白蚁筑巢对橡胶林土壤团聚体稳定性及其养分元素的动态影响

Dynamic impacts of termite mounds on soil aggregate stability and nutrient elements in rubber plantations

关键词:  培菌白蚁, 团聚体稳定性, 季节动态, 速效磷, 矿质元素

Key words:  fungus-growing termite, aggregate stability, seasonal dynamics, available phosphorus, mineral element

摘要:

为探究培菌白蚁作为“生态系统工程师”对热带人工林土壤质量的改良功能,该研究以西双版纳橡胶纯林内培菌白蚁巢穴为试验对象,通过对比相邻环境土壤,分析了白蚁巢穴顶部和基部土壤团聚体稳定性及不同粒级团聚体[大团聚体(>2 mm)、小团聚体(0.25～2 mm)、微团聚体(<0.25 mm)]养分含量的季节变化。结果表明:(1)旱季巢穴顶部微团聚体比例显著提高131.7%; 而雨季巢穴顶部和基部大团聚体比例分别降低19.6%和26.2%,小团聚体比例分别增加27.1%和42.6%。旱雨季巢穴相较于环境土壤均一定程度上降低了团聚体稳定性。(2)旱雨季巢穴均降低了各粒径团聚体的含水量、全磷和有效磷含量,顶部和基部平均降幅分别为38.2%和19.1%、15.3%和18.0%及35.6%和36.0%。各团聚体的可溶性有机碳含量旱季均显著高于雨季,铵态氮含量则相反。(3)旱雨季巢穴促进了各粒径团聚体全铝、全铁和全钾的富集,顶部和基部平均增幅分别为15.8%和14.2%、13.9%和13.4%及9.7%和9.1%; 旱季各团聚体的全铜、全锌和全硫的含量显著高于雨季。(4)随着团聚体粒径的减小,巢穴可溶性有机碳含量降幅高达72.7%,而有效磷含量增幅高达124.9%。综上认为,培菌白蚁筑巢对橡胶林土壤团聚体稳定性及其养分元素的影响受巢穴取样位置与季节的共同调控,并且时空异质性显著。该研究结果可为深入理解橡胶林中白蚁的生态功能定位和土壤可持续管理提供理论参考。

Abstract:

To explore the improvement function of fungus-growing termites as “ecosystem engineers” on soil quality in tropical plantations, this study compared termite mound soils(top and base positions)with adjacent environment soils from a mature rubber plantation in Xishuangbanna, Southwest China. Seasonal variations in soil aggregate stability and nutrient distribution within different aggregate sizes [megaaggregate(>2 mm), macroaggregate(0.25-2 mm), and microaggregate(<0.25 mm)] were analyzed. The results were as follows:(1)The percentage of microaggregates at mound tops increased significantly by 131.7% during dry season. During rainy season, the percentage of megaaggregates at mound tops and bases decreased significantly by 19.6% and 26.2%, respectively, while the percentage of macroaggregates increased by 27.1% and 42.6%. Compared to surrounding soils, mound soils exhibited reduced aggregate stability in both seasons to a certain extent.(2)Mound soils significantly reduced moisture, total phosphorus, and available phosphorus in each aggregate in both seasons, with average reductions of 38.2% and 19.1%, 15.3% and 18.0%, and 35.6% and 36.0% at the tops and bases, respectively. The content of dissolved organic carbon was higher in dry season than in wet season, whereas ammonium nitrogen exhibited the opposite trend.(3)Mound soils generally enriched total aluminum, total iron, and total potassium in each aggregate in both seasons, with average increases of 15.8% and 14.2%, 13.9% and 13.4%, and 9.7% and 9.1% at the tops and bases, respectively. Dry-season aggregates displayed significantly higher total copper, zinc, and sulfur than rainy-season counterparts.(4)As aggregate size decreased, the reduction in dissolved organic carbon content in mound soils reached as high as 72.7%, whereas the increase in available phosphorus content was as high as 124.9%. In summary, the impact of fungus-growing termites' nesting on soil aggregate stability and nutrient elements in rubber plantations is governed by mound sampling location and seasonal variation, demonstrating strong spatiotemporal heterogeneity. The results of this study can provide theoretical references for the ecological function positioning of termites in rubber plantations and the sustainable management of soil.