上海大金山岛植被分类与制图——基于网格化清查方法

网格化清查方法有助于准确诊断一个地区的植被性质,并为探索植被分类方法提供支持。该研究以上海大金山岛为对象,借助航拍影像等间距地将其划分为140个清查网格(40 m × 40 m),按照统计样方法逐网格调查植物群落特征,综合运用列表法和双向指示种法,进行植被分类并绘制现状植被图。按照新修订的植被三级分类系统进行分类:一级单位根据植被型,大金山岛植被划分为落叶阔叶林、常绿落叶阔叶混交林、常绿阔叶林、落叶阔叶灌丛、常绿落叶阔叶混交灌丛、常绿阔叶灌丛和草丛; 二级单位根据优势种和植物区系特征,可划分出15种群丛或群落类型; 三级单位根据群落年龄和外貌可划分为22种群落类型。以上结果表明,大金山岛不仅是上海市物种多样性最高的区域,也拥有华东海岛最典型、最多样的自然半自然森林群落。就植被状态而言,地带性森林群落处于演替中后期,但少数次生植被处于演替前期,且面临着猴群干扰导致的植被发育停滞不前等生态问题。关于植被分类方法,网格化清查方法可充分揭示植物群丛连续性中包含间断性和过渡性群落的现象。

Vegetation classification and mapping of Dajinshan Island: A grid inventory-based approach

The grid inventory-based approach is helpful for diagnosing vegetation properties of a given region, and provides support to explore the methods of vegetation classification. In this study, Dajinshan Island in Shanghai City was selected to conduct vegetation classification and vegetation mapping according to the methods of Tabulation and Two-Way Indicator Species Analysis. We divided this island into 140 regular grids(40 m × 40 m)based on an unmanned aerial vehicle image, and then surveyed community composition by using the Braun-Blanquet method and quadrat-based census across the grids. Under the newly revised three-level vegetation classification system, the first level of classification(i.e., vegetation type)included deciduous broad-leaved forest, evergreen and deciduous broad-leaved mixed forest, evergreen broad-leaved forest, deciduous broad-leaved shrubland, evergreen and deciduous broad-leaved mixed shrubland, evergreen broad-leaved shrubland, and grassland. According to the dominant species and floristic characteristics, the second level of classification included 15 types of associations or communities. The third level included 22 types of communities based on physiognomy and community age. These results indicate that Dajinshan Island is not only a species-richest region in Shanghai, but also possesses the most typical and diverse natural or semi-nature forest communities across islands in East China. In terms of vegetation status, zonal forest communities develop to the middle and late successional stages, but a few secondary vegetation still stop in the early successional stage, which encounter to the ecological problems such as development stagnation caused by monkey disturbance. With respect to the vegetation classification methods, the grid inventory-based technique can fully reveal the phenomena of intermittent and transitional communities in the continuity of flora.