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2,078 results for “soil data”
Data from: Earthworms and cadmium – heavy metal resistant gut bacteria as indicators for heavy metal pollution in soils?
Preservation of the soil resources stability is of high importance for ecosystems, particularly in the current era of environmental change, which presents a severe pollution burden (e.g. by heavy metals) to soil fauna. Gut microbiomes are becoming recognized as important players in organism health, with comprehension of their perturbations in the polluted environment offering new insights into the nature and extent of heavy metal effects on the health of soil biota. Our aim was to investigate the effect of environmentally relevant heavy metal concentrations of cadmium (Cd) on the earthworm (Lumbricus terrestris) gut microbiota. Our results revealed that Cd exposure led to perturbations of earthworm gut microbiota with an increase in bacteria previously described as heavy metal resistant or able to bind heavy metals, revealing the potential of the earthworm-gut microbiota system in overcoming human-caused heavy metal pollution. Furthermore, an 'indicator species analysis' linked the bacterial genera Paenibacillus, Flavobacterium and Pseudomonas, with Cd treatment, suggesting these bacterial taxa as biomarkers of exposure in earthworms inhabiting Cd-stressed soils. The results of this study help to understand the impact of anthropogenic disturbance on soil fauna health and will have implications for environmental monitoring and protection of soil resources.
Data from: Spatial variation of soil respiration in a cropland under winter wheat and summer maize rotation in the North China Plain
Spatial variation of soil respiration (Rs) in cropland ecosystems must be assessed to evaluate the global terrestrial carbon budget. This study aims to explore the spatial characteristics and controlling factors of Rs in a cropland under winter wheat and summer maize rotation in the North China Plain. We collected Rs data from 23 sample plots in the cropland. At the late jointing stage, the daily mean Rs of summer maize (4.74 μmol CO2 m-2 s-1) was significantly higher than that of winter wheat (3.77μmol CO2 m-2 s-1). However, the spatial variation of Rs in summer maize (coefficient of variation, CV = 12.2%) was lower than that in winter wheat (CV = 18.5%). A similar trend in CV was also observed for environmental factors but not for biotic factors, such as leaf area index, aboveground biomass, and canopy chlorophyll content. Pearson's correlation analyses based on the sampling data revealed that the spatial variation of Rs was poorly explained by the spatial variations of biotic factors, environmental factors, or soil properties alone for winter wheat and summer maize. The similarly non-significant relationship was observed between Rs and the enhanced vegetation index (EVI), which was used as surrogate for plant photosynthesis. EVI was better correlated with field-measured leaf area index than the normalized difference vegetation index and red edge chlorophyll index. All the data from the 23 sample plots were categorized into three clusters based on the cluster analysis of soil carbon/nitrogen and soil organic carbon content. An apparent improvement was observed in the relationship between Rs and EVI in each cluster for both winter wheat and summer maize. The spatial variation of Rs in the cropland under winter wheat and summer maize rotation could be attributed to the differences in spatial variations of soil properties and biotic factors. The results indicate that applying cluster analysis to minimize differences in soil properties among different clusters can improve the role of remote sensing data as a proxy of plant photosynthesis in semi-empirical Rs models and benefit the acquisition of Rs in cropland ecosystems at large scales.
Data from: Root biomass and exudates link plant diversity with soil bacterial and fungal biomass
Plant diversity has been shown to determine the composition and functioning of soil biota. Although root-derived organic inputs are discussed as the main drivers of soil communities, experimental evidence is scarce. While there is some evidence that higher root biomass at high plant diversity increases substrate availability for soil biota, several studies have speculated that the quantity and diversity of root inputs into the soil, i.e. though root exudates, drive plant diversity effects on soil biota. Here we used a microcosm experiment to study the role of plant species richness on the biomass of soil bacteria and fungi as well as fungal-to-bacterial ratio via root biomass and root exudates. Plant diversity significantly increased shoot biomass, root biomass, the amount of root exudates, bacterial biomass, and fungal biomass. Fungal biomass increased most with increasing plant diversity resulting in a significant shift in the fungal-to-bacterial biomass ratio at high plant diversity. Fungal biomass increased significantly with plant diversity-induced increases in root biomass and the amount of root exudates. These results suggest that plant diversity enhances soil microbial biomass, particularly soil fungi, by increasing root-derived organic inputs.
Data from: Convergence of soil nitrogen isotopes across global climate gradients
Quantifying global patterns of terrestrial nitrogen (N) cycling is central to predicting future patterns of primary productivity, carbon sequestration, nutrient fluxes to aquatic systems, and climate forcing. With limited direct measures of soil N cycling at the global scale, syntheses of the 15N:14N ratio of soil organic matter across climate gradients provide key insights into understanding global patterns of N cycling. In synthesizing data from over 6000 soil samples, we show strong global relationships among soil N isotopes, mean annual temperature (MAT), mean annual precipitation (MAP), and the concentrations of organic carbon and clay in soil. In both hot ecosystems and dry ecosystems, soil organic matter was more enriched in 15N than in corresponding cold ecosystems or wet ecosystems. Below a MAT of 9.8°C, soil δ15N was invariant with MAT. At the global scale, soil organic C concentrations also declined with increasing MAT and decreasing MAP. After standardizing for variation among mineral soils in soil C and clay concentrations, soil δ15N showed no consistent trends across global climate and latitudinal gradients. Our analyses could place new constraints on interpretations of patterns of ecosystem N cycling and global budgets of gaseous N loss.
Data from: When mutualisms matter: Rhizobia effects on plant communities depend on host plant population and soil nitrogen availability
1.Mutualistic interactions, such as the relationship between legumes and rhizobia, can affect community properties, yet there needs to be greater understanding of when these interactions may be most important to communities. Resource mutualism theory provides predictions based on variation in abiotic and biotic factors. First, there is substantial intraspecific genetic variation in how legumes interact with rhizobia, including variation in legume growth response to rhizobia, number of rhizobia-housing nodules, and nitrogen fixation. Rhizobia likely have greater community impacts when associating with hosts that benefit greatly from rhizobia, produce many nodules, and fix a lot of nitrogen. Second, increased soil nutrient availability typically reduces the partner benefits of legume-rhizobium interactions. As a result, the legume-rhizobium resource mutualism may have greater effects on communities in low nitrogen environments. 2.We first conducted a common garden study of the annual legume Chamaecrista fasciculata to explore intraspecific variation in focal traits related to competition and mutualistic interactions with rhizobia. Then, we manipulated the presence of rhizobia, nitrogen fertilization, and population identity of C. fasciculata in mesocosms simulating native plant communities. We measured plant diversity, assessed changes in community composition, and measured soil nutrient availability. 3.We detected significant genetically-based intraspecific variation in growth and mutualism related traits across C. fasciculata populations. From the experimental mesocosms, we found that although rhizobia consistently reduced diversity, rhizobia most strongly reduced diversity when associating with C. fasciculata populations that were highly dependent on rhizobia and when nitrogen was most limiting. We also detected greater variation among populations in their effects on communities in the absence of rhizobia; the presence of rhizobia dramatically minimized effects of population identity on the surrounding community. 4.Synthesis. These findings show that abiotic environmental factors and intraspecific variation in a dominant host plant can influence the magnitude of mutualism effects on communities and, reciprocally, how the presence of key mutualists can influence the importance of genetically-based variation among populations to community outcomes. While prior studies have detected both strong and weak effects of mutualism on plant communities, our study illustrates that mutualism theory may predict when strong mutualism effects are most likely to occur and also shows how theories developed for particular species interactions may make studies investigating the ecological impacts of genetic variation a more predictive science.
Data from: Removal of an apex predator initiates a trophic cascade that extends from herbivores to vegetation and the soil nutrient pool
It is widely assumed that organisms at low trophic levels, particularly microbes and plants, are essential to basic services in ecosystems, such as nutrient cycling. In theory, apex predators' effects on ecosystems could extend to nutrient cycling and the soil nutrient pool by influencing the intensity and spatial organization of herbivory. Here, we take advantage of a long-term manipulation of dingo abundance across Australia's dingo-proof fence in the Strzelecki Desert to investigate the effects that removal of an apex predator has on herbivore abundance, vegetation and the soil nutrient pool. Results showed that kangaroos were more abundant where dingoes were rare, and effects of kangaroo exclusion on vegetation, and total carbon, total nitrogen and available phosphorus in the soil were marked where dingoes were rare, but negligible where dingoes were common. By showing that a trophic cascade resulting from an apex predator's lethal effects on herbivores extends to the soil nutrient pool, we demonstrate a hitherto unappreciated pathway via which predators can influence nutrient dynamics. A key implication of our study is the vast spatial scale across which apex predators' effects on herbivore populations operate and, in turn, effects on the soil nutrient pool and ecosystem productivity could become manifest.
Data from: Differences in thallus chemistry are related to species-specific effects of biocrust-forming lichens on soil nutrients and microbial communities
1. It is well-known that vascular plants have species-specific effects on soil properties. However, little is known on how individual species forming biocrusts, communities dominated by lichens, mosses and cyanobacteria that are prevalent in many ecosystems world-wide, affect microbial communities and soil variables related to nutrient cycling. 2. We evaluated the relationship of six biocrust-forming lichens (Buellia epipolia, Diploschistes diacapsis, Fulgensia subbracteata, Psora decipiens, Squamarina cartilaginea and Squamarina lentigera) with microbial abundance and multiple variables associated with soil nitrogen (N), carbon (C) and phosphorus (P) cycling and storage. We also evaluated whether the composition of lichen tissues (contents in C, N, P and polyphenols) is related to the C, N, P availability and microbial abundance in soils. Finally, we assessed what lichen species positively and negatively relate to soil fertility compared to bare ground areas without biocrusts. 3. We found contrasted C, N, P availability and soil microbial abundance under the different biocrust-forming lichens. Interestingly, inorganic P and amino acids were the most important factors differentiating lichen microsites. These differences in nutrient availability seem to be related to the C, N and P composition of the lichen tissues. For example, soils under D. diacapsis and P. decipiens, which had the lowest and highest C, N and P contents in their tissues, respectively, had the lowest and highest nutrient availability, respectively. We also found contrasted soil microbes abundance under the different soil lichens. For instance, F. subbracteata and D. diacapsis were negatively related to the abundance of bacteria compared to bare ground areas. 4. Our results support the idea that, as found with vascular plants, biocrust-forming lichens have species-specific effects on soil microbial communities and C, N and P cycling. Thus, continuing considering biocrusts as a unique entity will only add confusion to our knowledge of how they control nutrient availability and microbial abundance in the ecosystems where this key community is prevalent.
Data from: Resource heterogeneity, soil fertility, and species diversity: effects of clonal species on plant communities
Spatial heterogeneity in soil resources is widely thought to promote plant species coexistence, and this mechanism figures prominently in resource-ratio models of competition. However, most experimental studies have found that nutrient enhancements depress diversity regardless of whether nutrients are uniformly or heterogeneously applied. This mismatch between theory and empirical pattern is potentially due to an interaction between plant size and the scale of resource heterogeneity. Clonal plants that spread vegetatively via rhizomes or stolons can grow large and may integrate across resource patches, thus reducing the positive effect of small-scale resource heterogeneity on plant species richness. Many rhizomatous clonal species respond strongly to increased soil fertility, and they have been hypothesized to drive the descending arm of the hump-shaped productivity-diversity relationship in grasslands. We tested whether clonals reduce species richness in a grassland community by manipulating nutrient heterogeneity, soil fertility, and the presence of rhizomatous clonal species in a 6-year field experiment. We found strong and consistent negative effects of clonals on species richness. These effects were greatest at high fertility and when soil resources were applied at a scale at which rhizomatous clonals could integrate across resource patches. Thus, we find support for the hypothesis that plant size and resource heterogeneity interact to determine species diversity.
Data from: Grazing and resource availability control soil nematode body size and abundance-mass relationship in semi-arid grassland
1. Body size is a central functional trait in ecological communities. Despite recognition of the importance of above-belowground interactions, effects of aboveground herbivores on size and abundance-size relationships in soil fauna are almost uncharted. Depending on climate and soil properties, herbivores may increase basal resources of soil food webs, or reduce pore space, mechanisms expected to have contrasting effects on soil animal body size. 2. We investigated how body size and shape of soil nematodes responded to mammalian grazers in three semi-arid grassland sites, along a gradient of soil texture and organic matter (OM) in a long-term herbivore removal study. We analysed nematode mass, length, diameter, body size distribution, and biomass distribution. We formulated two mechanistic hypotheses to assess whether resource availability or pore space was the dominant abiotic control and modulated the effects of grazing. 3. In ungrazed soils, average and maximum nematode size, as well as abundance and biomass of large nematodes, were greater in the high-OM than in the low-OM soil, and intermediate in the medium-OM soil. Grazing promoted larger sizes in the low-OM soil, where it had been shown to increase organic matter and microbial biomass, and led to more homogeneous average size and body size distribution across sites. The results support the hypothesis that nematode size was controlled by basal resource availability rather than by pore space. However, body shape might have been constrained by small pores in the fine-texture, high-OM soil, where nematodes were more elongated. 4. Grazing may facilitate larger sizes in soil nematode communities by boosting basal resources where these are limiting, with important implications for estimations of nematode biomass and contribution to carbon and nutrient cycling. These findings contribute to the insofar-limited mechanistic understanding of how herbivores can shape functional traits of soil fauna, and demonstrate that animals at one trophic level may control patterns in body size and abundance-size relationships in other trophic levels without a direct predator-prey or competitive linkage between them.
Data from: Plant community evenness responds to spatial plant-soil feedback heterogeneity primarily through the diversity of soil conditioning
1.Plant-soil feedback (PSF) has been identified as a key driver of local plant diversity and evenness in competitive communities. However, while it has been shown that spatial PSF heterogeneity can alter plant performance and competitive interactions, there is no proof of principle that spatial PSF heterogeneity enhances community diversity. 2.Using a grassland model system we separated two aspects of spatial heterogeneity: the number of species conditioning the soil and spatial distribution of the PSFs. 3.Our data show that PSFs promoted a higher plant evenness when the soil was conditioned by multiple species (mixed-conditioned), then when the soil was conditioned by a single species (mono-conditioned). On mono-conditioned soils, heterospecifics typically outperformed the focal species. In addition, there was a trend for increasing community evenness from uniform, via fine-grained to coarse-grained mixed-conditioned soils, but this was not significant. 4.On mixed-conditioned soils, performance of all competing species was intermediate to the best and the worst mono-conditioned soils, leading to higher community evenness. 5.Our data demonstrate that PSFs play a role in promoting plant evenness. Across mono-conditioned soils, PSF led to altered competitive hierarchies. However, on soils conditioned by multiple species, competitive ability among species was more similar and this led to higher plant evenness. The spatial distribution of the heterogeneity, on the other hand, did not significantly affect plant evenness. Our data therefore show that community evenness was more strongly related to the number of plant species that conditioned the soil than the spatial distribution of the PSF heterogeneity. Future studies need to investigate the importance of PSFs in the field across plant life-stages and multiple generations.
Data from: Plant competition alters the temporal dynamics of plant-soil feedbacks
1. Most studies on plant-soil feedback (PSF) and plant competition measure the feedback response at one moment only. However, PSFs and competition may both change over time, and how PSF and competition interact over time is unclear. 2. We tested the temporal dynamics of PSF and interspecific competition for the forb Jacobaea vulgaris and the grass Holcus lanatus. We grew both species individually and in interspecific competition in soil that was first conditioned in the greenhouse by J. vulgaris, by H. lanatus or without plant growth. For a period of 11 weeks, we harvested plants twice a week and analyzed the fungal and chemical composition of the different soils at the end of the first and second growth phase. 3. During the second growth phase, when grown in isolation, both species produced more biomass in heterospecific conditioned soil than in conspecific conditioned soil. Young J. vulgaris exhibited a strong negative conspecific feedback, but this effect diminished over time and became neutral in older plants. In contrast, when grown in competition, the negative conspecific feedback of J. vulgaris exacerbated over time. Older H. lanatus plants benefited more from heterospecific conditioning when competing with J. vulgaris, then when grown isolated. 4. Fungal community composition and soil chemistry differed significantly between soils but this was mainly driven by differences between plant-conditioned and unconditioned soils. Remarkably, at the end of the second growth phase, fungal community composition was not explained by the legacy of the species that had been grown in the soil most recently, but still reflected the legacy of the first growth phase. We reexamined plant growth during a third growth phase. Biomass of J. vulgaris was still influenced by the treatments imposed during the first phase, while H. lanatus responded only to the plant growth treatments imposed during the second phase. 5. Synthesis: Our study shows that the direction and magnitude of PSF depends on plant age and competition but also on soil legacy effects of earlier plant growth. These results highlight the need to incorporate dynamic PSFs in research on plant populations and communities.
Data from: Deciphering the associations between soil microbial diversity and ecosystem multifunctionality driven by long-term fertilization management
1.An increasing number of studies indicate that microbial diversity plays a crucial role in the mediation of ecosystem multifunctionality (EMF) in natural ecosystems. However, this point remains mostly overlooked in managed ecosystems, especially in agriculture. 2.Here, we compiled promising strategies for the targeted exploitation of the associations between microbial diversity and EMF of agricultural soils using samples from two long-term (more than 30 years) experimental field sites in southern China. The two sites experienced a similar subtropical monsoon climate and fertilization management practices. We used high-throughput amplicon sequencing, structural equation modeling (SEM), and random forest analysis, to analyze our data and validate our hypotheses. 3.We found that soil physiochemical properties and the C-, N-, P- and S-cycle enzyme activities were increased with the increase of microbial diversity. Specifically, a positive linear relationship was observed between microbial diversity and EMF, which was mediated by long-term fertilization management via changes in soil microbial communities and physiochemical properties. Random forest analysis and SEM showed that the important role of microbial diversity on EMF was maintained even when simultaneously taking multiple multifunctionality drivers (soil physiochemical properties, soil aggregation and enzymatic patterns) into account. In addition, microbial diversity, C-cycle enzyme activity and pH value are feasible predictors of EMF; these factors were shown to be the main drivers of EMF of arable soils. 4. Our findings suggest that there may be a limited degree of multifunctional redundancy in arable soils. The relationship we observed between microbial diversity and EMF suggests that management practices that foster more diverse soil microbial communities may have the potential to improve the functioning of agroecosystems.
Data from: Effect of soil pH increase by biochar on NO, N2O and N2 production during denitrification in acid soils
Biochar (BC) application to soil suppresses emission of nitrous- (N2O) and nitric oxide (NO), but the mechanisms are unclear. One of the most prominent features of BC is its alkalizing effect in soils, which may affect denitrification and its product stoichiometry directly or indirectly. We conducted laboratory experiments with anoxic slurries of acid Acrisols from Indonesia and Zambia and two contrasting BCs produced locally from rice husk and cacao shell. Dose-dependent responses of denitrification and gaseous products (NO, N2O and N2) were assessed by high-resolution gas kinetics and related to the alkalizing effect of the BCs. To delineate the pH effect from other BC effects, we removed part of the alkalinity by leaching the BCs with water and acid prior to incubation. Uncharred cacao shell and sodium hydroxide (NaOH) were also included in the study. The untreated BCs suppressed N2O and NO and increased N2 production during denitrification, irrespective of the effect on denitrification rate. The extent of N2O and NO suppression was dose-dependent and increased with the alkalizing effect of the two BC types, which was strongest for cacao shell BC. Acid leaching of BC, which decreased its alkalizing effect, reduced or eliminated the ability of BC to suppress N2O and NO net production. Just like untreated BCs, NaOH reduced net production of N2O and NO while increasing that of N2. This confirms the importance of altered soil pH for denitrification product stoichiometry. Addition of uncharred cacao shell stimulated denitrification strongly due to availability of labile carbon but only minor effects on the product stoichiometry of denitrification were found, in accordance with its modest effect on soil pH. Our study indicates that stimulation of denitrification was mainly due to increases in labile carbon whereas change in product stoichiometry was mainly due to a change in soil pH.
Data from: Ectomycorrhizas and tree seedling establishment are strongly influenced by forest edge proximity but not soil inoculum
Reforestation is challenging when timber harvested areas have been degraded, invaded by non-native species, or are of marginal suitability to begin with. Conifers form mutualistic partnerships with ectomycorrhizal fungi (EMF) to obtain greater access to soil resources, and these partnerships may be especially important in degraded areas. However, timber harvest can impact mycorrhizal fungi by removing or compacting topsoil, removing host plants, and warming and drying the soil. We used a field experiment to evaluate the role of EMF in Douglas-fir reforestation in clearcuts invaded by Cytisus scoparius (Scotch broom) where traditional reforestation approaches have repeatedly failed. We tested how planting distance from intact Douglas-fir forest edges influenced reforestation success and whether inoculation with forest soils can be used to restore EMF relationships. We used an Illumina DNA sequencing approach to measure the abundance, richness and composition of ectomycorrhizal fungi on Douglas-fir roots, and assessed differences in Douglas-fir seedling survival and growth near to and far from forest edges with and without forest soil inoculum. Planting Douglas-fir seedlings near forest edges increased seedling survival, growth and EMF root colonization. Edge proximity had no effect on EMF richness but did change fungal community composition. Inoculations with forest soil did not increase EMF abundance or richness or change community composition, nor did it improve seedling establishment. With Illumina sequencing we identified two to three times greater species richness than described in previous edge effects studies. Of the 95 EMF species we identified, 40% of the species occurred on less than 5% of the seedlings. The ability to detect fungi at low abundance may explain why we did not detect differences in EMF richness with distance to hosts as previous studies. Our findings suggest that forest edges are suitable for reforestation, even when the interiors of deforested areas are not. We advocate for timber harvest designs that maximize edge habitat where ectomycorrhizal fungi contribute to tree establishment. However, this study does not support the use of inoculation with forest soil as a simple method to enhance EMF and seedling survival.
Data from: Plant, soil and microbial controls on grassland diversity restoration: a long-term, multi-site mesocosm experiment
The success of grassland biodiversity restoration schemes is determined by many factors; as such their outcomes can be unpredictable. There is a need for improved understanding of the relative importance of belowground factors to restoration success, such as contrasting soil type and management intensities, as well as plant community composition and order of assembly. We carried out an eight-year mesocosm experiment across three locations in the UK to explore the relative and interactive roles of various aboveground and belowground factors in the establishment of target species, to determine general constraints on grassland restoration. Each location had a series of mesocosms with contrasting soil types and management status, which were initially sown with six grasses typical of species-poor grasslands targeted for restoration. Over five years, sets of plant species were added, to test how different vegetation treatments, including early-coloniser species and the hemiparasite Rhinanthus minor, and soil type and management, influenced the establishment of target plant species and community diversity. The addition of early-coloniser species to model grasslands suppressed the establishment of target species, indicating a strong priority effect. Soil type was also an important factor, but effects varied considerably across locations. In the absence of early-coloniser species, low soil nutrient availability improved establishment of target species across locations, although R. minor had no beneficial effect. Synthesis and applications. Our long-term, multi-site study indicates that successful restoration of species rich grassland is dependent primarily on priority effects, especially in the form of early-coloniser species that suppress establishment of slow-growing target species. We also show that priority effects vary with soil conditions, being stronger in clay than sandy soils, and on soils of high nutrient availability. As such, our work emphasises the importance of considering priority effects and local soil conditions in developing management strategies for restoring plant species diversity in grassland.
Data from: Encroachment of shrubs into subalpine grasslands in the Pyrenees modifies the structure of soil fungal communities and soil properties.
The encroachment of shrubs into grasslands is common in terrestrial ecosystems dominated by grass. Land abandonment and favourable climatic trends in recent decades have favoured the expansion of shrubs into subalpine grasslands in many mountainous regions across Europe. The advance of the succession from grassland to shrubland is expected to have a major impact on ecosystem functioning. We used DNA metabarcoding to assess whether the structure of soil fungal communities varied along the succession from subalpine grassland to shrubland in the Pyrenees, and investigated whether shrub encroachment was associated with changes in soil properties. The expansion of shrubs increased the soil C:N ratio and/or reduced the N, P, or K contents. Plant-driven changes in soil properties were strongly associated with the compositional turnover of fungi, including arbuscular mycorrhizal, ectomycorrhizal, ericoid, root endophytic, saprotrophic, lichenised, and pathogenic fungi. Total richness and the richness of most functional groups were correlated with soil P, N, and the C:N or N:P ratios. We show that the interplay between abiotic factors (changes in soil properties) and biotic factors (occurrence and identity of shrubs) played a key role in the structure and uniqueness of soil fungal communities along the succession.
Data from: Critical analysis of forest degradation in the southern Eastern Ghats of India: comparison of satellite imagery and soil quality index
India has one of the largest assemblages of tropical biodiversity, with its unique floristic composition of endemic species. However, current forest cover assessment is performed via satellite-based forest surveys, which have many limitations. The present study, which was performed in the Eastern Ghats, analysed the satellite-based inventory provided by forest surveys and inferred from the results that this process no longer provides adequate information for quantifying forest degradation in an empirical manner. The study analysed 21 soil properties and generated a forest soil quality index of the Eastern Ghats, using principal component analysis. Using matrix modules and geospatial technology, we compared the forest degradation status calculated from satellite-based forest surveys with the degradation status calculated from the forest soil quality index. The Forest Survey of India classified about 1.8% of the Eastern Ghats' total area as degraded forests and the remainder (98.2%) as open, dense, and very dense forests, whereas the soil quality index results found that about 42.4% of the total area is degraded, with the remainder (57.6%) being non-degraded. Our ground truth verification analyses indicate that the forest soil quality index along with the forest cover density data from the Forest Survey of India are ideal tools for evaluating forest degradation.
Data from: Aboveground mammal and invertebrate exclusions cause consistent changes in soil food webs of two subalpine grassland types, but mechanisms are system-specific
Ungulates, smaller mammals, and invertebrates can each affect soil biota through their influence on vegetation and soil characteristics. However, direct and indirect effects of the aboveground biota on soil food webs remain to be unraveled. We assessed effects of progressively excluding aboveground large-, medium- and small-sized mammals as well as invertebrates on soil nematode diversity and feeding type abundances in two subalpine grassland types: short- and tall-grass vegetation. We explored pathways that link exclusions of aboveground biota to nematode feeding type abundances via changes in plants, soil environment, soil microbial biomass, and soil nutrients. In both vegetation types, exclusions caused a similar shift toward higher abundance of all nematode feeding types, except plant feeders, lower Shannon diversity, and lower evenness. These effects were strongest when small mammals, or both small mammals and invertebrates were excluded in addition to excluding larger mammals. Exclusions resulted in a changed abiotic soil environment that only affected nematodes in the short-grass vegetation. In each vegetation type, exclusion effects on nematode abundances were mediated by different drivers related to plant quantity and quality. In the short-grass vegetation, not all exclusion effects on omni–carnivorous nematodes were mediated by the abundance of lower trophic level nematodes, suggesting that omni–carnivores also depended on other prey than nematodes. We conclude that small aboveground herbivores have major impacts on the soil food web of subalpine short- and tall-grass ecosystems. Excluding aboveground animals caused similar shifts in soil nematode assemblages in both subalpine vegetation types, however, mechanisms turned out to be system-specific.
Data from: Towards a mechanistic understanding of the effect that different species of large grazers have on grassland soil N availability
1. Herbivore grazing has major effects on soil nutrient dynamics in a variety of grassland ecosystems. Previous studies have examined how large herbivores as a group affect nutrient cycling, but little information is available on how assemblages of different herbivore species may influence nutrient cycling, and whether herbivore assemblage effects are influenced by plant community characteristics (e.g., composition, diversity) of the grazed grassland. 2. We conducted a five-year, replicated grazing experiment to test the effects of different large herbivore assemblages (cattle grazing, sheep grazing, combined cattle and sheep grazing, no grazing) under moderate grazing intensity on soil nitrogen (N) mineralization rate in two types of grassland communities (high forbs/high diversity and low forbs/low diversity) in meadow steppe habitat of northeast China. Moreover, we examined two distinctly different pathways that herbivores could influence soil N availability: directly through urine and dung deposition and indirectly by shifting grassland species composition (i.e., the grass: forb ratio), thereby the quality of plant litter available to soil decomposers. 3. We found that grazer effects on soil N availability (indexed with anion and cation adsorption strips) depended on herbivore assemblage, and the herbivore assemblage effects varied in the two types of grasslands. In one type of grassland characterized by low diversity, grazing by each of the herbivore assemblages enhanced soil N availability compared to the ungrazed plots, and mixed species (cattle and sheep) grazing had a greater effect than single species grazing. In high diversity grassland, single species herbivore grazing significantly increased soil N availability, but mixed grazing had no effect. 4. Mixed linear modelling revealed that soil N availability was facilitated primarily by excreta additions to the soil and secondarily by the abundance of grasses. 5. Synthesis. Grazers increased soil N availability directly by adding readily accessible N in urine and dung to the soil. Herbivores indirectly influenced soil N availability by altering the plant composition (grass: forb cover). Both mechanisms contributed to the variation in how different herbivore assemblages affected soil N availability in the two grassland types.
Data from: Competitor relatedness, indirect soil effects and plant co-existence
How species co-exist is a central question in ecology. Niche differentiation can prevent two species from excluding each other by competition. However, this interaction can vary in space because of internal factors such as intraspecific genetic variation, or external ones such as the presence of a third species. While these effects have been repeatedly observed, their joint effect on the outcome of competition has rarely been considered. We experimentally investigated how a dominant ecosystem engineer (the shrub Thymus vulgaris) affects interactions between two co-occurring and closely related annuals (Medicago minima and M. rigidula). We ask first if the outcome of their interaction depends on the genetic identity of the competitors, and in particular if intraspecific interaction differs between genetically related versus unrelated conspecifics. Second, we ask if co-existence of the two species is modified by the presence of thyme plants altering local soil conditions. We grew genotypes collected in nature of both annual species in inter- and intraspecific competition experiments using soil collected directly underneath thyme plant (thyme soil), and soil collected away from thyme plants (no-thyme soil). We found that thyme soil affected interactions in a way that shifted the species' rank. Crucial for this result was the division of intraspecific competition between genetically related and unrelated individuals. Intraspecific competition was significantly less detrimental to kin than to unrelated conspecifics. In highly structured plant populations, such effects could favor local dominance of a patch by one species. However this kin effect occurred for each species only in its preferred soil (thyme versus no-thyme), promoting a stabilizing co-existence mechanism at the landscape level. Synthesis: This study shows that the importance of intraspecific competition relative to interspecific competition can be highly dependent on the genotype identity of intraspecific competitors and of the local environment in which the interaction occurs. The local environment can itself be modified by the presence of a third species in the community. These results emphasize how, in order to understand the overall problem of species co-existence, it can be insightful to divide this into smaller local scale problems of co-existence.
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Allen Brain Atlas
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Annotated Behaviour and Observability Dataset (ABODe)
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