综合地理数据与MODIS物候特征的区域土地覆盖制图(英文)     

蔡红艳  张树文  卜坤  杨久春  常丽萍 《地理学报(英文版)》2011,21(4):705-718

The study developed a feasible method for large-area land cover mapping with combination of geographical data and phenological characteristics, taking Northeast China (NEC) as the study area. First, with the monthly average of precipitation and temperature datasets, the spatial clustering method was used to divide the NEC into four ecoclimate regions. For each ecoclimate region, geographical variables (annual mean precipitation and temperature, elevation, slope and aspect) were combined with phenological variables derived from the moderate resolution imaging spectroradiometer (MODIS) data (enhanced vegetation index (EVI) and land surface water index (LSWI)), which were taken as input variables of land cover classification. Decision Tree (DT) classifiers were then performed to produce land cover maps for each region. Finally, four resultant land cover maps were mosaicked for the entire NEC (NEC_MODIS), and the land use and land cover data of NEC (NEC_LULC) interpreted from Landsat-TM images was used to evaluate the NEC_MODIS and MODIS land cover product (MODIS_IGBP) in terms of areal and spatial agreement. The results showed that the phenological information derived from EVI and LSWI time series well discriminated land cover classes in NEC, and the overall accuracy was significantly improved by 5.29% with addition of geographical variables. Compared with NEC_LULC for seven aggregation classes, the area errors of NEC_MODIS were much smaller and more stable than that of MODIS_IGBP for most of classes, and the wall-to-wall spatial comparisons at pixel level indicated that NEC_MODIS agreed with NEC_LULC for 71.26% of the NEC, whereas only 62.16% for MODIS_IGBP. The good performance of NEC_MODIS demonstrates that the methodology developed in the study has great potential for timely and detailed land cover mapping in temperate and boreal regions.  相似文献   

Monitoring vegetation dynamics with medium resolution MODIS-EVI time series at sub-regional scale in southern Africa     

《International Journal of Applied Earth Observation and Geoinformation》2015

Currently there is a lack of knowledge on spatio-temporal patterns of land surface dynamics at medium spatial scale in southern Africa, even though this information is essential for better understanding of ecosystem response to climatic variability and human-induced land transformations. In this study, we analysed vegetation dynamics across a large area in southern Africa using the 14-years (2000–2013) of medium spatial resolution (250 m) MODIS-EVI time-series data. Specifically, we investigated temporal changes in the time series of key phenometrics including overall greenness, peak and timing of annual greenness over the monitoring period and study region. In order to specifically capture spatial and per pixel vegetation changes over time, we calculated trends in these phenometrics using a robust trend analysis method. The results showed that interannual vegetation dynamics followed precipitation patterns with clearly differentiated seasonality. The earliest peak greenness during 2000–2013 occurred at the end of January in the year 2000 and the latest peak greenness was observed at the mid of March in 2012. Specifically spatial patterns of long-term vegetation trends allowed mapping areas of (i) decrease or increase in overall greenness, (ii) decrease or increase of peak greenness, and (iii) shifts in timing of occurrence of peak greenness over the 14-year monitoring period. The observed vegetation decline in the study area was mainly attributed to human-induced factors. The obtained information is useful to guide selection of field sites for detailed vegetation studies and land rehabilitation interventions and serve as an input for a range of land surface models.  相似文献   

全球变暖对淡水湖泊浮游植物影响研究进展   总被引：9，自引：6，他引：3  

邓建明  秦伯强 《湖泊科学》2015,27(1):1-10

全球变暖对湖泊生态系统的影响已经成为近年来湖沼学领域的研究热点.本文首先列举了目前研究全球变暖对淡水湖泊浮游植物影响的常用方法:监测数据分析、时空转换、遥感信息提取、控制实验、模型预测和古湖沼学技术等.研究结果表明气候变暖导致的气温升高、湖泊热力分层提前破坏以及无冰期提前等因素可导致春季物候提前;在全球变暖大背景下浮游植物群落结构正朝着蓝藻占优的方向发展,但是不同地区以及不同物种对全球变暖的响应不一致.在营养盐充足的湖泊中,由于全球变暖延长了浮游植物生长季节等,从而能提高浮游植物初级生产力;但在贫营养湖泊中,浮游植物初级生产力与变暖趋势甚至可能呈负相关.由于生态系统往往是多因子的共同作用,这也使得全球变暖对浮游植物群落的影响效应复杂化,区分各因子的净影响份额是目前研究的一个难点;全球变暖引起的风场改变会促进浅水湖泊中营养盐从底泥的释放,同时也会增加水体中悬浮物的浓度而影响水下光场,因此开展气候变化对再悬浮及浮游植物群落结构的影响可能是将来研究的一个切入点.  相似文献   

Spatiotemporal characteristics of Qinghai Lake ice phenology between 2000 and 2016     

Qi  Miaomiao  Yao  Xiaojun  Li  Xiaofeng  Duan  Hongyu  Gao  Yongpeng  Liu  Juan 《地理学报(英文版)》2019,29(1):115-130

Journal of Geographical Sciences - Lake ice phenology is considered a sensitive indicator of regional climate change. We utilized time series information of this kind extracted from a series of...  相似文献   

Greenness Index from Phenocams Performs Well in Linking Climatic Factors and Monitoring Grass Phenology in a Temperate Prairie Ecosystem     

ZHOU Yuke 《资源与生态学报(英文版)》2019,10(5):481-493

Near-surface remote sensing (e.g., digital cameras) has played an important role in capturing plant phenological metrics at either a focal or landscape scale. Exploring the relationship of the digital image-based greenness index (e.g., Gcc, green chromatic coordinate) with that derived from satellites is critical for land surface process research. Moreover, our understanding of how well Gcc time series associate with environmental variables at field stations in North American prairies remains limited. This paper investigated the response of grass Gcc to daily environmental factors in 2018, such as soil moisture (temperature), air temperature, and solar radiation. Thereafter, using a derivative-based phenology extraction method, we evaluated the correspondence between key phenological events (mainly including start, end and length of growing season, and date with maximum greenness value) derived from Gcc, MODIS and VIIRS NDVI (EVI) for the period 2015-2018. The results showed that daily Gcc was in good agreement with ground-level environmental variables. Additionally, multivariate regression analysis identified that the grass growth in the study area was mainly affected by soil temperature and solar radiation, but not by air temperature. High frequency Gcc time series can respond immediately to precipitation events. In the same year, the phenological metrics retrieved from digital cameras and multiple satellites are similar, with spring phenology having a larger relative difference. There are distinct divergences between changing rates in the greenup and senescence stages. Gcc also shows a close relationship with growing degree days (GDD) derived from air temperature. This study evaluated the performance of a digital camera for monitoring vegetation phenological metrics and related climatic factors. This research will enable multiscale modeling of plant phenology and grassland resource management of temperate prairie ecosystems.  相似文献   

The effect of terrain factors on rice production: A case study in Hunan Province     

Wang  Chenzhi  Zhang  Zhao  Zhang  Jing  Tao  Fulu  Chen  Yi  Ding  Hu 《地理学报(英文版)》2019,29(2):287-305

Journal of Geographical Sciences - Rice (Oryza sativa L.) is the most important staple crop of China, and its production is related to both natural condition and human activities. It is fundamental...  相似文献   

黑河中游花棒的开花特性与繁育系统研究   总被引：3，自引：1，他引：2  

潘成臣  刘林德  侯月利  张莉  王艳杰  王艳华  王丽娟  赵雪 《中国沙漠》2010,30(5):1099-1103

 2009年5—10月在黑河流域中游定位观测了花棒的开花特性，运用人工授粉和套袋试验等方法测定了花棒的繁育系统。结果表明,花棒单朵花的花期为2～5 d。花粉属“非淀粉型”，寿命4～8 h。访花者有10余种，以膜翅目昆虫为主。授粉实验结果显示其不存在无融合生殖，自交亲和，自然条件下，虫媒在传粉过程中起决定性的作用，表明花棒的繁育系统为混合交配系统。  相似文献   

A dynamic relationship between the leaf phenology and rainfall regimes of Hawaiian tropical ecosystems: A remote sensing approach     

Sunyurp Park 《Singapore journal of tropical geography》2010,31(3):371-383

Hypertemporal MODIS time series data provide a unique opportunity to investigate a dynamic relationship between leaf phenology and the climatic pattern of diverse, cloud‐prone Hawaiian ecosystems. Harmonic analysis summarized the complex greenness signals of Hawaiian tropical ecosystems into two main phenological wave forms – a moisture‐limited and a light‐limited type. Greenness maximums occurred during the wet season in dry and mesic ecosystems, and during the dry season in wet forests. The magnitude and periodicity of greenness fluctuations were also rainfall‐dependent. The annual greenness amplitude increased with increasing mean annual precipitation (MAP) in dry and mesic ecosystems. In wetter environments where MAP was greater than 3000 mm, however, annual greenness amplitude decreased with MAP. Annual greenness periodicity was stronger in drylands than in wet forests, and it weakened as annual precipitation increased. This result shows that rainfall is less important as a limiting factor in wet forests than it is in drylands. Therefore, leaf phenology is not governed by rainfall seasonality as forest wetness increases in the region.  相似文献   

Spatio-Temporal Distribution of Algal and Animal Communities in a Posidonia oceanica Meadow     

Lucia MaZzella  Maria Beatrice Scipione  Maria Cristina Buia 《Marine Ecology》1989,10(2):107-129

Abstract. Investigations were carried out in a Posidonia oceanica meadow at Ischia (Gulf of Naples) along a depth gradient from 1 to 32 m in November 1979 and May 1981.
In these two months, different discontinuities were found at the sampling stations (1, 5, 10, 20, 30 m) at 10 m for leaf features, between 1 and 5 m for the algal community and the vagile fauna. The leaf features (length, surface, and biomass) along the transects show a delay in leaf production toward the deeper stations, below the thermocline.
The algal community shows in both seasons and in all stations a persistence of an encrusting layer, mostly represented by Corallinaceae and the brown alga Myrionema orbiculare , while at the shallowest station (1 m) the community is characterized by a more developed upright layer.
The vagile fauna of the leaf stratum, mostly represented by Polychaeta, Mollusca , and Crustacea (Peracarida and Decapoda) , shows a consistent zonation in both seasons along the transect. A superficial community at I m, characterized by a low number of species and individuals and specialized for high environmental energy levels, and a deeper community, persistent in time and more strictly related to the Posidonia oceanica meadows, are identified.
The influence of environmental factors and the importance of meadow structure for the zonation of the algal and animal communities are discussed.  相似文献   

Seasonality and Reproductive Phenology of Algae Inhabiting Littoral Pools in the Western Mediterranean     

Lisandro  Benedetti-Cecchi Francesco  Cinelli 《Marine Ecology》1993,14(2):147-157

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