Agricultural influences on the magnitude of stream metabolism in humid tropical headwater streams
Agricultural influences on the magnitude of stream metabolism in humid tropical headwater streams
复制标题
农业对潮湿热带源头河流代谢程度的影响
作者：
A. Ortega;A. Fremier;C. Orr
溪流中有机碳的产生和呼吸（溪流代谢）是一个基本的生态系统过程。在潮湿的热带源头，随着森林向农业转变，河流新陈代谢的程度发生了多大程度的变化，人们知之甚少。我们测量了森林-农业边界排水源头的全流代谢，以研究土地利用突然转变地区的代谢率以及残余河岸植被的作用。我们使用线性混合模型来检验以下假设：农业地区的总初级生产（GPP）和生态系统呼吸（ER）将分别由于较高的光利用率和养分浓度而较高。我们发现农业河流河段的 GPP 增加了 257%，ER 增加了 30%。 GPP受光驱动，ER主要受GPP控制。这些结果凸显了光对上游森林覆盖率很大的农业溪流的压倒性影响。我们的研究结果表明，高河岸冠层覆盖率（~90%）对于支持与农业区森林类似的河流代谢率是必要的。这项研究增加了我们对农业引起的生物群落内新陈代谢变化的理解，以及森林生物群落和热带溪流在全球碳循环中的作用之间的潜在相似性。
The production and respiration of organic carbon in streams (stream metabolism) is a fundamental ecosystem process. The extent to which the magnitude of stream metabolism changes with forest conversion to agriculture in humid tropical headwaters is poorly understood. We measured whole-stream metabolism in headwaters draining forest-agricultural boundaries to investigate metabolic rates in areas with abrupt land-use transitions and the role of remnant riparian vegetation. We used linear mixed models to test the hypotheses that gross primary production (GPP) and ecosystem respiration (ER) would be higher in agricultural areas due to higher light availability and nutrient concentrations, respectively. We found a 257% increase in GPP and 30% increase in ER in agricultural stream reaches. GPP was driven by light and ER was mainly controlled by GPP. These results highlight the overriding influence of light in agricultural streams with large fractions of upstream forest cover. Our findings suggest that high riparian canopy cover (~90%) is necessary to support stream metabolic rates similar to forests in agricultural areas. This study adds to our understanding of the within-biome variation of metabolism resulting from agriculture, and the potential similarities between forested biomes and the role of tropical streams in the global carbon cycle.