Subjects: Biology >> Botany >> Plant ecology, plant geography submitted time 2016-05-03
Abstract： Aims Carbon sequestration is the basic function and most primary service of forest ecosystems, and plays a vital role in mitigating the global climate change. However, carbon storage and allocation in forest ecosystems have been less studied at regional scales than for forest stands, and the results are subject to uncertainty due to inconsistent methodologies. Here, we aimed at relatively accurate estimates of forest carbon storage and sequestration rate at a provincial scale (regional) based on plot surveys of both stand biomass and soils over the province. Methods Based on the area and distribution of major forest types, 212 sampling plots, covering different age classes and originality (natural/planted), were surveyed in Gansu Province in northern China. Field investigations were conducted for vegetation layers (trees, shrubs, herbs and litter), soil profiles, and sampling of both plant materials and soils for laboratory analyses. Regional carbon storage was calculated by up-scaling the carbon densities of all forest types with their corresponding areas. Carbon sequestration rate was estimated by referring the reports of national forest inventory for different periods. Important findings Forest carbon storage at the provincial scale was 612.43 Tg C, including 179.04 Tg C in vegetation biomass and 433.39 Tg C in soil organic materials. Specifically, natural forests contributed largely and stored 501.42 Tg C, approximately 4.52 times that of the plantations. Vegetation carbon density in both natural forests and plantations showed increasing trend with the increase in age classes, and the natural forest showed a higher value than the plantation at the same age class. Soil carbon density also increased along the age classes in natural forests, whereas the highest value in plantations appeared at pre-mature stage. Weighted average of regional vegetation carbon density was 72.43 Mg C?hm–2, with 90.52 and 33.79 Mg C?hm–2 in natural forest and plantations, respectively. In 1996, vegetation biomass stored 132.47 and 12.81 Tg C in natural forests and plantations, respectively, and the values increased to 152.41 and 26.63 Tg C in 2011, with the mean carbon sequestration rates of 1.33 and 0.92 Tg C?a–1. Given that young and middle-aged forests account for a large proportion (62.28%) of the total forest area, they are expected to exert substantial potential of carbon sequestration in the province.
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