沙棘-桑树人工混交林对铁尾矿土壤的改良效益分析

通过测定与调查铁尾矿区营建沙棘-桑树人工混交林的土壤理化性质、养分含量及分布,评价人工混交林对铁尾矿区土壤改良的作用。与新尾矿区土壤相比,沙棘-桑树混交林下尾矿土壤容重与毛管孔隙度分别减小5.85%、5.04个百分点,空气孔隙度和自然含水量分别增加了10.97、1.35个百分点,混交林下尾矿土壤0～40 cm土层的平均相对含水量比新尾矿土壤增加12.90个百分点,表明混交林植物根系的生长促使原来致密的尾矿砂土的物理性质得到有效改善。混交林对尾矿碱性土壤的改良作用明显,且桑树的改良作用优于沙棘。混交林下尾矿土壤中的有机质含量增加,为对照新尾矿土壤的7.22倍,有机质含量随土层加深而递减,且均有一定的表聚性,主要分布在0～20 cm土层;但混交林下尾矿土壤中的有机质含量仍然较低,仅是该区域对照山地天然灌丛土壤的17.15%。混交林下尾矿土壤速效态大量元素的含量依次为速效P>速效K>碱解N,全量为K>P>N,其中沙棘根系周围土壤中的全N、全P、全K含量高于桑树,而桑树根系周围土壤中的全Ca和全Mg平均含量略高于沙棘。依据上述结果认为,沙棘-桑树人工混交林可有效改良铁尾矿土壤的理化性质,增加土壤养分含量。

An Analysis on Improvement Benefits of Hippophae rhamnoides and Morus L.Mixed Plantation to Soil of Iron Tailings

Soil physical and chemical properties and nutrient content and distribution of Hippophae rhamnoides L.and Morus L.mixed plantation on iron tailings were determined to evaluate improvement benefits of artificial mixed plantation to soil of iron tailings.Compared with control new iron tailings,the bulk density and capillary porosity of soil under the mixed plantation had reduced by 5.85% and 5.04 percentage points respectively,air porosity and natural moisture content had increased by 10.97 and 1.35 percentage points respectively,and average relative water content in 0～40 cm soil layers had increased by 12.90 percentage points,all of which showed that the growth of plant root systems of the mixed plantation had brought an effective improvement to physical property of the original dense sandy soil of iron tailings.The mixed plantation had a remarkable effect on modifying soil alkalinity of iron tailings.Morus L.had a better effect on soil alkalinity modification than Hippophae rhamnoides L.The organic matter in soil under the mixed plantation had been significantly increased,being 7.22 times to that of the control new iron tailings.Soil organic matter content decreased with depth of soil layer,displaying certain surface aggregation tendency.Organic matter was mainly distri-buted in 0 ～ 20 cm soil layers.However,the organic matter content in soil under the mixed plantation was still quite low,being only 17.15% to that of soil under the natural hilly bush.The content of major available nutritional elements in soil under the mixed plantation was in the order of available P>available K>alkaline hydrolyzed N.The whole quantity of major elements was in the order of K>P>N.The content of total N,total P and total K in soil surrounding root system of Hippophae rhamnoides L.was higher than that of Morus L.respectively,while the average content of total Ca and total Mg in soil surrounding root system of Morus L.was slightly higher than that of Hippophae rhamnoides L respectively.The above results suggest that Hippophae rhamnoides L.and Morus L.mixed plantation could remarkably improve soil physical and chemical properties and increase soil nutrient contents.