The diversity of soil mesofauna declines after bamboo invasion in subtropical China

Bamboo invasion alters Collembola community composition varying with life-forms

BACKGROUND

Plant invasions are a global concern. In eastern China, bamboo is rapidly expanding, negatively influencing neighbouring forest communities. However, studies on how bamboo invasion affects belowground communities, especially for soil invertebrates, are still lacking. In the present study, we focused on a highly abundant and diverse fauna taxon - Collembola. Collembola communities have three typical life-forms (i.e., epedaphic, hemiedaphic, and euedaphic) inhabiting different soil layers and playing distinct roles in ecological processes. Specifically, we studied their abundance, diversity, and community composition at the three stages of bamboo invasion: uninvaded secondary broadleaf forest, moderately invaded mixed bamboo forest, and completely invaded bamboo (Phyllostachys edulis) forest.

RESULTS

Our results showed that bamboo invasion negatively influenced Collembola communities by decreasing their abundance and diversity. Moreover, Collembola life-forms differed in their responses to bamboo invasion, with surface-dwelling Collembola being more vulnerable to bamboo invasion than soil-living Collembola.

CONCLUSION

Our findings indicate differential response patterns to bamboo invasion within Collembola communities. The negative effects of bamboo invasion on soil surface-dwelling Collembola may further influence ecosystem functioning. © 2023 Society of Chemical Industry.

Effects of trunk injection with emamectin benzoate on arthropod diversity

BACKGROUND

Pine wood nematode is a major plant quarantine object in the world. Trunk injection is an effective method for controlling pests that cause disease. To evaluate the ecological safety of trunk injection with emamectin benzoates in forests of Pinus massoniana, the community diversity and community composition of soil arthropods and flying insects (Hymenoptera) were studied at different stages of trunk injection.

RESULTS

The dominant taxonomic groups of soil arthropods were Collembola (30.80%), Insecta (26.42%), and Arachnida (23.84%). The taxonomic groups of flying insects (Hymenoptera) were Ichneumonidae (48.94%), Formicidae (14.10%), and Braconidae (8.44%). Trunk injection with emamectin benzoate has no significant effect on the community diversity indices of total soil arthropods and flying insects (Hymenoptera). However, it has a significant effect on the community diversity indices of detritivores for soil arthropods. It changed the community composition of soil arthropods but did not impact the community composition of flying insects (Hymenoptera). Redundancy analysis of arthropod community structure and environmental variables showed that total potassium, residual of green leaf, and residual of litter leaf have a significant impact on the community structure of soil arthropods, and total phosphorus, total nitrogen, water content, organic matter, and total potassium have a significant impact on the community structure of flying insects (Hymenoptera).

CONCLUSION

Trunk injection with emamectin benzoate is safe for the ecological environment. This study provides a new insight into the field for the prevention and control of pine wood nematode disease, which is of great significance to forest management and pest control. © 2022 Society of Chemical Industry.

What Are the Effects of Moso Bamboo Expansion into Japanese Cedar on Arbuscular Mycorrhizal Fungi: Altering the Community Composition Rather than the Diversity

The unbridled expansion of moso bamboo (Phyllostachys edulis) occurs throughout the world and has a series of consequences. However, the effect of bamboo expansion on arbuscular mycorrhizal fungi (AMF) is still poorly understood. We assessed the changes in the AMF community during bamboo expansion into Japanese cedar (Cryptomeria japonica) forests by analyzing AMF in three forest types-Japanese cedar (JC), bamboo-cedar mixed (BC) and moso bamboo (MB)-using 454 pyrosequencing technology. We found that the AMF community composition differed significantly among forest types. The relative abundance of Glomerales decreased from 74.0% in JC to 61.8% in BC and 42.5% in MB, whereas the relative abundance of Rhizophagus increased from 24.9% in JC to 35.9% in BC and 56.7% in MB. Further analysis showed that soil characteristics explained only 19.2% of the AMF community variation among forest types. Hence, vegetation is presumably the main driver of the alteration of the AMF community. The α diversity of AMF was similar between JC and MB, although it was higher in BC. Overall, this research sheds more light on AMF community dynamics during moso bamboo expansion. Our results highlight that the consequences of bamboo expansion in monoculture forests differ from those in mixed forests.

Trypoxylus dichotomus Gut Bacteria Provides an Effective System for Bamboo Lignocellulose Degradation

Fast-growing bamboo may be a source of high-quality cellulose with the potential to contribute to energy sustainability, if an efficient and low-cost solution to bamboo cellulose decomposition can be developed. This study compared the gut microbiomes of rhinoceros beetle (Trypoxylus dichotomus) feeding on bamboo and wood fiber. The results revealed that diet has a distinctive effect on microbial composition in the midgut, including its most abundant microorganisms that in the fermentation and chemoheterotroph pathways. After identifying the 13 efficient bacterial isolates, we constructed a natural bacterial system based on the microbial relative abundance and an artificial bacterial system with equal proportions of each isolate to catabolize bamboo lignocellulose. The isolate Enterobacter sp. AZA_4_5 and the natural system showed higher degradation efficiency than other single strains or the artificial system. The results can thus serve as important reference for further research and development of a synthetic bacterial consortium to maximize lignocellulolytic ability. IMPORTANCE Bamboo produces a great yield of lignocellulosic biomass due to its high efficiency in carbon fixing. The gut microbiome of Trypoxylus dichotomus differed between bamboo and wood fiber diets. The lignocellulosic pathways were enriched in the gut bacteria of the bamboo diet. The highly efficient bacterial isolates were identified from midgut, whereas the natural bacterial system as well as one isolate showed the higher degradation efficiency of bamboo lignocellulose. The results indicate that the gut bacteria could provide an effective system to utilize the bamboo lignocellulosic biomass.

The impact of restoration methods for Solidago-invaded land on soil invertebrates

The belowground community structure of soil biota depends on plant composition and may be affected by invasive plant species. We hypothesized that the type of land restoration method applied affects the abundance and composition of soil invertebrates. Our field experiment centred on Solidago species control using different seed mixtures and methods of seed introduction (sowing mixtures: grasses, grasses with legumes, seeds from a seminatural meadow, and application of fresh hay) and different frequencies of mowing (one, two, or three times per year). Soil invertebrates were identified to the taxa, using light microscopes. Richness and diversity indices were calculated, and a redundancy analysis was conducted. Generally, mowing intensity negatively influenced soil organisms, although increased mowing frequency positively affected the abundance of some taxa (Symphyla, Hemiptera). Mowing twice per year decreased the abundance of soil invertebrates, but not their diversity. Soil invertebrate taxa had the greatest abundance in the plots sown with a seed mixture containing grasses with legumes. Among the restoration methods studied, mowing once a year and introducing grasses with legumes represented the least harmful strategy with regard to soil invertebrate abundance. Further studies are needed to investigate the dynamics of soil mesofauna exposed to long-term mowing and changes in vegetation characteristics.

Mixed Forest of Larix principis-rupprechtii and Betula platyphylla Modulating Soil Fauna Diversity and Improving Faunal Effect on Litter Decomposition

This research performed a comparison study to investigate how mixed forest affects the abundance, groups, and diversity of soil fauna and the effects of soil fauna on litter decomposition. We comparatively studied two forests, Larix principis-rupprechtii forest (LF) and mixed Larix principis-rupprechtii and Betula platyphylla forest (MF), which hold 30 years of stand age and are the representative forests in the mountainous area of northwestern Hebei, China. The field experiments were conducted from May to November 2020, with soil fauna and litter samples taken every one and a half months. A total of 540 soil samples (replicated samples, 3) were collected in each forest and the soil faunas were extracted from the samples by Tullgren methods in laboratory. Litter samples were incubated separately in the sampled forests using litterbags with two mesh sizes (0.01 and 4 mm) to observe the decomposition rate. In total, 2958 (inds.) soil faunas belonging to 4 phyla, 11 classes, and 20 orders, were found, with Acarina (1079/2958; 36.48%) and Collembola (1080/2958; 36.51%) being the dominant groups. The total abundance of soil fauna in the MF (1581 inds.) was higher than that in the LF (1377 inds.), and the significantly more abundant predatory functional group in the MF (p < 0.05) may indicate a more complex soil fauna food web structure. Comparatively, the higher Shannon–Wiener index (1.42–1.74) and Pielou evenness index (0.58–0.71) and the lower Simpson dominance index (0.22–0.32) in the MF suggested that the MF promoted the soil fauna diversity. The cumulative litter decomposition rate of litterbags with 4 mm aperture in the MF (54.52% in 300 days) was higher than that in the LF (32.81% in 300 days). Moreover, the litter decomposition rate was positively correlated with the total abundance and the number of groups, and was negatively with the Simpson dominance index, implying that the soil fauna activity effectively improved litter decomposition in the MF. Via the comparison, we found that the mixture of plant species in the forest can modulate the soil fauna diversity and accelerate the litter decomposition. The results in this study may provide an interesting reference for forest restoration and sustainable management.

Multiple roles of bamboo as a regulator of cyanobacterial bloom in aquatic systems

To understand the potential roles of terrestrial bamboo on controlling cyanobacterial blooms in aquatic systems, growth rates of the cyanobacterium Microcystis aeruginosa and its competitor algae were examined under different concentrations of bamboo extract. In mono-species cultures with unicellular algal strains, 5.0 g L-1 extract treatment suppressed M. aeruginosa growth, while it had little effect on the growth of green alga Scenedesmus obliquus or promoted the growth of diatom Nitzschia palea. In co-species cultures, the extract treatment increased the effect of S. obliquus and N. palea on the growth of M. aeruginosa. Under the extract treatment with a field-collected M. aeruginosa population, its cell density declined and its colony was etiolated and sank, while co-cultured N. palea increased explosively by invading the colony. These results suggest that bamboo forest stands along banks and artificially installed bamboo poles can affect the aquatic environment for phytoplankton community. Enhancing the growth of competitors, especially diatoms that can invade cyanobacterial colonies, by using extracts or by providing substrates for growth, was suggested to be the major way of the bloom control by bamboo.