京津冀地区植被物候时空变化及其对城市化的响应

温度在调节植被物候的变化中起着重要作用,气候变暖和城市化均会对温度产生影响进而影响植被物候。基于京津冀地区2001—2020年的归一化植被指数(NDVI)时间序列影像,参照物候观测站点监测数据,采用动态阈值法提取出研究区关键物候参数,即生长季始期(SOG)、生长季结束期(EOG)和生长季的长度(LOG),分析近20年京津冀地区耕地、林地、草地不同植被的物候时空变化特征及其城乡差异,从而探讨植被物候对城市化的响应。结果表明：(1)耕地SOG分布呈现双波峰现象,林地和草地的SOG相对集中,3种植被的EOG的分布均较为集中;2001—2020年京津冀大部分地区的SOG提前,EOG推迟,LOG呈现延长的态势。(2)从城乡梯度物候差异的空间分布特征来看,整体而言耕地、林地、草地3种植被类型的城区物候与农村相比都存在SOG提前,EOG推迟的情况,并且城区与农村的物候差异幅度要明显大于城乡过渡带与农村的物候差异。(3)从城乡梯度物候差异的时间分布特征来看,2001—2020年间,研究区中新老城区、城乡过渡带和农村的SOG提前,EOG推迟,LOG延长,但耕地、林地、草地3种植被物候参数的城乡差异在逐年...     

植物物候对重庆主城区热岛效应的响应

为探究植物物候对山地城市内部热岛效应的响应特征,于2016年1月—2017年1月对重庆市主城区80种木本植物进行地面物候观测,同时利用Landsat 8热红外数据反演研究区地表温度,结合同时期地面实测气温,对研究区热岛强度等级进行划分,进而比较城市内部不同热岛强度等级下植物物候变化特征。结果表明,热岛过渡区与热岛区植物展叶期较凉岛区分别提前了5.1 d和8.1 d,初花期分别提前了4.0 d和20.8 d,终花期分别提前了4.8 d和11.6 d,而落叶期分别推迟了8.5 d和18.9 d,即城市内部热岛増温使植物春季物候提前,秋季物候推迟,生长季延长,且物候变化幅度随热岛强度等级增大而增大。不同功能型植物物候对热岛増温的响应存在差异,灌木、常绿植物和引种植物物候比乔木、落叶植物和本土植物更加敏感。本研究在一定程度上填补了我国西南山区物候研究的空缺,可为预测城市植物物候对未来山地城市小气候变化乃至全球气候变暖趋势的响应提供早期预警。     

滇中城市群植被物候时空变化及其对城市化的响应

植被物候是响应外界环境变化的重要感应器，本文基于MOD13Q1 EVI数据，采用动态阈值法提取滇中城市群2001—2020年的植被物候参数，即生长季开始期、生长季结束期和生长季长度，揭示植被物候时空变化特征及城乡差异。结果表明：2001—2020年，滇中城市群植被总体呈现生长季开始期推迟、生长季结束期推迟(每年推迟0.66 d)和生长季长度延长的现象；相较于郊区和乡村地区，城区植被近20年的生长季开始期提前(每年1.05 d),生长季结束期推迟(每年0.91 d),生长季长度延长(每年1.79 d)。在城区-郊区-乡村梯度上，植被物候表现出显著的差异性，城区植被平均每年生长季开始期最早，结束期最早，且生长季长度最长，尤其在城区及向外0～2 km范围内变化最明显。随人口密度、人均GDP和建成区面积占比的增大，城区植被物候生长季开始期显著提前，生长季结束期显著推迟，生长季长度显著延长。植被各物候期及其持续时间在城区-郊区-乡村梯度上对环境变化的敏感度不同，研究区人口密度和建成区面积占比对滇中城市群植被生长季结束期的推迟有重要影响。     

藏北高原植被物候时空动态变化的遥感监测研究

利用遥感数据提取的植被物候格局及时空变化特征能很好地反映区域尺度上植被对全球变化的响应。目前关于青藏高原地区植被物候的少量报道基本上是基于物候站点的观测记录展开分析的。该文基于非对称高斯拟合算法重建了藏北高原2001-2010年的MODIS EVI (增强型植被指数)时间序列影像, 然后利用动态阈值法提取整个藏北高原2001-2010年植被覆盖的重要物候信息, 包括植被返青期、枯黄期与生长季长度, 分析了植被物候10年间平均状况的空间分异特征以及年际变化情况, 并结合站点观测记录分析了气温和降水对植被物候变化的影响, 结果表明: (1)藏北高原植被返青期在空间上表现出从东南到西北逐渐推迟的水平地带性与东南高山峡谷区的垂直地带性相结合的特征, 近60%区域的植被返青期提前, 特别是高山地区; (2)植被枯黄期的年际变化不太明显, 大部分地区都表现为自然的年际波动; (3)生长季长度的时空变化特征由植被返青期和枯黄期二者决定, 但主要受返青期提前影响, 大部分地区生长季长度延长; (4)研究区内不同气候区划植被物候的年际变化以那曲高山谷地亚寒带半湿润区和青南高原亚寒带半干旱区的植被返青期提前和生长季延长程度最为明显; (5)基于气象台站数据分析气候变化对物候的影响发现, 返青期提前及生长季延长主要受气温升高的影响, 与降水的关系尚不明确。     

华南三省(区)2001—2020年植被物候时空变化

为深入了解气候变化对我国热带亚热带季风区植被物候的影响,该文基于2001—2020年MODIS EVI时序数据,采用Double Logistic法和阈值法提取华南三省(区)植被物候参数,分析了华南三省(区)植被物候的时空变化特征。结果表明, 研究区植被返青期主要集中在第90~105天,枯黄期在第320~335天,生长季在第220~235天。20年来植被返青期推迟,枯黄期基本不变,生长季缩短。在空间分布上,返青期在两广地区自西向东、自北向南逐渐推迟,海南则自东北向西南逐渐推迟;枯黄期表现为在两广中部晚、周边早,在海南中部早、周边晚的分布特征;生长季在两广地区整体自西向东逐渐缩短,在海南则自西南向东北逐渐延长。随着海拔增高,不同地区和不同植被的返青期差异较大,且波动性较大,而枯黄期先推迟后提前,生长季先延长后缩短。这揭示了气候变暖背景下华南三省(区)植被物候的变化特征,对更全面认识我国南方植被对气候变暖的响应有指导意义。     

东北地区植被物候期遥感模拟与变化规律

使用1982—2003年GIMMS-NDVI数据,借助GIS空间分析功能,提取东北地区不同植被NDVI时间序列数据,使用分段式Logistic函数模拟了东北地区不同植被物候期,分析了1982—2003年不同植被物候期的变化趋势。结果表明:针叶林、阔叶林、草丛、草甸和沼泽植被生长季开始日期提前,生长季延长,其中沼泽植被生长季开始日期提前和生长季延长的趋势明显,针叶林次之;结束日期的变化趋势表现不一,针叶林和沼泽植被生长季结束日期推迟,阔叶林、草丛和草甸植被呈现微弱提前趋势;针阔混交林、灌丛、草原和农田植被生长季开始日期推迟,生长季缩短,其中农田植被生长季开始日期推迟和生长季缩短的趋势明显,草原次之;针阔混交林、灌丛、草原和农田4种植被生长季结束日期呈现提前的变化趋势,其中灌丛结束日期的提前趋势明显。     

2003-2018年米仓山地区植被物候时空变化及对气候的响应

植被物候直接反映了植被对环境变化响应的动态过程,对研究植被与气候的关系具有重要意义。基于遥感植被时序数据,探讨秦巴山区典型山地-米仓山地区植被物候变化及其对气候的响应。利用MODIS NDVI时序数据,采用动态阈值法获取米仓山地区植被物候参数;借助于Theil Sen斜率、Mann Kendall趋势检验方法结合植被类型数据分析研究区物候时空变化;采用偏相关方法分析物候变化与气温和降水之间的关系。结果表明：（1）米仓山地区植被生长季始期（SOS）主要集中在第80-110d,海拔每上升100m,SOS大约推迟0.6d;生长季末期（EOS）主要集中在第250-300d;生长季长度（LOS）主要集中在130-210d。除低海拔区域受人类活动影响物候波动较大外,EOS和LOS随海拔变化存在2000m分界线,其下物候随海拔升高物候明显推迟或缩短,其上物候变化趋于平缓。（2）16a来植被SOS呈提前趋势,提前幅度为0.47d/a,提前的像元占74.03%,其中,达到显著提前的像元占12.21%（P<0.1）;EOS整体呈提前趋势,提前幅度为0.22d/a;LOS略有延长,延长幅度为0.26d/a。（3）区域常绿型森林植被SOS晚于同垂直带的落叶型森林植被;草地、常绿阔叶灌木林SOS提前趋势最明显,变化率分别为-0.80、-0.71d/a;EOS提前趋势最明显的是针阔混交林和落叶阔叶林。（4） SOS主要受3月平均气温和4月降水的影响,3月平均气温升高以及4月降水增加导致SOS提前;EOS主要受10月降水的负向影响。     

北方地区典型林草地物候时空变化特征及其对气象因子的响应

为探究北方地区典型植被林地、草地物候特征及其对气候变化的响应,本文基于1982—2015年的GIMMS NDVI 3gv1数据集和气象资料,采用动态阈值法提取植被物候,应用线性回归和偏相关分析法分析林、草地物候时空变化特征及其与气候变化的关系。结果表明：(1)林地生长季长度(LOS)以0.32d/a的速率极显著延长,整体表现为生长季始期(SOS)以-0.18d/a极显著提前,生长季末期(EOS)以0.14d/a极显著推迟。林地SOS提前、EOS推迟和LOS延长的区域面积占比分别为93.3%、90.4%和96.3%。(2)草地LOS以-0.01d/a的速率不显著缩短,表现为SOS以-0.09d/a不显著提前,EOS以-0.10d/a不显著提前。SOS提前、EOS提前和LOS缩短的区域占比为67.5%、69.1%和50%。(3)林地SOS主要受冬末春初的气温升高和降水增加而提前,EOS受夏季气温升高、秋季以及冬末春初降水增加而推迟。(4)草地SOS主要受春季气温升高和短波辐射减少而提前,EOS受秋季气温升高和短波辐射减少而提前,草地物候与气象因子的响应时长小于林地。     

甘肃河东地区植被物候及其对气候变化的响应

探究中纬度地区的植被物候及其对气候变化的响应,对理解生态系统对气候变化的响应以及预测区域生态系统的碳循环至关重要。本文基于2000—2018年MODIS EVI数据,利用非对称高斯函数(A-G)与动态阈值法提取森林与草地物候参数,结合气象数据探究河东地区植被物候与气候变化的响应关系。结果表明：森林与草地物候参数存在显著差异,两者生长季始期(start of growing season, SOS)的趋势均提前,生长季末期(end of growing season, EOS)的趋势分别提前和推迟,其中整体SOS呈提前趋势的面积占比61%,EOS呈推迟趋势的面积占比41%,生长季长度(length of growing season, LOS)呈延长趋势的面积占比53%;随着海拔和纬度的上升,植被SOS、EOS和LOS分别呈推迟、提前和缩短的趋势发展,但这种趋势正在减弱;季前气候对SOS和EOS存在不同程度、方向的影响,秋冬季高温推迟SOS,春季高温则提前SOS,春夏季降水增加提前EOS,秋季高温推迟EOS,且对于河东地区而言,最低气温影响更为显著;森林与草地之间对于气候变化的响应程度存...     

基于MODIS植被指数的藏北高原植被物候空间分布特征

基于非对称高斯拟合算法重建了2001-2010年的MODIS EVI时间序列影像,利用动态阈值法提取2001-2010年各年藏北高原植被覆盖的关键物候参数(生长季峰值、返青期、枯黄期及生长季长度),并在此基础上分析了藏北高原植被覆盖的物候参数空间分布特征.结果表明:植被生长季EVImax、物候返青期及生长季长度均表现出从东南到西北过渡的水平地带性与东南高山峡谷区的垂直地带性相结合的空间格局;对于不同地表覆盖类型,EVImax、返青期、生长季长度均呈现农林混合区＞林灌区＞草甸＞草原＞荒漠草原的特征,枯黄期除农林混合区较迟外,其他4种地表覆盖类型时间接近;对于不同气候区划,植被生长季EVImax、返青期、生长季长度表现出半湿润区→半干旱区→干旱区的递变规律;研究区内植被物候受地形影响较大,随着海拔的升高,植被生长季EVImax降低、物候返青期推迟、生长季长度减小.     

2001-2014年博斯腾湖流域植被物候时空变化及其驱动因子

以博斯腾湖流域为研究对象,利用MODIS的MCD12Q2和LST产品、GHCN_CAMS气温观测/再分析资料与气象数据,采取趋势分析与相关性分析法探求了博斯腾湖流域2001-2014年植被物候的时空变化及其影响因素的相对作用,对博斯腾湖流域植被物候分区不同的驱动区域。结果表明：①在研究期内,整个研究区植被物候始期在第76-168天,末期在第172-295天;物候始期自南向北逐渐推迟、而末期逐渐提前,物候的空间分布特征与该区海拔高度的分布保持了较好的一致性;②2001-2014年植被始期和末期有明显提前趋势（提前3-6d）,主要分布在流域的盆地和平原绿洲区,表示研究区植被物候受到人类活动的影响。③植被物候始期与末期变化受气候因子驱动影响的区域占比分别为57.10%和51.30%,主要分布在黄水沟流域,清水河流域,孔雀河流域,大尤路都斯盆地和小尤路都斯盆地周围地区;而非气候因子占42.90%和48.70%,主要位于博斯腾湖周围绿洲和库尔勒绿洲等地势较低的区域。④由植被生长季物候与降水、气温的偏相关性关系和复相关性关系可以得出,多年物候始期和末期与气温有关;而且随海拔升高,气温的敏感幅度越高。博斯腾湖流域植被物候的时空变化不仅是受气候变化的影响,还主要受人类活动和海拔高度差异等影响因素的共同作用。     

Extended season for northern butterflies

Butterflies are like all insects in that they are temperature sensitive and a changing climate with higher temperatures might effect their phenology. Several studies have found support for earlier flight dates among the investigated species. A comparative study with data from a citizen science project, including 66 species of butterflies in Sweden, was undertaken, and the result confirms that most butterfly species now fly earlier during the season. This is especially evident for butterflies overwintering as adults or as pupae. However, the advancement in phenology is correlated with flight date, and some late season species show no advancement or have even postponed their flight dates and are now flying later in the season. The results also showed that latitude had a strong effect on the adult flight date, and most of the investigated species showed significantly later flights towards the north. Only some late flying species showed an opposite trend, flying earlier in the north. A majority of the investigated species in this study showed a general response to temperature and advanced their flight dates with warmer temperatures (on average they advanced their flight dates by 3.8 days/°C), although not all species showed this response. In essence, a climate with earlier springs and longer growing seasons seems not to change the appearance patterns in a one-way direction. We now see butterflies on the wings both earlier and later in the season and some consequences of these patterns are discussed. So far, studies have concentrated mostly on early season butterfly–plant interactions but also late season studies are needed for a better understanding of long-term population consequences.     

基于源汇指数的沈阳热岛效应

基于2001和2010年Landsat 遥感影像,利用GIS技术识别沈阳城市热岛源区和汇区,利用地表温度(LST)、源区和汇区面积比率指数（CI）和热岛强度指数（LI）,评价分析了沈阳土地利用发展布局模式对热岛效应的影响.结果表明: 2001-2010年,沈阳三环内土地利用类型变化较大,导致热岛源、汇区面积变化明显,且主要发生在二环和三环.2001年,一环内热岛源、汇区面积比例分别为94.3%和5.7%,三环内分别为64.0%和36.0%;2010年,其比例在一环内分别为93.4%和6.6%,三环内分别为70.2%和29.8%,说明10年来“摊饼式”土地利用布局决定了沈阳热岛效应的“摊饼式”布局.研究期间,沈阳地表温度从一环至三环均呈递减趋势,热岛效应强度在2001年以单一中心为主,至2010年发展为多中心态势,热岛效应强度等级有所降低.从一环至三环,CI绝对值均呈增加趋势,LI值均小于1,说明期间研究区土地利用布局变化对改善区域热岛效应没有明显作用.     

Greater deciduous shrub abundance extends tundra peak season and increases modeled net CO2 uptake

Satellite studies of the terrestrial Arctic report increased summer greening and longer overall growing and peak seasons since the 1980s, which increases productivity and the period of carbon uptake. These trends are attributed to increasing air temperatures and reduced snow cover duration in spring and fall. Concurrently, deciduous shrubs are becoming increasingly abundant in tundra landscapes, which may also impact canopy phenology and productivity. Our aim was to determine the influence of greater deciduous shrub abundance on tundra canopy phenology and subsequent impacts on net ecosystem carbon exchange (NEE) during the growing and peak seasons in the arctic foothills region of Alaska. We compared deciduous shrub‐dominated and evergreen/graminoid‐dominated community‐level canopy phenology throughout the growing season using the normalized difference vegetation index (NDVI). We used a tundra plant‐community‐specific leaf area index (LAI) model to estimate LAI throughout the green season and a tundra‐specific NEE model to estimate the impact of greater deciduous shrub abundance and associated shifts in both leaf area and canopy phenology on tundra carbon flux. We found that deciduous shrub canopies reached the onset of peak greenness 13 days earlier and the onset of senescence 3 days earlier compared to evergreen/graminoid canopies, resulting in a 10‐day extension of the peak season. The combined effect of the longer peak season and greater leaf area of deciduous shrub canopies almost tripled the modeled net carbon uptake of deciduous shrub communities compared to evergreen/graminoid communities, while the longer peak season alone resulted in 84% greater carbon uptake in deciduous shrub communities. These results suggest that greater deciduous shrub abundance increases carbon uptake not only due to greater leaf area, but also due to an extension of the period of peak greenness, which extends the period of maximum carbon uptake.     

The interaction between island geomorphology and environmental parameters drives Adélie penguin breeding phenology on neighboring islands near Palmer Station,Antarctica

Despite many studies on Adélie penguin breeding phenology, understanding the drivers of clutch initiation dates (CIDs, egg 1 lay date) is limited or lacks consensus. Here, we investigated Adélie penguin CIDs over 25 years (1991–2016) on two neighboring islands, Torgersen and Humble (<1 km apart), in a rapidly warming region near Palmer Station, Antarctica. We found that sea ice was the primary large‐scale driver of CIDs and precipitation was a secondary small‐scale driver that fine‐tunes CID to island‐specific nesting habitat geomorphology. In general, CIDs were earlier (later) when the spring sea ice retreat was earlier (later) and when the preceding annual ice season was shorter (longer). Island‐specific effects related to precipitation and island geomorphology caused greater snow accumulation and delayed CIDs by ~2 days on Torgersen compared to Humble Island. When CIDs on the islands were similar, conditions were mild with less snow across breeding sites. At Torgersen Island, the negative relationship between CID and breeding success highlights detrimental effects of delayed breeding and/or snow on penguin fitness. Past phenological studies reported a relationship between air temperature and CID, assumed to be related to precipitation, but we found air temperature was more highly correlated to sea ice, revealing a misinterpretation of temperature effects. Finally, contrasting trends in CIDs based on temporal shifts in regional sea ice patterns revealed trends toward earlier CIDs (4–6 day advance) from 1979 to 2009 as the annual ice season shortened, and later CIDs (7–10 day delay) from 2010 to 2016 as the annual ice season lengthened. Adélie penguins tracked environmental conditions with flexible breeding phenology, but their life history remains vulnerable to subpolar weather conditions that can delay CIDs and decrease breeding success, especially on landscapes where geomorphology facilitates snow accumulation.     

Response of vegetation phenology to urbanization in the conterminous United States

The influence of urbanization on vegetation phenology is gaining considerable attention due to its implications for human health, cycling of carbon and other nutrients in Earth system. In this study, we examined the relationship between change in vegetation phenology and urban size, an indicator of urbanization, for the conterminous United States. We studied more than 4500 urban clusters of varying size to determine the impact of urbanization on plant phenology, with the aids of remotely sensed observations since 2003–2012. We found that phenology cycle (changes in vegetation greenness) in urban areas starts earlier (start of season, SOS) and ends later (end of season, EOS), resulting in a longer growing season length (GSL), when compared to the respective surrounding urban areas. The average difference of GSL between urban and rural areas over all vegetation types, considered in this study, is about 9 days. Also, the extended GSL in urban area is consistent among different climate zones in the United States, whereas their magnitudes are varying across regions. We found that a tenfold increase in urban size could result in an earlier SOS of about 1.3 days and a later EOS of around 2.4 days. As a result, the GSL could be extended by approximately 3.6 days with a range of 1.6–6.5 days for 25th ~ 75th quantiles, with a median value of about 2.1 days. For different vegetation types, the phenology response to urbanization, as defined by GSL, ranges from 1 to 4 days. The quantitative relationship between phenology and urbanization is of great use for developing improved models of vegetation phenology dynamics under future urbanization, and for developing change indicators to assess the impacts of urbanization on vegetation phenology.     

Demography of an endangered endemic rupicolous cactus

The snow cover extent is an important factor for the structure and composition of arctic and alpine tundra communities. Over the last few decades, snowmelt in many arctic and alpine regions has advanced, causing the growing season to start earlier and last longer. In a field experiment in subarctic tundra in Interior Alaska, I manipulated the timing of snowmelt and measured the response in mortality, phenology, growth, and reproduction of the eight dominant plant species. I then tested whether the phenological development of these species was controlled by snowmelt date or by temperature (in particular growing degree days, GDD). In order to expand our understanding of plant sensitivity to snowmelt timing, I explored whether the response patterns can be generalized with regard to the temporal niche of each species. Differences in the phenology between treatments were only found for the first stages of the phenological development (=phenophases). The earlier the temporal niche (i.e., the sooner after snowmelt a species develops) the more its phenology was sensitive to snowmelt. Later phenophases were mostly controlled by GDD, especially in late-developing species. In no species did an earlier snowmelt and a longer growing season directly enhance plant fitness or fecundity, in spite of the changes in the timing of plant development. In conclusion, the temporal niche of a species’ phenological development could be a predictor of its response to snowmelt timing. However, only the first phenophases were susceptible to changes in snowmelt, and no short-term effects on plant fitness were found.     

城市化对长三角地区主要城市植被物候的影响

基于长三角地区1998—2005年NDVI时间序列影像,利用移动平均法计算了上海、杭州、南京、常州、无锡和苏州6个城市的城区与各缓冲带的平均植被物候,并分析了城区与各缓冲带平均物候的差异及其与距城区距离间的关系.结果表明,1998—2005年间,研究区的城市化导致城区内植被始绿期提前、终绿期推后、生长期变长、NDVI的年内极差减小,离城区越近的缓冲带这些变化越明显.总体看来,城市化导致城区周围4 km范围内的植被始绿期明显提前,而终绿期推后、生长期变长、NDVI年内极差减小的趋势在离城区约10 km范围内的变化显著;城区与缓冲带植被的生长期差值和NDVI年内极差差值均与离城区距离存在显著的对数关系.     

Integration of flowering dates in phenology and pollen counts in aerobiology: analysis of their spatial and temporal coherence in Germany (1992–1999)

We studied the possibility of integrating flowering dates in phenology and pollen counts in aerobiology in Germany. Data were analyzed for three pollen types (Betula, Poaceae, Artemisia) at 51 stations with pollen traps, and corresponding phenological flowering dates for 400 adjacent stations (< 25 km) for the years 1992–1993 and 1997–1999. The spatial and temporal coherence of these data sets was investigated by comparing start and peak of the pollen season with local minima and means of plant flowering. Our study revealed that start of birch pollen season occurred on average 5.7 days earlier than local birch flowering. For mugwort and grass, the pollen season started on average after local flowering was observed; mugwort pollen was found 4.8 days later and grass pollen season started almost on the same day (0.6 days later) as local flowering. Whereas the peak of the birch pollen season coincided with the mean flowering dates (0.4 days later), the pollen peaks of the other two species took place much later. On average, the peak of mugwort pollen occurred 15.4 days later than mean local flowering, the peak of grass pollen catches followed 22.6 days after local flowering. The study revealed a great temporal divergence between pollen and flowering dates with an irregular spatial pattern across Germany. Not all pollen catches could be explained by local vegetation flowering. Possible reasons include long-distance transport, pollen contributions of other than phenologically observed species and methodological constraints. The results suggest that further research is needed before using flowering dates in phenology to extrapolate pollen counts.