炼山和套种绿肥对桉树人工林下植物和土壤C:N:P化学计量特征的影响

【目的】研究炼山和套种绿肥对桉树人工林林下植物和土壤C、N、P化学计量特征的影响,阐明炼山和套种绿肥条件下桉树人工林林下植物与土壤C、N、P的作用关系。【方法】在凭祥市热带林业实验中心青山试验场测定炼山和套种绿肥(山毛豆)处理下的桉树人工林林下植物与土壤C、N、P生态化学计量特征的变化规律。【结果】桉树人工林林下植物灌上(灌木层地上部分)有机碳、全氮含量最高,全磷含量最低;土壤有机碳和全氮含量随土壤层次的加深而递减,而土壤全磷则呈表层土的含量最高,随后减少再逐渐回升的趋势。炼山处理降低了林下植物中的有机碳、全氮含量,尤其是草上(草本层地上部分)和灌上(P0.05),却提高灌下(灌木层地下部分)的全磷含量(P0.05);炼山降低0～60cm土层的有机碳及全磷含量,降低0～10cm土层的全氮含量,提高10～60cm土层的全氮含量。套种绿肥后,林下植物有机碳含量降低,灌木层的全氮含量提高;显著降低草本层的全磷含量,而显著提高灌上的全磷含量;显著降低0～10cm的土壤有机碳及全磷含量(P0.05),小幅度降低0～10cm、10～20cm土层的全氮含量(P0.05)。炼山+套种绿肥处理,土壤表层0～10cm有机碳和全氮含量显著提高,林下植物草上全氮和全磷含量显著增加(P0.05);与单一的炼山或套种绿肥处理恰好相反。炼山提高林下植物生态化学计量比值,却降低土壤生态化学计量比值;套种绿肥总体上提高林下植物的N∶P和C∶P,降低林下植物的C∶N和土壤生态化学计量比值;炼山+套种绿肥对土壤生态化学计量比影响显著,总体降低林下植物的生态化学计量比,尤其是草上及灌上组分(P0.05)。林下草本和灌木层植物的地上部分与土壤的生态化学计量比呈负相关关系。【结论】炼山和套种绿肥对桉树人工林林下植物与土壤C∶N∶P化学计量特征有显著影响,炼山+套种绿肥比单一处理的方式更有利于提高土壤表层0～10cm有机碳和全氮含量以及林下草本植物地上部分全氮和全磷含量。

Effects of Controlled Burning and Interplanting Tephrosia candida on Plant and Soil C: N: P Stoichiometry in Eucalyptus Plantations

[Objective] By studying the effects of controlled burning and interplanting green manure on the stoichiometry characteristics of understory and soil C, N and P in Eucalyptus plantations, the role and relationship of C, N, and P in understory plants and soil of Eucalyptus plantations under the conditions of controlled burning and interplanting green manure plant were clarified.[Methods] At the Qingshan Test Site of the Tropical Forestry Experimental Center in Pingxiang City, the changes in the ecological stoichiometry characteristics of understory plants and soil C, N, and P in the Eucalyptus plantations under the conditions of controlled burning and interplanting green manure plant (Tephrosia candida) were measured.[Results] The contents of organic carbon and total N concentration were the highest and the contents of total P concentration were the lowest in the understory plants of the Eucalyptus plantations (the aboveground part of shrub layers).The content of soil organic carbon and total N concentration decreased with the deepening of the soil layers.While the content of total P concentration in the soil was the highest in top layer soil, subsequently it declined and then gradually rose again.Controlled burning treatment reduced the content of organic carbon and total P concentration in the understory plants, especially on the upper part of the herb layer and the aboveground part of shrub layers (P < 0.05), but increased the total P concentration under the belowground part of the shrub layer (P < 0.05).The controlled burning reduced the content of organic carbon and total P concentration in 0-60 cm soil layer and the total N content in 0-10 cm soil layer, but increased total N concentration in 10-60 cm soil layer.Understory organic carbon decreased and total N in shrub layer increased in plantations with green manure plant interplanting.Meanwhile, interplanting green manure plant significantly decreased total P in herb layer but markedly increased total P in the aboveground part of shrub layer.Interplanting green manure plant also significantly decreased SOC and total P in 0-10 cm soil layer, slightly decreased total N in 0-10 cm and 10-20 cm layer.Interplanting green manure plant with the controlled burning significantly increased SOC and total N in 0-10 cm soil layer, and increased total N and total P in aboveground part of herb layer.This trend was exactly in contrast to that in controlled burning or interplanting green manure plant.Controlled burning increased the ecological stoichiometry ratio of the understory plants but decreased the soil ecological stoichiometry ratio.Interplanting green manure plant increased the N:P and C:P of the understory plants, but decreased C:N and soil stoichiometry ratio of the understory plants.Interplanting green manure plant with controlled burning significantly affected the soil ecological stoichiometry ratio and decreased the ecological stoichiometry ratio of the understory plants, especially that in the aboveground part of understory plants.The stoichiometry ratio in the aboveground part of understory plants was negative correlation with that in soil.[Conclusion] Controlled burning and interplanting green manure plant significantly affected the stoichiometry ratio of understory plants and soil.Interplanting green manure plant with controlled burning was more conducive to increase the content of organic carbon and total N in the soil surface and total N and total P in the aboveground parts of understory herb plants than the single treatment.