Soil biochemical properties and arbuscular mycorrhizal fungi as affected by afforestation of rangelands in northern China

During the last five decades, a large amount of rangeland has been converted into forests in areas of northern China confronting soil erosion and land degradation. Assuming that such land use conversion influences soil biochemical properties, we used soil chemical and enzyme activities as well as spore density and arbuscular mycorrhizal (AM) colonization of five dominant plant species to evaluate the effects of conversion from rangeland to Poplar devidiana plantations on top soil quality. Planting trees on rangeland significantly decreased soil organic C and N irrespective of the sampling month and soil depth. Afforestation also lowered the soil pH level and reduced electrical conductance. Moreover, dehydrogenase, urease, acid and alkaline phosphatase activities were all significantly affected. Land use conversion decreased spore density and influenced the mutual relationships between AM fungi and plant species. AM colonization of the dominant plants was lower in forested land than rangeland. Correlation analyses also showed that AM colonization and spore density were positively correlated with N, organic C, and acid phosphatase. These results indicated that spore density and AM colonization as well as organic C and N content and enzyme activities are all sensitive and reliable indicators of biochemical changes generated by land use conversion.