A possible link between life and death of a xeric tree in desert

详细信息    查看全文

• 作者：Gui-Qing Xu^a ; Nate G. McDowell^b ; Yan Li^a ; ^{liyan@ms.xjb.ac.cn" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Biomass allocation ; Hydraulic conductance ; Non-structural carbohydrates ; Root distribution ; Drought-resistance strategy ; Tree mortality
• 刊名：Journal of Plant Physiology
• 出版年：2016
• 出版时间：1 May 2016
• 年：2016
• 卷：194
• 期：Complete
• 页码：35-44
• 全文大小：2211 K

文摘

Understanding the interactions between drought and tree ontogeny or size remains an essential research priority because size-specific mortality patterns have large impacts on ecosystem structure and function, determine forest carbon storage capacity, and are sensitive to climatic change. Here we investigate a xerophytic tree species (Haloxylon ammodendron (C.A. Mey.)) with which the changes in biomass allocation with tree size may play an important role in size-specific mortality patterns. Size-related changes in biomass allocation, root distribution, plant water status, gas exchange, hydraulic architecture and non-structural carbohydrate reserves of this xerophytic tree species were investigated to assess their potential role in the observed U-shaped mortality pattern. We found that excessively negative water potentials (<−4.7 MPa, beyond the P50_leaf of −4.1 MPa) during prolonged drought in young trees lead to hydraulic failure; while the imbalance of photoassimilate allocation between leaf and root system in larger trees, accompanied with declining C reserves (<2% dry matter across four tissues), might have led to carbon starvation. The drought-resistance strategy of this species is preferential biomass allocation to the roots to improve water capture. In young trees, the drought-resistance strategy is not well developed, and hydraulic failure appears to be the dominant driver of mortality during drought. With old trees, excess root growth at the expense of leaf area may lead to carbon starvation during prolonged drought. Our results suggest that the drought-resistance strategy of this xeric tree is closely linked to its life and death: well-developed drought-resistance strategy means life, while underdeveloped or overdeveloped drought-resistance strategy means death.