Robinia pseudoacacia-dominated vegetation types of Southern Europe: Species composition, history, distribution and management

Dieback and Replacement of Riparian Trees May Impact Stream Ecosystem Functioning

Alders are nitrogen (N)-fixing riparian trees that promote leaf litter decomposition in streams through their high-nutrient leaf litter inputs. While alders are widespread across Europe, their populations are at risk due to infection by the oomycete Phytophthora ×alni, which causes alder dieback. Moreover, alder death opens a space for the establishment of an aggressive N-fixing invasive species, the black locust (Robinia pseudoacacia). Shifts from riparian vegetation containing healthy to infected alder and, eventually, alder loss and replacement with black locust may alter the key process of leaf litter decomposition and associated microbial decomposer assemblages. We examined this question in a microcosm experiment comparing three types of leaf litter mixtures: one representing an original riparian forest composed of healthy alder (Alnus lusitanica), ash (Fraxinus angustifolia), and poplar (Populus nigra); one with the same species composition where alder had been infected by P. ×alni; and one where alder had been replaced with black locust. The experiment lasted six weeks, and every two weeks, microbially driven decomposition, fungal biomass, reproduction, and assemblage structure were measured. Decomposition was highest in mixtures with infected alder and lowest in mixtures with black locust, reflecting differences in leaf nutrient concentrations. Mixtures with alder showed distinct fungal assemblages and higher sporulation rates than mixtures with black locust. Our results indicate that alder loss and its replacement with black locust may alter key stream ecosystem processes and assemblages, with important changes already occurring during alder infection. This highlights the importance of maintaining heathy riparian forests to preserve proper stream ecosystem functioning.

Assessment of Parectopa robiniella Clemens (Lepidoptera: Gracillariidae) Effect on Biochemical Parameters of Robinia pseudoacacia Under Conditions of an Industrial City in Steppe Ukraine

Antioxidant enzymatic activity and soluble protein content in Robinia pseudoacacia L. (black locust), invasive tree in Europe, plants were determined under feeding conditions of the caterpillars of Parectopa robiniella Clemens, 1863, invasive miner in Europe, in trees of three (I, II, III) age groups (5–10, 15–25, and 40 years). Biochemical analysis data showed significant differences between reference and experimental leaf samples in different urban ecosystems. There was no association between changes in catalase and peroxidase activity and protein content under the influence of leaf blotch miners depending on the tree age. Significant variability of proteins under P. robiniella influence was noted; the highest of its values were recorded in the leaves of ІІІ-aged trees. In most plantings (and especially in trees of age group III), an increase (1.2 to 2.7 times) in GPx activity or the absence of its changes was registered both in the ecologically favorable zone and in the locations affected by emissions from road transport and industrial enterprises. Plants of age groups I and II in the emission areas of metallurgical, pipe-rolling, and chemical industries experienced a significant decrease in GPx activity (by 20.2–44.6%) in the leaves damaged by the phytophage. In most of the plantings studied, catalase showed an increase/stability of its activity in all age groups of trees under condition of pest attack. The highest increase in САТ activity (2.1 times) was recorded in young R. pseudoacacia plants in an ecologically favorable area of the city.

Risks, benefits, and knowledge gaps of non-native tree species in Europe

Changing ecosystem conditions and diverse socio-economical events have contributed to an ingrained presence of non-native tree species (NNTs) in the natural and cultural European landscapes. Recent research endeavors have focused on different aspects of NNTs such as legislation, benefits, and risks for forestry, emphasizing that large knowledge gaps remain. As an attempt to fulfill part of these gaps, within the PEN-CAFoRR COST Action (CA19128) network, we established an open-access questionnaire that allows both academic experts and practitioners to provide information regarding NNTs from 20 European countries. Then, we integrated the data originating from the questionnaire, related to the country-based assessment of both peer-reviewed and grey literature, with information from available datasets (EUFORGEN and EU-Forest), which gave the main structure to the study and led to a mixed approach review. Finally, our study provided important insights into the current state of knowledge regarding NNTs. In particular, we highlighted NNTs that have shown to be less commonly addressed in research, raising caution about those characterized by an invasive behavior and used for specific purposes (e.g., wood production, soil recultivation, afforestation, and reforestation). NNTs were especially explored in the context of resilient and adaptive forest management. Moreover, we emphasized the assisted and natural northward migration of NNTs as another underscored pressing issue, which needs to be addressed by joint efforts, especially in the context of the hybridization potential. This study represents an additional effort toward the knowledge enhancement of the NNTs situation in Europe, aiming for a continuously active common source deriving from interprofessional collaboration.

Latitudinal trends in the structure, similarity and beta diversity of plant communities invaded by Alternanthera philoxeroides in heterogeneous habitats

Variations in latitudinal gradients could lead to changes in the performance and ecological effects of invasive plants and thus may affect the species composition, distribution and interspecific substitution of native plant communities. However, variations in structure, similarity and beta (β) diversity within invaded communities across latitudinal gradients in heterogeneous habitats remain unclear. In this study, we conducted a two-year field survey along 21°N to 37°N in China, to examine the differential effects of the amphibious invasive plant Alternanthera philoxeroides on native plant communities in terrestrial and aquatic habitats. We compared the differences in the invasion importance value (IV), species distribution, community similarity (Jaccard index and Sorenson index) and β diversity (Bray-Curtis index and β_sim index) between terrestrial and aquatic communities invaded by A. philoxeroides, as well as analyzed their latitudinal trends. We found that the IV of A. philoxeroides and β diversity in aquatic habitats were all significantly higher than that of terrestrial, while the terrestrial habitat had a higher community similarity values. The aquatic A. philoxeroides IV increased with increasing latitude, while the terrestrial IV had no significant latitudinal trend. With increasing latitude, the component proportion of cold- and drought-tolerant species in the terrestrial communities increased, and the dominant accompanying species in the aquatic communities gradually changed from hygrophytes and floating plants to emerged and submerged plants. In addition, the aquatic communities had lower community similarity values and higher β diversity in higher latitudinal regions, while terrestrial communities had the opposite parameters in these regions. Our study indicates that the bioresistance capacities of the native communities to invasive A. philoxeroides in heterogeneous habitats are different; A. philoxeroides invasion leads to higher community homogenization in terrestrial habitats than in aquatic habitats, and terrestrial communities experience more severe homogenization in higher latitudinal regions. These findings are crucial for predicting the dynamics of invasive plant communities under rapid global change.

Do non-native and dominant native species carry a similar risk of invasiveness? A case study for plants in Turkey

Most risk analysis studies in invasion biology have focused on the invasiveness of non-native species, even though some native species also can pose a high risk to the environment and human well-being. This is especially true under current global change, which may cause dominant native species to expand their range of distribution and have substantial effects on the ecosystem. In this study, the risk of invasiveness of five non-native and five native plant species in Turkey was evaluated using a standard risk screening protocol. All ten species selected for screening are known to be invasive in several parts of the world, i.e. non-native Ailanthus altissima, Cuscuta campestris, Phytolacca americana, Robinia pseudoacacia and Sicyos angulatus, and native Cirsium arvense, Hedera helix, Onopordum acanthium, Phragmites australis and Sorghum halepense. The Australian Weed Risk Assessment decision-support tool adapted to Turkey’s geographical and climatic conditions was used for screening the study species based on their biological traits, ecology and management approaches. All species were classified as high-risk, with R. pseudoacacia among non-natives and P. australis among natives achieving the highest scores followed by S. halepense, C. campestris, C. arvense, O. acanthium, P. americana, S. angulatus, A. altissima and H. helix. Based on their risk scores, all non-native species were classified as invasive and all native species as ‘expanding’ for Turkey. An ordination based on the risk scores showed similarities between invasive and expanding species. The outcomes of this study indicate that species can have several risk-related traits resulting in high risk scores irrespective of their origin. Such species can modify their environment and interact with other species with severe consequences for biodiversity. It is argued that dominant species with highly negative environmental and socioeconomic impacts in their habitats should be included in priority lists for management measures irrespective of their origin (i.e. native or non-native). More studies are needed to evaluate the magnitude and prevalence of the present findings for other regions worldwide.

Impact of invasive species Parectopa robiniella (Gracillariidae) on fluorescence parameters of Robinia pseudoacacia in the conditions of the steppe zone of Ukraine

Robinia pseudoacacia L. is one of the most common and environmentally adaptable introduced tree species which has become an important element of artificial afforestation and landscaping in Ukraine over the past 150 years. Throughout the history of its introduction on the territory of Ukraine, this species was considered resistant because of the absence of dangerous phytophages. At the beginning of the XXI century, the phytosanitary situation changed as the result of the penetration and rapid spread of a number of North American invasive phytophages. The appearance and distribution of the miner Parectopa robiniella (Clemens, 1863) (Lepidoptera, Gracillariidae) feeding on R. pseudoacacia was recognized as the largest invasion in Ukraine. This paper considers the issues of studying the effect of P. robiniella caterpillars feeding on R. pseudoacacia in various forest-growing conditions in the steppe zone of Ukraine. The process of photosynthesis, as the most important physiological parameter, was chosen as indicator of condition. The study was conducted using biosensor technology which made it possible to measure the effect of caterpillar feeding on critical parameters of chlorophyll fluorescence (the Kautsky curve). The research has shown that the initial value of fluorescence induction was within the range of 196–284 RFU, and the maximum value of the background fluorescence parameter was recorded in undamaged leaves and under shading conditions. Both the effect of phytophages and the shading factor caused a significant decrease in the values of fluorescence induction of the “plateau” both in the conditions of an artificially washed sandbar, on the watershed area of a watershed-gully landscape, as well as on natural sandy-loam soil. The maximum values of photosynthetic fluorescence induction under the simultaneous influence of the studied factors had rather high variability. In contrast to the fluorescence induction parameter, the “plateau” of the highest maximum fluorescence induction was reached in the absence of pest damage under conditions of total shading. As revealed by dispersion and regression analyses, the maximum fluorescence index was most dependent on the amount of solar radiation and on the degree of the leaf surface damage by phytophages. Significantly higher values of the steady-state fluorescence induction parameter were determined in the absence of insect damage in both shading and lighting conditions. A statistically significant combined influence of abiotic and biotic factors on the “plateau” fluorescence induction parameter was determined in comparison with the mono-influence of individual factors. A highly significant dependence of the maximum efficiency indicator of primary photosynthesis processes on individual factors of exogenous influence was established, while the combined effect of these factors did not affect this parameter. The obtained data allow one to apply in practice the methods of analyzing chlorophyll fluorescence induction to establish the physiological state of tree flora in forest and garden farms.

Characterization of plant growth-promoting bacteria isolated from the rhizosphere of Robinia pseudoacacia growing in metal-contaminated mine tailings in eastern Morocco

BACKGROUND

Mining activity in the Touissit district of Eastern Morocco has led to an unprecedented accumulation of heavy metals, mainly lead and zinc, in the tailing ponds of the open-air mines. This poses a real danger to both the environment and local population.

OBJECTIVES

The goal of this work was to characterize the Plant Growth Promoting Rhizobacteria (PGPR) isolated from the rhizosphere soil of R. pseudoacacia plants grown wild in the abandoned Pb- and Zn-contaminated tailing ponds in the mining district of Touissit, in Eastern Morocco.

MAIN RESULTS

One hundred bacterial strains were isolated from the rhizosphere of black locust (Robinia pseudoacacia L.) plants growing naturally in the Touissit mine tailings. Quantitative determination of indole-acetic and siderophores production, inorganic phosphate solubilization, hydrolysis of 1-aminocyclopropane-1-carboxylic acid (ACC deaminase activity), and ability to act as a biocontrol agent allowed selection of the 3 strains, 7MBT, 17MBT and 84MBT with improved PGP properties. The three strains grew well in the presence of high concentration of Pb-acetate and ZnCl_2; and the addition of Pb or Zn to the culture medium differently affected the PGP properties analyzed.

NOVELTY STATEMENT

Inoculation of black locust grown with the 3 selected strains, in the presence 1000 μg ml^-1 of Pb-acetate, produced varying effects on the plant dry weight. The strain 84MBT alone or in combination with strains 7MBT and 17MBT increased significantly the dry weight of the plants by 91, 62, and 85% respectively. The 16S rRNA gene sequence analysis of each strain showed that the strains 7MBT 17MBT and 84MBT had 99.34, 100, and had 99.72% similarity with Priestia endophytica (formerly B. endophyticus), B. pumilus NBRC 12092^T, and B. halotolerans NBRC 15718^T, respectively.

Assessing Black Locust Biomass Accumulation in Restoration Plantations

Forests (either natural or planted) play a key role in climate change mitigation due to their huge carbon-storing potential. In the 1980s, the Hellenic Public Power Corporation (HPPC) started the rehabilitation of lignite post-mining areas in Northwest Greece by planting mainly black locust (Robinia pseudoacacia L.). Today, these plantations occupy about 2570 ha, but the accumulation of Above Ground Biomass (AGB) and deadwood has not been assessed to date. Therefore, we aimed at estimating these biomass pools by calibrating an allometric model for AGB, performing an inventory for both pools and predicting the spatial distribution of AGB. 214 sample plots of 100 m2 each were set up through systematic sampling in a grid dimension of 500 × 500 m and tree dbh and height were recorded. AGB was estimated using an exponential allometric model and performing inventory measurements and was on average 57.6 t ha−1. Kriging analysis reliably estimated mean AGB, but produced errors in the prediction of high and low biomass values, related to the high fragmentation and heterogeneity of the studied area. Mean estimated AGB was low compared with European biomass yield tables for black locust. Similarly, standing deadwood was low (6–10%) and decay degrees were mostly 1 and 2, indicating recent deadwood formation. The overall low biomass accumulation in the studied black locust restoration plantations may be partially attributed to their young age (5–30 years old), but is comparable to that reported in black locust restoration plantation in extremely degraded sites. Thus, black locust successfully adapted to the studied depositions of former mines and its accumulated biomass has the potential to improve the carbon footprint of the region. However, the invasiveness of the species should be considered for future management planning of these restoration plantations.

Quantifying the effects of Robinia pseudoacacia afforestation on plant community structure from a functional perspective: New prospects for management practices on the hilly and gullied Loess Plateau, China

Robinia pseudoacacia is regarded as a valuable but problematic plant due to its positive and negative environmental effects. A comprehensive and mechanistic understanding of the effects of R. pseudoacacia afforestation on ecosystems and striking a balance between ecosystem safety and functioning and R. pseudoacacia naturalization are crucially important. To achieve these goals, studying the community functional structure of R. pseudoacacia plantations is an essential prerequisite that remains understudied. Through quantifying and comparing the functional structure of R. pseudoacacia plantations and naturally restored communities relating to soil erosion control and plant ecology strategies along a 10-40-year chronosequence on the hilly and gullied Loess Plateau, China, we assessed the effects of R. pseudoacacia afforestation on plant community structure from a functional perspective. We found significant differences among restoration strategies in all the functional composition indices but only functional divergence (FDiv) indices, suggesting that the afforestation practice had a great impact on functional composition but not on functional diversity. Specifically, the plantations had relatively high community-weighted means (CWMs) of specific leaf area (SLA), plant height (PH), seed production, seed mass, root mean diameter, clonality and resprouting capacity and high FDivs of the leaf-height-seed scheme and persistence traits, partially suggesting that the exotic tree could naturalize and coexist with native plants in the study area. Moreover, the relatively high CWMs of woodiness, PH and SLA and high FDiv of erosion-control-related traits found in the plantations indicate that the plantations might have superiority in soil erosion control. R. pseudoacacia also had a homogenization effect on understory functional composition and divergence. Furthermore, we proposed a trait-based effect-and-response framework to find the balance, thus achieving sustainable coexistence of the exotic species with ecosystems. This study may provide new prospects for management practices of R. pseudoacacia plantations and a robust scaffold to maintain safe, resilient and functioning ecosystems.

Black locust (Robinia pseudoacacia L.) range contraction and expansion in Europe under changing climate

Robinia pseudoacacia is one of the most frequent non-native species in Europe. It is a fast-growing tree of high economic and cultural importance. On the other hand, it is an invasive species, causing changes in soil chemistry and light regime, and consequently altering the plant communities. Previously published models developed for the potential distribution of R. pseudoacacia concerned 2070, and were based mainly on data from Western and Central Europe; here we extended these findings and included additional data from Eastern Europe. To fill the gap in current knowledge of R. pseudoacacia distribution and improve the reliability of forecasts, we aimed to (i) determine the extent to which the outcome of range modeling will be affected by complementing R. pseudoacacia occurrence data with sites from Central, Southeastern, and Eastern Europe, (ii) identify and quantify the changes in the availability of climate niches for 2050 and 2070, and discuss their impacts on forest management and nature conservation. We showed that the majority of the range changes expected in 2070 will occur as early as 2050. In comparison to previous studies, we demonstrated a greater eastward shift of potential niches of this species and a greater decline of potential niches in Southern Europe. Consequently, future climatic conditions will likely favor the occurrence of R. pseudoacacia in Central and Northeastern Europe where this species is still absent or relatively rare. There, controlling the spread of R. pseudoacacia will require monitoring sources of invasion in the landscape and reducing the occurrence of this species. The expected effects of climate change will likely be observed 20 years earlier than previously forecasted. Hence we highlighted the urgent need for acceleration of policies aimed at climate change mitigation in Europe. Also, our results showed the need for using more complete distribution data to analyze potential niche models.

Long-term river management legacies strongly alter riparian forest attributes and constrain restoration strategies along a large, multi-use river

Many terrestrial ecosystems have undergone profound transformation under the pressure of multiple human stressors. This may have oriented altered ecosystems toward transient or new states. Understanding how these cumulative impacts influence ecosystem functions, services and ecological trajectories is therefore essential to defining effective restoration strategies. This is particularly the case in riverine ecosystems, where the profound alteration of natural disturbance regimes can make the effectiveness of restoration operations questionable. Using the case study of legacy dike fields, i.e., area delimited by longitudinal and lateral dikes, along the regulated Rhône River, we studied the impacts of long-term channelization and flow regulation on environmental conditions and riparian forests attributes along a 200 km climatic gradient. We characterized the imprint of human stressors on these forests by comparing the dike field stands to more natural stands in both young and mature vegetation stages. Across four reaches of the river between Lyon and the Mediterranean Sea, we found that channelization consistently promoted high rate of overbank sedimentation and rapid disconnection of dike field surfaces from the channel. The rapid terrestrialisation of dike field surfaces, i.e., the process by which former aquatic areas transition to a terrestrial ecosystem as a result of dewatering or sedimentation, fostered a pulse of riparian forest regeneration in these resource-rich environments that differs from more natural sites in structure and composition. Within the dike fields, older pre-dam stands are dominated by post-pioneer and exotic species, and post-dam stands support large, aging pioneer trees with a largely exotic understory regeneration layer. These patterns were associated with differences in the relative surface elevation among dike fields, whereas species shifts generally followed the river's longitudinal climate gradient. To enhance the functionality of these human-made ecosystems, restoration strategies should target the reconnection of dike fields to the river by dismantling part of the dikes to promote lateral erosion, forest initiation and community succession, as well as increasing minimum flows in channels to improve connection with groundwater. However, since a river-wide return to a pre-disturbance state is very unlikely, a pragmatic approach should be favoured, focusing on local actions that can improve abiotic and biotic function, and ultimately enhancing ecosystem services such biodiversity, habitat, and recreation opportunities.

Global guidelines for the sustainable use of non-native trees to prevent tree invasions and mitigate their negative impacts

Sustainably managed non-native trees deliver economic and societal benefits with limited risk of spread to adjoining areas. However, some plantations have launched invasions that cause substantial damage to biodiversity and ecosystem services, while others pose substantial threats of causing such impacts. The challenge is to maximise the benefits of non-native trees, while minimising negative impacts and preserving future benefits and options.

A workshop was held in 2019 to develop global guidelines for the sustainable use of non-native trees, using the Council of Europe – Bern Convention Code of Conduct on Invasive Alien Trees as a starting point.

The global guidelines consist of eight recommendations: 1) Use native trees, or non-invasive non-native trees, in preference to invasive non-native trees; 2) Be aware of and comply with international, national, and regional regulations concerning non-native trees; 3) Be aware of the risk of invasion and consider global change trends; 4) Design and adopt tailored practices for plantation site selection and silvicultural management; 5) Promote and implement early detection and rapid response programmes; 6) Design and adopt tailored practices for invasive non-native tree control, habitat restoration, and for dealing with highly modified ecosystems; 7) Engage with stakeholders on the risks posed by invasive non-native trees, the impacts caused, and the options for management; and 8) Develop and support global networks, collaborative research, and information sharing on native and non-native trees.

The global guidelines are a first step towards building global consensus on the precautions that should be taken when introducing and planting non-native trees. They are voluntary and are intended to complement statutory requirements under international and national legislation. The application of the global guidelines and the achievement of their goals will help to conserve forest biodiversity, ensure sustainable forestry, and contribute to the achievement of several Sustainable Development Goals of the United Nations linked with forest biodiversity.

Biomass Yield of 37 Different SRC Poplar Varieties Grown on a Typical Site in North Eastern Germany

A total of 37 different poplar varieties were grown in a randomized mini-rotation short rotation coppice (SRC) (harvest every three years) on a light sandy soil under continental climatic conditions in the south of the Federal State of Brandenburg, Germany. Along with well-known poplar varieties, newly bred ones that have not yet been approved for commercial use were selected for this study. Survival rates were determined after the first growing season in 2013 as well as at the first and second harvests in 2015 and 2018. Furthermore, the number of shoots, plant height, diameter at breast height, dry matter content and biomass yield of the varieties were recorded. After the second rotation period, only seven poplar varieties yielded more than 11 tadm ha−1 y−1 and can be recommended for commercial use. However, many varieties only reached about 8 tadm ha−1 y−1, and six varieties even had less than 4 tadm ha−1 y−1, among them newly bred varieties. Given the changing climate conditions, the cultivation of these varieties in SRC is not recommended. Our data also show that the biomass yield of several varieties decreased from the first to the second harvests. Since the survival rates were high and no damage by pest species was observed, the site-specific yield capacities of the individual clones are assumed to be the cause for this.

Range shifts of native and invasive trees exacerbate the impact of climate change on epiphyte distribution: The case of lung lichen and black locust in Italy

While changing climatic conditions may directly impact species distribution ranges, indirect effects related to altered biotic interactions may exacerbate range shifts. This situation fully applies to epiphytic lichens that are sensitive to climatic factors and strongly depend on substrate occurrence and features for their dispersal and establishment. In this work, we modelled the climatic suitability across Italy under current and future climate of the forest species Lobaria pulmonaria, the lung lichen. Comparatively, we modelled the suitability of its main tree species in Italy, as well as that of the alien tree Robinia pseudoacacia, black locust, whose spread may cause the decline of many forest lichen species. Our results support the view that climate change may cause range shifts of epiphytes by altering the spatial pattern of their climatic suitability (direct effect) and simultaneously causing range shifts of their host-tree species (indirect effect). This phenomenon seems to be emphasized by the invasion of alien trees, as in the case of black locust, that may replace native host tree species. Results indicate that a reduction of the habitat suitability of the lung lichen across Italy should be expected in the face of climate change and that this is coupled with a loss of suitable substrate. This situation seems to be determined by two main processes that act simultaneously: 1) a partial reduction of the spatial overlap between the climatic niche of the lung lichen and that of its host tree species, and 2) the invasion of native woods by black locust. The case of lung lichen and black locust in Italy highlights that epiphytes are prone to both direct and indirect effects of climate change. The invasion of alien trees may have consequences that are still poorly evaluated for epiphytes.

Prohibited, but still present: local and traditional knowledge about the practice and impact of forest grazing by domestic livestock in Hungary

BACKGROUND

Forests have been grazed for millennia. Around the world, forest grazing by livestock became a controversial management practice, gradually restricted in many countries over the past 250 years. This was also the case in most Central and Eastern European countries, including Hungary, where forest grazing was a legally prohibited activity between 1961 and 2017. Until the 2010s, ecologists and nature conservationists considered it merely as a historical form of forest use. As a result, there is little contemporary scientific information available about the impact of forest grazing on vegetation and the traditional ecological knowledge associated with it. Our aim was to explore and summarize this type of knowledge held by herders in Hungary.

METHODS

We interviewed 58 knowledgeable herders and participated in forest grazing activities in 43 study locations across the country. The results were analysed qualitatively.

RESULTS

We revealed a living ecological knowledge tradition and practice of forest grazing in native and non-native forest stands. The impact of livestock grazing on native and non-native forests is not considerably different, in the view of the herders. For both forest types, the greatest impact of grazing was the suppression of the shrub layer, while grazing also increased the dominance and palatability ("tameness") of the grasses. Livestock could cause significant damage to seedlings during forest grazing, but if done with care, grazing could also be an integral part of forestry management.

CONCLUSIONS

Sustainability of current forest grazing practices depends on the depth of local and traditional knowledge applied and herders' stewardship. We stress the importance of collaborating with holders of local and traditional knowledge in order to gain a better understanding of the effects of livestock grazing on vegetation in temperate forests.

Preserving air pollution forest archives accessible through dendrochemistry

Plants are continuously exposed to human air pollution, absorbing pollutants in their tissues. Trees can store pollutants in wood, in the annual growth rings, retaining traces of pollutants in the environment. Information on past pollution events are archived by trees, which dendrochemistry, a dendrochronological science combined with chemistry, is able to access. Many authors have suggested that trees could complement the conventional environmental monitoring: a forest archive of pollution events. However, the implications of trees occurrence in polluted areas on planning and management have not yet been discussed. In this article, we investigate whether forest archives exist and whether they should be integrated into the network of existing monitoring stations. We use a case study, the Veneto region of Italy, one of the most polluted areas in Europe, to examine the occurrence of trees around 28 industrial plants retrieved from a European pollution register. We propose planning actions to develop the latent potential of these forest archives for environmental monitoring, which society may benefit. We follow three steps: (a) assessing the cover and composition of tree canopies around the industrial plants, (b) inventorying the existing artificial air monitoring stations in order to discover whether pollutants around the industrial plants are already monitored, (c) assessing land use patterns in order to identify which are the receptors of air pollution and enhance the forest archive in the future. These spatial analyses are conducted in a 1-km radius buffer with the industrial plant as the centre. Results show that forest archives are available, with cover and composition suitable for dendrochemistry studies. Artificial monitoring stations are too far from industrial plants or have been installed recently, unable to provide historical data. Trees are an alternative source of pollution data. Receptors of air pollution include a diversity of urban, rural and agricultural lands, where forest archives can be managed and conserved through a variety of actions. Environmental protection agencies should value these trees, preserving them and accessing the records held in this forest archive. Similar inventories must be promoted in other industrialised regions of the world even at larger scales. Studies like this one should also be incorporated into landscape or urban planning processes.