Community level offset of rain use- and transpiration efficiency for a heavily grazed ecosystem in inner Mongolia grassland.
Community level offset of rain use- and transpiration efficiency for a heavily grazed ecosystem in inner Mongolia grassland.
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内蒙古草原重度放牧生态系统降雨利用和蒸腾效率的群落水平抵消
DOI：
10.1371/journal.pone.0074841
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发表时间：
2013
期刊：
影响因子：
3.7
通讯作者：
Yang HJ
中科院分区：
文献类型：
--
作者：
Gao YZ;Giese M;Gao Q;Brueck H;Sheng LX;Yang HJ
水分利用效率(WUE)是评价生态系统对水分胁迫适应性的重要指标。由于缺乏蒸腾数据，雨水利用效率(RUE)通常被用作WUE的替代指标。此外，基于地上第一性生产力(RUEANPP)的RUEANPP被用来评估整个植物的水分利用，因为根产量数据也经常丢失。然而，关于RUE是否是阐明蒸腾效率(TE)的可靠参数，以及RUEANPP是否适合作为整个植物基础的RUE的替代物，还存在争议。试验在内蒙古草原的三个不同管理地点进行：一个自1979年起围起来的地点(UG79)，一个冬季放牧地点(WG)和一个重度放牧地点(HG)。根据总净初级生产力(RUENPP)计算，HG立地具有一致最低的RUEANPP和RUE。RUEANPP在UG79和WG站点是一个相对较好的代理，但对于HG站点则不太可靠。同样，在UG79和WG，RUEANPP是基于地上净第一性生产力(TEANPP)的蒸腾效率的良好预测因子，而对于HG则不是。然而，如果考虑总的净第一性生产力，RUENPP是基于所有立地的总的净第一性生产力(TENPP)的蒸腾效率的良好预测因子。尽管我们的测量表明，在重度放牧下，植物蒸腾作用降低，RUE随之降低，但生产力相对补偿了较高的TE。在水分有限的条件下，RUE和TE之间的这种偏移量甚至会增加，当计入地下净初级生产力(BNNP)时，这种偏移量更加明显。这些发现表明，在研究更密集利用草地的水分利用效率时，应考虑BNPP。对整个植物视角和“真实”水分利用效率的考虑将部分修正我们对系统性能的看法，因此可能会影响对生态系统碳固存和恢复潜力的讨论。
Water use efficiency (WUE) is a key indicator to assess ecosystem adaptation to water stress. Rain use efficiency (RUE) is usually used as a proxy for WUE due to lack of transpiration data. Furthermore, RUE based on aboveground primary productivity (RUEANPP) is used to evaluate whole plant water use because root production data is often missing as well. However, it is controversial as to whether RUE is a reliable parameter to elucidate transpiration efficiency (TE), and whether RUEANPP is a suitable proxy for RUE of the whole plant basis. The experiment was conducted at three differently managed sites in the Inner Mongolia steppe: a site fenced since 1979 (UG79), a winter grazing site (WG) and a heavily grazed site (HG). Site HG had consistent lowest RUEANPP and RUE based on total net primary productivity (RUENPP). RUEANPP is a relatively good proxy at sites UG79 and WG, but less reliable for site HG. Similarly, RUEANPP is good predictor of transpiration efficiency based on aboveground net primary productivity (TEANPP) at sites UG79 and WG but not for site HG. However, if total net primary productivity is considered, RUENPP is good predictor of transpiration efficiency based on total net primary productivity (TENPP) for all sites. Although our measurements indicate decreased plant transpiration and consequentially decreasing RUE under heavy grazing, productivity was relatively compensated for with a higher TE. This offset between RUE and TE was even enhanced under water limited conditions and more evident when belowground net primary productivity (BNNP) was included. These findings suggest that BNPP should be considered when studies fucus on WUE of more intensively used grasslands. The consideration of the whole plant perspective and “real” WUE would partially revise our picture of system performance and therefore might affect the discussion on the C-sequestration and resilience potential of ecosystems.
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