Scarlett Arana
You must include captions for figures and tables: 8/10.
February 22nd, 2011
GEO 4300
ENVIRONMENTAL BIOGEOGRAPHY
Literature Summary #3
Analysis of vegetation distribution in Interior Alaska and sensitivity to climate
change using a logistic regression approach
1) The full citation reference for the study
Calef, M. P., David McGuire, A., Epstein, H. E., Scott Rupp, T. and Shugart, H. H.
(2005), Analysis of vegetation distribution in Interior Alaska and sensitivity to
climate change using a logistic regression approach. Journal of Biogeography,
32: 863–878. doi: 10.1111/j.1365-2699.2004.01185.x
Monika P. Calef is from the Institute of Arctic Biology, University of Alaska, Fairbanks,
AK, USA; David McGuire is from US Geological Survey, Alaska Cooperative Fish and
Wildlife Research Unit, University of Alaska, Fairbanks, AK; Epstein is from
Department of Environmental Sciences, University of Virginia, Charlottesville, VA,
USA; Scott Rupp and Shugart is from Department of Forest Sciences, University of
Alaska, Fairbanks, AK, USA.
2) The research problem or question (1 or 2 sentences)
What are the current controls on vegetation distribution? What is the sensitivity of
vegetation distribution to changes in climate? What is the sensitivity of vegetation
distribution to changes in fire interval and how do the changes in the fire interval interact
with changes in climate?
3) The general background knowledge leading up to this study (2 sentences)
Due to climate changes from greenhouse gases induced by human activities, there has
been a vegetation response lag in the Northern Hemisphere in the Americas which has
caused a disturbance on the ability for species to disperse and establish themselves.
Scientists have noticed that warming temperatures in high latitudes has not lead to linear
increase in vegetation biomass. The objective is to find changes in vegetation growth due
to changes in season temperature, precipitation and fires.
4) The methods used by the investigators (1 or 2 sentences)
The researchers used a hierarchical logistic regression approach to examine the
equilibrium response of the four major vegetation types (tundra, deciduous forest, black
spruce, white spruce) commonly found in the interior Alaska to find changes in growth
due to temperature, season precipitation, and fire. Logistic regression is used as a
statistical modeling tool to predict the probability of a bivariate response variable based
on a variety of explanatory variables. This aids in risk assessment, habitat evaluation, and
in predicting vegetation distribution.
5) The results of the study (2 sentences and one figure or table)
The results of the findings suggested that tundra vegetation was driven by elevation,
precipitation and latitude south to north, deciduous forest was driven by fire interval and
elevation, black and white spruce was driven by fire interval and elevation. The model
resulted that the black spruce remain the dominant vegetation under all types of scenarios
and increasing with warming climate and fire intervals, however the white spruce growth
was limited by moisture when temperatures exceeded critical limits of more than 2 °C,
deciduous forest expanded when there was decrease in fire, warming in temperature, and
increase in precipitation, and under warming conditions the tundra shows an expansion
under precipitation increase.
Include the caption for figures and tables. I don’t know what these graphs are telling the
reader. -2
6) What are the weaknesses of the study
In my opinion, the research focus mainly on the use of logistic regression model to
explain the trend rather than also focusing on causality of the changes. Using the
equilibrium model does not account for transient dynamics of the vegetation response to
a new climate. More research should be further investigated in order to obtain the overall
picture. This will help determine what may be causing such phenomena, and if such
condition exists, further research will help determine how climate change is linked to
anthropogenic effects.
7) What we learned new from the study (2 sentences)
Applications using logistic regression models to predict vegetation changes in
temperature, precipitation, and fire can be a useful tool to determine prediction for high
altitude regions. Also, climate change is indirectly affecting vegetation through
alternation to soil and fire regimes.