桂西北典型土壤有机碳矿化对碳酸钙与水分含量的响应

Responses of organic carbon mineralization in typical soils in northwest Guangxi of China to calcium carbonate and soil moisture

为了研究碳酸钙存在条件下水分对桂西北典型土壤有机碳矿化的影响,本文以添加定量Ca^14CO_3(50 g·kg^(-1)干土)的喀斯特地区棕色石灰土和地带性红壤(对照)的表层土(0~15 cm)为研究对象,进行100 d的室内培养实验,研究了3个水分梯度(30%、65%、100%WHC,分别记为W1、W2、W3)、25℃条件下土壤有机碳的矿化特征。结果表明:经培养100 d后,在3个水分条件下,来源外源碳酸钙的~14C-CO_2占棕色石灰土和红壤土壤表观累积矿化量的贡献率分别为9.64%、6.01%、7.63%和34.05%、27.73%、24.18%;棕色石灰土和红壤有机碳矿化速率(累积矿化量)分别表现为W2>W1>W3(P<0.05),W2、W3>W1(P<0.05);土壤含水量、土壤类型以及两者的交互作用均对土壤有机碳矿化速率、土壤有机碳累积矿化量有显著影响。因此,研究富含碳酸盐土壤的有机碳矿化,尤其是喀斯特地质背景发育的石灰土,应考虑水分和无机碳酸盐分解对有机碳矿化的作用,并将这种作用纳入C循环的模型中,才能准确评估土壤无机碳对有机碳碳库的影响。

In order to understand the effects of soil moisture on organic carbon （OC） mineralization in two typical soils in Northwest Guangxi of China under the existence of calcium carbonate, a 100day incubation experiment with the topsoil （0-15 cm） of terra fusca in Karst region and of zonal red soil （as a control） was conducted to study the characteristics of soil OC mineralization under the conditions of three soil moisture gradients （30%, 65%, and 100% waterholding capacity; W1, W2, and W3） and a fixed added calcium carbonate quantity （50 g Ca14CO3·kg-1 dry soil） at 25 ℃. After 100day incubation, the contribution rate of the 14CCO2 from added calcium carbonate to the apparent accumulative mineralization amount under W1, W2, and W3 was 9.64%, 6.01%, and 7.63% for the terra fusca, and 34.05%, 27.73%, and 24.18% for the red soil, respectively. The soil OC mineralization rate and accumulative mineralization amount were in the order of W2 〉 W1 〉 W3 （P〈0.05） for the terra fusca, and of W2, W3 〉 W1 （P〈0.05） for the red soil, respectively. Soil moisture, soil type, and their interaction had significant effects on the soil OC mineralization rate and accumulative mineralization amount （P〈0.05）. Therefore, when studying the OC mineralization in carbonate-rich soils, especially for the calcareous soils developed in Karst geological background, it would be necessary to consider the effects of soil moisture content and inorganic carbonate decomposition on the soil OC mineralization, and to incorporate these effects into C cycle model to accurately assess the effects of soil inorganic carbon on the soil OC pool.