大兴安岭呼中林业局森林景观格局变化及其驱动力

Forest landscape change and driving forces in Huzhong Forest Bureau of Daxing'anling in China

以大兴安岭呼中林业局为研究区,利用TM数据、森林资源清查数据和采伐统计资料,结合野外调查,以GIS为技术手段,剖析研究区1989～2000年景观变化,结果表明该区主要景观类型为针叶林、针阔混交林和阔叶林,这3种类型面积总比例达90%以上,其他景观类型面积比例小于10%,主要有荒草地、火烧迹地、采伐迹地、沼泽、居民点和道路.10a间景观由原有的大面积连续的针叶林为基质、小面积的阔叶林和针阔混交林斑块散布其中的格局,转变成大面积针阔混交林为基质的格局.研究区1989年是成过熟林、高公顷蓄积量、高郁闭度占优势的景观,2000年中幼龄林、低公顷蓄积量和低郁闭度森林面积增大,并趋于连续,形成低质量的相对均质化的景观.最后,结合历史资料,通过比较分析火烧、人工更新、土地利用和人为采伐活动这几种主要驱动力的特征,论证了采伐活动在该地区景观变化中所发挥的主导作用.

Landscape change and its driving forces are always considered one of the major issues in landscape ecology. Daxing＇ anling is one of the most important timber supply area in China. Since late 1960, Forest landscapes have been changed greatly due to harvesting and ecological functions have degraded substantially. We investigated the landscape pattern of Huzhong Forest Bureau, one part of Daxing＇ anling using TM data and forest stand map. The paper aims at exploring how and why the landscape changed from 1989 to 2000. The results show that main landscape types including coniferous forest, broad-leaved forests and coniferous-broadleaved forests cover more than 90% of the total area. The other 8 landscape types cover the rest areas and they are grasslands,fire blank, cutting area, wetland and roads. Change in the coniferous was great, decreasing from 47.62% of total landscape in 1989 to 31.49% in 2000. In contrast, coniferous-broadleaved forest decreased from 39.21% in 1989 to 53.37% in 2000. This trend suggests dominant landscape cover converted from large areas of continuous coniferous forests to large area of coniferous-broadleaved forests. Meanwhile, forest ages, timber volumes and canopy closure changed greatly. From 1989 to 2000, the landscapes dominated by mature and old-growth, large timber volume and high canopy forests turned into landscapes dominated by mid-aged, small timber volume and low canopy forests. Landscapes have been transformed from a high quality homogeneous state to a low quality homogeneous state, Both nature and human influenced landscapes in the study area. We use historical data to compare several driving forces including timber harvest, fire disturbance, afforestation, and residential build-up by the extent, intensity and frequency. We found that forest harvesting is the main driving force for the landscapes change in Huzhong Forestry Bureau from 1989 to 2000. This study revealed the relationships among landscape, ecological processes and human activities. It also revealed the intensities, directions and rates of landscape change caused by different driving forces. Additionally, this study can provide scientific basis for forest management at landscapes scales.