Yva Herion

Climate change threatens grassland biomass stability, but combined effects of climate variability and grassland management have rarely been analyzed, constraining our ability to predict management-dependent responses. In a large field experiment in Central Germany, we assessed temporal stability of aboveground biomass and potential underlying mechanisms (dominance, asynchrony, and averaging) in non-fertilized species-rich grasslands over nine years (2015–2023). The grasslands were exposed to ambient or simulated future climate following regional projections (higher temperature and altered seasonal precipitation pattern) and were managed by mowing or sheep grazing. While the future climate treatment showed little effects, high background climate variability increased biomass variability due to lower stabilization by asynchrony and averaging, which was more pronounced in meadows than in pastures. The lower biomass resistance to extreme summer droughts and the higher recovery afterwards in meadows compared to pastures was likely attributable to higher amounts of biomass removed by mowing than by grazing. However, stabilization by the diversity-associated averaging effect, which generally contributed most to biomass stabilization, was lower in pastures compared to meadows at peak biomass production in spring, due to declining species diversity with the lower biomass removal by grazing. Accordingly, we conclude that grassland management with low biomass removal can enhance biomass resistance to climate variability, but this may be offset in the long term by species loss and reduced stabilization through the diversity-associated averaging effect.

Climate change and agronomic management are major drivers altering Central European anthropogenic grassland ecosystems, but little is known about how these drivers interact in their effects on plant nutrient concentrations and ratios. This study was conducted in a climate change field experiment (higher temperature and changed seasonal precipitation pattern) in Central Germany with species‐rich non‐fertilized grasslands managed either by two times mowing (meadow) or three times sheep grazing (pasture) per year. In spring 2022, during peak plant growth, we collected leaves of five plant species per functional group (grasses, legumes, non‐legume forbs) as well as topsoil samples and determined plant leaf and plant available soil nutrient concentrations (N, P, K, Ca, Mg, S) and ratios. Plant functional groups differed in leaf concentrations of all studied nutrients with the exception of sulfur. The future climate treatment (compared to ambient climate) resulted in lower leaf N:P ratios across both management types and did not show any other effects on leaf or soil nutrients. Independent of the climate treatment, leaf and soil K concentrations were higher, while leaf Ca concentrations were lower in pastures compared to meadows. In addition, grasses had higher leaf N, legumes higher leaf S concentrations but lower leaf N:P ratios, and forbs lower leaf S concentrations in pastures than in meadows. While we found no interactive effect of climate and management and little effects of the rather moderate future climate treatment, the observed differences between pastures and meadows indicate that management, even at low intensity, modifies plant and soil nutrients in grasslands.

Climate and land‐use change are key drivers of global change. Full‐factorial field experiments in which both drivers are manipulated are essential to understand and predict their potentially interactive effects on the structure and functioning of grassland ecosystems. Here, we present 8 years of data on grassland dynamics from the Global Change Experimental Facility in Central Germany. On large experimental plots, temperature and seasonal patterns of precipitation are manipulated by superimposing regional climate model projections onto background climate variability. Climate manipulation is factorially crossed with agricultural land‐use scenarios, including intensively used meadows and extensively used (i.e., low‐intensity) meadows and pastures. Inter‐annual variation of background climate during our study years was high, including three of the driest years on record for our region. The effects of this temporal variability far exceeded the effects of the experimentally imposed climate change on plant species diversity and productivity, especially in the intensively used grasslands sown with only a few grass cultivars. These changes in productivity and diversity in response to alterations in climate were due to immigrant species replacing the target forage cultivars. This shift from forage cultivars to immigrant species may impose additional economic costs in terms of a decreasing forage value and the need for more frequent management measures. In contrast, the extensively used grasslands showed weaker responses to both experimentally manipulated future climate and inter‐annual climate variability, suggesting that these diverse grasslands are more resistant to climate change than intensively used, species‐poor grasslands. We therefore conclude that a lower management intensity of agricultural grasslands, associated with a higher plant diversity, can stabilize primary productivity under climate change.

Climate and land-use change are key drivers of global change. Full-factorial field experiments in which both drivers are manipulated are essential to understand and predict their potentially interactive effects on the structure and functioning of grassland ecosystems. Here, we present eight years of data on grassland dynamics from the Global Change Experimental Facility (GCEF) in Central Germany. On large experimental plots, temperature and seasonal patterns of precipitation are manipulated by superimposing regional climate model projections onto background climate variability. Climate manipulation is factorially crossed with agricultural land-use scenarios, including intensively used meadows and extensively used (i.e. low-intensity) meadows and pastures. Inter-annual variation of background climate during our study years was high, including three of the driest years on record for our region. The effects of this temporal variability far exceeded the effects of the experimentally imposed climate change on plant species diversity and productivity, especially in the intensively used, species-poor grasslands. These changes in productivity and diversity in response to alterations in climate were due to immigrant species replacing the target forage cultivars. This shift from forage cultivars to immigrant species may impose additional economic costs in terms of a decreasing fodder value and the need for more frequent management measures. In contrast, the extensively used, species-rich grasslands showed weaker responses to both experimentally manipulated future climate and inter-annual climate variability, suggesting that these diverse grasslands are more resistant to climate change than intensively used, species-poor grasslands. We therefore conclude that an extensive management of agricultural grasslands, together with other measures to increase species diversity, can stabilize primary productivity under climate change.