荒漠草原沙漠化对植物和土壤C、N、P化学计量特征的影响

The disturbance of human activities and global climate change have made the grassland ecosystem degradation/desertification in different degree, and grassland degradation/desertification has become the most serious ecological environment problem in northern China. In semi-arid desert steppe of Ningxia, the effect of grassland desertification on C, N, P stoichiometry characteristics of plant and soil and the relationships of stoichiometry between plant and soil will be studied by using ecological stoichiometry theory and method. The study will explore evolution characteristics and regularity of C, N, P and its stoichiometry characteristics of plant and soil in the desertification process of desert steppe, and reveal the effect of desertification on C, N, P stoichiometry exchange process and pattern between plant and soil, interaction among C, N and P in desert steppe ecosystem from the perspectives of stoichiometry. The study is help to understanding composition and pattern characteristics of vegetation, degradation and recovery succession mechanism of desert steppe, and provide theoretic foundation for preventing desertification and restoration of sandy grassland ecosystem.

由于人类对草地资源的过度利用和全球气候变化，造成草地生态系统不同程度的退化与沙漠化，宁夏中北部荒漠草原严重的退化/沙漠化已成为中国北方主要的生态环境问题。本项目拟以生态化学计量学理论和方法，分析荒漠草原沙漠化对土壤、植物C、N、P生态化学计量特征及土壤-植物生态化学计量特征之间关系的影响，旨在探讨荒漠草原沙漠化过程中土壤、植物C、N、P元素及其化学计量的演变特征和规律，并从生态化学计量学的角度揭示荒漠草原沙漠化对土壤-植物系统中C、N、P生态化学计量交换过程与格局的影响机制、荒漠草原生态系统C、N、P元素之间的相互作用及平衡制约关系，其结果有助于重新认识植被组成与格局、荒漠草原退化与恢复演替机理，以期为防止沙漠化及沙漠化草地生态系统的恢复和重建提供理论依据。

生态化学计量研究为深入认识植物、凋落物、土壤相互作用的养分调控因素，揭示碳氮磷元素之间的相互作用及平衡制约关系，研究退化生态系统的稳定性，以及植被恢复对土壤-植物的相互作用提供新思路。以宁夏半干旱地区沙漠化荒漠草原为研究对象，通过测定荒漠草原沙漠化过程中植物多样性，生产力、土壤理化性状、土壤碳氮储量、植物和土壤C、N、P生态化学计量特征等，探讨荒漠草原生态系统碳氮储量变化，C、N、P元素之间的相互作用及平衡制约关系。结果表明：随着沙漠化程度加剧草地植物群落生物量、Shannon-Wiener 指数、丰富度指数、盖度均呈降低趋势，但轻度沙漠化阶段草地植被生物量比潜在沙漠化增加了23%。草地沙漠化导致土壤容重和土壤粗砂粒含量增加，而土壤水分、土壤细砂粒和粘粉粒含量降低。（2）不同沙漠化阶段土壤C、N含量差异显著，而植物C、N没有明显变异。潜在沙漠化阶段C、N储量最高，分别为1291.93 g/ m2和 142.10 g/m2；极度沙漠化阶段C、N储量最低，分别为505.14 g/m2和 33.41g/m2。荒漠草原沙漠化导致生态系统C、N损失786.79 g/m2和 108.69 g/m2。（3）荒漠草原沙漠化对植物叶片、根系和枯落物碳、氮、磷含量及其生态化学计量特征产生显著影响，其中沙漠化对植物叶片和根系氮含量、C:N比的影响规律相反。植物C:N:P生态化学计量可以解释不同沙漠化阶段植物物种和功能群变化。土壤碳、氮、磷含量，C:P和N:P比随着荒漠草原沙漠化呈显著变异。土壤碳、氮、磷含量，C:P比随着沙漠化过程呈降低趋势，但是土壤C:N基本成稳定趋势（10.85 to 11.48）。荒漠草原沙漠化导致了土壤环境和植被退化，草地生产力明显降低，改变了荒漠草原生态系统碳、氮、磷含量及其生态化学计量特征。