典型耕作土壤团聚体力稳性的区域分异特点及其影响因素

    Regional variation and its influencing factors for the aggregate mechanical stability of typical cultivated soils

    • 摘要: 土壤团聚体力稳性直接影响根系生长和农业耕作等过程。为探究不同类型土壤团聚体力稳性的区域分异规律,自北向南选取典型农业种植区耕作土壤(黑土、褐土、红壤和砖红壤),通过抗压试验测定不同粒径团聚体(1~2、3~5、>5~8、>8~10 mm)的抗张强度、破碎能量和易碎性指数,分析其与土壤理化性质和气候因子间关系。结果表明:抗张强度和破碎能量自北向南逐渐减小,并随团聚体粒径增大而减小,但具体变化特征因土壤类型而异。易碎性指数自北向南先增大后减小,其中红壤最大(0.87),黑土最小(0.47);相比温带地区黑土和褐土,亚热带和热带的红壤和砖红壤易碎性指数的粒径分异更为明显,表现为其小粒径团聚体易碎性指数(1.10和0.76)显著高于大粒径团聚体(0.65和0.58)。抗张强度和破碎能量与蛭石呈极显著正相关关系(r=0.73和0.70,P<0.01),与年均降水量呈极显著负相关关系(r=−0.72和−0.72,P<0.01);易碎性指数与年均降水量呈极显著正相关关系(r=0.66,P<0.01),与蛭石、碳氮比、非晶形氧化锰呈极显著负相关关系(r=−0.75~−0.66,P<0.01),表明在区域尺度上气候因子通过黏土矿物控制团聚体力稳性的空间分异。研究结果为不同区域农业土壤质量的评估与改良提供了理论依据。

       

      Abstract: Aggregate mechanical stability greatly influences plant root growth, energy efficiency and ease of tillage, wind and water erosion. A mechanistic understanding of soil aggregate mechanical stability is of great significance for evaluating and improving soil quality. To date, how aggregate mechanical properties vary over different types of soils remains poorly understood. To this end, four cultivated soils including Black soil, Cinnamon soil, Red soil, and Latosol were separately selected in typical agricultural producing areas from the north to south in eastern China. The objectives of this study was to investigate the difference of aggregates among differet typical arable soils in China and its influential factors. The soil samples were collected from the top 20 cm. Tensile strength, specific rupture energy, friability index of different aggregate sizes (1-2, >3-5, >5-8, >8-10 mm) were calculated and measured by a compression test to analyze their relationships with soil physicochemical properties and climate factors. The results were shown as follows: Tensile strength and specific rupture energy decreased gradually from north to south and decreased with increasing aggregate size. The tensile strength of 1-2 mm aggregates (a mean value of 661.5 kPa) was significantly higher than that of ≥3 mm aggregates (a mean value of 240.3 kPa); there was no significant difference between the tensile strength of >5-8 mm and >8-10 mm aggregates (P>0.05). The specific variation of specific rupture energy differed with soil types. The friability index increased first and then decreased from south to north, with the highest and lowest values in red soil (0.87) and black soil (0.47), respectively. Compared to the Black and Cinnamon soils in temperate zones, the variations of friability index among aggregate sizes were more remarkable for Red soil and Latosol in subtropical and tropical zones, where friability index was larger for small aggregates (1.10 and 0.76) than for large aggregates (0.65 and 0.58). Tensile strength and specific rupture energy were correlated positively with vermiculite (r=0.73 and 0.70, P<0.01), while correlated negatively with mean annual precipitation (r=−0.72 and −0.72, P<0.01). In addition, The tensile strength also showed significant negative correlations with free aluminum oxides, 1.4 nm intergrade mineral, and mean annual temperature (r=−0.67-−0.66, P<0.01). The friability index was correlated positively with mean annual precipitation (r=0.66, P<0.01), while correlated negatively with vermiculite, carbon-nitrogen ratio, and amorphous manganese oxides (r=−0.75-−0.66, P<0.01), indicating that climate factors controlled the spatial differentiation of aggregate mechanical stability through the type of clay minerals and the content of metal oxides at the regional scale. Stepwise regression analysis showed that aggregate size, vermiculite or mean annual precipitation, and amorphous manganese oxides were good indicators to predict aggregate mechanical stability (R2adj≥0.47, P<0.01). The obtained results provide the valuable information for the prediction and improvement of agricultural soil quality across different climate zones.

       

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