Division of Biology, Imperial College London, Silwood Park Campus, Ascot, Berkshire SL5 7PY, UK.
Philos Trans R Soc Lond B Biol Sci. 2010 Jul 12;365(1549):2047-56. doi: 10.1098/rstb.2010.0028.
Grassland ecosystems cover vast areas of the Earth's surface and provide many ecosystem services including carbon (C) storage, biodiversity preservation and the production of livestock forage. Predicting the future delivery of these services is difficult, because widespread changes in atmospheric CO(2) concentration, climate and nitrogen (N) inputs are expected. We compiled published data from global change driver manipulation experiments and combined these with climate data to assess grassland biomass responses to CO(2) and N enrichment across a range of climates. CO(2) and N enrichment generally increased aboveground biomass (AGB) but effects of CO(2) enrichment were weaker than those of N. The response to N was also dependent on the amount of N added and rainfall, with a greater response in high precipitation regions. No relationship between response to CO(2) and climate was detected within our dataset, thus suggesting that other site characteristics, e.g. soils and plant community composition, are more important regulators of grassland responses to CO(2). A statistical model of AGB response to N was used in conjunction with projected N deposition data to estimate changes to future biomass stocks. This highlighted several potential hotspots (e.g. in some regions of China and India) of grassland AGB gain. Possible benefits for C sequestration and forage production in these regions may be offset by declines in plant biodiversity caused by these biomass gains, thus necessitating careful management if ecosystem service delivery is to be maximized. An approach such as ours, in which meta-analysis is combined with global scale model outputs to make large-scale predictions, may complement the results of dynamic global vegetation models, thus allowing us to form better predictions of biosphere responses to environmental change.
草原生态系统覆盖了地球表面的广大区域，提供了许多生态系统服务，包括碳（C）储存、生物多样性保护和牲畜饲料的生产。预测这些服务的未来提供情况具有挑战性，因为预计大气 CO2 浓度、气候和氮（N）输入会发生广泛变化。我们汇集了来自全球变化驱动因素操纵实验的已发表数据，并结合气候数据，评估了 CO2 和 N 富集对各种气候条件下草原生物量的影响。CO2 和 N 富集通常会增加地上生物量（AGB），但 CO2 富集的影响弱于 N 的影响。N 的响应还取决于添加的 N 量和降雨量，在高降雨量地区的响应更大。在我们的数据集内，未检测到 CO2 响应与气候之间的关系，因此表明其他站点特征（例如土壤和植物群落组成）是调节草原对 CO2 响应的更重要因素。使用 AGB 对 N 响应的统计模型结合预测的 N 沉积数据，估算未来生物量储量的变化。这突出了草原 AGB 增加的几个潜在热点（例如在中国和印度的一些地区）。这些地区的 C 固存和饲料生产可能会带来好处，但这些生物量增加可能会导致植物生物多样性下降，因此，如果要最大限度地提高生态系统服务的提供，就需要谨慎管理。我们采用的方法，即将荟萃分析与全球规模模型输出相结合以进行大规模预测，可能会补充动态全球植被模型的结果，从而使我们能够更好地预测生物圈对环境变化的响应。
