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1.
Affected by natural and anthropogenic disturbances such as forest fires, insect-induced mortality and harvesting, forest stand age plays an important role in determining the distribution of carbon pools and fluxes in a variety of forest ecosystems. An improved understanding of the relationship between net primary productivity (NPP) and stand age (i.e., age-related increase and decline in forest productivity) is essential for the simulation and prediction of the global carbon cycle at annual, decadal, centurial, or even longer temporal scales. In this paper, we developed functions describing the relationship between national mean NPP and stand age using stand age information derived from forest inventory data and NPP simulated by the BEPS (Boreal Ecosystem Productivity Simulator) model in 2001. Due to differences in ecobiophysical characteristics of different forest types, NPP-age equations were developed for five typical forest ecosystems in China (deciduous needleleaf forest (DNF), evergreen needleleaf forest in tropic and subtropical zones (ENF-S), deciduous broadleaf forest (DBF), evergreen broadleaf forest (EBF), and mixed broadleaf forest (MBF)). For DNF, ENF-S, EBF, and MBF, changes in NPP with age were well fitted with a common non-linear function, with R(2) values equal to 0.90, 0.75, 0.66, and 0.67, respectively. In contrast, a second order polynomial was best suitable for simulating the change of NPP for DBF, with an R(2) value of 0.79. The timing and magnitude of the maximum NPP varied with forest types. DNF, EBF, and MBF reached the peak NPP at the age of 54, 40, and 32 years, respectively, while the NPP of ENF-S maximizes at the age of 13 years. The highest NPP of DBF appeared at 122 years. NPP was generally lower in older stands with the exception of DBF, and this particular finding runs counter to the paradigm of age-related decline in forest growth. Evaluation based on measurements of NPP and stand age at the plot-level demonstrates the reliability and applicability of the fitted NPP-age relationships. These relationships were used to replace the normalized NPP-age relationship used in the original InTEC (Integrated Terrestrial Ecosystem Carbon) model, to improve the accuracy of estimated carbon balance for China's forest ecosystems. With the revised NPP-age relationship, the InTEC model simulated a larger carbon source from 1950-1980 and a larger carbon sink from 1985-2001 for China's forests than the original InTEC model did because of the modification to the age-related carbon dynamics in forests. This finding confirms the importance of considering the dynamics of NPP related to forest age in estimating regional and global terrestrial carbon budgets.  相似文献   
2.
以神府矿区为例,选取土地利用、植被覆盖、土壤、气象等生态环境与统计数据指标,利用RS和GIS技术构建生态系统服务遥感测量评估指标体系,评估研究区2005-2015年生态系统服务变化及时空分布特征,进一步探究神府矿区不同开采强度对生态系统服务的影响并进行驱动力分析。研究结果表明:(1)2005年、2010年、2015年研究区的总生态系统服务分别为1.598×1010元、1.905×1010元、2.134×1010元,呈现逐年递增的趋势;(2)生态系统服务功能中水土保持价值比例最大,草地的单位面积生态系统服务价值最高,耕地、草地生态系统为该地区贡献了最多的生态系统服务价值;(3)研究区生态系统服务分布表现为由东北向西南逐渐降低的趋势,不同开采强度下的生态系统服务增长变化较为相似,煤炭开采区域生态系统服务未显著下降,整体较为平稳。对生态系统服务变化的驱动分析表明在近年来相对改善的气候环境与人工修复共同作用下,神府矿区生态系统服务未发生明显的缩减。此类半干旱生态脆弱矿区国土空间生态修复适宜通过主动的“保护性开发”以及“人工诱导+自然修复”为主的方式,避免大范围与高强度的水土扰动型治理,通过适度的人为干预保证与维持区域内生态系统服务的功能。研究成果不但揭示高强度煤矿开采下的生态环境变化,也对西部生态脆弱区环境做了定量评估;同时,为将来的矿区重建提供了重要的依据。  相似文献   
3.
在GIS和RS支持下,利用土地利用类型数据、地面气象数据和遥感影像数据,以青岛市为例,研究了市域尺度下的植被NPP空间分布特征.结果表明:青岛市NPP值为0~288 g·m-2·a-2,林地NPP值较高,耕地次之,建成区等区域最小.在小尺度区域内,NPP分布受土地利用类型影响较大,受气象因素影响较小.NPP模块在数据获取上比较容易,仅利用土地利用类型数据、地面气象数据和遥感数据就可以对陆地植被NPP进行计算,实际应用可操作性强.30 m分辨率植被NPP计算值更适宜于在市级小尺度区域内应用.  相似文献   
4.
Vegetation net primary productivity (NPP) is a sensitive indicator to characterize the response of terrestrial ecosystems to the climate change. Projections of the NPP changes of the Loess Plateau under future climate scenarios have great significances in revealing the interactions among terrestrial ecosystems and climatic systems, as well as instructing future vegetation construction of this region. Here, we carried out a case study on the Yangou watershed in the Loess Plateau. Using the vegetation-producing process model (VPP) established for such small watersheds, we simulated the NPP of the Yangou watershed under different scenarios of climate changes. The results showed that the NPP significantly increased with the precipitation increasing and evidently decreased with the temperature increasing where the climate change occurred in the whole year or in the summer half year. However, where the climate change occurred in the winter half year, the increased precipitation had little effect on the NPP, and the increased temperature significantly reduced the NPP. There were clear differences among the response sensitivities of different vegetation types with trees and shrubs were more sensitive to the changes in temperature and precipitation than crops and grasses. Currently, the most favourable climate change scenario to the NPP in the Yangou watershed was T0P15 under which the precipitation increased by 15% and the temperature did not changed, in the whole year; in the meantime, the most unfavourable climate change scenarios was T2P-15 under which the precipitation declined by 15% and the temperature increased by 2℃, in the whole year.  相似文献   
5.
广东省土地覆盖变化对植被净初级生产力的影响分析   总被引:3,自引:0,他引:3  
理解土地利用/覆盖变化对植被净初级生产力(Net Primary Productivity,NPP)的影响对于全球碳循环和粮食安全具有重要意义。论文采用优化的CASA(Carnegie-Ames-Stanford Approach)模型估算广东省2000、2005和2010年NPP,分析NPP的空间格局和土地覆盖的时空动态,研究土地覆盖变化对NPP的影响。结果表明:1)广东省NPP空间分布不均,形成一系列高值区和低值区;总体上是粤中区最高,珠三角区最低。2)2000—2010年广东省土地覆盖变化程度增强,城市用地和耕地变化最大,主要集中在珠三角区和粤中区。3)在气候变化条件下,以城市扩张为主导的广东省土地覆盖类型变化整体上造成NPP的损失,损失量主要来自林地和耕地向低生产力土地覆盖类型的转换,尤其是被城市用地占用;不同生态区NPP损失差异显著,珠三角区和粤中区NPP损失较为严重;2005—2010年珠三角区NPP损失量有所降低,其他生态区均有所增加,体现了城市扩张对NPP影响的复杂性。  相似文献   
6.
2000~2010年贵州省植被净初级生产力时空变化研究   总被引:1,自引:0,他引:1  
为了探明贵州省植被净初级生产力(NPP)在2000~2010年的变化状况,以2000~2010年植被NPP数据为基础,运用ArcG IS和SPSS进行综合分析。结果表明:近11年间,草地、城镇用地、阔叶林、针叶林和湿地等面积呈增加趋势,而灌木林和农田则持续减少,其中农田面积变化尤为明显;2000~2010年贵州省植被NPP变化较大,NPP变化范围为778~889 g/(m2·a),平均值为828.1 g/(m2·a),NPP缓慢上升趋势;全省NPP分布有明显地域性差异,铜仁和六盘水为显著增加(P0.05),其余地州市增加缓慢(P0.05)。黔东南年均NPP最高((927±111)g/(m 2·a)),毕节最低((725±107)g/(m2·a))。NPP变化趋势为东南向西北方向递减,而往西北方向NPP波动程度明显;阔叶林和灌木林缓慢下降,而针叶林和针阔混交林则上升。NPP表现为针阔混交林阔叶林针叶林灌木林。  相似文献   
7.
NPP增长驱动下的中国森林生态系统碳汇   总被引:8,自引:1,他引:7  
森林生态系统能够有效地吸收大气中的CO2,在一定程度上缓解全球变暖的压力。生态系统固碳能力取决于两个关键因素:NPP的增长强度与碳周转时间。本文通过对遥感监测到的森林生态系统NPP增长趋势进行校正,结合森林样地实测数据得到的碳分配系数与周转时间,建立了中国森林生态系统碳周转模型,并模拟了1982~1999年森林生态系统的碳汇量及其年际变化。结果表明:1982~1999年,我国森林生态系统的平均碳汇量为0.051 PgC a-1,其中植被的碳汇量为0.034 PgC a-1,凋落物的碳汇量为0.013 PgC a-1,土壤的碳汇量为0.004PgC a-1;不同森林类型中,常绿针叶林和常绿阔叶林的碳汇贡献最大,落叶针叶林和针阔叶混交林贡献最小;进一步分析表明森林植被的固碳效率显著地受到碳周转时间的控制。  相似文献   
8.
目的分析堆芯中子通量测量系统指套管磨损分布规律,提出处理准则优化建议。方法统计了指套管在堆芯不同位置的磨损数量,分析了指套管磨损分布规律。结合指套管和导向管的结构特点和视频检查结果,分析了指套管的磨损原因,并提出了指套管磨损处理准则优化建议。结果指套管磨损位置主要集中在P1和P4两处,其中P1位置磨损数量最多,而P2、P3和P5位置磨损数量较少。P1和P4两处的指套管磨损形貌差异较大,在P1位置,由于指套管易发生方向随机的高频低振幅微动磨损行为,导致产生较窄的环槽形缺陷;在P4位置,指套管则易发生低频高振幅的微动磨损行为,导致产生较宽的楔形缺陷。结论指套管和导向管的结构特性、冷却剂流场等因素均对指套管磨损有较大影响,不同位置处指套管磨损缺陷形貌差异较大。有必要分别建立针对P1位置和P4位置的指套管磨损处理准则,使得核电厂对于指套管的磨损处理更有针对性,以有效延长指套管的服役寿命。  相似文献   
9.
近40年气候变化对江西自然植被净第一性生产力的影响   总被引:1,自引:0,他引:1  
根据全球气候变化的趋势,采用植被净第一性生产力模型,对江西省南昌、吉安、赣州3地近40年气候变化对自然植被净第一性生产力(NPP)的影响进行研究,并模拟了3地自然植被NPP在未来气候3种水热条件下的变化趋势。此外还以1980年江西全省自然植被NPP为例分析了自然植被NPP的区域分布特征,结果表明:3地近40年自然植被NPP平均值分别为1319 、1311和1320 t/hm2〖DK1〗·a,总体上都呈上升的趋势。 当年均气温增加2℃且降水量增加20%时,NPP值增加了149%~1585%;随着年均气温增加2℃且降水量减少20%,NPP减少了477%~516%;当年均气温增加2℃且降水量不变时,NPP增加了530%~569%。江西自然植被NPP区域分布特征由东、南、西3个方向向北呈放射状分布,随着地形由高山向丘陵、平原的方向变化而减小。  相似文献   
10.
Net primary production (NPP) of terrestrial ecosystems provides food, fiber, construction materials, and energy to humans. Its demand is likely to increase substantially in this century due to rising population and biofuel uses. Assessing national forest NPP is of importance to best use forest resources in China. To date, most estimates of NPP are based on process-based ecosystem modeling, forestry inventory, and satellite observations. There are little efforts in using spatial statistical approaches while large datasets of in-situ observed NPP are available for Chinese forest ecosystems. Here we use the surveyed forest NPP and ecological data at 1,266 sites, the data of satellite forest coverage, and the information of climate and topography to estimate Chinese forest NPP and their associated uncertainties with two geospatial statistical approaches. We estimate that the Chinese forest and woodland ecosystems have total NPP of 1,325 ± 102 and 1,258 ± 186 Tg C year−1 in 1.57 million km2 forests with a regression method and a kriging method, respectively. These estimates are higher than the satellite-based estimate of 1,034 Tg C year−1 and almost double the estimate of 778 Tg C year−1 using a process-based terrestrial ecosystem model. Cross-validation suggests that the estimates with the kriging method are more accurate. Our developed geospatial statistical models could be alternative tools to provide national-level NPP estimates to better use Chinese forest resources.  相似文献   
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