长沙市4种人工林生态系统碳储量与分布特征

采用标准地调查和生物量实测方法,研究了长沙市区4种人工林生态系统生物量、碳储量及其分布特征。结果表明:马尾松林、杉木林、毛竹林和杨树林生态系统生物量分别为135.390、100.578、64.497、63.381 t/hm~2;林下植被及死地被物层分别为18.374、22.321、1.847 t/hm~2和2.602 t/hm~2。乔木层林木各器官含碳率为0.405—0.551 g C/g,林下植被层为0.421—0.518 g C/g,死地被物层为0.230—0.545 g C/g,土壤层有机碳含量为15.669—19.163 g C/kg。4种人工林生态系统总碳储量为208.671、176.723、149.168 t/hm~2和164.735 t/hm~2,其中植被层为32.789—67.8661 t/hm~2;死地被物层为0.394—6.163 t/hm~2;土壤层为134.642、116.911、115.985 t/hm~2和126.860 t/hm~2。4种森林年净固碳量为15.167 t hm-2a-1,固定CO_2量55.602 t hm-2a-1。研究结果可为深入研究城市森林碳平衡提供基础数据。

Carbon storage and sequestration in four urban forest ecosystems in Changsha, Hunan

Forests are important contributors to the global carbon (C) cycle because they store large quantities of C in the vegetation and soil, and exchange CO₂ actively with the atmosphere through photosynthesis and respiration. Urban forests are a critical part of green infrastructure that not only maintains the health and quality of life in the cities, but also provides many ecosystem services, such as C sequestration in urban areas. In the present study, the quantity and distribution of vegetation biomass, C content and C storage were investigated in four types of forests (Masson pine forests, Chinese fir forests, Bamboo forests, and Poplar forests) in Changsha City, Hunan Province. The C sequestration capacity was also estimated for the four forest ecosystems. The results showed that the biomass of overstory vegetation was 135.390, 100.578, 64.497, and 63.381 t/hm² in masson pine, Chinese fir, bamboo and poplar forests, respectively. Stem had the highest, whereas fine root had the lowest proportion of overstory biomass among the different organs for all examined forests. The biomass was 18.374, 22.321, 1.847, and 2.602 t/hm² in understory vegetation and litter layers in masson pine, Chinese fir, bamboo, and poplar forests, respectively. On average, C content was found in the range of 0.405-0.551 gC/g in overstory vegetation with specifically ranging of 0.405-0.516, 0.458-0.509, 0.405-0.527, and 0.454-0.551gC/g in masson pine, Chinese fir, bamboo, and poplar forests, respectively. Average C content ranged between 0.421-0.518 gC/g in understory vegetation, 0.230-0.545 gC/g in litter layer, and 15.669-19.163 gC/g in the soil. The C content of soils under the four forest types decreased with increasing soil depth. The total C storage was 208.67, 176.723, 149.17 and 164.74 t/hm² in masson pine, Chinese fir, bamboo, and poplar forest ecosystems, respectively. Of which, the largest proportion of the total C storage was found in the soils that contained 134.64, 116.91, 115.99, and 126.86 t/hm² in the corresponding four forest types, respectively. The next was vegetation component that contained 33.976, 47.871, 32.632, and 66.346 t/hm² in the four studied forests. The litter layer accounted for the least percentage of the total C storage for the four examined forest types with a range of 0.39-6.16 t/hm². On average, the annual C sequestration in the four forest ecosystems was 3.969, 3.420, 6.019, and 1.759 t hm^-2 a^-1 was in masson pine, Chinese fir, bamboo, and poplar forests, respectively. The total C sequestration capacity in the four forest ecosystems (15.167 t hm^-2 a^-1) was roughly equal to 55.602 t hm^-2 a^-1 of CO₂ fixation in the study site. Our results demonstrate the significance of urban forest ecosystems in carbon sequestration to mitigate climate change. The results provide a scientific basis and reference for urban forest planning and management and an accurate estimation of C balances in urban forest ecosystems.