天山北部地区植被覆盖的时空变化及趋势分析

根据1982—2006年GIMMS-NDVI数据,采用线性趋势法和Hurst指数法,对天山北部植被覆盖状况的时空变化、发展趋势进行分析。结果表明:天山北部地区整体植被覆盖度不高,山麓地带、河湖沿岸的绿洲农业区植被覆盖较好。研究时段内的植被覆盖有退化的趋势,且退化区域以绿洲边缘区及中低山区为主,主要农耕区在灌溉措施保障下,植被覆盖有改善的趋势。天山北部的植被覆盖变化具有持续性特点,持续增大区主要分布在绿洲农业区;持续减小区主要分布在中低山区;沙漠戈壁区无显著变化特征。     

1982—2020年毛乌素沙地植被对气候变化的响应

毛乌素沙地属于我国北方农牧交错区,生态环境脆弱,植被生长受气候环境影响较大。基于1982—1999年GIMMS NDVI3g.v1数据、2000—2020年MOD13Q1数据,以及相关气象站点的气温降水数据,运用趋势分析、变异系数、偏相关分析及Hurst指数等方法,探讨1982—2020年毛乌素沙地植被生长时空特征及其对气候变化的响应。研究结果表明：1)毛乌素沙地植被生长状况呈现持续向好趋势,每10 a的增速为1.3%,以2005年为拐点,2005年以前植被长势缓慢,之后长势迅猛。2)毛乌素沙地NDVI均值介于0.10～0.41之间,空间分布呈“西低东高”的特征,沙地植被变化以增加为主,约占总面积的94.07%,其中显著增加占57.43%,极显著增加占30.14%;植被的空间变化稳定性地区差异明显,高波动变化区域占比最大,为35.95%,带状分布于沙地东南部边缘植被生长旺盛区域。3)4,6,8月,毛乌素沙地NDVI与气温正向相关系数较高;6—9月,NDVI与降水正相关性较强,降水对沙地植被生长发育的影响更大,植被变化的同向特征强于反向特征。4)毛乌素沙地未来变化趋势将以持续改善和持续退...     

北疆不同生态功能区近30年来植被盖度时空变化

NDVI时空变化不仅可反映生态环境的变动趋势,而且还能揭示出区域植被的恢复与退化状况。以1981—2003年GIMMS NDVI和1998—2010年SPOT VGT NDVI时间序列数据为基础,运用NDVI最大值合成法和趋势分析法,分析了北疆近30年来不同生态功能区及不同植被类型NDVI时空变化规律。结果表明:1)从北疆大功能区来看,1981—2003年期间NDVI平均值变化呈周期波动,增幅缓慢,并以2002年为转折期,北疆整体植被改善程度不断增强。2)从不同生态功能区看,1981—2003年伊犁河谷地区、天山北坡和阿尔泰山的南部生态区等主要生态功能区植被改善明显,在准噶尔盆地荒漠生态区及其东部区植被呈轻度植被退化;1998—2010年北疆大部地区植被恢复明显,伊犁河谷、天山北坡中段绿洲平原区植被改善程度达到极显著水平。3)北疆植被的改善或退化趋势可能与同期实施的生态建设工程以及区域气候的总体变化有关。     

1982—2013年准噶尔盆地植被长势变化分析

利用准噶尔盆地1982—2013年的GIMMS NDVI3g数据,以及温度、降水、日照等气候因子数据,结合当地防沙治沙工程等人类活动,分析近32年来该区域的植被变化状况,结果表明:1)准噶尔盆地33.0%的区域呈现植被退化现象,约20.0%的区域呈现植被恢复现象。2)植被退化区域主要分布在干旱区域,植被覆盖稀疏,为半荒漠地带;植被显著恢复的区域主要位于植被较浓密区域。3)近32年来温度的上升使得干旱区的蒸发量增大,因降雨量变化不明显,因此干旱趋势加剧,植被的长势变弱;而准噶尔盆地南部区域,因区域供水平衡稳定,温度的上升促进了植被的生长。4)人类活动对该区域的植被长势变化影响不明显。土地沙漠化治理需要一个较长的周期,应该不断加强该区域的土地沙漠化治理及治理成效的监测。     

基于MODIS NDVI数据的广西植被覆盖时空变化遥感诊断

【目的】对广西2006—2016年植被覆盖变化特征及其变化关键因素进行遥感诊断,为掌握广西地区植被覆盖的时空变化提供科学监测结果和诊断依据。【方法】基于250 m分辨率16天合成的MOD13Q1产品,利用趋势分析法获得11年间广西植被覆盖整体变化情况;结合气象数据,运用回归因子分析法得到植被覆盖变化与温度和降水之间的关系;采用遥感影像差异法对不同时期MODIS土地覆盖类型数据进行分析,探讨人类活动对植被覆盖变化的影响。【结果】2006—2016年11年间广西植被覆盖在波动中呈上升趋势;归一化差值植被指数(NDVI) 2—3月呈最低状态,9月最高。全区植被增加面积大于退化面积,其中面积增加最大的区域包括河池、百色、南宁东南部和桂林东部,退化面积最大的区域包括崇左、百色中部、南宁西部和桂林中部,退化程度最高的北海区域退化面积占全区面积的28. 9%。11年间,广西植被覆盖类型变化巨大,林地面积显著上升,农用地面积下降明显。【结论】温度和降水与植被覆盖呈正相关关系,二者与植被覆盖在月尺度上的正相关性较年尺度更为显著,且降水对植被的影响高于温度对植被的影响; MODIS土地覆盖类型数据反映出的人类活动表明,林地面积显著增加是广西NDVI上升的主要原因。     

近30年来东洞庭湖植被覆盖时空变化研究

洞庭湖湿地变化一直是湿地生态研究一项重要内容。本研究利用1989—2016年间6期的TM/ETM数据,结合气象、水位数据对东洞庭湖的植被覆盖度进行时空变化及关联分析,以期从长时间序列上揭示东洞庭植被覆盖变化的机理,为湿地植被保护提供重要的理论依据。结果表明:1)研究时段上,东洞庭湖的整体植被覆盖度存在降低的趋势,空间上,植被覆盖度等级围绕着水体呈现出由低到高的梯度差异。2)1989—2016年间,东洞庭湖的植被覆盖情况以退化为主,退化面积达到75.59%,且以轻度退化为主要类型;整体来说,研究区南边比北边退化程度高。3)研究区低、高植被覆盖区受水位变化的影响较大,与东洞庭湖特有的水文变化特征密切相关。     

1982—2015年河北省生态环境支撑区植被覆盖动态及其可持续性

植被是第一性生产者,是维持生物圈物质循环和能量流动的关键因素。河北省建设京津冀生态环境支撑区,植被建设占重要地位。利用1982—2015年的GIMMS NDVI3g数据,经像元二分法获得植被覆盖度,采用最小二乘法趋势分析和Hurst可持续分析方法分析近34年河北省各生态环境支撑区植被覆盖度的空间分布特征与长期变化趋势。结果表明,1982—2015年河北省生长季年平均植被覆盖度为49.4%。34年间,河北省植被覆盖度呈现整体增加的趋势,增加幅度为1.5%/10a,植被覆盖度增加的区域占总面积的90%以上。可持续性上,植被正向变化的可持续性较强,且以持续改善为主。由变化趋势与Hurst指数的耦合信息得出,植被覆盖增加区和退化区的Hurst指数的平均值分别为0.86和0.85,表明未来变化趋势将保持一致,即改善的持续改善,退化的持续退化。     

多伦县植被覆盖空间格局及动态变化研究

借助ENVI 4.3及GIS10.0软件,估算了多伦县2000年、2005年和2009年3期植被覆盖度,并结合研究区年平均降雨量变化趋势,分析得出:从空间分布格局上来说,多伦县植被覆盖处于良好状态,绝大部分地区已达40%以上,属中覆盖类型,而植被覆盖度较低的地区主要集中在该区西北部,且呈零星分布,说明该区林业工程生态效益明显;其次,从动态变化趋势上来分析,可以看出2000-2009年间,研究区植被覆盖度总体上呈现增加趋势,但后期(2005-2009年)较前期(2000-2005年)而言,增加幅度有所较小,这与该时段年平均降雨量变化相一致。     

浑善达克沙地2000—2018年NDVI时空变化及其驱动因素分析

基于MODIS和气象数据,对浑善达克沙地2000—2018年植被NDVI时空变化及其驱动因素进行分析。结果表明:(1)19 a间植被NDVI总体呈现上升趋势,年均值为0.35,上升幅度为0.057/10 a;在空间分布上,苏尼特右旗、苏尼特左旗东部和克什克腾旗和锡林浩特市部分区域植被有退化趋势,阿巴嘎旗、正蓝旗、正镶白旗的大部分区域植被呈增加的趋势,植被NDVI改善区域面积占总面积的58.42%,退化面积占总面积的17.95%。(2)浑善达克沙地年均降水量在127.6~348.6 mm之间,浑善达克沙地NDVI与降水的偏相关系数在-0.88~0.94,正相关性达到97.59%;NDVI与气温的偏相关系数在-0.81~0.88,正相关区域占总体的68.96%,负相关区域占总体的31.04%,整体而言降水是研究区NDVI变化的主要影响因素。     

基于Landsat的青神县植被覆盖动态变化分析

以Landsat TM/OLI系列遥感数据为基础,利用RS和GIS为技术手段提取NDVI值,通过像元二分模型得出青神县2009年、2013年、2018年三期的植被覆盖度分级图,并用转移矩阵和差值法分析其动态变化情况。结果表明:青神县植被覆盖总体良好,植被覆盖度以中高以上为主。2009—2013年该地区中高以上植被覆盖区占总面积的比例由71.73%降到62.69%,2018年有所改善,占总面积的67.77%,说明2009—2018年青神县植被覆盖度经历了先退化后改善的趋势,但整体发生了小幅度退化,退化面积比改善面积多出6.22 km~2,占总面积的1.6%。据分析,城区的扩张、基础设施的建设侵占了耕地和林地,是造成青神县植被覆盖度退化的主要原因。为促进区域生态环境的可持续发展,应进一步提升中心城区及周边的植被覆盖度。     

Relationship between vegetation carbon storage and urbanization: A case study of Xiamen, China

Rapid growth of the Chinese urban population and the expansion of urban areas have led to changes in urban forest structure and composition, and consequently changes in vegetation carbon storage. The purpose of this study is to quantify the effects of urbanization on vegetation carbon storage in Xiamen, a city located in southern China. Data used for this study were collected from 39,723 sample plots managed according to the forest management planning inventory program. Data from these plots were collected in 4 non-consecutive years: 1972, 1988, 1996 and 2006. The study area was divided into three zones, which were defined according to their level of urbanization: the urban core, the suburban zone, and the exurban zone. Total vegetation carbon storage and the vegetation carbon density for each study period were calculated for each zone. Our results show that urban vegetation carbon storage has increased by 865,589.71 t during the period from 1972 to 2006 (34 years) in Xiamen, with a rapid increase between 1972 and 1996, then relatively little change between 1996 and 2006. The increase in vegetation carbon storage is mainly due to the large percentages of the suburban and exurban areas which exist in Xiamen city, and the implementation of reforestation programs in these two zones. The percentage of total regional carbon storage in the city center (urban core), suburbs and exurbs was 5%, 23% and 72%, respectively. This demonstrates that the exurbs store the majority of vegetation carbon, and thus play a critical role in the vegetation carbon storage of the study area. The intensification of urbanization in the future will likely expand the urban core and reduce the area of the suburbs and exurbs, and thus potentially decrease total vegetation carbon storage. This article concludes with a discussion of the implications of these results for vegetation carbon management and urban landscape planning.     

陕西佛坪国家级自然保护区蝶类季节变化的调查

2006年4月～2007年10月,对陕西佛坪国家级自然保护区蝶类进行了种类、数量调查和统计,分析了该地区蝶类资源的季节性变化.共收集蝴蝶标本2625余只,隶属11科106属203种.研究表明季节的变化,植被类型及植物生长情况的变化是决定蝴蝶种类组成和分布的主要因素.     

Direct seeding of Quercus robur L. for reforestation: The influence of mechanical site preparation and sowing date on early growth of seedlings

Compared with conventional planting, direct seeding of Quercus spp. is a method that can reduce the costs of reforestation considerably. However, interference from natural vegetation and predation on acorns contribute to regeneration failures. Mechanical site preparation has the potential to reduce both these problems. To study the influence of sowing date and of different mechanical site preparation treatments on early seedling growth, an experiment was carried out in storm-felled areas, formerly Norway spruce forests, in southern Sweden from May 2006 to September 2008. Five treatments were applied and acorns were planted in May and July 2006. The treatments were: disc trenching, patch scarification, topsoil removal, mounding and an undisturbed control. A delay of less than two months in seeding resulted in the equivalent of one year's growth reduction with respect to oak seedling's height and biomass. This could be explained by delayed emergence of seedlings, and by the dry conditions during summer seeding. The seedlings only exhibited a weak positive biomass growth response following disc trenching, patch scarification and top soil removal. In the latter case this might be explained by increased soil compaction and extensive removal of the humus layer. Site preparation by mounding resulted in good vegetation control, an increased biomass growth response and deeper seedling roots. In this treatment, we found high relative light levels near seedlings, reduced soil moisture and dry bulk density of the soil and higher soil temperatures. One or more of these environmental factors could have influenced the growth response. Whether this increased early growth rate persists throughout young stand development is, however, uncertain.     

Invertebrate abundance in different forest habitats as animal food available to capercaillie Tetrao urogallus chicks

Invertebrate abundance was estimated in 1981 and 1982 by sweep‐netting at twelve forest vegetation types in Vegårshei, Southern Norway. Invertebrates are expected to be a major determinant of habitat quality to gallinaceous birds, since animal food is considered essential to young chicks. The twelve fixed stations were chosen to illustrate poor and rich habitats and a gradient from bog to forest habitat. Rich vegetation types also had the highest abundance of invertebrates mainly due to moist and heavy soils. A comparison between a clear‐cutting and a similar vegetation type not logged, showed strong reduction in invertebrate availability after cutting. The influence of this alteration on availability of the capercaillie Tetrao urogallus chicks’ food is discussed.     

喀斯特森林自然恢复演替中林木对生境利用分析

以喀斯特区小生境及其地表着生植物作为研究对象,分析了喀斯特区小生境分布面积及不同小生境植物的分布现状。不同生境面积比例关系是石面>土面>石沟>石缝>石槽>石洞。在森林群落的自然恢复演替进程中,林木株数密度的变化是从草本群落阶段到灌丛灌木阶段逐渐上升,灌乔过渡阶段林木株数密度和灌木林阶段基本一致,演替到乔林阶段林木株数密度最大,到顶级群落阶段林木株数密度又出现下降。在森林群落恢复的早期,林木主要占据石缝和土面的小生境,随着演替的进行,对于石面这种严酷的小生境植物也能充分利用。植被在自然恢复演替的早期,喀斯特区小生境对植物的生长有一定的限制作用,随着演替的进行,生境的限制作用逐渐减弱,在森林群落演替的后期,林中小气候的变化成为植物演替的主要限制条件。     

离子型稀土矿堆浸场地不同恢复年限植被多样性

生物群落多样性是判断生态系统稳定的重要指标,为了解人工建植对稀土矿废弃地生态系统的影响,以福建省长汀县离子型稀土矿堆浸废弃地为研究对象,利用植被恢复固定监测点,选取植被恢复5、8、11 a废弃地为样点,调查不同恢复年限样地物种种类和数量,分析稀土矿废弃地物种多样性随恢复时间的变化规律。结果表明:随植被恢复年限的增加,前期人工种植的植物逐渐被本土野生植物取代,增加物种以禾本科和菊科植物为主。乔木层、草本层植物种类和数量随恢复年限的增加而增加;随着植被恢复年限的增加,稀土矿废弃地乔木层物种丰富度(Gleason指数、Margalef指数)、Shannon指数逐渐增加,而乔木层、草本层Pielou均匀度指数则呈先增加后下降趋势;植被恢复8与11 a植被相似度最高,其次是植被恢复5与8 a,其中植被恢复11 a与对照样地植被相似度最低;Margalef指数、Simpson指数与Shannon指数呈显著相关。因此,随着植被恢复年限的增加,稀土矿生态退化区植被恢复前期人工干涉效应在逐渐降低,后期演变为自然演替,物种群落结构和种类发生变化,但与当地本土植物群落仍存在一定差异,表明生态退化区植被演替仍处于动态变化阶段。     

Soil carbon and nutrient pools in Douglas-fir plantations 5 years after manipulating biomass and competing vegetation in the Pacific Northwest

We assessed changes in mineral soil total carbon (C) and nutrient (exchangeable Ca, K, Mg, and total N) pools to 60 cm depth 5 years after manipulating biomass and competing vegetation at two contrasting Douglas-fir plantations (Matlock, WA, and Molalla, OR). Biomass treatments included whole-tree (WT) and bole-only (BO) harvest, and competing vegetation control (VC) treatments were applied as either initial or annual herbicide applications. There were main effects of biomass removal and VC on the absolute change in soil pools of some elements at both sites, but significant effects were more prevalent at the lower soil quality Matlock site than the Molalla site, and were generally confined to the top 15 cm of soil. In all cases, treatment effects were associated with increases in C and nutrients following BO and initial VC treatments combined with little change in soil pools following WT and annual VC treatments. At the Matlock site, total soil pools (0-60 cm) of C, N, and Ca significantly increased in the BO and initial VC treatments, and Mg increased and K decreased regardless of treatment. At the Molalla site, soil C and nutrient pools did not change in response to treatments, but total soil Mg increased in all treatments during the study period. Correlation analyses indicated little influence of soil nutrient pools on early growth at Matlock likely because soil water is more limiting than nutrient availability at that site, but vegetation growth was correlated to nutrient pools at Molalla indicating changes in pools associated with harvesting and treatment could influence crop development in the future. These early results indicate low potential for intensive management practices to reduce mineral soil pools of C and nutrients, but there is uncertainty on the long-term growth response because treatments may have influenced nutrient storage in pools other than mineral soil.     

洱海流域植被覆盖度遥感估算与变化分析

植被覆盖度是刻画地表植被覆盖的一个重要参数,也是指示生态环境变化的重要指标之一.以洱海流域1990年和2006年TM影像为数据源,利用NDVI的像元二分模型法对洱海流域1990年和2006年植被覆盖度进行遥感估算,并进行变化分析.结果显示,近17年来洱海流域植被覆盖度总体上有所提高,无植被覆盖区域面积明显下降,高植被覆盖占全植被覆盖区域面积比大幅提高,二者面积比近50％;在空间分布上,洱海流域上游地区、东部部分地区植被覆盖度相对较低,对地区生态环境稳定构成重大威胁,将是今后洱海流域生态建设和整治的重点区域.     

Daily variations of airborne pollen in Beijing Olympic Park during August of three consecutive years and their relationships with meteorological factors

A three-year aeropalynological study was carried out in the month of August for each of the three years 2005, 2006 and 2007 in the Beijing Olympic Park. A total of 19550 pollen grains were counted (15057 grains in 2005, 2717 in 2006 and 1776 in 2007) for the following taxa: Gramineae, Chenopodiaceae, Humulus L., Artemisia L., Ambrosia L. and Pinus L. The analysis indicated that in the three consecutive years of 2005–2007, airborne pollen types and daily number of pollen in August in the Beijing Olympic Park were closely related to environmental change and vegetation composition. The daily variations of airborne pollen displayed similar patterns in August in each of the three years, which were affected positively by periods of daily sunshine, negatively by daily relative humidity and daily precipitation. Continuously high daily temperatures and stable daily wind speeds seemed to have little effect on the fluctuation of airborne pollen.     

Understory Response to Repeated Thinning in Douglas-fir Forests of Western Oregon

This study investigated effects of a second-thinning entry on understory vegetation and tree regeneration development and understory vegetation composition. Study sites were located in the Coast Range and Cascade Range mountains of western Oregon and were dominated by Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) forests. Stands were initially thinned between 1975 and 1982 and parts of these same stands were thinned again approximately 20 yr later. Thinning stands a second time resulted in greater amounts of fern, graminoid, and open-site species, but the abundance of tree regeneration was not affected. Despite different site conditions, compositional patterns in the understory consistently shifted toward open-site early seral species following the second thinnings. These results suggest that the initial impacts of a second thinning are not simply predictable from studies in which only a single thinning was implemented. It is important to consider that vegetation trends were already influenced by the previous thinnings, and impacts of the second thinning are thus not as easily detectable. Within these limitations, repeated thinnings may be an effective management tool to maintain early seral species in older forests, while other aspects of understory vegetation and tree regeneration are less influenced in the short term.