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Growing evidence indicates that ecosystem processes may be differentially sensitive to dry versus wet years, and that current understanding of how precipitation affects ecosystem processes may not be predictive of responses to extremes. In an experiment within a mesic grassland, we addressed this uncertainty by assessing responses of two key carbon exchange processes—aboveground net primary production...
Both the dominance and the mass ratio hypotheses predict that plant internal nutrient cycling in ecosystems is determined by the dominant species within plant communities. We tested this hypothesis under conditions of extreme drought by assessing plant nutrient (N, P and K) uptake and resorption in response to experimentally imposed precipitation reductions in two semiarid grasslands of northern China...
While interspecific competition is prevalent in natural systems, we do not yet understand how it can influence an individual’s phenotype within its lifetime and how this might affect performance. Morphology and swimming performance are two important fitness-related traits in fishes. Both traits are essential in acquiring and defending resources as well as avoiding predation. Here, we examined if interspecific...
Extreme heat waves and drought are predicted to increase in frequency and magnitude with climate change. These extreme events often co-occur, making it difficult to separate their direct and indirect effects on important ecophysiological and carbon cycling processes such as photosynthesis. Here, we assessed the independent and interactive effects of experimental heat waves and drought on photosynthesis...
Resource availability may influence invertebrate communities, with important consequences for ecosystem function, such as biomass production. We assessed: (1) the effects of experimental soil nutrient additions on invertebrate abundances and feeding rates and (2) the resultant changes in the effects of invertebrates on aboveground plant biomass at three grassland sites spanning the North American...
Timing of precipitation is equally important as amount for determining ecosystem function, especially aboveground net primary productivity (ANPP), in a number of ecosystems. In tallgrass prairie of the Central Plains of North America, grass flowering stalks of dominant C4 grasses, such as Andropogon gerardii, can account for more than 70 % of ANPP, or almost none of it, as the number of flowering...
Although climate models forecast warmer temperatures with a high degree of certainty, precipitation is the primary driver of aboveground net primary production (ANPP) in most grasslands. Conversely, variations in temperature seldom are related to patterns of ANPP. Thus forecasting responses to warming is a challenge, and raises the question: how sensitive will grassland ANPP be to warming?...
Factors influencing vital demographic rates and population dynamics can vary across phases of population growth. We studied factors influencing survival and fidelity of peregrine falcons in south Scotland—north England at two stages of population growth: when the population was recovering from pesticide-related declines and density was low, and when it had largely recovered from pesticide effects...
Many global change drivers chronically alter resource availability in terrestrial ecosystems. Such resource alterations are known to affect aboveground net primary production (ANPP) in the short term; however, it is unknown if patterns of response change through time. We examined the magnitude, direction, and pattern of ANPP responses to a wide range of global change drivers by compiling 73 datasets...
Terrestrial ecosystems often vary dramatically in their responses to drought, but the reasons for this are unclear. With climate change forecasts for more frequent and extensive drought in the future, a more complete understanding of the mechanisms that determine differential ecosystem sensitivity to drought is needed. In 2012, the Central US experienced the fourth largest drought in a century, with...
Large herbivore grazing is a widespread disturbance in mesic savanna grasslands which increases herbaceous plant community richness and diversity. However, humans are modifying the impacts of grazing on these ecosystems by removing grazers. A more general understanding of how grazer loss will impact these ecosystems is hampered by differences in the diversity of large herbivore assemblages among savanna...
Fleshy-fruited plants depend fundamentally on interactions with frugivores for effective seed dispersal. Recent models of frugivory within spatially explicit networks make two general predictions regarding these interactions: rate of fruit removal increases (i.e., is facilitated) as densities of conspecific neighborhood fruits increase, and fruit removal rate varies positively with frugivore abundance...
Climate change has the potential to alter the genetic diversity of plant populations with consequences for community dynamics and ecosystem processes. Recent research focused on changes in climatic means has found evidence of decreased precipitation amounts reducing genetic diversity. However, increased variability in climatic regimes is also predicted with climate change, but the effects of this...
To improve the understanding of how native plant diversity influences invasion, we examined how population and community diversity may directly and indirectly be related to invasion in a natural field setting. Due to the large impact of the dominant C4 grass species (Andropogon gerardii) on invasion resistance of tallgrass prairie, we hypothesized that genetic diversity and associated traits within...
During the first few years of elevated atmospheric [CO2] treatment at the Nevada Desert FACE Facility, photosynthetic downregulation was observed in desert shrubs grown under elevated [CO2], especially under relatively wet environmental conditions. Nonetheless, those plants maintained increased Asat (photosynthetic performance at saturating light and treatment [CO2]) under wet conditions, but to...
Mesic grasslands in North America and South Africa share many structural attributes, but less is known of their functional similarities. We assessed the control of a key ecosystem process, aboveground net primary production (ANPP), by interannual variation in precipitation amount and pattern via analysis of data sets (15- and 24-year periods) from long-term research programs on each continent. Both...
We investigated the relationships between foliar stable carbon isotope discrimination (Δ), % foliar N, and predawn water potentials (ψpd) and midday stomatal conductance (gs) of Larrea tridentata across five Mojave Desert soils with different age-specific surface and sub-surface horizon development and soil hydrologies. We wished to elucidate how this long-lived evergreen shrub optimizes leaf-level...
Annual and short-lived perennial plant performance during wet years is important for long-term persistence in the Mojave Desert. Additionally, the effects of elevated CO2 on desert plants may be relatively greater during years of high resource availability compared to dry years. Therefore, during an El Niño year at the Nevada Desert FACE Facility (a whole-ecosystem CO2 manipulation), we characterized...
AbstractIn tallgrass prairie, plant species interactions regulated by their associated mycorrhizal fungi may be important forces that influence species coexistence and community structure; however, the mechanisms and magnitude of these interactions remain unknown. The objective of this study was to determine how interspecific competition, mycorrhizal symbiosis, and their interactions influence plant...
Abstract We used data from a 15-year experiment in a C4-dominated grassland to address the effects of community structure (i.e., plant species richness, dominance) and disturbance on invasibility, as measured by abundance and richness of exotic species. Our specific objectives were to assess the temporal and spatial patterns of exotic plant species in a native grassland in Kansas (USA) and to determine...
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