基于土地利用变化的热带植物群落功能性状与土壤质量的关系

为了明确热带天然林转变为橡胶林和槟榔后土壤质量变化,揭示土地利用变化下植物群落功能性状对土壤质量影响。在海南中部山区,以原始林(PF)、次生林(SF)、槟榔(Areca catechu)林(AP)、纯橡胶(Hevea brasiliensis)林(RP)和橡胶益智(Alpinia oxyphylla)林(RAP)为对象,探索天然林退化后土壤性质和质量变化,分析了植物群落功能性状(凋落物量、郁闭度、根长密度、细根密度和比根长)对土壤质量影响。结果表明:1)与原始林相比,其他土地利用类型凋落物量、根长密度、细根密度、土壤总孔隙度、最大持水量、土壤有机碳和总氮显著降低,土壤容重显著增加。人工林土壤碱解氮明显降低,但总磷、总钾和缓效钾明显升高(P0.05)。2)与原始林相比,次生林、槟榔林、纯橡胶林和橡胶益智林土壤质量指数分别降低63.4%、85.8%、81.2%和84.1%,随原始林、次生林和人工林梯度土地利用强度的增加,土壤质量显著降低(P0.05),但人工林间土壤质量无显著差异。3)凋落物量、郁闭度、根长密度和细根密度均与土壤质量指数显著正相关(P0.05),细根密度对土壤质量的直接影响效应最大,凋落物间接影响效应最大。天然林转变为橡胶和槟榔林显著改变土壤性质和质量,群落性状细根密度和凋落物可较好解释土壤质量变化,强化人工林林下植被和凋落物管理有利于土壤质量改善。

Relationships between plant community functional traits and soil quality based on land use changes in tropical region

To reveal the effects of plant community functional trait changes, resulted from the land use conversion from primitive forest to secondary forest or plantations, on soil quality in tropical region, an investigation was conducted in five typical land use types in the central mountainous area of Hainan Island. The land use types include primitive forest (PF), secondary forest (SF), areca plantation (AP), pure rubber plantation(RP) and rubber intercropping Alpinia oxyphylla plantation (RAP).The changes of soil qualities after the natural forest conversion to secondary forest or plantations and the relationships between plant community functional traits (litter fall, canopy density, root length density, fine root density, and specific root length) and soil quality were analyzed. Compared with those of primitive forest, the litter fall, root length density, fine root density, total soil porosity, maximum water holding capacity, soil organic carbon, and total nitrogen of other land use types decreased significantly (P < 0.05), but soil bulk density increased significantly(P < 0.05). Soil alkaline hydrolysis of nitrogen in all plantations decreased obviously, whereas soil total phosphorus, soil total potassium, and slowly available potassium increased significantly(P < 0.05) during the conversion. With increasing of land use intensity, the soil quality decreased significantly(P < 0.05). The soil quality indexes of SF, AP, RP, and RAP decreased by 63.4%, 85.8%, 81.2% and 84.1%, respectively, compared with that of PF. However, there were no differences in soil quality among the plantations. The litter fall, canopy density, root length density, and fine root density had the positive and significantly correlations with the soil quality index(P < 0.05). Moreover, fine root density had the largest direct effect on soil quality, and litter had the largest indirect effect. Our results suggested that the transformation of tropical primitive forests to rubber and areca plantations significantly changed soil properties and soil quality, which was mainly explained by the plan community functional traits of fine root density and litter fall. Improving the management of litter fall and understory plant community, which influences fine root density, will help increase soil quality in plantations in tropical region.