天然固定沙地不同微生境下土壤种子库差异

A comparative study of soil seed banks over different microhabitats in naturally stabilized sandy land

研究了腾格里沙漠东南缘天然固定沙地不同微生境下土壤种子库的种类组成和种子密度。结果表明:(1)灌丛下土壤种子库的物种丰富度大于灌丛边缘和灌丛间裸地。(2)不同微生境中土壤种子密度因物种而异。就距灌丛中心的距离来说,雾冰藜、刺蓬、地锦、虎尾草、虱子草和冷蒿灌丛下土壤中种子多于裸地,无芒隐子草和狗尾草种子裸地多于灌丛下,小画眉草在距灌丛各距离间土壤种子密度差异不显著。(3)就灌丛的不同方向来说,雾冰藜和刺蓬土壤中种子在东南方向最多,地锦和无芒隐子草土壤中种子密度在西南和西北均大于东南,狗尾草的土壤种子密度东北大于西北,虱子草的土壤种子密度在西南方向最大,冷蒿的土壤种子密度在西南方向最小,小画眉草和虎尾草在各方向间种子密度差异不显著。(4)不同微生境中物种的结籽量对土壤种子分布格局的影响力十分有限。种子离开母株后所经历的传播、消耗等过程在很大程度上打乱了植物结籽量的空间样式。

Assessing the differences in seed composition of distinct microhabitats can clarify the relationship between soil seed banks＇ patterns and processes.Knowledge on different seed types＇ specific location may explain the spatial pattern of plant recruitment at the microhabitat scale.In this regard,the soil seed bank composition and its density at the southeast edge of the Tengger Desert in Northern China were studied over 12 microhabitats around the Caragana korshinskii shrub.Specifically,we selected 40 individual adult Caragana korshinskii plants in the region and established four compass orientations（at 90° intervals,i.e.northeast [NE],southeast [SE],southwest [SW],and northwest [NW]） centered on each chosen plant.In each of the four orientations,a 3m sample line was established from the center of the shrub to the interspace between shrubs.Along each line,three sampling locations were positioned at distances of 0.5m（under the canopy）,1m（the canopy edge）,and 3m（the interspace） from the shrub center.A number of conclusions can be drawn from this study.（1） Species＇ richness under the canopy was superior compared to that of species situated at the canopy＇s edge and the interspace.（2） Soil seed density over different microhabitats varied with species.For the distance gradients from the shrub,Bassia dasyphylla,Salsola ruthenica,Euphorbia humifusa,Chloris virgata,Tragus berteronianus,and Artemisia frigida possessed more seeds under the canopy than in the interspace;Setaria viridis and Cleistogenes songorica yielded more seeds in the interspace than under the canopy,while Eragrostis minor displayed no significant differences in distances.（3） For different orientations,Bassia dasyphylla and Salsola ruthenica contained more seeds in SE,Euphorbia humifusa and Cleistogenes songorica contained more seeds in SW and NW than in SE,Setaria viridis had more seeds in NE than in NW,Tragus berteronianus had more seeds in SW,Artemisia frigida had the least number of seeds in SW with Eragrostis minor,and Chloris virgata had no significant differences in distinct orientations.（4） Seed production in different microhabitats wielded little influence on the spatial distribution patterns of soil seeds.The dispersal and consumption after seed dispersal from the maternal parent significantly disturbed the original patterns of seed production.