Showing papers by "Valerie T. Eviner published in 2021"
TL;DR: In this article, the authors show evidence from a field experiment demonstrating that warming and precipitation changes strengthen root controls over litter decomposition in a semi-arid grassland, suggesting that plant competition for water constraints the activities of saprophytic microbes.
Abstract: Plant roots are the primary source of soil organic carbon (C) and critically support the growth and activities of microbes in the rhizosphere. Climate change factors may, however, modify root-microbial interactions and impact C dynamics in the rhizosphere. Yet, the direction and magnitude of interactive climate change effects, as well as the underlying mechanisms, remain unclear. Here we show evidence from a field experiment demonstrating that warming and precipitation changes strengthen root controls over litter decomposition in a semi-arid grassland. While warming and precipitation reduction suppressed microbial decomposition of root litter regardless of the root presence, precipitation increase stimulated litter decomposition only in the absence of roots, suggesting that plant competition for water constraints the activities of saprophytic microbes. Root presence increased microbial biomass but reduced microbial activities such as respiration, C cycling enzymes and litter decomposition, indicating that roots exert differential effects on microbes through altering C or water availability. In addition, nitrogen (N) input significantly reduced microbial biomass and microbial activities (respiration). Together, these results showed that alterations in soil moisture induced by climate change drivers critically modulate root controls over microbial decomposition in soil. Our findings suggest that warming-enhanced plant water utilization, combined with N-induced suppression of microbes, may provide a unique mechanism through which moderate increases in precipitation, warming and N input interactively suppress microbial decomposition, thereby facilitating short-term soil C sequestration in the arid and semi-arid grasslands.
21 citations
TL;DR: In this article, the authors investigated how grazing by livestock, a common management practice, affects vernal pool plant diversity at multiple hierarchical spatial scales and concluded that grazing increases species richness and evenness by reducing competitive dominance.
Abstract: Disturbance often increases local-scale (α) diversity by suppressing dominant competitors However, widespread disturbances may also reduce biotic heterogeneity (β diversity) by making the identities and abundances of species more similar among patches Landscape-scale (γ) diversity may also decline if disturbance-sensitive species are lost California's vernal pool plant communities are species rich, in part because of two scales of β diversity: (1) within pools, as species composition changes with depth (referred to here as vertical β diversity), and (2) between pools, in response to dispersal limitation and variation in pool attributes (referred to here as horizontal β diversity) We asked how grazing by livestock, a common management practice, affects vernal pool plant diversity at multiple hierarchical spatial scales In terms of abundance-weighted diversity, grazing increased α both within local pool habitat zones and at the whole-pool scale, as well as γ at the pasture scale without influencing horizontal or vertical β diversity In terms of species richness, increases in α diversity within habitat zones and within whole pools led to small decreases in horizontal β diversity as species occupancy increased This had a dampened effect on species richness at the γ (pasture) scale without any loss of disturbance-sensitive species We conclude that grazing increases species richness and evenness (α) by reducing competitive dominance, without large disruptions to the critical spatial heterogeneity (β) that generates high landscape-level diversity (γ)
6 citations