典型亚热带森林生态系统碳密度及储量空间变异特征

以浙江省森林生态系统为研究对象,基于GIS网格布点,采集了838个森林样地样本(土壤、枯落物等),结合浙江省森林资源监测中心相关数据,利用地统计学和Moran's I相结合的方法系统研究了浙江省森林生态系统碳密度及碳储量空间变异特征。结果表明:浙江省森林生态系统平均碳密度为145.22 t/hm~2,其中森林植被、土壤、枯落物和枯死木层碳密度分别为27.34、108.89、1.79、1.38 t/hm~2。克里格空间插值和局部Moran's I指数结果表明碳密度空间分布规律呈现从西南向东北方向逐渐递减的趋势,与浙江省地形、地势较为一致,受海拔、树龄、森林类型、台风气候等自然因素和人类活动共同影响。浙江省森林生态系统碳储量为877.19 Tg C,森林植被、土壤、枯落物和枯死木层碳储量分别为203.88、656.20、10.84、6.27 Tg C,分别占总碳储量的23%、75%、1.3%、0.7%。在浙江省森林生态系统碳储量空间分布格局中,土壤层是森林生态系统中最大的碳库,约是森林植被层的3.22倍,是整个浙江省森林生态系统碳储量最主要的贡献者。浙江省森林资源丰富,大多数森林仍处于中幼龄林阶段,碳密度水平较低,但是中幼龄林生长速度较快,加强对全省中幼龄林的健康管理,是未来整体提升浙江省森林生态系统固碳潜力的关键。

Spatial variation characteristics of carbon density and storage in forest ecosystems in a typical subtropical region

Spatial pattern information of carbon density and storage in forest ecosystems plays an important role in the evaluation of carbon sequestration potentials and healthy forest management. Forest vegetation carbon, soil organic carbon, forest litter carbon and dead tree carbon are the four main carbon pools in forest ecosystems. Most of previous studies on carbon density and storage in forest ecosystems are based on the continuous forest inventory system in China or ecosystem models; however, there is little information on the spatial variation of forest ecosystems. Compared to traditional research methods, geostatistical methods combined with kriging spatial interpolation and Moran''s I have been regarded as an effective tool to explore spatial variation, which have been successfully used to investigate the spatial variability of environmental variables and to incorporate this information into mapping. Therefore, it is widely applied to analyze spatial heterogeneity of forest and soil variables. In 2012, based on the annual data from the Forest Resources Monitoring Center in Zhejiang Province, a total of 838 forest sample plots were established based on a 4 km (south-north)×6 km (east-west) grid system in Zhejiang Province, and the area of each plot was 0.08 hm². The portable global positioning system (GPS) was used to record the longitudes and latitudes. In this study, we analyzed the spatial variation characteristics of carbon density and storage of forest ecosystems in Zhejiang Province using geostatistical methods and Moran''s I. The results showed that the average carbon density of forest ecosystems in Zhejiang Province was 145.22 t/hm², and the forest vegetation layer, soil layer, forest litter layer, and dead tree layer carbon densities were 27.34 t/hm², 108.89 t/hm², 1.79 t/hm², and 1.38 t/hm². Kriging spatial interpolation and Local Moran''s I showed that the spatial distribution of carbon density gradually decreased from southwest to northeast, similar to topographic changes in Zhejiang Province, which was influenced by both natural factors such as altitude, forest age, forest types, typhoon climate, and human activities. The carbon storage of forest ecosystems in Zhejiang Province was 877.19 Tg C, of which 203.88 Tg C was in the forest vegetation layer, 656.20 Tg C in the soil layer, 10.84 Tg C in the forest litter layer, and 6.27 Tg C in the dead tree layer, accounting for 23%, 75%, 1.3%, and 0.7% of the total carbon storage, respectively. The soil layer was the largest carbon pool in forest ecosystems, which was about three times as large as the forest vegetation layer, and which was the most important contributor to the carbon storage of forest ecosystems in Zhejiang Province. There are abundant forest resources in Zhejiang Province; most of the forests are young and middle-aged forests, which account for 76.76% of the total forest area in Zhejiang Province, and the young and middle-aged forests often have relatively low carbon density, but grow fast. Therefore, we should strengthen the healthy management of young and middle-aged forests and enhance the carbon sequestration potentials of forest ecosystems in Zhejiang Province in the future, in order to regulate the global carbon cycle, mitigate the increase in atmospheric CO₂ concentrations, and maintain global climate.