Initial success of native grasses is contingent on multiple interactions among exotic grass competition, temporal priority, rainfall and site effects

Ecological communities are increasingly being recognized as the products of contemporary drivers and historical legacies that are both biotic and abiotic. In an attempt to unravel multiple layers of ecological contingency, we manipulated (i) competition with exotic annual grasses, (ii) the timing of this competition (temporal priority in arrival/seeding times) and (iii) watering (simulated rainfall) in a restoration-style planting of native perennial grasses. In addition, we replicated this experiment simultaneously at three sites in north-central California. Native perennial grasses had 73–99 % less cover when planted with exotic annuals than when planted alone, but this reduction was greatly ameliorated by planting the natives 2 weeks prior to the exotics. In a drought year, irrigation significantly reduced benefits of early planting so that these benefits resembled those observed in a non-drought year. There were significant differences across the three sites (site effects and interactions) in (i) overall native cover, (ii) the response of natives to competition, (iii) the strength of the temporal priority effect and (iv) the degree to which supplemental watering reduced priority effects. These results reveal the strong multi-layered contingency that underlies even relatively simple communities

Species richness effects on grassland recovery from drought depend on community productivity in a multisite experiment

Biodiversity can buffer ecosystem functioning against extreme climatic events, but few experiments have explicitly tested this. Here, we present the first multisite biodiversity × drought manipulation experiment to examine drought resistance and recovery at five temperate and Mediterranean grassland sites. Aboveground biomass production declined by 30% due to experimental drought (standardised local extremity by rainfall exclusion for 72–98 consecutive days). Species richness did not affect resistance but promoted recovery. Recovery was only positively affected by species richness in low-productive communities, with most diverse communities even showing overcompensation. This positive diversity effect could be linked to asynchrony of species responses. Our results suggest that a more context-dependent view considering the nature of the climatic disturbance as well as the productivity of the studied system will help identify under which circumstances biodiversity promotes drought resistance or recovery. Stability of biomass production can generally be expected to decrease with biodiversity loss and climate change. © 2017 John Wiley & Sons Ltd/CNR

Multiple cropping systems as drivers for providing multiple ecosystem services: from concepts to design

Provisioning services, such as the production of food, feed, and fiber, have always been the main focus of agriculture. Since the 1950s, intensive cropping systems based on the cultivation of a single crop or a single cultivar, in simplified rotations or monocultures, and relying on extensive use of agrochemical inputs have been preferred to more diverse, self-sustaining cropping systems, regardless of the environmental consequences. However, there is increasing evidence that such intensive agroecosystems have led to a decline in biodiversity as well as threatening the environment and have damaged a number of ecosystem services such as the biogeochemical nutrient cycles and the regulation of climate and water quality. Consequently, the current challenge facing agriculture is to ensure the future of food production while reducing the use of inputs and limiting environmental impacts and the loss of biodiversity. Here, we review examples of multiple cropping systems that aim to use biotic interactions to reduce chemical inputs and provide more ecosystem services than just provisioning. Our main findings are the identification of underlying ecological processes and management strategies related to the provision of pairs of ecosystem services namely food production and a regulation service. We also found gaps between ecological knowledge and the constraints of agricultural practices in taking account of the interactions and possible trade-offs between multiple ecosystem services as well as socioeconomic constraints. We present guidelines for the design of multiple cropping systems combining ecological, agricultural, and genetic concepts and approaches