Spatial relationship between δ<sup>15</sup>N and elevation in agricultural landscapes

oleh: F. L. Walley, B. C. Si, A. Biswas

Format: Article
Diterbitkan: Copernicus Publications 2008-05-01

Deskripsi

Understanding of the nitrogen (N) cycle and its spatial variability is important for managing ecosystems. Soil δ<sup>15</sup>N, as an important indicator of different soil nitrogen cycling processes, may provide critical information about the spatial variability in soil N cycling. The objective of this study was to examine the dominant landscape scale variability of δ<sup>15</sup>N, the location of the variability and its spatial relationship with elevation. Soil δ<sup>15</sup>N and elevation were measured along two transects (Davidson and Elstow, Saskatchewan, Canada). Each transect had 128 points with 3 m sampling intervals. Higher δ<sup>15</sup>N values typically occurred in topographic depressions as compared to knolls. The coefficient of determination revealed a significant linear relationship between δ<sup>15</sup>N and elevation (<i>r</i><sup>2</sup>=0.27) at Davidson whereas no relationship (<i>r</i><sup>2</sup>=0.00) was detected for the Elstow transect. However, wavelet spectra, cross wavelet, and squared wavelet coherency analysis revealed spatial relationships between δ<sup>15</sup>N and elevation at both sites. A strong coherency between δ<sup>15</sup>N and elevation at large scales (96 m or more) was detected for both transects. The Davidson transect showed an out of phase coherency at a topographically elevated area at the beginning and the end of the transect. The Elstow transect had a strong out of phase correlation (negative relationship) at the middle of the transect (corresponding to a depressions) indicating a location dependent relationship between δ<sup>15</sup>N and elevation. The relationship between δ<sup>15</sup>N and elevation reflects the effects of hydrology and soil water content over the landscape on N cycling processes.