Biotic- and abiotic-driven variations of the night-time sap flux of three co-occurring tree species in a low subtropical secondary broadleaf forest.

Qian Wang,Guangyan Ni,Ping Zhao,Xiuhua Zhao,Lei Ouyang,Liwei Zhu,Jianguo Gao

doi:10.1093/aobpla/ply025

Qian Wang, Guangyan Ni + Show 5 more

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https://doi.org/10.1093/aobpla/ply025

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Abstract

Although several studies on the night-time water use of different plant species have been reported, comparative studies under the same climatic conditions of a region are scarce. This study aimed to analyse the inter- and intraspecific variations in night-time water use in relation to environmental factors and to tree morphological features to understand and elucidate the possible underlying mechanisms. The sap flow of three co-occurring tree species in a low subtropical secondary broadleaf forest in South China was monitored using Granier-style sap flux sensors. All examined environmental factors except wind speed exerted significant influence on the daytime sap flows of Schima superba, Castanopsis hystrix and Michelia macclurei, but the impacts of all factors, including wind speed, on the night-time sap flux were trivial. These results indicated that sap flow was mainly used for water recharge at night. The morphological features of the trees, except tree height, significantly affected the daytime water use, but no morphological features significantly affected the night-time water use. We found that night-time water recharge was strongly affected by the maximum flux density. A principal component analysis showed that there were more intraspecific than interspecific variations in water transport. The results also revealed that the night-time water use and the percentage of night/day (Qn/Qd) of photosynthetic stem species (C. hystrix and M. macclurei) were greater than those of non-photosynthetic stem species (S. superba).

Highlights

The leaf stoma is the site where water is transpired into the ambient air, namely, transpiration (E)
The sap flux densities of trees 2, 5 and 8 were the lowest for each of the three tree species, which was verified by the principal component analysis (PCA) results because they were located in the third quadrant (Fig. 2, right)
We found that the night-time water use was strongly affected by Jsmax,n, and this effect was irrespective of the tree morphological features when we pooled the measured data from all three tree species and analysed them together (R2 = 0.870, P < 0.001; Fig. 5, left)

Summary

Introduction

The leaf stoma is the site where water is transpired into the ambient air, namely, transpiration (E). It has been reported that Ouratea hexasperma has reduced stomatal conductance (gs) in nitrogen-rich environments, so the amount of water used greatly declines at night (Scholz et al 2007) This suggests that the plant’s night-time water use may be related to nitrogen uptake and can be affected by available soil nitrogen. Another study has shown that soil nitrogen limitation did not affect the night-time transpiration (En) or water loss of two Populus species, which mainly showed effects related to soil moisture conditions (Howard and Donovan 2010). Dawson et al (2007) studied 18 trees and shrubs in seven vegetation types and found that night-time transpiration or a certain degree of gs were related to soil moisture fluctuation They inferred that night-time stomatal opening was conducive to the assimilation of carbon by plants in the early morning of the day. More experiments are needed to elucidate the ecophysiological significance of night-time water use by plants

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