Spatial variability of soil nitrogen, phosphorus and potassium contents in Moso bamboo forests in Yong'an City, China

Abstract

Bamboo is an important forest type in Southern China, covering an area of 6.16 million ha, >70% of which is Moso bamboo (Phyllostachys heterocycla (Carr.) Mitford cv. Pubescens) forest. Moso bamboo forests are characterized by fast growth and high nutrient dynamics due to the annual timber harvest, and thus a high nutrient input is required compared with other forest types. Soil nitrogen (N), phosphorus (P) and potassium (K) are important micronutrients for plant growth and productivity. Because of the high spatial and temporal variability of soil, information on the spatial distribution of N, P and K contents in Moso bamboo forests is very limited, although this information is important for improving soil nutrient management. Therefore, in this study, soil samples at 0–20, 20–40 and 40–60cm were taken from 138 locations in Moso bamboo forests across the study area. The N, P and K contents of different soil layers ranged from 1.01 to 4.11gkg−1, from 0.025 to 0.131gkg−1 and from 0.42 to 5.40gkg−1, respectively. The coefficient of variation of N, P and K contents ranged from 26% to 43%, suggesting a moderate variability. Ordinary kriging (OK) and inverse distance weighting (IDW) approaches were applied to analyse the spatial patterns of N, P and K contents. Geostatistical analysis showed a moderate spatial dependence of N, P and K contents, indicating that N, P and K contents were controlled by both intrinsic and extrinsic factors. Cross-validation illustrated that OK performed better than IDW. OK and IDW showed a similar spatial pattern of N, P and K contents over the whole study area, demonstrating the suitability of OK and IDW in spatial interpolation. However, OK produced a smaller range of predicted N, P and K contents than IDW, highlighting the necessity of using different approaches when studying the spatial distribution of soil properties.