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1.
Foy Lake in northwestern Montana provides a record of annual-to-decadal-scale landscape change. Sedimentary charcoal and pollen analyses were used to document fire and vegetation changes over the last 3800 years, which were then compared to similar records from AD 1880 to 2000. The long-term record at Foy Lake suggests shifts between forest and steppe as well as changes in fire regime that are likely the result of climate change. Fire activity (inferred from the frequency of charcoal peaks) averaged 18 fire episodes/1000 years from 3800 to 2125 cal year BP, and increased from 16 fire episodes/1000 years at 2125 cal year BP to 22 episodes/1000 years at 750 cal year BP, a period when the pollen data suggest that steppe vegetation yielded to increasing patches of forest cover. Between 2125 and 750 cal year BP, increased forest cover produced more background charcoal than before and after this period, when vegetation was dominated by steppe. Between 750 and 75 cal year BP steppe has expanded and fire episode frequency averaged 33 episodes/1000 years, increasing to a maximum of 40 episodes/1000 years at ca. 300 cal year BP and then decreasing to present levels. Since AD 1880, the pollen record indicates an increase in shrubs and grasses from AD 1895 to 1960 as a result of vegetation changes associated with timber harvesting and livestock grazing. No fires have been documented in the Foy Lake watershed since AD 1880. Charcoal from the extralocal fires of AD 1910, burning over 4,111,249 ha in Idaho, Montana, and Wyoming, however, is present in Foy Lake. Between AD 1970 and 2000, increased arboreal pollen in the record is consistent with observations that the forest has become more closed. The activities of Euro–Americans have led to a decline in forest cover between AD 1880 and 1970, followed by a recent increase as trees are now growing in areas previously occupied by steppe. Euro–Americans are likely the cause of a reduction in fire activity in watershed since AD 1880.  相似文献   

2.
为了研究新疆不同类型植被对气候变化的响应,以地带性划分的植被类型作为研究对象,1998-2012年为时间尺度,利用GIS的空间分析方法结合数学统计方法,分析了新疆各地带植被覆盖变化的时空分布特征;并采用"多元回归+残差插值"的方法,模拟了气温和降水量的空间分布;利用SPOT VGT/NDVI数据以及气候数据(气温和降水量数据),分析了5个不同地带植被的动态变化、年际变化和生长季内各月变化及其对气候变化的响应。结果表明:(1)新疆各地带植被覆盖度存在着显著差异,其中,温带北部草原地带高植被区和浓密植被区的范围较广,植被覆盖度较高,而高寒荒漠地带的极低植被区占该地带面积的一半以上,且植被覆盖度最低。(2)新疆各地带植被覆盖在近15 a间呈波动增加的趋势,5个地带的植被覆盖均有所改善,其中,高寒荒漠地带和暖温带半灌木、灌木地带的植被覆盖改善较为明显,其余3个地带均有少部分地区出现轻微改善现象。(3)温带半灌木、矮乔木荒漠地带,暖温带半灌木、灌木荒漠地带和温带半灌木、灌木荒漠地带4~10月的平均气温呈上升趋势,而温带北部草原地带、高寒荒漠地带对应的平均气温则出现下降趋势。5个地带的降水量在该时段内均表现为下降趋势。(4)基于年际尺度,新疆各地带植被NDVI与气温、降水量的相关性均不显著;基于月尺度,各地带植被NDVI受降水量的影响比气温大。同时,仅有暖温带半灌木、灌木荒漠地带植被NDVI与气温存在1个月的滞后性,其余4个地带对气温和降水均不存在滞后性。  相似文献   

3.
神农架大九湖四万年以来的植被与气候变化   总被引:3,自引:0,他引:3  
通过对大九湖6 m长连续沉积岩芯剖面(DJH-1 孔) 7 个样品的AMS14C年龄测定和151 块孢粉样品的鉴定分析, 揭示了神农架区域4 万以年来植被和气候演变。末次冰期阶段大九湖附近发育森林草地或草地-草甸植被。MIS 3 晚期, ~42-39 cal ka BP之间, 气候相对干冷, 发育森林草地;~39-31 cal ka BP 之间, 气候较为湿润, 草甸扩张并伴随低海拔阔叶树种的发育。MIS 2 阶段, 草甸组分中蒿属显著增加, 高海拔可能分布有荒漠草地, 气候极端干冷;该时期植被带垂直下降达到1000 余m, 按垂直温度递减率推算, 冰盛期阶段该区域温度下降约7℃左右。从冰消期开始, 森林植被开始扩张, 北温带、暖温带和亚热带乔木组分依次增加。约在9.4-4 cal ka BP之间, 演变为亚热带常绿阔叶落叶林, 属全新世适宜期;从约4 cal ka BP以来, 北温带阔叶和针叶树开始增加, 气候趋于凉干。通过对比区域高分辨率的洞穴石笋及高纬冰芯氧同位素记录, 表明神农架区域植被环境变化对气候变化敏感, 并记录了H1, YD气候突变事件;进一步体现出该区域气候环境演变主要与北半球太阳辐射控制的东亚夏季风强度变化有关, 且与北半球高纬气候变化一致。  相似文献   

4.
Terrestrial ecosystem disturbances inferred from the fossil hemlock pollen decline (ca. 4,800 BP) and recovery (ca. 3,800 BP) affected van Nostrand Lake, including the diatom communities. Ecological models suggest the lake responded by eutrophying, reflecting higher nutrient influx resulting from increased erosion. A decline in lake productivity followed as the forest vegetation recovered and erosion slowed. Lastly, as the forest switched from early and middle successional species to mature species, lake productivity increased as erosion increased nutrient inflow, especially phosphorus. However, this eutrophication response was delayed or buffered, perhaps due to wetland development surrounding the lake. The lake never fully returned to its initial, pre-hemlock decline state, but oscillated between more eutrophic and more mesotrophic or oligotrophic stages, possibly reflecting other disturbances in the catchment and climatic change.  相似文献   

5.
Pollen and charcoal data from the Jingerwa section of the Nihewan Basin, north-central China, were used to reconstruct vegetation and climate changes during Marine Isotope Stage (MIS) 3. Mean annual precipitation changes were quantified by applying pollen-climate transfer functions. Sparse vegetation cover dominated by herbs indicates relatively dry climate between 51 and 43 cal ka BP. Between 43 and 35 cal ka BP, a Pinus-dominated forest reached its maximum extent, implying that climate was wetter than today. Severe fire episodes during that period suggest warm temperatures. Between 35 and 32 cal ka BP, forest retreat and the expansion of dryland vegetation are indicative of drier climates. Slightly wetter conditions prevailed between 32 and 29 cal ka BP, as indicated by the expansion of ferns. Our results suggest that the climate conditions in the Nihewan Basin during middle and late MIS 3 were probably wetter than today. This may have been caused by intensification of Asian monsoon circulation in response to greater insolation in June at 30°N. However, increases in summer temperatures and evaporation, triggered by peak summer insolation levels, may have led to a reduction in humidity around 35 cal ka BP.  相似文献   

6.
基于MODIS-NDVI、DEM和气象数据,分析柴达木盆地2000—2015年植被覆盖度(FVC)时空变化特征,并与降水、温度、日照时数、相对湿度、蒸散量和海拔进行相关、偏相关或叠加分析,探讨FVC与各环境因子的关系。结果表明:FVC整体自东南向西北内陆呈半环状递减,FVC集中在20%以下,人类活动及径流等打破植被地带性规律;2000—2015年FVC明显改善,广泛分布于盆地中西部地区,2001—2002年年际变化最显著;FVC与降水、相对湿度以正相关为主,与温度关系不显著,与日照时数和蒸散量主要为负相关,降水对FVC贡献最大,温度通过影响蒸散量等间接影响FVC,而土壤蒸发对蒸散量的影响大于植物蒸腾;FVC与等高线空间分布较吻合,FVC在2 800~2 900 m和4 600~4 700 m出现两个峰值,4 700 m以上FVC迅速降低。  相似文献   

7.
High-resolution analysis of macroscopic charcoal and pollen ratios were used to reconstruct a 10,000 yr history of fire and vegetation change around Dog Lake, now in the Montane Spruce biogeoclimatic zone of southeastern British Columbia. Lake sediment charcoal records suggest that fire was more frequent in the early Holocene from 10,000 to 8200 calendar yrs BP, when climate was warmer and drier than today and forest fuels were limited. Fire frequency increased and reached its maximum during the early to mid-Holocene from 8200 to 4000 calendar yrs BP, corresponding to the dry and warm Hypsithermal period in the Rocky Mountains. During the Hypsithermal period forests around Dog Lake were dominated by Pseudotsuga/Larix,Pinus and open meadows of Poaceae that were subject to frequent fire. From 4000 calendar yrs BP to present, fires became less frequent with the onset of cooler and wetter Neoglacial climate and an increase in wet-closed Picea and Abies forests in the valley. Changes in fire frequency are supported by dry-open/wet-closed pollen ratio data indicating that forest type and disturbance regimes vary with changing climate. The fire frequency and forest cover reconstructions from Dog Lake are a first attempt at defining a range of natural variability for Montane Spruce forests in southeastern British Columbia. Fire and vegetation management in Kootenay National Park can now use this century to millennial-scale range of variability to define the context of current forest conditions and potential changes under global warming scenarios.  相似文献   

8.
华北平原晚冰期以来气候环境演变研究对该地区社会发展、灾害风险评估和科学应对未来全球增温背景下极端降水和洪涝事件具有重要意义。本文以华北平原中部白洋淀地区高阳剖面(BG-2019)为研究对象,通过高精度AMS14C、OSL定年技术和高分辨率孢粉组合、粒度组分分析,恢复和重建了白洋淀地区晚冰期以来(距今13710 a—今)区域植被演替和气候环境变化历史。结果显示:BG-2019剖面在距今10270~13710 a和距今4630~5400 a发育湖相沉积,距今3470~3700 a发育沼泽相沉积;距今7130~8000 a发育河流—入湖三角洲相沉积,距今3700~4630 a和距今3230~3470 a发育河流相沉积;距今8000~10270 a和距今5400~7130 a存在明显的沉积间断/地层缺失;表明采样剖面所在位置缺乏连续的湖相地层。晚冰期白洋淀为局地小湖沼;中全新世湖沼较发育、范围广,但也不是连续广袤的湖相沉积;晚全新世湖泊范围收缩。晚冰期和全新世白洋淀流域植被景观存在显著差异;晚冰期气候寒冷干燥,平原发育以蒿属、藜亚科、禾本科和菊科等为主的草地,周围山地森林覆盖度低;中全新世气候温暖湿润,平原大部仍发育以蒿属、藜亚科和禾本科为主的草地,湖区水蕨和水生植物繁盛,周围山地生长松属、栎属为主的针阔混交林,森林覆盖度增高;晚全新世气候温和偏干,平原仍是以蒿属、藜亚科和禾本科等为主的草地,西部山地生长以松属为主的针阔混交林,森林覆盖度较高。  相似文献   

9.
利用1982-2000年NOAA/AVHRR卫星的NDVI数据(时间分辨率旬,空间分辨率8 km×8 km),结合同时期的气温和降水资料,基于时滞互相关方法和GIS工具,分析了青藏高原植被覆盖对水、热条件年内变化的时滞响应及其空间特征。结果如下:①除高寒荒漠、森林外,青藏高原植被NDVI与同期旬均温和旬降水相关性均呈高度正相关。其中,中等覆盖度的植被受水、热影响表现更为强烈。②青藏高原植被NDVI对气温和降水有滞后效应,且滞后水平存在空间差异,高原北部(柴达木盆地、昆仑山北冀)和高原南部植被对降水、和温度的响应比较迟缓,而高原中、东部地区植被对温度和降水的响应比较敏感。③不同植被类型对水热条件的响应程度也存在差异,由高到低依次是草甸、草原、灌丛、高寒垫状植被、荒漠,最后是森林。  相似文献   

10.
共和盆地末次冰消期以来的植被和环境演变   总被引:10,自引:1,他引:9  
程波  陈发虎  张家武 《地理学报》2010,65(11):1336-1344
在青藏高原共和盆地中的内陆湖泊--达连海获取40.92 m长的湖泊岩芯(DLH钻孔),选用植物残体作为测年材料,利用AMS14C测年技术建立可靠的地层年代序列,对岩芯进行孢粉分析,重建该地末次冰消期以来的古植被和古环境。末次冰消期以来达连海周围山地在14.8~12.9Cal ka BP和9.4~3.9 Cal ka BP时段曾发育森林,气候较湿润,达连海附近盆地发育的荒漠草原盖度增加或演化为草原;在15.8~14.8 Cal ka BP、12.9~9.4 Cal ka BP 和3.9~1.4 Cal ka BP 时段该地气候比较干旱,依据干旱的程度周围山地森林退化或消失,盆地内发育盖度较低的荒漠草原或草原化荒漠。1.4 Cal ka BP以来湿度有所增加,发育草原植被类型。依据植被的演替历史推断该地气候的变化历程是15.8~14.8 Cal ka BP 干旱,14.8~12.9 Cal ka BP 湿润,12.9~9.4 Cal ka BP干旱,9.4~3.9 Cal ka BP湿润,3.9~1.4 Cal ka BP干旱,1.4~0 Cal ka BP湿润。达连海的孢粉记录与附近青海湖的孢粉结果对比,发现两地植被发育基本一致。末次冰消期Bølling-Allerød 时期,山地森林发育;新仙女木事件发生时森林萎缩;全新世中期两地针叶林发育达到鼎盛,之后逐渐减少至消失。早全新世达连海森林扩张的时间滞后于青海湖,主要与两地森林树种的不同和植被演替的时间差异有关。该区森林发育的全盛时期在中全新世,这与石笋记录到的亚洲季风强盛时期在早全新世不相一致,可能与植被复杂的响应机制有关。  相似文献   

11.
From the high alpine Sägistalsee (1935 m a.s.l.), 13.50 m of continuously laminated sediments comprising the last 9050 years, were analyzed. Even though Sägistalsee is a high elevation site, human-induced environmental changes start as early as 4300 cal. BP and leave a clearly detectable signal in the mineralogy of the sediments, which is much stronger than the signal from natural environmental changes that occurred before this time. Variations in the physical and mineralogical sediment properties of this clastic sequence reflect erosional changes in the catchment, where almost pure limestone contrasts with carbonaceous, quartz-bearing marl, and shist. The calcite/quartz (Cc/Qz) ratio was found to be most indicative of these changes, which occurred around AD 1850 and at 650, 2000, 3700, and 6400 cal. BP. The first four are interpreted as erosion events, which are related to human-induced changes in the vegetation cover and land use. We associate them to the recent development of tourism and grazing, the medieval intensification of pasturing, Roman forest clearance, and Bronze Age forest clearance, respectively. The Cc/Qz-ratio increases significantly within less than 100 years during these events, reflecting the erosion of unweathered or poorly weathered soils. The time intervals in between are characterized by a gradually decreasing Cc/Qz-ratio and reflect the stabilization or formation of new soils. Only the change at 6400 cal. BP, which represents the initial gradual stabilization of the catchment, is related to the immigration of Picea abies.  相似文献   

12.
基于遥感和地理信息系统技术,利用1998—2008年SPOT-VEGETATION归一化植被指数(NDVI)数据对塔里木河干流区1998—2007年植被覆盖的时空变化进行了监测,并从气候变化和土地利用变化双重角度分析了植被覆盖变化的原因。研究表明,塔里木河干流区植被覆盖变化经历了两个阶段:1998—2001年植被覆盖严重退化时期;2002—2007年植被覆盖度由急剧上升到缓慢下降再到持续升高时期,NDVI明显高于20世纪末期水平。塔里木河干流区植被覆盖变化存在显著的空间差异,绿洲农业灌溉区和退耕还林还草生态恢复区的植被覆盖度显著提高,天然草地植被区的植被退化严重。塔里木河干流区植被覆盖变化是气候和土地利用变化共同作用的结果。温度对植被覆盖变化的影响表现为对植被生长年内韵律的控制和秋季植被生长期的延长,年降水量的波动式上升是导致塔里木河干流区植被覆盖变化两个阶段呈现差异的主导因素。  相似文献   

13.
近10年蒙古高原植被覆盖变化及其对气候的季节响应   总被引:8,自引:0,他引:8  
利用2001~2010年间MODIS NDVI数据、同期气象数据和MODIS土地覆盖分类产品,探讨蒙古高原植被覆盖变化趋势及其对气温和降水量的季节响应特征。结果表明,10 a来,蒙古高原植被覆盖度呈增加趋势和呈下降趋势的面积基本持平;春季和夏季植被覆盖度呈下降趋势,而秋季呈上升趋势,降水量是最主要的影响因子;在秋季5种植被类型均呈增加趋势,而在春季和夏季不同植被类型的增减趋势因植被类型而异。  相似文献   

14.
A combination of pollen and macrofossil analyses from six lakes at altitudes between 370 and 999 m above sea level (a.s.l.) in the Torneträsk area reflect the Holocene vegetation history. The main field study area has been the Abisko valley at altitudes around 400 m a.s.l. The largest lake, Vuolep Njakajaure has annually laminated (varved) sediments. The chronology and sedimentation rates in the pollen-influx calculations are based on varve yrs in this lake and on radiocarbon dated terrestrial plant macrofossils in the other lakes. A strong increase of mountain birch (Betula pubescens ssp. tortuosa) during the early Holocene with a tree-line c. 300 m above the present, indicates that the summer temperature was c. 1.5 °C higher than today, assuming that the land uplift has been 100 m since then. Scattered stands of pine (Pinus sylvestris) may have been growing in the area immediately after the deglaciation but a forest consisting of pine and mountain birch expanded first at low elevations and reached the eastern parts of the Torneträsk area at c. 8300 cal BP and the western parts at c. 7600 cal BP. The highest pine-birch forest limit was not reached until 6300 cal BP (110 m above present pine limit). Warm and dry conditions during the pine forest maximum led to lowering of the water level documented in Lake Badsjön in the Abisko valley about 1-1.5 m lower than today. Pine and mountain birch were growing at the maximum altitude until c. 4500 cal BP. Assuming that land uplift has been in the range of 20-40 m since the mid-Holocene, this implies that the temperature was then c. 1.5-2 °C higher than today. Rising lake-levels and lowering limits of pine and mountain birch since c. 4500 cal BP indicate a more humid and cool climate during the late Holocene.  相似文献   

15.
MODIS影像的NDVI和LSWI植被水分含量估算   总被引:6,自引:4,他引:2  
植被含水量估算在作物灌溉和森林火灾预警中具有重要指导意义。采用8天合成MODIS地表反射率数据,针对植被水分含量与陆表水指数,植被覆盖与归一化植被指数的关系及不同植被类型和地表水分含量状况在NDVI-LSWI二维空间中的分布规律,在NDVI-LSWI梯形特征空间中确定最大和最小含水量边界线的基础上采用植被干燥指数直接估算植被水分亏缺程度。该方法不仅简便,而且可以避开植被指数温度梯形图中陆地表面温度和气温差值的测量。  相似文献   

16.
根据采自福建省中部戴云山脉亚高山水系源头地带(大致25°40'N,118°11'E)泥炭沉积洼地的孢粉纪录,对该地区亚热带山地植被近4 000年来的变化进行了研究.孢粉记录和其他沉积资料显示,3个取样点的泥炭沉积开始于4 000年前,很可能是全新世后期气候转冷的结果.在距今4 000~1 200年前期间,戴云山脉上部(海拔1 300~1 600 m)的植被为亚热带针阔叶混交类型,优势种属包括Cryptomeria(柳杉)、Castanopsis(栲)、Quercus(栎)和Tsuga(铁杉)等.距今1 200年前左右,该区域的植被发生了一次大的变化,表现在上述优势属种的孢粉在样品总孢粉数的比例突然下降,而Pinus(松),Gramineae(禾本科)以及Dicranopteris(芒萁)等属种的比例则提高了.这次剧烈的植被变化在其中的一个泥炭钻孔中留下了一层粘土记录,它代表了当时流域内植被受破坏后出现的严重土壤侵蚀.从泥炭沉积提取的孢粉记录还可以看出,研究区内广泛分布的松林是一种次生植被,它是人类不断干扰的结果.  相似文献   

17.
In Northeast Thailand, the climate change has resulted in erratic rainfall and tem- perature patterns. The region has experienced both periods of drought and seasonal floods with the increasing severity. This study investigated the seasonal variation of vegetation greenness based on the Normalized Difference Vegetation Index (NDVI) in major land cover types in the region. An assessment of the relationship between climate patterns and vegeta- tion conditions observed from NDVI was made. NDVI data were collected from year 2001 to 2009 using multi-temporal Terra MODIS Vegetation Indices Product (MOD13Q1). NDVI pro- files were developed to measure vegetation dynamics and variation according to land cover types. Meteorological information, i.e. rainfall and temperature, for a 30 year time span from 1980 to 2009 was analyzed for their patterns. Furthermore, the data taken from the period of 2001-2009, were digitally encoded into GIS database and the spatial patterns of monthly rainfall and temperature maps were generated based on kriging technique. The results showed a decreasing trend in NDVI values for both deciduous and evergreen forests. The highest productivity and biomass were observed in dry evergreen forests and the lowest in paddy fields. Temperature was found to be increasing slightly from 1980 to 2009 while no significant trends in rainfall amounts were observed. In dry evergreen forest, NDVI was not correlated with rainfall but was significant negatively correlated with temperature. These re- sults indicated that the overall productivity in dry evergreen forest was affected by increasing temperatures. A vegetation greenness model was developed from correlations between NDVI and meteorological data using linear regression. The model could be used to observe the change in vegetation greenness and dynamics affected by temperature and rainfall.  相似文献   

18.
城市不同下垫面的能量平衡及温度差异模拟   总被引:2,自引:0,他引:2  
城市能量平衡是研究城市热岛效应的物理基础。利用北京市教学植物园2010年的实测数据,设置不同类型下垫面(植被覆盖类型:林地、草地和不透水层覆盖类型:道路、房屋),利用局地尺度城市气象参数化方案模拟并分析了相同气象条件和净辐射通量输入下,不同类型下垫面的显热、潜热通量及蒸散降温效应的差异。结果显示:(1)不同类型下垫面的各能量支出项有明显差异,植被覆盖区域和不透水层覆盖区域的波文比年均值分别为0.28和4.60,且在植被生长季差异较大;(2)城市扩展过程中道路、房屋替换林地、草地的过程,也是显热增加而潜热减少的过程。植被层向不透水层转换的过程中,显热通量年均增加32.74W/m2,潜热通量减少38.87W/m2,储热通量增加7.95W/m2;(3)理论上,植被蒸散的年降温效应使单位面积植被覆盖区域的气温比不透水层区域可低2.63℃。  相似文献   

19.
清代西南地区森林空间格局网格化重建   总被引:1,自引:0,他引:1  
基于遥感土地利用数据和全球潜在植被数据,确定了中国西南地区土地垦殖前森林植被可能的分布范围,并通过量化地形(海拔、坡度)和气候生产潜力(光照、温度、水分)与农林地分布间的关系,构建了土地宜垦性评估模型和历史森林面积网格化分配模型,重建了清代西南地区5个时点、分辨率为10 km×10 km的森林空间格局。结果表明:①本文设计的森林空间格局网格化重建方法具有一定的可行性,其结果能较好地反映森林变迁历史过程的基本特征;②西南地区森林覆被率从雍正二年(1724年)的54.7%下降至宣统三年(1911年)的27.8%,其减少地区主要分布在四川盆地、云南中南部以及贵州大部;③从网格占比的变化趋势看,1724-1911年,西南地区森林覆被率小于10%的网格占比上升了约31个百分点,而覆被率大于80%的网格占比则下降了约13个百分点。  相似文献   

20.
Urban forests play an important role in the thermal comfort and overall life of local populations in large-and medium-sized cities.This study analyzes urban forest loss and maps land use and land cover (LULC) changes between 1991 and 2018 by evaluating the use of urban planning instruments for the mitigation of urban forest loss in Jo~o Pessoa,Brazil.For this purpose,satellite-derived LULC images from 1991,2006,2010 and 2018 and data on urban forest loss areas obtained using the Google Earth Engine were used.In addi-tion,this paper also discusses the instruments used for integrated urban planning,which are(a) the legal sector,responsibility and nature;(b) the urban expansion process;and (c) the elements of urban infrastructure.The results show a clear shift in land use in the study area.The major changes in LULC classes occurred in urban areas and herbaceous vegetation,while the greatest loss was in arboreal/shrub vegetation.Thus,an increase in the pressure to occupy zones intended for environmental preservation could be estimated.Our results showed similar accuracies with other studies and more spatial details.The characteristics of the patterns,traces,and hotspots of urban expansion and forest cover loss were explored.We highlighted the potential use of this proposed framework to be applied and validated in other parts of the world to help better understand and quantify various aspects of ur-ban-related problems such as urban forest loss mapping using instruments for integrated urban planning and low-cost approaches.  相似文献   

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