气候变化对阔叶红松林潜在地理分布区的影响

物种地理分布主要取决于它对气候、地形等环境因子的适应性。基于22个环境因子和阔叶红松林的4类主要建群树种——红松、紫椴、水曲柳和蒙古栎的地理分布数据,采用最大熵模型模拟了阔叶红松林的潜在分布区域,并分析决定阔叶红松林地理分布的主要气候和地形因子,最后利用政府间气候变化专门委员会(IPCC)发布的3种排放场景(SRES-A2、SRES-A1B、SRES-B1)下2020、2050、2080年的气候数据预测阔叶红松林的未来潜在分布区。结果表明:各树种的受试者工作特征曲线下面积(AUC值)都大于0.8,说明模型有很好的预测能力;影响阔叶红松林分布的主导环境因子是年降雨量、季节性降雨量、海拔、年平均温度、最湿季度的平均温度。在基准气候条件下,阔叶红松林的高度适宜分布区主要分布在长白山和小兴安岭地区,占研究区总面积的11.69%,低度适宜区面积、不适宜区面积分别占研究区总面积的23%和65.31%。模型预测结果显示,未来在A2、A1B和B1气候情景下,阔叶红松林高度适宜区的南界与北界都向北移动,其面积有缩减的趋势,而低度适宜区的面积有增加的趋势。

Impacts of climate change on the potential geographical distribution of broadleaved Korean pine (Pinus koraiensis) forests

Species-environment relationships have always been a central issue in ecology and biogeography. The adaptation of species to a changing natural environment, including topographical and climatic factors, determines its geographic distribution. Accumulating evidence has revealed that Northeast China has experienced the greatest temperature increase since the 1950s, which in turn affected species distribution in this region. Broadleaved Korea pine (Pinus koraiensis) mixed forest (BKF) is the native forest type in the southern part of Northeast China. The distribution area of this species has shrunk substantially due to historical overexploitation. It is important for forest managers to be able to predict the potential geographic distribution of BKF based on species-environment relationships. Although the distributions of individual species in BKF such as P. koraiensis and Quercus mongolica have been reported previously, few studies have focused on the potential geographic distribution of BKF. In this study, four dominant tree species -P. koraiensis, Q. mongolica, Tilia amurensis and Fraxinus mandshurica, which together account for more than 80% of the growing stock in primary BKF, were selected to represent this forest type. Nineteen climatic and three topographic variables in Northeast China that are considered to be most likely influences on the geographic distribution of tree species were selected as environmental factors. To identify the major climatic and topographic factors controlling BKF distribution and simulate the potential geographic distribution of BKF under current climatic condition, the geographic distribution records of the dominant tree species, together with the environmental factors, were used in the Maxent model. The future geographic distributions of BKF were consequently predicted for the 2020s, 2050s, and 2080s, based on three kinds of climate change scenarios (SRES-A2, SRES-A1B, SRES-B1) published by the Intergovernmental Panel on Climate Change (IPCC). For the four dominant tree species, the simulations showed that the area under the curve indexes (AUC) were 0.925, 0.890, 0.859, and 0.847, respectively. All these values exceeded 0.8, which indicates that the models had a good predictive performance. The major environmental factors affecting the distribution of BKF included annual precipitation, precipitation seasonality, elevation, annual mean temperature and mean temperature of wettest quarter. For the entire region, 11.69% of the total area was identified to be of high suitability for BKF distribution, 23% was of low suitability, and 65.31% of the area was unsuitable. Under the A2, A1B, and B1 scenarios, the model predicted that both the southern and northern boundary of the high suitability area for BKF will shift northward. Overall, the high suitability area in this region was predicted to decrease, with the extent of the decrease depending on the severity of climate change. For example, under the A2 and A1B scenarios, the high suitability area in Northeast China will be less than 1% of the region by the 2080s. Overall, the results indicate that if no effective measures are taken to mitigate climate change, there is a great possibility that BKF will disappear from Northeast China.