Search

Community stability is a fundamental factor sustaining ecosystem functioning and is affected by species richness and species evenness. The Arctic is warming more rapidly than other biomes, and cryptogam plant species (specifically lichens and bryophytes in this study) are major contributors to tundra biodiversity and productivity. However, to our knowledge, the impacts of warming on cryptogam community stability and the underlying mechanisms have not been investigated. We conducted a 13‐year summer warming experiment in mesic birch hummock tundra vegetation near Daring Lake in the continental interior of low Arctic Canada and recorded patterns of cryptogam species abundance in several different growing seasons. Warming decreased the stability of total community abundance, had no effects on species richness, but increased species evenness and species synchrony. Structural equation model analyses indicated that higher species richness was the principal factor associated with the stronger community abundance stability in the control plots and that this effect was driven primarily by a negative correlation with species synchrony. By contrast, higher species evenness was the principal factor associated with the weakened community abundance stability in the warming plots, and this effect was driven primarily by a positive correlation with species synchrony. Our study suggests that climate warming could reduce cryptogam plant community stability in low Arctic tundra and, therefore, decrease important ecosystem services, including carbon storage and food availability to caribou in northern regions. [ABSTRACT FROM AUTHOR]

Biodiversity can stabilise productivity through different mechanisms, such as asynchronous species responses to environmental variability and species stability. Global changes, like intensified drought, could negatively affect species richness, species asynchrony and species stability, but it is unclear how changes in these mechanisms will affect the stability of above‐ground primary productivity (ANPP) across ecosystems.We studied the effects of a 4‐year extreme drought on ANPP stability and the underlying mechanisms (species richness, species asynchrony and species stability) across six grasslands in Northern China. We also assessed the relative importance of these mechanisms in determining ANPP stability under extreme drought.We found that extreme drought decreased ANPP stability, species richness, species asynchrony and species stability across the six grasslands. However, structural equation modelling revealed that species asynchrony, not species richness or species stability, was the most important mechanism promoting stability of ANPP, regardless of drought across the six grasslands.Synthesis. Our results suggest that species asynchrony, not species richness and species stability, consistently buffers ecosystem stability against extreme drought across and within grasslands spanning a broad precipitation gradient. Thus, species asynchrony may be a more general mechanism for promoting stability of ANPP in grasslands in the face of intensified drought. [ABSTRACT FROM AUTHOR]

Random species loss has been shown experimentally to reduce ecosystem function, sometimes more than other anthropogenic environmental changes. Yet, controversy surrounds the importance of this finding for natural systems where species loss is non‐random.We compiled data from 16 multi‐year experiments located at a single native tallgrass prairie site. These experiments included responses to 11 anthropogenic environmental changes, as well as non‐random biodiversity loss either the removal of uncommon/rare plant species or the most common (dominant) species.As predicted by the mass ratio hypothesis, loss of a dominant species had large impacts on productivity that were comparable to other anthropogenic drivers. In contrast, the loss of uncommon/rare species had small effects on productivity despite having the largest effects on species richness.The anthropogenic drivers that had the largest effects on productivity nitrogen, irrigation, and fire experienced not only loss of species but also significant changes in the abundance and identity of dominant species.Synthesis. These results suggest that mass ratio effects, rather than species loss per se, are an important determinant of ecosystem function with environmental change. [ABSTRACT FROM AUTHOR]

Stability is an important property of ecological systems, many of which are experiencing increasing levels of anthropogenic environmental changes. However, how these environmental changes influence ecosystem stability remains poorly understood., We conducted an 8-year field experiment in a semi-arid natural grassland to explore the effects of two common environmental changes, precipitation and nitrogen enrichment, on the temporal stability of plant above-ground biomass. A split-plot design, with precipitation as the main plot factor and nitrogen as the subplot factor, was used. Temporal stability was related to potential explanatory abiotic and biotic variables using regressions and structural equation modelling., Increase in growing season precipitation enhanced plant species richness and promoted temporal stability of plant above-ground biomass. Nitrogen fertilization, however, reduced both plant species richness and temporal stability of plant above-ground biomass. Contrary to expectations, species richness was not an important driver of stability. Instead, community temporal stability was mainly driven by water and nitrogen availability that modulated the degree of species asynchrony and, to a lesser extent, by the stability of dominant plant species., Synthesis. Our results highlight the importance of limiting resources for regulating community biomass stability and suggest that the projected increase in growing season precipitation may potentially offset negative effects of increased atmospheric nitrogen deposition on species diversity and community stability in semi-arid grasslands. [ABSTRACT FROM AUTHOR]

Humans are both intentionally (fertilization) and unintentionally (atmospheric nutrient deposition) adding nutrients worldwide. Increasing availability of biologically reactive nitrogen (N) is one of the major drivers of plant species loss. It remains unclear, however, whether plant diversity will be equally reduced by inputs of reactive N coming from either small and frequent N deposition events or large and infrequent N fertilization events. By independently manipulating the rate and frequency of reactive N inputs, our study teases apart these potentially contrasting effects. Plant species richness decreased more quickly at high rates and at low frequency of N addition, which suggests that previous fertilization studies have likely over-estimated the effects of N deposition on plant species loss. N-induced species loss resulted from both acidification and ammonium toxicity. Further study of small and frequent N additions will be necessary to project future rates of plant species loss under increasing aerial N deposition. [ABSTRACT FROM AUTHOR]