蒙古高原植被返青期对气候、积雪、土壤水变化的响应特征研究

Response Characteristics of Vegetation Reforestation Period to Climate,Snow Cover and Soil Water in Mongolian Plateau

植被返青期是植被生长过程中的重要阶段之一,探究植被返青期的变化及其影响因素具有重要意义。目前,将积雪与气温、降水等结合,从而探讨植被返青期影响机制的研究还比较少,因此研究基于MODIS NDVI、积雪产品以及ERA-5再分析等数据,采用累计NDVI的Logistic曲线曲率极值法、趋势分析、相关分析以及敏感性分析等方法,探究2001~2018年蒙古高原植被返青期时空变化特征及对气候、积雪、土壤水变化的响应机制。主要结果表明:近18 a蒙古高原植被返青期平均在123 d左右,整体呈现出不显著推迟趋势。其中西南地区和大兴安岭地区返青期最早,萨彦岭和杭爱山返青期最晚。蒙古高原返青期与积雪覆盖度、积雪日期、积雪终日呈显著正相关的区域均>30%,与融雪期温度呈显著负相关的区域>25%,与积雪期降水、土壤水分及积雪初日的相关性较弱。研究得到积雪对于植被返青期的影响显著,其因子敏感度排序为:积雪覆盖度(0.467)>积雪日期(0.184)>融雪期温度(0.113)>积雪终日(0.028)。

The vegetation greening period is one of the important stages in the vegetation growth process,so it is of great significance to explore the change of vegetation greening period and its influencing factors.At present,there are few studies that combine snow cover with temperature and precipitation to explore the influencing mechanism of vegetation greening period.Therefore,based on MODIS NDVI,snow cover products and ERA-5 reanalysis data,this paper adopts the Logistic curve curvature extreme value method,trend analysis,correlation analysis and sensitivity analysis of accumulated NDVI.To explore the spatio-temporal variation of vegetation greening period in Mongolia Plateau from 2001 to 2018 and its response mechanism to climate,snow cover and soil water change.The main results show that the average greening period of the Mongolian plateau in recent 18 years is about 123d,and the overall trend is not significantly delayed.The earliest greening stage was found in the southwest region and the Greater Khingan Mountains,and the latest was found in the Sayan Mountains and Hangai Mountains.The regions with significant positive correlation with snow cover,snow cover date and snow cover total day were all>30%,while the regions with significant negative correlation with temperature during snowmelt period were>25%,and the correlations with precipitation,soil moisture and snow cover first day were weak.The results showed that snow cover had a significant effect on the greening stage of vegetation,and its factor sensitivity was ranked as follows:snow cover(0.467)>snow cover date(0.184)>temperature during snowmelt period(0.113)>snow cover day(0.028).