Highest drought sensitivity and lowest resistance to growth suppression are found in the range core of the tree Fagus sylvatica L. not the equatorial range edge

Cavin L., Jump A.S. (2016) Highest drought sensitivity and lowest resistance to growth suppression are found in the range core of the tree Fagus sylvatica L. not the equatorial range edge. Global Change Biology. : 0-0.
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Doi: 10.1111/gcb.13366

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Biogeographical and ecological theory suggests that species distributions should be driven to higher altitudes and latitudes as global temperatures rise. Such changes occur as growth improves at the poleward edge of a species distribution and declines at the range edge in the opposite or equatorial direction, mirrored by changes in the establishment of new individuals. A substantial body of evidence demonstrates that such processes are underway for a wide variety of species. Case studies from populations at the equatorial range edge of a variety of woody species have led us to understand that widespread growth decline and distributional shifts are underway. However, in apparent contrast, other studies report high productivity and reproduction in some range edge populations. We sought to assess temporal trends in the growth of the widespread European beech tree (Fagus sylvatica) across its latitudinal range. We explored the stability of populations to major drought events and the implications for predicted widespread growth decline at its equatorial range edge. In contrast to expectations, we found greatest sensitivity and low resistance to drought in the core of the species range, whilst dry range edge populations showed particularly high resistance to drought and little evidence of drought-linked growth decline. We hypothesize that this high range edge resistance to drought is driven primarily by local environmental factors that allow relict populations to persist despite regionally unfavourable climate. The persistence of such populations demonstrates that range-edge decline is not ubiquitous and is likely to be driven by declining population density at the landscape scale rather than sudden and widespread range retraction. Copyright © 2016 John Wiley & Sons Ltd

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Community change and species richness reductions in rapidly advancing tree lines

Greenwood S., Chen J.-C., Chen C.-T., Jump A.S. (2016) Community change and species richness reductions in rapidly advancing tree lines. Journal of Biogeography. : 0-0.
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Doi: 10.1111/jbi.12776

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Aim: Climate change is causing shifts in the range of species worldwide. In high-altitude areas forests are often observed to be shifting their upper limits to higher altitudes in response to warming temperatures. Although this phenomenon is well described, the possible consequences of this for the wider forest community have not been fully considered. In this study, we used epiphytic macro-lichens to investigate the impacts of tree line advance on associated organisms. We hypothesized that the rate of forest advance should influence the species richness and composition of associated communities. Location: The Hehuanshan area, Central Mountain Range, Taiwan (24°08-09' N, 121°15 - 16' E). Methods: Lichen communities were sampled on trees occurring at 33 tree line sites displaying varying degrees of advance. Habitat variables were recorded. ANOVA, GLMM, nestedness analysis and indicator species analysis were used to investigate patterns of species richness and community composition and their association with tree line advance and habitat variables. Results: Species richness was lower in tree lines exhibiting rapid advance; reductions were related to tree size (considered here as a proxy for age) and the distance over which advance had occurred. Community composition varied with tree line form and forest position. Only a subset of species found in slowly advancing or stable forest edges occurred in rapidly advancing tree lines. Main conclusions: Differential migration rates between co-occurring species and differences in habitat structure associated with tree line advance can result in community change, but this depends, amongst other factors, on the speed of tree line advance. The importance of advance rate in determining the response suggests that reductions in species richness at tree line could be transitory. However, this will depend on whether advance continues, and on the changes in habitat associated with advance. Given the complexity of tree line behaviour, the findings that we report represent an essential step in understanding community responses to climate change. This understanding is of importance for biodiversity and conservation, especially given the high rate of endemism reported for this and other alpine regions. © 2016 John Wiley & Sons Ltd.

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Role of geographical provenance in the response of silver fir seedlings to experimental warming and drought

Matías, L., Gonzalez-Díaz, P., Quero, J.L., Camarero, J.J., Lloret, F., Jump, A.S. (2016) Role of geographical provenance in the response of silver fir seedlings to experimental warming and drought. Tree Physiology. 36: 1236-1246.
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Doi: 10.1093/treephys/tpw049

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Functional diversity underlies demographic responses to environmental variation in European forests

Ruiz-Benito, P., Ratcliffe, S., Jump, A.S., Gómez-Aparicio, L., Madrigal-González, J., Wirth, C., Kändler, G., Lehtonen, A., Dahlgren, J., Kattge, J., Zavala, M.A. (2016) Functional diversity underlies demographic responses to environmental variation in European forests. Global Ecology and Biogeography. : 0-0.
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Doi: 10.1111/geb.12515

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Gradual expansion of moisture sensitive Abies spectabilis forest in the Trans-Himalayan zone of central Nepal associated with climate change

Tiwari A., Fan Z.-X., Jump A.S., Li S.-F., Zhou Z.-K. (2016) Gradual expansion of moisture sensitive Abies spectabilis forest in the Trans-Himalayan zone of central Nepal associated with climate change. Dendrochronologia. : 0-0.
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Doi: 10.1016/j.dendro.2016.01.006

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Population structure and tree recruitment dynamics in the natural treeline ecotone of high mountains are strong indicators of vegetation responses to climate. Here, we examined recruitment dynamics of Abies spectabilis across the treeline ecotone (3439-3638. m asl) of Chimang Lekh of Annapurna Conservation Area in the Trans-Himalayan zone of central Nepal. Dendrochronological techniques were used to establish stand age structure by ring counts of adults, and by terminal bud scar count for seedlings and saplings. The results showed abundant seedling recruitment, higher regenerative inertia and colonization with a consistent range shift of the A. spectabilis treeline. The upward expansion of this sub-alpine treeline was found to be driven by a strong dependence of seedling recruitment and radial growth on snowmelt and precipitation as temperatures rise. The radial growth of A. spectabilis at the alpine timberline ecotone (ATE) and closed timberline forest (CTF) showed sensitivity to spring season (March-May) climate. Tree ring indices of CTF showed a strong positive correlation with spring and annual precipitation, and a significant negative correlation with spring and annual temperature, however, moisture sensitivity was less strong at ATE than CTF. © 2016 Elsevier GmbH.

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