几种灌木、半灌木对沙地土壤肥力影响机制的研究

研究了科尔沁地广泛分布的几种灌木和半灌木的“肥岛”和根际效应。结果表明,在灌丛下土壤有机C、全N和全P分别比灌丛间地高56％、51％和37％,土壤电导率（EC）提高了56％,但pH值并无明显变化;灌木根际土壤较非根际土壤有机C和全N分别高76％和54％,根际土壤pH降低0．19个单位,EC提高了2－3倍,但土壤全P并无显著变化,灌丛下土壤发和根际中土壤养分含量显著相关,表明丛肥岛的利于根系的生长,导致更多的根际沉积;而根系的活动又促进了肥岛的发育,灌丛对沙地土壤肥力的影响机制在于：灌丛对土壤风蚀物质、降尘和凋落物等的截获,形成灌丛“肥岛”;并通过发达的根系以根际沉积的形式向土壤输入大量的有机物质,从而使周围土壤的肥力性关得以改善。

Influencing mechanism of several shrubs and subshrubs on soil fertility in Keerqin sandy land

Keerqin sandy land is one of serious desertification areas in the semiarid zone of north China, and shrubs are the dominant plant life form and play an important role in the region. The effects of "fertile island" and rhizosphere of several shrubs and subshrubs were studied. The results showed that the concentrations of organic C, total N and total P, and values of electrical conductivity (EC) in the soils under the canopy of shrubs increased by 56%, 51%, 37%, and 51%, respectively, compared with those of the soils in open spaces, but there was no significant difference in pH value between the soils under shrub canopies and in open spaces. Shrub rhizosphere soils had significant higher contents of organic C, total N, and values of EC as well as lower pH value compared to the bulk soils, but there was no significant difference in total P between rhizosphere and bulk soils. There were close relationships between the properties in soils under shrub canopies and the rhizosphere soils, indicating that the development of "fertile island" were favorable to root growth and induced greater amount of rhizodeposition, and vice versa. Soils under Artemisia frigida and Caragada microphylla canopies and rhizospheres had significant higher organic C and total N contents than those of Artemisia halodendron and Salix gordejvii . This results suggested that shrubs were of vital importance for accumulation of nutrients and maintenance of soil fertility in Keerqin sandy land ecosystem.