黄土高原羊圈沟小流域人工物种和自然物种径向生长对气候变化的响应差异

Climate effect on the radial growth of introduced and native tree species in the Yangjuangou catchment of the Loess Plateau

为揭示黄土高原人工和自然物种径向生长对气候变化的响应差异,在延安羊圈沟小流域分别获取人工和自然物种的树木年轮材料并构建标准年表,其中人工物种为刺槐(Robinia pseudoacacia)和柠条(Caragana korshinskii),自然物种为山杏(Armeniaca sibirica)和荆条(Vitex negundo var. heterophylla),并对年表中的气候信号进行了统计分析。结果表明:1)人工物种年表中的气候信号较强,主要表现在5—8月份,与温度呈负相关关系(刺槐:r=-0.427—-0.427,P<0.05;柠条:r=-0.738—-0.227,P<0.05),与降雨则呈正相关关系,但相关系数未达到显著性水平;自然物种年表中的气候信号较弱,与温度和降雨的相关关系均较低; 2)不同于自然物种,人工物种树轮年表还与去年夏季(7—9月份)温度(负相关)和降水(正相关)存在相关关系,表明人工物种树木生长对气候因子存在一定滞后性; 3)人工物种树轮年表与PDSI干旱指数在各月份均维持正相关关系,在生长季(刺槐4—9月、柠条4—8月)达到显著水平(刺槐:r=0.481—0.704,P<0.05;柠条:r=0.314—0.610,P<0.05);而自然物种年表与PDSI干旱指数的相关关系较弱,均未达到相关性水平。从各年表与气候要素(温度、降雨、PDSI)响应强度来看,黄土高原人工物种树木生长受水分胁迫显著,且以刺槐最为明显,其次是柠条;自然物种树木生长则没有明显干旱胁迫的影响,仅山杏生长受一定水分胁迫影响,荆条生长则与各气候要素关系较弱,水分胁迫对其生长的影响已很小。本研究的结果表明黄土高原人工物种生长明显受到水分条件限制,而自然恢复物种生长则受水分条件影响较小,能适应黄土高原干旱半干旱气候条件。

A considerable challenge faced by the largest Grain-to-Green Programme of the Chinese Loess Plateau( CLP) is whether planted species can adapt to semi-arid climates. Our project aimed to explore the adaption characteristics of introduced vegetation under warming and drying climates in the Yangjuangou catchment of the Loess Plateau. We analyzed and commpred the differences of inter-annual radial growth responding to climate change between introduced and native tree species. Based on dendrochronological methods,we collected tree-ring samples and established ring-width chronologies for both introduced( Robinia pseudoacacia,Caragana korshinskii) and native( Armeniaca sibirica, Vitex negundo var.heterophylla) species. Relationships between the environmental factors( temperature, precipitation, Palmer Drought Severity Index( PDSI)) and tree-ring index were determined using correlation analyses. The results showed that: 1) The tree-ring width series of introduced species had significantly passive correlations with May—August temperatures( R.pseudoacacia:-0.511 to-0.427; C. korshinskii:-0.738 to-0.227; P<0.05) and positive correlations with May—August precipitation; tree-ring series of native species were also negatively correlated with the temperature and positively correlated with precipitation,but not significantly; 2) Different from those of native species,the tree-ring width series of introduced species showed a relationship with the temperature and precipitation from the growing season of the previous summer( July—September),indicating that the environmental factors had a lag-effect on the growth of the introduced species; 3)The tree-ring width series of introduced species maintained positive correlations with PDSI each month with the highest correlation coefficients( R. pseudoacacia: 0.481 to 0.704; C. korshinskii: 0.314 to 0.610; P<0.05) in the growing season( R. pseudoacacia April—September,C. korshinskii April—August). However,there was a weak correlation that did not reach a significant level between the native species and PDSI; 4) The tree-ring chronologies showed a specific intensity response to environmental factors( temperature,precipitation,PDSI),introduced species were strongly negatively affected by water stress in the CLP semi-arid region,with R. pseudoacacia affected the most followed by C. korshinskii; however,native trees were only weakly affected by drought,where A. sibirica growth was normal in the severe drought condition,and V. negundo var. heterophylla was the most drought tolerant species and relatively robust to the effects of climate change. In conclusion,introduced species were strongly negatively affected by water stress, suggesting their growth would be unsustainable in the future,and native trees were weakly affected by drought,and could adapt to the climate change trends in the CLP semi-arid area.