基于分形维数的不同林龄新疆杨对土壤理化特性的影响分析

Influence of Different Aged Populus alba var. pyramidalis on Soil Physicochemical Properties Based on Fractal Dimension

选取新疆南部阿克苏市郊柯柯牙防护林不同林龄新疆杨(Populus alba var.pyramidalis)林下土壤为研究对象,以裸露地为对照,通过野外采样和室内分析,基于分形维数模型研究了不同种植年限新疆杨土壤颗粒分形维数(D)特征及其主要影响因素。结果表明:不同年限新疆杨土壤D值处于2.2693~2.7104之间,明显高于裸露地(D=2.0545)(P<0.05),由高到低依次为22年生>15年生>6年生;在土壤深度10~30 cm和30~50 cm时,22年生防护林地D值较大,其它年龄林地各土层D值变化幅度不明显(P>0.05)。该防护林内各养分含量均高于裸露地,其差异显著(P<0.05),随杨树年龄的增长而增加。林地内土壤可溶性盐总量比裸露地降低了73%,其差异显著(P<0.05),随着杨树年龄的增长,土壤pH值及水溶性盐总量趋于降低。土壤颗粒分形维数与粉黏粒、土壤有机质、速效钾、全氮、有效磷、碱解氮、HCO_3^-等土壤理化参数呈显著正相关关系,与粗砂粒、Ca^(2+)、Mg^(2+)、SO_4^(2-)、Cl^-、K^++Na^+等呈显著负相关,与全磷和pH值相关性不大(P>0.05)。研究表明,柯柯牙人工防护林水土保持措施对土壤改良效益显著,随着种植年限的延长其效果越来越明显。

To investigate soil particle fractal dimension（D） characteristics and the main affecting factors, we took soil samples from different ages of P. pyramidalis forest of the Kokyar protection forest in the Aksu suburb of Southern Xinjiang. Results showed that the mean D value of soil at different aged P. pyramidalis ranged from 2.2693 to 2.7104 and was significantly higher（P〈 0.05） than that at bare land（2.0545）. It decreased in the order of 22 years 15 years 6 years. Soil D values in 22 years old of P. pyramidalis land was higher at the depths of 10-30 cm and 30 -50 cm. D values in all soil layers of other aged forest showed little change（P〈 0.05）. The soil nutrient content in the protective forest was higher than that in the bare land, and it increased with the forest age. The total amount of soluble salt significantly（P〈 0.05） decreased by 73% compared with in the bare land. The pH value and the total amount of water-soluble salts tended to decrease with increasing forest age. It was positively correlated with silt-clay content, soil organic matter, available potassium, total nitrogen, available phosphorous, alkaline hydrolysis nitrogen, HCO3^-, but negatively correlated with coarse sand, Ca^2＋,Mg^2＋,SO4^2-,Cl^-,K^＋＋Na^＋. The D value of soil particle was not significantly correlated with the total phosphorus and pH value（P〈 0.05）. The soil and water conservation measures for artificial protection forest improved soil environment in the Kokyar peri-urban area, and the effect was more obvious with the planting years.