基于物种分布模型的兴安落叶松林概率分布区动态研究

Dynamic Study on Probability Distribution Zone of Larix gmelinii Forest Based on Species Distribution Model

全球变暖对森林的地理分布有重要影响,兴安落叶松是北方森林生态系统的重要组成部分。因此,有必要准确评价气候变暖对兴安落叶松天然林地理分布的影响,为制定兴安落叶松林的可持续经营提供依据,基于机械布点的方法在东北地区建立了68个半径为17.85 m、面积为1000 m^(2)的兴安落叶松天然林临时样圆。从ClimateAP软件获取1950-2017年的气候数据,通过M-K检验判定区域年均温突变点。根据影响兴安落叶松地理分布的8个潜在气候因子变量:年均温(MAT)、最冷月均温(MCMT)、最暖月均温(MWMT)、最冷最暖月温差(TD)、年均降水量(MAP)、秋季降水量(MAPA)、>5℃年积温(DD>5℃)和哈格里夫斯水分亏缺(HCMD),利用MaxEnt模型选取突变前后影响兴安落叶松林地理分布的主导气候因子,探讨突变前、后兴安落叶松林的潜在概率分布区的动态变化。结果表明,研究区年均温度在1984年之后发生突变;突变前、后影响兴安落叶松天然林生长概率分布区的主导因子均为DD>5℃、MWMT和HCMD,且3个因子的累积贡献率均达到85%以上,在突变后主导因子中贡献率最大的因子由>5℃积温(40.21%)转变为最暖月均温(40.29%),这2个时期温度的累积贡献率均高于降水;气候变暖使得兴安落叶松林的潜在气候生长概率分布区整体呈现北移的趋势,且不同概率分布区变化趋势具有差异性。兴安落叶松林不存在区、中概率区和高概率区的面积在突变后均减少,而低概率区的面积增加,兴安落叶松林适生区的总面积整体上仍呈现增加的趋势,其总面积由突变前的131.31万km^(2)扩大至135.55万km^(2)。本研究表明气候变暖对兴安落叶松林不同概率分布区的影响具有区域异质性,该研究结果可为未来兴安落叶松林的可持续经营管理提供科学依据。

Global warming has an significant impact on the geographical distribution of forests.Larix gmelinii is an important part of forest ecosystem in Northern China.Therefore,it is necessary to accurately evaluate the impact of climate warming on the geographical distribution of L.gmelinii natural forest,and provide a basis for formulating the sustainable development of the forest.In this study,68 temporary sample circles of L.gmelinii natural forest with a radius of 17.85 m and an area of 1000 m^(2)were established in Northern China based on the method of mechanical point placement.The climate data from 1950 to 2017 were obtained from the Climate AP software,and the regional annual mean temperature abrupt point was checked by M-K.Eight potential climate factor variables affecting the geographical distribution of L.gmelinii forest were selected:i.e.,mean annual temperature(MAT),mean coldest month temperature(MCMT),mean warmest month temperature(MWMT),temperature difference between MWMT and MCMT(TD),mean annual precipitation(MAP),mean annual precipitation in autumn(MAPA),degree-days above 5℃(DD>5℃)and Hargreaves climatic moisture deficit(HCMD),using the MaxEnt model to select the dominant climatic factors affecting the geographical distribution of L.gmelinii forest before and after mutation,and dynamic changes of the potential probability distribution area of the L.gmelinii forest before and after the mutation were discussed.The results showed that the annual average temperature in the study area changed abruptly after 1984.The dominant factors affecting the growth probability distribution of the natural L.gmelinii forest before and after mutation were both DD>5℃,MWMT and HCMD,and the cumulative contribution rates of the three factors were all reached more than 85%.After the mutation,the factor with the largest contribution rate changed from the degree-days above 5℃(40.21%)to the mean warmest month temperature(40.29%),and the cumulative contribution rate of temperature in these two periods was higher than those of precipitation.Climate warming made the potential climate growth probability distribution area of L.gmelinii forest show a northward trend as a whole,and the change trends of different probability distribution areas were different.The area of non existence,medium probability and high probability areas of L.gmelinii forest all decreased after the mutation,while the area of low probability area increased.The total area of L.gmelinii forest of suitable area still showed an increasing trend,and its total area expanded from 1.3131 million km^(2)to 1.3555 million km^(2).This study shows that the impact of climate warming on different probability distribution areas of L.gmelinii forest has regional heterogeneity,and the results can provide a scientific basis for the sustainable management of L.gmelinii forest in the future.