Changes in Dominant Perennial Species Affect Soil Hydraulic Properties after Crop Abandonment in a Semiarid Grassland in Mongolia
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Crop abandonment is a factor responsible for soil degradation in semi-arid regions. The effects of crop abandonment on soil restoration may depend on soil properties and climatic conditions of an area. In particular, soil hydraulic properties affect the vegetation recovery process. The objective of this study was to investigate the succession changes in water flow as a result of changes in soil hydraulic properties after crop abandonment under drought and non-drought conditions, and under water uptake by co-occurring perennial plants to clarify the observation that typical perennial grass species are seldom observed in abandoned fields. Soil hydraulic properties were measured in croplands which had been abandoned for different periods (2, 9, and 18 years ago) and in a grazed grassland site (control site). Hydrological processes in the soil profiles were simulated with soil hydraulic properties under drought and non-drought summer conditions with water uptake from perennial grass species. Suctioning the surface soils increased with the period of abandonment, with this trend being particularly obvious in a drought year. Soil water appears to be restricted in the later succession stage of abandoned fields and in grazed grassland for drought-tolerant plants. Dry soil and climate conditions are important factors determining the intrusion of the typical perennial grass, Stipa krylovii, into degraded abandoned fields. A water availability with low pressure (plant can use with low pressure) made difficult the intrusion of typical perennial grasses to abandoned cropland. This abiotic relation between soil hydraulic properties and climate conditions may play an important role for plant succession in abandoned cropland.
Keywords:unsaturated hydraulic conductivity water restoration
This study would not have been possible without the willing cooperation of the staff of Hustai National Park. We sincerely thank them all, especially Prof. B. Namkhai (Director, Hustai National Park). We also thank assistant professor S. Okubo and Dr. T. Okayasu (Department of Ecosystem Studies, Graduate School of Agricultural and Life Sciences, The University of Tokyo) for their helpful comments.
This study was conducted under the Global Environmental Research Fund of Japan’s Ministry of the Environment “Desertification Control and Restoration of Ecosystem Services in Grassland Regions of North-East Asia” (no. G-071), with the additional support of a JSPS Research Fellowship for Young Scientists awarded to A. Yanagawa (no. 20-7002 and 24-7604).
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