Spatial variability of soil total nitrogen in PopuLus tomentosa forestation land in south Hebei plain

摘要

In order to investigate the spatial variability of soil total nitrogen (STN) contents in Populus tomentosa forestation land in South Hebei Plain, a gridding method was adopted for stationing and sampling in the 6.0 hm2 of P. tomentosa forestation land in South Hebei Plain in March. 2007. The land was divided into twenty four 50×50 m plots where soil samples were selected at varying soil layers: 0-20 cm, 20-40 cm and 40-60 cm. The results showed that the mean of STN contents above 60 cm soil layer was 0.40 g·kg-1 (from 0.05 to 0.82g·kg-1). Fertility level of the soil in the P. tomentosa forestation land in South Hebei Plain is classified as extremely-low level. The STN content generally had moderate spatial variability since the coefficient of variation (CV) at each layer was increased with the increase of soil depth. The horizontal variability of STN at 0-20 cm soil layer was that the value first increased and then declined from west to east and had a twice trend of first increase and then decrease from north to south. At 20-40 and 40-60 cm soil layers, the horizontal variability of STN content was: the value declined gradually from west to east. while rose up gradually from north to south. The STN content at the depth of 0-20 cm was obviously higher than the value at the depth of 20-40 cm and 40-60 cm (P<0.01). In conclusion. the thin soil layer, sandy texture and severe wind erosion and desertification are contributed to the relative lower STN in the P. tomentosa forestation land in South Hebei Plain, and the proper methods of irrigation and fertilization should be taken to improve the soil fertility.