『Abstract
The northern Loess Plateau is an important cropping-pastoral
ecotone and wind-water erosion crisscross region in China, but
the distribution of soil organic carbon (C), nitrogen (N) and
phosphorus (P) in different land uses across this vulnerable ecoregion
is not well understood. This study was carried out to determine
the distribution patterns of soil organic C, N and P in native
grassland and in two woody lands (Chinese Pine land and Korshinsk
Peashrub land) that were established on the native grassland 28
years ago. In the north part of the Loess Plateau, the concentrations
of soil organic C, N and P were lower than in the southern Loess
Plateau either across or within the land use patterns. The concentrations
and stocks of organic C and total N were significantly decreased
in Chinese Pine and L\Korshinsk Peashrub lands compared with those
in native grassland in the surface 0-40 cm soil layer, where more
than 70% of the roots were distributed. The decreases in organic
C in 0-40 cm soil layers were 2.6 and 3.0 Mg C ha-1
(26.3 and 27.7%) by Chinese Pine and Korshrinsk Peashrub, while
those of total N were 0.6 and 0.4 Mg N ha-1 (31.5 and
17.2%), respectively, compared with native grassland. Both concentration
and stock of total P varied only slightly with land use. The findings
suggested that the conversion of natural grass into Chinese Pine
and Korshinsk Peashrub resulted in decreased soil organic C and
total N in the surface 0 to 40 cm soil layer of the northern Loess
Plateau. Our results further indicated that a combination of low
temperatures, little precipitation and large soil degradation
impede increasing C and N stocks by afforestation, and the afforestation
on grassland should be viewed very critically in such areas.
Keywords: Chinese Pine; Korshinsk Peashrub; Native grass; Nitrogen;
Phosphorus; Organic carbon; The northern Loess Plateau 』
Introduction
Materials and methods
Study site
Field investigation, soil sampling and laboratory analysis
Statistical analysis
Results
Similarity of soil organic C and nutrients before land use
conservation in the study site
The effects of land use on soil organic C and nutrients
Comparison with other regions in the Loess Plateau
Discussion
Land use effects on soil organic C and nutrients in the northern
Loess Plateau
Comparison with other regions in the Loess Plateau
Implications for land management and suggestions for further
research
Acknowledgments
References