title: Spatial variability of soil nitrogen in a hilly valley: Multiscale patterns and affecting factors.
abstract: Estimating the spatial distribution of soil nitrogen at different scales is crucial for improving soil nitrogen use efficiency and controlling nitrogen pollution. We evaluated the spatial variability of soil total nitrogen (TN) and available nitrogen (AN) in the Fujiang River Valley, a typical hilly region composed of low, medium and high hills in the central Sichuan Basin, China. We considered the two N forms at single hill, landscape and valley scales using a combined method of classical statistics, geostatistics and a geographic information system. The spatial patterns and grading areas of soil TN and AN were different among hill types and different scales. The percentages of higher grades of the two nitrogen forms decreased from low, medium to high hills. Hill type was a major factor determining the spatial variability of the two nitrogen forms across multiple scales in the valley. The main effects of general linear models indicated that the key affecting factors of soil TN and AN were hill type and fertilization at the single hill scale, hill type and soil type at the landscape scale, and hill type, slope position, parent material, soil type, land use and fertilization at the valley scale. Thus, the effects of these key factors on the two soil nitrogen forms became more significant with upscaling.
authors.affiliation: College of Environmental Science, Sichuan Agricultural University, Wenjiang 611130, PR China. Electronic address: srzhang01@aliyun.com.
authors.forename: Shirong
authors.initials: S
authors.lastname: Zhang
authors.affiliation: College of Environmental Science, Sichuan Agricultural University, Wenjiang 611130, PR China.
authors.forename: Chunlan
authors.initials: C
authors.lastname: Xia
authors.affiliation: College of Resources, Sichuan Agricultural University, Wenjiang 611130, PR China.
authors.forename: Ting
authors.initials: T
authors.lastname: Li
authors.affiliation: Agricultural Bureau in Shehong, Shehong 629200, PR China.
authors.forename: Chungui
authors.initials: C
authors.lastname: Wu
authors.affiliation: College of Resources, Sichuan Agricultural University, Wenjiang 611130, PR China.
authors.forename: Ouping
authors.initials: O
authors.lastname: Deng
authors.affiliation: College of Environmental Science, Sichuan Agricultural University, Wenjiang 611130, PR China.
authors.forename: Qinmei
authors.initials: Q
authors.lastname: Zhong
authors.affiliation: College of Environmental Science, Sichuan Agricultural University, Wenjiang 611130, PR China.
authors.forename: Xiaoxun
authors.initials: X
authors.lastname: Xu
authors.affiliation: College of Resources, Sichuan Agricultural University, Wenjiang 611130, PR China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Li
authors.affiliation: College of Resources, Sichuan Agricultural University, Wenjiang 611130, PR China.
authors.forename: Yongxia
authors.initials: Y
authors.lastname: Jia
keywords: Affecting factor; Available nitrogen; General linear model; Hilly region; Multiscale; Total nitrogen