Contingent productivity responses to more extreme rainfall regimes across a grassland biome
Contingent productivity responses to more extreme rainfall regimes across a grassland biome
复制标题
DOI：
10.1111/j.1365-2486.2009.01961.x
复制
发表时间：
2009-12-01
影响因子：
11.6
通讯作者：
Knapp, Alan K.
中科院分区：
文献类型：
--
作者：
Heisler-White, Jana L.;Blair, John M.;Knapp, Alan K.
气候模型预测，经验证据证实，更多的极端降水制度正在发生与大气温度上升。这些更极端的降雨模式的特点是事件规模增加，季节内干旱期较长，代表了新的气候条件，其对不同生态系统类型的影响在很大程度上是未知的。在这里，我们提出了一个实验中，更极端的降雨模式施加在三个原生草原网站在北美，美国中部平原地区的结果。沿着这600公里的降水生产力梯度，有较强的敏感性，温带草原更极端的生长季降雨制度，地上净初级生产力（ANPP）的响应取决于不同类型的草地的平均土壤水分水平。在中端的梯度（tallgrass草原），较长的干燥间隔事件导致延长期低于平均土壤含水量，增加植物水分胁迫和减少ANPP的18%。相反的反应发生在干端（半干旱草原），在那里转移到更少，但更大的，事件增加期间高于平均水平的土壤含水量，减少季节性植物水分胁迫，并导致在30%的增加ANPP。在一个中间混合草草原网站与高植物物种丰富度，ANPP是最敏感的极端降雨制度（增加70%）。这些结果突出了预测陆地生态系统将如何对预测的新气候条件作出反应的固有复杂性，以及从单点实验中延伸到整个生物群落的推论的困难。即使年降水量没有变化，在一个相对统一的地文区域的ANPP响应不同的幅度和方向，在响应降雨事件的大小/频率的季节变化。
Climate models predict, and empirical evidence confirms, that more extreme precipitation regimes are occurring in tandem with warmer atmospheric temperatures. These more extreme rainfall patterns are characterized by increased event size separated by longer within season drought periods and represent novel climatic conditions whose consequences for different ecosystem types are largely unknown. Here, we present results from an experiment in which more extreme rainfall patterns were imposed in three native grassland sites in the Central Plains Region of North America, USA. Along this 600 km precipitation-productivity gradient, there was strong sensitivity of temperate grasslands to more extreme growing season rainfall regimes, with responses of aboveground net primary productivity (ANPP) contingent on mean soil water levels for different grassland types. At the mesic end of the gradient (tallgrass prairie), longer dry intervals between events led to extended periods of below-average soil water content, increased plant water stress and reduced ANPP by 18%. The opposite response occurred at the dry end (semiarid steppe), where a shift to fewer, but larger, events increased periods of above-average soil water content, reduced seasonal plant water stress and resulted in a 30% increase in ANPP. At an intermediate mixed grass prairie site with high plant species richness, ANPP was most sensitive to more extreme rainfall regimes (70% increase). These results highlight the inherent complexity in predicting how terrestrial ecosystems will respond to forecast novel climate conditions as well as the difficulties in extending inferences from single site experiments across biomes. Even with no change in annual precipitation amount, ANPP responses in a relatively uniform physiographic region differed in both magnitude and direction in response to within season changes in rainfall event size/frequency.