title: Water use efficiency in a primary subtropical evergreen forest in Southwest China.
abstract: We calculated water use efficiency (WUE) using measures of gross primary production (GPP) and evapotranspiration (ET) from five years of continuous eddy covariance measurements (2009-2013) obtained over a primary subtropical evergreen broadleaved forest in southwestern China. Annual mean WUE exhibited a decreasing trend from 2009 to 2013, varying from ~2.28 to 2.68 g C kg H2O-1. The multiyear average WUE was 2.48 ± 0.17 (mean ± standard deviation) g C kg H2O-1. WUE increased greatly in the driest year (2009), due to a larger decline in ET than in GPP. At the diurnal scale, WUE in the wet season reached 5.1 g C kg H2O-1in the early morning and 4.6 g C kg H2O-1in the evening. WUE in the dry season reached 3.1 g C kg H2O-1in the early morning and 2.7 g C kg H2O-1in the evening. During the leaf emergence stage, the variation of WUE could be suitably explained by water-related variables (relative humidity (RH), soil water content at 100 cm (SWC_100)), solar radiation and the green index (Sgreen). These results revealed large variation in WUE at different time scales, highlighting the importance of individual site characteristics.
authors.affiliation: Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun 666303, China.|Global Change Ecology Group, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun 666303, China.
authors.forename: Qing-Hai
authors.initials: QH
authors.lastname: Song
authors.affiliation: Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun 666303, China.|Global Change Ecology Group, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun 666303, China.|University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Xue-Hai
authors.initials: XH
authors.lastname: Fei
authors.affiliation: Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun 666303, China.|Global Change Ecology Group, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun 666303, China.|Ailaoshan Station for Subtropical Forest Ecosystem Studies, Jingdong 676200, Yunnan, China.
authors.forename: Yi-Ping
authors.initials: YP
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun 666303, China.|Global Change Ecology Group, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun 666303, China.
authors.forename: Li-Qing
authors.initials: LQ
authors.lastname: Sha
authors.affiliation: Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun 666303, China.|Global Change Ecology Group, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun 666303, China.
authors.forename: Yun-Tong
authors.initials: YT
authors.lastname: Liu
authors.affiliation: Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun 666303, China.|Global Change Ecology Group, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun 666303, China.
authors.forename: Wen-Jun
authors.initials: WJ
authors.lastname: Zhou
authors.affiliation: Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun 666303, China.|Global Change Ecology Group, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun 666303, China.|University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Chuan-Sheng
authors.initials: CS
authors.lastname: Wu
authors.affiliation: Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun 666303, China.|Ailaoshan Station for Subtropical Forest Ecosystem Studies, Jingdong 676200, Yunnan, China.
authors.forename: Zhi-Yun
authors.initials: ZY
authors.lastname: Lu
authors.affiliation: Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun 666303, China.|University of Chinese Academy of Sciences, Beijing 100049, China.|Ailaoshan Station for Subtropical Forest Ecosystem Studies, Jingdong 676200, Yunnan, China.
authors.forename: Kang
authors.initials: K
authors.lastname: Luo
authors.affiliation: Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun 666303, China.|Global Change Ecology Group, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun 666303, China.|University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Jin-Bo
authors.initials: JB
authors.lastname: Gao
authors.affiliation: Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun 666303, China.|Ailaoshan Station for Subtropical Forest Ecosystem Studies, Jingdong 676200, Yunnan, China.
authors.forename: Yu-Hong
authors.initials: YH
authors.lastname: Liu