Detecting human impact in the pollen record using data-model comparison

Palaeoecological data are compared with output from climate-driven forest simulation models to separate human influence as a driver of vegetation dynamics from other drivers such as climatic change. The transition from Tilia cordata to Fagus sylvatica dominance in a small forest hollow in Denmark was not predicted by a climate-driven forest simulation model and could be ascribed to anthropogenic impact. This transition can be upscaled to a large region of north-west Europe and contributes to a data-model mismatch for the European distribution of Fagus 6,000 years ago. A data-model mismatch for Picea abies during the last few centuries in southern Scandinavia can also be attributed to anthropogenic impact. Combining pollen data and vegetation models can help with the important task of upscaling from the scale of the forest stand, where anthropogenic impact is readily detectable, to regions and continents, where it is more challenging to distinguish anthropogenic impact from the impacts of climatic change.     

Danish forest development during the last 3000 years reconstructed from regional pollen data

Most present Danish forest types are a direct result of recent silvicultural practice. We use fossil pollen data converted into estimates of tree abundance to map the development of forest types during the last 3000 radioearbon yr. The forest types were clusters in an artificial neural network based on all available European Holocene pollen data. Diverse deciduous forest types found 3000 yr ago were replaced by less diverse Fagus -dominated types over a period of 2000 yr. The present day map contained many new combinations of tree species, dominated by Picea and Pinus. The association between the increase in non-forest communities and establishment of Fagus suggests that anthropogenic activity has accelerated the loss of species-rich deciduous forest with abundant .Alnus, Corylus, Quercus and Tilia. We conclude that the natural forest composition of Denmark would be deciduous forest today with a significant presence of Fugus sylvatica. Recent forest development has created a break in compositional continuity with the past that is unnatural and has posed problems for forest-dependent biota.     

The effect of climate conditions on inter-annual flowering variability monitored by pollen traps below the canopy in Draved Forest, Denmark

Since 1967 annual pollen deposition has been monitored in the semi-natural mixed deciduous woodland Draved Forest by the Geological Survey of Denmark. In this paper, we analyse the variability in pollen accumulation rates for the eight most common deciduous trees, and their relationships to monthly temperature and precipitation. High summer temperatures in the year before flowering have a positive effect on pollen deposition for several species. A positive correlation between temperatures during the flowering season and pollen accumulation rates is found for Fagus sylvatica, Quercus robur, Fraxinus excelsior and Corylus avellana. The amount of precipitation can have both positive and negative effects on pollen accumulation, depending on species and on time of year. Linear modelling showed that combinations of monthly climate parameters could explain between 10 and 80% of the variation observed in different species. There were marked differences in the time series of pollen accumulation and pollen/climate relationships for some species between traps within the forest related to the location of trees near the traps. This underlines the importance of using multiple traps in a region for this type of study. Time series analyses were used to test for cyclicity in pollen accumulation rates, which could be caused by resource limitations or internal biological factors. No significant autocorrelations were found, although Alnus glutinosa showed a tendency towards 3-year cyclicity. These results indicate that, with the possible exception of Alnus glutinosa, temperature and precipitation are the main factors controlling the annual variability in pollen deposition of the trees in Draved Forest.     

Tree Species Composition and Harvest Intensity Affect Herbivore Density and Leaf Damage on Beech,Fagus sylvatica,in Different Landscape Contexts

Most forests are exposed to anthropogenic management activities that affect tree species composition and natural ecosystem processes. Changes in ecosystem processes such as herbivory depend on management intensity, and on regional environmental conditions and species pools. Whereas influences of specific forest management measures have already been addressed for different herbivore taxa on a local scale, studies considering effects of different aspects of forest management across different regions are rare. We assessed the influence of tree species composition and intensity of harvesting activities on arthropod herbivores and herbivore-related damage to beech trees, Fagus sylvatica, in 48 forest plots in three regions of Germany. We found that herbivore abundance and damage to beech trees differed between regions and that – despite the regional differences - density of tree-associated arthropod taxa and herbivore damage were consistently affected by tree species composition and harvest intensity. Specifically, overall herbivore damage to beech trees increased with increasing dominance of beech trees – suggesting the action of associational resistance processes – and decreased with harvest intensity. The density of leaf chewers and mines was positively related to leaf damage, and several arthropod groups responded to beech dominance and harvest intensity. The distribution of damage patterns was consistent with a vertical shift of herbivores to higher crown layers during the season and with higher beech dominance. By linking quantitative data on arthropod herbivore abundance and herbivory with tree species composition and harvesting activity in a wide variety of beech forests, our study helps to better understand the influence of forest management on interactions between a naturally dominant deciduous forest tree and arthropod herbivores.     

Danish deciduous forest types

In this study, the first comprehensive multivariate statistical analysis of Danish native forest vegetation, based on 1768 sample plots, is presented. Data were composed of data from literature sources and newly collected data. A series of cluster analyses resulted in 24 forest community types, grouped in beech (Fagus sylvatica), oak (Quercus robur-Q. petraea), hornbeam (Carpinus betulus), alder-ash (Alnus-Fraxinus) and lime (Tilia cordata, T. platyphyllos) types, in addition to mixed forest communities with several co-dominant tree species. The described communities are provisionally arranged syntaxonomically, when possible, according to the international phytosociological system. The distribution of ecological indicator values of pH, soil moisture and nitrogen is gradual in relation to the perceived plant communities. Many forest types, such as beech and oak dominated types, obtain indicated values for pH that span most of the indicated gradient. It is suggested that natural Danish forests probably would be composed of a multitude of canopy forming tree species. The present stands with one or a few tree species forming the canopy is the result of long anthropogenic influence and selective logging.     

Hybridization among Tilia cordata and T. platyphyllos (Tiliaceae) in Denmark

Morphological evidence of hybridization among Tilia cordata and T. platyphyllos is presented in plots of principal components analysis (PCA) and Wells' distance diagrams, the latter based on differently weighted characters. Putative hybrids from both natural and planted stands in Denmark are studied. Plausible hybrids found by running Estabrook's HYWIN program on the data are almost identical with those found by PCA and the weighted Wells' distance coefficient.     

Growth–mortality relationships as indicators of life-history strategies: a comparison of nine tree species in unmanaged European forests

Forest succession depends strongly on the life history strategies of individual trees. An important strategic element is the ability to survive unfavourable environmental conditions that result in strongly reduced tree growth. In this study, we investigated whether the relationship between growth and mortality differs among tree species and site conditions. We analysed 10 329 trees of nine tree species (Picea abies , Taxus baccata , Fagus sylvatica , Tilia cordata , Carpinus betulus , Fraxinus excelsior , Quercus robur , Betula spp. and Alnus glutinosa ) from unmanaged forests of Europe: the continental Białowieża forest (Poland) and several oceanically influenced Swiss forest reserves. For each species, we calculated a set of flexible logistic regression models with the explanatory variables growth (as measured by relative basal area increment), tree size and site. We selected the species-specific model with the highest goodness-of-fit and calculated its discriminatory power (area under the receiver operating characteristic curve, AUC) and calibration measures. Most models achieved at least a good discriminatory power (AUC>0.7) and the AUC ranged from 0.62 to 0.87; calibration curves did not indicate any overfitting. Almost all growth–mortality relationships differed among species and sites, i.e. there is no universal growth–mortality relationship. Some species such as F. excelsior showed reduced survival probabilities for both unfavourable and very good growth conditions. We conclude that the growth–mortality relationships presented here can contribute to the life-history classification of trees and that they should also help to improve projections of forest succession models.     

Recent successional processes investigated by pollen analysis of closedcanopy forest sites

Forest succession was investigated by pollen analysis of two mor-humus sections and of peat from a 3 m-diameter hollow under mixed conifer-hardwood forest in north-central Massachusetts, USA. The humus profiles recorded a major forest perturbation caused by the removal of Castanea dentata by the chestnut blight (1910–1912), and the peat from the hollow extended the record beyond the time of colonial settlement (1733). Fagus grandifolia was a forest dominant before 1733 but declined abruptly upon settlement. Castanea, a late Holocene immigrant to the area, rapidly increased its pollen representation after settlement until the epidemic of the chestnut blight. Forest succession following the loss of Castanea involved the successive rise to dominance of Betula, Quercus, Acer rubrum, and Tsuga canadensis. These vegetational changes conform to observations made during studies of forest-stand composition by other workers. Allogenic factors such as logging, disease, and wind have initiated major compositional change, which has been modified by autogenic successional processes such as the gradual rise to dominance of Tsuga canadensis around one of the humus sections. The two humus sites resolve fine-scale pattern in former vegetation such as differences in the distribution of Pinus strobus and Castanea over 200 m, the distance between the mor-humus sites. These within-forest sites permit investigations of fine-scale vegetational patterns and processes that are of interest to forest ecologists.     

Vegetation structure and diversity of an ancient temperate deciduous forest in SW Denmark

Bolderslev Skov (113 ha) is the largest contiguous ancient forest remnant in Denmark. The forest has been preserved since 1998 as a strict non-intervention forest reserve. We studied vegetation structure, floristic gradients, and diversity of the forest in 50 plots of 100 m² placed according to a restricted random sampling design. Dominant tree species were Fagus sylvatica, Fraxinus excelsior, Tilia cordata and Quercus robur, which in most parts of the forest form a mixed canopy. Most stands appeared to be of moderate age, 55-80 years old, and large old trees were rare. pH in association with light and thickness of the litter layer were the most important factors in explaining floristic gradients in the forest. Soil moisture (dry to mesic) was not strongly correlated with DCA axes for neither tree nor field layer, but had a significant effect on the distribution of a number of herb species. Forest structure was not important in explaining species distributions. Field layer species richness showed a positive relationship with the pH-gradient. At the scale of 1m² plots we also found a highly significant negative relationship between field layer species richness and the plot-wise Ellenberg indicator value for nitrogen availability. Structure of the tree layer had little effect on field layer species richness. The mixed composition, long continuity, and presence of a high proportion of the regional species pool assigns a high conservation value to Bolderslev Skov and makes it an important site for future studies of the dynamic properties, niche preferences, and inter-specific competition of temperate deciduous forest species. This revised version was published online in June 2006 with corrections to the Cover Date.     

Tree and stand-scale factors affecting richness and composition of epiphytic bryophytes and lichens in deciduous woodland key habitats

Conservation and sustainable forestry are essential in a multi-functional landscape. In this respect, ecological studies on epiphytes are needed to determine abiotic and biotic factors associated with high diversity. The aim of the present study was to evaluate relative sensitivity of conservation targets (epiphytic bryophytes and lichens) in relation to contrasting environmental variables (tree species, tree diameter at breast height, bark crevice depth, pH, tree inclination, pH, forest stand age, area and type) in boreo-nemoral forests. The study was conducted in Latvian 34 woodland key habitat (WKH) boreo-nemoral forest stands. Generalized linear mixed models and canonical correspondence analysis showed that tree species and tree bark pH were the most important variables explaining epiphytic bryophyte and lichen composition and richness (total, Red-listed, WKH indicator species). Forest stand level factors, such as stand size and habitat type, had only minor influence on epiphytic species composition and richness. The results of the present study indicate a need to maintain the diversity of tree species and large trees, particularly Acer platanoides, Carpinus betulus, Fraxinus excelsior, Populus tremula, Tilia cordata, Ulmus glabra and Ulmus laevis in conservation of epiphytic bryophyte and lichen communities in the future.     

野生人参自然分布的典型原始阔叶红松林群落及其特征研究

本文通过物种多样性指数、生态优势度、群落均匀度、重要值等指标综合分析了野生人参自然分布的典型椴树阔叶红松林的群落特征．结果认为椴树阔叶红松林内物种数及其个体数量较多,多样性指数及群落的均匀度都较高,物种分布均匀并具有明显的层次,生态优势度较低,具有较稳定的群落结构．这种群落特征给人参的生活和生长创造了适宜的生态条件,是人参这一古老遗植物在这种群落中得以长期保存和生长繁衍的主要因素．     

Evaluating the effects of climate change on tree species abundance and distribution in the Italian peninsula

Question: What is the effect of climate change on tree species abundance and distribution in the Italian peninsula? Location: Italian peninsula. Methods: Regression tree analysis, Random Forest, generalized additive model and geostatistical methods were compared to identify the best model for quantifying the effect of climate change on tree species distribution and abundance. Future potential species distribution, richness, local colonization, local extinction and species turnover were modelled according to two scenarios (A2 and B1) for 2050 and 2080. Results: Robust Random Forest proved to be the best statistical model to predict the potential distribution of tree species abundance. Climate change could lead to a shift in tree species distribution towards higher altitudes and a reduction of forest cover. Pinus sylvestris and Tilia cordata may be considered at risk of local extinction, while the other species could find potential suitable areas at the cost of a rearrangement of forest community composition and increasing competition. Conclusions: Geographical and topographical regional characteristics can have a noticeable influence on the impact of predicted climate change on forest ecosystems within the Mediterranean basin. It would be highly beneficial to create a standardized and harmonized European forest inventory in order to evaluate, at high resolution, the effect of climate change on forest ecosystems, identify regional differences and develop specific adaptive management strategies and plans.     

The origin of present forest composition and pattern in southern Sweden

Abstract. Deciduous forests in much of southern Sweden are often located on former ‘in-field’ sites close to farms and villages. The more distant ‘out-field’ sites are almost always dominated by conifers. Using palaeecological methods, we investigate the origin of this forest pattern at a small estate in Småland, southern Sweden that was the birthplace of Carl Linnaeus. Prior to extensive permanent settlement (c.ad 1100) both in-fields and out-fields supported a rich, mixed deciduous forest that was irregularly ravaged by forest fire. After ad 1100 the in-field site was transformed into a species-rich forest-meadow system with tree composition similar to the pre-cultural state with the addition of Fagus sylvatica L. The out-field sites were used for grazing and slash-and-burn agriculture, but nevertheless maintained a high degree of forest continuity. Forest composition however changed from deciduous to coniferous dominance. Floristic diversity is closely linked to human activity. Herbaceous diversity is greatest during the earliest phase of the forest-meadow system. It declines during the late-mediaeval agrarian crisis and again during the over-exploitation of the late nineteenth century. Diversity returns to pre-cultural levels after the abandonment of the forest-meadow system during the present century. Present forest composition and pattern in the study area are closely related to former human activities and are not primarily a function of soil type or present-day management.     

孟家岗林场森林景观结构动态分析

以黑龙江省孟家岗林场1989年和2006年两期森林资源二类调查数据为基础,结合林相图,利用GIS技术和景观格局分析软件包FRAGSTATS进行分析,提取森林景观要素内部结构指标等景观指数,并对孟家岗林场近20年的景观格局的动态特征进行了系统的分析。研究结果表明：由于孟家岗林场森林景观要素类型的增加以及多样性和优势度指数的增高,使得森林景观的分离度和破碎度也在增加;虽然落叶松林为该研究区域的优势景观要素类型,但其优势度却在逐渐降低,表明落叶松景观要素在向其它景观要素类型转化;首次对孟家岗林场进行景观内部结构指数分析,表明阔叶树和混交林景观要素类型是以成、过熟林为主,三大主要针叶树种以中龄林和近熟林为主。人为干扰的加剧,使针叶林年龄结构趋于单一化。     

Niche characteristics of Danish woody species as derived from coenoclines

Abstract. A main floristic coenocline is extracted from a Danish forest vegetation data set with Detrended Correspondence Analysis. Huisman‐Olff‐Fresco (HOF) modelling of 262 species occurrences relative to site scores along the coenocline is compared with Gaussian and Generalized Linear Modelling. HOF models allow for responses of variously skewed forms, which may result from interspecific interactions. Most species have symmetric (60%) or skewed (29%), and only few species have flat or monotone response curves. This provides evidence for the generality of unimodal plant species response curves, provided the gradient in question comprises a sufficient amount of compositional turnover. The Gaussian niche width is correlated with density of optima and probability of occurrence of the species. Detailed analysis of HOF estimates for 28 woody species indicates that early succession species such as Pinus sylvestris and Populus tremula have wider niches than middle to late successional canopy species such as Alnus glutinosa, Carpinus betulus, Fagus sylvatica, Fraxinus excelsior, Quercus robur and Tilia cordata. A marked overlap in niche range along the coenocline is interpreted in terms of species competition. Rubus idaeus intrudes into the niches of all other shrub species. Several canopy tree species, such as Fagus sylvatica, Fraxinus excelsior and Quercus robur overlap more than 60% of the ranges of all other species, while their internal overlaps are fairly equal, presenting evidence for their likely co‐existence given more natural forest conditions. The combined analysis of coenoclines with HOF modelling of species behaviour is the most robust among the compared methods for estimating model parameters and niche characteristics of plant species. It is recommended for future ecological studies.     

择伐对吉林蛟河阔叶红松林群落结构及动态的影响

科学的森林经营能够优化林分结构,是调控森林生产力和生物多样性的有效手段。择伐作为森林经营的重要方式之一,其对森林结构以及群落动态的影响一直未有定论,因此迫切需要利用更加全面的数据对择伐及伐后林分特征的变化进行长期监测。根据森林大样地建立规范,2010年在吉林蛟河建立了42hm~2阔叶红松林动态监测样地,2011年冬季截取部分面积进行择伐经营,以经营样地为研究对象,运用数值变量描述采伐活动并分析择伐前后群落结构的变化;同时结合2015年的二次调查数据,以立地条件基本一致的对照样地为参照,比较林分水平和物种水平上死亡率、更新率的差异,并利用线性混合效应模型探究择伐活动对个体径向生长的影响。研究结果显示:经营样地的择伐强度为5.4%,受采伐干扰影响较大的物种主要包括色木槭、白牛槭、裂叶榆、胡桃楸、千金榆、水曲柳以及紫椴,采伐主要集中于林冠层树种,亚林层和灌木层个体很少涉及。择伐前后物种组成、径级结构等并未发生明显改变。5年间,经营样地和对照样地的林分密度都降低,对比对照样地,经营样地的死亡率较低,但其更新状况并未优于对照样地。从胸高断面积来看,经营样地整体的年平均生长量高于对照样地,表明择伐导致的稀疏对个体生长和存活起到了一定的促进作用。将采伐强度纳入线性混合效应模型中分析发现,胸径始终是影响个体生长的最重要因素,其次是树木个体之间的非对称竞争;采伐所涉及到的7个主要树种的年平均生长量均高于对照样地,但仅有紫椴的径向生长表现出对采伐干扰的显著响应。综合来看,低强度择伐对群落结构和动态的影响较小,不同物种的径向生长对择伐的响应存在一定差异。     

Pollen from Lake Sedmo Rilsko reveals southeast European postglacial vegetation in the highest mountain area of the Balkans

A lacustrine sequence from Lake Sedmo Rilsko (altitude 2095 m) in the northwest of Rila Mountain, Bulgaria, was analysed on the basis of 84 pollen spectra and three ¹⁴C accelerator mass spectrometry dates. The lower part of the sequence (413–530 cm) corresponds to the Late-glacial. Three phases, two stadial and one interstadial, are characterized by the dominance of mountain–steppe herb vegetation composed of Artemisia , Chenopodiaceae and Poaceae, with single trees of Pinus and shrub land of Juniperus and Ephedra . The identification of pollen grains of Abies , Quercus robur -type, Corylus , Acer , Fagus and other mesophilous trees suggests that they survived the harsh Late-glacial conditions in refuges below an altitude of 1000 m, where moisture was sufficient for their growth. In the early Holocene period, Betula forests at high altitudes and, below them, closed deciduous forests with Quercus , Tilia , Ulmus and Corylus , occurred from 11800 until approx. 6700 cal. BP. The formation of the coniferous belt dominated by Pinus sylvestris , Pinus peuce and Abies alba lasted from between 6700 and 5000 cal. BP. The forest dynamics in the Subboreal and the Subatlantic ended with the invasion of Fagus sylvatica and Picea abies after approx. 4500 and 3300 cal. BP, respectively. Indications of anthropogenic activities, expansion of agriculture in the lowland foothills, and livestock grazing in the mountain meadows and pastures, are clearly evident from the pollen diagram from 2400 cal. BP onwards.     

天保工程实施以来东北阔叶红松林的可持续经营

20世纪末以来有两个重要的变化影响着东北温带阔叶红松林资源的可持续性,一是天然林资源保护工程(下称天保工程)的实施,另一个是红松不再作为用材树种被采伐。但森林采伐后的更新造林模式并没有显著改变。以长白山腹地-露水河林业局的阔叶红松林为研究对象,利用森林资源清查(二类)和作业设计调查(三类)资料,评估了这两个重要的变化对当前的森林资源的产生影响。结果表明,天保工程的实施调减了采伐量,间接提高了森林的公顷蓄积量,整体上促进了森林资源的恢复。目前,紫椴,蒙古栎,水曲柳和春榆等占商品材总生产量94.7%(蓄积量)。与此同时,可供采伐的这4个树种年生长量却小于采伐量,而林下补植红松,却忽视阔叶树更新的经营模式势必会逐渐增加红松在阔叶红松林中的比例,使目前商品材资源不足的情况更加恶化。总的来说,天保工程促进了公益林区森林资源的可持续性,但降低了用于木材生产的商品林的面积;红松不采伐增加了红松在商品林中的比例,降低了商品林中用材树种比例和商品材的可持续生产能力,从长期看,必然导致可采伐林木资源的枯竭。据此,建议应根据森林培育的目标,选择合适的森林更新恢复模式。     

New Tuber species found in Poland

New information from a survey of truffles carried out in southern part of Poland in September 2007 is presented. The fruit bodies of Tuber aestivum, T. excavatum, T. rufum and one unidentified Tuber sp. were found. The soil chemistry of the five T. aestivum sites was analysed. Our inventory showed that T. aestivum prefers the mixed forest with host-trees such as: Quercus robur, Corylus avellana, Carpinus betulus, Fagus silvaticus and Tilia cordata. Selection of local inocula of T. aestivum for the propagation of truffles production could be an alternative to the Mediterranean truffles orchards in times when demand for the fungi will be increasing. Fruit bodies of truffles are conserved in the collection of biological material in the Forest Research Institute in Sękocin Stary.     

MALDI-TOF mass spectrometry and PSD fragmentation as means for the analysis of condensed tannins in plant leaves and needles

MALDI-TOF mass spectrometry and 13C NMR spectroscopy were applied to unveil typical characteristics of condensed tannins of leaves and needles from willow (Salix alba), spruce (Picea abies) and beech (Fagus sylvatica) of three tree species that are ubiquitous in German forests and landscapes. For further evaluation, lime (Tilia cordata) was included. The 13C NMR spectroscopy confirmed the purity of the condensed tannin fractions and the efficiency of the procedure used for their extraction. While signals representative for procyanidin units are observable in all liquid-state 13C NMR spectra, resonance lines of prodelphinidin were only detected in those obtained from the condensed tannins of spruce needles and beech leaves. Typical signals in the chemical shift region between 70 and 90 ppm demonstrated the presence of stereoisomers (catechin/epicatechin; gallocatechin/ epigallocatechin). The MALDI-TOF mass spectra of the condensed tannins show signals of polymers of up to undecamers. Supporting the observations from the NMR spectroscopy, the mass spectra of the willow and lime leaf condensed tannins were identified as polymers with mainly procyanidin units, while the polymers of the spruce needle and beech leaves exhibit varying procyanidin/prodelphinidin ratios. Post source decay (PSD) fragmentation lead to a sequential loss of monomers and allowed a detailed characterization and sequencing of individual chains. In the case of the condensed tannins of lime this technique clearly excludes a pelargonidin terminal unit followed by a prodelphinidin unit, which would result in the same molecular masses as a polymer solely built up of procyanidin units.