| 摘要: |
| 【目的】探讨西藏那曲不同高寒退化草地土壤种子库存量、可萌发种子数量和种子萌发的生理生态特征，为西藏高寒退化草地植被恢复、生产力提高及生态保护提供参考。【方法】采用典型取样法，在那曲退化草地试验区按照植被盖度高低选取轻度、中度、重度和极重度4种不同退化程度的样地，在每个样地内采用样线法选取4块样方，于每个月的第1天在样方内采取10 cm×10 cm×10 cm的土样(包括地上的枯枝落叶)，采用土样浸泡、溶解、过筛方法分离种子，对其进行鉴定并计数，通过室内萌发试验测定土壤种子库中可萌发的种子数量；用不同质量分数的GA3(0.10%，0.05%和0.02%)、KNO3(0.20%)、H2SO4(60%，70%，80%和90%)处理种子库，分析3种溶液对种子萌发的影响。调查各种植物的相对盖度、相对频度、相对密度和相对生物量，计算其重要值，分析不同退化草地植物群落种类的组成特征。【结果】那曲高寒中度退化草地种子库中的种子数量最多，为(530±80.00) 粒/m2；其次是重度和极重度退化草地，其种子数量均为(250±44.72) 粒/m2；轻度退化草地种子库种子存量最少，为(216±21.34) 粒/m2。种子库中的物种以蔷薇科（Rosaceae）、菊科（Compositae）、禾本科（Gramineae）植物为主。在实验室条件下，轻度退化草地种子库中可萌发种子数量最少，为(100±0.00) 粒/m2；其次是重度和极重度退化草地，均为(140±24.50) 粒/m2；中度退化草地种子库中可萌发种子数量最多，为(260±40.00) 粒/m2。采用质量分数0.05% GA3处理土壤种子库中的种子时，能够破除种子的休眠作用，有利于种子的萌发；采用质量分数0.2% KNO3处理土壤种子库中的种子，对种子萌发也有一定的促进作用；不同质量分数H2SO4处理对土壤种子库中种子的萌发表现出一定的抑制作用。轻度退化草地以西藏嵩草和高山嵩草为优势种，中度退化草地以高山嵩草和黑褐苔草为优势种，重度退化草地以高山嵩草为优势种，极重度退花草地以臭蒿、矮火绒草和轮叶棘豆为优势种。【结论】轻度退化草地以西藏嵩草和高山嵩草植物为主，牛羊采食量大，且有鼠害，可能会导致植物结种量减小；中度和重度退化草地由于菊科、蔷薇科属植物较多，所以种子库中留存植物种子最多；极重度退化草地中已经没有莎草科植物，主要为菊科、蔷薇科和十字花科植物，动物不可食植物比例增加，牛羊采食减少，故其种子库中植物数量也较多。 |
| 关键词: 西藏那曲 高寒地区 退化草地 土壤种子库 |
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| 基金项目:国家自然科学基金项目(30860061)；科技部农业科技成果转化项目(2010GB2F400453)；国家社科基金项目（XZ1121） |
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| Study on soil seed bank of different alpine degraded grasslands in Nakchu area of Tibet |
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| Abstract: |
| 【Objective】In order to provide some background knowledge for vegetation restoration,productivity and ecological protection of degraded grasslands in Nakchu area of Tibet,soil feed bank,the number of fermentable seeds,and the ecological characteristics in different degraded grasslands of Nakchu were systematically investigated.【Method】Based on vegetation coverage,plots of four different degradation levels (light degradation,medium degradation,heavy degradation and extremely severe degration)were selected.In four plots which were selected using line transect method,soils with volume of 10 cm×10 cm×10 cm (including litters) were taken as seed bank sample on the first day of each month .The soil was immersed,dissolved and sifted to separate seeds,and the separated seeds were appraised and counted.Then the amount of germinative seeds of soil seed bank was mensured by germination test in the lab.The influence of different mass fractions of GA3(0.10%,0.05% and 0.02%),KNO3(0.20%),H2SO4(60%,70%，80% and 90%)treatment of seed bank on seed germination was analyzed.The importance value of soil bank was calculated through its relative coverage,relative frequency，relative density and relative biomass.The composition and characteristics of plant community of soil bank was also analyzed.【Result】The results showed that the largest number of seeds (530±80.00)grains/m2 was obtained in the medium degraded meadow in Nakchu,followed by heavy and extremely severe degradation grasslands (250±44.72)grains/m2,while medium degraded grassland’s seed stock was the least (216±21.34)grains/m2.Most species in the seed banks were the Rosaceae,Compositae,Gramineae,and so on.Under laboratory conditions,the number of seeds that could germinate was the least in the seed bank of medium degraded grassland(100±0.00)grains/m2,followed by heavily and extremely severe degraded grasslands,and the largest number of seeds that could germinate was obtained in the medium degraded grassland(260±40.00)grains/m2.GA3 (mass fraction 0.05%) treatment could break the grassland seed dormancy and promote its germination.KNO3 (mass fraction 0.2%) treatment also promoted seed germination.However,different mass fractions of H2SO4 treatment of soil seed banks inhibited seed germination.Kobresia tibetica Maxim,Kobresia pygmaea and O.chiliophylla Royle were the dominant species in light degradation grassland,Kobresia pygmaea and Carex atrofusca were the dominant species in medium degradation grassland,Kobresia pygmaea was the dominant species in heavy degradation grassland,Artemisia hedini,Leontopodium.nanum and O.chiliophylla Royle were the dominant species in extremely severe degradation grassland.【Conclusion】The dominant species in minor degraded meadow in Nakchu were Kobresia alpine and Tibetan Kobresia,and most of them were fed to cattle and sheep.The rodent damage resulted in a smaller amount of seeds for many plant species.Due to the increase of asteraceae and rosaceae species at medium and heavily degraded meadows,the retained seeds in seed bank were most frequent.There existed no sedge plants,but mainly Asteraceae,Rosaceae and Cruciferous plants in extremely severely degraded grassland.With the increase of the proportion of inedible plants for cattle and sheep,a larger number of seeds thus were obtained in the seed banks. |
| Key words: Tibet Nakchu alpine area degraded grassland soil seed bank |
