科尔沁沙地疏林榆树植被更新过程研究

The community of sparse Elm woodland is mainly composed by Elm trees, desert shrubs and herbaceous plants in kerqin Sandy Land. The characteristics of vegetation are long-term existence and relatively stable near-natural. The sparse Elm woodland made an irreplaceable role in maintaining the ecosystem stability, promoting the natural vegetation restoration, and conserving biodiverstiy in kerqin Sandy Land. In recent 30 years, the sparse Elm woodland could not complete the natural regeneration processes led by many obstacles under natural conditions, which mainly showed reduction of seed germination, seedlings survival and growth rate affected by climate and human activities. The population degradation of sparse Elm woodland has put significant pressure on stability and control functions of ecosystem and natural vegetation restoration processes in Kerqin Sandy Land. Selected Sparse Elm trees as objective in this project, we discuss the main characteristics in life history of Sparse Elm trees, effects of environmental factors, grazing disturbance and species competitions on regeneration processes of sparse Elm woodland in kerqin Sandy Land. The aim is to reveal the major obstacles of natural regeneration and elucidate the mechanisms in the regeneration processes of the sparse Elm woodland. The results would provide more scientific basis for the natural regeneration of sparse Elm woodland, promotion of natural vegetation restoration and conservation of ecosystem stability in kerqin Sandy Land.

科尔沁沙地榆树疏林植被是稀疏榆树与沙地灌木、草本植物共同组成的群落类型，是科尔沁地区长期存在的一种相对稳定的近自然原生植被。疏林榆树植被在维系科尔沁沙地生态系统稳定、促进沙地植被自然恢复以及沙地物种多样性保护方面具有不可替代的作用。 在近30年以来，受气候条件和人为活动影响，科尔沁沙地疏林榆树植被在自然条件下的天然更新存在诸多障碍，主要表现在榆树的种子萌发率低、幼苗保存和幼树生长数量减少，榆树种群衰退，已经对科尔沁沙地生态系统的稳定及植被自然恢复过程产生重要影响。 本项目以科尔沁沙地疏林榆树植被为研究对象，通过对疏林榆树生活史阶段特征、沙地环境因子对疏林榆树更新过程的影响、放牧干扰和物种竞争对疏林榆树更新过程的作用研究，阐明和揭示影响科尔沁沙地疏林榆树天然更新的主要障碍因子与作用机理，进而为实现科尔沁沙地疏林榆树的自然更新、促进沙地植被自然恢复、维系沙地生态系统的稳定与平衡提供科学依据。

科尔沁沙地榆树疏林植被是稀疏榆树与沙地灌木、草本植物共同组成的群落类型，是科尔沁地区长期存在的一种相对稳定的近自然原生植被。疏林榆树植被在维系科尔沁沙地生态系统稳定、促进沙地植被自然恢复以及沙地物种多样性保护方面具有不可替代的作用。 在近30年以来，受气候条件和人为活动影响，科尔沁沙地疏林榆树植被在自然条件下的天然更新存在诸多障碍，主要表现在榆树的种子萌发率低、幼苗保存和幼树生长数量减少，榆树种群衰退，已经对科尔沁沙地生态系统的稳定及植被自然恢复过程产生重要影响。 本项目以科尔沁沙地疏林榆树植被为研究对象，通过对疏林榆树生活史阶段特征、沙地环境因子对疏林榆树更新过程的影响、放牧干扰和物种竞争对疏林榆树更新过程的作用研究 ， 得到如下主要结论：沙地榆结实量年际间变化剧烈，种源质量不佳，传播范围受限使得沙地榆拓殖更新能力受阻。主要表现为种子千粒重低，萌发率低。生长季水分亏缺和遭受过度沙埋是导致沙地榆种子-幼苗阶段更新受阻的主要原因。土壤表层水分含量低影响沙地榆种子顺利萌发和幼苗的生长建成过程，同时频繁风沙活动影响萌发成苗过程。放牧干扰和围栏封育对于沙地榆群落结构产生了重要影响。重度放牧导致幼龄沙地榆所占比例较少，使得种群表现为衰退型。因地制宜开展榆树疏林草原的有效恢复与适当利用既可以减轻放牧对于榆树疏林草原的影响，又有助于沙地生态保护与经济增长的协调发展。