氮磷添加及林分密度对大叶相思林土壤化学性质的影响

Effects of nitrogen and phosphorus additions and stand density on soil chemical property in Acacia auriculiformis stands

大气氮(N)沉降随着人类的活动而日趋严重,加上中国热带亚热带红壤普遍缺磷(P),许多森林生态系统由于广泛使用磷肥而产生P富集,直接影响了森林土壤化学特性。林分密度改变林地的光照、温度、湿度和凋落物持水量,从而影响土壤特性。为了解外源性N和P添加与林分密度对大叶相思(Acacia auriculiformis)林地土壤化学性质的影响,为大叶相思人工林的种植密度和土壤养分管理提供科学依据,该研究于2013到2015年,以4种不同密度(1667、2500、4444和10000 trees·hm-2)的10年生大叶相思人工林为研究对象,分别进行添加N、P和N+P处理,在试验结束时采集0–10cm土壤,对其pH、有机质含量、N含量、P含量和钾(K)含量进行了测定分析。结果表明:施N和N+P均显著降低了土壤的pH和速效K含量,显著提高了林地土壤的碱解N含量。施N还显著提高了林分土壤的全N含量,施P显著提高了土壤pH,降低了林分土壤的全N含量。施P和N+P显著提高了土壤有机质、全P和有效P含量。随着林分密度的增加,各处理的土壤有机质、全N、碱解N、全P、有效P和速效K含量显著提高。N、P添加处理和密度处理对大叶相思林的土壤pH、有机质和N、P、K含量有显著的交互作用。总体来看,N添加、P添加、林分密度及其交互作用对大叶相思的土壤化学性质有显著影响。

Aims Due to human activities, nitrogen(N) deposition is increasingly serious, and phosphorous(P) fertility is widely applied in the soils of subtropical forests suffering from P deficiency, but there are relatively few researches of N and P additions on soil characteristics of subtropical forests. Difference in stand density may affect light, temperature, water and litter water holding capacity, which may influence soil characteristics. The effects of external nitrogen and phosphorus and stand density on soil chemical property were investigated in 10 years-old Acacia auriculiformis stands in order to provide a scientific basis for stand density and forest soil management. Methods In this study, five subsample plots were established in the stands with four densities(1 667, 2 500, 4 444 and 10 000 trees·hm-2) and treated with N addition, P addition, N+P addition and control from 2013 to 2015. At the end of experiment, soils at 0–10 cm depth with different treatments were collected and pH value, organic matter content, N, P and K contents were analyzed in the A. auriculiformis stands. Important findings The results indicated that soil pH value and available potassium(K) content significantly decreased, whereas soil alkalized N content significantly increased after N and N+P additions in the four density stands, and soil total N content significantly increased after N addition. Soil pH value significantly increased and soil total N content significantly decreased after P addition. Contents of soil organic matter, total P and available P significantly increased after P and N+P additions. With the increase of stand density, the contents of soil organic matter, total N, alkaline N, total P, available P and available K significantly increased. The interactive effects of density and N and P additions on soil pH value, organic matter, N, P and K contents were significant in the stands. Generally, the effects of N and P additions, stand density and the both interaction on soil chemistry property were significant.