温室大棚土壤有机碳淋溶迁移研究

Exploring whether the soil organic carbon (SOC) in plastic greenhouse would leach to deeper soil layer or ultimately leak out of the ecosystem is vital to assess the carbon balance of the human-dominated ecosystem. Based on the previous research of carbon cycle, we focus on the SOC concentration of several greenhouse ecosystems of different cultivation years and put the research on the soil carbon leaching principle of plastic greenhouse ecosystems. We set up 3 pilots and each pilot selected five greenhouse ecosystems (with different cultivation years of 1, 10, 20, 25 and 30, respectively) and open-field. First we will sample plants, soil and fertilizer and test the abundance of 13C in the samples. The soil sampling depth is 100 cm and in each 20 cm as a soil layer. Soil pH, the concentration of the SOC and bulk density were measured; Meanwhile, the leaching simulation experiment was conduct to study the effect on SOC leaching process of different cultivation years, with measuring the dissolved organic carbon (DOC), pH and NH4+. The study was to clarify whether the SOC leaching take place between the different soil layer? And try to analyze how the soil organic carbon changes along with the cultivation years of the plastic greenhouse in each soil layer. Clarifying these issues is important to understand the carbon budget of a human-dominated system, which provides theoretical support for carbon emission reduction management.

探明温室大棚农业生态系统土壤有机碳是否存在淋溶下渗作用而进入深层土壤甚至最终离开系统，对评估该类人工生态系统碳平衡具有重要科学意义。本项目以前期温室大棚碳循环研究为基础，以土壤各土层有机碳变化为主线，以温室大棚不同种植年限为研究桥梁，进行温室大棚系统土壤有机碳淋溶迁移研究。研究拟选择3个样点，每个样点分别选择大棚种植年限为1年、10年、20年、25年、30年的大棚样地和附近露天菜地，测定各样地植物、土壤及肥料碳同位素δ13C，土壤取样深度为0-100 cm，每隔20 cm取一层，并测定各层土壤有机碳浓度、容重及pH。同时，采用原状土柱淋溶模拟实验，测定淋溶液的可溶性有机碳、pH和氨氮。研究旨在弄清温室大棚土壤有机碳是否存在淋溶下渗甚至进入深层土壤；并分析随温室大棚耕作年限延长，各层土壤有机碳密度变化规律，为研究此类人工生态系统碳收支提供理论参考，也为人与生态系统的互动与干扰研究提供新的思路

本项目通过测定温室种植系统土壤碳同位素13（δ13C）、土壤有机碳（SOC）、土壤pH值等，对比不同耕作年限温室各层土壤的SOC含量和δ13C的空间和时间尺度上的变化规律来分析淋溶机理，以探究温室生态系统碳循环情况。结果如下：（1）试验观测范围内所有耕作年限大棚表层土壤（0-20 cm）SOC均显著高于对应的底层（20-100 cm）土壤（p < 0.01），亚表层（20-40 cm）SOC含量次之，显著高于对应的下层（40-100 cm）土壤。所有耕作年限下温室40-60 cm、60-80 cm和80-100 cm之间SOC无显著变化。表层SOC含量高出亚表层47-87%，平均为58%。与露天系统相比，温室种植系统耕层（0-20 cm）土壤有机碳含量呈现增加趋势，平均增加41%。温室耕作系统 SOC随耕作年限不会无限制增加，而是呈现 SOC 含量先增后减，最后趋于平缓的变化规律，变化拐点出现在耕作年限15年左右。（2）通过对温室栽培作物及其土壤δ13C的测定，我们证实了土壤有机碳的淋溶路径的存在。在土壤0-100 cm的五个观测层内，δ13C值先减后增，表明地上植被转化为土壤有机碳后由耕层开始，随耕作年限的延长，通过淋溶作用，逐层下渗进入深部土壤。（3）温室种植系统各种植年限温室土壤0-20 cm淋溶液有机碳含量均高于与之对应的0-40 cm土壤层，此结果表明由0-20 cm 土壤层下渗的有机碳在下层（20-40 cm）部分受到截留。0-20 cm土层，SOC淋溶迁移量与温室种植年限无显著相关（P>0.05），0-40 cm 土层，SOC 淋溶通量与温室耕作年限则呈现负相关（P<0.01）；温室土壤0-2 cm和0-40 cm土壤层淋溶液中TN、NH4+-N的淋洗量分别与SOC的淋溶迁移量呈现显著正相关。（4）温室种植系统0-20 cm和20-40 cm土层pH逐渐降低，呈现酸化态势，酸化率分别为0.0661/yr和0.0173/yr；而40-60 cm、60-80 cm和80-100 cm土层随耕作年限增加，土壤pH并未发生显著变化。