三峡水库奉节以东秭归和巫山段消落带植物群落动态特征

基于2008—2012年对三峡水库奉节以东秭归和巫山段消落带固定样地不同海拔区段植物群落的5a定位监测,研究消落带植物群落的物种组成、优势植物、植物生活型和物种多样性的动态变化,结果表明:1)截止2012年,消落带海拔156—172 m区段共经历了4次水库水位涨落。经历首次后(2009年),消落带原生植物由55科147种减少到18科33种,经历4次后(2012年),减少到14科39种。与经历水库水位涨落前(2008年)比较,经历首次后的科数减少了67.3%,种数减少了77.6%;经历4次后的科数减少了74.5%,种数减少了73.5%。在消落带原生植物减少的同时,出现了许多"新"植物。经历首次后出现了49种,经历4次后出现了23种,分别占调查当年样地植物种类总数的59.8%和32.9%。海拔172—175 m区段共经历了2次水库水位涨落,消落带原生植物由40科91种(2008年)减少到了13科20种。与经历水库水位涨落前比较,科数减少了67.5%,种数减少了78.0%。出现"新"植物21种,约占调查当年样地植物种类总数的44.7%。通过对历次调查中消落带植物"消失"和"出现"的数量比较表明,消落带植物对经历首次水库水位涨落的反应最为敏感,此后,虽又经历过几次水库水位涨落,但其变化速率趋于减小。2)不同海拔区段、不同生态适应型植物的"消长"动态和优势种组成不完全相同。海拔156—172 m区段,经历4次水库水位涨落后,在消落带植物群落中占优势的草本植物种为菊科(Compositae)的鬼针草(Bidens pilosa)、禾本科(Gramineae)的狗牙根(Cynodon dactylon)、毛马唐(Digitaria chrysoblephara)、狗尾草(Setaria viridis)、莎草科(Cyperaceae)的碎米莎草(Cyperus iria),占优势的灌木树种为漆树科(Anacardiaceae)的盐肤木(Rhus chinensis)和大戟科(Euphorbiaceae)的算盘子(Glochidion puberum);在海拔172—175 m区段,除鬼针草、毛马唐仍为优势种外,还增加了大戟科的湖北算盘子(Glochidion wilsonii),马鞭草科(Verbenaceae)的黄荆(Vitex negundo),葡萄科(Vitaceae)的五叶地锦(Parthenocissus quniquefolia)等树种。3)消落带植物群落的优势生活型为一年生和多年生草本;物种多样性随着水库水位涨落次数的增加总体变化呈减少趋势。4)三峡水库水位周期性涨落导致消落带发生水陆环境交替变化,不同生态适应型植物对变化生境的适应能力有所不同,是消落带植物群落发生变化的主要驱动因素。

Plant community dynamics in the Hydro-fluctuation Belt of the Three Gorges Reservoir at the Zigui and Wushan Section, East of Fengjie County, China

The plant community growing in the hydro-fluctuation belt is an important component of reservoir management, playing a significant role in the maintenance of riparian ecosystems and ecological functioning. Obtaining timely and accurate data on plant community dynamics could provide theoretical and practical information for vegetation restoration and reconstruction in the Three Gorges Reservoir. This study collected data over 5 years (2008-2012) for the plant community from four permanent monitoring plots at different elevations in Zigui and Wushan section of the Three Gorges Reservoir (East of Fengjie County). The dynamic characteristics, plant community composition, dominant plants, plant life forms, and species diversity were studied. The results indicated that compared to 2008, the elevation from 156 to 172 m was subject to water level fluctuation on one occasion by 2009 and four occasions by 2012. The number of native plants declined from 147 species in 2008 (belonging to 55 families) to 33 species (belonging to 18 families) by 2009;the rate of reduction for families and species was 67.3% and 77.6%, respectively. The number of native plants declined to 39 species (14 families) by 2012, with the rate of reduction for families and species being 74.5% and 73.5%, respectively. However, 49 (by 2009) and 23 (by 2012) "new" species appeared during the study period, raising the total number of species by 59.8% and 32.9%, respectively, in certain sampled plots. The elevation from 172 to 175 m was subject to water level fluctuations on two occasions by 2012. The number of native plants declined from 91 species (40 families) to 20 species (13 families). The rate of reduction was 67.5% and 78.0%, respectively. However, 21 "new" species accounted for about 44.7% of all sampled plant species. Based on the comparison of several survey results on the number of "disappeared" and "appeared" plant species, the results indicated that the most sensitive response of the plant community was to the first water level fluctuation. Subsequently, even though the plant community was subject to several water level fluctuations, the rate of change declined. The "growth" dynamics of ecologically adapted plants and the composition of dominant species differed at different altitudes. At an altitude of 156-172 m, the dominant herbaceous species were Bidens pilosa (Asteraceae), Cynodon dactylon (Poaceae), Digitaria chrysoblephara (Poaceae), Setaria viridis (Poaceae), and Cyperus iria (Cyperaceae). The dominant shrub species were Rhus chinensis (Anacardiaceae) and Glochidion puberum (Euphorbiaceae). At an altitude of 172-175 m, Glochidion wilsonii (Euphorbiaceae), Vitex negundo (verbenaceae) and Parthenocissus quniquefolia (Vitaceae) became dominant shrub species, except for Bidens pilosa, and Digitaria chrysoblephara. Annual and perennial herbs were the dominant plant life-form in the hydro-fluctuation belt. Species diversity decreased as the number of water level fluctuations increased. Periodic fluctuation in the water level of the Three Gorges Reservoir led to flooding-drying habitat alterations. The adaptability of different ecological plants to changing habitats was the main driving factor of plant community change.