海拔高度对水稻覆膜旱作土壤碳氮转化和稳定性的影响

Water-saving Ground Cover Rice Production System (GCRPS) is an innovative techniue that uses significantly less water and reduce greenhouse gas emission than tradinational paddy rice cultivation system. However, on the one hand, reduction of soil moisture and increase of soil temperature and redox potential will accelerate soil catbon and nitrogen mineralization, leading to reduction in soil carbon and nitrogen stocks under GCRPS. On the other hand, soil carbon and nitrogen stocks might increase due to the increase of photosynthetic products into the plant root and of the water stable small aggregates as well as more stable structure of organic material allocated into the soil. However, with regard to the above-mentioned conflicting interpretations rarely reported so far in the literature. This project, from the view of earth science and agronomy, as well as environmental factors and soil conditions, reveal the influence of GCRPS on soil carbon and nitrogen transformation. The following three questions will be answered: ① Soil carbon and nitrogen stocks must be reduced under GCRPS? (2) How the temperature decrease cause by elevation increase and the soil temperature increase by using GCRPS will interactively affect the transformation and stability of soil carbon and nitrogen in GCRPS? ③ Can measurement of 13C and 15N natural abundance of plant soil samples in different altitues reveal the differences in soil carbon mineralization and nitrogen loss between the GCRPS and conventional paddy rice system? Does the above differences increase with the altitude? The results from this project will provide theoretical support for the sustainable development of water-saving GCRPS.

水稻覆膜旱作是解决稻田水资源短缺和温室气体排放等问题的有效技术措施之一。然而，水稻覆膜旱作后，一方面，土壤含水量降低、土温和氧化还原电位升高，将加速土壤碳氮矿化，导致土壤碳氮储量减少；另一方面，转移到根系的光合产物和土壤水稳性小团聚体数量增加、进入土壤的有机物料结构更趋稳定，则有利于土壤碳氮储量增加。关于上述相互矛盾的解释，至今鲜见报道。本项目将从地学、生物学、环境因子和土壤条件等，揭示水稻覆膜旱作体系不同海拔高度土壤碳氮转化规律。回答以下三个问题：①水稻覆膜旱作后，土壤碳氮储量是否一定降低？②海拔升高引起的气温下降和覆膜旱作引起的土温上升将如何影响覆膜旱作土壤碳氮转化和稳定性？③不同海拔高度土壤和植物样品13C和15N自然丰度的测定值，能否揭示覆膜旱作和常规淹水栽培体系之间土壤碳氮矿化和氮素损失的差异？上述差异会随海拔高度加大吗？上述成果将为水稻覆膜旱作节水减排和可持续发展提供理论依据。

通过研究不同海拔高度和覆膜年限下，水稻覆膜旱作体系中土壤碳氮储量和土壤理化性状、气温和土温差异、初级生产力、地上地下部光合产物分配比例、进入土壤的有机物组成和有机物矿化等的差异，① 揭示了水稻覆膜旱作土壤碳氮转化规律和稳定性，为水稻覆膜旱作节水减排和可持续发展提供理论依据。②与原有试验假设推测的结果相反，基于区域尺度农户田块大样本试验结果首次表明，由常规淹水栽培转变为覆膜栽培5-20年之后，1 m深度土层土壤有机碳氮含量与储量显著提高。③ 与常规淹水体系相比，不同海拔高度引起的气温变化和覆膜旱作引起的土温变化差异，导致初级生产力、地上地下部光合产物分配比例、进入土壤的有机物组成和有机物矿化等的差异，高海拔覆膜旱作增产效果比低海拔显著。④ 水稻覆膜旱作显著提高了灌溉水水分利用效率500%，显著提高了氮肥利用效率。⑤ 显著降低了温室气体N2O排放量，但增加了CH4排放量，总体致温效应显著降低。⑥ 在土壤有机质含量高的东北寒地稻作区，该栽培体系具有巨大的推广应用前景。. 本项目研究工作， 在国外权威学术期刊（一、二区）发表论文SCI论文12篇，其中第一标注6篇、第二标注4篇；培养博士生研究生4名、硕士研究生4名； 参加项目的4位博士生均赴德国哥廷根大学或德国大气环境研究所，开展了为期6-18个月的学术交流。