Grazing and Spatial Heterogeneity: Implications for Grassland Structure and Function

Grasslands cover around 30% of the Earth’s terrestrial surface and provide important ecosystem services. On the other hand, grasslands are among the most endangered ecosystems, threatened by land-use change, mainly through agricultural intensification or abandonment, and ongoing climatic changes, such as warming and drought. The principal aim of this book is to give an overview of current knowledge and future challenges for ecological studies on grasslands and to provide new perspectives for the management and conservation of grassland ecosystems. The first chapter presents some current threats to grasslands by reviewing the influence of land-use and climate change on the integrity of grassland ecosystems through changes in plant species composition and biodiversity (Chapter 1). While aboveground patterns and processes in grasslands are relatively well-known, the importance of belowground components in shaping grassland ecosystems is not well-understood. This is despite recognition that most of the grassland biomass and biodiversity is belowground, and that soil communities provide key ecosystem functions. Chapter 2 readdresses the importance of soil organisms by synthetizing their effects on grassland production and diversity, illustrated by a simplified soil food web with antagonist and mutualistic pathways. Soil microbial communities are particularly important for grassland functioning and need to be taken into account in management practices. As such, Chapter 3 highlights the importance of the seasonal variability of soil microbial communities and gives perspectives for bettering the management of disturbed grasslands. In addition to temporal variation, spatial variability should also be considered in grassland management. Chapter 4 presents a conceptual toolkit that accounts for spatial and temporal variability to facilitate restoration planning and management. Grazing is one of the most common practices in grassland management, with positive or negative effects on biodiversity and ecosystem functioning, depending on intensity and frequency. Chapter 5 investigates how grazing components (i.e. defoliation, trampling, animal excretions) affect spatial heterogeneity and as such, affect the functioning of grassland ecosystems and the services they provide. Grazing can be also used as a tool to restore degraded ecosystems and Chapter 6 shows how grazing, as well as other management practices, affect plant diversity and biomass production in a unique long-term restoration experiment in China. In a historic perspective, over the past two centuries, grasslands have been transformed globally by conversion to intense agricultural use, while extensively low-intensity grazed grasslands are disappearing. The ongoing effects of climate change are an additional threat to these endangered ecosystems as shown in Chapter 7. Climate change impacts are especially important in high elevation ecosystems, which are disproportionally affected, and Chapter 8 and 9 explore the influences of land-use and climate change on mountain and alpine grasslands. Both of these chapters focus explicitly on changes in plant functional group composition, which are key drivers of ecosystem properties and functioning. In this light, Chapter 10 gives an overview of the role of the largely understudied functional group of bryophytes by showing how this group contributes to the biodiversity of grasslands and constitutes a key group in the functioning of grassland ecosystems.