快速城市化对北京城市表层土壤碳库的影响研究
文献类型：学位论文
| 作者 | 罗上华 |
| 学位类别 | 博士 |
| 答辩日期 | 2014-05 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 北京 |
| 导师 | 马克明 ; 邬建国 |
| 关键词 | 城市土壤 土壤有机碳 土壤呼吸 城市化 北京市 urban soils soil organic carbon soil respiration urbanization Beijing city |
| 其他题名 | Impact of rapid urbanization on urban topsoil carbon stocks in Beijing, China |
| 学位专业 | 生态学 |
| 中文摘要 | 目前全球已有超过50%的人口生活在城市中，过去30 年及未来较长的一段时期内，城市用地的扩张速度远高于城市人口的增长。城市化使越来越多的自然用地和农业用地转变为城市，深刻地改变着生态系统的结构和功能，在城市、区域乃至全球尺度上对生态系统造成重大影响。土壤碳循环是全球变化研究中最受关注的领域之一，有关城市土壤碳循环的研究日益受到关注，但是相对于其他陆生生态系统，这种由人类活动主导的剧烈环境变化所驱动的土壤环境演化及其生态系统响应仍是一个尚未系统回答的科学问题。随着城市用地的持续扩张，特别是处于城市化高速发展的发展中国家，迫切需要深入认识这种转化对于区域乃至全球变化的影响。 近30年来，中国是世界上城市人口和城市用地增长最快的国家。作为中国北方城市化程度最高的城市，自20世纪80年代以来，北京市的人口城市化率和城市用地规模均呈快速扩张态势。伴随着快速城市化中土地利用/覆盖的剧烈变化，对当地和区域的土壤环境产生显著影响。然而，城市化对当地土壤碳库和碳通量等方面的研究仍处于起步阶段，尤其缺乏对城市土壤碳库和碳通量方面的研究。因此，本研究选择北京市中心城区与近郊区（六环路范围及周边）的典型绿地土壤为研究对象，开展了城市土壤碳库特征及其影响因素、城市土壤碳通量特征、城市土壤碳固持潜力、以及土地利用变化对土壤碳储量的潜在影响方面的研究，这对于增进了解快速 城市化过程对土壤碳库、碳通量以及土壤碳固持潜力等方面的影响及其调控，具有一定的理论意义和现实意义。 本研究主要包括五个方面的研究内容，即（1）北京城市表层土壤碳储量分布特征研究；（2）城市化对土壤碳库的影响研究；（3）典型城市绿地土壤碳固持效应研究；（4）典型城市绿地土壤通量特征研究；（5）城市土地利用变化对土壤碳库的影响研究。主要研究结论如下： （1）北京城市表层土壤碳组分呈现较高的时空异质性特征。不同类型城市绿地土壤有机碳、无机碳和全碳含量差异显著，行道树土壤有机碳、无机碳和全碳均显著高于其他类型绿地，而其它类型间土壤中有机碳和全碳含量差异不显著；居住绿地、道路绿地、单位绿地和公园绿地中土壤无机碳含量显著高于生产绿地、防护绿地。在本研究的空间和尺度上，土壤中碳组分呈现较强的空间自相关性，土壤中碳含量的空间格局总体呈现西北高、东南低的特点；城区略高于郊区的特点。 （2）北京中心城区的绿地表层土壤碳含量显著高于郊区绿地，城区单位绿地、居住绿地、道路绿地土壤有机碳密度均显著高于郊区同类型绿地，公园绿地和行道树土壤有机碳城郊差异不显著；城区各类绿地表层土壤无机碳和全碳密度均显著高于郊区同类绿地，位于郊区的防护绿地、生产绿地土壤无机碳含量显著低于城区和郊区其他类型绿地。与郊区农业用地相比，城市绿地土壤中的有机碳、无机碳和全碳含量均有增加，说明城市化在一定程度上增加了北京市城区土壤有机碳和无机碳的储量。 （3）影响北京城市表层土壤碳储量及空间分布的主要因素是土壤理化性质、环境因素和人为影响，成土土壤的理化性质包括土壤氮含量、pH 值和容重；环境因素包括距城市中心的距离、绿地类型、城郊差异；较好的管护水平以及乔灌草复合配置绿地可能有利于碳的累积。 （4）北京市典型绿地土壤中碳累积研究结果显示，土壤中有机碳、无机碳和全碳含量与绿地建成时间具有显著的正相关关系。居住区绿地的土壤有机碳、无机碳和全碳均随建成时间增长呈线性增加趋势，碳固持的速率分别约为46 gC·m-2·a-1，19g C·m-2·a-1 和65 g C·m-2·a-1。而公园绿地土壤碳累积量较低，景观改造等人为扰动对表层土壤碳累积具有较大影响。这些结果综合表明，北京城市土壤具有一定的碳固持潜力。 （5）北京典型城市草坪的土壤呼吸的季节动态呈单峰型变化，冬季和春初较低，至夏季达到最高值(６月－８月份)后逐渐减小，最大值出现在７月份；城市草坪的全年土壤呼吸速率的变化范围在0.09－13.19 g C·m-2·d-1 之间，土壤呼吸的年碳通量在796.18－1555.72 gC·m-2·a-1 之间，均值为1124.3 gC·m-2·a-1。城郊差异、热岛效应、土壤温度、绿地建成时间和管护水平等都对城市草坪土壤呼吸有一定影响，其中土壤温度对城市草坪土壤呼吸的解释程度达到69.4%。各草坪样地的土壤呼吸温度敏感性Q10 在1.92－3.25 之间。全市草坪土壤呼吸的年碳通量达到113346.53 t C·a-1，但城市绿地是碳源还是碳汇具有很大的不确定性。 （6）在1984 年－2010 年期间，北京主城区范围内除农业用地大幅减少外，人工表面、林地、草地、湿地和其他用地均呈增加趋势，城镇用地蔓延趋势十分明显，其中1990 年代扩张最为剧烈。建成区用地扩展主要来自农业用地和原来的建设用地，对于林地、草地、湿地等自然用地占用比例并不高；而城市郊区的建设用地主要来自于农业用地。 （7）在1984－2010 年期间，伴随着北京快速城市化过程的土地利用变化，研究区范围内的表层土壤有机碳的总储量增加了0.507Mt。本研究初步表明，在华北平原这类农业土壤有机碳背景值较低的地区，城市化带来的土地利用变化增加了区域土壤有机碳储量。 |
| 英文摘要 | Although urban settlements cover less than 1% of the earth’s surface, more than 50% of the world’s population lives in cities and towns. As urbanization continues, the trend of the spread of urban land becomes more obvious. Urban land coverage around the world is expanding, on average, twice as fast as their populations. The rapid and massive urbanization has resulted in widespread ecological and environmental consequences from local to regional and national scales. To alleviate the negative impacts of urbanization and make our cities more sustainable, it is important to understand how urbanization affects biogeochemical cycles, particularly carbon dynamics. Soil carbon stock, including SOC and SIC stock, is the largest carbon pool in the terrestrial ecosystem. So far, however, understanding of urban soil biogeochemistry is rather limited, and more research is urgently needed. The majority of urban soil carbon research projects have focused on a limited number of samples in the developed nations. The study of urban soil carbon stocks in developing regions, where urban expansions take place on prime agricultural land and at a higher speed, is somewhat sparse.Beijing is a historical city located on the northern tip of the roughly triangular North China Plain. The city has been undergoing rapid and sprawling urbanization in the past three decades, where urban land cover and population have increased markedly through these decades. To assess the effect of urban land-use change on the soil carbon stocks, we compared soil organic carbon (SOC), soil inorganic carbon (SIC), and soil total carbon (TC) between different land-use types in the Beijing metropolitan areas(the BMA). The study is important to increase our understanding of impacts of rapid urbanization on local soil carbon pool. For this thesis, five approaches were used to investigate the impacts of urbanization on soil carbon pool: 1) a field sampling of 490 topsoil samples by a dual gradient, spatially stratified sampling design with 128 survey sites in the BMA; 2) a univariate and multivariate factor analysis of anthropogenic drivers and environmental drivers in the control of urban soil carbon storage; 3) a chronosequence study of typical residual and park soil carbon densities to assess urban soil carbon sequestration ability; 4) an observational study of soil respiration in 16 typical turfgrass fields along urban-suburbs gradient; 5) a city-scale landscape study in which the effects of land use and land cover(LUCC) coupled with rapid urbanization on local soil carbon pool were tested. The main results and conclusions showed as following: (1) We analyzed concentration and density of soil organic carbon (SOC), inorganic carbon (SIC), total carbon(TC), in order to explore the characteristics of the spatial distribution of carbon in the urban topsoils. The results showed that the soil carbon content showing a high spatial and temporal heterogeneity in the BMA, and urban soils had higher SOC and SIC contents than suburban soils. The roadside tree pit soils had significantly higher SOC, SIC and TC density than other land-use type, and differences in SOC content among other types were not significant. SIC densities of residential, institutional, parks and transportation soil were significantly higher than those of suburban forests, nurseries, and orchards. In the scope and scale of this study, soil carbon stocks showing high spatial autocorrelation characteristics, the spatial pattern of soil carbon content overall northwest to southeast, and urban soil carbon stock is slightly higher than that of the suburbs. (2) Comparing similar land cover types between urban and suburban sites,institutional and transportation had significant higher SOC than the same types in the suburban sites. Yet urban parks and roadside tree pits had slightly lower SOC than the similar types in the suburban area. Urban land cover types had higher SIC and TC than the same land cover types of the suburban sites. Significantly negative correlations existed among SOC, SIC and TC, as well as between these variables and distance from the urban core. Compared with the agricultural land in the suburbs, the soil carbon densities of urban soil were also increased. These results indicated that urbanization is conducive to local soil carbon stocks to some extent. (3) The topsoil carbon storage and spatial distribution of the main factors is the soil physical and chemical properties, environmental factors and anthropogenic factors. Soil physical and chemical properties included soil nitrogen content, pH and bulk density; environmental factors included distance from the city center, land-use types, soil parent material peri-urbanization; and management and vegetation complex configuration are conducive to the accumulation of urban soil carbon stocks. (4) Results from our chronosequence suggest that soils at typical urban green space have the potential to accumulate carbon rapidly after residential development. Rates of SOC, SIC and TC at residential area sites are 46 g C·m-2·a-1，19 g C·m-2·a-1, and 65 gC·m-2·a-1, respectively. Rates of SOC and TC at Park sites are 25 g C·m-2·a-1， and 23 g C·m-2·a-1, which showed disturbance may cause carbon accumulated carbon. These date suggested that soils in the BMA have a significant capacity to sequester carbon. (5) The annual soil respiration of 16 typical turfgrass ecosystem in the BMA showed a single peak dynamic changes in performance for lower in winter and early spring (December-March), being higher in the summer (June-August), and get to the maximum in July. The range of variation of soil respiration is 0.09－13.19 g C·m-2·d-1, and total annual respiration is 796.18－1555.72 gC·m-2·a-1(mean value 1124.3 gC·m-2·a-1). The soil respiration rate had significant exponential correlation with soil temperature. The Q10 value in the range of 1.92 to 3.25. The results showed influencing factors on soil respiration included soil temperature, built-up time, and management. But whether urban turfgrass ecosystem is green house gas sources or sinks need be further studied. (6) In the period 1984 -2010, the land area of agricultural land, artificial surfaces,woodlands, grasslands, wetlands and other sites in the BMA showed an increasing trend,which expanded most dramatically in the 1990s. The built-up area are mainly converted from agricultural land and the construction land, while woodland, grassland, wetlands and other natural land occupancy ratio is not high. But the building land in the suburbs in the BMA, were mainly from the agricultural land. (7) In the period 1984-2010, the local SOC stocks increased totaled 0.507Mt in the topsoils, due to land use change along with rapid urbanization process in the BMA. The study showed that, LUCC accompany with urbanization may be beneficial to regional soil organic carbon accumulation in the North China Plain, where has the lower SOC background value. |
| 公开日期 | 2015-06-12 |
| 源URL | [http://ir.rcees.ac.cn/handle/311016/13449]  |
| 专题 | 生态环境研究中心_城市与区域生态国家重点实验室 |
| 推荐引用方式 GB/T 7714 | 罗上华. 快速城市化对北京城市表层土壤碳库的影响研究[D]. 北京. 中国科学院研究生院. 2014. |
入库方式： OAI收割
来源：生态环境研究中心
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