丘陵陡坡荒山灌木草丛及其造林地生态系统碳库的分配格局

植被恢复往往有利于提高生态系统的碳储量,但对南方丘陵陡坡荒山灌木草丛造林后如何影响生态系统碳库及其分配格局仍知之甚少。选取江西泰和典型丘陵陡坡(>25°)荒山灌木草丛和马尾松(Pinusmassoniana)造林19年后的林地为对象,开展上、中、下坡0～75cm土壤层和植物体碳储量的对比研究。结果表明,造林地土壤容重低于灌木草丛,土壤石砾含量与土壤碳含量和碳密度呈显著负相关,表明造林有利于改善土壤物理结构;石砾含量影响土壤碳积累。荒山灌木草丛和马尾松林土壤碳含量和碳密度均表现为随土壤加深呈下降的趋势(P<0.05),但上、中、下坡的变异规律不一致,且2种生态系统之间差异不显著。荒山灌木草丛和马尾松生态系统碳储量分别为52.85,111.31t/hm2,均表现为自上、中坡至下坡呈增加的趋势;灌木草丛和马尾松林中的植物体分别占生态系统碳储量的11.2%和59.5%。灌木草丛马尾松造林碳年均增汇3.08t/(hm2.a),林分生物量的积累是造林增汇的直接原因;推断种植耐瘠速生树种是提高困难立地造林碳增汇的有效途径。

The Pattern of Ecosystem Carbon Stock in Steep Slope Wild Shrubs and Neighboring Forest Plantations in Hilly Red Soil Area

Vegetation restoration is generally helpful to increase the ecosystem carbon stock,however the influences of wild shrubs afforestation on the amount and distribution pattern of ecosystem carbon stock in steep slope land are few understood.Wild shrubs and neighboring masson pine(Pinus massoniana) plantations of 19-year old were selected to study carbon stocks in different soil depths and plant modulates at upper,middle and lower slope positions in typical hilly steep slope land of Taihe county,Jiangxi province.The results showed that soil bulk density was lower in pine plantation than shrubs,and soil stone percentage negatively correlated with soil carbon concentration and density,which indicated that afforestation could improve soil physical structure,and soil carbon accumulation might be influenced by soil stone percentage.Soil carbon concentrations and stocks decreased with increasing depths in both shrubs and masson pine plantation,and their variability among upper,middle and lower slope positions varied with ecosystem types,but no differences in amounts were found between two ecosystem types.Ecosystem carbon stocks were 52.85,111.31 t/hm2 in shrubs and masson pine plantation,respectively,and both showed increasing tendency from upper,middle to lower slope positions.Meanwhile,the carbon stock in plant modulates to the total carbon stock was 11.2% and 59.5% in shrubs and masson pine plantation ecosystems,respectively.In sum,average carbon sink afforested masson pine on shrubs was 3.08 t/(hm2·a),and the direct reason of afforestation carbon sink was the accumulation of forest plant biomass.It was suggested that planting fast-growing trees would be an efficient approach of carbon sink during the afforestation on poor stand condition.