title: Time lags between crown and basal sap flows in tropical lianas and co-occurring trees.
abstract: Water storage in the stems of woody plants contributes to their responses to short-term water shortages. To estimate the contribution of water storage to the daily water budget of trees, time lags of sap flow between different positions of trunk are used as a proxy of stem water storage. In lianas, another large group of woody species, it has rarely been studied whether stored water functions in their daily water use, despite their increasing roles in the carbon and water dynamics of tropical forests caused by their increasing abundance. We hypothesized that lianas would exhibit large time lags due to their extremely long stems, wide vessels and large volume of parenchyma in the stem. We examined time lags in sap flow, diel changes of stem volumetric water content (VWC) and biophysical properties of sapwood of 19 lianas and 26 co-occurring trees from 27 species in 4 forests (karst, tropical seasonal, flood plain and savanna) during a wet season. The plants varied in height/length from <5 to >60 m. The results showed that lianas had significantly higher saturated water content (SWC) and much lower wood density than trees. Seven of 19 liana individuals had no time lags; in contrast, only 3 of 26 tree individuals had no time lags. In general, lianas had shorter time lags than trees in our data set, but this difference was not significant for our most conservative analyses. Across trees and lianas, time lag duration increased with diurnal maximum changeable VWC but was independent of the body size, path length, wood density and SWC. The results suggest that in most lianas, internal stem water storage contributes little to daily water budget, while trees may rely more on stored water in the stem.
authors.affiliation: Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China University of Chinese Academy of Sciences, Beijing 100049, China chenyj@xtbg.org.cn caokf@xtbg.ac.cn.
authors.forename: Ya-Jun
authors.initials: YJ
authors.lastname: Chen
authors.affiliation: Forest Ecology and Forest Management Group, Wageningen University, PO Box 47, 6700 AA Wageningen, The Netherlands.
authors.forename: Frans
authors.initials: F
authors.lastname: Bongers
authors.affiliation: Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China.
authors.forename: Kyle
authors.initials: K
authors.lastname: Tomlinson
authors.affiliation: Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China.
authors.forename: Ze-Xin
authors.initials: ZX
authors.lastname: Fan
authors.affiliation: Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China.
authors.forename: Hua
authors.initials: H
authors.lastname: Lin
authors.affiliation: Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China.
authors.forename: Shu-Bin
authors.initials: SB
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China.
authors.forename: Yu-Long
authors.initials: YL
authors.lastname: Zheng
authors.affiliation: Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China.
authors.forename: Yang-Ping
authors.initials: YP
authors.lastname: Li
authors.affiliation: State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, and College of Forestry, Guangxi University, Nanning, Guangxi 530004, China chenyj@xtbg.org.cn caokf@xtbg.ac.cn.
authors.forename: Kun-Fang
authors.initials: KF
authors.lastname: Cao
authors.affiliation: Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China.
authors.forename: Jiao-Lin
authors.initials: JL
authors.lastname: Zhang
mesh_terms: D018526:Plant Transpiration / Q000502:physiology; D014197:Trees / Q000378:metabolism* / Q000502:physiology; D014867:Water / Q000378:metabolism
chemical_list: D014867:Water
keywords: frequency domain reflectometry; hydraulic capacitance; transpiration; volumetric water content; water relations; water storage