喀斯特不同土地利用方式和生态恢复模式的土壤磷素特征

Soil phosphorus characteristics of different land use types and ecological restoration modes in karst region

为了探究不同土地利用方式和生态恢复模式对喀斯特地区土壤磷素循环特征的影响,选择长期控制试验样地的3种土地利用方式(果树林(枇杷)、牧草地、退化干扰地)和4种生态恢复模式(常绿林、落叶林、常绿落叶混交林、自然恢复林)作为研究对象,分析了土壤磷素(全磷(TP)、有效磷(AP))含量、微生物生物量磷(MBP)变化及其与pH和有机碳(SOC)、全氮(TN)、铵态氮(NH_(4)^(+)-N)、硝态氮(NO_(3)^(-)-N)、交换性钙(Ca)、镁(Mg)含量、微生物生物量碳(MBC)和氮(MBN)的关系。结果显示:持续开发利用的土地土壤TP含量均高于生态恢复模式的土地,而MBP正好相反。在3种持续开发利用的土地中,牧草地土壤TP和AP含量显著高于果树林和退化干扰地,而MBP最低;果树林的土壤MBP最高,退化干扰地的土壤TP和AP含量最低。在4种生态恢复模式中,自然恢复林和落叶乔木林土壤AP含量和MBP显著高于常绿落叶混交林和常绿乔木林,TP含量则变化不大。土壤TP与SOC、TN和交换性Ca呈显著正相关,AP与pH、MBC、MBN、MBP和交换性Mg呈显著正相关,MBP与交换性Ca和Mg、MBC和AP呈显著正相关。冗余分析发现,土壤MBC、MBN是影响3种土地利用方式和4种生态恢复模式土壤磷素含量变化的主要因子,说明在喀斯特地区不同土地利用和恢复方式中,土壤微生物活动对土壤磷素有效性变化具有重要影响。另外,在3种持续利用的土地中,果树林的土壤下TP、AP和MBP含量较高,更接近于生态恢复模式下土壤状况,意味着这是较好的土地利用方式;4种生态恢复模式中,落叶乔木林的土壤TP、AP、MBP均高于常绿落叶混交林和常绿乔木林,更接近于自然恢复林。为了使生态系统更快恢复,可以在植被恢复区人为配植更多的落叶树种。

We explored the effects of land use types and ecological restoration modes on soil phosphorus(P) characteristics in karst ecosystems, with three land-use types(orchard(loquat), pastureland, and disturbed land) and four restoration modes(evergreen forest, deciduous forest, evergreen-deciduous mixed forest, and naturally restored forest) being selected. We measured soil phosphorus [(total phosphorus(TP), available phosphorus(AP) content, microbial biomass phosphorus(MBP)] and analyzed the relationships between the three P variables and soil pH, organic carbon(SOC), total nitrogen(TN), ammonium nitrogen(NH_(4)^(+)-N), nitrate nitrogen(NO_(3)^(-)-N), exchangeable calcium(Ca), magnesium(Mg), microbial biomass carbon(MBC), and nitrogen(MBN). Results showed that soil TP across different land-use types was higher than that across different restoration modes, while MBP showed an opposite pattern. Among the land-use types, pasture had the highest TP and AP and lowest MBP, orchard had the highest MBP, and disturbed land had the lowest TP and AP. Across the restoration modes, soil AP and MBP in the naturally restored forest and deciduous forest were significantly higher than those in evergreen-deciduous mixed forest and evergreen forest. Soil TP was not different among the four restoration modes and was positively correlated with SOC, TN, and exchangeable Ca. Soil AP was positively correlated with pH, MBC, MBN, MBP, and exchangeable Mg, while soil MBP was positively correlated with exchangeable Ca and Mg, MBC, and AP. Results of redundancy analysis showed that soil MBC and MBN significantly influenced the variations in soil P content across different land-use types and restoration modes, indicating that soil P availability in these karst ecosystems was extremely affected by soil microbial activities. The orchard had higher soil TP, AP, and MBP across three land-use types, with values approximating that in the naturally restored forest, suggesting that it would be an appropriate land-use type. The deciduous forest had higher soil TP, AP, and MBP than those in evergreen-deciduous mixed forest and evergreen forest, similarly to the naturally restored forest, which suggested that deciduous tree species can be planted in the recovered areas to enhance vegetation restoration in karst ecosystems.