The impact of red deer on liverwort-rich oceanic heath vegetation

Background: There is concern about increasing numbers of large herbivores including red deer (Cervus elaphus), but little is known about their impact on bryophytes.

Aims: This study set out to determine the effect of different localised densities of red deer on the internationally important Northern Atlantic hepatic mat, characteristic of oceanic heath vegetation, at four locations in the Scottish Highlands where sheep have been absent for decades.

Methods: Thirty 7 m × 7 m plots were randomly located in each study area. The standing crop dung pellet group count method was used to estimate red deer density. Species richness, diversity and cover of hepatic mat liverworts were obtained from 1 m × 1 m quadrats placed at random within the sample plots. Calluna vulgaris cover, ericoid height, rock cover, gradient and altitude were also recorded.

Results: Model simplification in analysis of covariance revealed a consistent pattern of decreasing cover of hepatic mat and Calluna with increasing red deer density at all four study areas. Northern Atlantic hepatic mat cover, diversity and species richness were positively correlated with Calluna cover.

Conclusions: The data suggest that Calluna cover is reduced (through trampling and browsing) at high local densities of red deer which has had cascading effects on the Northern Atlantic hepatic mat. Alternative explanations are discussed.     

Climate change drives substantial decline of understorey species richness and abundance in Norway spruce forests during 32 years of vegetation monitoring

Questions

Observations in permanent forest vegetation plots in Norway and elsewhere indicate that complex changes have taken place over the period 1988–2020. These observations are summarised in the “climate-induced understorey change (CIUC)” hypothesis, i.e. that the understorey vegetation of old-growth boreal forests in Norway undergoes significant long-term changes and that these changes are consistent with the ongoing climate change as an important driver. Seven testable predictions were derived from the CIUC hypothesis.

Location

Norway.

Methods

Vegetation has been monitored in a total of 458 permanently marked plots, each 1 m², in nine old-growth forest sites dominated by Picea abies at intervals of 5–8 years over the 32-year study period. For each of the 52 combinations of site and year, we obtained response variables for the abundance of single species, abundance and species density of taxonomic–ecological species groups and two size classes of cryptogams, and site species richness. All of these variables were subjected to linear regression modelling with site and year as predictors.

Results

Mean annual temperature, growing-season length and the number of days with precipitation were higher in the study period than in the preceding ca. 30-year period, resulting in increasingly favourable conditions for bryophyte growth. Site species richness decreased by 13% over the 32-year study period. On average, group abundance of vascular plants decreased by 24% (decrease in forbs: 38%). Patterns of group abundance change differed among cryptogam groups: although peat-moss abundance increased by 39%, the abundance of mosses, hepatics and lichens decreased by 13%, 49% and 67%, respectively. Group abundance of small cryptogams decreased by 61%, whereas a 13% increase was found for large cryptogams. Of 61 single species tested for abundance change, a significant decrease was found for 43 species, whereas a significant increase was found only for 6 species.

Conclusions

The major patterns of change in species richness, group species density and group abundance observed over the 32-year study period accord with most predictions from the CIUC hypothesis and are interpreted as direct and indirect responses to climate change, partly mediated through changes in the population dynamics of microtine rodents. The more favourable climate for bryophyte growth explains the observed increase for a few large bryophyte species, whereas the decrease observed for small mosses and hepatics is interpreted as an indirect amensalistic effect, brought about by shading and burial in mats of larger species and accelerated by reduced fine-scale disturbance by microtine rodents. Indirect effects of a thicker moss mat most likely drive the vascular plant decline although long-term effects of tree-stand dynamics and former logging cannot be completely ruled out. Our results suggest that the ongoing climate change has extensive, cascading effects on boreal forest ecosystems. The importance of long time-series of permanent vegetation plots for detecting and understanding the effects of climate change on boreal forests is emphasised.     

Long-term fire and vegetation change in northwestern Amazonia

Amazonian forest plots are used to quantify biodiversity and carbon sequestration, and provide the foundation for much of what is known about tropical ecology. Many plots are assumed to be undisturbed, but recent work suggests that past fire, forest openings, and cultivation created vegetation changes that have persisted for decades to centuries (ecological legacies). The Yasuní Forest Dynamics plot is one of the most biodiverse places on earth, yet its human history remains unknown. Here, we use charcoal and phytolith analysis to investigate the fire and vegetation history of the Yasuní forest plot, and compare results with nearby forest plots in Colombia (Amacayacu) and Peru (Medio Putumayo-Algodón [MPA]) to explore the spatial variability of past disturbances and ecological legacies in northwestern Amazonia. Three ¹⁴C dated charcoal fragments provided evidence for a modern (1956 CE) and a past fire event ca. 750 years ago at Yasuní, compared with fire ages of 1000–1600 years ago documented at Amacayacu and MPA. Small-scale disturbances and localized canopy openings also occurred in the Yasuní plot. Phytolith assemblages from Yasuní and Amacayacu showed more variability in past vegetation change than MPA. Low-intensity, non-continuous disturbances occurred at all three plots in the past, and our results highlight the variability of past human activities both in space and time in northwestern Amazonia. Our data also suggest that post-Columbian human disturbances from the Rubber Boom (AD 1850–1920) and subsequent oil exploration have likely left stronger ecological legacies than those left by pre-Columbian peoples in our studied regions.     

Predicted changes in vegetation structure affect the susceptibility to invasion of bryophyte-dominated subarctic heath

Background and Aims

A meta-analysis of global change experiments in arctic tundra sites suggests that plant productivity and the cover of shrubs, grasses and dead plant material (i.e. litter) will increase and the cover of bryophytes will decrease in response to higher air temperatures. However, little is known about which effects these changes in vegetation structure will have on seedling recruitment of species and invasibility of arctic ecosystems.

Methods

A field experiment was done in a bryophyte-dominated, species-rich subarctic heath by manipulating the cover of bryophytes and litter in a factorial design. Three phases of seedling recruitment (seedling emergence, summer seedling survival, first-year recruitment) of the grass Anthoxanthum alpinum and the shrub Betula nana were analysed after they were sown into the experimental plots.

Key Results

Bryophyte and litter removal significantly increased seedling emergence of both species but the effects of manipulations of vegetation structure varied strongly for the later phases of recruitment. Summer survival and first-year recruitment were significantly higher in Anthoxanthum. Although bryophyte removal generally increased summer survival and recruitment, seedlings of Betula showed high mortality in early August on plots where bryophytes had been removed.

Conclusions

Large species-specific variation and significant effects of experimental manipulations on seedling recruitment suggest that changes in vegetation structure as a consequence of global warming will affect the abundance of grasses and shrubs, the species composition and the susceptibility to invasion of subarctic heath vegetation.     

近10年来蒙古高原植被覆盖变化对气候的响应

基于东亚干旱半干旱地区内蒙古和蒙古国67个气象站的观测资料和SPOTVEGETATION归一化植被指数(NDVI)数据,借助线性趋势、MK趋势性检验、最大化合成法和相关分析等常用数理统计方法,研究了内蒙古和蒙古国地区的植被覆盖变化和气候变化及其响应关系。结果表明:①近49年内蒙古和蒙古国地区年均气温显著上升,降水变化不明显。年均气温在空间上呈现出南高北低的空间分布格局,降水量表现出由西向东递增趋势。②空间分布上,内蒙的植被覆盖状况好于蒙古国。时间变化上,该地区植被覆盖变化分为2个阶段,1998—2001年NDVI呈整体退化趋势,2002—2012年波动上升,其中2009—2012年连续3a上升。空间变化上,内蒙古境内植被退化的区域主要集中在锡林郭勒盟周边地区,蒙古国境内退化的区域分布在中西部地区。③蒙古国境内荒漠和草原植被NDVI与降水呈正相关关系,与气温呈负相关。而对于内蒙古而言荒漠和草原植被的NDVI也与降水呈正相关关系,森林植被与气温呈正相关。就政策层面:内蒙古区域近年来受国家重大生态政策退耕还林、退牧还草的影响,大部分东部和西部植被恢复较快。在今后如果增强两国的文化和政策交流学习,将会对未来的游牧民族文化的保留和发展提供契机。     

近40年中国干旱特征及其对植被变化的影响

全球变暖影响下,中国干旱事件发生愈加频繁。过去半个世纪里,中国半干旱和半湿润地区的分界线总体南移,干旱面积呈增加趋势,因此了解中国干旱变化趋势对区域生态环境保护具有重要意义。基于GLASS数据产品、ERA5-Land数据,采用游程理论和多元线性回归等方法,探究1982—2018年间多尺度干旱事件基本特征(干旱持续时间、干旱严重度、干旱强度等),并分析植被生产力变化趋势,揭示干旱对植被变化的累积影响。结果表明：(1)新疆、青藏高原以及东南地区干旱较为严峻,而华中、华东大部分区域处于轻旱或无旱状态;(2)1982—2018年间,中国植被生产力整体呈改善态势,显著改善区集中在中国中部,而退化区集中在东南部、内蒙古和西藏南部;(3)中国大部分区域干旱与植被呈正相关,且干旱对植被多为累积影响,在干旱区和半干旱区尤为明显;(4)随着植被覆盖度的增加,植被与近短期尺度干旱的相关性也逐渐增加,由干旱区到湿润区,近短尺度干旱对植被变化的影响逐步增大。其中,SPEI-6(标准化降水蒸散发指数—中期尺度)对植被轻微变化累积影响最显著,而SPEI-12(标准化降水蒸散发指数—长期尺度)对植被显著变化累积影响更...     

我国三北地区植被变化的动因分析

地表植被变化是气候变化、人类活动等多种因素共同作的结果。然而,以往的研究要么集中在与气候变化有关的气象因素,要么集中在与人类活动有关的人为因素,鲜有基于长期数据监测下对自然与社会因素之间相互作用的定量评估。因此,气候变化和人为因素对地表植被变化的相互作用并不明确,各个因素对植被变化影响的量化贡献仍然不确定。为了评价生态修复项目对荒漠化防治的效果、以及在土地荒漠化防治中自然与社会因素对我国植被变化的影响、及其复杂的相互作用机理,该研究应用卫星遥感影像资料,通过面板数据混合回归模型大数据分析方法,计算了1983年至2012年气候变化和人类活动对我国北方地区植被变化的贡献率。结果表明,气候变化和人类活动对NDVI变化均有重要作用,其中人类活动对植被覆盖度变化的影响占58.2%—90.4%、气候变化占9.6%—41.8%;不同地区表现出不同的地理分异特征,并存在时滞效应。由此可见,荒漠化防治必须充分考虑不同因素的综合作用和地域特征,才能取得事半功倍的效果。研究结果较好地体现了卫星遥感影像资料在大尺度(省域尺度)下与社会经济统计指标的融合,为进一步中尺度(县域尺度)研究提供了方法借鉴。     

Species composition of coastal dune vegetation in Scotland has proved resistant to climate change over a third of a century

Climate change is expected to have an impact on plant communities as increased temperatures are expected to drive individual species' distributions polewards. The results of a revisitation study after c. 34 years of 89 coastal sites in Scotland, UK, were examined to assess the degree of shifts in species composition that could be accounted for by climate change. There was little evidence for either species retreat northwards or for plots to become more dominated by species with a more southern distribution. At a few sites where significant change occurred, the changes were accounted for by the invasion, or in one instance the removal, of woody species. Also, the vegetation types that showed the most sensitivity to change were all early successional types and changes were primarily the result of succession rather than climate‐driven changes. Dune vegetation appears resistant to climate change impacts on the vegetation, either as the vegetation is inherently resistant to change, management prevents increased dominance of more southerly species or because of dispersal limitation to geographically isolated sites.     

陕北气候变化与生态植被变迁

分析了128万年以来陕北气候变化及其生态植被变迁。结果表明,陕北黄土高原气候经历了多次冷、暖、干、湿的周期变化。陕北植被变迁在地质时期以及历史时期早期,主要由气候条件所控制,植被类型随气候的冷暖干湿变化而变迁。随着人类活动的加剧,气候条件不再是影响植被变迁的唯一因素,人类活动对植被的影响愈来愈明显。明清时期,气候冷干,旱灾频繁．陕北生态环境脆弱,大规模垦殖和滥烧使自然植被迅速减少,陕北自然植被遭到毁灭性破坏。20世纪50年代,陕北逐步开始生态环境治理,在对生态环境治理的同时,又对部分地区自然植被进行破坏。20世纪80年代以后,生态环境总体上趋于好转。     

110000 years of Quaternary beetle diversity change

Our first aim was to document the effects of palaeotemperatures and vegetation changes on beetle assemblages, and secondly to determine the extent to which surrogacy analysis at the family taxonomic level reveals patterns evident from lower taxa analysis. The sedimentary sequence sampled on the experimental site of La Grande Pile (Vosges, France) covers the whole of the last climatic cycle. Beetle fragments were extracted from 39 coring samples and identified to the lowest possible taxonomic level. A total of 3092 beetle specimens belonging to 394 taxa were identified, more than half to species level. Carabidae, Staphylinidae and Curculionidae families together represented 40% of the overall taxa richness. Beetle taxa richness and assemblage composition varied markedly over time. Average summer temperatures clearly play a major role in diversity patterns, as temperature was positively correlated with taxon richness. Nevertheless, the warmest and the coldest periods were not the richest and the poorest, respectively, and the most humid period did not correspond to maximum beetle richness. Beetle assemblages are likely to fluctuate in response to other factors such as plant diversity and vegetation structure. Steppe-like vegetation did not reduce species richness while dense, homogenous and closed forests did. Family patterns mirrored those observed at the lower taxa level. This makes the family level a convincing alternative to lower taxonomic level analyses by representing a faithful picture of changing beetle diversity over a long period of time. Finally, evolution of beetle diversity over the Quaternary represents a convincing model for evaluating the effect of close and wide past climate changes, and for assisting in management of present-day biodiversity as part of the current anthropogenic global climate change.     

喀斯特流域径流对植被和气候变化的多尺度响应

植被覆盖和气候变化对径流的影响可能具有尺度依赖性,而在生态环境脆弱和地质结构复杂的西南喀斯特区开展研究较少。为此,以喀斯特地貌广泛发育的西江流域为研究区,选取郁江、红水河、浔江和梧州4个流域,利用Mann-Kendall趋势检验对4个流域年径流深、NDVI、降水量、潜在蒸散发和气温(1982—2015)的变化趋势进行了分析,运用多元经验模态分解(MEMD)量化了流域径流深与植被和气候因子在不同尺度上的相关性,并预测了年径流深,旨在研究喀斯特流域径流对植被和气候变化的多尺度响应。结果表明,径流深仅有红水河流域呈显著下降趋势(P<0.05)。其中郁江流域径流深主要表征尺度为3年和5年,红水河流域径流深主要表征尺度为10年和22年,浔江和梧州流域径流深主要表征尺度为3年和22年。径流深与植被和气候因子的关系具有尺度依赖性,在不同尺度下,4个流域径流深与降水量和潜在蒸散发始终呈显著相关性(P<0.05),而径流深与NDVI和气温的多尺度关系在某些表征尺度上并不显著。利用MEMD法对径流深的预测效果(R²=0.81—0.86)要优于基于原始数据的多元逐步回归方法...     

近17年陕西榆林植被指数的时空变化及影响因素

植被指数是研究区域植被变化的重要手段。基于MODIS/Terra NDVI遥感影像数据,对陕西榆林市2000—2016年8月份NDVI进行像元尺度的时空变化及影响因素分析。结果表明,榆林有96.44%的区域植被指数是增加的,增加值在0—0.02/a区域面积占榆林的93.63%,呈显著增加趋势的面积占榆林的80.72%。复直线回归分析显示,气象因素对植被生长、演化起到了促进作用,人类活动使得植被指数等级变得更加均匀。人类活动抑制植被生长演化的区域占榆林总面积的45.04%,主要分布在榆林市最北部的府谷县、榆林市南部及西部的大部分区域;人类活动促使植被指数增加的区域占榆林总面积的54.96%,说明有一半以上的区域,人类活动对植被生长起到了促进作用,这些地区的封山育林、退耕还林、退牧还草等措施的实施效果较好。     

Seasonal change in the redox property of peat and its relation to vegetation in a system of floating mat and pond

A relationship was sought between species distribution and seasonal change in the redox property of peat in a floating mat in Mizorogaike Pond, central Japan. The mat surface experienced an annual submergence-emergence cycle due to its sinking-rising movement. Redox potential (Eh) of the surface peat showed little difference between communities in the mat in the submergence season (January–June) and early emergence season (July–August). However variation in Eh among communities was clear in the late emergence season (September–December). Among seven communities in the floating mat, theMenyanthes trifoliata-Rhynchospora fauriei, M. trifoliata-Eriocaulon sikokianum-E. bondoense f.pilosum, Sphagnum cuspidatum andM. trifoliata-Carex thunbergii communities had high Eh (400–600 mV) in the late emergence season, while theMenyanthes trifoliata andPhragmites australis-M. trifoliata communities had lower Eh (200–400 mV). TheM. trifoliata-Isachné globosa community was intermediate (300–500 mV). The earlier the emergence of the peat surface began, the higher the Eh became in the late emergence season.     

黄土高原不同植被覆被类型NDVI对气候变化的响应

植被与气候是目前研究生态与环境的重要内容。为探究黄土高原地区植被与气候因子之间的响应机制,利用线性趋势分析、Pearson相关分析、多元线性回归模型以及通径分析的方法,对黄土高原2000—2015年全区和不同植被覆被类型区内NDVI与气候因子的变化趋势以及相互作用关系进行分析。植被覆被分类数据和植被指数数据分别来源于ESA CCI-LC(The European Space Agency Climate Change Initiative Land Cover)以及MODND1T/NDVI(Normalized Difference Vegetation Index)。结果表明:(1) 2000—2015年黄土高原全区植被年NDVI_(max)显著增加的区域占总面积的74.25%,不同植被覆被类型年NDVI_(max)分别为常绿阔叶林常绿针叶林落叶阔叶林落叶针叶林镶嵌草地农田镶嵌林地草地灌木,并且都呈显著增加趋势,其中常绿阔叶林和农田增加幅度最大,为0.012/a。(2)黄土高原全区NDVI与气温、日照、降水和相对湿度等气候因子之间没有显著相关性,但在不同植被覆被类型区,气候因子对NDVI存在显著作用,且不同植被覆被类型差异明显。(3)在全区和不同植被覆被类型区NDVI仅对降水的响应比较一致,气温无论在整个区域尺度还是不同植被覆被类型区对植被的影响均不显著。(4)常绿阔叶林、落叶阔叶林、常绿针叶林及镶嵌林地等以乔木为主的植被覆被类型受年均相对湿度和年总日照时数的显著负效应驱动,草地、镶嵌草地等以草本为主的植被覆被类型则受到年总降水量的显著正效应影响。这说明对植被类型进行区分,更有利于揭示气候对植被的作用机制。     

西双版纳地区主要森林植被乔木多样性的时间变化

为了评估云南省西双版纳森林植被乔木多样性的时间变化,该研究通过样方调查收集了该地区4种主要森林植被(热带雨林、热带季节性湿润林、热带山地常绿阔叶林和暖热性针叶林)乔木多样性数据,结合遥感影像提取了该地区4种森林植被在1992年、2000年、2009年和2016年4个时期的分布,用Simpson、Shannon-Wiener和Scaling物种多样性指数对比4种森林植被乔木均匀度差异,并利用Scaling生态多样性指数和灰色关联评价模型,评估该地区在4个时期的森林乔木多样性的时间变化。结果表明:(1)森林面积比例变化有先减少后增加的趋势,表现为由1992年的65.5%减少至2000年的53.42%,减少到2009年的52.49%,再增至2016年的54.73%,但热带雨林呈现持续减少的趋势。(2) 4种森林植被对乔木多样性的贡献有明显差异,均匀度排序是热带雨林>热带山地(低山)常绿阔叶林>暖热性针叶林>热带季节性湿润林,丰富度排序是热带雨林>热带山地(低山)常绿阔叶林>热带季节性湿润林>暖热性针叶林,对乔木多样性贡献的排序是热带雨林>热带山地(低山)常绿阔叶林>热带季节性湿润林>暖热性针叶林。(3)热带雨林和热带季节性湿润林乔木多样性呈现持续减少趋势,4个时期西双版纳森林植被乔木多样性排序为1992年>2009年> 2016年> 2000年。以上结果表明经济活动是影响西双版纳生物多样性的重要原因,保护热带雨林对维持该地区生物多样性具有重要意义。