Abstract Karst landforms account for 10% of the Earths land surface, and it is well-known that water is a limiting factor for karst ecosystems because numerous underground fractures and conduits induce rapid drainage. Therefore, an understanding of ecosystem water consumptions (evapotranspiration) and environmental controls is particularly important for land management on karst landforms. This study compared the actual evapotranspiration ( AET) characteristics and analyzed the controls of three agroforestry ecosystems by field observations using a refitted ventilated-chamber, thermal dissipation probes and micro-lysimeters in a subtropical humid karst catchment from 12th March 2015 to 26th May 2016. Results show that: 1) the diurnal transpiration curves of trees plateau at noon with low fluctuations at a high level, while evapotranspiration curves of grass and crop ecosystems present single peaks; 2) AET of the forest-grass mixed ecosystem (7.64 ± 5.75 mm·day −1 ) was significantly higher than crop (4.24 ± 3.35 mm·day −1 ) and grass ecosystems (5.78 ± 3.53 mm·day −1 ); 3) AET of grass and crop ecosystems were most sensitive to temperature, while the forest-grass mixed ecosystem was more sensitive to leaf area index ( LAI ) than other factors; 4) AET of the forest-grass mixed ecosystem was more sensitive to deep soil moisture (>30 cm), while grass and crop ecosystems were more sensitive to shallow soil moisture (10 cm and 20 cm). This study suggests that soil water content was not key limit factors to AET in humid karst landscapes . However, LAI , which can be controlled by land management, heavily influenced AET rates and E / AET ( E , evaporation) ratio through changing water demand.

中文翻译：

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亚热带湿润喀斯特地区三种农林生态系统的蒸散特征和环境控制比较

摘要 喀斯特地貌占地球陆地表面的10%，众所周知，水是喀斯特生态系统的限制因素，因为地下裂缝和管道众多，导致快速排水。因此，了解生态系统耗水量（蒸散）和环境控制对于岩溶地貌的土地管理尤为重要。本研究比较了 2015 年 3 月 12 日至 2016 年 5 月 26 日在亚热带潮湿喀斯特集水区的实际蒸散量 (AET) 特征，并通过使用改装通风室、热耗散探头和微蒸渗仪的实地观察分析了三个农林业生态系统的控制情况。结果表明： 1) 中午树木高原的日蒸腾曲线低波动高水平，而草地和作物生态系统的蒸散曲线呈现单峰；2）林草混合生态系统的AET（7.64±5.75 mm·day -1 ）显着高于作物（4.24±3.35 mm·day -1 ）和草地生态系统（5.78±3.53 mm·day -1 ）；3）草和作物生态系统的AET对温度最敏感，而林草混合生态系统对叶面积指数（LAI）的敏感性高于其他因素；4）林草混合生态系统的AET对深层土壤水分（>30 cm）更敏感，而草和作物生态系统对浅层土壤水分（10 cm和20 cm）更敏感。这项研究表明，土壤含水量不是潮湿喀斯特景观中AET的关键限制因素。然而，土地管理可以控制的 LAI 严重影响了 AET 率和 E / AET ( E ,