Productivity responses to altered rainfall patterns in a C4-dominated grassland
Productivity responses to altered rainfall patterns in a C4-dominated grassland
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DOI：
10.1007/s00442-003-1331-3
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发表时间：
2003-10-01
期刊：
影响因子：
2.7
通讯作者：
Collins, SL
中科院分区：
文献类型：
--
作者：
Fay, PA;Carlisle, JD;Collins, SL
降雨量的变化是全球草原生态系统结构和功能的关键驱动因素。全球气候模型预测的美国中部降雨模式的变化预计将导致土壤水分可获得性降低且变化越来越大，这可能会影响原生大平原草原的净初级生产力和植物物种组成。我们通过实验改变了生长季降雨输入的时间和数量，与堪萨斯州东北部原生Tallgras草原生态系统的环境降雨制度相比，延长了50%的降雨间隔，减少了30%的降雨量，或两者兼而有之。在三个生长季节中，在总降雨量不变的情况下，由于降雨时间的改变而导致的降雨变异性增加，导致土壤含水量(0-30 cm深度)更低和更可变，地上净第一性生产力(ANPP)下降10%，根冠比增加，在土壤表面30 cm处的冠层光子通量密度更大。总ANPP下降主要是由于暖季型次生C-4牧草的生长、生物量和开花减少所致，而C-4暖季型牧草生产力相对较低。一般而言，植被对土壤水分变异性增加的响应至少等于在不改变降雨输入时间的情况下将降雨量减少30%所造成的响应。ANPP的降低很可能是由于土壤水分亏缺对根系活力、植物水分状况和光合作用的直接影响。降雨制度的变化很可能是该草原气候变化情景的一个重要因素，与其他气候变化因素相互作用的性质仍然是预测生态系统对气候变化反应的一个重大挑战。
Rainfall variability is a key driver of ecosystem structure and function in grasslands worldwide. Changes in rainfall patterns predicted by global climate models for the central United States are expected to cause lower and increasingly variable soil water availability, which may impact net primary production and plant species composition in native Great Plains grasslands. We experimentally altered the timing and quantity of growing season rainfall inputs by lengthening inter-rainfall dry intervals by 50%, reducing rainfall quantities by 30%, or both, compared to the ambient rainfall regime in a native tallgrass prairie ecosystem in northeastern Kansas. Over three growing seasons, increased rainfall variability caused by altered rainfall timing with no change in total rainfall quantity led to lower and more variable soil water content (0-30 cm depth), a similar to10% reduction in aboveground net primary productivity (ANPP), increased root to shoot ratios, and greater canopy photon flux density at 30 cm above the soil surface. Lower total ANPP primarily resulted from reduced growth, biomass and flowering of subdominant warm-season C-4 grasses while productivity of the dominant C-4 grass Andropogon gerardii was relatively unresponsive. In general, vegetation responses to increased soil water content variability were at least equal to those caused by imposing a 30% reduction in rainfall quantity without altering the timing of rainfall inputs. Reduced ANPP most likely resulted from direct effects of soil moisture deficits on root activity, plant water status, and photosynthesis. Altered rainfall regimes are likely to be an important element of climate change scenarios in this grassland, and the nature of interactions with other climate change elements remains a significant challenge for predicting ecosystem responses to climate change.