Disentangling the Effects of Tree and Soil Properties on the Water Uptake of a Waterlogging Tolerant Tree in the Yangtze River Delta, China

Beibei Zhang,Deqiang Gao,Haijun Zuo,Jing Jiang,Ranran Ren,Qing Xu

doi:10.3390/f12111547

Abstract

Waterlogging tolerant tree species exert a critical role in forest preservation and the associated water conservation in flood prone areas. Clarifying the patterns and drivers of water uptake by waterlogging tolerant trees is crucial for forest management in flood-prone areas, especially in the scenario of precipitation changes in the estuary delta. Here, we uploaded the values of δD and δ18O obtained from soil and xylem waters to a Bayesian mixed model (MixSIAR) to determine the water use pattern of Taxodium distichum, a waterlogging tolerant tree, following different magnitudes of rainfall events in three sites of the Yangtze River Delta, China. We further conducted variation partitioning analysis and a random forest model to discern the dominant factor driving plant water uptake. Our results indicated that T. distichum mainly absorbed soil water from shallow soil layers (0–40 cm, 43.63%–74.70%), while the percentage of water uptake from deep soil layers was lower in the Yangtze River Delta (60–100 cm, 13.43%–35.90%), whether in light, moderate, or heavy rainfall conditions. Furthermore, our results demonstrated that tree traits, such as fine root biomass, are dominantly driving plant water uptake. These findings imply that waterlogging tolerant tree species could increase the percentage of water uptake from shallow soils by changing their plant attributes, which would effectively improve the water conservation of forests in the estuary delta.

Highlights

Changes in global precipitation increase the frequency and intensity of extreme precipitation in humid areas, subsequently leading to frequent floods [1,2,3]
Our results revealed that δD and δ18 O in shallow groundwater were distributed on the local meteoric water line (LMWL), while those in soil and xylem water were located on the right side of the LMWL in the T. distichum plantations of the Yangtze River Delta, indicating that both xylem and soil water did not exchange with groundwater
Based on the δD and δ18 O coupled with the Bayesian mixed model, our study revealed that T. distichum, a waterlogging tolerant tree species, mainly absorbed shallow soil water in the Yangtze River Delta of China, whether in light, moderate, or heavy rainfalls

Summary

Introduction

Changes in global precipitation increase the frequency and intensity of extreme precipitation in humid areas, subsequently leading to frequent floods [1,2,3]. Floods induced by extreme precipitation expose trees to waterlogging stress, and cause root hypoxia and inhibit plant respiration, increasing the tree mortality [4,5,6]. This phenomenon is universal in the river basins and estuarine deltas of tropical/subtropical areas [7,8,9]. In order to alleviate the large-scale tree death caused by frequent floods, tree species owning waterlogging resistance have been cultivated in some estuarine deltas in recent years. Knowledge on water use pattern of waterlogging tolerant tree species is of importance for forest management in flood-prone areas

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