香溪河消落带人工构建与自然恢复植物群落的差异性

三峡工程修建后所形成的大幅度、反季节水位消涨节律使得库区消落带植物群落及其生态功能严重退化,积极开展消落带植物群落的生态恢复有利于改善库区的生态环境。以香溪河消落带为例,通过对人工恢复地和自然恢复地植物群落的野外调查,研究了不同恢复模式下植物群落的物种组成与结构、物种多样性以及群落生物量特征,以客观评价不同模式对植物群落恢复的影响。结果显示:(1)人工与自然恢复模式下的消落带均形成了以1年生和多年生草本为主的植物群落,其中人工恢复样地中共有草本48种、灌木6种,自然恢复样地中有草本42种,无灌乔木分布;(2)人工恢复地植物群落的物种多样性略高于自然恢复地,自然恢复地植物群落的物种多样性随海拔梯度的增加呈先增加、后减少的变化趋势,而人工恢复地因在消落带上引入了灌木物种呈先增加、后减少、再增加的趋势,植物群落组成在不同海拔梯度也呈相应的变化;(3)2种恢复模式下植物群落生物量均随着海拔梯度的增加而逐步增加,但人工恢复地草本植物群落的生物量显著高于自然恢复地,其中总平均生物量高出27.5%,海拔145 m及165 m处的生物量分别高出62.7%和69.4%。实验表明,人工恢复通过引入灌木物种和增播草本植物,在一定程度加快了消落带的恢复进程,增强了植物群落的稳定性。

Vegetation Community Characteristics of Artificial and Natural Restorations within the Water-Level-Fluctuation Zone of Xiangxi River

The wide amplitude and reverse water-level-fluctuation resulting from the construction of the Three Gorges Project have caused serious degradation of riparian vegetation and ecological function within the water-level-fluctuation zone in the Three Gorges Reservoir Area. Effective vegetation restoration improves the ecological environment. Taking Xiangxi River as a case, this field investigation characterized the species composition, structure, biodiversity and biomass of the artificial and natural plant communities to objectively evaluate the effect of different restoration methods. The results provide scientific evidence to guide vegetation restoration and management in the water-level-fluctuation zone of the Three Gorges Reservoir area. The vegetation demonstration project in the water-level-fluctuation zone has been ongoing since 2009 in the middle section of Xiangxi River with an area of 14 hm2. The natural plant community studied was 2 km from the demonstration project. In August 2014, six vegetation belts were delineated in the two investigation sites along elevation gradients of 145-150, 150-155, 155-160, 160-165, 165-170, 170-175 m and 20 1m×1m plots were randomly set in each vegetation belt. Vegetation species, above ground biomass, height and cover of each plot were recorded and measured, and plant samples were selected for determination of dry weight. Results show that: (1) A riparian plant community composed of annual and perennial herbs developed in the water-level-fluctuation zone of both the artificial and natural restoration plots. There were 48 annual and perennial herbs, and 6 shrubs in the artificial restoration plot. The importance value of 32 vegetation species was higher than 0.5%. A total of 42 annual and perennial herbs were observed in the natural restoration plot, but there were no shrubs and the importance value of only 19 vegetation species was higher than 0.5%; (2) The species biodiversity of the artificially restored community was slightly higher than that of the naturally restored community. The species number, richness index, evenness index, dominance index and diversity index of the artificially restored community were higher by 41.5%, 34.0%, 7.1%, 1.5% and 15.1%, respectively, than those in the naturally restored community. As vegetation belt elevation increased, species biodiversity increased, then decreased in the naturally restored community and decreased, then increased in the artificially restored community because shrubs were introduced on the upper section of the water-level fluctuation zone. Species composition of the community also changed with elevation; (3) The biomass in both restorations increased with elevation. However, the average total biomass of the artificially restored community was significantly higher (27.5%) than that of the naturally restored community; 62.7% higher at 145m and 69.4% at 155m. In summary, introducing shrubs and seeding herbaceous plants in the artificial restoration accelerated the restoration process and promoted the stability of riparian plant community on the water-level-fluctuation zone.