黄土区露天煤矿排土场刺槐×油松复垦模式17～22年间群落生长动态

Community growth dynamics of Robinia pseudoacacia × Pinus tabuliformis reclamation pattern from the 17^(th) to 22^(nd) year in an open-pit coal mine waste dump in Loess area

为了解矿区复垦土地人工重建植被的群落生长动态,基于2010年和2015年对安太堡露天煤矿排土场0.8 hm^2"刺槐(Robinia pseudoacacia)×油松(Pinus tabuliformis)"复垦模式动态监测样地的两次调查数据,从物种组成、数量特征、径级结构等方面分析了人工植被复垦17~22年间群落生长动态特征。结果表明:5年间,群落的树种组成较为稳定,优势种仍为刺槐,但其重要值大幅下降,入侵种榆树的重要值增长较快;草本层植物由44种减少到35种,在优势成分上呈现出由1年生或1~2年生向多年生、旱中生向中生演替的趋势;样地内胸径≥1 cm的独立个体数由1530株增加到2854株,其中死亡194株,新增1518株,每年死亡率和每年增补率分别为2.71%和15.18%;死亡量最大的树种是刺槐,增补量最大的是榆树;群落总的胸高断面积由10.99 m^2·hm^(-2)增加到14.19 m^2·hm^(-2),其中因死亡而减少的胸高断面积为0.65 m^2·hm^(-2),新增的胸高断面积为3.85 m^2·hm^(-2),以刺槐的损失量和新增量为最多;刺槐和油松的平均胸径增加,榆树的平均胸径减少;小径级个体死亡量较大,大径级个体死亡量较小;不同树种的死亡个体径级分布基本类似于2010年该树种的径级分布;刺槐和油松的种群大小变化率分别为-2.88%和-0.24%,均呈小幅度负增长,榆树的种群大小变化率(33.37%)在5%以上,属于快速增长的种群。从群落5年间的物种组成和结构变化来看,不同树种的死亡率和增补率各异,群落的物种成分和结构变化较大,复垦生态结构尚不稳定。

Vegetation restoration is effective for ecological reclamation of mining areas. To study the community growth dynamics of artificial vegetation on reclaimed land in a mining area, a 0.8 hm^2 permanent monitoring plot was established in 2010, with mixed forestry of locust trees（Robinia pseudoacacia）and Chinese pine（Pinus tabuliformis）at the Antaibao open-pit coal mine in Shanxi Province. Based on two datasets obtained in 2010 and 2015, we analyzed the dynamics of species composition, quantity, and DBH（Diameter at Breast Height）structure of the trees（DBH≥1 cm）from the 17^th to 22^nd year since reclamation. During this five-year period, the composition of the tree species was found to be relatively stable. The dominant species in the community continues to be R. pseudoacacia, albeit with significantly decreasing importance in contrast to the increasing importance of the invasive elm（Ulmus pumila）. The herbaceous species reduced from 44 to 35, with the community composition tending to succeed from annual/biennial to perennial and from intermediate mesophyte to mesophyte. The number of trees（DBH≥1 cm）increased from 1530 to 2854 stands, of which 194 died and 1518 emerged, with an annual mortality and emergence rate of 2.71% and 15.18%. The highest mortality and emergence were each observed among the R. pseudoacacia and U. pumila. The basal area of the trees increased from 10.99 m^2·hm^-2 to 14.19 m^2·hm^-2, in which death led to the reduction of 0.65 m^2·hm^-2,while 3.85 m^2·hm^-2 was newly added. Interestingly, both, the largest decrease and increment of the basal area were observed in R. pseudoacacia. The mean DBH increased for R. pseudoacacia and P. tabuliformis, while it decreased for U. pumila. The smaller individuals had a higher mortality as opposed to the larger ones. The DBH distribution of the dead tree species was similar to that of living tree species in 2010. The population size of R. pseudoacacia and P. tabuliformis declined slightly, each at an annual rate of-2.88% and-0.24%, respectively, while that of U. pumila increased at an annual rate of at least 5%, with a significantly rapid growth of 33.37% in 5 years. With respect to the species composition and structure, great variations were observed in the mortality and emergence rates among different species, while considerable fluctuations were noted in community species and structure, indicating the instability of the reclaimed ecosystem.