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1.
青海省属于全国四大牧区之一,及时监测草地植被长势、准确估算牧草产量对青海牧区可持续发展与生态保护具有重要意义。草地产草量遥感估算主要基于植被指数与地面实测数据的统计关系,但是估算涉及植被指数、统计模型和建模指标等因素,不同组合建立的估算模型的精度不同。本文基于青海省MODIS数据与地面实测产草量数据,选择了6种植被指数（NDVI、EVI、RVI、DVI、RDVI、MSAVI）、5种统计模型（简单线性模型、二次多项式模型、幂函数模型、指数函数模型、对数函数模型）以及3种建模指标（植被指数年度最大值VImax、植被指数生长季累积值VIseason-cum、植被指数年度累积值VIannual-cum）,研究不同组合下估算模型的精度差异,并从中选出最优产草量估算模型,用于估算青海省2015年和2016年的产草量。结果表明：（1）6种植被指数中,基于NDVI的产草量估算精度最高;非线性模型的估算精度高于线性模型,尤其是指数模型,适用于大多数草地类型产草量的估算;基于NDVI年度最大值的估算模型对大多数草地类型都具有最高的决定系数（R2）。（2）从干重来看,高产草量区（>1 200 kg·hm-2）主要位于青海东部的高寒草原,中等产草量区（600~1 200 kg·hm-2）位于青海南部和东部的高寒草原和禾草草原,低产草量区（<600 kg·hm-2）位于青海西部和北部的高寒草甸、高寒草原、高寒荒漠和盐生草甸。（3）与2015年相比,2016年青海省干草总产量减少31.60×104 t,减幅为1.36%。其中,禾草草原和高寒草甸的减产幅度最大,而荒漠草原和盐生草甸的产量则有所增加。本文可为草地产草量遥感估算的研究和实践提供参考。 相似文献
2.
《Norsk geografisk tidsskrift. Norwegian journal of geography》2012,66(2):77-84
Because of its species-rich hay meadows and old pollards that are traditionally managed, Ulvund in Myrkdalen, Voss, is one of 14 areas in Hordaland county that are considered to be of special interest for cultural landscape conservation. The spatial patterns of species richness were investigated in hay meadows at Ulvund. Two main types of vegetation were recognised in managed meadows. Unfertilised and species-rich areas with a rather short field layer were situated in the steep parts of the meadows. Fertilised and species-poor areas with a high field layer were situated on flat or gently sloping areas. This spatial pattern is recognised in other west Norwegian hay meadows as well and is very likely linked to historical differences in land management; the flatter areas were formerly used as heavily fertilised permanent tilled fields for grain production, while the steep areas were used for hay production. As the conservation value largely lies in small, localized parts of the farms, conservation management actions can also be localized and thus feasible under modern conditions. 相似文献
3.
Seasonal changes in pasture biomass, production and offtake under the transhumance system in northern Pakistan 总被引：1，自引：0，他引：1
R.M. Omer A.J. Hester I.J. Gordon M.D. Swaine S.M. Raffique 《Journal of Arid Environments》2006,67(4):641-660
An understanding of seasonal changes in pasture biomass, production and offtake of different range types is fundamentally important for the efficient management of livestock grazing. However, few studies have quantified these changes for transhumance systems, despite the fact that transhumance is still the main form of livestock management in several regions of the world and is often critical for the livelihoods of the people. One such area is the Northern Areas of Pakistan, where six villages and their pastures were selected for study. Pastures were categorized within foothill, dry temperate and alpine range types, and seasonal biomass, production and offtake of the vegetation was estimated by clipping paired caged and uncaged quadrats. The alpine range type had by far the highest biomass and offtake; the foothill and dry temperate range types were much more sparsely vegetated. Although alpine pastures were heavily used, particularly in spring, there was no evidence for consistent over-utilization of pasture resources. Within the dry temperate range type, production was highest during spring but significantly under-used. This indicates a potential for increased use of dry temperate pastures during spring, an important period both for early recovery of livestock body condition after winter and to reduce the heavy pressure on the alpine pastures at this time. 相似文献
4.
《Journal of Arid Environments》2007,68(4):661-670
Riparian meadows of southern Patagonia are temporally and spatially heterogeneous habitats. They are thought to play a key role in regulating the dynamics of arid grazed steppes of the region. We conducted a 2-year study with sheep to determine the influence of two grazing conditions (deferment and spring grazing) on structural and nutritional parameters of three vegetation types apparently associated with a soil moisture gradient in a riparian meadow in southern Santa Cruz (Argentina). Spring deferment allowed forage accumulation in very moist and intermediate vegetation types by the beginning of the summer and had no detrimental impact on forage quality. Deferment had no effect on biomass accumulation of the drier vegetation type at our study site. Structural attributes of the vegetation appeared to affect spatial grazing patterns of sheep. Soil-related patchiness, rather than sheep grazing, appeared to control vegetation structure and nutritional value. The proportion of more mesic plant communities in riparian habitats of Patagonia could determine the outcome of plant–animal interactions in these systems. Practical recommendations of grazing capacity in paddocks, or more theoretical considerations of ecosystem dynamics of the Patagonian steppes need to explicitly consider the internal patchiness of riparian habitats. 相似文献
5.
新疆地区表土孢粉分布规律及其与植被关系研究 总被引：2，自引：2，他引：2
对中国新疆地区218个样点进行植被调查及表土孢粉分析的研究结果表明,新疆地区温带山地针叶林、高寒草甸及盐生草甸、温带草原、荒漠以及荒漠-沙漠过渡带均具有相对特殊的孢粉组合,新疆南北向样带的孢粉图式揭示出表土孢粉从北到南随地形、纬度和植被的改变而发生的空间变化。针叶林区表土孢粉浓度平均值为22 602粒/g、草原为3 834粒/g、荒漠为1 762粒/g、沙漠为0-10粒/g。但在同一植被类型中,特别是在草原和荒漠中,孢粉浓度与植被盖度之间并不呈现线性相关关系。根据大空间尺度样品的A/C(蒿Artemisia/藜Chenopodiaceae)值的中位数统计,草原为1.264、荒漠为0.565、沙漠为0.243。Ep/C(麻黄Ephedra/藜Chenopodiaceae)比值的中位数在荒漠为0.098、草原为0.063。 相似文献
6.
Riparian meadows of southern Patagonia are temporally and spatially heterogeneous habitats. They are thought to play a key role in regulating the dynamics of arid grazed steppes of the region. We conducted a 2-year study with sheep to determine the influence of two grazing conditions (deferment and spring grazing) on structural and nutritional parameters of three vegetation types apparently associated with a soil moisture gradient in a riparian meadow in southern Santa Cruz (Argentina). Spring deferment allowed forage accumulation in very moist and intermediate vegetation types by the beginning of the summer and had no detrimental impact on forage quality. Deferment had no effect on biomass accumulation of the drier vegetation type at our study site. Structural attributes of the vegetation appeared to affect spatial grazing patterns of sheep. Soil-related patchiness, rather than sheep grazing, appeared to control vegetation structure and nutritional value. The proportion of more mesic plant communities in riparian habitats of Patagonia could determine the outcome of plant–animal interactions in these systems. Practical recommendations of grazing capacity in paddocks, or more theoretical considerations of ecosystem dynamics of the Patagonian steppes need to explicitly consider the internal patchiness of riparian habitats. 相似文献
7.
轮牧传统衰退:滇西北藏区亚高山草地退化的人文因素 总被引：1，自引：1，他引：1
滇西北藏区亚高山草地退化是个有目共睹的现实,有自然的原因也有人文的原因。以实地调查为基础,从藏民生计出发的研究发现,滇西北藏族的畜牧生产特点是6～9月位于3800m以上的高山草甸地带,11月至翌年3月位于3200m左右的亚高山草甸地带,属于轮牧作业;轮牧传统适应了气候和植物生长的季节性变化,有效地维持草地生产和传统围栏农业。轮牧传统的衰退,使牲畜集中在亚高山草甸地带,导致了草地退化。充分挖掘和尊重民族传统知识有助于退化草地恢复。 相似文献
8.
中国不同气候带各类型森林的生物量和净第一性生产力 总被引：27，自引：0，他引：27
根据<中国植被>的区划,将收集的全国984个样点的森林数据归并到5种气候带类型中,计算了各类型森林以及同一类型森林(分人工林和天然林)的生物量和净第一性生产力,还计算了不同气候带森林各器官的平均生物量和净第一性生产力.结果表明,从寒温带到热带各类型森林的生物量和净第一性生产力逐渐增加,天然林的生物量大于人工林生物量;除热带林外,人工林的净第一性生产力大于天然林净第一性生产力. 相似文献
9.
土地荒漠化是非常重要的生态环境问题,而科学评价荒漠化治理和零增长目标是否实现的必要前提是具有完善统一的评价体系。为此,联合国防治荒漠化公约（UNCCD）提出了土地退化零增长（LDN）的概念和监测指标。防治土地退化是中国的重要生态目标,中国已开展了多次全国土地荒漠化和沙化监测工作。但是,如何将这些监测结果用于土地退化的评估实践,尚未见报道。因此,本研究针对中国四大沙地,利用3期全国荒漠化和沙化监测数据,与基于UNCCD框架体系下的土地退化零增长（LDN）指标进行对比分析,并基于土地沙化程度变化趋势提出了中国沙化土地退化指标体系（CSLDN）。结果表明：UNCCD所提出的LDN监测指标与中国的荒漠化监测数据总体精度为0.51,中国沙化土地监测指标与LDN指标具有宏观一致性。此外,经本地优化后的CSLDN指标克服了低植被盖度区域LDN对土地退化和恢复的评价不准确的问题,更准确刻画了精细尺度空间内的土地动态变化状况,对土地退化防治意义重大。 相似文献
10.
青海高寒草甸退化演替中的植被指数 总被引：2，自引：0，他引：2
随着气候变化和人为活动干扰,高寒草甸退化已成为青藏高原严重的生态环境问题,精准识别其退化程度并制定相应恢复策略,对实现高寒草甸可持续发展具有重要意义。目前,低空间分辨率MODIS数据为草地遥感监测的主要数据源,但难以满足景观破碎度或异质性较强地区的应用。本研究基于野外调查资料,利用多源遥感数据（MODIS、Landsat、Sentinel-2）研究不同空间分辨率归一化植被指数（NDVI）对高寒草甸退化演替的响应,为准确评估青藏高原高寒草甸退化程度提供依据。结果表明：（1）随着高寒草甸退化,植被群落优势种演化趋势为禾草—矮嵩草—小嵩草—杂草群落;植被高度和生物量先快速下降,然后缓慢下降或趋于稳定,植被覆盖度和NDVI的变化呈相反特征。（2）随着湿地草甸旱化,植被群落优势种从藏嵩草演变为矮嵩草或小嵩草,湿地旱化初期植被高度、生物量和覆盖度平均值略低于原生湿地,NDVI略大于原生湿地,差异不显著。（3）植被高度、覆盖度和生物量与Sentinel-2或Landsat的NDVI相关性均优于MODIS,说明Sentinel-2和Landsat的NDVI对高寒草甸退化演替过程更加敏感,采用该数据能更准确评估高寒草甸退化程度。 相似文献
11.
We consider the current tendencies in the agricultural production of Siberia's steppe regions and the processes that are responsible for the current state and future utilization of pastures. It is shown that the ongoing reduction in livestock population, combined with a decrease in sown areas, has led to an increase in natural meadowlands, and to a widespread occurrence of post-pasture demutational successions. We outline the digression and demutation stages of steppe and sandy-steppe pastures and identify the features of their similarity and difference associated with resistance to grazing pressure. It is shown that overgrazing and underutilization decrease their natural potential. We have defined the degradation and desertification criteria for pastures, and the priorities of their utilization. 相似文献
12.
土地退化评价与监测技术路线的研究 总被引：22，自引：4，他引：18
在对 90年代后期国内外土地退化评价与监测主要进展分析基础上 ,归纳出了绝对、相对和差异三种退化的评价思想 ;直接运用图象处理软件 ,通过监督非监督分类选择几个基于RS、GIS的指标 ,给定不同的权重综合地确定土地退化类型和程度的两种技术监测路线。最后 ,结合中国的实际情况 ,以沙质荒漠化为例提出了在绝对退化思想指导下 ,通过确定土地退化生态基准的时空尺度 ,建立监测区内典型土地退化类型与程度的标准信息资源库 ,GIS数据与RS数据相融合的土地退化评价与监测的技术路线框架。 相似文献
13.
This paper provides a geospatial analysis of regional inequality across provinces, prefectures and counties in China from 1997 to 2010 under a comparative spatiotemporal conceptual framework. Despite significant spatial agglomeration at all spatial scales, the extent of agglomeration shows an obviously downward trend from 2003 to 2006. Substantially stronger agglomeration of economic development is demonstrated at county scales. Local indicators of spatial autocorrelation (LISA) are employed to visualize the local spatial characteristics of economic growth. Four snapshots (in the years 1997, 2001, 2005, and 2010) of LISA indicate a dramatic north-shifting of hot spots of economic growth in response to the northward movement of foreign investors and spatial agglomeration besides institutional forces in China. Furthermore, local spatial agglomeration demonstrates a heterogeneous process: hot spots of economic development along the coast, cold spots in western China and no significant spatial clusters in central China. As the major carries of scale economies, metropolitan regions see decreasing internal agglomeration during this period with the exception of the Yangtze River Delta area, which shows a strong spatial spillover into its neighbourhood. Finally, LISA Markov and geovisualization methods are employed to predict the long-run properties of spatial distribution in multi-scalar China. The results show that downward co-movements of a county with its neighbours are more frequently encountered, perhaps resulting in the continuous concentration of poor areas in the long run. 相似文献
14.
The contribution of climatic change and anthropogenic activities to vegetation productivity are not fully understood. In this study, we determined potential climate-driven gross primary production (GPPp) using a process-based terrestrial ecosystem model, and actual gross primary production (GPPa) using MODIS Approach in alpine grasslands on the Tibetan Plateau from 2000 to 2015. The GPPa was influenced by both climatic change and anthropogenic activities. Gross primary production caused by anthropogenic activities (GPPh) was calculated as the difference between GPPp and GPPa. Approximately 75.63% and 24.37% of the area percentages of GPPa showed increasing and decreasing trends, respectively. Climatic change and anthropogenic activities were dominant factors responsible for approximately 42.90% and 32.72% of the increasing area percentage of GPPa, respectively. In contrast, climatic change and anthropogenic activities were responsible for approximately 16.88% and 7.49% of the decreasing area percentages of GPPa, respectively. The absolute values of the change trends of GPPp and GPPh of meadows were greater than those of steppes. The GPPp change values were greater than those of GPPh at all elevations, whereas both GPPp and GPPh showed decreasing trends when elevations were greater than or equal to 5000 m, 4600 m and 4800 m in meadows, steppes and all grasslands, respectively. Climatic change had stronger effects on the GPPa changes when elevations were lower than 5000 m, 4600 m and 4800 m in meadows, steppes and all grasslands, respectively. In contrast, anthropogenic activities had stronger effects on the GPPa changes when elevations were greater than or equal to 5000 m, 4600 m and 4800 m in meadows, steppes and all grasslands, respectively. Therefore, the causes of actual gross primary production changes varied with elevations, regions and grassland types, and grassland classification management should be considered on the Tibetan Plateau. 相似文献
15.
《Norsk geografisk tidsskrift. Norwegian journal of geography》2012,66(4):312-316
In an old, species-rich hay meadow in Varalds?y in Hardanger, the only known remaining managed site of its kind in West Norway, the moss layer is increasing in thickness in some places. Thick moss is associated with a high cover of monocotyledons, while a low cover of monocotyledons is associated with high numbers of herbs, including vulnerable species, which mainly occur in herb-rich areas. The increase in moss is probably caused by a reduction in both traditional means of moss removal and in sheep trampling and it may represent a potential threat to plant species diversity in traditionally managed hay meadows in the region. In order to increase the area of open, species-rich hay meadows, and thus the potential population sizes for indicator species of traditional management, increased grazing intensity (back to traditional levels) and removal of mosses during haymaking is recommended. The study demonstrates that, for conservation purposes, it is not easy to replicate past conditions unless the details of traditional management practices are known and understood, and these are now passing from general knowledge. 相似文献
16.
In the last decade, there has been increasing interest in climate change, pasture degradation and its driving forces, and innovations in nomadic pastoralism on the Tibetan Plateau. However, little is known of indigenous strategies of adaptation to pasture degradation, which limits the effectiveness of adaptation strategies planned by local government. This paper analyzes nomads’ strategies of adaptation to pasture degradation on the basis of a field survey of three townships of Dalag County in the source regions of the Yangtze and Yellow rivers. Pastures there have evidently degraded, with pastures in Wasai mainly in a state of slight or medium degradation and those in Manzhang and Jianshe in a state of medium or severe degradation. With the degradation of pasture, the grazing time is reduced, which affects the livelihoods of nomads. Although the Four-Package Project has commenced in this region, there is still severe fodder shortage in winter and spring. The traditional hay storage strategy does not work because of pasture degradation, and few nomads establish fenced and artificial pastures. Therefore, nomads have employed other strategies, such as renting pasture, providing supplementary feed, and diversifying their livelihoods. Local strategies taken by nomads can provide valuable insights into ecological restoration and livelihood improvement in the region and suggest changes to means promoted by local government. It is necessary to seek new means that combine the best aspects of nomadic pastoralism with modern stockbreeding technologies to help nomads adapt to pasture degeneration and improve their livelihoods. 相似文献
17.
《Norsk geografisk tidsskrift. Norwegian journal of geography》2012,66(2):65-73
In a sloping hay meadow, situated on phyllitic soils in the fjord region of western Norway, shade from solitary trees in the lower meadow and from high tree cover on the upper slopes has reduced the number of indicators of traditional management, which include vulnerable hay-meadow species. However, the number of additional species, for example, forest species, was higher in shade from solitary trees than in the open; the areas under the crowns may have functioned as refuges for forest species in former days, when wooded hay meadows, comprising small woodlots, solitary trees and shrubs, were widespread in the region. Indicators of traditional management were more frequent in dry plots than in moist plots, but most species in this group occurred in moist plots too. To keep the habitat area for these species as large as possible and at the same time restore the former well-managed tree-layer of the meadow, the removal of large Fraxinus excelsior and Alnus incana specimens from the upper slopes and reduction of the crowns of solitary Taxus baccata and Prunus domesticus on the lower slopes is recommended. 相似文献
18.
基于地理探测器的中国亚热带北界探讨 总被引：1，自引：0，他引：1
暖温带与亚热带的分界线,是自然区划中一条重要的自然界线,它的划分问题曾引起诸多学科学者的争论。由于早期综合自然区划研究多以定性、专家集成方法为主,同时区划目的、使用指标等多有不同,导致不同学者所划分的自然区多存在一定的差异。本文基于空间分异性思想,使用地理探测器定量探测气候指标对中国亚热带北界的影响,选择其中q值较大的指标如日均温≥0℃天数、最冷月1月均温、年降水和湿润指数等作为主导因子并参考植被、土壤数据探讨亚热带北界界线的位置。结果表明：① 地理探测器法可以快速、准确地筛选自然区划的主要气候指标,并确定分界线的准确位置,提高了自然区划研究的技术水平和区划界线的客观性。② 使用地理探测器划分的新界线在研究区西部位于秦岭南坡1000~1600 m的位置,与以往界线相比略偏南;在研究区东部河南东部、安徽北部比以往界线略偏北。在保持自然要素完整性的同时,新界线具有更大的q值,表明新界线可以很好的反映暖温带与北亚热带2个区划带之间的差异,划分结果具有合理性。 相似文献
19.
中国土地利用效益的时空特征研究 总被引：1，自引：0，他引：1
基于经济、社会、生态三维视角构建土地利用效益评价指标体系,运用灰色关联方法测度2004—2014年中国土地利用效益水平,并借助于Arc GIS空间分析技术分析其空间异质性及空间演变格局。从时序特征来看,2004—2014年全国土地利用效益波动性提升。从空间特征来看,中国土地利用效益的空间格局存在差异性,但差异日渐缩小;土地利用效益的增减空间分布不均,随着时间的推移,土地利用效益提升省份增加的幅度越来越大,土地利用效益降低省份的下降幅度越来越小;中国土地利用效益空间集聚特征明显,热点主要分布在内蒙古、辽宁和西藏,冷点主要分布在东南沿海地区;土地利用效益的变化也表现出集聚特征,东南沿海与西部地区为中国土地利用效益变化最强烈的集聚区,其土地利用效益变化呈互逆发展态势;中国土地利用效益变化具有明显的政策导向性。 相似文献
20.
SHEN Zhenxi SUN Wei LI Shaowei ZHANG Haorui FU Gang YU Chengqun ZHANG Guangyu 《资源与生态学报(英文版)》2018,9(5):538-544
Vapor pressure deficit (VPD) is an important parameter in modelling hydrologic cycles and vegetation productivity. Meteorological stations are scarce in remote areas, which often results in imprecise estimations of VPD on the Tibetan Plateau. Moderate Resolution Imaging Spectroradiometer (MODIS) provides evapotranspiration data, which may offer the possibility of scaling up VPD estimations on the Tibetan Plateau. However, no studies thus far have estimated VPD using MODIS evapotranspiration data on the Tibetan Plateau. Therefore, this study used MODIS potential evapotranspiration (PET) to estimate VPD in alpine meadows, alpine steppes, croplands, forests and shrublands for the year, spring, summer, autumn and winter in 2000-2012. A series of root-mean- squared-error (RMSE) and mean-absolute-error (MAE) values were obtained for correlating measured VPD and estimated VPD using MODIS PET data for each listed time period and vegetation type: whole year (0.98-2.15 hPa and 0.68-1.44 hPa), spring (0.95-2.34 hPa and 0.72-1.54 hPa), summer (1.39-2.60 hPa and 0.89-1.96 hPa), autumn (0.78-1.93 hPa and 0.56-1.36 hPa), winter (0.48-1.40 hPa and 0.36-0.98 hPa), alpine steppes (0.48- 1.39 hPa and 0.36-1.00 hPa), alpine meadows (0.58-1.39 hPa and 0.44-0.90 hPa), croplands (1.10-2.55 hPa and 0.82-1.74 hPa), shrublands (0.98-1.90 hPa and 0.78-1.37 hPa), and forests (1.40-2.60 hPa and 0.98-1.96 hPa), respectively. Therefore, MODIS PET may be used to estimate VPD, and better results may be obtained if future studies incorporate vegetation types and seasons when the VPD data are estimated using MODIS PET on the Tibetan Plateau. 相似文献