『Abstract
The spatial variability of soil total nitrogen (STN) and soil
total phosphorus (STP) levels, which may be greatly affected by
land use, plays an important role in both agriculture and the
environment, especially with regard to soil fertility, soil quality,
and water-body eutrophication. Little research has been done that
addresses the spatial patterns of STN and STP under different
land use types at a watershed scale. We collected 689 soil surface
(0-20 cm) samples, using a grid sampling design, from the Liudaogou
watershed (6.89 km2) on the Loess Plateau of North
China. Using classical statistical and geostatistical methods,
we characterized and compared the spatial heterogeneities of STN
and STP under different land use types (farmland, grassland, and
shrubland). Concentrations of STN and STP were normally distributed
with the exception of STP in grassland, and decreased in the order:
farmland ＞ grassland ＞ shrubland. Stepwise multiple regression
analysis indicated a strong relationship between STN and soil
organic carbon (which was mainly controlled by plant growth and
microbial activity), while STP was associated with the content
of finer soil particles (which absorb P more readily and whose
distribution is related to slope aspect and altitude). Both STN
and STP showed moderate variability under different land use types.
Nugget ratios for STN showed a moderate spatial dependence and
decreased in the order: farmland ＞ grassland ＞ shrubland, whereas
STP increased in that order and showed strong, moderate, and weak
spatial dependence, respectively. The type of optimal theoretical
isotropy models differed for STN and STP as well as for the land
use type. We concluded that spatial patterns of STN and STP would
change significantly with land use changes currently being implemented
to achieve sustainable agriculture development and environmental
restoration. Taking land use type into account when considering
the spatial variation of STN and STP would increase the accuracy
in modeling and prediction of soil nutrient status and nutrient
movement at the watershed scale.
Keywords: Land use; Spatial variability; Geostatistics; Multivariate
statistics; The Loess Plateau』
1. Introduction
2. Materials and methods
2.1. Description of study area
2.2. Soil sampling and analysis of STN and STP
2.3. Statistical and geostatistical analyses
3. Results and discussion
3.1. Traditional statistics
3.1.1. Correlation analysis
3.1.2. Multiple linear regression analysis
3.2. Geostatistical analysis
3.3. Spatial autocorrelation analysis
4. Conclusions
Acknowledgments
References