基于生态网络效用的城市碳代谢空间分析——以杭州为例

城市碳排放占全球碳排放总量的78%,通过模拟生物代谢来剖析城市碳代谢机理从而控制城市碳排放是缓解全球气候变暖危机的关键。为研究杭州城市化过程中土地利用变化对城市碳代谢的综合作用,以4个时间段(1995—2000,2000—2005,2005—2010,2010—2015)为例,建立了一个"碳流"模型来分析城市生态系统中自然和人工分室在城市碳代谢正负"碳流"产生中的作用,之后利用生态网络效用方法分析"碳流"产生的生态关系及其空间分布,同时利用互惠指数M综合评价土地利用变化对城市碳代谢的综合作用。结果显示(1)净"碳流"在研究期间持续呈现负值且在2000—2005年间达到峰值,负"碳流"主要源自耕地与工业用地之间的转换,正"碳流"主要源自工业用地与城市用地之间的转换。(2)1995—2000年互惠指数(M)呈现先增加后减少再增加的变化趋势,M平均值小于1,说明土地利用变化对城市碳代谢的综合作用是消极的。(3)竞争关系集聚在高负碳代谢密度分室,互惠共生关系主要集聚在高正碳代谢密度分室。(4)从1995—2000至2010—2015,以每5年为时间间隔,生态关系分布空间变化如下:掠夺限制生态关系呈现向西北、西南和南部方向蔓延—西北方向移动—东南方向移动的变化趋势,竞争生态关系呈现东南方向移动—南部和西北部方向蔓延—零星分布的变化趋势,互惠共生生态关系呈现向东南方向移动—暂时不存在—零星分布的变化趋势。研究结果为低碳城市发展提供了理论依据。     

土地利用/覆盖变化对陆地生态系统碳循环的影响

土地利用/覆盖变化是学术界最为关注的环境变化问题之一,它能够影响陆地生态系统的生物多样性、水、碳和养分循环、能量平衡,引起温室气体释放增加等其它环境问题。不同类型的土地利用/覆盖变化对生态系统碳循环的作用不同,由高生物量的森林转化为低生物量的草地、农田或城市后,大量的CO₂将释放到大气中。全球土地利用/覆盖变化具有很强的空间变异性,对生态系统碳循环的影响同样具有明显的空间差异:热带地区的土地利用/覆盖变化造成大量的碳释放,而中高纬度地区土地利用/覆盖变化则表现为碳汇。目前,土地利用/覆盖变化引起的生态系统碳循环变化主要是通过模型模拟来估算的。尽管土地利用/覆盖变化及其相关过程与生态系统碳循环的关系已经比较清楚,但是,由于土地利用/覆盖变化过程复杂且影响广泛,对于如何量化两者之间的关系还存在很多不确定性。目前的量化过程主要是利用经验数据来实现的,机理性不强,使得对土地利用/覆盖变化造成的陆地生态系统CO₂释放量的估测差异很大。除了进一步加强长期定位研究以获得土地利用/覆盖变化与生态系统碳循环过程的定量关系外,土地利用/覆盖变化模型与植被动态模型、生态系统过程模型的耦合也是今后模型发展的主要方向之一。采用合理的管理措施能够大量增加土地利用/覆盖变化过程中的碳储存量,降低碳释放量,因此在模型中耦合管理措施来研究土地利用/覆盖变化过程对生态系统碳循环的影响是未来几年的工作重点。     

城市生态网络分析研究进展

自生态网络分析方法提出40多年来,其理论发展和应用实践不断拓展,但直至21世纪才不断引入到城市生态系统研究中,用以分析城市内部多个主体和多种生态流构成的关联网络。目前,城市生态网络分析集中于生态网络分析方法与指标的拓展及多尺度的应用研究,而生态网络分析方法又形成了上升性分析和环境元分析两大分支,多尺度应用涵盖了城市镶嵌的区域背景尺度和城市内部产业部门之间的细节尺度。然而,当前研究仍存在着多尺度融合、多种生态网络分析方法集成不足等问题,这限制了城市生态网络分析方法在城市规划设计中的应用。未来城市生态网络分析研究集中于如下3点:(1)开展多尺度城市生态网络分析,包括城市群-城市-园区/社区等,构建多级嵌套生态网络模型;(2)集成上升性与环境元分析方法,提出由外在表征到内在过程的城市生态系统评价模式及模拟方法;(3)强调自然节点在城市生态网络中的重要作用,形成社会经济节点与自然节点并重的生态网络模型,并强调构建多精度的生态网络模型服务于不同的研究目的。     

基于FLUS与InVEST模型的北京市生态系统碳储量时空演变与预测

城市地区虽然只占世界陆地面积的2%,却产生了全球约75%的碳排放,而科学合理的土地利用和管理方式可以重新固定大约60%-70%已耗损的碳。因此基于土地利用类型核算碳储量并探究城市土地利用变化其对碳储量的影响,能够揭示碳储量时空变化规律,为双碳目标下国土空间规划提供科学依据。基于1990-2018年北京市土地利用数据,利用InVEST模型测算1990-2018年北京市碳储量变化,再利用FLUS模型,分别测算自然演变情景、人口疏解城市发展情景、绿色集约生态保护情景3个城市发展情景下的土地利用变化,接着采用InVEST模型预测2035年3种情景下的碳储量变化,最后借助空间自相关模型对其进行分区管理研究,并基于此提出北京市未来城市发展与低碳城市建设规划建议。基于研究得出以下结果：（1）2000-2010年是碳流失较严重时期,碳储量下降了4.3%,而2010年后碳流失相对缓和,且在2015年后得到明显改善,2010年至2018年碳储量提升了3.5%。（2）除自然演变情景外,两种情景下的未来碳储量预测值均会进一步增加,且绿色集约生态保护情景的碳储量预测值最高,为16.39×10⁶ t,比最低的自然演变情景高出7.5×10⁵ t。（3）局部空间自相关分析结果显示,3种情景下的碳储量值在空间分布上具有相似性,碳储量高值区域在城市北部、西北部及西部区域出现集聚,低值区域则在中心城区聚集。     

京津唐城市群土地利用变化的区域增温效应模拟

土地利用变化与大气相互作用,影响区域气候,而城市及其周边地区受人类活动影响很大,成为土地利用变化最为强烈的区域。利用耦合了城市冠层模型的中尺度大气模式(WRF/UCM),在2008年的初始大气条件和边界条件下,用20世纪70年代后期和2008年两期京津唐地区土地利用资料替换WRF/UCM模式推荐的地表覆盖数据,模拟分析不同土地利用类型及其变化对应的气候差异情况。在此过程中,利用插值方法(ANUSPLIN)得到京津唐及其周边26个气象站点观测气温的插值数据,并以此在时空尺度上对比验证了模式的模拟结果。结果表明:WRF/UCM较好地模拟出了近地表2 m的气温,无论在空间上还是在时间上都表现良好;由城市扩展主导的土地利用变化导致研究区大部分区域的增温幅度大于0.05℃,且最大的增温区域出现在城市扩展区,可达1.31℃。此外本研究初步探讨了土地利用变化的增温贡献率,结果显示研究区土地利用变化导致增温0.08℃,整体贡献率为9.88%,城市扩展区增温0.29℃,表示出了城市扩展导致的增温贡献率达到32.75%。     

基于Markov和CLUE-S模型的敦煌市土地利用/覆盖格局情景模拟

建立Markov过程模型和CLUE-S模型的集成模型,选取海拔、坡度、到河流距离、到道路距离等13个驱动因子,基于敦煌市1996年的土地利用/覆盖变化(LUCC)数据,对2007年的土地利用/覆盖格局进行模拟,模拟效果较好。设置4种情景对敦煌市2018年土地利用/覆盖格局进行预测,揭示不同情景下的土地利用格局变化。情景模拟结果表明:不论是自然发展型情景还是单纯考虑生态保护和经济发展的情景,都仅是单一需求的考虑,不能实现区域又快又好的发展,是不可持续的发展模式。综合发展型情景弥补了上述情景的缺点,比较全面地考虑了生态环境恢复、经济发展等的需要,是一种比较理想的发展模式。     

土地利用/覆盖变化动力学国际会议将在北京召开

由北京师范大学、国家自然科学基金委员会主办 ,北京师范大学资源科学研究所、北京师范大学环境演变与自然灾害教育部重点实验室承办的土地利用 /覆盖变化动力学国际会议 (ＬＵＣＣＤ’2 0 0 1)将于 2 0 0 1年 8月 2 6～ 30日在中国北京市召开 .(ＬＵＣＣＤ’2 0 0 1)大会的目的是展现土地利用 /覆盖变化研究及近期在理论与应用上的发展 .大会议题 :1)土地利用 /覆盖变化检测理论与方法 2 )土地利用 /覆盖时空演变规律3)土地利用 /覆盖变化的驱动力模型 4 )土地利用 /覆盖变化预测与模拟技术5)物候、生物化学过程与土地利用 /覆盖变化 6)区…     

土地利用/覆盖变化动力学国际会议(LUCCD’2001)将在我国召开

由北京师范大学、国家自然科学基金委员会主办 ,北京师范大学资源科学研究所、北京师范大学环境演变与自然灾害教育部重点实验室承办的“土地利用 /覆盖变化动力学国际会议 (L UCCD’2 0 0 1)”将于 2 0 0 1年 8月 2 6～ 30日在我国北京市召开。大会 (L U CCD’2 0 0 1)的目的是为了展现土地利用 /覆盖变化研究 ,近期在理论与应用上的发展。大会议题 :1)土地利用 /覆盖变化检测理论与方法 ;2 )土地利用 /覆盖时空演变规律 ;3)土地利用 /覆盖变化的驱动力模型 ;4)土地利用 /覆盖变化预测与模拟技术 ;5 )物候、生物化学过程与土地利用 /…     

基于Google Earth Engine平台与复杂网络的黄河流域土地利用/覆被变化分析

黄河流域在中国社会经济发展和生态安全方面的地位十分重要,过去几十年的自然演变和人类活动对其造成了深远影响,系统科学地认识黄河流域的环境格局变化是实现黄河流域高质量发展的重要前提。基于Google Earth Engine平台和复杂网络分析方法,解译并分析了1986年至2018年黄河流域的连续年度土地利用/覆被变化(LUCC)。基于1000个独立验证点进行的评估显示解译的覆盖黄河流域33年的年度土地利用/覆被数据集的7个一级类的总体准确率为82.6%,15个二级类的总体准确率为74.7%。分析结果显示黄河流域的土地系统在整个研究期间呈现出复杂的时空变化,主要的LUCC模式包括：不变或很小的变化、伴随耕地流失的城市扩张、草地恢复、果园和梯田扩张和森林增加。基于复杂网络方法对黄河流域土地系统的分析表明,土地利用/覆被转移网络中的高覆盖草地、低植被覆盖地表和落叶常绿混交林与其他地类的转移较频繁,地类节点的中介中心性和度值较高,是黄河流域土地系统中的关键地类。另外与人类活动关系密切的果园和梯田、谷物耕地和城市及建设用地节点组成了较为活跃的网络社区结构,它们都有较高的结构多样性、接近中心性,这些地...     

光滑球拟酵母生产2,3-丁二酮的系统代谢工程策略

【目的】调控丙酮酸工业生产菌株光滑球拟酵母(Torulopsis glabrata)CCTCC M202019碳代谢流分布促进2,3-丁二酮积累。【方法】过量表达来源于枯草芽孢杆菌(Bacillus subtilis)的乙酰乳酸合成酶(ALS);在此基础上,借助T.glabrata全基因组规模代谢网络模型(GSMM)iNX804解析敲除基因ILV5的必要性;敲除基因BDH以阻断2,3-丁二酮的降解。【结果】过量表达ALS将ALS活性提高了4.6倍,发酵液中2,3-丁二酮浓度从0.01 g/L提高至0.57 g/L。敲除基因ILV5使2,3-丁二酮浓度提高28.1%。敲除基因BDH导致丁二酮还原酶和丁二醇脱氢酶活性分别降低74.4%、76.1%,同时2,3-丁二酮进一步代谢产物3-羟基丁酮和2,3-丁二醇浓度则分别降低52.2%和71.4%,2,3-丁二酮浓度为0.95 g/L。【结论】基于GSMM的系统代谢工程策略能够将碳代谢流从丙酮酸节点导向2,3-丁二酮,实现2,3-丁二酮的有效积累。     

Gross changes in reconstructions of historic land cover/use for Europe between 1900 and 2010

Historic land‐cover/use change is important for studies on climate change, soil carbon, and biodiversity assessments. Available reconstructions focus on the net area difference between two time steps (net changes) instead of accounting for all area gains and losses (gross changes). This leads to a serious underestimation of land‐cover/use dynamics with impacts on the biogeochemical and environmental assessments based on these reconstructions. In this study, we quantified to what extent land‐cover/use reconstructions underestimate land‐cover/use changes in Europe for the 1900–2010 period by accounting for net changes only. We empirically analyzed available historic land‐change data, quantified their uncertainty, corrected for spatial‐temporal effects and identified underlying processes causing differences between gross and net changes. Gross changes varied for different land classes (largest for forest and grassland) and led to two to four times the amount of net changes. We applied the empirical results of gross change quantities in a spatially explicit reconstruction of historic land change to reconstruct gross changes for the EU27 plus Switzerland at 1 km spatial resolution between 1950 and 2010. In addition, the reconstruction was extended back to 1900 to explore the effects of accounting for gross changes on longer time scales. We created a land‐change reconstruction that only accounted for net changes for comparison. Our two model outputs were compared with five commonly used global reconstructions for the same period and area. In our reconstruction, gross changes led in total to a 56% area change (ca. 0.5% yr^?1) between 1900 and 2010 and cover twice the area of net changes. All global reconstructions used for comparison estimated fewer changes than our gross change reconstruction. Main land‐change processes were cropland/grassland dynamics and afforestation, and also deforestation and urbanization.     

Estimating soil carbon fluxes following land-cover change: a test of some critical assumptions for a region in Costa Rica

Changes in soil carbon storage that accompany land‐cover change may have significant effects on the global carbon cycle. The objective of this work was to examine how assumptions about preconversion soil C storage and the effects of land‐cover change influence estimates of regional soil C storage. We applied three models of land‐cover change effects to two maps of preconversion soil C in a 140 000 ha area of northeastern Costa Rica. One preconversion soil C map was generated using values assigned to tropical wet forest from the literature, the second used values obtained from extensive field sampling. The first model of land‐cover change effects used values that are typically applied in global assessments, the second and third models used field data but differed in how the data were aggregated (one was based on land‐cover transitions and one was based on terrain attributes). Changes in regional soil C storage were estimated for each combination of model and preconversion soil C for three time periods defined by geo‐referenced land‐cover maps. The estimated regional soil C under forest vegetation (to 0.3 m) was higher in the map based on field data (10.03 Tg C) than in the map based on literature data (8.90 Tg C), although the range of values derived from propagating estimation errors was large (7.67–12.40 Tg C). Regional soil C storage declined through time due to forest clearing for pasture and crops. Estimated CO₂ fluxes depended more on the model of land‐cover change effects than on preconversion soil C. Cumulative soil C losses (1950–1996) under the literature model of land‐cover effects exceeded estimates based on field data by factors of 3.8–8.0. In order to better constrain regional and global‐scale assessments of carbon fluxes from soils in the tropics, future research should focus on methods for extrapolating regional‐scale constraints on soil C dynamics to larger spatial and temporal scales.     

Assessing the impacts of ecological governance on carbon storage in an urban coal mining subsidence area

Carbon storage, which is considered one of the important service functions of ecosystems, plays an irreplaceable role in maintaining the regional carbon balance and regulating the climate. Regional carbon storage is closely related to regional land use and land cover (LULC). With the development and expansion of coal resource-based cities, the construction areas of cities have started to overlap with underground coal resources. Coal mining leads to regional LULC changes, such as large-scale surface subsidence and subsidence waterlogging, and LULC has changed and consequently affected carbon storage in urban coal mining subsidence areas. This study analyses the change trend of carbon storage and clarifies the effect of ecological governance being implemented in the urban coal mining subsidence area. First, the LULC change map of the ecological governance scenario was obtained via remote sensing technology. Then, the natural evolution scenario from 2000 to 2021 was simulated using the hybrid cellular automata and Markov chain, also named the CA–Markov model. Finally, combined with the subsidence waterlogging in the urban subsidence area, the InVEST model was used to analyse the spatial–temporal variation characteristics of carbon storage. The analysis results showed that LULC and carbon storage in small-scale urban coal mining subsidence areas changed dramatically between 2000 and 2021 due to coal mining and ecological governance. The subsidence waterlogging area increased by 1033.83 ha, resulting in total carbon storage decreasing by 37,560.21 t. Subsidence waterlogging is the key influencing factor in the decrease in carbon storage. The forest area increased by 1270.83 ha, resulting in a total carbon storage increase of 216,531.04 t. Forest is the crucial increasing factor in carbon storage. The changes in carbon storage in the urban coal mining subsidence area can be classified as follows: obvious improvement area, basically unchanged area, and significantly degraded area. As opposed to the natural evolution scenario, the ecological governance scenario increased the coverage of the “obvious improvement area” by 818.46 ha in the urban coal mining subsidence area. Overall, this study illustrates that ecological governance can effectively improve carbon sequestration and is conducive to the healthy development of coal resource-based cities.     

Assessing the influence of historic net and gross land changes on the carbon fluxes of Europe

Legacy effects of land cover/use on carbon fluxes require considering both present and past land cover/use change dynamics. To assess past land use dynamics, model‐based reconstructions of historic land cover/use are needed. Most historic reconstructions consider only the net area difference between two time steps (net changes) instead of accounting for all area gains and losses (gross changes). Studies about the impact of gross and net land change accounting methods on the carbon balance are still lacking. In this study, we assessed historic changes in carbon in soils for five land cover/use types and of carbon in above‐ground biomass of forests. The assessment focused on Europe for the period 1950 to 2010 with decadal time steps at 1‐km spatial resolution using a bookkeeping approach. To assess the implications of gross land change data, we also used net land changes for comparison. Main contributors to carbon sequestration between 1950 and 2010 were afforestation and cropland abandonment leading to 14.6 PgC sequestered carbon (of which 7.6 PgC was in forest biomass). Sequestration was highest for old‐growth forest areas. A sequestration dip was reached during the 1970s due to changes in forest management practices. Main contributors to carbon emissions were deforestation (1.7 PgC) and stable cropland areas on peaty soils (0.8 PgC). In total, net fluxes summed up to 203 TgC yr^?1 (98 TgC yr^?1 in forest biomass and 105 TgC yr^?1 in soils). For areas that were subject to land changes in both reconstructions (35% of total area), the differences in carbon fluxes were about 68%. Overall for Europe the difference between accounting for either gross or net land changes led to 7% difference (up to 11% per decade) in carbon fluxes with systematically higher fluxes for gross land change data.     

Land Transitions in the Tropics: Going Beyond the Case Studies

Estimates of the percent of Earth's land surface that has either been transformed or degraded by human activity range between 39 and 50 percent, with agriculture accounting for the vast majority of these changes. Although much of the focus of research on land use and cover change in the tropics has been on deforestation, ongoing socioeconomic changes both locally and globally have made land transitions in the tropics extremely fluid. In addition, feedbacks between land cover change and human behavior constrain the extent and trajectories of land transitions. The sustainability of land use systems in the tropics depends on an understanding of coupled human–natural systems that can lead to general frameworks for management and prediction. The unprecedented availability of land use/cover data together with ecological data collected at large spatial scales offer exciting opportunities for advancing our understanding of socioecological systems. We rely on six studies of land transitions in the tropics to illustrate some promising approaches and pose critical questions to guide this body of research.     

The impact of projected increases in urbanization on ecosystem services

Alteration in land use is likely to be a major driver of changes in the distribution of ecosystem services before 2050. In Europe, urbanization will probably be the main cause of land-use change. This increase in urbanization will result in spatial shifts in both supplies of ecosystem services and the beneficiaries of those services; the net outcome of such shifts remains to be determined. Here, we model changes in urban land cover in Britain based on large (16%) projected increases in the human population by 2031, and the consequences for three different services--flood mitigation, agricultural production and carbon storage. We show that under a scenario of densification of urban areas, the combined effect of increasing population and loss of permeable surfaces is likely to result in 1.7 million people living within 1 km of rivers with at least 10 per cent increases in projected peak flows, but that increasing suburban 'sprawl' will have little effect on flood mitigation services. Conversely, losses of stored carbon and agricultural production are over three times as high under the sprawl as under the 'densification' urban growth scenarios. Our results illustrate the challenges of meeting, but also of predicting, future demands and patterns of ecosystem services in the face of increasing urbanization.     

Accounting for Emissions and Sinks from the Biogeochemical Cycle of Carbon in the U.S. Economic Input‐Output Model

Biogeochemical cycles are essential ecosystem services that continue to degrade as a result of human activities, but are not fully considered in efforts toward sustainable engineering. This article develops a model that integrates the carbon cycle with economic activities in the 2002 U.S. economy. Data about the carbon cycle, including emissions and sequestration flows, is obtained from the greenhouse gas inventory of the U.S. Environmental Protection Agency. Economic activities are captured by the economic input‐output model available from the Bureau of Economic Analysis. The resulting model is more comprehensive in its accounting for the carbon cycle than existing methods for carbon footprint (CF) calculations. Examples of unique flows in this model include the effect of land‐use and land‐cover change on carbon dioxide flow within the U.S. national boundary, carbon sequestration in urban trees, and emissions resulting from liming. This model is used to gain unique insight into the carbon profile of U.S. economic sectors by providing the life cycle emissions and sequestration in each sector. Such insight may be used to support policies, manage supply chains, and be used for more comprehensive CF calculations.