青藏高原东部尕海湿地种子库沿水位梯度的分布格局

Heterogeneity in the seed bank along the water gradient of the Gahai Lake wetland on the eastern Qinghai-Tibet Plateau

近年来,青藏高原湿地生物多样性逐渐降低、植被严重退化.种子库研究是开展受损湿地植物群落恢复的重要手段之一,而种子库的空间分布格局对研究地表植被的分布格局具有指导作用.本研究选取青藏高原东部尕海湿地作为研究地点,沿水位梯度设置沉水区以及交错区2个区域,在沉水区设置3条样线,交错区设置2条样线,探讨不同水位梯度下种子库空间分布格局,以期为青藏高原东部退化湿地种子库湿地植被修复的取样策略提供依据.基本特征结果表明,不同样线间、不同区域间平均种子密度(P>0.05)以及相对丰富度(P>0.05)差异不显著,物种数在不同区域差异较明显(P=0.005);Shannon(H),Simpson(D)比较结果表明,交错区的物种多样性高于沉水区;物种相似性S?rensen’s比较结果仅在样线上存在差异,第一条样线的物种相似性比其他样线差异小;以样方为单位基于TWINSPAN聚类进行的DCA分析的结果将沉水区和交错区区分开来.疏化曲线结果表明:为获得调查所观测到的最大物种数,沉水区为361个个体,交错区为304个个体;沉水区疏化曲线个体与样方之间的垂直距离大于旱生区域,并随着取样个体的增加而逐渐增大.一年生或两年生物种的物种数以及高原所特有的物种数比较结果表明,交错区物种数高于沉水区.以上结果说明,以尕海为代表的高海拔湿地种子库沿水位梯度存在带状分布格局,这一格局的存在使得地表植被存在沿水位梯度带状分布特征的潜力.

In recent years, wetland biodiversity and vegetation on the Qinghai-Tibet Plateau have been severely degraded. The seed bank is one of the most important resources available to aid recovery of degraded wetland plant communities. Studies of seed bank heterogeneity are crucial for understanding population formation, vegetation succession, and dynamics. In this study, we investigated the seed bank along water gradients of the Gahai Lake wetland on the eastern Qinghai-Tibet Plateau. We established three sampling lines in lakeside zones and two sampling lines in submerged zones, and looked for differences between lakeside and submerged zones. Seed bank species number and evenness were tile same among different sampling lines and different zones, whereas Shannon＇s （H） and Simpson＇s （D） formulas revealed that diversity was higher in the lakeside zone than in the submerged zone, A comparison based on Scrensen＇s index indicated the least diverse along the first sampling line. DCA and TWINSPAN analyses separated the sampled species into two clusters： a group consisting of the first and second sampling lines and the first sample of the third line, and a group comprising the remaining samples. Based on species rarefaction curves, more species were found to occur in submerged zones than lakeside zones, although fi＇equency of presence of species found in both zones was similar. Comparisons of species＇ life histories and plateau endemicity revealed that the number of endemic species in the fourth and fifth sampling lines was higher than in the first three lines. Our results indicate that a vegetational zonation pattern based on water gradients exists around Gahai Lake.