Nitrogen deposition and multi-dimensional plant diversity at the landscape scale

Roth, Tobias; Kohli, Lukas; Rihm, Beat; Amrhein, Valentin; Achermann, Beat

doi:10.1098/rsos.150017

Cited by 28 publications

(23 citation statements)

References 39 publications

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“…Contrasts between watersheds, as depicted in Table 1, suggest both the profound effect of excess N on herb diversity and the principle mechanism for such an effect. As already reported for this site [24], and consistent with findings of numerous other studies [41][42][43], chronic additions of N to WS3 have significantly (p < 0.05) decreased herb layer diversity. Although both richness and evenness contribute to species diversity, these results reveal that the N-mediated loss of diversity arose from decreased species evenness, which also declined significantly (p < 0.005), and not species richness, which showed no change (Table 1).…”

Section: Change In Herb Diversity Metrics Over Timesupporting

confidence: 92%

Excess Nitrogen in Temperate Forest Ecosystems Decreases Herbaceous Layer Diversity and Shifts Control from Soil to Canopy Structure

Gilliam

2019

Forests

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Research Highlights: Excess N from atmospheric deposition has been shown to decrease plant biodiversity of impacted forests, especially in its effects on herbaceous layer communities. This work demonstrates that one of the mechanisms of such response is in N-mediated changes in the response of herb communities to soil resources and light availability. Background and Objectives: Numerous studies in a variety of forest types have shown that excess N can cause loss of biodiversity of herb layer communities, which are typically responsive to spatial patterns of soil resource and light availability. The objectives of this study were to examine (1) gradients of temporal change in herb composition over a quarter century, and (2) spatial patterns of herb cover and diversity and how they are influenced by soil resources and canopy structure. Materials and Methods: This study used two watersheds (WS) at the Fernow Experimental Forest, West Virginia, USA: WS4 as an untreated reference and WS3 as treatment, receiving 35 kg N/ha/yr via aerial application. Herb cover and composition was measured in seven permanent plots/WS from 1991 to 2014. In 2011, soil moisture and several metrics of soil N availability were measured in each plot, along with measurement of several canopy structural variables. Backwards stepwise regression was used to determine relationships between herb cover/diversity and soil/canopy measurements. Results: Herb diversity and composition varied only slightly over time on reference WS4, in contrast to substantial change on N-treated WS3. Herb layer diversity appeared to respond to neither soil nor canopy variables on either watershed. Herb cover varied spatially with soil resources on WS4, whereas cover varied spatially with canopy structure on WS3. Conclusions: Results support work in many forest types that excess N can decrease plant diversity in impacted stands. Much of this response is likely related to N-mediated changes in the response of the herb layer to soil N and light availability.

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Section: Change In Herb Diversity Metrics Over Timesupporting

confidence: 92%

Excess Nitrogen in Temperate Forest Ecosystems Decreases Herbaceous Layer Diversity and Shifts Control from Soil to Canopy Structure

Gilliam

2019

Forests

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“…A study of soil microbial communities within the experimental plots sampled in the current study found that nutrient addition had distinct effects on different phylogenetic groups of species (Leff et al, ), and our current results suggest that this effect on endophytic fungi might depend on local site. This stands in contrast to the effects of nutrients on the host plant community diversity: elevated nutrient supply can cause local plant species extinctions (Borer, Seabloom, Mitchell, & Cronin, ; Harpole et al, ) as well as reduction in plant phylogenetic diversity (Roth, Kohli, Rihm, Amrhein, & Achermann, ).…”

Section: Discussionmentioning

confidence: 98%

Site‐specific responses of foliar fungal microbiomes to nutrient addition and herbivory at different spatial scales

Lumibao

Borer

Condon

et al. 2019

Ecology and Evolution

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The plant microbiome can affect host function in many ways and characterizing the ecological factors that shape endophytic (microbes living inside host plant tissues) community diversity is a key step in understanding the impacts of environmental change on these communities. Phylogenetic relatedness among members of a community offers a way of quantifying phylogenetic diversity of a community and can provide insight into the ecological factors that shape endophyte microbiomes. We examined the effects of experimental nutrient addition and herbivory exclusion on the phylogenetic diversity of foliar fungal endophyte communities of the grass species Andropogon gerardii at four sites in the Great Plains of the central USA. Using amplicon sequencing, we characterized the effects of fertilization and herbivory on fungal community phylogenetic diversity at spatial scales that spanned within‐host to between sites across the Great Plains. Despite increasing fungal diversity and richness, at larger spatial scales, fungal microbiomes were composed of taxa showing random phylogenetic associations. Phylogenetic diversity did not differ systematically when summed across increasing spatial scales from a few meters within plots to hundreds of kilometers among sites. We observed substantial shifts in composition across sites, demonstrating distinct but similarly diverse fungal communities were maintained within sites across the region. In contrast, at the scale of within leaves, fungal communities tended to be comprised of closely related taxa regardless of the environment, but there were no shifts in phylogenetic composition among communities. We also found that nutrient addition (fertilization) and herbivory have varying effects at different sites. These results suggest that the direction and magnitude of the outcomes of environmental modifications likely depend on the spatial scale considered, and can also be constrained by regional site differences in microbial diversity and composition.

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“…In spite of the diverse nature of these six measures, however, low values of plant diversity were consistently associated with high atmospheric N deposition (Roth et al 2015). The current study underpins that N deposition has similar effects on the different aspects of plant diversity.…”

Section: Discussionmentioning

confidence: 99%

Using change-point models to estimate empirical critical loads for nitrogen in mountain ecosystems

Roth

Kohli²,

Rihm

et al. 2017

Environmental Pollution

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To protect ecosystems and their services, the critical load concept has been implemented under the framework of the Convention on Long-range Transboundary Air Pollution (UNECE) to develop effects-oriented air pollution abatement strategies. Critical loads are thresholds below which damaging effects on sensitive habitats do not occur according to current knowledge. Here we use change-point models applied in a Bayesian context to overcome some of the difficulties when estimating empirical critical loads for nitrogen (N) from empirical data. We tested the method using simulated data with varying sample sizes, varying effects of confounding variables, and with varying negative effects of N deposition on species richness. The method was applied to the national-scale plant species richness data from mountain hay meadows and (sub)alpine scrubs sites in Switzerland. Seven confounding factors (elevation, inclination, precipitation, calcareous content, aspect as well as indicator values for humidity and light) were selected based on earlier studies examining numerous environmental factors to explain Swiss vascular plant diversity. The estimated critical load confirmed the existing empirical critical load of 5-15 kg N ha yr for (sub)alpine scrubs, while for mountain hay meadows the estimated critical load was at the lower end of the current empirical critical load range. Based on these results, we suggest to narrow down the critical load range for mountain hay meadows to 10-15 kg N ha yr.

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Nitrogen deposition and multi-dimensional plant diversity at the landscape scale

Cited by 28 publications

References 39 publications

Excess Nitrogen in Temperate Forest Ecosystems Decreases Herbaceous Layer Diversity and Shifts Control from Soil to Canopy Structure

Excess Nitrogen in Temperate Forest Ecosystems Decreases Herbaceous Layer Diversity and Shifts Control from Soil to Canopy Structure

Site‐specific responses of foliar fungal microbiomes to nutrient addition and herbivory at different spatial scales

Using change-point models to estimate empirical critical loads for nitrogen in mountain ecosystems

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