滨海土壤盐渍化对秸秆腐解转化的影响与调控机制

Although saline soil improvement is being carried out with straw for a few years, little is known about the transformation of straw in saline soil currently. Especially, few researches were conducted on the effect of soil salinity on the transformation of organic carbon (C) from straw, which in turn caused the low improvement efficiency, and shortage of technical innovation. In this study, 13C labelled straw, molecular ecological and spectrum technologies were employed with coastal saline soil to investigate that (1) the effect of soil salinity on the decomposition procession of straw (decomposition rate, nutrient release and residue composition); (2) transformation of organic C from straw into soil organic C fractions and driving factors; and (3) soil microbial community changes with salinity and decomposition procession. The aims are to elucidate the effect of salinity on the transformation of straw and its mechanism; discover soil organic C fractions transformation, composition and influenced factors; and explore the efficient methods to regulate the transformation of straw in saline soils. The results can provide the theoretical supports for the technical innovation of saline soil improvement and fertilization cultivation. Hence, it is of great theoretical and practical significance for implementing national strategy of “storing grain in land”.

尽管利用秸秆进行盐渍化土壤改良已有多年，但盐渍化土壤中秸秆腐解转化过程尚不清楚，尤其是盐渍化对秸秆有机碳转化的影响及相关机制研究较为薄弱，致使秸秆改良效率受到限制，技术创新缺乏理论指导。本项目拟以滨海盐渍化土壤为研究对象，通过温室培养和田间试验，采用13C标记、分子生态及波谱分析技术，研究：（1）土壤盐渍化对秸秆腐解进程的影响（腐解速率、养分释放、及腐解残渣结构组成等）；（2）从质与量层面，分析秸秆有机碳向盐渍化土壤不同有机碳组分转化的过程及驱动机制；（3）盐渍化土壤微生物种群沿盐渍化程度及秸秆腐解进程的演变规律。从中阐明土壤盐渍化对秸秆腐解转化过程的影响及机制；揭示秸秆腐解驱动下，土壤不同有机碳组分的转化过程、结构特征及关键影响因素，探索调控秸秆腐解转化过程与归趋的有效途径。研究结果能为盐渍化土壤改良技术创新及肥力定向培育提供重要理论依据，对于国家“藏粮于地”战略实施具有理论和实践意义。

秸秆作为一种重要的盐渍化土壤改良材料，在国内外已有大量报道，而土壤盐渍化对秸秆腐解转化的影响还不清楚。本项目通过室内培养试验和田间试验，系统研究了秸秆腐解对土壤盐渍化的响应；秸秆腐解驱动盐渍化土壤微生物种群的变化规律；以及秸秆腐解对盐渍化土壤有机碳含量、分布与结构的影响及其机制。结果表明，土壤盐渍化能够显著降低微生物活性和秸秆腐解速率；秸秆腐解驱动下，土壤微生物生物量、活性显著增加，细菌、革兰氏阳性菌、革兰氏阴性菌、放线菌、真菌增幅分别为17.6–44.8%、10.0–26.1%、24.7–39.3%、14.1–34.0%、36.6–81.2%。添加氮磷养分能够显著增加秸秆腐解速率，28 d室内培养试验，秸秆残留量下降10%以上。秸秆腐解显著提高了土壤磷酸酶、β-糖苷酶、蛋白酶、脲酶活性，土壤磷酸酶、β-糖苷酶活性随氮磷养分施入量增加而增加，蛋白酶、脲酶呈现先增后降的变化趋势，大量施用氮磷养分，脲酶活性下降。氮磷养分添加能够显著降低秸秆矿化速率和CO2-C累积释放量，提高微生物碳利用效率（CUE），但CUE并未随氮磷施用量增加而增加。秸秆腐解显著增加了土壤有机碳、可溶性有机碳、微生物生物量碳、氨基糖含量，土壤大团聚体增加14.7–19.0%，平均质量直径提高13.4–28.9%。施用秸秆后，土壤及不同团聚体组分在3400 cm-1、1030cm-1处吸收显著增强，875cm-1处吸收相对减弱，1630cm-1 / 1030cm-1吸收比降低，表明秸秆腐解在增加土壤有机碳（质）含量的同时，惰性有机碳组分比例减少，有机碳库稳定性下降。同时，随盐渍化程度升高，875cm-1处吸收值显著增强。氨基糖含量占土壤有机碳含量的8.9–17.1%。微生物源可能不是盐渍化土壤有机碳固持主要途径；芳香基等惰性基团含量增加，提高有机碳稳定性，可能是土壤有机碳对盐渍化生境一种适应。