2. Materials and methods
2.1. Site description
The study site is located at the Yanting Agro-ecological
Experimental Station of Purple Soil, Chinese Academy of Science
under the Chinese Ecosystem Research Network (CERN). The
station is located at 31
160
N, 105280
E, at an altitude of 400–600 m,
and in the middle of the Sichuan Basin, southwestern China.
The soil in the study area is called purple soil and is classified as a
Pup-Orthic Entisols in the Chinese soil taxonomy and as an Entisol
in the U.S. Taxonomy (Zhu et al., 2009). The study site represents the intensive agriculture lands found in a subtropical monsoon
climate and has an annual mean temperature of 17.3 C and a mean
precipitation of 826 mm (1981–2009).