Net nitrogen mineralization in soils of Napahai wetland in Northwest Yunnan Peashrub Community May Accelerate the Successional Process in a Meadowland-Peashrub-Birch Sere Effects of understory removal and nitrogen addition on the soil chemical and biological properties of Pinus sylvestris var. mongolica plantation in Keerqin Sandy Land. Soil N Mineralization of An Alpine Meadow in Eastern Qinghai-Tibetan Plateau Nitrogen mineralization in alfalfa stands