Factors influencing late-Holocene vegetation dynamics and biodiversity on Hallands Väderö, SW Sweden: A statistical evaluation

Forest composition characteristic of the Mid-Holocene has survived on Hallands Väderö, an island nature reserve off the south west coast of Sweden. Current veteran Tilia and Quercus trees contribute to a remarkably rich biodiversity of fungi, bryophytes, lichens and insects. Understanding which potential factors influence Holocene vegetation dynamics can support efforts to protect biodiversity, but the role of grazing and browsing has previously been difficult to evaluate because of the lack of long-term datasets. Palaeoecological analyses over the last c. 3000 years from a pond on the island reveal sustained presence of Quercus, Alnus, Tilia, Corylus and Ulmus, alongside increasing Fagus in recent centuries. Changes in grazing pressure have been documented since AD 1665 and a statistical approach was used to calculate the relative importance of grazing pressure, climate variability, and fire activity on the dynamics of selected taxa. Grazing was the main factor reducing population size of Fagus, Alnus, Tilia and Corylus on the island over the period AD 1665–1858, with warm winter temperatures and summer humidity having significant positive influences in the last millennium for Quercus, Alnus, Tilia and Corylus. The survival of large numbers of red-listed species is likely to be due to the continuity of large old trees, ancient forest composition and a distinctive disturbance history in a favourable climate. </jats:p

The history of <i>Fagus sylvatica</i> at its northern limit in Vendsyssel, Denmark

Pollen, plant macrofossils and charcoal analyses were used to study tree diversity, fire history and forest disturbance over the past c. 3500 years at three forest remnant sites in Vendsyssel, northern Denmark. All locations had a more diverse tree composition in the past including abundant Alnus, Betula, Corylus, Pinus, Quercus, Salix, Tilia and Ulmus. The changes in tree diversity through time can be attributed to a combination of factors including climate change, burning linked to shifting cultivation, grazing and felling. The balance between arboreal and non-arboreal pollen was already being influenced by human activities in the late Bronze Age c. 3000 years ago. The high pollen abundance values recorded for Tilia pre-2000 years ago are exceptional as compared to later periods at these sites. At one location, the transition from Tilia to Fagus indicated that Tilia prevailed until c. 1300 years ago. Subsequent periods of forest clearance, with charcoal and cereal cultivation, initially including Hordeum and subsequently also Secale, were recorded. There was pollen evidence for grazing followed by shrub regeneration including Calluna, Erica, Juniperus and herbaceous taxa, and following that, a forest recovery of mainly Fagus, Picea and Pinus. This recovery is also recorded in historical forest records from 1880 CE onwards, emphasising the dominant role of plantation schemes. Results are placed in a wider framework of other sites in Denmark and southern Scandinavia, which have also documented a reduction of tree diversity and forest cover over the same period. The evidence from the long-term record is used to draw conclusions to assist forest restoration programmes. </jats:p

Patterns and dynamics of European vegetation change over the last 15000 years

Aim Palaeoecological reconstructions document past vegetation change, with estimates of fast shifts in species distributions. The resulting rates of plant spread are often not matched by model simulations of climate-driven vegetation dynamics. Genetic surveys of extant plant populations document directions of the post-glacial spread of trees, challenging traditional interpretations. Our aim is to examine an updated continental pollen data set from Europe in the light of the new ideas about vegetation dynamics emerging from genetic research and vegetation modelling studies. Location Europe. Methods We use pollen data from the European Pollen Database (EPD) to construct interpolated maps of pollen percentages documenting changes in the distribution and abundance of major plant genera and the grass family in Europe over the last 15,000years. Results Our analyses confirm high rates of post-glacial spread with at least 1000myear(-1) for Corylus, Ulmus and Alnus and average rates of 400myear(-1) for Tilia, Quercus, Fagus and Carpinus. The late Holocene expansions of Picea and Fagus populations in many European regions cannot be explained by migrational lag. Both taxa shift their population centres towards the Atlantic coast suggesting that climate may have played a role in the timing of their expansions. The slowest rates of spread were reconstructed for Abies. Main conclusions The calculated rates of post-glacial plant spread are higher in Europe than those from North America, which may be due to more rapid shifts in climate mediated by the Gulf Stream and westerly winds. Late Holocene anthropogenic land use practices in Europe had major effects on individual taxa, which in combination with climate change contributed to shifts in areas of abundance and dominance. The high rates of spread calculated from the European pollen data are consistent with rapid tracking of early Holocene climate change by common tree species, documenting that plants can spread fast tracing their climate space, regardless of their dispersal strategy

Fire-vegetation interactions during the last 11,000 years in boreal and cold temperate forests of Fennoscandia

The long-term ecological interactions between fire and the composition of dominant trees and shrubs in boreal and cold temperate Fennoscandian forests are still under discussion. We hypothesized that fire-prone taxa should abound during periods and regions characterized by higher fire disturbance, while fire-intolerant taxa should dominate when and where fire activity is low. Biomass burning (BB) is here investigated based on 69 sedimentary charcoal records. For the same sites, the relative contribution of pollen-based reconstructions of dominant vegetation cover divided into three different fire-sensitivity classes is explored by means of a statistical approach. The overall patterns found across Fennoscandia suggest that Ericaceae (mainly Calluna), Pinus, Betula and Populus are strongly positively correlated with multi-millennial variability of BB in both boreal and cold temperate forests, confirming their fire-prone character (taxa adapted/favoured by burning). Positive but much weaker (and not always significant) relationships also exist between long-term trends in BB and Fagus, Quercus, Corylus, Alnus, Juniperus, Carpinus and Salix, fire-tolerant taxa that survive low/moderate intense fires because of specific functional traits or their rapid, enhanced regeneration after fire. A strong negative significant correlation is instead detected between BB and Picea, Ulmus Tilia, Fraxinus, which are fire-intolerant taxa and can locally disappear for a short time after a fire. This large-scale analysis supports our initial hypothesis that tree and shrub dominance was closely linked to biomass burning since the onset of the Holocene in the study regions. Fire was an important ecosystem disturbance in Fennoscandia influencing long-term vegetation dynamics and composition over the last 11,000 years, although human activities probably altered the strength of fire-vegetation interactions during more recent millennia

Fossil charcoal quantification using manual and image analysis approaches

Charcoal particles are evidence of past fire events and macro-charcoal particles have been shown to represent local fire events. There are several methods for the preparation and quantification of macro-charcoal particles, none of which have been universally accepted as standard. Very few studies compare methodological differences and no studies to date compare quantification by mass with quantification by volume using image analysis. Using three cores taken from a peatland located in SE Norway, we compare these two established methods using a generalized linear mixed model (GLMM) and a split-plot ANOVA test. We show that charcoal volume (image analysis method) was a better predictor of charcoal mass than charcoal particle number and the same size classes of charcoal as size class distributions were not spatially and temporally correlated. Although there is still a need for a common and unifying method, our results show that quantification of charcoal particles by image analysis including size (e.g. height in mm) and area (mm2)/volume (mm3) measurements provides more significant results in cross-site or multiple-site studies than quantifications based on particle number. This has implications for the interpretation of charcoal data from regional studies that are used to model drivers of wildfire activity and environmental change in boreal–temperate landscapes during the Holocene. </jats:p

School Effects on the Wellbeing of Children and Adolescents

Well-being is a multidimensional construct, with psychological, physical and social components. As theoretical basis to help understand this concept and how it relates to school, we propose the Self-Determination Theory, which contends that self-determined motivation and personality integration, growth and well-being are dependent on a healthy balance of three innate psychological needs of autonomy, relatedness and competence. Thus, current indicators involve school effects on children’s well-being, in many diverse modalities which have been explored. Some are described in this chapter, mainly: the importance of peer relationships; the benefits of friendship; the effects of schools in conjunction with some forms of family influence; the school climate in terms of safety and physical ecology; the relevance of the teacher input; the school goal structure and the implementation of cooperative learning. All these parameters have an influence in promoting optimal functioning among children and increasing their well-being by meeting the above mentioned needs. The empirical support for the importance of schools indicates significant small effects, which often translate into important real-life effects as it is admitted at present. The conclusion is that schools do make a difference in children’s peer relationships and well-being

Rapid carbon accumulation within an unmanaged, mixed, temperate woodland

Forest carbon stocks have increased in both Europe and North America in recent decades. National forest inventories are often used to indicate recent carbon dynamics, but the data from unmanaged forests are often incomplete. Here we calculate changing biomass carbon stocks for a mixed, unmanaged British woodland with two different management histories: (1) older growth stands untouched since 1902 and (2) younger growth stands clear felled in 1943 but have developed naturally since. Transects in the older growth have been monitored since 1945 and the younger growth since 1977. Separate estimates of tree carbon (C), soil C and dead wood C were obtained to verify how C is apportioned in these stands. Tree biomass C stocks had approximately doubled in the older growth stands since 1945 and 60% of C was stored in tree biomass, 38% was stored in soil and 2% stored in coarse woody debris. This study suggests that natural older growth stands are storing more C than typical managed forests, with tree biomass the most important compartment for C stores. If management is to be shifted from biomass production to increased C stores, due consideration should be given to the role of unmanaged, older growth forests.</p

sj-docx-1-hol-10.1177_09596836241236340 – Supplemental material for The history of Fagus sylvatica at its northern limit in Vendsyssel, Denmark

Supplemental material, sj-docx-1-hol-10.1177_09596836241236340 for The history of Fagus sylvatica at its northern limit in Vendsyssel, Denmark by Gina E Hannon, Richard HW Bradshaw, Richard C Chiverrell and Jens Peter Skovsgaard in The Holocene</p

Vegetation dynamics and Fire History in Färnebofjärden National Park, Central Sweden

Palaeoecological studies can identify past trends in vegetation communities and processes over long time scales. Pollen, plant macrofossils and charcoal analyses are used to reconstruct vegetation over the last 6400 years and provide information about former human impact and disturbance regimes in Färnebofjärden National Park, Central Sweden. Three specific conservation planning topics were addressed: (1) the changing ratio of conifers to broadleaved trees; (2) the origin and history of the river meadows and the biodiverse Populus tremula meadows; (3) the role of fire in the maintenance of biological values. Early diverse mixed broadleaved forest assemblages with pine were followed by significant declines of the more thermophilic forest elements prior to the expansion of spruce in the Iron Age. The rise to dominance of spruce was a ‘natural’ process that has been exaggerated by anthropogenic disturbance to artificially high levels today. The initial river meadow communities were facilitated by fire and frequent flooding events, but subsequent dynamics have more definitely been supported by human activities. Rural abandonment during the last 100 years has led to woody successions. Fire has been a continual disturbance factor with an influence on conservation issues such as Picea abies dominance and the maintenance of diverse, non-forest communities. Present occurrence of fire is unusually low, but natural fire frequencies are increasing in the region

Role of forest fires in Holocene stand-scale dynamics in the unmanaged taiga forest of northwestern Russia

Fossil pollen, conifer stomata, and charcoal records for the last 10,000 years were studied from three small hollow sites (Larix Hollow, Mosquito Hollow, and Olga Hollow) located at the modern western range limit of Siberian larch (Larix sibirica) in northwestern Russia to investigate the role of forest fires in stand-scale dynamics of taiga vegetation. Wavelet coherence analysis was utilized to reveal the significance of fire on the vegetation composition at different timescales by assessing the phase and strength of the relationship between forest fires and most common boreal tree taxa in a time–frequency window. Pollen and stomata data show that all of the modern-day common tree taxa, including Norway spruce (Picea abies) and Siberian larch, have been present in the study region since the early Holocene. The absence of charcoal layers at Mosquito Hollow suggests that this site has acted as a fire-free refugium with continuous dominance of spruce throughout the Holocene. Meanwhile, the Larix Hollow record indicates frequent local fire events and as a consequence, a more variable tree species composition. The wavelet coherence results show that the impact of forest fires on vegetation varies from short-term (<200-year periods) changes in individual tree taxa to long-term (400–800 years) changes in forest composition, such as the expansion of spruce population after local high-intensity fires around 7500–7000 cal. yr BP and the increase in abundance of birch and alder during periods of high fire frequency. Our results suggest that Holocene fire histories can be markedly different within a small geographical area, demonstrating the importance of site-specific factors in the local fire regime in the unmanaged taiga forest