Yi Wang, Antonio D. del Campo, Xiaohua Wei, Rita Winkler, Wanyi Liu, Qiang Li
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引用次数: 8
Abstract
Water-use efficiency (WUE) represents the coupling of forest carbon and water. Little is known about the responses of WUE to thinning at multiple spatial scales. The objective of this research was to use field measurements to understand short-term effects of two thinning treatments (T1: 4500 stems ha?1; and T2: 1100 stems ha?1) and the control (NT: 27,000 stems ha?1) on WUE at the three spatial scales (leaf level: the ratio of leaf photosynthesis to leaf transpiration; tree-level: tree growth to tree transpiration; and stand level: net primary production (NPP) to stand transpiration) and intrinsic WUEi (the ratio of leaf photosynthesis to stomatal conductance at leaf-level; and NPP to canopy conductance at stand-level) in a 16-year old natural lodgepole pine forest. Leaf-level measurements were conducted in 2017, while tree- and stand-level measurements were conducted in both 2016 (the normal precipitation year) and 2017 (the drought year).
The thinning treatments did not significantly affect the tree- and stand-level WUE in the normal year of 2016. However, the thinning significantly affected WUE in the drought year of 2017: T2 exhibited significantly higher tree-level WUE (0.49?mm2?kg?1) than NT?(0.08?mm2?kg?1), and compared to NT, the stand-level WUE values in the thinned stands (T1 and T2) were significantly higher, with means of?0.31, 0.56 and 0.70?kg?m?3, respectively. However, the leaf-level and stand-level WUEi in the thinned stands in the drought year were significantly lower than those in the unthinned stands. No significant differences in the leaf-level WUE were found among the treatments in 2017. In addition, the thinning?did not significantly change the WUE-VPD relationships at any studied spatial scale.
The thinning treatments did not cause significant changes in all studied WUE metrics in a normal year. However, their effects were significantly promoted under the drought conditions probably due to the decrease in soil water availability, demonstrating that thinning can improve WUE and consequently support forests to cope with the drought effects. The inconsistent results on the effects of the thinning on forest carbon and water coupling at the spatial scales and the lack of the consistent WUE metrics constraint across-scale comparison and transferring of WUE.
水分利用效率(WUE)是森林碳与水的耦合关系。在多个空间尺度上，WUE对疏变的响应知之甚少。本研究的目的是利用田间测量来了解两种间伐处理(T1: 4500茎/公顷;T2: 1100茎ha?1)和对照(NT: 27000茎ha?1)在三个空间尺度(叶片水平:叶片光合与蒸腾之比;树级:树木生长到树木蒸腾;林分水平:净初级生产量(NPP)与林分蒸腾的比值和内在WUEi(叶片光合作用与气孔导度之比);林分水平NPP与冠层导度的比值)。2017年进行了叶片水平测量，而2016年(正常降水年)和2017年(干旱年)分别进行了树木和林分水平测量。在2016年正常年，间伐处理对林木和林分水分利用效率无显著影响。然而，在2017年干旱年，间伐对水分利用效率有显著影响:T2的林木水平水分利用效率(0.49 mm2 - kg - 1)显著高于NT (0.08 mm2 - kg - 1)，而T1和T2的林分水平水分利用效率显著高于NT，平均值分别为0.31、0.56和0.70 kg - m - 1。3,分别。枯水年间伐林分的叶级和林级WUEi显著低于未间伐林分。2017年各处理叶片水分利用效率无显著差异。此外，变薄?在任何研究的空间尺度上，WUE-VPD关系都没有显著改变。在正常年份，间伐处理没有引起所有研究的WUE指标的显著变化。然而，在干旱条件下，它们的作用显著增强，这可能是由于土壤水分有效性的降低，表明间伐可以提高水分利用效率，从而支持森林应对干旱影响。在空间尺度上，间伐对森林碳水耦合影响的结果不一致，且缺乏一致的水分利用效率指标，限制了水分利用效率的跨尺度比较和转移。
期刊介绍：
Carbon Balance and Management is an open access, peer-reviewed online journal that encompasses all aspects of research aimed at developing a comprehensive policy relevant to the understanding of the global carbon cycle.
The global carbon cycle involves important couplings between climate, atmospheric CO2 and the terrestrial and oceanic biospheres. The current transformation of the carbon cycle due to changes in climate and atmospheric composition is widely recognized as potentially dangerous for the biosphere and for the well-being of humankind, and therefore monitoring, understanding and predicting the evolution of the carbon cycle in the context of the whole biosphere (both terrestrial and marine) is a challenge to the scientific community.
This demands interdisciplinary research and new approaches for studying geographical and temporal distributions of carbon pools and fluxes, control and feedback mechanisms of the carbon-climate system, points of intervention and windows of opportunity for managing the carbon-climate-human system.
Carbon Balance and Management is a medium for researchers in the field to convey the results of their research across disciplinary boundaries. Through this dissemination of research, the journal aims to support the work of the Intergovernmental Panel for Climate Change (IPCC) and to provide governmental and non-governmental organizations with instantaneous access to continually emerging knowledge, including paradigm shifts and consensual views.
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