Climate change may accelerate the decline of desert riparian forest in the lower Tarim River, Northwestern China: Evidence from tree-rings of Populus euphratica

Abstract

Although climate change has emerged as a major threat to biodiversity, few assessments exist of the sensitivity of desert riparian forests to climate in extremely arid plain areas. We mapped tree growth-climate correlations (time period: 1957–2015) to identify the sensitivities of Populus euphratica (P. euphratica), a dominant and important tree species in the desert riparian forest in the lower Tarim River, an extremely arid area in China, to climate change. The results indicated that groundwater depth was the key factor for controlling tree growth in the study area. In order to accurately assess sensitivity to climate change of the desert riparian forest, it was necessary to consider the effects of hydrological fluctuations on P. euphratica because the sensitivities of tree growth to precipitation and temperature depended on changes in the groundwater environment. The groundwater depth threshold to distinguish the sensitivity of climate change to P. euphratica growth was 6–7 m. Moreover, warming would accelerate desert riparian forest decline when the groundwater depth was more than 6 m because an anomalously high temperature would intensify evapotranspiration and the shortage of soil moisture during the growing season, and offset the benefits from precipitation, which would cause more drought if groundwater was not compensated by sufficient runoff. Therefore, global warming would bring great disadvantages to desert riparian forests if the current mode of the ecological water conveyance project (EWCP) continues to be implemented without a fixed time and water amount in the lower Tarim River, which could not steadily decrease and actively maintain shallow groundwater depth.