准噶尔无叶豆土壤种子库特征及其对种子萌发的影响

Characteristics of Soil Seed Bank of Desert Plant Eremosparton songoricum and Their Effects on Seed Germination

准噶尔无叶豆(Eremosparton songoricum(Litv.)Vass.)是中亚荒漠特有种,中国的单属种植物类群,稀有种,仅片段化分布在古尔班通古特沙漠风蚀坡地及流动-半流动沙丘上。按照不同微地形条件,于2008年9月、2009年的4月及6月分别对两个自然种群8种微地形条件(A种群为积沙灌丛下、积沙平缓处、风蚀灌丛下和风蚀平缓处4种;B种群为沙丘上部、中部、下部及底部4种)进行土壤种子库取样,并统计萌发季节的自然种群萌发率,同时对比室内萌发率,以研究土壤种子库的时空分布特征及其对种子萌发的影响。结果表明,从9月至次年4月和6月,种群种子库密度逐渐减少。自然状态下沙埋深度0—6cm的种子能够萌发,主要萌发季节(4月)A种群有42%～73.56%的种子、B种群有63.33%～72.73%的种子分布在沙土6cm以下的深度,为"无效种子"。A种群积沙灌丛下种子库密度值最大,但萌发季节的自然种群萌发率为0;B种群的沙丘下部种子库密度较大,但自然种群萌发率仅为4.8%±0.8%。不同微地形条件下沙粒打磨作用(去除种子硬实)和水分条件的差异,是微地形间种子萌发率差异的主要原因。本研究从土壤种子库角度解析自然种群有性更新困难的原因,为该稀有物种的保育提供理论依据。

Eremosparton songoricum（Litv.） Vass.is a rare desert species endemic to Central Asia,and is the only species of the genus of Eremosparton in China,scattering on sand dunes in the Gurbantunggut Desert,Xinjiang,China.To analyse the characteristics of the soil seed bank and their effects on seed germination,E.songoricum were examined by natural soil seed collection and germination experiments both in wild and lab,which were all manipulated in different micro-sites for two populations（smooth sandy area,leeward sides of the shrub,smoothly sand erosion area and windward sides of the shrub for population A in smooth sand land;top,middle,lower,bottom positions of dunes for population B in moving sand dunes） in three different months.The results show that the seed bank densities decline from September to next April and then to June.In natural conditions,seeds germinate only at depths of less than 6 cm of sand-burying.In germinating season of April,there are 42%~73.56% and 63.33%~72.73% of the seeds distributed at depths of more than 6 cm in population A and population B respectively,which are considered as ＂invalid seeds＂.For population A,the seed bank density is the highest in leeward side of the shrub,while its natural germination rate is 0 there;For population B,the seed bank density is the highest in the lower position of dunes,while its natural germination rate is 4.8%±0.8% there.Combined with the lab germination experiments,variation in sand burnishing（breaking the hardness of seeds） and soil water content are the main reasons for the variation of germination rate among micro-sites.