新乡毛白杨人工林土壤性质垂直分布特征

Vertical Distribution Characteristics of Soil Properties of Populus tomentosa Plantation in Xinxiang

2020年10月份,以新乡市16年生毛白杨(Populus tomentosa)人工林地土壤为研究对象,在样地内按梅花型设置5个取样点,每个样点按照土层深度(h)用环刀分别采集0<h≤20 cm、20 cm<h≤40 cm、40 cm<h≤60 cm、60 cm<h≤80 cm土层的土样;测定土壤密度、田间持水量、毛管持水量、土壤碱解氮(水解性氮)质量分数、pH、有机碳质量分数等理化指标,计算土壤各粒级团聚体的质量百分比(P_(i))、平均质量直径(D_(MW))、几何平均直径(D_(GM));应用单因素方差分析法、皮尔逊(Pearson)相关性分析法,分析不同土层土壤理化指标的差异。结果表明:毛白杨林地0~80 cm土层,土壤密度随土层加深而增大,毛管孔隙度、总孔隙度、田间持水量、毛管持水量随土层加深而减少。土壤碱解氮质量分数随土层加深整体下降幅度较大,下一层较上一层的降幅分别为33.45%、44.60%、20.86%,0<h≤20 cm土层碱解氮质量分数最高(82.30 mg/kg)。土壤有机碳质量分数在11.52~28.67 g/kg之间,呈表聚效应;各土层间土壤有机碳质量分数差异显著(P<0.05)。0~80 cm土层,土壤呈碱性,pH均值为8.41,各土层间土壤pH无明显规律。粒径大于0.25 mm的团聚体、土壤平均质量直径、几何平均直径均随土层深度的增加而降低,微团聚体(粒径<0.25 mm)随土层的加深而增多,各土层超大团聚体(粒径>2 mm)占土壤团聚体总质量比例都最高,在49.60%~65.80%之间。粒径大于0.25 mm的团聚体、土壤平均质量直径、几何平均直径,与土壤有机碳均呈显著正相关(P<0.05)。综合看,毛白杨人工林土壤,养分质量分数较低、持水量不高、土壤偏碱;可通过营造混交林、建立林草复合生态系统,增施有机肥等措施加以改良。

The soil of 16-year-old Populus tomentosa plantation in Xinxiang City was taken as the research object in October,2020,and five sampling points were set in the sample plot according to plum blossom pattern.According to the depth(h)of the soil layer,0<h≤20 cm,20 cm<h≤40 cm,40 cm<h≤60 cm and 60 cm<h≤80 cm were collected at each sampling point with cutting ring.Physical and chemical indexes such as soil density,field water capacity,capillary water capacity,soil alkali-hydrolyzable nitrogen(hydrolyzable nitrogen)contents,pH value and organic carbon content were measured,and the mass percentage(P_(i)),average weight diameter(D_(MW))and geometric average diameter(D_(GM))of soil aggregates of various fractions were calculated.The differences of soil physical and chemical indexes in different soil layers were analyzed by single factor variance analysis and Pearson correlation analysis.The results showed that the soil density in the 0-80 cm soil layer of P.tomentosa forest land increased with the deepening of the soil layer,while the capillary porosity,total porosity,field capacity and capillary capacity decreased with the deepening of the soil layer.The mass fraction of soil alkali-hydrolyzable nitrogen decreased greatly with the deepening of soil layer,and the decreases of the lower layer were 33.45%,44.60%and 20.86%,respectively,compared with the upper layer.The soil layer with 0<h≤20 cm had the highest content of alkali-hydrolyzable nitrogen(82.30 mg/kg).The content of soil organic carbon is between 11.52 and 28.67 g/kg,which shows the surface aggregation effect.There was a significant difference in soil organic carbon content between layers(P<0.05).The soil pH of 0-80 cm soil layer is alkaline,with an average value of 8.41,and there is no obvious law between layers.Aggregates larger than 0.25 mm,average weight diameter and geometric average diameter of soil decrease with the increase of soil depth,while micro-aggregates(<0.25 mm)increase with the increase of soil depth,and super-large aggregates(particle size>2 mm)in each layer account for the highest proportion of the total mass of soil aggregates,ranging in 49.60%-65.80%.Aggregates with particle size larger than 0.25 mm,soil average weight diameter and geometric average diameter are positively correlated with soil organic carbon(P<0.05).Generally,the soil nutrient content under P.tomentosa plantation is low,the water holding capacity is low,and the soil is alkaline,which can be improved by building mixed forest,establishing forest-grass complex ecosystem,adding organic fertilizer and other measures.