坝上地区典型防护林土壤改良效益

Improvement Benefits on Soil of Typical Shelterbelt Stands in Bashang Area

以御道口牧场4种典型防护林(樟子松纯林、落叶松纯林、樟子松-落叶松混交林、樟子松-榆树混交林)为研究对象,裸露沙地为对照,运用野外取样与室内试验相结合的方法,对各林分林下土壤的理化性质及其空间变化特征进行了分析。结果表明:4种防护林对土壤质地、土壤密度、土壤有机质、全量养分、速效养分及土壤pH值均有显著的改良作用,但各林分的改良效果具有差异性。除了土壤pH值,各林分对土壤理化性质的改良有相似的规律,樟子松-榆树混交林的改良作用最好,樟子松-落叶松混交林次之,樟子松纯林、落叶松纯林最差;各林分的土壤均有一定程度的酸化,但樟子松-榆树混交林土壤的酸化程度最小,几乎接近中性,适合植物的生长。土壤中粉粒、黏粒质量分数由表层(0~10 cm)到深层都呈降低趋势,砂粒呈增加的变化趋势;土壤密度和土壤pH值随着土层厚度的加深而逐渐增大;土壤有机质、全量养分(全氮、全磷、全钾)、速效养分(碱解氮、速效磷、速效钾)的质量分数随着土壤厚度的增加,均呈降低趋势土壤粒径<0.25 mm的质量分数与土壤各养分指标均呈正相关,但显著性水平不统一;土壤密度与全磷、全钾、碱解氮、速效磷、速效钾的质量分数呈显著负相关;土壤有机质与全氮、全钾、碱解氮、速效钾质量分数呈显著正相关。

Taking four typical shelter forests(I. Pinus sylvestris var. mongolica pure forest,Ⅱ. Larix gmelinii pure forest,Ⅲ. mixed forest of Pinus sylvestris var. mongolica and Larix gmelinii , IV. mixed forest of Pinus sylvestris var. mongolica and Ulmus pumila ) in Yudaokou Ranch as the research objects, the bare sandy land was used as the control. Combining field sampling with laboratory experiments were applied to study the physical and chemical properties and spatial variation characteristics of different forests. The four shelterbelts had significant improvement effects on soil texture, soil bulk density, soil organic matter, total nutrients, available nutrients and soil pH value, but the improvement effects of the four shelterbelts were different. In addition to soil pH value, the improvement of soil physical and chemical properties of each forest had similar rules, that was, the improvement effect descending order was IV,Ⅲ, and I equal to Ⅱ. Soil acidification of each stand was with some extent, but the acidification degree of IV forest was the smallest and almost neutral, which was suitable for plant growth. From surface layer (0-10 cm) to deep layer, the contents of silt and clay were decreasing, while the content of sand was increasing. With the increase of soil depth, soil bulk density and soil pH value gradually increased, while soil organic matter content, total nutrient content (total nitrogen, total phosphorus, total potassium), available nutrient content (alkali-hydrolyzed nitrogen, available phosphorus, available potassium) increased. The correlation analysis showed that the content of soil particle size <0.25 mm was positively correlated with all soil nutrient indicators, but the significant level was not uniform. Soil bulk density was negatively correlated with total phosphorus, total potassium, alkali-hydrolyzed nitrogen, available phosphorus and available potassium. Soil organic matter was positively correlated with total nitrogen, total potassium, alkali-hydrolyzed nitrogen and available potassium.