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[Assessment of soil quality under different land use types in the rocky mountain area of northern Hebei Province, China.]

To assess the variations of soil quality among land use types and with altitude in the rocky mountain area of northern Hebei Province is critical for preventing further human-induced degradation of land and vegetation, and for formulating a strategic plan on vegetation restoration after the Beijing Winter Olympics. Taking Betula platyphylla natural forest, Larix gmelinii plantation, natural grassland and abandoned cropland as research objects, 13 soil physicochemical indices (e.g., soil bulk density, porosity and soil nutrient content) were measured to compare soil quality among land use types. The results showed that soil quality presented the trend as B. platyphylla natural forest > natural grassland > L. gmelinii plantation > abandoned cropland. B. platyphylla natural forest had the best soil quality due to high total nitrogen (3.24 ±1.42 g·kg-1) and phosphorus (0.59±0.10 g·kg-1) contents, suggesting that long-term soil nutrient accumulation played an important role in preventing soil degradation. Soil quality in natural grassland was lower than that in B. platyphylla natural forest, due to topographic factors and coarse soil fraction. Soil physical properties in L. gmelinii plantation had been substantially improved after 40 years restoration, as indicated by significant reductions in soil gravel fraction, while soil nutrient contents changed little. The low soil quality in abandoned cropland was attributable to low vegetation coverage and intense human activities in the low-altitude area. Driven by soil total nitrogen, soil quality under the four land use types increased with altitude, and peaked at about 1700 m. We suggested that enclosure and ecological restoration measures should be strengthened in ecologically-fragile, low-altitude areas, taking sustainable development into consideration for high-density stands and promoting plantations to adapt to environmental change.