A record of Lateglacial/Holocene environmental change from a high‐elevation site in the Intermountain West,USA     

Andrea Brunelle  Thomas A. Minckley  Elliott Lips  Paul Burnett 《第四纪科学杂志》2013,28(1):103-112

Records of past vegetation and fire history can be complicated by changes in the depositional environment of a sampling location. However, these changes can alternatively be used as a measure of climate variability. Our study site, ca. 18.0 cal. ka BP record from Little Brooklyn Lake, Wyoming, located near the crest of the Snowy Range, records three moisture states. Initially, the lake was likely a glacier‐fed pond indicated by the presence of Pediastrum algae colonies. Around 13.0 cal. ka BP this pond transitioned to a meadow environment, suggested by the loss of Pediastrum algae colonies and slow sedimentation rates. Meadow conditions were maintained until ca. 5.0 cal. ka BP when Pediastrum algae colony abundance increased,indicating the formation of a shallow lake. From 18.0 to ca. 5.0 cal. ka BP, the pollen record is suggestive of alpine vegetation conditions with relatively high spruce and herbaceous taxa. Low charcoal influx also characterizes the period between 18.0 and 5.0 cal. ka BP. After 5.0 cal. ka BP, the coincidence of the formation of shallow lake and pollen data, indicating a shift to a spruce and fir forest, suggests an increase in effective moisture. Fire remained rare in this basin over the entire record, however, once the lake established sedimentation rates and charcoal influx increased. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Subsurface lateral flow generation in aspen and conifer‐dominated hillslopes of a first order catchment in northern Utah     

Amy R. Burke  Tamao Kasahara 《水文研究》2011,25(9):1407-1417

Mountain headwater catchments in the semi‐arid Intermountain West are important sources of surface water because these high elevations receive more precipitation than neighboring lowlands. This study examined subsurface runoff in two hillslopes, one aspen dominated, the other conifer dominated, adjacent to a first order stream in snow‐driven northern Utah. Snow accumulation, soil moisture, trenchflow and streamflow were examined in hillslopes and their adjacent stream. Snow water equivalents (SWEs) were greater under aspen stands compared to conifer, the difference increasing with higher annual precipitation. Semi‐variograms of shallow spatial soil moisture patterns and transects of continuous soil moisture showed no increase in soil moisture downslope, suggesting the absence of subsurface flow in shallow (～12 cm) soil layers of either vegetation type. However, a clear threshold relationship between soil moisture and streamflow indicated hillslope–stream connectivity, deeper within the soil profile. Subsurface flow was detected at ～50 cm depth, which was sustained for longer in the conifer hillslope. Soil profiles under the two vegetation types varied, with deep aspen soils having greater water storage capacity than shallow rocky conifer soils. Though SWEs were less under the conifers, the soil profile had less water storage capacity and produced more subsurface lateral flow during the spring snowmelt. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

叶绿素荧光遥感在陆地生态系统碳循环和陆气相互作用中的应用研究进展          下载免费PDF全文

邱博  郭维栋 《大气科学学报》2022,45(6):801-814

陆地生态系统通过植被光合作用可以吸收约30％的人为碳排放,在全球碳循环、减缓大气二氧化碳浓度上升等方面具有重要作用。最近10年发展起来的日光诱导叶绿素荧光遥感技术,可以监测植被实际光合作用,为全球陆地生态系统碳循环的研究提供了新的思路和方法。本文回顾了叶绿素荧光遥感产品发展及其在陆地生态系统碳循环和陆气相互作用中的应用研究进展,特别是在全球植被总初级生产力估算和陆地生态系统碳循环模型发展方面的进展,并进一步讨论了该领域研究面临的挑战和未来的发展方向。  相似文献   

Impacts of Irrigation and Vegetation Growth on Summer Rainfall in the Taklimakan Desert     

Dongze XU  Yanluan LIN 《大气科学进展》2021,38(11):1863-1872

In recent decades, a greening tendency due to increased vegetation has been noted around the Taklimakan Desert(TD), but the impact of such a change on the local hydrological cycle remains uncertain. Here, we investigate the response of the local hydrological cycle and atmospheric circulation to a green TD in summer using a pair of global climate model(Community Earth System Model version 1.2.1) simulations. With enough irrigation to support vegetation growth in the TD, the modeling suggests first, that significant increases in local precipitation are attributed to enhanced local recycling of water, and second, that there is a corresponding decrease of local surface temperatures. On the other hand, irrigation and vegetation growth in this low-lying desert have negligible impacts on the large-scale circulation and thus the moisture convergence for enhanced precipitation. It is also found that the green TD can only be sustained by a large amount of irrigation water supply since only about one-third of the deployed water can be "recycled " locally. Considering this,devising a way to encapsulate the irrigated water within the desert to ensure more efficient water recycling is key for maintaining a sustainable, greening TD.  相似文献   

泛北极地区植被数据集与制图：回顾与展望     

薛守业  徐海燕  甘子鹏  梁冰妍  种碧莹  王莉  张博  李小明  李莉莎  毛楠  刘桂民  吴晓东 《地球信息科学学报》2022,24(3):421-436

泛北极地区位于北半球高纬度地区,主要属于低温限制型生态系统,因而泛北极地区植被对全球变暖敏感。要明确泛北极地区陆地生态系统对全球变暖响应过程和机理,就需要高精度的植被类型分类数据作为基础资料。但是,目前泛北极地区植被数据的结果还不完善。为更好地认识泛北极地区植被类型分类的现状、发展历史和未来研究方向,本文综述了泛北极地区植被类型制图的数据来源、植被类型划分方法和植被类型制图研究方法。总体而言,泛北极地区的植被调查从20世纪20年代就陆续开展,目前部分区域尺度上的地表覆盖类型的结果,但具体的植被类型制图工作还存在一系列难题。主要原因包括植被野外调查实测数据较少和分布不均、植被类型分类标准不一、苔原植被群落的异质性大、制图技术和分类算法优化困难等。因此,在下一步泛北极植被类型制图工作中,需要制定标准化分类策略,规范数据获取及数据库的整理工作,并发展新的制图方法,从而促进植被类型制图研究工作。  相似文献   

1990—2020年中国能源开采和加工场地多源数据综合制图与时空变化分析     

郭长庆  迟文峰  匡文慧  窦银银  傅舒婧  雷梅 《地球信息科学学报》2022,24(1):127-140

由于当前缺乏有效的能源开采和加工场地精细化遥感探测方法和高精度的数据产品,全国尺度的能源开采和加工场地时空分布规律的认识仍显不足。本研究基于高分辨率遥感影像、土地利用/覆盖数据、网络爬虫数据、OSM地图数据和环境专题数据等信息,发展了基于多源数据融合和专家知识参与获取的能源开采和加工场地遥感识别和精细化制图的技术方法,研发了1990、2000、2010和2020年共4期的中国能源开采和加工场地分布数据产品及2010—2020年场地植被恢复信息数据产品,作为中国土地利用/覆盖变化数据的组成部分（CLUD-Mining）。CLUD-Mining具有较高的质量和可靠性,数据产品平均精度为91.75%;中国能源开采和加工场地开发建设的面积呈现先增长后减少的发展趋势,1990—2010年,面积增长速度从55.22 km²/a上升到95.51 km²/a,而2010—2020年呈现负增长,平均每年减少27.28 km²;此外,2010—2020年场地植被恢复面积达746.76 km²,主要集中在华北区和西南区;中国能源开采和加工场地分布格局逐渐由东部地区向西部地区转移。本研究对提升中国能源开采和加工场地时空分布特征的认识具有重要意义,可为场地污染治理和生态修复提供重要的数据基础。  相似文献   

Literature analysis of Dendrolimus disasters based on remote sensing monitoring     

WANG Mingchang  ZHOU Yuyang  LI Mingjie  JI Xue  LIU Ziwei 《世界地质(英文版)》2022,25(1):49-59

Due to global climate change,Dendrolimus pests and diseases seriously threaten the protec-tion of forestry plants and the safety of crops all over the world.This paper aims to discuss the research results and frontier progress of Dendrolimus disasters based on remote sensing monitoring,trying to find the occurrence characteristics of pests.In this paper,bibliometric methods and CiteSpace knowledge graphs were used to analyze the publication trend,highly cited documents,key research institutions,and high-frequency keywords of the extracted documents in the Web of Science(WOS)database.The following conclusions are drawn:(1)The amount of research in WOS is on the rise,but it has declined in recent years.The countries with strong influence in national cooperation are mainly the United States and China.(2)The United States Department of Agriculture-Agricultural Research Service(USDA ARS)and the Chinese Academy of Sciences have published a lot.This paper reviewed the research progress of high-frequency institutions.(3)The key research topics focus on remote sensing,agriculture,and environmental sciences.Besides,the research hotspots include remote sensing monitoring,climate change,spectral reflectance,vegetation index,and precision agriculture.Finally,we put forward the current challenges and development trends of remote sensing pest monitoring.This paper can provide a reference for the research on remote sensing monitoring of Dendrolimus disasters in the future.  相似文献   

大气散射对采用归一化植被指数进行赤潮遥感监测的影响研究   总被引：3，自引：0，他引：3  

唐军武  丁静  王其茂  马超飞 《海洋学报》2004,26(3):136-142

1　引言近年来赤潮灾害在我国海域频繁发生,对沿海环境、经济和人民生产生活都造成一定的影响,因此对赤潮进行实时监测并业务化运行就显得尤其重要.赤潮遥感监测是目前常用手段之一,在实践中取得了一定的效果,但到目前为止还没有一种成熟的算法能用于业务化监测赤潮的发生.很多研究人员借鉴归一化植被指数(NDVI)阈值法、海表温度(SST)异常等来判断赤潮的发生,但归一化植被指数阈值法经常会出现误判或无法区分正常与异常水体的情况.该阈值范围由先验知识得到,没有定量的理论依据.归一化植被指数是陆地遥感中用以表征地表植物覆盖程度和健…  相似文献   

Vegetation change and surface elevation dynamics in estuarine wetlands of southeast Australia   总被引：1，自引：1，他引：1  

K. Rogers  K.M. Wilton  N. Saintilan   《Estuarine, Coastal and Shelf Science》2006,66(3-4):559-569

Vertical accretion and surface elevation trends were studied in mangrove and saltmarsh wetlands in southeast Australia. A total of 69 surface elevation tables, each associated with three feldspar marker horizons, was deployed in 10 wetlands across 7 estuaries, and monitored for three years. Saltmarsh and mangrove vegetation distributions were mapped for the same estuaries, and elevation characteristics of the wetlands were modelled. Rates of vertical accretion were found to correlate with tidal range. No relationship was found between rates of vertical accretion and surface elevation increase. A positive relationship was demonstrated between contemporary rates of saltmarsh surface elevation change and longer-term rates of mangrove encroachment into saltmarsh. We conclude that landward mangrove encroachment may be facilitated by local factors contributing to saltmarsh compaction during drought conditions.  相似文献   

江苏沿海互花米草盐沼动态变化及影响因素研究   总被引：14，自引：0，他引：14  

刘永学  张忍顺  李满春 《海洋地质前沿》2004,20(2):18-21

收集了1988-2001年12个时相的江苏盐城幅卫星影像，提取了双洋河口至梁垛：河闸之间的互花米草盐沼；统计了不同时期的分布信息。分析表明：①互花米草盐沼在江苏扩张非常迅速，到2001年7月互花米草盐沼分布面积达129．28km^2，从射阳河口至梁垛河闸之间的潮问中上带泥滩大部分已被互花米草盐沼所覆盖；②由于生态位的影响，互花米草盐沼沿平行于海岸线方向的扩张速度快于垂直于海岸线方向的扩张速度；③依据野外调查和卫星影像分析，互花米草盐沼扩张可分为3个阶段：立地阶段、快速扩张期及成熟期。此外，还对互花米草盐的影响因素进行了探讨。  相似文献