基于TM NDVI的武功山山地草甸植被覆盖度时空变化研究

以江西省武功山山地草甸为研究区,基于4期TM(Thematic Mapper,专题测图仪)卫星遥感影像,提取NDVI(Normalized Difference Vegetation Index,归一化植被指数),采用像元二分模型,运用ENVI 5.1和Arc GIS 10.0软件计算得到武功山山地草甸的植被覆盖度分布格局及动态变化。研究结果表明:(1)研究期间山地草甸面积减少了9.72%,呈递减趋势。20年来随着武功山风景区成立—旅游业发展—山地草甸生态修复,山地草甸植被覆盖度增加和减少交替,总体呈上升趋势;(2)山地草甸植被覆盖度呈现东南高西北低的空间分布特征。低覆盖度草甸区集中在武功山山脉的西北侧坡面的崖壁和部分山脊线上,而高覆盖度草甸区多分布在武功山山脉的东南坡面;(3)研究区山地草甸退化与改善并存,山地草甸最北端和白鹤峰-九龙山区域的东南坡、南坡低海拔处植被总体呈退化特征;发云界南部的东坡植被总体呈现改善特征。研究期间山地草甸退化面积比改善面积多出1.78%。(4)山地草甸植被覆盖度的分布格局和地形因子存在较高的相关性(P0.05):植被覆盖度随着坡向的变化而呈规律性的变化,总体上山地草甸植被覆盖度的分布为阳坡平坡阴坡;植被覆盖度先是随着坡度的上升而升高,在坡度15°—25°时达到峰值,然后随坡度的上升而下降,在45°—90°最低;植被覆盖度随海拔升高呈波浪式下降,1000—1200m最高,在主峰山顶海拔1800—1918.3m最低。遥感解译检验结果证明采用此方法对大面积山地草甸覆盖度分布及变化进行反演可行而准确;在后续研究中将采用不同季相的多期影像数据提取NDVI对研究区植被覆盖度进行长期监测,以便更准确可靠地分析山地草甸演化过程和趋势。

Spatial-temporal dynamics of upland meadow coverage on Wugong Mountain based on TM NDVI

Taking the upland meadow on Wugong Mountain as a study area, and based on the TM (Thematic Mapper) remote sensing image, this study used ENVI 5.1 and ArcGIS 10.0 software to calculate the vegetation coverage distribution pattern and to analyze the dynamic changes to upland meadow on Wugong Mountain. The results indicated that the area showed a progressively decreasing trend that fell by 9.72% during the study period. During the past 20 years, with the establishment of the Wugong Mountain Scenic Area and the development of tourism, the ecological restoration of upland meadow has meant that vegetation coverage has increased;the vegetation coverage distribution characteristics showed that vegetation was high in the southeast and low in the northwest. The low vegetation coverage meadow area was concentrated on a precipice on the northwest slope and on part of the ridge line, whereas meadow coverage was high on the southeast slope.The degradation and improvement of upland meadow coexisted in the study area. It was degraded in the northernmost end of the upland meadow and the low altitude area of the southeast and south slopes of Bai Hefeng-Jiu Longshan area; the vegetation showed improvement on the southern slope of Fa Yunjie. At the same time, the distribution pattern of vegetation coverage and terrain factors were closely related (P < 0.05):vegetation coverage showed regular change with the change in aspect.Its distribution was in the order:sunny slope > flat area > shady slope.Vegetation coverage rose firstly with the rise of slope and peaked at 15°-25°, but then fell along with the rise of the slope.It reached its lowest value at 45°-90°.Vegetation coverage showed a wavelike decline with increasing altitude, and achieved a maximum value at an altitude of 1000-1200m, and a minimum value at the peak region of 1800-1918.3m. This research showed that the methods employed were feasible and accurate and could be used to investigate large area distributions and variations in mountain meadow coverage. However in order to analyze the evolution and trends on upland meadow more accurately and reliably, the image data for different season should be used in a follow-up study that includes the long-term monitoring of vegetation coverage in the study area.