The positive contribution of iWUE to the resilience of Schrenk spruce ( Picea schrenkiana ) to extreme drought in the we
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ORIGINAL ARTICLE
The positive contribution of iWUE to the resilience of Schrenk spruce (Picea schrenkiana) to extreme drought in the western Tianshan Mountains, China Guoju Wu1 · Xiaohong Liu1,2 · Tuo Chen1 · Guobao Xu1 · Bo Wang1,3 · Huhu Kang1,3 · Caijuan Li1,3 · Xiaomin Zeng2 Received: 23 March 2020 / Revised: 21 October 2020 / Accepted: 21 October 2020 © Franciszek Górski Institute of Plant Physiology, Polish Academy of Sciences, Kraków 2020
Abstract Drought-related forest growth declines are observed globally in main forest types, especially with repeatedly hot droughts. Therefore, quantifying forest resilience and identifying the factors driving resilience in response to extreme drought with the consideration of atmospheric C O2 fertilization is crucial for the accurate assessment of forest dynamics under current climate change, particularly for the widespread and climate-sensitive spruce forests in the arid Tianshan Mountains, China. Here, we explored the growth response of Schrenk spruce (Picea schrenkiana) to six extreme drought events since 1900, and investigated how tree resilience in pure stands is related to local drought intensity, cambial age (CA), and intrinsic water-use efficiency (iWUE). Specifically, we found that spruce trees had a mean resistance (Rt) value of less than 1, with iWUE contributing less to Rt variation. The results are in agreement with the drought-induced limitations on tree growth in response to increasing C O2, in spite of rising iWUE trends. However, increased iWUE has significant and positive impacts on the recovery (17%) and resilience (15%) of trees, suggesting that increased iWUE enhances the restoration of Schrenk spruce growth after extreme drought events. The growth resilience indices of Schrenk spruce showed that juvenile and adult trees exhibit different strategies to mitigate the drought influences. This study indicated that tree age, climate conditions, and variation in iWUE should be considered simultaneously in drought resilience evaluations to assess forest dynamics objectively in relation to climate change (i.e., drought) and propose appropriate forest management strategies. Keywords Extreme drought · iWUE variation · Radial growth · Resistance · Recovery · Resilience
Introduction
Communicated by P. Wojtaszek. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11738-020-03158-1) contains supplementary material, which is available to authorized users. * Xiaohong Liu [email protected]; [email protected] 1
State Key Laboratory of Cryospheric Science, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China
2
School of Geography and Tourism, Shanxi Normal University, Xi’an 710119, Shaanxi, China
3
University of the Chinese Academy of Sciences, Beijing 100049, China
Extreme drought events are usually compounded by warm temperatures, and are increasingly being recognized as the key factor driving changes in tree growth rates (Allen et al. 2010, 2015).
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