Trying to keep nature the same is a fool’s errand – we should embrace change

First paragraph: When it comes to deciding which plants and animals to protect and which to remove, our approach might make even the most forthright nationalist blush if it were ever applied to people. The central question in the UK and many other countries is whether a particular species is native or non-native

Els faigs es defensen del canvi climàtic

Investigadors del Centre de Recerca Ecològica i Aplicacions Forestals (CREAF), del CSIC i de la Universitat Autònoma de Barcelona han descobert que les poblacions de faigs mostren capacitat d'adaptar-se a l'escalfament climàtic que estem vivint. En particular, han observat que cada cop hi ha més fagedes adaptades a temperatures més càlides. No està clar, però, que aquesta capacitat d'adaptació permeti pal·liar completament els efectes del canvi climàtic.Investigadores del Centro de Investigación Ecológica y Aplicaciones Forestales (CREAF), del CSIC y de la UAB han descubierto que las poblaciones de hayas muestran capacidad de adaptarse al calentamiento global que estamos viviendo. En particular, han observado que cada vez hay más hayedos adaptados a temperaturas más cálidas. No obstante, no está claro que esta capacidad de adaptación permita paliar completamente los efectos del cambio climático

Consequences of treeline shifts for the diversity and function of high altitude ecosystems

Treeline expansion is reported as a widespread response to rising temperatures, yet few studies have considered the impact of treeline advance on the diversity and function of high altitude systems. Evidence suggests that climate change is already having a negative impact on alpine diversity and is modifying functions such as carbon sequestration and nutrient cycling. Treeline advance is likely to further affect diversity and function, yet our understanding of the processes involved is limited. Here we review and synthesize literature that assesses the impact of treeline advance into treeless ecosystems. Using published literature, we explore to what extent treeline advance will lead to the displacement of alpine species and the fragmentation of alpine habitats. While large changes will be observed in the ecosystems above the current treeline as trees migrate, it is likely that these newly forested areas will deviate substantially from the established forests from which they have developed. Consequently, at the forest community level we investigate the potential for differential response speeds of typical forest plant species, and the potential for treeline advance to lead to community disassembly. Given that changes in species presence and abundance can alter the functional composition of plant communities, we explore the potential for shifts in tree distribution to lead to changes in carbon storage, nutrient cycling, and hydrological properties of ecosystems. Despite typically being intensively studied regions, the likely impact of forest expansion above the current mountain treeline has received relatively little attention and so we identify key knowledge gaps that should act as priorities for future research in mountain systems

Coppice management of forests impacts spatial genetic structure but not genetic diversity in European beech (Fagus sylvatica L.)

Coppice management of forests was historically common in Europe. Actively managed coppice persists through vegetative regeneration prolonging the lifespan of trees and reducing flowering, seed production, and establishment. As coppicing alters the primary regeneration pathway within a stand, it is expected to alter the level and structuring of genetic diversity within populations. The study species, European beech (Fagus sylvatica L.), has historically experienced widespread coppicing throughout the range of the species. Genetic material was obtained from paired coppiced and high forest stands, in each of three study sites across Europe located in Germany, France, and Italy. Trees were genotyped at 11 microsatellite loci. Estimates of genetic diversity were found to be equally high as those found in natural forests. Significant spatial genetic structure of coppice stands extended 10-20m further than their paired high forest indicating that local-scale patterns of geneflow have been significantly altered by generations of forest management in the coppice stands. Understanding the implications of such changes for the structure and level of diversity within traditionally managed populations can assist with management planning for conservation and resource use into the future

Geographic patterns in the distribution, productivity and population genetic structure of Cirsium species across their UK geographic range.

Geographically peripheral populations are believed to be particularly important in a species' response to environmental change and for the conservation of intraspecific genetic diversity. It is expected that as a species' range limits are approached, productivity and reproduction will decline and populations will become less abundant and more isolated. Decreased genetic variability and increased genetic divergence of peripheral populations is predicted based on these patterns. Cirsium heterophyllum reaches a southern geographical limit in the UK, C. acaule and C. eriophorum reach a northern limit and C. arvense occurs throughout the UK. These species have been used to determine whether contemporary patterns of distribution, productivity and reproductive potential across a species' UK latitudinal range are reflected in the predicted patterns of population genetic structure (assessed using microsatellite markers). Population frequency declines approaching the periphery of Cirsium acaule and C. heterophyllum. A decline in abundance was found in C. heterophyllum only. Community surveys suggest that peripheral populations do not occur in atypical habitat. There is no latitudinal variation in morphological characters across the species range, whereas reproductive potential declines approaching the periphery of the species that reach a latitudinal limit in the UK. Population genetic analysis revealed a decline in genetic variation toward the latitudinal limit of C. acaule. This pattern is absent in C. heterophyllum despite a marked decline in seed production and increase in population - . isolation approaching its periphery. C. heterophyllum exhibits almost randomised geographical structure of genetic variation. The lack of agreement between patterns of reproductive potential and population frequency and population genetic structure suggests that contemporary patterns of population distribution and reproduction may be inadequate for indicating patterns of population genetic structure within a species. Interspecific differences in post-glacial history may be important in explaining this disparity

Larger investment in roots in southern range-edge populations of Scots pine is associated with increased growth and seedling resistance to extreme drought in response to simulated climate change

Extreme climate events such as heat waves or severe drought have the potential to fundamentally alter species dynamics, and are expected to increase in frequency in the coming decades. Early life stages of plant species are highly sensitive to these variations, with the potential for profound consequences for plant communities. In order to explore the response of Scots pine (Pinus sylvestris L.) seedlings to predicted increases in temperature and extreme drought, we performed a controlled-conditions experiment using growth chambers to simulate (1) current and future temperatures expected at the southernmost edge of the range, (2) current and drier growing seasons before an acute summer drought, and (3) drought alleviation by sporadic rainy events during summer. We analysed the response of seedlings by assessing survival, growth, biomass allocation and isotopic discrimination. Southern range-edge seedlings were compared under same conditions with those from the northern range edge, which experience cooler and wetter conditions throughout the year. The combination of extreme drought and the predicted temperature rise severely reduced overall survival for both provenances. A reduction in precipitation before the onset of drought diminished the survival and final biomass of seedlings, while the interruption of summer drought drastically increased survival probabilities. Southern seedlings invested a higher proportion of their biomass in roots, which conferred on them higher growth, higher survival probabilities, better nutritional status and lower drought stress. These results help us to understand the mechanisms of local adaptation at the southern range edge and indicate southern populations as a valuable genetic resource to buffer the response of Scots pine against such extreme climatic events

Forest disturbance leads to the rapid spread of the invasive leucaena leucocephala in Taiwan

This study, based on different investigative documents and analytical methods, elucidates spatial distribution of habitats for major invasive exotic plants, Leucaena leucocephala, in Taiwan. Results show that Leucaena leucocephala is most harmful to broad-leaved trees and its invasion directly relates to changes in the physical environment. Leucaena leucocephala can bloom and bear fruits all year round and during the period of seeds sprouting and saplings, the invasion varies greatly among different soil types. Leucaena leucocephala prefers weakly acidic soil, though it grows well with other soil textures and nutrients as well. The average spreading rate of Leucaena leucocephala is 3.55 ha year-1 on abandoned farm land calculated from the aerial photographs taken in 1982, 1992, 2003, and 2007

Refining predictions of population decline at species' rear edges

According to broad‐scale application of biogeographical theory, widespread retractions of species’ rear edges should be seen in response to ongoing climate change. This prediction rests on the assumption that rear edge populations are ‘marginal’ since they occur at the limit of the species’ ecological tolerance and are expected to decline in performance as climate warming pushes them to extirpation. However, conflicts between observations and predictions are increasingly accumulating and little progress has been made in explaining this disparity. We argue that a revision of the concept of marginality is necessary, together with explicit testing of population decline, which is increasingly possible as data availability improves. Such action should be based on taking the population perspective across a species’ rear edge, encompassing the ecological, geographical and genetic dimensions of marginality. Refining our understanding of rear edge populations is essential to advance our ability to monitor, predict and plan for the impacts of environmental change on species range dynamics

Warming induced growth decline of Himalayan birch at its lower range edge in a semi-arid region of Trans-Himalaya, central Nepal

Changes in the position of altitudinal treelines and timberlines are considered useful indicators of climatic changes on tree growth and forest dynamics. We sought to determine if recent warming is driving contrasting growth responses of Himalayan birch, at moist treeline (Lete Lekh) and semi-arid timberline (Chimang Lekh) sites in the Trans-Himalayan zone of central Nepal. We used dendrochronological techniques to measure tree ring width (TRW) and basal area increment (BAI) of birch trees from climatically contrasting but nearby sites. The TRW series were correlated with climate records from nearby meteorological stations, and BAI was compared between populations to explore growth trends over recent decades. We found contrasting precipitation trends between nearby sites such that the wet site (Lete) is getting warmer and wetter, and the dry site (Chimang) is getting warmer and drier in recent decades. The radial growth of birch in both moist and semi arid sites are positively correlated to spring (March-May) rainfall, and negatively correlated to mean and maximum temperature for the same period. The growth climate analysis indicated that moisture availability in early growing season is crucial for birch growth at these locations. The BAI of birch is declining more rapidly at the dry timberline than at the moist treelines in the recent decades, indicating that climatic warming might negatively impact birch radial growth where warming interacts with increasing spring drought in the region. Our work highlights contrasting growth response of birch to climate change at moist and semi-arid forests indicating that local climatic variation must be accounted for when assessing and forecasting regional patterns of tree growth in topographically complex regions like Trans-Himalaya, in order to make accurate predictions of vegetation responses to climate change

Temperature and sheltering determine patterns of seedling establishment in an advancing subtropical treeline

Questions: An advance of high-altitude treelines has been reported in response to warming climate throughout the globe. Understanding local controls on the establishment of seedlings above the treeline is essential for predicting wider patterns of treeline response from a process-based perspective. Here we investigate patterns of seedling establishment in relation to microsite conditions in an advancing treeline ecotone in the subtropics, using climate data recorded at the plant-relevant scale. We sought to determine which temperature factors were of importance, if sheltering plays an important role in seedling establishment and if the response varied with seedling age. Location: The Abies kawakamii treelines of the Central Mountain Range, Taiwan, 2800 to 3275m a.s.l. Methods: Seedlings were monitored in plots covering a range of treeline structural forms over a period of 2yrs. Temperatures were recorded at plant-relevant height (5cm) above ground and depth below ground with data loggers. Microtopographic sheltering (at a 10-m scale) and surrounding vegetation were measured. The influence of the above variables on seedling number and growth was investigated using generalized linear models and linear mixed effect models, respectively. Results: Soil temperatures had more influence on seedling number than air temperature, whilst air temperature was positively associated with subsequent seedling growth. Establishment patterns were found to have a strong relationship with microtopographic sheltering, with more sheltered areas having elevated seedling numbers. Early growth may have significant implications for subsequent plant performance since smaller seedlings were more sensitive to both temperature and microtopography than larger seedlings. Conclusions: Air and soil temperatures and microtopography determine spatial patterns of seedling establishment. Our results suggest that establishment above the treeline is likely to continue as the climate warms, although advance will not be spatially uniform due to the modifying influence of topography. This variability has important implications for the persistence and extinction of alpine plant communities occurring above treeline in topographically complex systems