海拔梯度及典型土地利用类型对北热带山地土壤有机质和综合肥力的影响

为深入了解北热带海拔梯度各山地土壤带及典型土地利用类型（次生林、香蕉园、橡胶林）土壤有机质（SOM）、综合肥力（SIF）分布特征，以云南省金平县蝴蝶谷地区为例，区分表层（0～20 cm）和亚表层（20～40 cm），测定SOM、pH、全氮、全磷、全钾和速效氮磷钾，采用修正内梅罗指数法评价SIF，分析限制SIF的关键因素。结果表明，研究区海拔与SOM、SIF呈显著正相关，6个山地土壤带表层和亚表层SOM、SIF排序为棕壤带>黄棕壤带>黄壤带>红壤带>赤红壤带>砖红壤带（P<0.05）。无论表层还是亚表层，SOM和SIF均以次生林最大，香蕉园次之，橡胶林最小，次生林SOM显著大于香蕉园和橡胶林（P<0.05）,SIF则无显著差异。随着海拔升高，限制SIF的因素由速效氮、速效磷转变为速效磷和速效钾，且pH的限制逐渐加强，而维持和限制低海拔不同土地利用类型SIF的因素与同海拔段内自然土壤基本一致。未来山地开发利用过程中低海拔区域应该注重补充氮肥和磷肥，中高海拔区域注重补充磷肥和钾肥，同时调节适宜的pH更有助于土壤养分释放和植物吸收利用。综上，海拔梯度和...

The Effects of Altitude and Land Use on Organic Matter and Integrated Fertility of Soils in the Northern Tropics Mountain

This study was conducted to gain insight into the distribution characteristics of Soil Organic Matter (SOM) and Soil Integrated Fertility (SIF) in various mountain soil zones and several typical land use types (secondary forest, banana plantation, and rubber plantation) on different altitude gradients in the northern tropics and the Butterfly Valley area in Jinping County, Yunnan Province, China. The surface (0-20 cm) and subsurface (20-40 cm) layers are distinguished. SOM, pH, total N, total P, total K, and available N, P, and K were measured. The SIF was evaluated using the modified Nemorow index method, and the key limiting factors were analyzed. First, the results show that the SOM content ranges from 21.91 to 120.67 g/kg for the surface layer and 16.38 to 101.88 g/kg for the subsurface layer, with the mean SOM of the surface layer (75.32 g/kg) greater than that of the subsurface layer (51.57 g/kg, P > 0.05). In terms of SIF, that of the surface layer was 1.15-1.59 and that of the subsurface layer was 0.94-1.44, with the mean SIF of the surface layer (1.35) greater than that of the subsurface layer (1.16). This shows that there is a significant positive correlation between the altitude gradient and SOM as well as SIF. Ranking of SOM and SIF for the surface layer (P < 0.05). Second, the SOM for the surface layer of the secondary forest, banana plantation, and rubber plantation were 26.61, 13.48, and 11.91 g/kg, respectively, while the SOM for the subsurface layer of these three typical land use types are 19.28, 9.61, and 8.91 g/kg, respectively. With regard to SIF, they were 1.48, 1.33, and 1.21 for the surface layer, and 1.17, 1.10, and 0.94, respectively. Notably, both in the surface and subsurface layers, the SOM and SIF were largest in the secondary forest, followed by the banana plantation, and then the rubber plantation. The SOM of the secondary forest was significantly greater than that of the banana and rubber plantations (P < 0.05), whereas there was no significant difference among the SIF of these three land use types. Finally, as the altitude increased, the factors limiting the SIF change from available N and available P to available P and available K, and the effect of pH gradually strengthened. The factors that maintain and limit the SIF of different land use types at low altitudes are generally consistent with natural soils at the same altitude. Therefore, in the process of future mountain development and utilization, it is important for low-altitude areas to supply nitrogen and phosphate to the soil. In medium- and high-altitude areas, supplementation with phosphate and potash is useful, and a suitable pH helps the soil release nutrients and promotes plant uptake and utilization.