典型重构措施下复垦土壤碳通量及其生物调控机制

Soil respiration is an important part of the carbon cycle. A clear understanding of the response mechanisms between the reconstruction measures, soil respiration and driving factors is crucial for ecosystem carbon budget assessment and scientific management of reclaimed soil. The quantified response mechanism of carbon emission for the reconstruction soil is not comprehensive, the understanding of process is not uniform, and carbon budget assessment is uncertainty at present. On the basis of synchronous observation and theory analysis, with micro area test and indoor simulation, Spatio-temporal variation of soil respiration was studied, distribution and change of soil carbon flux was clarified, which would reduce the uncertainty for carbon flux calculation. Through isotope tracer technique and molecular biology, the relation research on plants, microorganisms and soil respiration was carried out, and regulation of soil carbon emission and absorption and transformation mechanism were deeply analyzed from the molecular scale. Using geostatistics and stepwise regression analysis, the synergistic effect mechanism of biology-soil nutrient-heat and water factors on soil respiration were studied, the main process and key factors control soil carbon emission were revealed, which would improve the level of cognitive for process and mechanism of carbon emissions. The results of the project would provide data support for the scientific management of reconstructed soil, and provide scientific data for the assessment of ecosystem carbon budget, and further enrich the theory of soil carbon cycle.

土壤呼吸是碳循环的重要环节。清楚认识重构措施、土壤呼吸、驱动因子相互之间的响应机制对于生态系统碳收支评估和复垦土壤的科学管理至关重要。当前重构土壤碳排放定量化响应机制研究不系统全面、过程认识不统一，碳收支评估不确定。据此拟以微区试验与室内模拟试验为平台，利用同步观测与理论分析相结合的方法，研究重构土壤呼吸在不同时空尺度上的变化规律，阐明重构土壤碳通量分布格局及其变化，降低碳通量计算的不确定性；利用同位素示踪技术与分子生物学的新方法，研究植物、微生物与土壤呼吸相互之间的关联性，从分子尺度深入探讨调控土壤碳排放和吸收转化联系机制；利用地统计学与逐步回归分析方法，研究生物-土壤养分-水热因子对土壤呼吸的协同作用机制，揭示控制重构土壤碳通量排放主要过程与关键因子，提升碳排放过程与机制的认知水平。项目成果将为重构土壤的科学管理提供数据支撑，为生态系统碳收支评估提供科学数据，进一步充实土壤碳循环理论。

为了探讨复垦土壤碳排放与重构措施、环境、生物等响应机制，本项目以江淮地区典型复垦农田生态系统为研究对象，研究了重构土壤呼吸在不同时空尺度上的变化规律及生物调控机制。研究涉及填充物为煤矸石和粉煤灰2种；处理有：煤矸石填充中有覆土厚度（GS-VI、GS-V、GS-IV）、矸石分级组合填充（GS-I、GS-II、GS-III、GS-V）；粉煤灰填充中有复垦年限（SY-10、SY-20、SY-30）、填充模式（PW-1、PW-2、PW-3、PW-4、PW-5）。结果表明，煤矸石或粉煤灰填充的生态系统土壤呼吸速率最佳监测时间为07:00～09:00和17:00～19:00两个时间段。典型重构措施下土壤呼吸速率在日、季节、作物生育期尺度上表现单峰变化，土壤碳排放日变化速率最高值出现在13:00～15:00，最低值出现的时刻出现在03:00～05:00。煤矸石填充不同复垦年限处理土壤碳排放日变化速率全年在0.12～4.37μmol·m-2·s-1之间波动，平均值为1.54μmol·m-2·s-1。粉煤灰填充不同处理土壤碳排放日变化速率全年在0.18～6.26μmol·m-2·s-1之间波动，平均值为2.07μmol·m-2·s-1。不同的处理土壤呼吸速率变化不同的。煤矸石填充实验中，覆土厚度表现为GS-V＞GS-Ⅳ＞GS-Ⅵ，不同粒径组分填充表现为GS-Ⅲ＞GS-Ⅱ＞GS-Ⅰ。粉煤灰填充实验中，土壤呼吸随复垦年限的增加呈递减趋势，复垦10年＞复垦20年＞复垦30年；填充模式处理表现为PW-2>PW-1>PW-5>PW-4>PW-3。煤矸石填充实验中土壤剖面碳排放速率GS-I、GS-II呈现表层低-中部高-底层低的分布特征，GS-Ⅲ和GS-Ⅳ则呈现表层高-中部高-底层低的分布特征；粉煤灰填充实验中复垦年限>20年土壤碳呼吸通量则呈现随土层深度增而加减小变化，复垦10年结果相反。植物生长和土壤微生物结构显著影响土壤呼吸速率。小麦季根系呼吸速率占土壤呼吸作用的31.9%～81.8%，玉米季根系呼吸速率占土壤呼吸作用的11.6%～81.0%。煤矸石填充处理中土壤呼吸强度与土壤细菌、真菌总数呈显著正相关，粉煤灰填充处理中土壤呼吸强度与土壤放线菌总数显著相关。0～10cm土壤温度和水分的变化能够解释83%的土壤呼吸变异。环境因子通过影响植物和微生物生长活性进而综合影响碳排放。