The Relationship Between Vegetation Characteristics and Altitudes in Transitional Permafrost Zone in Xidatan, Qinghai-Tibetan Plateau

Many studies showed that permafrost has profound influence on alpine ecosystem. However, former researches were mainly focused on typical points by temporal scales. There were few studies about the correlation between vegetation characteristics and different altitudes covering a large region in spatial pattern, especially in transitional permafrost(TP). There were continuous permafrost(CP) discontinuous permafrost(DCP) and seasonal frozen ground(SFG) in this study region. The types of permafrost changed from SFG to DCP, and finally become CP as the altitudes of Xidatan increase. In this paper, 112 845 points interpreted by HJ1-B(environment and disaster monitoring and prediction small satellite constellation), vegetation investigation points, thawing layer thickness research sites, ground temperature and water content observation plots were used to examine the spatial pattern of vegetation which were located in different altitudes in Xidatan, a typical TP region, in Qinghai-Tibetan Plateau. Vegetation characteristics, soil moisture content(SMC) and thaw depths were collected in 15 August to 25 August2012. Characteristics of vegetation were mainly represented by fractional vegetation cover(FVC) derived from the normalized difference vegetation index(NDVI), as well as above ground biomass(AGB). In this paper, we analyzed that the distinction of vegetation characteristics in each range through statistics data. These ranges were divided by varied altitudes. For examples, the ranges were divided into 50 m or 100 m. In this study we use a large area plots method to further discuss the relationship between the features of vegetation and the different regions of permafrost based on altitudes shifts in Xidatan. A diagram described the vegetation characteristics variability with rising altitudes in transitional permafrost region was drawn in this paper. Our results illustrated the FVCs first increased in SFG region and then decreased in DCP zone slowly, and in CP region FVCs soared then dropped dramatically. With the altitudes increased, the curve of FVCs indicated a parabolic distribution except a little difference in the first 200 m range.

Discussion on position of China’s north-south transitional zone by comparative analysis of mountain altitudinal belts

The Qinling Mountains has always been regarded as an essential dividing line between the warm temperate zone and the subtropical zone in eastern China and plays a vital role in the geoecological pattern of China.However,there is controversy about the specific location of this geographical boundary in the academic community.As a product of the combined effects of zonal and non-zonal factors,the mountain altitudinal belts(MABs)can reflect both the horizontal zonality and the vertical zonality of vegetation distribution.Using the MAB information,we can not only profoundly understand the complex mountain system of QinlingDaba Mountains but can also judge its nature as a geographical boundary more scientifically.Therefore,based on the comparative analysis of basal belt,dominant belt characteristics and belt structure characteristics of the MABs in Qinling-Daba Mountains,subtropical and temperate mountains,this paper analyzed the MAB differences and similarities among Qinling-Daba Mountains,subtropical and temperate typical mountains,to reveal the vegetation distribution characteristics in the north-south transitional zone.The results show that:(1)The MABs of the southern part of QinlingDaba Mountains(southern slope of the Daba Mountains)are the same or similar to those of the Subtropical Mountains,and the MABs of the northern part of Qinling-Daba Mountains(northern slope of the Qinling Mountains)are similar to those of the temperate mountains.While it shows obvious transitional characteristics in the vast area between the northern slope of the Daba Mountains and the southern slope of the Qinling Mountains:the basal belts gradually transit from the evergreen broadleaved forest belt(basal belt in subtropical mountains)to the evergreen and deciduous broad-leaved mixed forest belt,and the dominant belts also transit from the evergreen broad-leaved forest belt to the evergreen and deciduous broad-leaved mixed forest belt or the deciduous broad-leaved forest belt.(2)The transitional zone between the subtropical zone and the warm temperate zone is located between the northern slope of the Daba Mountains and the southern slope of the Qinling Mountains.The southern boundary of the transitional zone is along the northern slope of Shennongjia Mountain-the northern slope of Micang Mountain-Baishuijiang Nature Reserve,and the northern boundary is along the southern slope of Funiu Mountain-the southern slope of Taibai Mountain-Lianhua Mountain.Additionally,in the transitional zone,the average temperature in January is between-5°C and 1°C,the annual average temperature is between 10°C and 13°C except Hanzhong Basin and Hanshui Valley,and the accumulated temperature above 10°C ranges from 2000°C to 4000°C,the annual rainfall is about 800-1000 mm.The results provide a scientific basis for revealing the characteristics of China’s north-south transitional zone and scientific division of the boundary between the subtropical zone and warm temperate zone in China.

The Role of Physical and Political Factors on the Conservation of Native Vegetation in the Brazilian Forest-Savanna Ecotone

The AraguaiaRiver Basincovers a considerable extent of Brazilian Savanna (locally called Cerrado) and part of Amazon Tropical Rainforest, embracing high biodiversity and a vast flooding area. This region has been converted to agricultural lands since 1970s, for the past four decades, leading to a fragmented landscape that holds one of the few large remaining blocks of Cerrado primary vegetation. Therefore, to assess the degree of preservation of this area a 2007 primary vegetation map was derived through Boolean operations using land use and land cover maps from 1975, 1985, 1996 and 2007, from digital classification of Landsat MSS and TM images. To evaluate the role of driving factors on the presence of pristine vegetation, a logistic regression analyses was performed. Tested factors were: distance from roads and cities, terrain slope, land tenure, soil fertility and flooding. We found statistical significant values (p nous lands, wetlands and areas with low fertility have positive influence on the presence and maintenance of these pristine areas. The occurrence of original vegetation in many cases is associated with environmental constraints that difficult or do not allow agricultural use. Analysis of physical and political factors, which may have direct or indirect influence on the conservation and degradation of native vegetation are very important for the comprehension of the dynamics of regional land use, and provide supporting information for a more efficient and sustainable regional landscape planning.

川西北高寒典型沙区植被恢复动态遥感监测研究

近几十年来,土地退化、沙化问题威胁着川西北地区草原生态环境和群众生产生活。为获取并定量分析沙区治理的植被恢复动态及趋势,探讨典型沙区的生态修复变化机制,本文以红原县瓦切镇典型沙区1984、2000和2021年3期长时序Landsat遥感影像为数据源,在ENVI 5.3和ArcGIS 10.2软件的支持下,通过植被覆盖指数(NDVI)与光谱混合分析(NDVI-SWA)相结合的方法提取植被覆盖度(FVC),运用土地动态度空间分析模型和转移矩阵分析川西北高寒典型沙区植被恢复变化特征。结果表明:(1)研究区植被覆盖度等级结构以高度植被覆盖度为主(占50%以上),且不同植被盖度类型存在明显空间差异;(2)1984年研究区植被覆盖情况最差,2021年植被覆盖情况最好,中度及以下植被覆盖度面积仅占4.71%。1984-2021年,变化幅度最大的是中度以下植被覆盖度情况,占比呈现出先增加后降低的趋势,相对而言,中高度、高度植被覆盖度处于较为稳定的变化状态。(3)各级FVC转移矩阵分析中,具体转化方向较为一致,主要是向高植被覆盖方向转化,表现为:中高等级向高等级转化;低等级向中低、中等级转化。

香日德—柴达木河流域NDVI时空变化及其影响因子研究

【目的】探究香日德—柴达木河流域植被覆盖度变化及其与气象因子的关系。【方法】以2000-2021年归一化植被指数(NDVI)为基础并结合气温、降水数据,采用植被覆盖转移矩阵、ArcGIS空间分析和数理统计等方法,分析了该流域NDVI的时空变化趋势及其对气温和降水的响应。【结果】(1)香日德—柴达木河流域近22年NDVI整体呈现出增加趋势,增速为0.0071/a;2010年NDVI值最大,为0.256,2001年NDVI值最低,为0.180,均值为0.220;(2)研究区内中覆盖、较高覆盖及高覆盖植被的覆盖面积增加,裸地和低覆盖植被的覆盖面积减少,植被由东南向西北逐渐退化,在海拔4000-4500 m处植被覆盖度最高;(3)气温和降水均对NDVI有一定的影响,气温升高限制了NDVI增长,而降水的增加有助于提高NDVI。【结论】研究区近22年生态环境明显改善,植被整体恢复较好,气温、降水及海拔综合影响该地区的植被生长。

石羊河流域植被生态质量时空变化动态监测

基于遥感和GIS技术,以MODIS NDVI为数据源,应用DEM和土地利用分类图,采用转移矩阵、一元线性回归模型等方法,对石羊河流域2000-2020年植被生态质量指数(Q)的时空变化特征进行研究,并对Q值基于不同海拔高度、坡度、坡向和植被类型的分布特征进行分析。结果表明:(1)2000-2020年石羊河流域的平均Q值为9.8,南北差异较大,Q值与海拔高度和坡度呈正相关;(2)分析Q转移矩阵,流域植被生态质量处于改善之中,2000-2010年植被生态质量改善和退化面积占总面积的比例分别为30.0%和2.2%,2010-2020年分别为13.7%和10.9%;(3)2000年以来流域Q值平均每10a增加1.2,呈增加趋势(Slope>0.0)的区域面积占整个研究区面积的90.3%;(4)Q值呈增加趋势的面积随着海拔高度的增大呈波动变化,随着坡度的增大先增加后减小;(5)森林、草地和灌木丛植被类型Q值呈增加趋势所占比例均在60.0%以上;(6)研究区Q值与气温、降水的相关系数分别为0.352和0.281,气温是植被生长的主要影响因素。

近20年鄂西地区植被覆盖度时空变化特征分析

基于2000—2020年的MOD13Q1 NDVI遥感数据,使用像元二分模型计算湖北省西部山体区域的植被覆盖度,并利用斜率模型、马尔可夫转移矩阵模型和赫斯特指数综合分析了植被覆盖度的时空变化规律。结果表明,研究区的植被覆盖度总体呈上升趋势,平均植被覆盖度增加了0.025,轻微增长区域面积为44 359.26 km^(2),显著性增长面积为3 069.375 km^(2),不显著性变化的面积为39 862 km^(2)。2000—2020年期间,时序植被覆盖度的赫斯特指数为0.63,表明研究区内植被覆盖度的增长趋势在未来是可持续的。本研究成果不仅可为城市生态环境评价提供科学依据,而且可为城市的生态建设和可持续发展提供决策支持。

中国第二、三级阶梯地形过渡带植被NDVI时空动态研究

基于二、三级阶梯地形过渡带2001~2020年的MODIS归一化植被指数和气象数据,利用趋势分析、相关分析等方法,分析过渡带植被NDVI的时空变化特征及其受气候因子的影响机制,并利用多元回归残差分析过渡带植被动态变化驱动力的空间分布.结果表明:2001~2020年,二、三级阶梯地形过渡带植被以0.028/10a的变化率增加,显著改善区占研究区总面积的53%.在生长季期间,二、三级阶梯地形过渡带的植被生长对气温、降水和辐射的响应存在一定的滞后性,滞后于气温1个月,滞后于降水和太阳辐射3个月.从海拔上来看,显著改善区集中分布在0~1000 m,显著退化区集中分布在1500~2000 m.20年来,自然要素和人为要素对植被变化的影响占研究区总面积的87%和6%.

煤炭资源枯竭转型城市植被碳汇变化观测:以徐州为例

在国家“碳达峰、碳中和”战略背景下,资源枯竭型城市的生态修复正成为固碳增汇的重要途经,利用长时间序列观测数据开展固碳增汇能力定量评价,将为设计资源枯竭型城市生态修复方式提供有价值的参考。以我国东部典型资源枯竭转型城市徐州为研究区域,通过“涡度相关法”和“卫星遥感”2种方式观测分析了总初级生产力(Gross Primary Productivity,GPP)的时空变化特征。结果表明:(1)在生长季植被生长旺盛的时候,MODIS卫星遥感对GPP存在低估,是由于光能利用率模型将同种植被的最大光能利用率设为定值,不能体现植被生长状态的影响,从而增加了估算光能利用率的不确定性。但MODIS GPP与涡度相关通量塔实测GPP数据变化趋势一致,有较强的相关性(R~2=0.587,P=0),因此MODIS GPP数据可用于徐州矿区生态修复前后GPP变化特征分析。(2) 2005—2011年,徐州煤矿开采对徐州矿区生态环境破坏严重,固碳能力持续减弱,2011年后徐州地区采取生态修复措施,GPP明显升高,到2015年GPP达到最高值(0.878 kgC/(m^(2)·a)),2016—2020年GPP变化趋于稳定(0.85 kgC/(m^(2)·a)左右)。(3)徐州采取的矿区关闭、煤矸石回填、生态公园建设等一系列生态修复措施,提高了原有矿区的固碳增汇能力,形成了自稳定生态系统,且未来仍有改善的趋势,证明对煤炭资源枯竭型城市进行生态修复可以在5~10 a内有效改善当地生态环境,快速提升当地的植被固碳能力,为其他煤炭资源枯竭型城市的生态修复提供参考。

Dynamics of mediterranean pine forests reforested after fires

Forest fires are frequent under a Mediterranean climate and have shaped the landscape of the region but are currently altered by human action and climate change.Fires have historically conditioned the presence of pine forests,depending on severity and forest regeneration.Regeneration of Mediterranean pine forests is not always successful,and a transition to shrublands or stands of resprouting species can occur,even after reforestation.This study analyses vegetation changes in two Mediterranean pine forests after severe fires and both reforested.The pines had difficulty to regenerate,even despite post-fire reforestation.The problem is the difficulty of young seedlings to survive,possibly due to increased summer drought.Problems are greater in pine species at the limit of their ecological tolerance:Pinus pinea had a much better recovery success while P.sylvestris and P.nigra virtually disappeared.Pinus pinaster had intermediate results but recovery was generally poor.A transition has taken place in many burnt areas to scrubland or to thickets of the resprouting Quercus rotundifolia,although it is not possible to know whether they will evolve into forests or remain in a sub climatic state.Resprouting species may increase fire severity but facilitates post-fire colonisation.Post-fire recovery difficulties are closely linked to issues of natural regeneration.Fire could initiate the disappearance of pine forests,but even in the absence of fire they may disappear in the long-term due to the lack of regeneration.Action is needed to increase the resilience of these forests,ensuring natural regeneration,and incorporating resprouting species in the understorey.

基于地理探测器的开都-孔雀河流域植被覆盖度时空变化及驱动力分析

植被覆盖度(FVC)是反映生态环境质量的评价指标,系统研究植被覆盖变化和驱动机制对区域生态管理至关重要。本研究基于MODIS数据,运用Sen+Mann-Kendall趋势分析法、地理探测器模型等方法,分析新疆开都-孔雀河流域植被覆盖度的演变趋势,探讨植被覆盖度与驱动因子之间的空间关联,并识别主导因子。结果表明:(1)2000-2020年开都-孔雀河流域植被覆盖整体呈上升趋势,年增长速率为每10年0.013。2011年之前植被覆盖度均值略有小幅度波动,之后植被覆盖度持续增加,在2019年达到最大值29.0%。空间尺度上,2020年极低植被覆盖度分布度最广,占研究区面积的51.93%,21年间减少了5010.31 km^(2),其次是高植被覆盖度,占研究区面积的22.84%。(2)开都-孔雀河流域以极低覆盖度与低覆盖度之间转化为主。研究区植被有轻微的改善趋势,其中17.82%的区域呈极显著(P<0.01)、显著增加趋势(P<0.05);71.90%的区域变化不显著(P>0.05)。(3)研究区植被覆盖主要受高程和土地利用类型的影响,其解释力均在0.45以上。两两因子之间的协同作用影响显著高于单个因素,其中高程和土地利用类型两两相交的解释力最高为0.743。

东秦巴山地自然保护地样区植被物候的过渡特性研究

本文选取东秦巴山地神农架样区和伏牛山样区2个自然保护地集中分布地域作为研究区,通过比较分析南、北2个不同地域精细尺度的物候格局,探讨东秦巴山地植被物候的南北过渡特征。基于近20年时序遥感影像信息综合提取植被物候空间格局,从物候总体分布特征、物候与高程关系等多方面分析2个研究区物候特征的联系和差异,并在物候信息高程校正的基础上,对比分析同高程、不同地域物候的南北变化特征及规律。研究结果表明,在不考虑地形高程影响的情况下,神农架样区植被生长季开始期晚于伏牛山样区8.49 d;生长季长度则短于伏牛山样区9.31 d;不同海拔高度对于南、北2个研究区植被物候影响也不一样,海拔每增高100 m,神农架样区生长季开始时间推迟1.97 d,生长季长度缩短2.54 d;伏牛山样区生长季开始时间推迟2.05 d,生长季长度缩短1.56 d。经过高程校正,神农架样区整体植被生长季开始时期比伏牛山样区早2.52 d,植被生长季长度比伏牛山样区植被生长季长度增长了3.91 d。比较2个研究区主要的植被类型落叶阔叶林和常绿针叶林之后可发现,神农架样区的落叶阔叶林生长季开始时间比伏牛山样区早3.25 d;常绿针叶林的生长季开始时间比伏牛山样区早1.78 d,生长季长度长11.96 d。在植被物候信息高程校正前后,2个研究区的植被生长季开始期相对早晚、生长季长度相对大小均发生反转。这种物候格局的复杂分布特征,较好地呈现了多列山地阻隔和分异作用所形成的东秦巴山地植被复杂过渡特征。

东北农牧交错区水分条件及其对植被分布的影响

水分条件是决定植物生长、分布的主要因子之一 ,也是生态学和地理学研究所关注的一个基本问题。本文依据最新的数据资料对东北农牧交错区水分条件的基本特征进行了分析 ,以三维图形表达了湿度指数的空间分布格局 ;对典型站点的年干燥度以及在年内的变化进行了分析 ;通过Kira指数、湿度指数和NDVI植被指数说明了农牧交错区植物生长。

基于NDVI的农牧交错区植被覆盖度变化研究——以宁夏盐池县为例

为了解农牧交错区植被覆盖度变化，以宁夏盐池县为例，基于NDVI和植被覆盖度遥感定量模型，提取了植被覆盖等级图。在此基础上对盐池县1989年、1999年、2003年的植被覆盖度等级图进行对比分析，结果表明两个时间段的植被盖度都呈增加趋势，后期（1999～2003年）年均变化明显高于前期（1989～1999年）年均变化，这主要归功于荒漠化治理措施（包括退耕还林、禁牧封育等）以及降水增加等多种因素。与此同时，在生态环境建设过程中，原有中、高覆盖度植被发生退化。因此，今后的治理工作应该加大对中、高盖度植被地区的保护工作。

锡林河流域植被叶面积指数时空变化特征及其对地形因子的响应

为了摸清欧亚大陆大草原重要的组成部分锡林河流域在外界环境和人类活动干扰下植被的时空变异规律及其与地形因子的响应关系,利用遥感影像数据及基于大气阻抗植被指数(ARVI)的统计模型,反演了1985—2015年4个典型代表年份的LAI,从长时间尺度上分析了LAI的时空变化特征以及地形因子对其空间分布格局的影响。结果表明:近30 a,锡林河流域LAI总体呈上升趋势,多年平均值为0.8～1.5,从上游至下游逐渐降低。植被恢复状况空间差异明显,主要发展态势为恢复。LAI在0.78～0.82,0.82～0.86所占面积比例随着海拔、坡度的升高而降低,在东南方向上的面积占比大于其他方向;LAI在0.92～1.5,1.5～3.0所占面积比例随着海拔、坡度的升高而增大,在西、西南方向上的面积占比大于其他方向。高程对LAI的直接影响效应为0.438,远大于坡度和坡向对LAI的影响。本研究可为草原型流域陆面过程及生态水文研究提供理论基础和科学依据,对于天然生态系统的健康维持、退化生态系统的恢复重建等也具有一定的参考价值。

敦煌绿洲—戈壁过渡带地表辐射与能量特征分析

利用“西北干旱区陆—气相互作用野外观测试验”2002年在敦煌加强期的资料,分析了敦煌绿洲—戈壁过渡带的地表辐射和能量特征。研究表明:白天,绿洲—戈壁过渡带的地表温度和近地层大气温度很高,和戈壁的地表温度接近;在多数晴天夜晚,绿洲—戈壁过渡带的地表温度和近地层大气温度要低于戈壁的值。总辐射、反射辐射和地表长波辐射的值都很接近荒漠戈壁的值,日积分通量分别为24.48,6.1,41.42MJ.m-2.d。绿洲—戈壁过渡带的感热、潜热和地表热通量的日积分值分别为6.58,1.60和0.38MJ.m-2.d。同时,在绿洲—戈壁过渡带有较强的水平湍流输送。

干旱半干旱区草原灌丛化的原因及影响-争议与进展

灌丛化作为全球干旱半干旱区草原普遍发生的现象,其定义为草原生态系统中灌木/木本的生物量、密度、盖度的增加以及草本的生物量、密度、盖度的减少。草原灌丛化是气候变化和人类活动多种因素综合作用的结果。过度放牧被认为是引发草原灌丛化的主要原因之一。最新的研究结果表明过度放牧并不能导致草原灌丛化,但过度放牧后实施休牧却改变了草本与灌木的种间作用,有可能导致灌木的扩张。灌木入侵草原长期以来被认为是草原的退化,结论来源于干旱区土壤沙化的情形,在沙化的灌木林中,土壤碳库被局限于灌木株丛及其周边,使草原的碳截留和储存降低。但最近的全球性集成研究表明草原中灌木覆盖率盖度增加对生态系统可以产生积极作用,灌木可以增加土壤水分的下渗,有利于生态系统的水分储存和和养分的转化(如加强氮的矿化过程)。草原灌丛化对生态系统结构和功能影响存在景观尺度和斑块尺度上的差异。进一步研究适应灌丛化过程的管理机制,综合不断变化的气候条件因素和地域因素,采取合理的草原管理策略,对于全球草原区生产具有极其重要的意义。

玻璃化转变在食品贮藏中的应用研究进展

玻璃化转变是指无定形聚合物因受热从玻璃态到橡胶态(高弹态)或因冷却从橡胶态到玻璃态的转变。玻璃化转变是影响食品性质、加工特性和货架期的重要因素之一。文章介绍了玻璃化转变相关的基本理论,阐述了玻璃化转变在微生物和酿造发酵食品、果蔬、淀粉类食品、水产品、乳制品、冷冻禽畜肉类及糖果类食品贮藏方面的研究现状,并对玻璃化转变在食品贮藏的应用进行了展望。

中国北方农牧交错带植被动态研究进展

通过回顾植被动态研究的历史,简要概述了植被动态的发展。综述了我国北方农牧交错带历年来植被动态的研究现状。研究指出植被动态变化与农牧交错带内气候、自然环境演变、农牧业经营方式的转变及土地利用有着密切的关系。结合前人的研究,根据农牧交错带内存在的生态环境问题,提出应从北方农牧交错带植被动态与生物多样性、生态环境、生态系统健康以及对全球变化响应的关系进行研究,揭示其受损及恢复机理,为农牧交错带受损的生态系统恢复与重建、区域可持续发展提供理论依据。

用NOAA气象卫星的AVHRR遥感资料估算中国的净第一性生产力

重点研究用气象卫星ＡＶＨＲＲ遥感方法估算目前中国的净第一性生产力（ＮＰＰ）水平。ＡＶＨＲＲ可见光通道和近红外通道组合成的标准化差植被指数（ＮＤＶＩ），既是监测植被生长好坏的参量，也是计算净第一性生产力的重要参量。介绍了用遥感统计模型计算ＮＰＰ的方法，获得了一系列结果。将遥感方法计算的ＮＰＰ与气候模型计算的ＮＰＰ进行了比较，证明两者有一定的可比性。计算净第一性生产力需要全年的ＮＤＶＩ。