Changes in and evaluation of surface soil quality in Populus × xiaohei shelterbelts in midwestern Heilongjiang province, China

Abstract

To examine changes in surface soil quality over time in Populus × xiaohei shelterbelts, we collected soil samples from five shelterbelts of different ages and also from former cropland left fallow for 25 years. Twenty-one surface soil (0–20 cm) properties were measured, and variation in soil quality was assessed using one-way ANOVAs and multiple comparison tests. Based on this analysis, 16 soil indexes were used in a model evaluating soil quality, with each index given weight as determined by the correlation coefficient. Compared with the control, the post-mature forest had greater soil moisture content but lower bulk density (P < 0.05). The mature forest also had higher soil pH, total organic carbon, alkali-hydrolyzed nitrogen, available phosphorus, and biomass nitrogen content, but reduced nitrate-nitrogen and total phosphorus content than the control (P < 0.05). Total porosity was highly positively correlated with aeration, nitrate-nitrogen, alkali-hydrolyzed nitrogen, available phosphorus, microbial biomass carbon and microbial biomass nitrogen. Soil total organic carbon, ammonium nitrogen, nitrate-nitrogen, alkali-hydrolyzed nitrogen, total nitrogen, available phosphorus, microbial biomass carbon and microbial biomass nitrogen were all strongly correlated. In the soil quality evaluation model, total organic carbon was assigned the highest weight and total potassium content the lowest. The soil quality index was lowest in the near-mature forest and greatest in the post-mature forest. Generally, soil quality in Populus × xiaohei shelterbelts varied with age and was higher in the 10–20 cm versus 0–10 cm soil layer. After a single forest generation, surface soil quality was significantly improved.