Brown bear digging decreases tree growth: Implication for ecological role of top predators in anthropogenic landscapes

Large carnivores have recently increased in number and recolonized in human-dominated landscapes; however, their ecological roles in these landscapes have not been well studied. In the Shiretoko World Heritage (SWH) site, brown bears have recolonized a previously abandoned mosaic landscape of natural forests and conifer plantations after land abandonment. We previously reported that the bears had recently begun to dig for cicada nymphs in association with the creation of larch plantations. As a result, this digging activity decreased soil nutrients. To deepen the understanding of the novel ecological role of brown bears within human-modified landscapes, we examined the impacts of brown bear digging on the growth of larch trees. We found that brown bear digging decreased fine root biomass of larch, soil water, and nitrogen availability. Brown bear digging negatively affected needle nitrogen content, but not carbon isotope ratios, a water stress index of trees. Tree ring data suggest that digging negatively affected the radial growth of larches. The results imply that digging decreases tree growth due to limited soil nitrogen uptake. Our findings indicate that the ecological roles of large carnivores may differ between natural and anthropogenic landscapes.

Tree parameter extraction in Fokienia hodginsii plantation based on airborne LiDAR data

Accurate and efficient extraction of tree parameters from plantations lay foundation for estimating individual wood volume and stand stocking. In this study, we proposed a method of extracting high-precision tree parameters based on airborne LiDAR data. The main process included data pre-processing, ground filtering, individual tree segmentation, and parameter extraction. We collected high-density airborne point cloud data from the large-diameter timber of Fokienia hodginsii plantation in Guanzhuang State Forestry Farm, Shaxian County, Fujian Province, and pre-processed the point cloud data by denoising, resampling and normalization. The vegetation point clouds and ground point clouds were separated by the Cloth Simulation Filter (CSF). The former data were interpolated using the Delaunay triangulation mesh method to generate a digital surface model (DSM), while the latter data were interpolated using the Inverse Distance Weighted to generate a digital elevation model (DEM). After that, we obtained the canopy height model (CHM) through the difference operation between the two, and analyzed the CHM with varying resolutions by the watershed algorithm on the accuracy of individual tree segmentation and parameter extraction. We used the point cloud distance clustering algorithm to segment the normalized vegetation point cloud into individual trees, and analyzed the effects of different distance thresholds on the accuracy of indivi-dual tree segmentation and parameter extraction. The results showed that the watershed algorithm for extracting tree height of 0.3 m resolution CHM had highest comprehensive evaluation index of 91.1% for individual tree segmentation and superior accuracy with R2 of 0.967 and RMSE of 0.890 m. When the spacing threshold of the point cloud segmentation algorithm was the average crown diameter, the highest comprehensive evaluation index of 91.3% for individual tree segmentation, the extraction accuracy of the crown diameter was superior, with R2 of 0.937 and RMSE of 0.418 m. Tree height, crown diameter, tree density, and spatial distribution of trees were estimated. There were 5994 F. hodginsii, with an average tree height of 16.63 m and crown diameter of 3.98 m. Trees with height of 15-20 m were the most numerous (a total of 2661), followed by those between 10-15 m. This method of forest parameter extraction was useful for monitoring and managing plantations.

Changes in Competitors, Stress Tolerators, and Ruderals (CSR) Ecological Strategies after the Introduction of Shrubs and Trees in Disturbed Semiarid Steppe Grasslands in Hulunbuir, Inner Mongolia

To reveal the changes in the life history characteristics of grassland plants due to vegetation restoration, plant species and communities were analyzed for their competitor, stress tolerator, and ruderal (CSR) ecological strategies after the introduction of woody plants in the damaged steppe grassland and were compared with those in reference sites in Hulunbuir, Inner Mongolia. As a result, it was found that the introduction of the woody plants (Corethrodeneron fruticosum, Caragana microphylla, Populus canadensis, and Pinus sylvestris var. mongolica) into the damaged land greatly increased the plant species diversity and CSR eco-functional diversity as the succession progressed. The plant strategies of the temperate typical steppe (TTS) and woodland steppe (WS) in this Asian steppe are CSR and S/SR, respectively, which means that the plants are adapted to disturbances or stress. As the restoration time elapsed in the damaged lands exhibiting (R/CR) (Corispermum hyssopifolium), the ecological strategies were predicted to change in two ways: (1) →R/CSR (Cynanchum thesioides, Astragalus laxmannii, etc.) → CSR in places (TSS) (Galium verum var. asiaticum, Saussurea japonica, etc.) where only shrubs were introduced, and (2) → S/SR (Allium mongolicum, Ulmus pumila, etc.) → S/SR in sites (WS) (Ulmus pumila, Thalictrum squarrosum, etc.) where trees and shrubs were planted simultaneously. The results mean that the driving force that causes succession in the restoration of temperate grasslands is determined by the life-form (trees/shrubs) of the introduced woody plants. This means that for the restoration of these grasslands to be successful, it is necessary to introduce woody tree species at an early stage.

Diversity and Network Relationship Construction of Soil Fungal Communities in Lactarius hatsudake Tanaka Orchard during Harvest

Lactarius hatsudake Tanaka is a mycorrhizal edible mushroom with rich economic and nutritional value. Although it is artificially planted, its yield is unstable. Soil fungi, including L. hatsudake, coexist with many other microorganisms and plants. Therefore, complex microbial communities have an influence on the fruiting body formation of L. hatsudake. L. hatsudake and its interactions with the rest of the fungal community over time are not completely understood. In this study, we performed high-throughput sequencing of microorganisms in the basal soil of the fruiting body (JT), mycorrhizosphere soil (JG), and non-mushroom-producing soil (CK) in a 6-year-old L. hatsudake plantation at harvest. The results showed that the soil of the L. hatsudake plantation was rich in fungal communities and a total of 10 phyla, 19 classes, 53 orders, 90 families, 139 genera, and 149 species of fungi were detected. At the phylum level, the major groups were Basidiomycota and Ascomycota. At the genus level, the dominant groups were Lactarius, Trichoderma, Suillus, and Penicillium. Among them, L. hatsudake had an absolute dominant position in the soil fungal community of the plantation, and was the only group of Lactarius in the plantation soil. Penicillium cryptum and Penicillium adametzii were unique to the JT soil sample. Chaetopsphaeria, Myxocephala, Devriesia, and Psathyrella were positively correlated with L. hatsudake. In the constructed fungal network, the total number of nodes were ranked in descending order as JG (441) > CK (405) > JT (399), while the total number of edges were ranked in descending order as CK (1360) > JG (647) > JT (586). Analysis of the fungal assembly process revealed that groups CK and JG have determinative processes that dominated community building, while the JT group exhibited a dominant random process with a 0.60 probability. The results indicated that L. hatsudake was successfully colonized in the plantation soil. During harvest, the CK group exhibited the largest network size and the most complex fungal interactions, while the fungal community structure in the mushroom cultivation zone (JT and JG) was stable and less susceptible to external environmental interference. L. hatsudake affects the fungal community in the soil surrounding its fruiting body.

Relationship between net primary productivity and stand age in typical plantation forests in China

Plantation forests play an important role in carbon sink in terrestrial ecosystems. Based on tree rings of five main plantation tree species (Robinia pseudoacacia, Quercus variabilis, Cunninghamia lanceolata, Pinus sylvestris var. mongolica, and Pinus tabuliformis) at 25 sites in China, we calculated the average annual NPP of standard trees in each study area by the biomass equations and extended to the stand scale. The relationships between NPP and stand age were fitted by the InTEC and Law models. The results showed that NPP of R. pseu-doacacia, C. lanceolata, and P. tabuliformis plantations increased to a peak and then leveling off with stand age, while that of Q. variabilis and P. sylvestris var. mongolica plantations reached a peak and then showed a decreasing trend. The inflection points of NPP-stand age curve for different planatations was 11 years for P. sylvestris var. mongolica, 14 years for C. lanceolata, 16 years for P. tabuliformis, and 20 years for R. pseudoacacia. The NPP peak was 6.65, 7.58, 4.70 and 2.59 t·hm-2·a-1, respectively. Both the InTEC and Law NPP-stand age models had high fitting accuracy at a large scale, with the lowest R2 of 0.95 and RMSE of 0.55 t·hm-2·a-1 for the P. sylvestris var. mongolica InTEC model and the highest R2 of 0.99 and RMSE of 0.26 t·hm-2·a-1 for the C. lanceolata InTEC model. The construction of NPP-stand age relationship for major plantations in China provided mechanistic support for the estimation of carbon sinks in plantations at long time scales and provided a reference for the diversification of afforestation tree species selection.

Changes in Soil Properties, Microbial Quantity and Enzyme Activities in Four Castanopsis hystrix Forest Types in Subtropical China

It is well established that forest type can have a profound impact on soil physicochemical properties but the associated changes in soil microbial communities and the mechanisms by which soil quality is improved by various plantations are not fully understood. In this study, soil physicochemical properties and microbial and enzyme activities were investigated in four forest types-Castanopsis hystrix pure forests (CHPF), C. hystrix-Pinus elliottii mixed forests (CHPEF), C. hystrix-Michelia macclurei mixed forests (CHMMF), and C. hystrix-Mytilaria laosensis mixed forests (CHMLF) in the subtropical region of China. The purpose of this study was to assess the effects of afforestation types on characteristics of soil-its physical, chemical, and biological properties. The results showed that the contents of soil total organic carbon (TOC), soil total nitrogen (TN), microbial biomass carbon (MBC), and microbial biomass nitrogen (MBN) were significantly improved in both CHMMF and CHMLF mixed forest stands when compared to the CHPF pure stand. Soil enzyme activities were enhanced in the mixed forests. In particular, high phosphatase activity was observed in CHMLF stands, leading to the transformation of soil phosphorus to available phosphorus in this forest type. Our study demonstrated that the broad-leaved mixed forests, but not coniferous mixed forests, could significantly improve soil quality in the study region. Our research provides a scientific insight into the promotion of vegetation restoration and plantation forest management in plantation regions of subtropical areas.

[Effects of Long-term Sod Cultivation on Chinese Hickory Plantation Soil Fungal Community and Enzyme Activities]

A long-term field experiment was conducted at a Chinese hickory (Carya cathayensis) plantation from 2011 to 2021, with the purpose of researching the effects of long-term sod cultivation on hickory plantation soil fungal communities and enzyme activities and providing experience for ecological management in other plantations. Sod cultivation included oilseed rape (Brassica chinensis, BR), Chinese milk vetch (Astragalus sinicus, AS), and oilseed rape+Chinese milk vetch (BA), and clear tillage (CT) served as a contrast. The soil fertility, fungal community composition and diversity, and soil enzyme activities were determined. The results showed that:① long-term sod cultivation significantly increased soil nutrient contents and availability, and pH increased variably from different sod cultivation treatments (P<0.05). ②The soil fungal community composition was changed by long-term sod cultivation. The relative abundance of Ascomycota, which utilized the readily decomposed organic matter, was increased, whereas the relative abundance of Basidiomycota, which degraded stubborn organic matter, decreased. Long-term sod cultivation shifted the soil dominant genera, as BR and BA increased the relative abundance of somemycorrhizal fungi that could form mutually beneficial structures with dominant plant genera after sod cultivation,whereas AS increased the relative abundance of saprophytic fungi that could decompose the remains of dead plants and animals. The soil fertility factors including pH, available nitrogen, microbial biomass nitrogen, and water-soluble organic carbon were revealed to have a significant influence on the soil fungal composition (P<0.05). ③ Moreover, long-term sod cultivation stimulated the activities of soil enzymes involved in the carbon and nitrogen cycle. Apart from BA, sod cultivation treatments decreased the activities of alkaline phosphatase, which was involved in the soil P turnover. The correlation analysis demonstrated that the correlations between activities of enzymes decomposing carbon and nitrogen and soil fertility were significant (P<0.05 or P<0.01). The activities of phosphatase were positively correlated with soil microbial biomass carbon and nitrogen. Long-term sod cultivation could improve soil nutrient content and availability, optimized soil fungal community structure, and promoted soil nutrient turnover enzyme activities.

Integrated pest management of Hypsipyla robusta shoot-tip borer (Lepidoptera: Pyralidae) in Chukrasia tabularis (Sapindales: Meliaceae)

Chukrasia tabularis A. Juss produces a valuable timber but plantations are susceptible to attack by the shoot-tip borer Hypsipyla robusta Moore. An integrated pest management (IPM) approach is desirable to limit the extent of damage. Therefore, this study was undertaken to evaluate the deployment of IPM measures in plantations in Vietnam. Data on tree damage and the biology of H. robusta were gathered in 4 provinces over one year and used to build an investigation schedule. Two preliminary IPM trials were then established in which Bacillus thuringiensis and Metarhizium anisopliae were applied to the foliage when the damage incidence (P%) was in the range 5-10%; and insecticides (Carbaryl, Carbosulfan) were applied when the P% exceeded 10%. In addition, larvae and pupae were removed manually over time. In the first trial, the combination of manual and biological control methods reduced the damage index (DI) of trees from 4 tolerant families by 82% compared to the untreated control plots. In the second trial using standard planting stock, application of insecticides was required to reduce the DI by 83%. Six extended IPM trials were undertaken using the same IPM protocols and these reduced the DI to the same extent as in the preliminary trials. Over an 18-month period, the deployment of IPM increased height growth by 19-22% and diameter growth by 38-41% compared to the controls. These findings highlight the value of planting improved seed and the benefit of adopting an IPM approach to manage the shoot-tip borer.

Radial Variability of Selected Physical and Mechanical Parameters of Juvenile Paulownia Wood from Extensive Cultivation in Central Europe-Case Study

The research on Paulownia cultivation and wood properties is up to date in many countries. However, there are no data on the properties of this wood defined on a microscale, on microtome samples. The main aim of this study was to find the best valorization path for the wood of Paulownia Shang Tong Hybrid F1 from an extensively cultivated plantation established in April 2017 in Poland by determining the tensile strength, the wood density, the strength-to-density ratio, and the modulus of elasticity on a cross-section of the trunk. The wood was collected from extensive plantation, where production is based on the natural resources of the habitat and ambient weather conditions, which is the opposite to the intensive cultivation model, which is the recommended model of Paulownia cultivation. The results of this study show that the mean density of the analyzed samples was approximately 210 kg/m³ when the mean value of the modulus of elasticity (MOE) was approximately 2400 MPa. The mean result for the tensile strength ratio to density was 11.25 km. In the case of anatomical structure, the increasing trend with age was noticed both in fiber and vessel characteristics. The study results provide unique data worldwide about Paulownia wood's properties based on a cross-section of the trunk, from plantations cultivated in conditions which are not recommended by seedlings producers. The obtained data indicate that the Paulownia wood (examined) from the cultivation in this study has a technical quality similar to that of model-intensive agricultural plantations.

Factors influencing contraceptive use among women of reproductive age in plantation farming communities in South-South Nigeria

The use of contraceptives by women of reproductive age remains one of the cost-effective ways of reducing maternal, infant, and child mortality and achieving a decline in the high fertility rate in the country. This was a descriptive cross-sectional study aimed to assess the association between the location of residence, occupation, and education level and the current use of contraceptives among women of reproductive age resident in plantation farming communities in South-south Nigeria. The test of associations between the dependent and independent variables and covariates was conducted using the Likelihood ratio Chi-square as appropriate. Multiple logistic regressions using the best-fit option of covariate selection were done with the use of contraceptives as the dependent variable. Of the 609 participants recruited, 189 (31.03%) were currently using a contraceptive. Women with secondary education were less likely to use contraceptives compared to the none educated [AOR=0.07; CL: 0.013-0.39]. Location and age were also significant predictors of the use of contraceptives by women in plantation farming communities in Nigeria. Deliberate and purposeful targeting of women and girls of reproductive age in plantation farming communities should be prioritized in the universal access to contraceptive use.

Variations in Soil Blue Carbon Sequestration between Natural Mangrove Metapopulations and a Mixed Mangrove Plantation: A Case Study from the World's Largest Contiguous Mangrove Forest

Sundarban is the world's largest mangrove wetland. This study, conducted in 2016, to compare blue carbon sequestration with different natural metapopulations and a four-year-old Avicennia marina (30% area)-Rhizophora mucronata (70% area)-mixed mangrove plantation under anthropoganic stress. The aims of the study is to find out the variations in soil ecological function indicators (pH, electrical conductivity, bulk density, soil texture, available nitrogn, phosphorus and soil organic carbon) and key ecological service indicator (soil blue carbon pool) between sites. Simpson's Index of dominance, diversity and Shannon-Weiner Index revealed that all the sites are under ecological stress, with the Suaeda maritima-dominated mudflat having the least biodiversity. It is also revealed that pH and electrical conductivity were highest in Suaeda maritima and Phoenix padulosa-dominated metapopulations, whereas organic carbon was the highest under the mangrove plantation and Avicennia marina-dominated site. Available nitrogen was recorded highest in the community with the Sonneretia sp.-Avicennia marina association. The mixed mangrove plantation had the highest blue carbon pool. The species diversity was not found to be related with the distance from the nearby conserved mangrove forest, contrary to the island biogeography theory. This study concludes with a recommendation of mixed mangrove plantations to restore the degraded saline mudflats along the human settlements across the globe.

Development of an Ergonomic, Portable, Climber-Propelled Date Tree Climbing Device

In the most of main date fruit producer regions, including Iran, date palm crown access operation is still performed traditionally. The date plantation workers need to climb date trees. This may cause an unsafe condition, which increases the risk of fall from height. It is also associated with ergonomic and health problems. The present study aimed to develop a date tree climber device (DTCD) covering all aspects of safety, ergonomics and efficiency. A primary model of the DTCD was structured and modified based on a review of existing devices, a field investigation and an unstructured interview with 20 farmworkers. Participants rated their comfort, perceived pain and discomfort as well as exertion levels when using the DTCD compared to a traditional device (Parband). In total, eight key elements were suggested for the desired device. More than 60% of the participants reported that the DTCD was comfortable/very comfortable compared to Parband. Additionally, DTCD could significantly reduce the pain and discomfort of the back (p < .001), knees (p = .001) and Ankles/feet (p = .01). However, no significant difference was found between devices when the physical exertion was compared through Borg's RPE scale and heart rate analysis. The results of regression analysis showed that the DTCD users perceived lower exertion as the body weight increased (β = -0.18, p = .013). The signs of musculoskeletal disorders, pain and discomfort were strongly reduced among DTCD users and safety aspects improved, generally by reducing discomfort and physical exertion.

Incorporating stand density effects and regression techniques for stem taper modeling of a Larix principis-rupprechtii plantation

Stem form is the shape of the trunk, differs among tree species and mainly affected by stand density factor. Accurate taper equations are crucial for estimating the stem diameter, form and tree volume, which is conducive to timber utilization and sustainable forest management and planning. Larch (Larix principis-rupprechtii Mayr.) is a valuable afforestation species under large-scale development in North China, but no study on the effect of density on its stem taper has been reported yet. The dataset included 396 analytical trees from 132 standard plots of larch plantation in Saihanba, Hebei Province. Based on 12 different forms of models, we explored the optimal basic equation for plantations and the effects of the stand density, basal area, canopy density and different forms of stand density on the prediction accuracy of the variable-exponent models. The variable-exponent taper equation that includes Sd (stand density) was constructed by using nonlinear regression, a nonlinear mixed effect model and the nonlinear quantile regression method. The results indicate that the Kozak's 2004 variable-exponent taper equation was the best basic model for describing changes in the stem form of larch plantations, and the density factor in the form of S d improved the prediction accuracy of the basic model. Among the three regression methods, the quantile regression method had the highest fitting accuracy, followed by the nonlinear mixed effect model. When the quantile was 0.5, the nonlinear quantile regression model exhibited the best performance which provides a scientific basis for the rational management of larch plantations.

Impact of Plantation Induced Forest Degradation on the Outbreak of Emerging Infectious Diseases-Wayanad District, Kerala, India

The world has been facing a pandemic owing to COVID-19. We have also seen the geographic expansion and outbreaks of other emerging infectious diseases (EID) in recent years. This paper investigates the direct and indirect effects of land use land cover change (LULCC) on EID outbreaks in the context of Wayanad District of Kerala, India. Wayanad is in the vulnerable tropical forested region, and it is named as one of the four environmental change hotspots. The focus of this project is mainly three EIDs prevalent in this region: Kyasanur forest disease (KFD), Dengue and Leptospirosis. Our results, based on topographical map, remote sensing and extensive field work, show that the natural forest in Wayanad was replaced with agriculture and forest plantation during 1950-2018. This paper further suggests that encroachment of forest by forest plantation causes the human-animal conflict resulting in the outbreak of KFD cases. Our analysis reveals that a high number of Dengue cases is found in the forested regions of the district and over the adjacent human-made agriculture plantation areas. High and medium number of Leptospirosis cases contain a high portion of land area devoted to paddy cultivation and agricultural plantation. In summary, the results clearly show the linkage between the outbreak of above mentioned EIDs and LULCC in the context of Wayanad district, Kerala. We also discuss in detail the causal pathway involving human-environmental dynamics through which plantation leads to the outbreak of KFD. Replacing forests with plantations poses an alarming threat of disease outbreak in the community.

[Effects of tree species identity and diversity on young tree growth in a south subtropical plantation]

To select the tree species assembly model for improving the productivity in south subtropical plantations, we carried out an experiment following a random block design with eight native tree species across a richness gradient of 1, 2, 4, and 6 species. The effects of tree species diversity and species mixing with different functional identities on the young tree growth were investigated in the 5th year of the experiment. The results showed that tree growth was not positively correlated with tree species richness. The growth of fast-growing tree species (Pinus massoniana and Mytilaria laosensis) in the monoculture was 2.5-4.5 times of the valuable broadleaved tree species (Castanopsis hystrix and Erythrophleum fordii) monoculture. Tree growth was significantly increased by 51.5%-132.8% in the conifer and broadleaved tree species mixing plantations and in the fast-growing and nitrogen fixation tree species mixing plantations, when two tree species or four tree species were mixed. There was no significant difference in tree growth among different tree species mixed types, when six tree species were mixed. The contents of soil nitrogen, phosphorus and organic matter were the main factors affecting tree growth. The results indicated that young tree growth could be improved through the selecting conifer and broadleaved tree species mixing, fast-growing and nitrogen fixation tree species mixing in south subtropical plantations.

[From the earth to the plate, a unique experience]

A group of toddlers in a childcare facility participated in the creation of an educational garden. For some time, they all lived at the rhythm of the different stages of the project, i.e. planting, waiting, harvesting and finally the preparation and consumption of the fruit and vegetables produced. Although this experimentation raised questions among the professionals, it also provided all the participants with some wonderful moments of sharing.

Entomopathogenic Potential of Simplicillium lanosoniveum Native Strain in Suppressing Invasive Whitefly, Aleurodicusrugioperculatus Martin (Hemiptera: Aleyrodidae), Infesting Coconut

In 2016, infestation of an exotic polyphagous pest, the rugose spiraling whitefly (RSW), Aleurodicus rugioperculatus Martin (Hemiptera: Aleyrodidae), was documented on coconut for the first time in India. Instantaneously, RSW has garnered wide attention owing to its damage severity and rapid spread across the coconut-growing regions of the country. Hence, an attempt was made to devise a sustainable integrated pest management (IPM) module using biological control agents as a mainstay component. The present study documented the identification and characterization of a potential entomopathogenic fungal isolate for the management of RSW. An entomopathogenic fungus isolated from nymphal cadavers of RSW was identified as Simplicillium lanosoniveum based on morphological and phylogenetic analyses. A gradient of five conidial concentrations (1 × 10⁴, 1 × 10⁵, 1 × 10⁶, 1 × 10⁷ and 1 × 10⁸ conidia/mL) of the S.lanosoniveum were tested against eggs, first instars, second to third instars and pupae of RSW. Results revealed that S.lanosoniveum is highly virulent to all developmental stages of RSW by causing mortality rates of 95.20%, 87.33%, 85.38% and 72.85%, in eggs, initial, middle and later instar nymphs of RSW, respectively, at the highest tested concentration (1 × 10⁸ conidia/mL) at seven days after exposure. The LC₅₀ and LT₅₀ values of S.lanosoniveum were 4.72 × 10⁴, 4.94 × 10⁴, 5.11 × 10⁵, 5.92 × 10⁵ conidia/mL and 4.27, 4.86, 4.56, 5.89 days against eggs, initial, middle and later instar nymphs of RSW, respectively. Further, preliminary field trials with S.lanosoniveum strain at 1 × 10⁸ conidia/mL exhibited a significant reduction in the egg and nymphal population by 57.8% and 56.3%, respectively. This report thus demonstrated that the newly isolated S.lanosoniveum is an effective pathogen at suppressing all the developmental stages of RSW. This is the first record of S.lanosoniveum infecting RSW, and it has a great potential to be developed as a mycoinsecticide.

Mycobiota Associated with the Vascular Wilt of Poplar

In 2017, a 560-ha area of hybrid poplar plantation in northern Poland showed symptoms of tree decline. The leaves appeared smaller, yellow-brown, and were shed prematurely. Twigs and smaller branches died without distinct cankers. Trunks decayed from the base. The phloem and xylem showed brown necrosis. Ten percent of the trees died 1–2 months after the first appearance of the symptoms. None of these symptoms were typical for known poplar diseases. The trees’ mycobiota were analysed using Illumina sequencing. A total of 69 467 and 70 218 operational taxonomic units (OTUs) were obtained from the soil and wood. Blastocladiomycota and Chytridiomycota occurred only in the soil, with very low frequencies (0.005% and 0.008%). Two taxa of Glomeromycota, with frequencies of 0.001%, occurred in the wood. In the soil and wood, the frequencies of Zygomycota were 3.631% and 0.006%, the frequencies of Ascomycota were 45.299% and 68.697%, and the frequencies of Basidiomycota were 4.119% and 2.076%. At least 400 taxa of fungi were present. The identifiable Zygomycota, Ascomycota, and Basidiomycota were represented by at least 18, 263 and 81 taxa, respectively. Many fungi were common to the soil and wood, but 160 taxa occurred only in soil and 73 occurred only in wood. The root pathogens included species of Oomycota. The vascular and parenchymal pathogens included species of Ascomycota and of Basidiomycota. The initial endophytic character of the fungi is emphasized. Soil, and possibly planting material, may be the sources of the pathogen inoculum, and climate warming is likely to be a predisposing factor. A water deficit may increase the trees’ susceptibility. The epidemiology of poplar vascular wilt reminds grapevine trunk diseases (GTD), including esca, black foot disease and Petri disease.

Effects of natural and artificial restoration on plant community characteristics of alpine cutting blank in Western Sichuan, China

To investigate the plant community characteristics of alpine cutting blanks under different restoration approaches, we conducted a field survey on cutting blanks experienced either natural restoration (40 years) or artificial restoration (30, 40 and 50 years) in western Sichuan, with natural forests as the reference. Our results showed that after 40 years natural succession, cutting blank was replaced by the secondary shrub of Spiraea alpina, while artificial restoration plantation was dominated by Picea likiangensis var. rubescens. The similarity indices between these communities and natural forests were low (0.19) and medium (0.28-0.49), respectively. Cutting blank through natural and artificial restoration had lower species diversity in the shrub layer but higher diversity in the herb layer than that of natural forests. With the increases of recovery time, total cross-sectional area at breast height, wood volume, index of species diameter class distribution, diversity indices, and similarity indices between plantations and natural forests gradually increased, while stand density gradually decreased. Compared with natural forests, plantations were facing with problems including high stand density, unreasonable structure, pure stands of cohorts and poor regeneration.

Structure and function of soil bacterial communities in the monoculture and mixed plantation of Pinus massoniana and Castanopsis hystrix in southern subtropical China

Establishing monoculture of native broadleaved tree species and mixed coniferous broadleaved plantations is the tendency for forest management in subtropical China. The variations of structure and function of soil bacterial community in monoculture and mixed tree plantations are still not clear. We examined soil bacterial community structure and function under different soil layers (0-20, 20-40 and 40-60 cm) in three planted forests, including broadleaved Castanopsis hystrix, coniferous Pinus massoniana and their mixed plantation, in south subtropical China, using 16S rRNA gene high-throughput sequencing and PICRUSt prediction. The results showed that soil bacterial community structure of mixed plantation and P. massoniana plantation were similar but being significant different from that in C. hystrix plantation. The diversity, biological pathways metabolic function, and nitrogen cycling function of soil bacterial community in C. hystrix plantation were lower than those in P. massoniana plantation and mixed plantation. Soil total nitrogen, nitrate nitrogen and C/N were the main factors driving the variations of soil bacterial community structure and function among different forest types. Our results suggested that the mixed plantation of C. hystrix and P. massoniana is better than C. hystrix plantation in this area in terms of soil bacterial community structure and function.

[Effects of plantation on aggregate distribution and stability of lateritic red soil in south subtropical China]

We examined the stability of soil aggregates in five typical plantations, i.e., Eucalyptus urophylla × E. grandis plantation, Cunninghamia lanceolata plantation, Pinus massoniana plantation, Mytilaria laosensis plantation and Castanopsis hystrix plantation, in the south subtropical China by the Elliott wet sieving and Le Bissonnais (LB) methods. The results showed that the content of water stability aggregate (WR_&gt;0.25) was more than 62.2% after wet sieving. The mean weight diameter (MWD) and geometric mean diameter (GMD) of aggregates were 1.58-3.71 mm and 0.57-2.02 mm, respectively, which were the largest in C. lanceolata plantation and the smallest in E. urophylla × E. grandis plantation. Percentage of aggregate destruction (PAD) of five kinds of plantations ranged from 4.6% to 31.5%. The transfer matrix method was used to evaluate the soil aggregates, with the aggregate stability index (ASI) following the order of C. lanceolata plantation &gt; C. hystrix plantation &gt; M. laosensis plantation &gt; P. massoniana plantation &gt; E. urophylla × E. grandis plantation. Under the three treatments of LB method, the FW treatment was the most destructive to the stability of soil aggregates, indicating that dissipation played a major role in the disintegration of soil aggregates. The WS treatment had the least damage to the aggregates. The effect of slow wetting (SW) treatment was between the fast wetting (FW) and wet stirring (WS). Both the MWD and GMD values followed the order of WS&gt;SW&gt;FW, which gradually decreased with the increases of soil depth. The GMD value of aggregates under FW treatment by LB method of five plantations was significantly positively correlated with ASI, MWD and GMD of wet sieving method, indicating that the traditional wet sieving method had a good correlation with FW treatment and was feasible to determine the stability of soil aggregates in the subtropical red soil. Based on the aggregate stability indices of MWD, GMD, PAD and ASI, C. lanceolata plantation was more conducive to the improvement of soil aggregation level, with more stable soil structure than the other four plantations.

A Decade of Close-to-Nature Transformation Alters Species Composition and Increases Plant Community Diversity in Two Coniferous Plantations

Close-to-nature transformation silviculture is a promising approach to meet the criteria for sustainable forestry. To explore the effects of close-to-nature transformation on community structure and plant diversity in Pinus massoniana and Cunninghamia lanceolatas pure plantations, four stands were selected, including close-to-nature transformed stand of P. massoniana (PCN) and its unimproved pure stand (PCK), and close-to-nature transformed stand of C. lanceolata (CCN) and its unimproved pure stand (CCK). Plant diversity and community structure in the four stands were investigated before and after a decade of close-to-nature transformation. After the close-to-nature transformation, the plant diversity and community structure were significantly altered. Compared with control stands, the transformation increased the species richness and diversity of the tree layer and the whole community, while did not significantly affected the shrub and herb diversity. The species richness in the tree layer in the P. massoniana and C. lanceolata plantations was 2.1 and 2.8 times that of their corresponding control. Species composition and important value of each species were altered in the tree, shrub and herb layers. The close-to-natural transformation lowered the community dominance and the important value of P. massoniana and C. lanceolate. The advantage position of single species in the community was weakened by the forest transformation. The plant community became diversified and uniformly distributed. The enhanced community species diversity was derived from the increase in the tree diversity. These results indicated that close-to-nature transformation increased the forest plant diversity and optimized the community structure. The close-to-nature transformation plays a positive role in coniferous plantation ecosystem structure.

Empire and indigestion: Materializing tannins in the Indian tea industry

In the mid-1800s, plantation-produced tea from India came onto the British market. Tea retailers blended this more malty and black tea with the lighter Chinese-grown tea to which consumers had become accustomed. By the turn of the 20th century, blending helped Empire-grown tea supplant Chinese-grown tea on the market. Scholars of tea have shown how British tea companies working in South Asia stoked racialized fears that Chinese tea arrived in Britain in an adulterated state, laden with impurities that included dyes, perfumes and even human sweat. This article describes how concerns about protecting tea leaves from outside adulteration gave way to concerns about the potential digestive threat that lay inside tea leaves themselves. Medical journals linked the increased consumption of Indian teas to a population-wide 'epidemic' of indigestion. The most cited culprits in this epidemic were tannins, chemical compounds that were also thought to give black tea its characteristic bitterness and color. The normalization of black tea consumption among the British public was not just a work of marketing or branding but a work of resolving uncertainty about what tannins were at a material, biophysical level. As this uncertainty was resolved scientifically, tea was materialized not as a singular, unified product but as an active chemical assemblage.

Plantation Mapping in Southeast Asia

Plantation mapping is important for understanding deforestation and climate change. While most existing plantation products are created manually, in this paper we study an ensemble learning based framework for automatically mapping plantations in southern Kalimantan on a yearly scale using remote sensing data. We study the effectiveness of several components in this framework, including class aggregation, data sampling, learning model selection and post-processing, by comparing with multiple baselines. In addition, we analyze the quality of our plantation mapping product by visual examination of high resolution images. We also compare our method to existing manually labeled plantation datasets and show that our method can achieve a better balance of precision (i.e., user's accuracy) and recall (i.e., producer's accuracy).

Novel species of Calonectria isolated from soil near Eucalyptus plantations in southern China

Calonectria species are soil-borne and widely distributed in tropical and subtropical regions around the world. The species in this genus include many important plant pathogens that cause serious diseases to economically important crops and forest trees. Previous research results indicated that the leaf blight and cutting rot caused by Calonectria species caused big losses to the Eucalyptus industry in southern China, and large number of Calonectria species identified in China have been collected from soil in Eucalyptus plantations. In this study, Calonectria samples were isolated from soils close to Eucalyptus plantations in Guangdong Province, southern China. These isolates were identified by DNA sequence analyses based on the calmodulin (cmdA), histone H3 (his3), translation elongation factor 1-alpha (tef1), and β-tubulin (tub2) gene regions, and combined with morphological characteristics. One novel species of Calonectria was identified and described, named Calonectria xianrensis, which resides in the Prolate Group. Results in this study suggest that more species of Calonectria may be distributed in soils in China.

[Effects of Chinese fir litter cover on its seedling emergence and early growth]

Litter accumulation can strongly affect seedling emergence and early growth through both physical and chemical mechanisms, and can further influence natural regeneration. Chinese fir (Cunninghamia lanceolata) is one of the most important afforestation tree species. Its natural regeneration is poor, possibly due to the thick leaf accumulation inhibiting seedling emergence and growth. We used natural and plastic litter to study the effects of Chinese fir litter on its own seedling emergence and early growth, as well as to assess whether the effect was physical or chemical. In this experiment, two litter types (natural and plastic litter) and four different litter amounts (control, 0 g·m^-2; low, 200 g·m^-2; medium, 400 g·m^-2; high, 800 g·m^-2) were used. The results showed that compared to the control (0 g·m^-2), low litter amount (200 g·m^-2) exerted a slight positive effect on seedling emergence, whereas high litter amount (800 g·m^-2) significantly reduced the seedling emergence and survival rate in the case of both natural and plastic litter. With increasing litter amount, root length of seedlings decreased and stem length increased. The highest and lowest root mass, leaf mass, and total mass of seedlings were observed for the low and high litter amount, respectively, in the case of both natural and plastic litter. The root:shoot ratio of seedlings decreased with the increasing litter amount for both natural and plastic litter. The photosynthesis:non-photosynthesis biomass ratio of the seedlings was higher under all litter cover treatments, compared to that in the control. Because the effect of the same amounts of the natural and plastic litter on seedling emergence and early growth did not differ, the litter layer's short-term influence was primarily physical. As the litter cover increased, the initial slight positive effects on seedling emergence and early growth could shift to inhibitory effects. Moreover, to penetrate the thick litter layer, Chinese fir seedlings allocated more resources toward stems and aboveground growth. This study provided evidence for litter amount being a key ecological factor that affects the seedling development and subsequent natural regeneration of Chinese fir.

Herbicides and herbivory interact to drive plant community and crop-tree establishment

Land management practices often directly alter vegetation structure and composition, but the degree to which ecological processes such as herbivory interact with management to influence biodiversity is less well understood. We hypothesized that large herbivores compound the effects of intensive forest management on early seral plant communities and plantation establishment (i.e., tree survival and growth), and the degree of such effects is dependent on the intensity of management practices. We established 225-m² wild-ungulate (deer and elk) exclosures, nested within a manipulated gradient of management intensity (no-herbicide control, light herbicide, moderate herbicide, and intensive herbicide treatments), replicated at the scale of whole harvest units (10-19 ha). Vegetation structure, composition, and crop-tree responses to herbivory varied across the gradient of herbicide application during the first two years of stand establishment, with herbivory effects most evident at light and moderate herbicide treatments. In the moderate herbicide treatment, which approximates management applied to >2.5 million hectares in the Pacific Northwest, United States, foraging by deer and elk resulted in simplified, low-cover plant communities more closely resembling the intensive herbicide treatment. Herbivory further suppressed the growth of competing vegetation in the light herbicide treatment, improving crop-tree survival, and providing early evidence of an ecosystem service. By changing community composition and vegetation structure, intensive forest management alters foraging selectivity and subsequent plant-herbivore interactions; initial shifts in early seral communities are likely to influence understory plant communities and tree growth in later stages of forest development.

[Early effects of forest harvesting gap on understory plant diversity of three different plantations in Baiyun Mountain, China.]

Pinus massoniana, Cunninghamia lanceolata, and Phyllostachys edulis are the main afforesting species in the low hilly areas and valley of the southern Yangtze River for commercial purpose. Ecological problems such as the monotonous community structure and low biodiversity are common in these plantations. To understand the effect of forest harvesting gap on the understory plant diversity in the three plantations, different size gaps with identical habitats were conducted with cano-pies as control in the three plantations in Baiyun Mountain. The life form spectrum of plants and plant diversity were compared among the different forest gaps. The results showed that species richness was the highest in C. lanceolata plantation (57 species), followed by P. edulis plantation (53 species) and P. massoniana plantation (41 species) in two years after harvesting. In the early period, plant species were more abundant in the gaps than that in the controls in C. lanceolata and P. edulis plantations, but there was no significant difference between the gaps and the control in P. masso-niana plantation. The percentage of phanerophyte plants were significantly higher in the forest gaps covered 500 m² area than that with other sizes. The percentage of the hemicryptophyte and therophyte plants were higher in the forest gaps covered 250 m² area. The percentage of geophyte plants were higher in the forest gaps with 50 m² area than the others. The resembling coefficients between the different size gaps were higher than that between the gaps and the control in the same plantation. The resembling coefficients between different size gaps in the same plantation were higher than that between different size gaps in different plantations. The resembling coefficients between the gaps and the control in different plantations were generally lower than the others. The species richness, Simpson ecological dominance index, and Shannon diversity index differed significantly for different size gaps. Except for Simpson ecological dominance index, the indices were significantly influenced by the plantation types. The effects of the interaction between plantation types and gap sizes on these indices were not statistically significant. Forest harvesting gaps altered life form spectrum of understory plants and increased plant diversity in the three plantations.

[Effects of natural vegetation restoration and afforestation on soil carbon and nitrogen storage in the Loess Plateau, China.]

Changes in land use can have important impacts on soil carbon and nitrogen storage. To explore the effects of different land use types on soil carbon and nitrogen storage, we examined the differences of soil carbon and nitrogen storage, ratio of carbon to nitrogen and root biomass in the 0-100 cm soil layer of the natural grassland and Pinus tabuliformis plantation since the implementation of the project (15 years) of "Returning Farmland to Forest (Grassland)" in the Ziwuling forest region of the Loess Plateau, China. The results showed that soil organic carbon of both natural grassland and P. tabuliformis plantation showed surface polymerization effect. Soil organic carbon storage in the 0-20 cm soil layer of natural grassland was significantly lower than that of P. tabuliformis plantation, while the other soil layers showed no significant difference. The total soil carbon storage of P. tabuliformis plantation in the 0-100 cm soil layer was 117.94 Mg·hm^-2, which was 28.4% higher than that of natural grassland. There was no significant difference in total nitrogen storage in different soil layers of the two vegetation types. The soil total nitrogen storage of natural grassland was 7.69 Mg·hm^-2 in the 0-100 cm soil layer, which was 17.7% higher than P. tabuliformis plantation. There was significant difference in ammonium storage among different soil layers in natural grassland and P. tabuliformis plantation. The ammonium storage in natural grassland was significantly higher than that in P. tabuliformis plantation, exhibited first increase and then decrease trend with the increases of soil depth. Only in the 0-20 cm soil layer, nitrate storage in natural grassland was significantly higher than the P. tabuliformis plantation. The ratio of carbon to nitrogen of natural grassland and P. tabuliformis plantation showed no significant difference in 0-20 cm soil layer. With the increases of soil layers, the ratio of carbon to nitrogen in P. tabuliformis plantation were higher than in the natural grassland, and the difference increased gradually. In addition, soil carbon and nitrogen storage showed significantly positive correlation with root biomass in natural grassland and P. tabuliformis plantation. Therefore, natural grassland was conductive to the accumulation of soil nitrogen storage, and P. tabuliformis plantation was beneficial to increase soil carbon storage. Root was an important factor affecting the distribution of soil carbon and nitrogen storage.

Seasonality of nitrogen partitioning (non-structural vs structural) in the leaves and woody tissues of tropical eucalypts experiencing a marked dry season

Numerous studies have shown that internal nitrogen (N) translocation in temperate tree species is governed by photoperiod duration and temperature. For tropical tree species, the seasonality of rainfall is known to affect growth and foliage production, suggesting that efficient internal N recycling also occurs throughout the year. We tested this hypothesis by comparing the N budgets and N partitioning (non-structural vs structural N) in the different organs of 7-year-old Eucalyptus urophylla (S.T. Blake) × E. grandis (W. Hill ex Maiden) trees from a plantation in coastal Congo on poor sandy soil. The trees were sampled at the end of the dry season and late in the rainy season. Lower N concentrations and N investment in the non-structural fraction were observed in leaves during the dry season, which indicates resorption of non-structural N from senescing leaves. Stem wood, which contributes to about 60% of the total biomass of the trees, accumulated high amounts of non-structural N at the end of the dry season, most of which was remobilized during the following rainy season. These results support the hypothesis of efficient internal N recycling, which may be an important determinant for the growth potential of eucalypts on N-poor soils. Harvesting trees late in the rainy season when stem wood is depleted in non-structural N should be recommended to limit the export of nutrients off-site and to improve the sustainability of tropical eucalypt plantations.

[Carbon storage and sequestration potential of five typical plantation ecosystems in Gansu Province, China]

Based on the data of the field investigation and laboratory and the database of the 8^th national forestry inventory, ecosystem carbon density, storage amount, and sequestration potential of tree layer were estimated for five typical plantation ecosystems (Robinia pseudoacacia, Populus spp., Pinus tabuliformis Pinus armandii, which were grouped as one kind of ecosystems, Larix principis-rupprechtii, and Picea asperata) in Gansu Province. The results showed that the average carbon density and total carbon storage of the five typical plantation ecosystems were 139.65 t·hm^-2 and 85.78 Tg, respectively. Ecosystem carbon density varied among ecosystems. It followed the sequence of premature (250.70 t·hm^-2) > mature (175.97 t·hm^-2) > middle-aged (156.92 t·hm^-2) > young (117.56 t·hm^-2) forest. Meanwhile, carbon storage in these plantations ranked in the order of young (45.47 Tg) > middle-aged (19.54 Tg) > mature (11.84 Tg) > pre-mature (8.93 Tg) forest. Specifically, young and middle-aged plantations contributed the most and accounted for 75.9% of the total carbon storage. The realistic carbon sequestration potential (CP_r) by tree layer of the five typical plantation ecosystems in Gansu Province was estimated as 7.27 Tg. The two largest contributors toCP_r were R. pseudoacacia (2.49 Tg) and Populus spp. (2.10 Tg). Young plantations (3.78 Tg) showed the largest CP_r, followed by middle-aged plantations (2.04 Tg), and the value of premature plantations (0.45 Tg) was the smallest. The maximum carbon sequestration potential (CP_max) might be up to 27.55 Tg, the CP_max with different plantations ranked in the order of R. pseudoacacia (9.42 Tg)> L. principis-rupprechtii (6.22 Tg) ≈ P. asperata (6.36 Tg) > Populus spp. (3.18 Tg) >P. tabuliformis P. armandii (2.37 Tg). The CP_max of young and middle-aged plantations was estimated as 18.48 and 6.89 Tg, respectively, which accounted for 92% of the total maximum carbon sequestration potential.

A hyperspectral image can predict tropical tree growth rates in single-species stands

Remote sensing is increasingly needed to meet the critical demand for estimates of forest structure and composition at landscape to continental scales. Hyperspectral images can detect tree canopy properties, including species identity, leaf chemistry and disease. Tree growth rates are related to these measurable canopy properties but whether growth can be directly predicted from hyperspectral data remains unknown. We used a single hyperspectral image and light detection and ranging-derived elevation to predict growth rates for 20 tropical tree species planted in experimental plots. We asked whether a consistent relationship between spectral data and growth rates exists across all species and which spectral regions, associated with different canopy chemical and structural properties, are important for predicting growth rates. We found that a linear combination of narrowband indices and elevation is correlated with standardized growth rates across all 20 tree species (R²  = 53.70%). Although wavelengths from the entire visible-to-shortwave infrared spectrum were involved in our analysis, results point to relatively greater importance of visible and near-infrared regions for relating canopy reflectance to tree growth data. Overall, we demonstrate the potential for hyperspectral data to quantify tree demography over a much larger area than possible with field-based methods in forest inventory plots.

Rash in a foreign worker

Hookworm-related cutaneous larva migrans (HrCLM) is a zoonosis which is endemic in many sub-tropic and tropical countries including Malaysia. We report a case of a 40-year old plantation worker who presented with a pruritic rash on his abdomen. It is important for clinicians to diagnose and treat HrCLM promptly as this condition results in considerable morbidity when treatment is delayed.

Foraging ecology and occurrence of 7 sympatric babbler species (Timaliidae) in the lowland rainforest of Borneo and peninsular Malaysia

Understanding foraging strategies of birds is essential to understanding mechanisms of their community assembly. To provide such information on a key Southeast Asian rainforest family, the babblers (Timaliidae), we evaluated foraging behavior and abundance in 7 morphologically and behaviorally similar sympatric species (Cyanoderma erythropterum, C. rufifrons, Stachyris maculata, S. nigricollis, S. poliocephala, Macronus ptilosus, and Mixornis gularis) in 5 habitats defined by structural complexity: (1) continuous native rainforest, (2) logged native rainforest fragments, (3) mature industrial tree plantation, (4) young industrial plantation, and (5) oil palm plantation. Enough data were obtained to compare abundance in all 7 species and foraging behavior in 5. All species were common in forest fragments and mature industrial tree plantations and less so in continuous rainforest and young industrial plantations; only M. gularis occurred in oil palm. In terms of foraging, M. gularis was the greatest generalist; C. rufifrons foraged mainly on live leaves in the forest midstory; and S. maculata, C. erythropterum, and M. ptilosus foraged mainly on dead leaves suspended in understory vegetation at significantly different heights. The dead-leaf substrate depends on a rich supply of falling leaves and extensive understory structure, conditions most common in native forest and old industrial plantations, and less so in mature forest, young plantations, and oil palm. Because of the importance of foraging data to understanding and managing biodiversity, we encourage the development of foraging fields in eBird (ebird.org), so that birdwatchers may help collect these relatively rare data.

Variation in the number of nucleoli and incomplete homogenization of 18S ribosomal DNA sequences in leaf cells of the cultivated Oriental ginseng (Panax ginseng Meyer)

BACKGROUND

Wild ginseng, Panax ginseng Meyer, is an endangered species of medicinal plants. In the present study, we analyzed variations within the ribosomal DNA (rDNA) cluster to gain insight into the genetic diversity of the Oriental ginseng, P. ginseng, at artificial plant cultivation.

METHODS

The roots of wild P. ginseng plants were sampled from a nonprotected natural population of the Russian Far East. The slides were prepared from leaf tissues using the squash technique for cytogenetic analysis. The 18S rDNA sequences were cloned and sequenced. The distribution of nucleotide diversity, recombination events, and interspecific phylogenies for the total 18S rDNA sequence data set was also examined.

RESULTS

In mesophyll cells, mononucleolar nuclei were estimated to be dominant (75.7%), while the remaining nuclei contained two to four nucleoli. Among the analyzed 18S rDNA clones, 20% were identical to the 18S rDNA sequence of P. ginseng from Japan, and other clones differed in one to six substitutions. The nucleotide polymorphism was more expressed at the positions 440-640 bp, and distributed in variable regions, expansion segments, and conservative elements of core structure. The phylogenetic analysis confirmed conspecificity of ginseng plants cultivated in different regions, with two fixed mutations between P. ginseng and other species.

CONCLUSION

This study identified the evidences of the intragenomic nucleotide polymorphism in the 18S rDNA sequences of P. ginseng. These data suggest that, in cultivated plants, the observed genome instability may influence the synthesis of biologically active compounds, which are widely used in traditional medicine.

Slow recovery of tropical old-field rainforest regrowth and the value and limitations of active restoration

There is current debate about the potential for secondary regrowth to rescue tropical forests from an otherwise inevitable cascade of biodiversity loss due to land clearing and scant evidence to test how well active restoration may accelerate recovery. We used site chronosequences to compare developmental trajectories of vegetation between self-organized (i.e., spontaneous) forest regrowth and biodiversity plantings (established for ecological restoration, with many locally native tree species at high density) in the Australian wet tropics uplands. Across 28 regrowth sites aged 1-59 years, some structural attributes reached reference rainforest levels within 40 years, whereas wood volume and most tested components of native plant species richness (classified by species' origins, family, and ecological functions) reached less than 50% of reference rainforest values. Development of native tree and shrub richness was particularly slow among species that were wind dispersed or animal dispersed with large (>10 mm) seeds. Many species with animal-dispersed seeds were from near-basal evolutionary lineages that contribute to recognized World Heritage values of the study region. Faster recovery was recorded in 25 biodiversity plantings of 1-25 years in which wood volume developed more rapidly; native woody plant species richness reached values similar to reference rainforest and was better represented across all dispersal modes; and species from near-basal plant families were better (although incompletely) represented. Plantings and regrowth showed slow recovery in species richness of vines and epiphytes and in overall resemblance to forest in species composition. Our results can inform decision making about when and where to invest in active restoration and provide strong evidence that protecting old-growth forest is crucially important for sustaining tropical biodiversity.

Vulnerability of native savanna trees and exotic Khaya senegalensis to seasonal drought

Seasonally dry ecosystems present a challenge to plants to maintain water relations. While native vegetation in seasonally dry ecosystems have evolved specific adaptations to the long dry season, there are risks to introduced exotic species. African mahogany, Khaya senegalensis Desr. (A. Juss.), is an exotic plantation species that has been introduced widely in Asia and northern Australia, but it is unknown if it has the physiological or phenotypic plasticity to cope with the strongly seasonal patterns of water availability in the tropical savanna climate of northern Australia. We investigated the gas exchange and water relations traits and adjustments to seasonal drought in K. senegalensis and native eucalypts (Eucalyptus tetrodonta F. Muell. and Corymbia latifolia F. Muell.) in a savanna ecosystem in northern Australia. The native eucalypts did not exhibit any signs of drought stress after 3 months of no rainfall and probably had access to deeper soil moisture late into the dry season. Leaf water potential, stomatal conductance, transpiration and photosynthesis all remained high in the dry season but osmotic adjustment was not observed. Overstorey leaf area index (LAI) was 0.6 in the native eucalypt savanna and did not change between wet and dry seasons. In contrast, the K. senegalensis plantation in the wet season was characterized by a high water potential, high stomatal conductance and transpiration and a high LAI of 2.4. In the dry season, K. senegalensis experienced mild drought stress with a predawn water potential -0.6 MPa. Overstorey LAI was halved, and stomatal conductance and transpiration drastically reduced, while minimum leaf water potentials did not change (-2 MPa) and no osmotic adjustment occurred. Khaya senegalensis exhibited an isohydric behaviour and also had a lower hydraulic vulnerability to cavitation in leaves, with a P50 of -2.3 MPa. The native eucalypts had twice the maximum leaf hydraulic conductance but a much higher P50 of -1.5 MPa. Khaya senegalensis has evolved in a wet-dry tropical climate in West Africa (600-800 mm) and appears to be well suited to the seasonal savanna climate of northern Australia. The species exhibited a large phenotypic plasticity through leaf area adjustments and conservative isohydric behaviour in the 6 months dry season while operating well above its critical hydraulic threshold.

Acetylcholinesterase activity and neurodevelopment in boys and girls

BACKGROUND

Organophosphate exposures can affect children's neurodevelopment, possibly due to neurotoxicity induced by acetylcholinesterase (AChE) inhibition, and may affect boys more than girls. We tested the hypothesis that lower AChE activity is associated with lower neurobehavioral development among children living in Ecuadorian floricultural communities.

METHODS

In 2008, we examined 307 children (age: 4-9 years; 52% male) and quantified AChE activity and neurodevelopment in 5 domains: attention/executive functioning, language, memory/learning, visuospatial processing, and sensorimotor (NEPSY-II test). Associations were adjusted for demographic and socioeconomic characteristics and height-for-age, flower worker cohabitation, and hemoglobin concentration.

RESULTS

Mean ± standard deviation AChE activity was 3.14 ± 0.49 U/mL (similar for both genders). The range of scores among neurodevelopment subtests was 5.9 to 10.7 U (standard deviation: 2.6-4.9 U). Girls had a greater mean attention/executive functioning domain score than boys. In boys only, there were increased odds ratios of low (<9th percentile) neurodevelopment among those in the lowest tertile versus the highest tertile of AChE activity (odds ratios: total neurodevelopment: 5.14 [95% confidence interval (CI): 0.84 to 31.48]; attention/executive functioning domain: 4.55 [95% CI: 1.19 to 17.38], memory/learning domain: 6.03 [95% CI: 1.17 to 31.05]) after adjustment for socioeconomic and demographic factors, height-for-age, and hemoglobin. Within these domains, attention, inhibition and long-term memory subtests were most affected.

CONCLUSIONS

Low AChE activity was associated with deficits in neurodevelopment, particularly in attention, inhibition, and memory in boys but not in girls. These critical cognitive skills affect learning and academic performance. Added precautions regarding secondary occupational pesticide exposure would be prudent.

The function of the superficial root mat in the biogeochemical cycles of nutrients in congolese eucalyptus plantations

BACKGROUND AND AIMS

The importance of superficial root mats inside the forest floor for the nutrition of Amazonian rain forests has been extensively investigated. The present study was aimed at assessing the function of a root mat adherent to decomposing organic material observed in Eucalyptus plantations.

METHODS

The development of the root mat was studied through micromorphological observations of thin litter sections, and the influence of soil microtopography and soil water repellency on root mat biomass was assessed in situ on an area of 5 m2. In addition, input-output budgets of nutrients within the forest floor were established from measurements of litterfall, dissolved nutrients in gravitational solutions, and forest floor nutrient contents.

KEY FINDINGS

The amounts of nutrients released during litter decay in this ecosystem during the period of study were, on average, 46, 3, 4, 19 and 17 kg ha-1 year-1 for N, P, K, Ca and Mg, respectively. The simultaneous measurements of the chemical composition of throughfall solutions and leachates beneath the forest floor showed a very quick uptake of nutrients by the root mat during the decomposition processes. Indeed, the solutions did not become noticeably enriched in nutrients during their passage through the holorganic layer, despite large amounts of elements being released during litter decay. The root mat biomass decreased significantly during the dry season, and a preferential development in microdepressions at the soil surface was observed. A strong water repellency observed in these depressions might enhance the ability of the roots to take up water and nutrients during the dry periods.

CONCLUSIONS

The root mat was active throughout the year to catch the flux of nutrients from the biodegradation of the forest floor, preventing the transfer of dissolved nutrients toward deeper soil horizons. This mechanism is involved in the successful adaptation of this Eucalyptus hybrid in areas covered by 'climacic' savannas in Congo.

Nutrient dynamics throughout the rotation of Eucalyptus clonal stands in Congo

The dynamics of the main nutrient fluxes of the biological cycle were quantified in a clonal Eucalyptus plantation throughout the whole planted crop rotation: current annual requirements of nutrients, uptake from the soil, internal translocations within trees, return to soil (litterfall and crown leaching) and decomposition in the forest floor. As reported for other species, two growth periods were identified in these short-rotation plantations: (1) a juvenile phase up to canopy closure, during which the uptake of nutrients from the soil reserves supplied most of the current requirements; and (2) a second phase up to harvest, characterized by intense nutrient recycling processes. Internal translocation within trees supplied about 30 % of the annual requirements of N and P from 2 years of age onwards, and about 50 % of the K requirement. The mineralization of large amounts of organic matter returned to the soil with litterfall during stand development represented a key process providing nutrients to the stand at the end of the rotation. The importance of the recycling processes was clearly shown by the small amounts of nutrients permanently immobilized in the ligneous components of trees, compared with the total requirements accumulated over the stand rotation which were two to four times higher. Small pools of nutrients circulating quickly in the ecosystem made it possible to produce high amounts of biomass in poor soils. The sustainability of these plantations will require fertilizer inputs that match the changes in soil fertility over successive rotations, mainly linked to the dynamics of organic matter in this tropical soil.