伏牛山地区森林植被动态变化对水热条件的响应

利用环境一号卫星不同时相多光谱数据,提取伏牛山地区不同森林植被类型。借助S-G滤波算法重构2000-2013年MODIS EVI时间序列影像,并结合气温和降水数据,运用线性回归、相关性分析和ANUSPLIN插值等方法分析伏牛山地区不同森林植被类型变动对水热条件的响应方式。结果表明：① 伏牛山地区植被覆盖较高,EVI平均值为0.48,14年来总体呈上升趋势,但不同森林植被类型变化存在明显差异,其中占比例最大的落叶阔叶林的上升趋势最为明显。② 14年来伏牛山地区气温呈升高趋势,气温距平升高速度约为0.27℃/10a,降水距平百分率呈波动增加趋势。③ 伏牛山地区不同森林植被类型EVI变化和气温、降水的相关性存在明显差异,其中常绿阔叶林EVI与气温的相关性最高,常绿落叶混交林与气温的相关性最弱;除常绿落叶混交林与降水主要呈弱正相关外,其余森林植被类型与降水主要呈弱负相关。④ 伏牛山地区森林植被对气温和降水的响应总体上滞后性不明显,仅在局部区域内常绿落叶混交林与气温和降水存在半个月滞后期。

The response of forest dynamics to hydro-thermal change in Funiu Mountain

The response of mountain ecosystem to global change is one of hot topics in the field of forest dynamics. As an important component of mountain ecosystems, to some degree, vegetation coverage change represents the change of land cover, and can provide indication to the global change. The result from the study on the relationship between climate change and forest coverage change within different vertical natural zones could enhance our understanding about the complexity and diversity of mountain ecosystem. It also can reveal the mechanism of mountain ecosystem changes. In recent years, many studies have been conducted to explore the relationship between mountain vegetation change and climatic factors, i.e., temperature, precipitation and so on. It should be noted that, the study area, Funiu Mountain is located at a transitional region between the north subtropical zone and warm temperate zone in China. The plant flora in the Funiu Mountain is complicated and very sensitive to the global climate change. In this study, the HJ-1 satellite data were used to extract forest cover types in the Funiu Mountain region. This paper adopted the S-G filtering algorithm to reconstruct the MODIS EVI (Enhanced Vegetation Index) time-series data form 2000 to 2013. Combined with the temperature with precipitation of the same study period, the response of different forest types to hydrothermal condition changes was analyzed based on the linear regression, correlation analysis, and ANUSPLIN interpolation. The results showed that: (1) the region of Funiu Mountain boasts high forest coverage, and mean EVI reached 0.48, which also showed a gradually ascending trend in recent 14 years. However, some variations were identified among different forest types. Broad-leaved deciduous forest, the dominant forest type in this region showed a noticeable growth trend. (2) There was an increasing trend in temperature in this region during the past 14 years. The increasing rate of temperature departure was about 0.27℃/10a, and the precipitation percentage displayed an ascending trend as well despite of fluctuations. (3) The correlation between EVI and temperature, and precipitation differed noticeably in different forest types. In particular, the evergreen broad-leaved forest showed the highest correlation between EVI and temperature, while the evergreen deciduous mixed forest had the least correlation. Almost all the forest coverage types showed a weak negative correlation between EVI and precipitation, except evergreen deciduous mixed forest, which displayed a weak positive correlation. (4) Generally speaking, the response lag in the mountain towards temperature and precipitation was not obvious, with half-a-month lag in evergreen deciduous mixed forest in some regions.