关键词: 梯度分析, 景观格局, 植被景观, 景观指数, 唐家河自然保护区

Abstract: To explore gradient variations of landscape pattern in Tangjiahe nature reserve , the belt transect (width of 2 km and length of 22 km) was set from northwest to southeast on the remote sensing vegetation image by employing GIS technology. Our results indicate that: (1) as a well-developed vegetation type , the woodland distributes widely in the nature reserve
and occupies approximately 91 .65% of the total study area . In detail, the evergreen broad-leaved and deciduous broad-leaved mixed forest is considered as background of landscape in the reserve because of biggest distribution area . In contrast, sub-alpine shrub meadow and farmland have lower heterogeneity degree because of small area and simple patch edge . (2) With space change from northwest to southeast , the landscape indices vary in three different ways at the landscape scale : increasing, decreasing and no consistent trend . In general , value of some indices, such as edge density, mean proximity index, landscape shape index and mean patch fractal dimension , maintains a increasing trend along the belt transect, but the value of mean patch size index and mean nearest neighbor distance index decrease obviously . The other indices such as Shannon′s diversity index, Shannon′s evenness index, largest patch index and interspersion juxtaposition index keep a steady fluctuate . ( 3) On the other hand, secondary deciduous broad-leaved forest , evergreen broad-leaved and deciduous broad-leaved mixed forest, coniferous and broad- leaved mixed forest and coniferous forest are dominant classes at the patch scale , and have obvious peaks in variation of landscape indices value along belt transect in the reserve .

Key words: Gradient analysis