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土地利用变化对焉耆盆地土壤有机碳和土壤无机碳的影响
王家平
学位类型博士
导师王秀君 ; 赵成义
2015
学位授予单位中国科学院大学
学位授予地点北京
学位专业生态学
关键词土壤有机碳 土壤无机碳 稳定性碳同位素 土壤co2浓度 地表co2通量 土壤无机碳累积速率 土地利用变化
摘要土壤有机碳库和土壤无机碳库是陆地生态系统中重要的两个碳库,当前对干旱区两个碳库的评估匮乏。因此我们在新疆中部焉耆盆地对土壤有机碳和土壤无机碳动态变化进行研究。通过对荒漠、灌丛和农田植被下21个土壤剖面土壤有机碳、土壤无机碳及其同位素研究分析,明确不同土地利用方式对土壤有机碳、无机碳储量的影响;并以焉耆盆地农田土壤为研究对象,进行野外观测实验,设置两个裸地处理(其中一个添加钙源)和一个种植玉米的处理,定期同步观测土壤剖面中CO2浓度和地表CO2通量等数据,获得玉米生育期的季节变化规律。主要研究结果包括: (1)烧失法能够准确测定干旱区土壤有机碳和无机碳的含量:通过对用烧失法和传统分析方法所测的土壤有机碳和无机碳进行比较,发现二者具有显著的相关关系(r > 0.94, P < 0.001);通过一组土样所得数据建立土壤有机碳、土壤无机碳烧失法与传统方法回归方程,然后用另一组土样进行检验发现烧失法能够准确测定干旱区土壤有机碳和土壤无机碳。 (2)增加钙源能够降低响农田土壤CO2的排放:玉米生育期内,三种处理下土壤CO2浓度都随着土壤深度增加而增大;CO2浓度在整个生育期内大小顺序为: 添加钙源 < 裸地 < 玉米。土壤地表CO2通量日变化特征明显,早晨5:00-7:00较低,在午后12:00-14:00达到最大。三种处理月最小值都出现在十月,最大值玉米处理在六月,裸地和添加钙源处理在七月。玉米整个生育期内,以玉米处理土壤地表CO2通量最高 (688 g C m-2),添加钙源处理最小 (241 g C m-2),裸地处理居中 (273 g C m-2)。 (3)土地利用变化(即荒漠、灌丛植被转变为农田)能够提高土壤有机碳和无机碳的储量:土壤有机碳随着土壤深度增加为减少,除了荒漠,灌丛和农田植被土壤无机碳含量随着土壤深度增加而增大。在0-30 cm土壤中,土壤有机碳密度和土壤无机碳密度在荒漠植被下土壤中含量分别为1.0 ±0.3 和 4.0 ±0.8 kg C m-2,在农田中最大,分别为4.6 ±0.6 和 11.0 ±2.0 kg C m-2。焉耆盆地荒漠、灌丛和农田植被土壤总碳密度在0-100 cm分别为11.6 ±4.8, 45.1±10.4 和 51.2±5.6 kg C m-2,表明干旱区灌丛转变为农田后,不仅能增加土壤有机碳,而且也增加了无机碳。不同土地利用条件下土壤有机碳稳定性碳同位素没有明显差异,而土壤无机碳稳定性碳同位素差异显著,在荒漠、灌丛和农田植被土壤中分别为-0.6‰、-2.2‰ 和-3.4‰,表明农田土壤中次生碳酸盐含量高于荒漠土壤和灌丛土壤。 (4)干旱区农田土壤中无机碳的累积主要以次生碳酸盐为主:1m土层土壤无机碳的累积在荒漠、灌丛和农田植被土壤分别为9.7、36.8和42.0 kg C m-2。平均来说,土壤次生碳酸盐在荒漠、灌丛和农田植被土壤分别占土壤无机碳的18.3、32.5和44.5%。分析发现,焉耆盆地农田土壤有机碳、土壤无机碳和土壤次生碳酸盐累积速率分别为23.3、85.0和113.3 g C m-2 yr-1。 通过以上研究结果,可以得出以下结论:干旱区土地利用变化(即灌丛开垦为农田),不仅能提高土壤肥力(即增加土壤有机碳),而且能更多的增加土壤无机碳;干旱区农田土壤次生碳酸盐的累积速率超过土壤有机碳的累积速率,以往研究中可能低估了干旱区土壤无机碳累积速率。由此可见,探明干旱区土壤有机碳、土壤无机碳的累积转化过程及地表释放量,将丰富干旱区碳循环过程的认识,为揭示“碳失汇”提供科学依据。
其他摘要Soil organic carbon (SOC) and inorganic carbon (SIC) are important reservoirs of carbon in the terrestrial ecosystems. Assessments of both SOC and SIC are lacking in arid regions. We carried out a study in the Yanqi Basin, located in central Xinjiang, to evaluate the dynamics of SOC and SIC. Twenty one soil profiles were sampled from three types of land: desert, shrub, and agricultural soils. We determined SOC and SIC, and the stable carbon isotopic compositions (δ13C). In order to investigate the effects of calcium source and cropping on soil CO2 concentration and CO2 efflux, field measurements were also conducted in the cropland of Yanqi basin during the maize growing season. The main parts of this study are as follows: (1) Evaluation of Loss-on-ignition (LOI) methods: There were strong linear relationships (r > 0.94, P < 0.001) between the traditional method and the LOI technique for both SOC and SIC measurements. We used one set of soil samples to develop relationships between LOI and SOC (by the Walkley-Black method), and between LOI and SIC (by the pressure calcimeter method). Then the other set of soil samples was used to evaluate the derived equations. By comparing predicted SOC and SIC with measured values, we found that the mean absolute errors were small for both SOC (1.7 g C kg-1) and SIC (1.22 g C kg-1). Our study demonstrated the capacity of the LOI methods for accurate estimates of SOC and SIC in arid soils (2) Effects of calcium source and cropping on soil CO2 and CO2 efflux: Soil CO2 concentrations showed an increase with depth during the maize growing season, which followed an order: bare ground with Ca addition (BG+Ca) < bare ground (BG) < maize field (MF). There was a significant diurnal variation in CO2 efflux, with the lowest and highest values appeared at 5:00-7:00 and 12:00-14:00, respectively. As for the seasonal variation, the lowest CO2 efflux appeared in October whereas the highest was in June under the MF treatment and in July under the BG and BG+Ca treatments. During the growing season, CO2 efflux was 273, 241 and 688 g C m-2 for the BG, BG+Ca and MF treatments, respectively. (3) Impacts of land use change on SOC and SIC: Our data showed SOC decreased with depth in all soil profiles, however, SIC increased with depth in all soil profiles except in the desert soils. Both SOC and SIC stocks (over the 0–30-cm depth) were lowest in the desert soils (1.0±0.3 and 4.0±0.8 kg C m-2 for SOC and SIC, respectively), but greatest in the agricultural soils (4.6 ±0.6 and 11.0 ±2.0 kg C m-2 for SOC and SIC, respectively). Total soil carbon stocks in the 0–100 cm were 11.6 ±4.8, 45.1±10.4 and 51.2±5.6 kg C m-2 in the desert soils, shrub soils and agricultural soils, respectively. On average, SIC accounted for more than 80% of the total carbon in this region. There were no significant differences in δ13C of SOC among land use types. In contrast, the δ13C of SIC was different: desert soils (-0.6‰) > shrub soils (-2.2‰) > agricultural soils (-3.4‰). The depletion of 13C in SIC of the agricultural soils indicates enhancement of pedogenic carbonate (PIC) by cropping. Our study suggested that converting shrub land to agricultural land in arid regions may lead to an increase not only in SOC stock, but also in SIC stock. (4) Accumulation rate of soil carbonate: In the Yanqi Basin, SIC stock was 9.7, 36.8 and 42.0 kg C m-2 in desert soil, shrub soil and agricultural soil, respectively. On average, PIC was 18.3%, 32.5% and 44.5% of SIC for desert soil, shrub soil and agricultural soil, respectively. The accumulation rate of SIC in the agricultural soil was 23.3, 85.0 and 113.3 g C m-2 yr-1 for SOC, SIC and PIC, respectively. In summary, converting shrub land to agricultural land in arid regions may lead to an increase not only in SOC stock, but also in SIC stock. The accumulation rate of PIC exceeds that of SOC in the agricultural soil. These analyses suggest that SIC accumulation rate may be underestimated previously. Further studies are needed to investigate the fluxes and transformations of various carbon forms in arid regions.
学科领域生态学
语种中文
文献类型学位论文
条目标识符http://ir.xjlas.org/handle/365004/14613
专题研究系统_荒漠环境研究室
作者单位中科院新疆生态与地理研究所
推荐引用方式
GB/T 7714
王家平. 土地利用变化对焉耆盆地土壤有机碳和土壤无机碳的影响[D]. 北京. 中国科学院大学,2015.
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