黄土区耕地面积占全国耕地面积的15%以上,该区域降水资源贫乏,是我国土壤生产力和土壤有机碳储量最低的区域之一。营养的大量投入可以极大地提高土壤生产力,但对于营养添加下土壤CO_2排放有何变化以及是如何改变黄土区土壤环境,进而影响土壤呼吸及温度敏感性还尚不清楚。本文以长武实验田的黑垆土作为研究对象,分别对N12(施氮量120 kg · hm~(-2))土样设置不添加、添加磷源以及CK(长期连作不施肥)土样设置不添加、添加磷源、碳源、碳磷源(共计6个处理),比较分析在15℃和25℃培养下土壤呼吸速率的变化,以及培养周期内土壤温度敏感性Q_(10)(即温度每升高10℃,温室气体排放速率变化的倍数)的变化趋势。通过对呼吸前后土壤pH值、全碳全磷、有机碳、速效磷、硝态氮、铵态氮以及微生物生物量碳磷(MBC、MBP)的测定,分析其影响因素。碳磷添加在一定程度上提高了土壤的呼吸速率,其中碳源的添加明显增强了土壤呼吸速率以及土壤Q_(10)值。碳磷添加大幅度提高了土壤全碳、速效磷含量以及微生物活性,15℃条件培养后,土壤微生物生物量最高。碳磷添加后,土壤呼吸速率与土壤pH、全碳、铵态氮、MBC呈极显著相关关系。该研究为黄土区土壤生产力的提高以及降低温室气体的排放、恢复和改善生态环境提供理论依据。
英文摘要:
Background, aim, and scope The cultivated land area in the loess area accounts for more than 15% of the total cultivated land area in China. The rainfall resources in this area are poor, soil erosion and desertification are serious, and productivity is low. Agricultural operation and management in dry land is relatively backward; it is one of the lowest areas of productivity and soil organic carbon storage in China. In recent years, there are many researches on loess area. Studies have found that a large amount of nutrition can greatly increase soil productivity. However, it is not clear about the change in CO_2 emissions after nutrition is added, and how nutrient additions change the soil environment in loess area, and then affect soil respiration and temperature sensitivity. Materials and methods In this paper, the N12 soil samples are divided into two treatments: black and phosphorus addition, and CK soil samples are divided into four treatments: black, phosphorus addition, carbon addition, and carbon and phosphorus addition (6 treatments in total), soil basic respiration rate at 15℃ and 25℃ is compared and analyzed as well as the change trend of Q_(10) during the period of culture. Influencing factors are analyzed by comparing the changes of soil pH, total carbon and total phosphorus, organic carbon, available phosphorus, nitrate nitrogen and microbial biomass carbon and phosphorus (MBC and MBP) around respiration. Results Carbon and phosphorus increase the respiration rate of soil to a certain extent, the addition of carbon source significantly enhance soil respiration rate and Q_(10). The addition of carbon and phosphorus has increase effect on the total carbon, available phosphorus content and microbial activity, the soil microbial biomass is the highest after 15℃. After the addition of carbon and phosphorus, the soil respiration rate has a very significant correlation with soil pH, total carbon, ammonium nitrogen content and MBC. Discussion Soil respiration is an important biological indicator of soil quality and fertility, in particular, the basic soil respiration partly reacts the biological activity of the soil and the strength of soil material metabolism, which reflects the transformation and supply of soil nutrients. The addition of nutrients changes the soil environment and fertility, and then increases the respiration rate and Q_(10). Carbon content in soil is a quick-acting substrate for microbial growth, so the addition of carbon promotes the activity and growth of microbes and then increases the respiration. In addition, soil pH also affects soil carbon, nitrogen and other nutrients then influences CO_2 emissions. Conclusions To sum up, the addition of carbon and phosphorus changes soil environment, such as soil pH, total carbon, ammonium nitrogen and MBC, which changes soil respiration rate and Q_(10). Recommendations and perspectives The sensitivity of soil respiration rate to temperature change directly affects the estimation of carbon cycling and carbon accumulation, and predicts the carbon balance and global warming degree of the terrestrial ecosystem in the future. Therefore, the study provides a theoretical basis for the improvement of soil productivity and the reduction of greenhouse gas emissions, recovery and improvement of the ecological environment in the loess region.