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1.
乡村人口、耕地和居民点(人—耕—居)是农村社会经济发展的核心要素,其变化反映了农村特定时期的人地关系。该文综合运用热点分析和脱钩模型,探讨2009-2017年湖北省县域乡村人—耕—居动态演化特征和时空关联模式,揭示乡村人—耕—居发展的内在关系与规律。结果表明:1)湖北省乡村人—耕—居整体以“人减耕减居增”变化为主,空间上未呈现典型的高低值集聚特征,但武汉市及其周边区域是人口和居民点变化的冷热点集聚区。2)强复钩和衰退复钩分别是湖北省乡村人口与居民点变化及人口与耕地变化的最主要类型,农村居民点粗放利用趋势明显,城镇发展与耕地保护的矛盾依然突出。3)湖北省县域乡村人—耕—居变化共有7种时空关联模式,不同类型分布体现了城镇化和社会经济发展的地域分异性,人—居强复钩与人—耕衰退复钩组合是最主要类型,湖北省县域多数乡村发展尚处于快速城镇化的自然衰退期。研究成果有助于深入理解快速城镇化期乡村人地关系,能够为乡村振兴分类、分标准施策提供借鉴。  相似文献   
2.
能源消费是人类活动影响全球气候变化的主要行为之一,对能源消费导致的碳足迹进行研究具有重要意义。本文首先应用能源消费碳足迹的相关概念和方法,计算得到了甘肃省1990年-2009年的总碳足迹、各能源消费类型的碳足迹、碳足迹产值和碳足迹生态压力;然后利用STIRPAT模型进行岭回归函数拟合,探讨了经济增长与碳足迹之间的定量关系,并验证了环境库兹涅茨曲线的存在性;最后通过脱钩指数分析进一步研究了经济增长与碳足迹之间的动态变化关系。结果表明:碳足迹从1990年的每人0.091 ha上升为2009年的每人0.191 ha,呈现波动上升的趋势。各能源消费类型的碳足迹构成中,煤和石油占据了绝对地位,其中又以煤所占比重最大,石油次之,天然气所起的作用甚微。碳足迹产值由1990年的1.18万元ha-1增加为2009年的2.51万元ha-1,碳足迹生态压力也从1990年的0.10上升至2009年的0.24。人口和人均GDP是驱动碳足迹增长的主要因素,且回归分析和脱钩指数分析都表明经济增长与碳足迹之间存在环境库兹涅茨曲线。  相似文献   
3.
In this study, we examined the year 2011 characteristics of energy flux partitioning and evapotranspiration of a sub‐alpine spruce forest underlain by permafrost on the Qinghai–Tibet Plateau (QPT). Energy balance closure on a half‐hourly basis was H + λE = 0.81 × (Rn ? G ? S) + 3.48 (W m?2) (r2 = 0.83, n = 14938), where H, λE, Rn, G and S are the sensible heat, latent heat, net radiation, soil heat and air‐column heat storage fluxes, respectively. Maximum H was higher than maximum λE, and H dominated the energy budget at midday during the whole year, even in summer time. However, the rainfall events significantly affected energy flux partitioning and evapotranspiration. The mean value of evaporative fraction (Λ = λE/(λE + H)) during the growth period on zero precipitation days and non‐zero precipitation days was 0.40 and 0.61, respectively. The mean daily evapotranspiration of this sub‐alpine forest during summer time was 2.56 mm day?1. The annual evapotranspiration and sublimation was 417 ± 8 mm year?1, which was very similar to the annual precipitation of 428 mm. Sublimation accounted for 7.1% (30 ± 2 mm year?1) of annual evapotranspiration and sublimation, indicating that the sublimation is not negligible in the annual water balance in sub‐alpine forests on the QPT. The low values of the Priestley–Taylor coefficient (α) and the very low value of the decoupling coefficient (Ω) during most of the growing season suggested low soil water content and conservative water loss in this sub‐alpine forest. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   
4.
基于资源环境压力与经济发展的相互耦合关系视角,基于脱钩理论构建了资源环境与经济增长的脱钩状态评价指标体系,引入生态足迹法并结合改进的弹性脱钩分析方法,探讨了沈阳市2002~2009年资源环境与经济发展的脱钩程度、时序演变及其综合脱钩程度等.研究结果表明:2002 ~ 2005年研究区经济增长导致资源环境压力逐渐增大,2005~2009年资源环境压力趋缓;整个时段内研究区资源环境与经济发展脱钩状态以相对脱钩为主,呈“相对脱钩4—强耦合—相对脱钩4—相对脱钩1”的演变趋势.  相似文献   
5.
康定杂岩位于扬子地块西缘,通过对四川康定—冕宁—攀枝花—云南元谋地区出露的康定杂岩中基性、中性、酸性岩岩石学、锆石Lu-Hf同位素等多方面系统研究,确定这套岩石形成于岛弧环境。分析表明:康定杂岩中镁铁质侵入体锆石εHf(t)变化范围-4.2~+11.0,Hf模式年龄742~2386 Ma;长英质侵入体锆石εHf(t)变化范围-4.9~+9.4,Hf模式年龄为967~2707 Ma;暗示康定杂岩体复杂的构造成因。锆石Hf同位素分析表明其岩浆锆石具有与扬子地块西缘同时代镁铁质/长英质侵入体相似的Hf同位素组成,暗示其相似的岩浆起源。研究表明,康定杂岩为大洋俯冲背景下的产物,镁铁质侵入体来源于较为亏损地幔源区,长英质侵入体为新生陆壳与古老地壳物质相互作用形成的产物。锆石Hf同位素数据表明,康定侵入体杂岩中锆石Hf-全岩Nd解耦,为"锆石效应"与少量地壳物质加入共同作用结果。结合岩石学、地层学、构造及地球化学证据综合表明,新元古代时期,扬子地块可能位于Gondwana超大陆的边缘,而不是澳大利亚与北美Laurentia古陆之间的连接部分。  相似文献   
6.
The sedimentary infills of subglacially eroded bedrock troughs in the Alps are underexplored archives for the timing, extent and character of Pleistocene glaciations but may contain excellent records of the Quaternary landscape evolution over several glacial–interglacial cycles. The onset of sedimentation in these bedrock troughs is often reflected by diamicts and gravels directly overlying bedrock in the deepest basin segments. Subglacial or proglacial depositional environments have been proposed for these coarse‐grained basal units but their characteristics and origin remain controversial. This article presents results from drill cores that recovered a coarse‐grained basal unit in a major buried bedrock‐trough system in the Lower Glatt Valley, northern Switzerland. The excellent core recovery allowed a detailed study combining macroscopic, microscopic and geochemical methods and gives unprecedented insights into the transition from erosion to deposition in overdeepened bedrock troughs. These results show that the basal infill comprises diamicts, interpreted as subglacial tills, separated by thin sorted interbeds, originating from subglacial cavity deposition. The stacking of these units is interpreted to represent repeated switching between a coupled and decoupled ice–bed‐interface indicating an ever‐transforming mosaic of subglacial bed conditions. Decoupling in response to high basal water pressures is probably promoted by the confined subglacial hydraulic conditions resulting from the bedrock acting as aquitards, the narrow reverse sloping outlet and a large catchment area. While stratigraphic and lithological evidence suggests that erosion and the onset of basal sedimentation occurred during the same glaciation, different scenarios for the relative timing of infilling in relation to formation and glaciation of the bedrock trough are discussed. Overlying deltaic and glaciolacustrine sediments suggest deposition during subsequent deglaciation of the bedrock trough. The basal sediment characteristics are in agreement with previous reports in hydrogeological and seismic exploration and suggest the occurrence of similar basal successions in other subglacially overdeepened basins in the Alps and elsewhere.  相似文献   
7.
We present in situ trace element and Nd isotopic data of apatites from metamorphosed and metasomatized (i.e., altered) and unaltered granitoids in the Songnen and Jiamusi massifs in the eastern Central Asian Orogenic Belt, with the aim of fingerprinting granitoid petrogenesis, including both the magmatic and post-magmatic evolution processes. Apatites from altered granitoids (AG) and unaltered granitoids (UG) are characterized by distinct textures and geochemical compositions. Apatites from AG have irregular rim overgrowths and complex internal textures, along with low contents of rare earth elements (REEs), suggesting the re-precipitation of apatite during epidote crystallization and/or leaching of REEs from apatite by metasomatic fluids. εNd(t) values of the these apatites are decoupled from zircon εHf(t) values for most samples, which can be attributed to the higher mobility of Nd as compared to Sm in certain fluids. Apatites from UG are of igneous origin based on their homogeneous or concentric zoned textures and coupled Nd-Hf isotopic compositions. Trace element variations in igneous apatite are controlled primarily by the geochemical composition of the parental melt, fractional crystallization of other REE-bearing minerals, and changes in partition coefficients. Sr contents and Eu/Eu* values of apatites from UG correlate with whole-rock Sr and SiO2 contents, highlighting the effects of plagioclase fractionation during magma evolution. Apatites from UG can be subdivided into four groups based on REE contents. Group 1 apatites have REE patterns similar to the host granitoids, but are slightly enriched in middle REEs, reflecting the influence of the parental melt composition and REE partitioning. Group 2 apatites exhibit strong light REE depletions, whereas Group 3 apatites are depleted in middle and heavy REEs, indicative of the crystallization of epidote-group minerals and hornblende before and/or during apatite crystallization, respectively. Group 4 apatites are depleted in heavy REEs, but enriched in Sr, which are features of adakites. Some unusual geochemical features of the apatites, including the REE patterns, Sr contents, Eu anomalies, and Nd isotopic compositions, indicate that inherited apatites are likely to retain the geochemical features of their parental magmas, and thus provide a record of small-scale crustal assimilation during magma evolution that is not evident from the whole-rock geochemistry.  相似文献   
8.
针对电涌保护器(SPD)级间能量配合试验中配合失效的问题,主要利用波的传输理论与基尔霍夫定律进行分析,结合JB/T 10618-2006(组合式电涌保护器)的规定假设一套组合型SPD,通过基础理论分析与精确计算得出:当被保护装置属于低频(直流)设备时,在不影响信号强度的情况下,退耦元件采用电感或电阻型元件均可;当被保护装置属于高频设备时,退耦元件只能选用低电感量的电阻型退耦元件.退耦元件的参数值均可按照波的传输理论与基尔霍夫定律进行理论计算.这在组合型SPD退耦元件的选型过程中,具有重要的指导意义.  相似文献   
9.
10.
城市拓展对资源消耗的影响程度分析——以长春市为例   总被引:2,自引:1,他引:1  
刘艳军  张婧 《地理科学》2012,(9):1093-1098
构建脱钩状态模型和响应程度模型,通过定量研究1995~2010年长春市城市拓展对资源消耗的影响程度,得到以下结论:①长春市城市拓展与资源消耗总体呈现"双增长"特征,城市快速拓展导致的资源消耗及资源环境压力不断增大;②长春市城市拓展与资源消耗始终处于"相对脱钩"状态,且资源消耗增长速度随着城市拓展呈先相对下降、后又相对提升的趋势。在城市拓展规模保持总体稳定增长的情况下,资源消耗变化是影响二者脱钩状态与脱钩程度演化的关键因素;③随着长春市城市拓展规模的不断扩大,其对资源消耗增长的影响程度持续增大,进一步说明城市拓展作为资源消耗的驱动力,其变化是导致长春市城市拓展对资源消耗影响程度增大的重要推动因素。  相似文献   
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