Jia Guodong, Liu Ziqiang, Chen Lixin, Yu Xinxiao
Key Laboratory of State Forestry Administration on Soil and Water Conservation Beijing Forestry University Beijing China.
Beijing Engineering Research Center of Soil and Water Conservation Beijing Forestry University Beijing China.
Ecol Evol. 2017 Nov 5;7(24):10640-10651. doi: 10.1002/ece3.3584. eCollection 2017 Dec.
Water stress is regarded as a global challenge to forests. Unlike other water-limited areas, the water use strategies of rocky mountainous forests, which play an important ecohydrological role, have not received sufficient attention. To prove our hypothesis that species adopt different water use strategies to avoid competition of limited water resources, we used site abiotic monitoring, sap flow and stable isotope method to study the biophysiological responses and water use preferences of two commonly distributed forest species, (Pt) and (Qv). The results showed that Pt transpired higher than Qv. Pt was also prone to adopt isohydric water use strategy as it demonstrated sensitive stomatal control over water loss through transpiration. Qv developed cavitation which was reflected by the dropping in response to high vapor pressure deficit, concentrated peak sap flux density (), and enlarged hysteresis loop. Considering the average soil depth of 52.8 cm on the site, a common strategy shared by both species was the ability to tap water from deep soil layers (below 40 cm) when soil water was limited, and this contributed to the whole growing season transpiration. The contribution of surface layer water to plant water use increased and became the main water source for transpiration after rainfall. Qv was more efficient at using water from surface layer than Pt due to the developed surface root system when soil water content was not stressed. Our study proves that different water-using strategies of co-occurring species may be conducive to avoid competition of limited water resources to guarantee their survival. Knowledge of water stress-coping strategies of trees has implications for the understanding and prediction of vegetation composition in similar areas and can facilitate forest management criteria for plantations.
水分胁迫被视为森林面临的全球性挑战。与其他水资源有限的地区不同，落基山森林的水分利用策略虽发挥着重要的生态水文作用，但尚未得到足够关注。为证明我们的假设，即物种采用不同的水分利用策略以避免对有限水资源的竞争，我们运用实地非生物监测、液流和稳定同位素方法，研究了两种常见分布的森林物种——白云杉（Pt）和颤杨（Qv）的生物生理响应及水分利用偏好。结果表明，Pt的蒸腾作用高于Qv。Pt也倾向于采用等水型水分利用策略，因为它通过蒸腾作用对水分流失表现出敏感的气孔控制。Qv出现了空穴现象，这表现为在高水汽压差下导水率下降、液流通量密度峰值集中（）以及滞后环扩大。考虑到该地点的平均土壤深度为52.8厘米，两种物种共有的一个常见策略是，在土壤水分有限时能够从深层土壤（40厘米以下）获取水分，这有助于整个生长季的蒸腾作用。降雨后，表层水对植物水分利用的贡献增加，并成为蒸腾作用的主要水源。当土壤水分不紧张时，由于发达的表层根系，Qv比Pt更有效地利用表层水。我们的研究证明，共存物种不同的水分利用策略可能有助于避免对有限水资源的竞争，以确保它们的生存。了解树木应对水分胁迫的策略，对于理解和预测类似地区的植被组成具有重要意义，并且有助于制定人工林的森林管理标准。
