Changes In Forest Composition Research Articles

Changes in forest structure and composition in a successional tropical dry forest

We describe changes in forest structure and floristic composition of three successional stages for Mata Seca State Park, in Minas Gerais, Brazil, through the measurement of all trees greater than 5 cm of diameter at breast height (DBH) of 18 permanent plots (6 per stage) for early, intermediate, and late successional stages of a tropical dry forest during a 5-year period. Using this information, we calculated the Importance Value Index (IVI), Holdridge Complexity Index, Jaccard Similarity Coefficient, and Shannon Diversity Index for each stage of succession. The floristic composition and structure of the successional stages expressed by the Holdridge Complexity Index, showed that complexity increases gradually as we advance through the successional stages, while the Shannon Diversity Index indicated that species diversity was higher in the intermediate stage of succession. The Jaccard Similarity Coefficients showed that the intermediate and late successional stages had high similarity, whereas the early successional stage had low similarity with these two successional stages. Mortality rates were higher in the early stage, especially in stems with smaller diameters (5-10cm). This information contributes to the dissemination of important knowledge for the conservation of the tropical dry forests of Brazil, which are the most threatened ecosystems in this country and, at the same time, the least studied.

A new Neotibicen cicada subspecies (Hemiptera: Cicadidae) from the southeastern USA forms hybrid zones with a widespread relative despite a divergent male calling song.

A morphologically cryptic subspecies of Neotibicen similaris (Smith and Grossbeck) is described from forests of the Apalachicola region of the southeastern United States. Although the new form exhibits a highly distinctive male calling song, it hybridizes extensively where it meets populations of the nominate subspecies in parapatry, by which it is nearly surrounded. This is the first reported example of hybridization between North American nonperiodical cicadas. Acoustic and morphological characters are added to the original description of the nominate subspecies, and illustrations of complex hybrid song phenotypes are presented. The biogeography of N. similaris is discussed in light of historical changes in forest composition on the southeastern Coastal Plain.

The movement of pre-adapted cool taxa in north-central Amazonia during the last glacial

The effects of climate change on the lowland vegetation of Amazonia during the last glacial cycle are partially known for the middle and late Pleniglacial intervals (late MIS 3, 59–24 ka and MIS 2, 24–11 ka), but are still unclear for older stages of the last glacial and during the last interglacial. It is known that a more seasonal dry-wet climate caused marginal forest retraction and together with cooling rearranged forest composition to some extent. This is observed in pollen records across Amazonia depicting presence of taxa at glacial times in localities where they do not live presently. The understanding of taxa migration is hindered by the lack of continuous interglacial-glacial lowland records. We present new data from a known locality in NW Amazonia (Six Lakes Hill), showing a vegetation record that probably started during MIS 5 (130–71 ka) and lasted until the onset of the Holocene. The vegetation record unravels a novel pattern in tree taxa migration: (1) from the beginning of this cycle Podocarpus and Myrsine are recorded and (2) only later do Hedyosmum and Alnus appear. The latter group is largely restricted to montane biomes or more distant locations outside Amazonia, whereas the first is found in lowlands close to the study site on sandy soils. These findings imply that Podocarpus and Myrsine responded to environmental changes equally and this reflects their concomitant niche use in NW Amazonia. Temperature drop is not discarded as a trigger of internal forest composition change, but its effects are clearer later in the Pleniglacial rather than the Early Glacial. Therefore early climatic/environmental changes had a first order effect on vegetation that invoke alternative explanations. We claim last glacial climate-induced modifications on forest composition favoured the expansion of geomorphologic-soil related processes that initiated forest rearrangement.

Seed dispersal of Diospyros virginiana in the past and the present: Evidence for a generalist evolutionary strategy

Several North American trees are hypothesized to have lost their co‐evolved seed disperser during the late‐Pleistocene extinction and are therefore considered anachronistic. We tested this hypothesis for the American persimmon (Diospyros virginiana) by studying the effects of gut passage of proposed seed dispersers on seedling survival and growth, natural fruiting characteristics, and modern animal consumption patterns. We tested gut passage effects on persimmon seeds using three native living species, the raccoon (Procyon lotor), Virginia opossum (Didelphis virginiana), and coyote (Canis latrans), and two Pleistocene analogs; the Asian elephant (Elephas maximus) and alpaca (Vicugna pacos). Persimmon seeds excreted by raccoons, coyotes, and elephants survived gut transit. Gut passage did not affect sprouting success, but did tend to decrease time to sprout and increase seedling quality. Under field conditions, persimmon fruits were palatable on the parent tree and on the ground for an equal duration, but most fruits were consumed on the ground. Seven vertebrate species fed upon persimmon fruits, with the white‐tailed deer (Odocoileus virginianus)—a species not capable of dispersing persimmon seeds—comprising over 90% of detections. Conversely, potential living seed dispersers were rarely detected. Our results suggest the American persimmon evolved to attract a variety of seed dispersers and thus is not anachronistic. However, human‐induced changes in mammal communities could be affecting successful seed dispersal. We argue that changes in the relative abundance of mammals during the Anthropocene may be modifying seed dispersal patterns, leading to potential changes in forest community composition.

A three decade assessment of climate‐associated changes in forest composition across the north‐eastern USA

Summary Climate‐associated changes in forest composition have been widely reported, particularly where changes in abiotic conditions have resulted in high mortality of sensitive species and have disproportionately favoured certain species better adapted to these newer conditions. In the north‐eastern USA and south‐eastern Canada, few studies have examined climate‐related influences associated with forest composition, and none have considered broad‐scale changes over a long temporal (>25 years) period. We used US Forest Service Forest Inventory and Analysis data from 1983 to 2014 across four north‐eastern states (Maine, New Hampshire, New York and Vermont) to assess temporal and spatial changes in the occurrence and abundance of American beech Fagus grandifolia Ehrh, sugar maple Acer saccharum L., red maple Acer rubrum L. and birch Betula spp. saplings. We also tested the effects of biotic and abiotic factors on the distribution of the four studied deciduous species over the entire period examined. Occurrence and abundance of American beech have increased substantially over the past three decades, whereas the occurrence and abundance of three other deciduous species have decreased in all ecological provinces of the north‐eastern USA, except the Midwest Broadleaf ecological province. Consequently, a clear shift in species composition is currently underway in the beech‐maple‐birch (BMB) forests of the north‐eastern USA, with uncertain consequences for future ecosystem structure and function. In the studied region and over the entire period examined, the distribution of increased occurrence and abundance of beech relative to the three other deciduous species were associated with higher temperature and precipitation as well as higher conspecific basal area and dead tree basal area. Synthesis and applications. The change from beech‐maple‐birch forests to more beech‐dominated forests with beech encroachment to new forest areas across the north‐eastern USA may continue if higher intensity harvesting and disturbances (i.e. large‐scale canopy openings) do not occur. This would be a significant management concern as beech is associated with a widespread bark disease, is commercially less desirable, and can limit natural regeneration from other species. Our results emphasize the need for management strategies such as higher intensity harvesting methods, vegetation control and limiting browsing pressure to reduce beech dominance.

Three centuries of fire and forest vegetation transitions preceding Texas’ most destructive wildfire: Lost Pines or lost oaks?

In 2011, the most destructive wildfire in Texas history (Bastrop County Complex Fire, BCCF) burned 34,000 acres including most of Bastrop State Park. We used dendrochronological analysis of vegetation paired with documentary information to reconstruct the historical fire regime, changes in forest composition, and possible human influences leading up to this seemingly unique event. In addition, demographics of fire-killed and immediate post-fire regenerating trees were determined through stem aging and a regeneration census. Historical fire frequency was lower during the pre-EuroAmerican Settlement period (pre-1830) compared to later time periods before the 1920s. Since the 1920s, fire occurrence has significantly decreased. Historical fire characteristics appeared to change with local and regional cultural and land use changes. Within the BCCF area were extensive areas of very old (up to 359yrs old) open-grown post oaks (Quercus stellata) that had been overtopped by 60year old loblolly pines (Pinus taeda). Historically, oak woodlands likely persisted in the study area due to recurring fire and, though less well documented, by grazing and selective logging for loblolly pines. This region is an ecotone between the oak woodlands and Lost Pines and our data show transitions between the two types through time. It is unclear how this vegetation interaction may have affected the destructive BCCF, but its severity and effects were unprecedented during at least the last three centuries. Little to no loblolly pine natural regeneration existed despite being dominant in the pre-fire forest overstory. Based on stump sprout abundance, blackjack oak (Q. marilandica) will likely be the dominant tree species in the next few decades.

Seven decades of change in forest structure and composition in Pinus resinosa forests in northern Minnesota, USA: Comparing managed and unmanaged conditions

An understanding of long-term patterns of forest structural and compositional development is critical for anticipating management outcomes and developing appropriate silvicultural strategies for restoring complex forest conditions. In most cases, this information comes from stand-level assessments; however, the impacts and outcomes of management and other disturbances on forest development occur over multiple spatial scales across a landscape. We compared historical (1941) and contemporary (2012–2014) forest structure and composition on 301 plots distributed across managed and unmanaged, late seral red pine (Pinus resinosa)-dominated forests in a 1230ha landscape in north-central Minnesota, USA. Discriminate factor analysis was used to determine which compositional and structural attributes best described the forest conditions between two sampling periods (1941, 2012–2014) and management histories (managed and unmanaged). Plot basal area, average diameter of live trees, richness of tree size classes, and the basal area of standing deadwood were the four most important variables in discriminating between the managed and unmanaged plots in 1941 and 2013. In some cases, structural conditions between managed and unmanaged plots converged, including contemporary BA, trees per hectare, size inequality, and structural complexity indices. In contrast, several attributes, including standing deadwood basal area and percent hardwood basal area, were significantly greater in unmanaged plots after 72years and highlight the lasting influence of land use on these structural and compositional conditions. The broad ranges of structural and compositional conditions observed across the landscape highlight the importance of having spatially varying desired future conditions across managed stands to approximate this range in live and dead-tree attributes in unmanaged forests. In addition, the lower basal area of standing dead trees documented in this and other comparisons of unmanaged and managed P. resinosa systems argues for an increased emphasis on deliberate deadwood and live-tree retention to recruit these features if the restoration of late-successional forest conditions is included as a management objective.

Forest vegetation change and disturbance interactions over the past 7500 years at Sasquatch Lake, Columbia Mountains, western Canada

Fire is the most important abiotic disturbance in the interior cedar-hemlock (ICH) and Engelmann spruce–subalpine fir (ESSF) forest zone of southeastern British Columbia, Canada. Other disturbances are also important, such as defoliator and boring insect outbreaks, windthrow, diseases, and rapid mass movements. Few studies have examined the interaction between multiple types of disturbances in these forests over long timescales. Here we present high-resolution analyses of biomass burning, erosion, and vegetation assemblage changes at Sasquatch Lake (NEL02), a valley lake in the Columbia Mountains. The 531.5 cm sediment core was radiocarbon dated and provided a 7500-year stratigraphy that was used for pollen, macroscopic charcoal (>150 μm), and sedimentologic analyses. Pollen and charcoal data provided evidence of forest composition changes and fire activity. Magnetic susceptibility, loss-on-ignition, and particle size distribution analyses characterised changes in erosion into the basin. The results show that coniferous forests, with a high abundance of Pinus pollen, had established in the catchment by the beginning of the record and were subject to intermittent burning and high-energy erosive events. Tsuga heterophylla expanded by 4400 cal BP and the modern interior cedar-hemlock forests expanded throughout the lower elevations due to increased regional continentality since 4500 cal BP. High-energy erosional inputs to the lake were less frequent from 3500 to 750 cal BP and rapid mass movements may have increased in frequency during the Little Ice Age. Dendrochronological evidence in these stands suggests a mixed-severity fire regime during past ∼300 years, which has not been fully examined for charcoal-based fire event reconstruction. Here we use identified peaks as an indicator of increased biomass burning and charcoal movement in the catchment in relation to peaks in allochthonous clastic material to understand the potential relationships between biomass burning and erosion events at multiple temporal scales in the catchment. This suggests that post-fire conditions, up to several decades, were subject to increased erosion to the lake and erosion events were more common during the early Holocene. Establishment of dense ESSF and ICH forests decreased siliciclastic input to the lake throughout the mid Holocene until a recent rockslide. The high-resolution sampling of this lake sediment record provides long-term evidence of variability in the relationships between vegetation cover, fire and erosion at a catchment scale.

Tree growth is more sensitive than species distributions to recent changes in climate and acidic deposition in the northeastern United States

Summary Tree‐growth responses to environmental change could provide early detection of shifts in forest composition and help facilitate ecosystem management and conservation. We studied forest tree responses to recent trends in climate and acidic deposition using analyses of tree rings and long‐term climate, deposition and forest plot data along an elevational climatic gradient in the northeastern United States. We analysed how (i) individual growth of dominant species (Picea rubens, Abies balsamea) and (ii) spatial distributions of all species, changed with elevation over time due to changing environment. We observed a mean 220 m upslope shift of temperature envelopes since the 1960s, consistent with regional climate warming, but found no evidence of synchronous upslope shifts in species abundance. Species' ranges were stable although some leaned upslope or downslope, suggesting species‐specific migration lags or controls on species' ranges. Compared to species distributions, the growth of dominant species was more responsive to environmental change. Although the basal area of P. rubens declined within its range since the 1960s, its growth has increased recently with increasing precipitation pH and to a lesser extent with warming climate. Abies balsamea has gradually increased in both basal area and density since the 1960s, with its growth responding to precipitation pH but not climate. Historically, P. rubens grew better at lower and A. balsamea at higher elevations, but these elevation effects appeared to be mediated primarily by moisture, and have disappeared over time. Synthesis and applications. Mean tree‐growth responses to changing climate (temperature, moisture) and precipitation chemistry were more consistent and more clearly detectable than shifts in tree species' ranges, suggesting that monitoring tree growth across climatically controlled species' ranges (e.g. along elevational or latitudinal gradients) may provide a powerful tool for early detection of potential future changes in forest composition in a changing environment.

Assessing and predicting shifts in mountain forest composition across 25 years of climate change

AbstractAimSpatial predictions of future communities under climate change can be obtained by stacking species distribution models (S‐SDM), but proper evaluation of community S‐SDM predictions across time with fully independent data has rarely been carried out. The aim of this study was to evaluate the predictive abilities of S‐SDMs for whole forest communities across the last 25 years in a mountain region.LocationThe western Swiss Alps.MethodsWe used past vegetation surveys (2,984 plots) and environmental data from the 1990s to calibrate SDMs for 364 plant species and predict changes in forest composition under contemporary conditions. These projections were then evaluated by resurveying a random subset of 92 forest plots in summer 2014.ResultsSpecies distribution models showed the same accuracy in the past (calibration data) and present (evaluation data). The S‐SDMs correctly predicted the general trends in species richness and shift of ecological conditions (i.e., temperature, moisture) at the regional level. However, it proved more difficult to identify precisely which forest communities or areas are most or least affected by climate change.Main conclusionOur results show that, across a period of a few decades, S‐SDMs can usefully predict trends in macroecological properties such as richness or average ecological conditions, but fail to accurately predict changes in composition. This is likely due to the combined effects of the stochasticity of local colonization and extinction events, dispersal limitations, community assembly rules (e.g., competition), observer bias, model and location errors and interannual variation. Furthermore, these models cannot account for potential species adaptations leading to persistence in sites predicted unsuitable. This highlights the need for developing more accurate forest community predictions as support to help prioritizing conservation actions.

Fire and dwarf mistletoe (Viscaceae: Arceuthobium species) in western North America: contrasting Arceuthobium tsugense and Arceuthobium americanum

Dwarf mistletoes (Viscaceae: Arceuthobium spp.) and fire interact in important ways in the coniferous forests of western North America. Fire directly affects dwarf mistletoes by killing the host, host branch, or heating/smoking the aerial shoots and fruits. Fire is a primary determinant of dwarf mistletoe distribution on the landscape, and time since fire controls many aspects of dwarf mistletoe epidemiology. Conversely, dwarf mistletoes can influence fire by causing changes in forest composition, structure, and fuels. Prescribed fire is important for management of dwarf mistletoes, while fire suppression is thought to have increased dwarf mistletoe abundance in western forests. Two dwarf mistletoes are compared in order to illustrate fire interactions in Oregon and Washington, USA: Arceuthobium americanum Nutt. ex Engelm. (lodgepole pine dwarf mistletoe) and Arceuthobium tsugense (Rosendahl)(western hemlock dwarf mistletoe). Arceuthobium persists on the landscape where the host is not killed by fire. Arceuthobium americanum spreads directly into the regenerating Pinus contorta Dougl. ex Loud., while A. tsugense persists in refugia for 200 years or more following fire. Host successional status is a driver of fire – dwarf mistletoe interactions, but forest disturbance agents also play a role. Given the importance of these interactions to the ecology of fire-prone forests, dwarf mistletoes warrant inclusion in disturbance ecology research.

Emergent climate and CO2 sensitivities of net primary productivity in ecosystem models do not agree with empirical data in temperate forests of eastern North America.

Ecosystem models show divergent responses of the terrestrial carbon cycle to global change over the next century. Individual model evaluation and multimodel comparisons with data have largely focused on individual processes at subannual to decadal scales. Thus far, data-based evaluations of emergent ecosystem responses to climate and CO2 at multidecadal and centennial timescales have been rare. We compared the sensitivity of net primary productivity (NPP) to temperature, precipitation, and CO2 in ten ecosystem models with the sensitivities found in tree-ring reconstructions of NPP and raw ring-width series at six temperate forest sites. These model-data comparisons were evaluated at three temporal extents to determine whether the rapid, directional changes in temperature and CO2 in the recent past skew our observed responses to multiple drivers of change. All models tested here were more sensitive to low growing season precipitation than tree-ring NPP and ring widths in the past 30years, although some model precipitation responses were more consistent with tree rings when evaluated over a full century. Similarly, all models had negative or no response to warm-growing season temperatures, while tree-ring data showed consistently positive effects of temperature. Although precipitation responses were least consistent among models, differences among models to CO2 drive divergence and ensemble uncertainty in relative change in NPP over the past century. Changes in forest composition within models had no effect on climate or CO2 sensitivity. Fire in model simulations reduced model sensitivity to climate and CO2 , but only over the course of multiple centuries. Formal evaluation of emergent model behavior at multidecadal and multicentennial timescales is essential to reconciling model projections with observed ecosystem responses to past climate change. Future evaluation should focus on improved representation of disturbance and biomass change as well as the feedbacks with moisture balance and CO2 in individual models.

Water yield following forest–grass–forest transitions

Abstract. Many currently forested areas in the southern Appalachians were harvested in the early 1900s and cleared for agriculture or pasture, but have since been abandoned and reverted to forest (old-field succession). Land-use and land-cover changes such as these may have altered the timing and quantity of water yield (Q). We examined 80 years of streamflow and vegetation data in an experimental watershed that underwent forest–grass–forest conversion (i.e., old-field succession treatment). We hypothesized that changes in forest species composition and water use would largely explain long-term changes in Q. Aboveground biomass was comparable among watersheds before the treatment (208.3 Mg ha−1), and again after 45 years of forest regeneration (217.9 Mg ha−1). However, management practices in the treatment watershed altered resulting species composition compared to the reference watershed. Evapotranspiration (ET) and Q in the treatment watershed recovered to pretreatment levels after 9 years of abandonment, then Q became less (averaging 5.4 % less) and ET more (averaging 4.5 % more) than expected after the 10th year up to the present day. We demonstrate that the decline in Q and corresponding increase in ET could be explained by the shift in major forest species from predominantly Quercus and Carya before treatment to predominantly Liriodendron and Acer through old-field succession. The annual change in Q can be attributed to changes in seasonal Q. The greatest management effect on monthly Q occurred during the wettest (i.e., above median Q) growing-season months, when Q was significantly lower than expected. In the dormant season, monthly Q was higher than expected during the wettest months.

Climate changes and wildfire alter vegetation of Yellowstone National Park, but forest cover persists

AbstractWe present landscape simulation results contrasting effects of changing climates on forest vegetation and fire regimes in Yellowstone National Park, USA, by mid‐21st century. We simulated potential changes to fire dynamics and forest characteristics under three future climate projections representing a range of potential future conditions using the FireBGCv2 model. Under the future climate scenarios with moderate warming (>2°C) and moderate increases in precipitation (3–5%), model simulations resulted in 1.2–4.2 times more burned area, decreases in forest cover (10–44%), and reductions in basal area (14–60%). In these same scenarios, lodgepole pine (Pinus contorta) decreased in basal area (18–41%), while Douglas‐fir (Pseudotsuga menziesii) basal area increased (21–58%). Conversely, mild warming (<2°C) coupled with greater increases in precipitation (12–13%) suggested an increase in forest cover and basal area by mid‐century, with spruce and subalpine fir increasing in abundance. Overall, we found changes in forest tree species compositions were caused by the climate‐mediated changes in fire regime (56–315% increase in annual area burned). Simulated changes in forest composition and fire regime under warming climates portray a landscape that shifts from lodgepole pine to Douglas‐fir caused by the interaction between the magnitude and seasonality of future climate changes, by climate‐induced changes in the frequency and intensity of wildfires, and by tree species response.

Revision and application of the LINKAGES model to simulate forest growth in central hardwood landscapes in response to climate change

Context Global climate change impacts forest growth and methods of modeling those impacts at the landscape scale are needed to forecast future forest species composition change and abundance. Changes in forest landscapes will affect ecosystem processes and services such as succession and disturbance, wildlife habitat, and production of forest products at regional, landscape and global scales.

Climate and seed availability initiate alternate post‐fire trajectories in a lower subalpine forest

AbstractQuestionsDo functional traits explain individual tree species’ responses to environmental filters and dispersal limitations following stand‐replacing fire? Can post‐fire conditions initiate alternate trajectories of community assembly?LocationGlacier National Park, Montana,USA.MethodsWe characterized the species composition of tree re‐establishment following nine recent fires in the lower subalpine zone of Glacier National Park, a region with multiple co‐dominant tree species that has experienced extensive fire in recent decades. We usedGLMMsto describe individual species’ responses to spatial and temporal heterogeneity of post‐fire conditions and seed availability, and used multivariate approaches to examine whether post‐fire conditions can initiate alternate trajectories of forest community assembly.ResultsPost‐fire regeneration responses were strongly species‐dependent and consistent with functional trait differences. We found that there was a brief opportunity for establishment during the first several years after fire, during which tree recruitment for all species was contingent upon the availability of nearby seeds and the occurrence of favourable weather conditions. There was a remarkable amount of compositional change following fire, and the majority of our study sites transitioned from a mixed forest to a tree assemblage dominated by a single species.ConclusionsDifferential species‐specific responses to climate and disturbance can initiate alternate trajectories of community assembly, triggering substantial changes in forest composition. The composition of post‐fire tree assemblages reflects the differential responses of individual species to climate and disturbance, providing support for the interacting role of dispersal and environmental filtering in shaping post‐disturbance communities and highlighting the importance of incorporating functional traits into predictive models of ecosystem dynamics.

Anthropogenic Disturbances Create a New Vegetation Toposequence in the Gatineau River Valley, Quebec

This study measured changes in forest composition that have occurred since the preindustrial era along the toposequence of the Gatineau River Valley, Quebec, Canada (5650 km2), based on survey records prior to colonization (1804–1864) and recent forest inventories (1982–2006). Changes in forest cover composition over time were found to be specific to toposequence position. Maple and red oak are now more frequent on upper toposequence positions (+26%, +21%, respectively), whereas yellow birch, eastern hemlock, and American beech declined markedly (−34% to −17%). Poplar is more frequent throughout the landscape, but particularly on mid-toposequence positions (+40%). In contrast, white pine, frequent on all toposequence positions in the preindustrial forest, is now confined to shallow and coarse-textured soils (−20%). The preindustrial forest types of the study area were mostly dominated by maple, yellow birch, and beech, with strong components of white pine, hemlock, and eastern white cedar, either as dominant or codominant species. In a context of ongoing anthropogenic disturbances and environmental changes, it is probably not possible to restore many of these types, except where targeted silvicultural interventions could increase the presence of certain species. The new forest types observed should be managed to ensure continuity of vital ecosystem services and functions as disturbance regimes evolve.

High-frequency variation of tree-ring width of some native and alien tree species in Latvia during the period 1965–2009

The plasticity of climate-growth relationships of trees is one of the main factors determining the climate-induced changes in forest productivity and composition. In this study, high-frequency variation of tree-ring width (TRW) of four native and three alien tree species and two hybrids of Populus L. growing in Latvia (hemiboreal zone) was compared using a principal component analysis based on TRW indices for the period 1965–2009. The effect of climatic factors was assessed using a bootstrapped correlation analysis. Influence of common climatic factors related to the length of the vegetation season, winter temperature, and water regime in summer was traced in the TRW of the studied species and hybrids. The combination and effect of the identified factors differed by species (and hybrids), to a certain extent explaining the diversity of TRW patterns. Nevertheless, some similarities among the species were also observed, suggesting the plasticity of growth response. Scots pine was generally sensitive to winter temperatures, but Norway spruce was mainly sensitive to summer water regime, while black alder was sensitive to winter temperatures and precipitation in spring. In contrast, silver birch showed the lowest sensitivity to the tested climatic factors (demonstrating sensitivity to winter precipitation in a few sites), suggesting tolerance to weather fluctuations. The TRW of the alien species was primarily sensitive to climatic factors related to water regime in the summer of the year preceding the formation of tree-ring, implying differences in mechanisms regulating wood increment. Nevertheless, temperature in the dormant period was significant for European larch in a few sites, suggesting sensitivity to cold damage. The variation of TRW of Populus hybrids diverged from others, as their growth was negatively correlated with the temperature in autumn, spring, and summer and positively correlated with water balance. Although the annual water balance in Latvia is positive, the effect of water deficit on tree growth was apparent.

The fourth dimension of vegetation.

100 years ago, Lennart von Post first used pollen analysis to reconstruct past ecosystems

Analysis of the changes in forest ecosystem functions, structure and composition in the Black Sea region of Turkey

We used geographical information system to analyze changes in forest ecosystem functions, structure and composition in a typical department of forest management area consisting of four forest management planning units in Turkey. To assess these effects over a 25 year period we compiled data from three forest management plans that were made in 1986, 2001 and 2011. Temporal changes in forest ecosystem functions were estimated based on the three pillars of forest sustainability: economics, ecology and socio-culture. We assessed a few indicators such as land-use and forest cover, forest types, tree species, development stage, stand age classes, crown closure, growing stock and its increment, and timber biomass. The results of the case study suggested a shift in forest values away from economic values toward ecological and socio-cultural values over last two planning periods. Forest ecosystem structure improved, due mainly to increasing forest area, decreasing non-forest areas (especially in settlement and agricultural areas), forestation on forest openings, rehabilitation of degraded forests, conversion of even-aged forests to uneven-aged forests and conversion of coppice forests to high forests with greater growing stock increments. There were also favorable changes in forest management planning approaches.