Forest ecosystem, as a major body of terrestrial ecosystem, holding 85% of terrestrial biomass plays an irreplaceable role in the global carbon cycle and consequently in global climate change. Although China has the smallest forest area among mid-latitude nations, it contains a relatively large forest vegetation carbon pool and high forest carbon density as a result of intensive forestation programs and forest managements. Thus, natural reserves are the most effective areas for forest management, and they often complement some environmental goals including protection of carbon sink, and should not be ignored in regional carbon researches. In former studies, the capability, distribution and changing of carbon resource and sink are basic scientific issues in regional carbon sequestration researches, and these issues are closely related to vegetation distribution, composition, carbon density and other forest statuses. Jinyun Mountain is one of the national natural reserves in China. As the mountain holds well-protected subtropical evergreen broad-leaved forest (EBF) accompanied by coniferous forest (CF), mixed coniferous and evergreen broad-leaved forest (MCB), etc., it has been concerned by many researchers. Consequently, studying the spatial distribution of vegetation and carbon density of Jinyun Mountain Nature Reserve can provide important basic data for forest ecosystem operation, carbon pool management and even regional carbon sequestration researches.
In this study, high-resolution remote sensing image and 1∶10 000 relief maps were used to generate Jinyun vegetation map and digital elevation model respectively, combining with non-destructive method to acquire forest biomass by field investigation and the data of carbon content and biomass regression models from the published papers. And then, the spatial characteristics of vegetation and carbon density in Jinyun Mountain Natural Reserve were analyzed by ArcGIS. The results showed that CF was the dominating forest stand, followed by SH (shrub). The vegetation area ranged as CF (30%) > SH (21%) > MCB (16%) > NS (neosinocalams stand, 11%) > EBF (6%) > MCN (mixed coniferous and neosinocalsms stand, 5%) > MBS (moso bamboo stand, 4%). The average vegetation carbon density in Jinyun Mountain was 50.45 Mg/hm², which was higher than the average level in China, ranged as MCB (74.23 Mg/hm²) > CF (62.97 Mg/hm²) > EBF (62.65 Mg/hm²) > MCN (59.84 Mg/hm²) > NS (48.72 Mg/hm²) > MBS (47.88 Mg/hm²) > SH (10.66 Mg/hm²). Moreover, vegetation and carbon density had clear spatial variations with altitude, slope and aspect. CF dominated in altitude higher than 500 m and slope > 15°, but the shrub was the other way around. The carbon density of MCB and EBF increased with the increasing of altitude and slope. EBF had a large area in the northwest aspect, and MCB had a large distribution in the north, northwest, east and southeast aspects. NS and MCN were the dominating forest stand in the south relatively. CF, dominated with Pinus lanceolata, and SH were at primary stage of forest recovery succession in the Jinyun Mountain. The results indicate that the actual carbon sequestration of Jinyun Mountain is still much lower than the potential value of the zonal climax vegetation in this subtropical area. As we find the carbon storage and density are negatively correlated with human disturbance, forest reserve managements, such as enclosure of forest region, might contribute to conserve and sequester carbon in Jinyun Mountain.