Elevation-dependent variations of tree growth and intrinsic water-use efficiency in Schrenk spruce (Picea schrenkiana) in the western Tianshan Mountains, China.
Elevation-dependent variations of tree growth and intrinsic water-use efficiency in Schrenk spruce (Picea schrenkiana) in the western Tianshan Mountains, China.
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DOI：
10.3389/fpls.2015.00309
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发表时间：
2015
影响因子：
5.6
通讯作者：
Zhang X
中科院分区：
文献类型：
--
作者：
Wu G;Liu X;Chen T;Xu G;Wang W;Zeng X;Zhang X
大气CO2浓度(Ca)的升高有望通过增强光合作用和提高固有水分利用效率(IWUE)来加速树木的生长。然而，这种对长期IWUE的影响程度以及它与气候的相互作用在沿着海拔梯度的树木中仍不清楚。为此，我们基于1960年至2010年的断面积增量(BAI)和树轮δ13C年表，研究了位于上树线(A1：2700ma.s.l)、中海拔(A2：2400ma.s.l)和林下限(A3：2200ma.s.l)的天山云杉成熟树的径向生长和IWUE的变化，以及与钙含量上升和气候变化的关系。我们利用CRUTS3.22数据集分析了树木生长对区域气候年际变化的总体响应，发现A1的BAI和δ13C对气候的敏感性低于A2和A3。计算了三种理论情景下IWUE的时间趋势，作为解释观测到的Ca增加时的气体交换的基线。我们发现，在过去的50年里，从A1到A3，iWUE增加了12-32%，并表现出随海拔高度变化的生理反应。A2和A3的BAI与IWUE呈显著负相关，表明尽管IWUE长期增加，但树木的生长一直在减少。然而，BAI在整个研究期间基本保持稳定，尽管IWUE在A1[1980年前恒定的胞间二氧化碳浓度(Ci)]增加最强。我们的结果表明，在低海拔地区，干旱诱导的树木生长对二氧化碳浓度上升的响应受到限制，而自1980年以来，上层树木的生长没有明显的变化，IWUE的改善也有所减弱。这项研究可能与这样的预期相矛盾，即钙升高和气温上升的综合影响提高了森林生产力，特别是在高海拔森林。
Rising atmospheric CO2 concentration (Ca) is expected to accelerate tree growth by enhancing photosynthesis and increasing intrinsic water-use efficiency (iWUE). However, the extent of this effect on long-term iWUE and its interactions with climate remains unclear in trees along an elevation gradient. Therefore, we investigated the variation in the radial growth and iWUE of mature Picea schrenkiana trees located in the upper tree-line (A1: 2700 m a.s.l.), middle elevation (A2: 2400 m a.s.l.), and lower forest limit (A3: 2200 m a.s.l.), in relation to the rising Ca and changing climate in the Wusun Mountains of northwestern China, based on the basal area increment (BAI) and tree-ring δ13C chronologies from 1960 to 2010. We used the CRU TS3.22 dataset to analyze the general response of tree growth to interannual variability of regional climate, and found that BAI and δ13C are less sensitive to climate at A1 than at A2 and A3. The temporal trends of iWUE were calculated under three theoretical scenarios, as a baseline for interpreting the observed gas exchange at increasing Ca. We found that iWUE increased by 12–32% from A1 to A3 over the last 50 years, and showed an elevation-dependent variation in physiological response. The significant negative relationship between BAI and iWUE at A2 and A3 showed that tree growth has been decreasing despite long-term increases in iWUE. However, BAI remained largely stable throughout the study period despite the strongest iWUE increase [at constant intercellular CO2 concentration (Ci) before 1980] at A1. Our results indicate a drought-induced limitation of tree growth response to rising CO2 at lower elevations, and no apparent change in tree growth and diminished iWUE improvement since 1980 in the upper tree-line. This study may contradict the expectation that combined effects of elevated Ca and rising temperatures have increased forest productivity, especially in high-elevation forests.
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影响因子：
11.6
作者：
Levesque, Mathieu;Saurer, Matthias;Rigling, Andreas
通讯作者：
Rigling, Andreas
影响因子：
1.6
作者：
Biondi, Franco;Qeadan, Fares
通讯作者：
Qeadan, Fares
影响因子：
2
作者：
Laumer, W.;Andreu, L.;Wissel, H.
通讯作者：
Wissel, H.
影响因子：
3.7
作者：
Allen, Craig D.;Macalady, Alison K.;Cobb, Neil
通讯作者：
Cobb, Neil
影响因子：
2.7
作者：
Feng, XH
通讯作者：
Feng, XH