近50年中国温带季风区植物花期春季霜冻风险变化   总被引：7，自引：2，他引：5  

戴君虎  王焕炯  葛全胜 《地理学报》2013,68(5):593-601

中国温带季风区是我国重要的农业区,春季霜冻常对该地区的植物造成严重的损害。本文利用“中国物候观测网”12 个站点的物候观测数据和对应站点气象资料,应用物候模型方法,对1963-2009 年各站点的霜冻频次和多种木本植物的始花期进行了分析,并对植物在花期的霜冻风险进行了评估。结果表明,1963-2009 年,研究区内东北地区和华北地区的始花期分别以-1.52 天/10a (P < 0.01) 和-2.22 天/10a (P < 0.01) 的速度提前。在同一时段,研究区春季霜冻日数显著减少,终霜冻日显著提前。综合考虑花期和霜冻频次的变化,霜冻风险指数,即木本植物花期受到霜冻的物种数占调查总数的百分比,在东北地区以-0.37%/10a 的速度降低(不显著);而在华北地区,霜冻风险指数则以-1.80%/10a 的速度显著下降(P < 0.01)。这表明过去半个世纪研究区植物花期霜冻风险在降低,且存在显著的区域差异。该结论可为农业和森林管理者制订应对春季霜冻害的决策提供参考。  相似文献   

基于HJ-1A/B CCD数据的河南省平原绿化分析     

刁慧娟  ;王正兴  ;于信芳 《地球信息科学学报》2014,16(5):824-832

平原绿化在未来农林发展中具有重要地位。本文利用环境卫星(HJ-1 A/B)多时相数据,选择河南省6月冬小麦收割后的CCD数据,直接去除第二季作物,并利用4月份第一季作物播种前的CCD数据,剔除了一季作物,以及[(NDVI_4月≥0.22)与(NDVI_6月≥0.35)]提取平原绿化的信息,其与26个主要城市城区绿化信息进行的相关分析达到显著水平(R²=0.9166)。因此,该区的平原绿化解译效果好,而南部信阳市以一季水稻为主的地区及“水稻-冬小麦”过渡区,解译效果较差。除信阳外,由HJ-1卫星解译的河南平原绿化总面积6909.8 km²,占2010年河南省森林面积20.53%。  相似文献   

Spatial-temporal variations of lake ice phenology in the Hoh Xil region from 2000 to 2011     

Xiaojun Yao  Long Li  Jun Zhao  Meiping Sun  Jing Li  Peng Gong  Lina An 《地理学报(英文版)》2016,26(1):70-82

Lake ice phenology, i.e. the timing of freeze-up and break-up and the duration of the ice cover, is regarded as an important indicator of changes in regional climate. Based on the boundary data of lakes, some moderate-high resolution remote sensing datasets including MODIS and Landsat TM/ETM+ images and the meteorological data, the spatial-temporal variations of lake ice phenology in the Hoh Xil region during the period 2000–2011 were analyzed by using RS and GIS technology. And the factors affecting the lake ice phenology were also identified. Some conclusions can be drawn as follows. (1) The time of freeze-up start (FUS) and freeze-up end (FUE) of lake ice appeared in the late October–early November, mid-November–early December, respectively. The duration of lake ice freeze-up was about half a month. The time of break-up start (BUS) and break-up end (BUE) of lake ice were relatively dispersed, and appeared in the early February–early June, early May–early June, respectively. The average ice duration (ID) and the complete ice duration (CID) of lakes were 196 days and 181 days, respectively. (2) The phenology of lake ice in the Hoh Xil region changed dramatically in the last 10 years. Specifically, the FUS and FUE time of lake ice showed an increasingly delaying trend. In contrast, the BUS and BUE time of lake ice presented an advance. This led to the reduction of the ID and CID of lake. The average rates of ID and CID were–2.21 d/a and–1.91 d/a, respectively. (3) The variations of phenology and evolution of lake ice were a result of local and climatic factors. The temperature, lake area, salinity and shape of the shoreline were the main factors affecting the phenology of lake ice. However, the other factors such as the thermal capacity and the geological structure of lake should not be ignored as well. (4) The spatial process of lake ice freeze-up was contrary to its break-up process. The type of lake ice extending from one side of lakeshore to the opposite side was the most in the Hoh Xil region.  相似文献   

融合Landsat 8与Sentinel-2数据的红树林物候信息提取与分类     

薛朝辉  钱思羽 《遥感学报》2022,26(6):1121-1142

科学准确地监测红树林是保护海陆过渡性生态系统的基础和前提,但红树林分布于潮间带,难以进行大规模人工监测。遥感技术能够对红树林进行长时间、大面积监测,但已有研究尚存不足。一方面,红树林分布于热带、亚热带区域,受到天气条件限制难以获得长时间覆盖的有效光学遥感数据;另一方面,红树林极易与其他陆生植被混淆,仅利用多波段数据的光谱信息难以精确识别。本文以恒河三角洲孙德尔本斯地区为例,基于谷歌地球引擎GEE（Google Earth Engine）获取2016年全年的Landsat 8 OLI和Sentinel-2 MSI数据,利用物候信息进行红树林提取研究。首先,基于最小二乘回归构建两个传感器在相同指数之间的关系,重建时间序列数据,之后根据可分性判据选取增强型植被指数EVI（Enhanced Vegetation Index）和陆地表面水分指数LSWI（Land Surface Water Index）。其次,对两个指数的时间序列数据进行Savitzky-Golay滤波处理,并分别提取生长期始期等13种物候信息。最后,将两个指数的物候信息进行特征级联,采用随机森林RF（Random Forest）方法进行分类,提取研究区红树林范围。实验结果表明：Landsat 8 OLI和Sentinel-2 MSI数据融合可有效提升时间序列质量,与基于单一传感器数据的分类结果相比,总体精度提高1.58%;物候信息可以显著增强红树林与其他植被的可分性,与直接使用时间序列数据的分类结果相比,总体精度提高1.92%;同时考虑EVI和LSWI指数可极大地提升分类效果,与采用单一指数相比,总体精度分别提高14.11%和9.69%。因此,本文通过数据融合、物候信息提取和指数特征级联可以更好地提取红树林,总体精度达到91.02%,Kappa系数为0.892。研究验证了物候信息在红树林遥感监测中的应用潜力,提出的方法对科学准确地监测全球或区域红树林具有一定参考价值。  相似文献   

Analysis of differences in vegetation phenology cycle of abandoned farmland,using harmonic analysis of time-series vegetation indices data: the case of Gwangyang City,South Korea     

Sunggyu Lee  Soyoun Kim 《地理信息系统科学与遥感》2020,57(3):338-351

ABSTRACT

Globally, countries have experienced substantial increases in farmland abandonment. Although vegetation phenology is a key factor for the classification of land use, understanding of the phenological change of abandoned farmland is lacking. Using harmonic analysis of NDVI and NDWI extracted from Landsat imagery, this study investigates the distinctive phenological characteristics of abandoned farmland, which contrasts with that of three other agricultural types (paddy, agricultural field, orchard) in the study site of Gwangyang City in Jeollanam Province, South Korea. The results suggest that abandoned farmland has higher overall greenness coverage and overall water content in vegetation than the other uses. In terms of both indices, abandoned farmlands changed with relatively less fluctuation than those of other uses, suggesting the existence of constant and unmanaged vegetation from ecological succession, which differs from crop fields that undergo cultivation procedures. The significant harmonic components differed among agricultural types and vegetation indices. In paddy, NDVI was explained with multiple, higher-order harmonic components, while in other types only first-order components met the 5% statistical significance level. With NDWI, land types were more clearly discernible, because of the different cultivation procedures involving water: wet-field method (paddy), dryland farming (orchard, agricultural field), and no cultivation (abandoned farmland). The analysis confirms that harmonic analysis could be useful in discerning abandoned farmland among areas of active agricultural use and shows that the statistical significance of harmonic terms can be employed as indicators of different agricultural types. The observed pattern of the geographic distribution of abandoned farmland has policy implications for the promotion of sustainable reuse of marginal farmland.  相似文献   

Land surface phenology from VEGETATION and PROBA-V data. Assessment over deciduous forests     

《International Journal of Applied Earth Observation and Geoinformation》2020

Land surface phenology has been widely retrieved although no consensus exists on the optimal satellite dataset and the method to extract phenology metrics. This study is the first comprehensive comparison of vegetation variables and methods to retrieve land surface phenology for 1999–2017 time series of Copernicus Global Land products derived from SPOT-VEGETATION and PROBA-V data. We investigated the sensitivity of phenology to (I) the input vegetation variable: normalized difference vegetation index (NDVI), leaf area index (LAI), fraction of absorbed photosynthetically active radiation (FAPAR), and fraction of vegetation cover (FCOVER); (II) the smoothing and gap filling method for deriving seasonal trajectories; and (III) the method to extract phenological metrics: thresholds based on a percentile of the annual amplitude of the vegetation variable, autoregressive moving averages, logistic function fitting, and first derivative methods. We validated the derived satellite phenological metrics (start of the season (SoS) and end of the season (EoS)) using available ground observations of Betula pendula, B. alleghaniensis, Acer rubrum, Fagus grandifolia, and Quercus rubra in Europe (Pan-European PEP725 network) and the USA (National Phenology Network, USA-NPN). The threshold-based method applied to the smoothed and gap-filled LAI V2 time series agreed best with the ground phenology, with root mean square errors of ˜10 d and ˜25 d for the timing of SoS and EoS respectively. This research is expected to contribute for the operational retrieval of land surface phenology within the Copernicus Global Land Service.  相似文献   

基于微博大数据的2010～2018年中国桃花观赏日期时空格局研究     

刘俊  王胜宏  金朦朦  李宁馨 《地理科学》2019,39(9):1446-1454

从新浪微博中检索到2 952 828条有关桃花观赏活动的微博,按照数据筛选、时空匹配、检验校准的流程,筛选出843 034条表述“桃花开了”的可采信微博,从中提取并构建了2010~2018年全国293个城市的桃花观赏日期数据集。之后使用物候站点观测数据、气温数据和物候模型模拟数据验证了桃花观赏日期数据集,得出基于微博大数据提取的中国桃花观赏日期数据集符合物候站点观测的桃花花期变化规律,符合桃花开花前气温升高则花期提前的基本规律,并与物候模型模拟的桃花花期基本一致,可以作为物候站点观测数据的重要补充。基于提取出的桃花观赏日期数据集,进一步分析了中国桃花观赏日期的时空格局,结果表明,纬度每升高1°,桃花观赏日期推迟1.78 d,其中北亚热带桃花观赏日期对纬度变化最为敏感,纬度每升高1°,桃花观赏日期推迟2.56 d。过去9 a全国大部分城市的桃花观赏日期提前。  相似文献   

草型湖泊总悬浮物浓度和浊度遥感监测   总被引：1，自引：0，他引：1  

曹引  冶运涛  赵红莉  蒋云钟  王浩 《遥感学报》2019,23(6):1253-1268

草型湖泊水质遥感监测中水生植物会造成“水体—水生植物”混合像元问题，针对因混合像元导致草型湖泊水生植物覆盖区域水质难以直接利用遥感监测的问题，本文以草型湖泊微山湖为研究对象，提出定性和定量相结合的总悬浮物浓度和浊度分区监测方法，实现微山湖水体总悬浮物浓度和浊度的时空变化监测。基于获取的2014年7月—2015年6月覆盖微山湖的多期高分一号（GF-1） WFV和HJ-1A/1B CCD影像，利用归一化水体指数将微山湖区分为水生植物覆盖区和水体区。针对水生植物覆盖区，利用时序MODIS NDVI数据获取微山湖主要水生植物的时谱曲线，识别不同水生植物的物候特征；基于不同物候期内的水生植物对总悬浮物浓度和浊度的指示作用，对微山湖水生植物覆盖区水体总悬浮物浓度和浊度进行定性监测。针对水体区，分别构建水体总悬浮物浓度和浊度的单波段/波段比值模型和偏最小二乘模型，定量反演微山湖水体区总悬浮物浓度和浊度。研究结果表明，微山湖中水生植物以光叶眼子菜、穗花狐尾藻和菹草等沉水植物为主，其中光叶眼子菜/穗花狐尾藻和菹草的空间分布和物候特征存在明显差异，不同水生植物在不同物候期内对水质具有不同的指示作用；微山湖水体总悬浮物浓度和浊度具有显著的空间变异性，基于定性和定量相结合的方法可以有效监测微山湖水体总悬浮物浓度和浊度的时空变化规律。本文提出的定性和定量相结合的监测方法为草型湖泊水质监测的业务化应用提供了新思路。  相似文献   

Modelling the interaction of climate,forest ecosystem,and hydrology to estimate catchment dissolved organic carbon export     

Kyongho Son  Laurence Lin  Lawrence Band  Emmet M. Owens 《水文研究》2019,33(10):1448-1464

The potential for increased loads of dissolved organic carbon (DOC) in streams and rivers is a concern for regulating the water quality in water supply watersheds. With increasing hydroclimatic variability related to global warming and shifts in forest ecosystem community and structure, understanding and predicting the magnitude and variability of watershed supply and transport of DOC over multiple time scales have become important research and management goals. In this study, we use a distributed process‐based ecohydrological model (Regional Hydro‐Ecological Simulation System [RHESSys]) to explore controls and predict streamflow DOC loads in Biscuit Brook. Biscuit Brook is a forested headwater catchment of the Neversink Reservoir, part of the New York City water supply system in the Catskill Mountains. Three different model structures of RHESSys were proposed to explore and evaluate hypotheses addressing how vegetation phenology and hydrologic connectivity between deep groundwater and riparian zones influence streamflow and DOC loads. Model results showed that incorporating dynamic phenology improved model agreement with measured streamflow in spring, summer, and fall and fall DOC concentration, compared with a static phenology. Additionally, the connectivity of deep groundwater flux through riparian zones with dynamic phenology improved streamflow and DOC flux in low flow conditions. Therefore, this study suggests the importance of inter‐annual vegetation phenology and the connectivity of deep groundwater drainage through riparian zones in the hydrology and stream DOC loading in this forested watershed and the ability of process‐based ecohydrological models to simulate these dynamics. The advantage of a process‐based modelling approach is specifically seen in the sensitivity to forest ecosystem dynamics and the interactions of hydroclimate variability with ecosystem processes controlling the supply and distribution of DOC. These models will be useful to evaluate different forest management approaches toward mitigating water quality concerns.  相似文献   

First insights on spatial and temporal distribution patterns of humpback whales in the breeding ground at Sainte Marie Channel,Madagascar     

L Trudelle  J-B Charrassin  A Saloma  S Pous  A Kretzschmar  O Adam 《African Journal of Marine Science》2018,40(1):75-86

The Sainte Marie Channel on the northeast coast of Madagascar is an important breeding ground for humpback whales; the first observation of birth was documented there, yet it has never been investigated for phenology and habitat use of humpback whales. The present study was aimed at examining temporal and spatial distribution patterns and the encounter rate of different social groups of humpback whales during the breeding season. We used a large set of opportunistic sightings data collected from whale-watching boats. A total of 3 247 sightings were collected during 897 whale-watching trips conducted between June and September from 2009 to 2013. Our study complements previous information on the seasonal presence of humpback whale social groups by demonstrating a persistent and well-structured temporal pattern in the succession of the different groups. Over the different years of the study period, groups without calves consistently dominated the first 30 days of the breeding season, followed by an increase in groups with calves. Interannual differences were observed in the encounter rates, with significantly higher global encounter rates in 2009, 2011 and 2013 (2.2, 2.3 and 2.3 sightings h^–1, respectively), and likewise for the mean encounter rates for groups with calves. In contrast, the encounter rate of groups without calves was similar over the study period. Although our study area exhibits a narrow configuration and poorly contrasting physiographic features due to its restricted spatial extent, we report a spatially segregated pattern of humpback whale social groups in the Sainte Marie Channel. A general linear model showed that groups with calves were influenced by water depth and distance from shore, being observed mostly in shallow waters (to 20 m depth) and close to the coastline (6 km). Our findings will be useful for the development of strategic sustained management plans by providing baseline information on humpback whale distribution at an important but poorly documented breeding site.  相似文献