岩溶区不同土地利用方式土壤碳、氮、磷生态化学计量的空间变异性研究

Spatial variability of soil carbon,nitrogen and phosphorus ecological stoichiometry of different land uses in karst area

【目的】探究岩溶区土壤C、N、P生态化学计量特征的空间分异格局对土地利用方式的响应规律,为揭示岩溶生态系统各组分之间的养分循环规律及阐明系统的稳定性提供科学参考。【方法】在广西马山县西部岩溶区分别采集水田、旱地、草地、灌木林地和树木郁闭度≥20%的有林地等土地利用方式的表层(0~20 cm)土壤,测定其有机C、全N和全P等含量,并运用统计学方法分析不同土地利用方式下土壤的C、N、P生态化学计量特征、空间变异性及影响因素。【结果】研究区土壤有机C、全N和全P含量均值分别为13.83、1.75和0.92 g/kg,C∶N、C∶P和N∶P均值分别为7.95、18.79和2.28。土壤C∶N、C∶P、N∶P空间分布和土地利用基本一致,高值区位于水田和有林地,低值区分布在旱地、灌木林地和草地。不同土地利用方式下土壤C∶N平均值集中分布在7.13~9.26,变异系数为20.84%,C∶N较稳定,在空间上存在中等程度的变异性。水田和有林地之间C∶N差异不显著(P>0.05,下同),旱地、灌木林地和草地之间C∶N差异也不显著,变化趋势为水田>有林地>旱地>灌木林地>草地;C∶P为11.21~29.10,N∶P为1.51~3.11,变异系数较大,两者在不同土地利用方式下的变化趋势均为水田>有林地>灌木林地>草地>旱地。土壤C∶N、C∶P、N∶P与有机C、全N、全P、全K、pH均存在极显著相关性(P<0.01)。土壤理化性质和环境因子在不同土地利用方式土壤C、N、P化学计量特征冗余分析排序图上表现出不同的相关性,其中,有效P在所有土地利用方式中均与土壤C∶N、C∶P、N∶P呈显著负相关(P<0.05,下同),而碱解N、成土母质在所有土地利用方式中均与C∶N、C∶P、N∶P呈显著正相关;pH在水田、旱地和有林地土壤中与C∶N、C∶P、N∶P呈显著负相关,而在灌木林地和草地土壤中呈显著正相关。【结论】研究区普遍缺乏有机质和N,P元素相对丰富,但其变异系数较大。碱解N、有效P、pH和成土母质是影响研究区不同土地利用方式下土壤C、N、P生态化学计量的关键因子。

【Objective】Exploring the spatial variability of soil carbon(C),nitrogen(N),phosphorus(P)and ecological stoichiometry under different land uses in karst area,to reveal the Nutrient cycling regulation among different components of karst eco-system and explaining the stability of the system.【Method】Surface soil(0-20 cm)in paddy fields,dry land,grassland,shrub land,and forest land with a canopy density of 20%or more were collected in the western karst area of Mashan County,Guangxi,and the contents of soil organic C,total N and total P were determined.The ecostoichiometric characteristics,spatial variability and influencing factors of ecological stoichiometry of C,N and P uner different land uses were studied by statistical methods.【Result】The results showed that,the average content of soil organic C,total N and total P in the study area were 13.83,1.75 and 0.92 g/kg respectively.The average soil C∶N,C∶P,N∶P were 7.95,18.79 and 2.28 respectively.The spatial distribution of soil C∶N,C∶P,N∶P was consistent with land use,high value areas were located in paddy fields and forest land,low value areas were distributed in dry land,shrub land and grassland.The average C∶N concentration of soil under different land use patterns was between 7.13 and 9.26,and the coefficient of variation was 20.84%.C∶N was stable and had moderately variability in space.The difference of C∶N between paddy field and forest land was not significant(P>0.05,the same below).The difference of C∶N between dry land,shrub land and grassland was not significant too,and the change trend was paddy field>forest land>dry land>shrub land>grassland;C∶P was 11.21-29.10,N∶P was 1.51-3.11,and the coefficient of variation was large.The trends of the C∶P and N∶P under different land use patterns were paddy field>forest land>shrub land>grassland>dry land.Soil C∶N,C∶P,N∶P and organic C,total N,total P,total potassium,pH existed extremely significant correlation(P<0.01).Ordination diagram of redundancy analysis of soil C,N,P and properties and environmental factors showed different correlations in different land uses.Available P was significantly negatively correlated with soil C∶N,C∶P,N∶P in all land uses(P<0.05,the same below),while alkali N and soil parent materials were significantly positively correlated with C∶N,C∶P and N∶P in all land uses.pH was significantly negatively correlated with C∶N,C∶P,N∶P in paddy fields,dry land,and forest land,but significantly positively correlated in shrub land and grassland soils.【Conclusion】The soil in the study area were generally lacking in organic matter and N,while P is relatively abundant.However,the coefficient of variation of P is large.Alkali N,available P,pH,and soil parent material are key factors that affect soil C,N,P ecological stoichiometry in different land use types in the study area.