茶园土壤有机碳淋溶迁移研究

Exploring whether the soil carbon would leak to deeper soil layer or ultimately leak out of the ecosystem is important to assess the carbon budget of this system. Based on previous work, this project is proposed to investigate the soil carbon leaching principle of tea plantations. We will take soil carbon in tea plantations in Pu'er, Yunnan Province as an example. We will select 3 sites in the areas,then select tea plantation which cultivation age are 1,10,30 and 50 years old,and an adjacent forest plot for each sites. First we will sample leaves of dominated species, litters and soil and test δ13C. Sampling soil in each 20cm as a soil layer, and measuring soil pH, the concentration of the soil organic carbon and bulk density; Meanwhile,take undisturbed soil pilla to lab and they were treated with simulated the similar rainfall to study the effect on carbon leaching process in soils of different age tea plantation and forest, measure the dissolved organic carbon, dissolved inorganic carbon, pH and NH4+.We aim to clarify whether the carbon leaching take place between the different soil layer? In particular, new established tea plantations, the topsoil with high carbon content were buried under soil about 60cm deep. Whether these buried carbon would be leaching into the deeper soil? And try to analyze how the soil organic carbon changes along with the cultivation age of the tea plantation in each soil layer. Clarifying these issues is important to understand the carbon cycle of a human-dominated ecsystem and identify the cultivation management in favor of low carbon development.

探明人工生态系统土壤有机碳是否会因淋溶作用而下渗进入深层土壤或最终离开系统对评估生态系统碳得失很重要。本项目结合前期茶园碳循环的研究基础，拟以云南普洱茶产区的茶园土壤碳为研究对象，进行茶园土壤碳淋溶迁移研究。研究拟选择3个样点，每个样点选择栽培年限为1、10、30、50年的茶园和周边森林一块，测定各样地优势植物的叶、凋落物和各层土壤的碳同位素δ13C， 土壤按每20cm一层取样，并测定各层土壤pH、有机碳浓度及其容重；同时，采原状土柱到实验室模拟淋溶试验，测定淋溶液的可溶性有机碳、无机碳、pH和氨氮。旨在弄清各土层之间是否存在碳下渗迁移；特别是新建茶园时，含碳高的表层土被翻埋入60cm之下，这些被埋入的碳是否会淋溶下渗进入更深土层；并分析随茶园栽培年限的延长各土层碳密度的变化规律。探明这些问题对弄清人类主导的生态系统碳循环和找到低碳的栽培管理措施很重要。

本项目通过测定茶园土壤的碳同位素13（δ13C）、土壤有机碳（SOC）含量、土壤容重（BD）、土壤pH值等，对比不同植茶年龄茶园的各层土壤样品的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。结果如下：（1）砍伐森林建植茶园后，建植茶园10年内，40-120 cm土层的有机碳经历了一个有机碳的快速恢复期，但到33年时，该土层的有机碳仍然没有恢复到周边森林的同层碳浓度水平；在茶园建成20年后，茶园土壤有机碳的恢复和积累主要发生在0-60 cm的表土层。（2）通过对有机碳δ13C比率的分析，明确了茶园土壤的碳淋溶途径真实存在。坡上的位置是影响茶园淋溶通量的因子。坡顶茶园的碳淋溶损失可以忽略不计，坡中茶园的有机碳淋溶迁移缓慢，坡脚茶园有机碳淋溶损失较大。（3）各茶园有机碳淋溶迁移通量0-20 cm土层均高于0-40 cm土层，依次为5607.78 mg/m2和4358.27 mg/m2，说明20-40 cm土壤层截留了表层（0-20 cm）淋溶下来的22.28%的有机碳，但仍有有机碳迁移到40 cm土层以下。各植茶年龄的茶园的0-20 cm和0-40 cm土层SOC淋溶迁移损失通量均小于森林土壤，说明砍伐当地阔叶林建植茶园并未加剧了土壤碳的淋溶损失。20-40 cm土层SOC淋溶通量大小与植茶年龄呈负相关（P<0.05），说明植茶年龄的延长有利于减小有机碳淋溶损失而增加茶园的碳储存能力。（4）高密度种植（10000株/ha）的茶园，0-40 cm土层的pH随植茶年龄的延长而增加，碱化率分别为0.0158/yr，0.0140/yr；80-120 cm土层的pH则随植茶年龄的延长而降低，酸化率分别为-0.0161/yr和-0.0245/yr；低密度种植（5000株/ha）的茶园未发现酸化。低密度种植能够减缓茶园土壤的酸化。. 项目按计划完成了研究工作，并取得了预期研究成果。本项目目前发表研究论文8篇，其中SCI数据库收录4篇，累计影响因子达11.064，在中科院分区中，1篇属于Ⅱ区，2篇属于Ⅲ区。该研究为茶园生态系统的碳管理提供了科学依据。