Rhizosphere and non-rhizosphere soil nutrient characteristics of Betula alnoides forest in southwest China with different stand densities

Due to the complex interaction process between roots and soil of trees, the effects of stand density on rhizosphere and non-rhizosphere soil may be different. Based on this, the effects of different stand densities on rhizosphere and non-rhizosphere soil nutrients in Betula alnoides plantation were explored, and the characteristics of rhizosphere and non-rhizosphere nutrients under different stand densities were clarified, providing theoretical basis for screening reasonable densities of Betula alnoides plantation. Four kinds of Betula alnoides forests with different stand density of 15 year were selected as the research object, and their densities were(A:400 plants/hm², B:1000 plants/hm², C:1367 plants/hm², D:2025 plants/hm²), respectively. Soil nutrient of rhizosphere and non-rhizosphere soils in different soil layers(0-20 cm, 20-40 cm) were analyzed. The soil quality was evaluated by variance analysis and correlation analysis. 1. The rhizosphere soil pH and total potassium of the two soil layers reached the maximum at stand density A, pH was 4.54 and 4.31, and total potassium was 19.49 g/kg and 17.09 g/kg, respectively. The remaining nutrient indexes reached the maximum at stand density B, which was significantly higher than that of the other three stands. 2. The total potassium content of 20-40 cm non-rhizosphere soil was the highest in stand A(16.67 g/kg), and the other nutrient indexes of non-rhizosphere soil reached the maximum at stand density B; 3. The rhizosphere effects of different stand densities showed that pH of the four stands was negative, the nutrient indexes of stand A, B and C were positive as a whole, and the rhizosphere effects of stand D were negative except for total nitrogen, organic matter and total potassium. 4. Correlation results showed that rhizosphere and non-rhizosphere soil nutrient indexes were significantly positively correlated with organic matter content as a whole. Principal component analysis showed that stand density had the greatest influence on soil organic matter, total nitrogen and total phosphorus. With 1000 plants/hm² stand density, the rhizosphere and non-rhizosphere nutrient content of Southwest birch plantation is rich, and the density of southwest birch plantation can be controlled at about 1000 plants/hm² during production.