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Although there are undoubtedly some environmental fluctuations that are sufficient to overcome the capacity of diversity to respond, a general consensus emerging from studies of biodiversity is that diversity commonly decreases realized disturbance Figure 2 , and reduces variability in community traits e. Figure 4: Effects of salmon population diversity on catch variation in Bristol Bay, AK The coefficient of variation from year to year in total sockeye salmon returns at three spatial scales streams to rivers to bay-wide and two levels of life history aggregation circles represent age structured data and triangles represent variation within dominant age classes.
Gray symbols are from the Wood River system, with continuous long-term data on stream populations. Black symbols are for all rivers in Bristol Bay Schindler et al.
In addition to effects of species diversity, population and genetic variation within species can also affect realized disturbance and variability over time see references in Hughes et al. In some cases, the effects of diversity within species can be far-reaching.
For example, diversity among sockeye salmon populations in life history characteristics and spawning habitat increases resistance to disturbance and enhances productivity and sustainability in the sockeye salmon fishery, currently the most valuable fishery in the US Hilborn et al. In this case, the agent of distrurbance is fishing itself, which results in the removal of salmon biomass from the community. Without the buffering effects of population and life history diversity, variability in overall salmon abundance would increase, leading to a fold increase in fishery closures Schindler et al.
These benefits of salmon population diversity in the face of fishing pressure argue for greater attention to the influence of within-species diversity on disturbance response and stability.
As with the effects of disturbance on species diversity, the shape of the relationship between diversity and disturbance response can vary Figure 2 , although diversity most commonly reduces realized disturbance Hughes et al. Because experimental tests of the effects of diversity typically manipulate common species in the community of interest, they may actually underestimate the impact of diversity: uncommon species can play an important role in the response to disturbance and environmental change Lyons et al.
Future studies need to incorporate variation in relative abundance as well as diversity to tease apart these effects. The role of rare species provides one example of the chicken and egg nature of the diversity-disturbance relationship: disturbance can promote the coexistence of less common species by preventing competitive exclusion e. Thus, the diversity-disturbance relationship may be more cyclical than unidirectional, with both directions of causation operating simultaneously: disturbance changes diversity, which changes the response of the community to future disturbance, and so on Hughes et al.
Several lines of evidence support the suggestion that there are reciprocal effects of disturbance and diversity. First, as detailed above, there is substantial evidence for each of the one-way relationships disturbance affects diversity and diversity affects realized disturbance.
In addition, each of these one-way relationships has been documented in the same system at similar spatial scales e. Although the point of dual causation between diversity and disturbance may appear both obvious and esoteric, failing to consider the reciprocal effects of one upon the other could hinder management and conservation decisions.
For instance, sockeye salmon population diversity clearly reduces variability in catch Hilborn et al. Conversely, if fishing pressure, land and hydrological alteration, and climate change continue to reduce population diversity Gustafson et al.
Thus considerations of diversity and its stabilizing effects are necessary for effective management of this system. It turns out that this chicken and egg issue is not limited to the relationship between disturbance and diversity; in fact, there are a variety of ecological processes that are both a cause and a consequence of biodiversity.
For example, productivity, or resource availability, can be an important determinant of community diversity MacArthur ; Loreau et al.
Resolving the nature and direction of the diversity-productivity relationship has thus been the focus of numerous studies Loreau et al. A similar example comes from studies of diversity and species invasion: increased diversity in experimental manipulations typically leads to reduced invasion success Levine et al. Though not the focus of this article, these examples support recent suggestions that reciprocal i.
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Leaf traits represent resource use, and plant height and crown cover CC for competitive ability and seed mass embody the response to perturbations Westoby, Table 2 represents the rationale behind the selection of plant traits and associated variables. Plant height was measured using a clinometer. Samples were collected aiming for leaves fully expanded with little or no damage by herbivores or pathogens.
Fresh weight was taken by a portable weighing machine after drying through gently blotting with tissue paper to remove any surface water. After sampling, the leaves were air dried and transported in sealed plastic bags to the laboratory. Table 2. Five randomly located soil core samples at depths of 0—10, 10—20, and 20—30 cm were collected from each plot using a soil corer of 5 cm diameter.
Soil microbial carbon and soil microbial nitrogen were estimated following the chloroform fumigation-extraction method Brookes et al. Soil samples from each disturbed class were collected to make composite samples from varying depths that were sent for DNA extraction and purification in the laboratory.
Metagenomics sequencing was performed on the collected soil sample 0. Forty nanograms of extracted DNA were used for amplification along with 10 pM of each primer.
The amplicons from each sample were purified with Ampure beads to remove unused primers and eight additional cycles of PCR were performed using Illumina barcoded adapters to prepare the sequencing libraries. This workflow enables highly accurate investigations at the genus level. Each read was classified based on percent coverage and identity. Kernel density plots were drawn for each plant trait and soil variables to understand the variability within each disturbed site.
Principal component analysis PCA was performed including the plant traits for individuals in the study sites and soil properties from each plot. The importance value index of plant species was calculated following Curtis , and its association with different plant traits and soil parameters was determined using canonical correspondence analysis CCA.
CCA was also used to explore changes in traits and diversity with forest disturbances. Pearson correlations were performed to examine the relationships between soil microbial communities, PFTs, and plant community composition. All statistical analyses were conducted using R version 3. After phytosociological survey, 22 tree species having 1, individuals were found throughout the study site.
Total basal area and tree density were found to be maximum for the LDI site Total basal area of mature individuals was found to be significantly varying among the study sites Table 3. However, the differences were not significant for tree density. Plant SR varied from 0. CC was found to be varying throughout the study site due to the effect of lopping. SM showed greater variation within the study sites reflecting fundamental divergence in the phylogenetic distance between deciduous and evergreen species Figure 2.
Maximum variation accounted for SLA suggesting that with an increase in disturbance intensity, the values shifted toward species having higher trait values for acquisitive traits such as SLA, indicating higher competitive ability and faster resource acquisition. Table 3. One-way ANOVA table suggesting the effects of disturbance on plant traits, community composition, and soil properties followed by Tukey post hoc test.
Figure 2. Violin plots representing variation in plant traits and soil variables for each disturbed class. After quality trimming, a total of , sequences in moderately disturbed sites and , sequences in LDI sites were found. Analysis of soil bacterial community composition revealed sequences belonging to 19 phyla, 44 classes, 70 orders, families, and genera in soil samples across all the stands.
Furthermore, Nitrospirae, Gemmatimonadetes, Spirochetes, Chlamydiae, Nitrospirae, Chlorofelxi, Planctomycetes, and Fusobacteria were also present in the soil samples with varying proportions across the study sites. The alpha diversity indices Shannon and Simpson revealed similar patterns to plant species diversity and richness, i.
Phylotypes within Actinobacteria and Acidobacteria were found to be greater for moderately disturbed sites, whereas phylotypes within Proteobacteria, Planctomycetes, Verrucomicrobia, and Bacteroidetes were greater for LDI sites.
Soil microbial biomass carbon and nitrogen were found to increase around twofold with values being significantly greater for the LDI site and least for the MDI1 site Figure 2. One-way ANOVA test revealed that soil microbial biomass carbon and nitrogen were the most affected variables with increase in disturbance intensity Table 3. Figure 3. The relative abundance of soil bacteria at the phylum level across the disturbed sites.
Both plant species diversity and bacterial species diversity followed the same pattern being maximum for the MDI2 site and least for the LDI site. Pearson correlation coefficients calculated for plant traits, community characteristics, and soil microbial diversity along the disturbance gradient revealed that total basal area TBA and tree density DEN were found to have a positive correlation among the study sites Figure 4.
They were also found to have a strong positive correlation with soil MBC and MBN and bacterial phyla Proteobacteria, Planctomycetes, and Verrucomicrobia and negatively correlated with phyla Actinobacteria, Firmicutes, and Acidobacteria. Principal component analysis suggested that the first and second principal components explained HT was found to be negatively correlated with SM. CCA explained the relationship of plant community characteristics with soil variables in all the disturbed sites Figure 6.
Figure 4. Figure 5. Principal component analysis among all the plant traits and soil variables. Figure 6. CCA plot diagram to analyze the major gradients among the combination of explanatory variables.
The length of vectors in the ordination diagram represents the strength of the correlation, while the angle between two vectors shows the degree of correlation among variables with each axis.
In the present study, the effect of low- to moderate-level disturbances on plant community characteristics and functional traits along with soil microbial diversity in temperate reserved forests in the western Himalayan region was explored. However, there was no effect on HT and SM based on disturbance intensity. The findings indicate that low to moderate level of disturbance does not affect the community composition, but with increasing and continued disturbance intensity, species with conservative growth strategies promoting resistance of species to environmental stresses will be replaced with species having higher trait values for acquisitive traits such as SLA, indicating higher competitive ability and faster resource acquisition.
Here, the ecological significance of the present findings and their proper implications for sustainable forest management are discussed. This holds for the hypothesis suggesting that SR and diversity will not be affected because of limited disturbance activities throughout the study sites. This lack of effect was probably due to regular management implications that do not allow the local people to barely denude the tree individuals which affects their growth and survival.
However, SR was found to be increased by more than twofold in MDI2 sites that could be attributed to differences in management practices Toledo et al.
Studies have proven that mild disturbances provide greater opportunity for species turnover, establishment, and colonization, thus leading to higher SR Whittaker and Likens, ; Connell, ; Mishra et al.
Additionally, other factors might contribute to the differences among studies, such as topographical heterogeneity, environmental conditions, and forest types in the study site.
Local disturbance causes tree gaps resulting in scattered canopy that creates patches of greater light availability and availability of optimum resources and nutrients for lower subcanopy and regenerating species Raghubanshi and Tripathi, The findings tend to approach closer to the intermediate disturbance hypothesis theory which suggests an increase in species diversity with a low to moderate amount of disturbance Connell, The hypothesis that the increasing level of lopping intensity impacts forest community characteristics holds for tree basal area that tends to decrease with increase in disturbance intensities but remains insignificant for tree density and other community characteristics.
With an increase in disturbance intensity, SLA was found to be maximum at MDI2 sites suggesting shifting to acquisitive traits rather than conservative traits Kitajima and Poorter, ; Onoda et al.
Similar results were found in a study conducted by Hall et al. This suggests a faster turnover of plants as a response to disturbance Kazakou et al. LDI sites were found to have the lowest value for SLA, and such individuals tend to have longer leaf life spans causing lower growth rates Louault et al. SM was not found to be significantly affected by varying disturbance intensity, but within site, variation was mainly due to phylogenetic distances between the species.
Conifers in the study site are being characterized by a higher number of seeds with lower seed mass as compared with broadleaved trees that are known to have increased seed mass. CC is considered to be another trait that is highly affected by disturbance activities, especially lopping. Variation in CC further affects light intensity variation in the study site as well loss of structural components, i.
CCs are also known to be affected by topographic and edaphic conditions Lang, HT did not vary much with disturbance but was found to be lowest for the LDI site being less light demanding hence tends to be shorter, whereas for species at the MDI1 site being higher light demanding, successional species tends to be taller Falster and Westoby, This suggests that additional factors such as topography slope aspect and elevation , forest types, and environmental conditions Castro-Luna et al.
Therefore, the inclusion of the combined effect of disturbances, topographical heterogeneity, forest types, and environmental conditions might play an important role in the regulation of plant species diversity and functional traits in the study site. The study reported that soil bacterial communities were mostly composed of Proteobacteria, Acidobacteria, Actinobacteria, Planctomycetes, Verrucomicrobia, and Bacteroidetes across the study sites.
Various previous studies confirm the present findings conducted in temperate forest ecosystems Shen et al. It was found that plant species diversity and bacterial species diversity showed a similar pattern of increment with increment in disturbance intensity.
Thus, soil bacterial diversity was found to be positively correlated with plant species diversity. This might be due to an increase in aboveground plant communities and belowground microbial communities. Plant communities are also known to modify the resource availability and microclimatic conditions for belowground soil level which affects microbial growth responses Zumsteg et al.
The study was also in confirmation with other studies conducted in temperate grassland ecosystems Chai et al. Proteobacteria remained to be the most abundant bacterial phylum through the study site. These are represented by fast-growing copiotrophs that are acclimatized to increased carbon content and nutrient availability Cong et al.
This was in support of this study that showed increased density and basal area at LDI sites leading to higher carbon content and nutrient accumulation than other sites. This supports the suggested hypothesis that soil bacterial diversity would be largely determined by soil attributes supporting a strong correlation between soil microbial biomass and bacterial phyla.
Overview: the importance of spatial and temporal scale in ecological investigations. Download references. You can also search for this author in PubMed Google Scholar. Reprints and Permissions. Disturbance effects on plant community diversity: spatial scales and dominance hierarchies. Vegetatio 93, — Download citation. Accepted : 05 February Issue Date : May Anyone you share the following link with will be able to read this content:.
Sorry, a shareable link is not currently available for this article. Provided by the Springer Nature SharedIt content-sharing initiative. Skip to main content. Search SpringerLink Search. Abstract It is proposed that evaluations of disturbance effects upon community diversity will be influenced by two factors currently overlooked in models addressing disturbance-diversity relationships: 1 the spatial scale of inquiry, and 2 the level of the species abundance dominance hierarchy at which the search for diversity is done.
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