• 1
  • 原文摘要
  • 本文以宁夏沙湖一个典型的干旱区灌草型白刺(Nitraria tangutorum)-芨芨草(Achnatherum splendens)群落为研究对象,将该群落自植物聚生丛冠层覆盖区至丛间裸地依次划分为冠盖区、过渡区和空旷区3个微生境分区,通过比较两优势种的根系生物量密度以及根系消弱系数(反映根系总体埋深)在这3个分区中的分布特征,研究了干旱胁迫环境下两物种的根系分布与共存机制.结果表明:两物种的总根与细根均集中分布于冠盖区,但芨芨草根系生物量密度自冠盖区至空旷区的下降幅度更大;白刺总根及细根生物量密度重心自冠盖区至空旷区逐渐下移,而芨芨草的总根和细根生物量密度重心在空旷区较过渡区有所抬升;另外,白刺细根生物量密度在冠盖区10~30 cm土层中最高,而芨芨草在0~10cm层最高;各微生境分区内两物种的根系消弱系数均具有显著性(或接近于显著性)差异.这暗示了白刺与芨芨草的根系分布存在明显的生态位分离现象.“地上聚生,地下分离”的共生方式可能是白刺与芨芨草共同适应干旱环境的生长策略. This study aims to better understand the underlying mechanisms of the coexistence of shrub and grass species in arid environments.A typical shrub-grass community,Nitraria tangutorum-Achnatherum splendens community,was selected near the Shahu Lake in Ningxia Hui Autonomous Region,Northwest China.To characterize the heterogeneity of the habitat,we partitioned the community into three microhabitats,namely under-canopy,transitional and open microhabitats,from the canopy areas of plant clumps to the inter-clump barren areas.With trenching methods,roots were collected and the distributions of root biomass densities and root extinction coefficients of the two species were compared in the soil profiles of the three microhabitats.The results showed that both Nitraria and Achnatherum produced most of their roots in under-canopy microhabitats;however,the extent of decline in root biomass density from under-canopy to open microhabitats was more intensive in Achnatherum.The layers with highest root biomass densitv of Nitraria were continuously deepened from under-canopy to open microhabitats,while that of Achnatherum re-increased in open microhabitats.Nitraria had its highest fine root biomass density in 10-30 cm layer in the under-canopy microhabitat,while the highest fine root biomass density of Achnatherum was in 0-10 cm layer.There were significant (or marginally significant)differences in root extinction coefficients between the two species in all microhabitats,indicating that there was belowground niche segregation between Nitraria and Achnatherum.Taking into account of the patchy clump-style aboveground distribution pattern,we suggest that abovcground aggregation together with belowground segregation might be the coexistence strategies of Nitraria and Achnatherum to cope with arid environments.
  • 用户摘录