Impact of land management practices on tree water use strategy and
responses to drought in a dryland plantation
Abstract
Extreme droughts of increased frequency due to climate change poses
great challenges to the sustainability of plantations in drylands
worldwide. Millions of plantations on China’s Loess Plateau which are
mainly in drylands are threatened by serious degradation due to water
scarcity. Here we aim to disentangle the impacts of combinations of
terracing and mulching on water use strategy and its response to extreme
droughts in a rainfed jujube (Ziziphus jujuba) plantation on the
semiarid Loess Plateau, using three-year in situ field observations.
Pruned jujube branches and maize straw were mulched on half-moon
terraces to form two combined treatments, referred to as JBT and MST,
respectively. The efficacy of these two combinations on the water use
strategy of jujube trees was compared with terracing alone (SHT) and
control (no terrace). We found that extreme drought clearly reduced soil
water storage (SWS) under all treatments. However, the combined
treatments showed significantly (P<0.05) higher SWS than the
SHT and control. Furthermore, the combined treatments enhanced soil
water use in deep layers during both normal and drought years, thus
helping jujube trees to resist droughts. Moreover, the extreme drought
significantly reduced transpiration whereas the moderate drought
increased transpiration at both seasonal and annual scales. Nonetheless,
the combined treatments were associated with enhanced transpiration
compared to the SHT and control during drought periods. Finally, jujube
trees exhibited isohydric behavior which also helped them to cope with
prolonged droughts. Overall, the findings here may provide insights into
land management of dryland plantations worldwide under climate change.