Sarah Greenwood

PhD Research Student

BSc (Hons) Ecology University of Aberdeen (2006-2010)

Supervisor: Prof Alistair Jump

Start Date: 1st October 2010

 

email: Sarah Greenwood

Research Project

Shifting species distributions in a warming world: The rising Abies kawakamii treelines of Taiwan    

Funded by the Natural Environment Research Council and conducted in collaboration with the National Pingtung University of Science and Technology (NPUST) and China Medical University (CMU).

Background

Abies kawakamii (Taiwan fir) is the dominant treeline species occurring at high altitudes throughout the Central Mountain Range on the subtropical island of Taiwan. Aerial photography for the period 1975-2001 shows that there have been significant changes to treeline forests with increases in forest density and a range expansion occurring as Abies invades the bamboo grasslands at high altitude. Treeline shifts have been investigated in relation to recent climate change throughout the world but there is a lack of knowledge on far east biogeography and few studies of treeline shifts have been conducted in subtropical regions.

Altitudinal treelines are particularly sensitive to climate change because they represent the upper limit of the climatic tolerance of trees and are mainly temperature limited. An increase in temperature is therefore likely to result in range expansion, this makes treelines ideal indicators of climatic change and useful for determining early responses of species to changing climate condition

Project aims

This project aims to investigate the factors responsible for this shift in species distribution. The response of Abies at the treeline will be investigated on a number of spatial scales in order to better understand the processes by which forests respond to climate and the effects that this change in the distribution of a dominant species is likely to have on associated biodiversity and ecosystem function. The project can be split into several different research topics, as follows:

Tree growth rates in response to climate

A combination of dendroecology and long term climate data will be used to determine how the growth of Abies kawakamii has varied over time in relation to climate. Tree cores will be collected from sites spanning the altitudinal range of the species on Yushan  Mountain, an area for which long term climate data, dating back to the 1940s is available. Standard dendrochronological techniques will be used to analyse the cores for climate signals in the growth pattern of the trees.

Regeneration and microclimate conditions across the treeline ecotone

The establishment of seedlings beyond current forest limits is an understudied but crucial aspect of treeline expansion. The microclimate conditions associated with successful establishment will be investigated by following seedling survival over a number of growing seasons and recording air and soil temperatures with dataloggers. The influence of aspect, slope and surrounding vegetation will also be considered. A digital elevation model (DEM) will be used to explore the relationship between topographic features and regeneration at a wider, landscape scale and the potential for using the DEM coupled with a model of topographic sheltering in order to predict treeline behaviour will be tested

Forest expansion and density changes in relation to climatic warming

Through GIS analysis of aerial photography from the period 1975-2001 in the Hehuan region of the Central Mountain Range, the changes in forest area and density will be analysed and the topographical features associated with these changes will be identified. Coupled with dendroecology this will allow for changes in the forest to be described spatially and temporally at the landscape scale. Climate data for the period will be used to test for correlation between climate variables and forest expansion.

The impact of treeline shifts on associated community composition and diversity

A shift in a dominant species is likely to have impacts on co-occurring species and because species respond in an individualistic manner to their environment, and have varying migration rates and dispersal capacities, climate change could lead to community disassembly and the formation of non analogue communities. From a biodiversity conservation view point it is important to understand how treeline advance will affect forest community diversity. Through biodiversity surveys of epiphytes throughout the treeline ecotone, in both interior forests and in areas with static and advancing treelines, the impact of tree range shifts on epiphytic lichen and bryophyte communities will be investigated.

Treeline shifts and carbon stocking of high altitude forests

Forests represent a significant carbon store, however, as trees respond to climate with altered growth rates and forest area/density changes this is likely to result in changes in the carbon stocking. This will be explored through a combination of remote sensing and GIS technologies and with forest inventory data.

Research interests

My general research interests include forest and alpine ecology, plant physiology and botany (including lichenology and bryology).  Past work has consisted of a study of the effects of forest management on the epiphytic flora of old growth forest in the Bialowieza National Park, Poland.

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