Carbon sequestration in salt affected and alkaline soils under cotton in Tarim oasis (China)

该项目的主要目标是阐明导致CO2流入土壤的过程。在新疆绿洲棉田，这种现象已被报道，特别是在夜间。我们假设物理化学过程（e。G.与生物过程（例如，土壤微生物或植物根系中的掺入）相比，土壤中的CO2通量（例如，土壤中的微生物或植物根系的掺入）更高。为了探索导致CO2通量进入土壤的过程，将研究CO2在土壤中的产生和运输以及在土壤水中的溶解增加和成土CaCO 3的重结晶。CO2通量的分析将在有棉花和没有棉花的地块上进行。为了全面评估土壤CO2的产生和传输，并验证Fick第一定律描述的土壤表面CO2排放，将通过气室和涡度相关方法连续测量土壤表面CO2排放。此外，将使用一个小型固态CO2传感器连续测量0厘米、5厘米、15厘米、20厘米、30厘米、50厘米、80厘米和100厘米深度的土壤CO2浓度。同时测定影响土壤CO_2产生和运移的其他土壤物理特性和生物因子，实验室用~（14）CO_2和田间用~（13）CO_2进行同位素标记，将有助于了解土壤CO_2固定的机理。在特定的环境条件（温度、湿度、昼夜）下，将14 CO2应用于有植物和无植物的微观世界，将使我们能够在土壤水、土壤空气、植物、成土碳酸盐、微生物和土壤上方的空气中追踪14 C。考虑到已阐明的CO2进出土壤的机制，将进行13 CO2的田间试验。测量的CO2浓度和同位素组成的所有隔间将使我们能够创建一个模型，阐明土壤中的CO2固定的现象。关键词：土壤CO2生产，土壤CO2运移，绿洲棉田，碳平衡，成土碳酸盐

The main objective of the project is the elucidation of the process that leads to CO2 flux into the soils. This phenomenon has been reported on oasis cotton fields in Xinjing, China especially at night. We assume that physicochemical processes (e. g. recrystallyzation as pedogenic carbon, higher solution in cool soil water) than biological processes (e.g. incorporation in soil microorganisms or plant roots are responsible for this CO2 flux into soil. To explore the process causing CO2 flux into soil, CO2 production and transport in soil as well as increased dissolution in the soil water and recrystallization of pedogenic CaCO3 will be investigated. Analysis of CO2 fluxes will be conducted in the field on plots with and without cotton plants. For complete assessment of soil CO2 production and transport and to testify the soil surface CO2 efflux described by Fick’s fist law, soil surface CO2 efflux will be measured continuously both by chamber and by eddy covariance methods. Additionally, a small solid-state CO2 sensor will be used to measure continuously soil CO2 concentrations at depths of 0 cm, 5 , 15 , 20 , 30 , 50 , 80 and 100 cm. Other soil physical characteristics and biotic factors influencing soil CO2 production and transport will be measured simultaneously.Isotopic labeling with 14CO2 in the laboratory and with 13CO2 in the field will help to understand mechanisms of CO2 fixation. Application of 14CO2 under defined environmental conditions (temperature, moisture, day/night) to microcosms with and without plants will enable us to trace 14C in soil water, soil air, plants, pedogenic carbonates, microorganisms and the air above the soil. Considering the elucidated mechanisms of CO2 flux into and out of the soil, field experiments with 13CO2 will be conducted. Measurements of CO2 concentrations and isotopic composition in all compartments will enable us create a model which elucidates the phenomenon of CO2 fixation in soils. Keywords: Soil CO2 production, Soil CO2 transport, Oasis cotton field, carbon balance, pedogenic carbonates