Variation Of Soil Carbon Flux And Its Imapct Factors Under Typical Land Use Types In The Lower Reaches Of The Yellow River

Soil respiration is closely related to global climate change, and it can reflect the ability of soil nutrient transformation and supply to a certain extent, which has become a hot research topic at home and abroad. Therefore, the typical land use types in the lower reaches of the Yellow River were selected as the study area and we got different indicators from different sample plots from Mar, 2014 to May, 2015. The major indicators include soil carbon flux, soil temperature, near-surface atmospheric temperature, soil moisture and soil physicochemical properties. Based on this measurement, we analyzethe diurnal and lunar variations of soil carbon flux and their relationship with the influencing factors so as to provide some references about the mechanism of carbon flux carbon and carbon sequestration for the different land use types in the lower reaches of the Yellow River. The major results are as follows:?1? The monthly averaged value of soil carbon flux of north shore is 24% higher than the south. The soil carbon flux in March and April is close to that in September and October, and becomes slight higher from May to August and reaches the peak of the year in August; There is a decreasing trend in coming months and reaches the minimum in December. The highest value of soil carbon flux in different months of north shore in Fengqiu is 13.19 ?mol·m^-2·s^-1 in August and the lowest value is 0.39 ?mol·m^-2·s^-1 in December. The monthly averaged value is 5.28 ?mol·m^-2·s^-1 ranging from 1.20 ?mol·m^-2·s^-1 to 8.57 ?mol·m^-2·s^-1. Regarding the soil carbon flux of south shore in Kaifeng, the highest value is 10.97 ?mol·m^-2·s^-1 in July and the lowest value is only 0.20 ?mol·m^-2·s^-1 in December ranging from 0.87?mol·m^-2·s^-1 to 7.69?mol·m^-2·s^-1. The highest monthly average value is in August and the lowest is in December.?2? In the same month, the diurnal variation of soil carbon flux in the plots of different land use types is similar. The highest value is found between 10:00 am and 16:00 pm,and the variation tendency shows unimodal type, bimodal type and straight. In terms of different months, especially the months with lower temperature, the highest value of soil carbon flux is relative later, at about 14:00. The variation of soil carbon flux of north shore in Fengqiu is:wheat/corn > orchard > artificial forest > lonicera land; while the south shore in Kaifeng presents different result: orchard > wheat/corn> artificial forest > watermelon land.?3? The higher values of soil carbon flux appear in different period. For north shore of Fengqiu, the higher values are found in late spring and summer, while autumn and winter are relative lower. For south shore of Kaifeng, summer is the main season for higher value, and the lower values are in spring, autumn and winter. Relatively, the duration of high value for north shore of Fengqiu is longer.?4? This study analyzes the relationship between different environmental factors and soil carbon fluxes by means of regression equation. The results indicates that there is some correlation between soil temperature, soil moisture, and near-surface atmospheric temperature.The relationship between influencing factors and soil carbon fluxes in differet years in Fengqiu and Kaifeng is different.?5? It is widely accepted that soil texture, soil carbon and nitrogen have significant effect on soil carbon flux. Soil texture of north shore in Fengqiu is mainly composed of clayey loam,while south shore in Kaifeng is sandy soil. The soil texture with high clay content is conducive to the accumulation of organic carbon and nitrogen, which has positive effects on improving soil respiration. However, the soil texture with high sand content has weak conservation of fertilizer and produces opposite effects compared with clay. This is the reason why the soil carbon flux of north shore in Fengqiu is higher than that of south shore in Kaifeng. Therefore, increasing organic matter content in soil, returning straw to field and applying compound fertilizer can increase the soil total carbon, total nitrogen content, which will make a great contribution to improving soil activated carbon and organic nitrogen, hence soil respiration.