Hands-on problem_biome1
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Southeast Missouri State University *
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Course
BI-332
Subject
Geography
Date
Feb 20, 2024
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docx
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7
Uploaded by Selahallen
Hands-On Problem
Advance of the Tree Lines: Biome Boundaries and Climate
Change
(This exercise is based on Harsch M., P. Hulme, M. McGlone and R. Duncan. 2009. Are treelines advancing? A global meta-analysis of treeline response to climate warming
. Ecology Letters 12: 1040–1049.)
INTRODUCTION
In this class on Biomes, we introduce the idea that terrestrial biomes are characterized by the growth forms of the dominant vegetation. The distribution of biomes reflects global patterns of temperature and precipitation (
see figure below
). In areas with low precipitation and low temperatures, we see a transition between the boreal forest biome and the tundra. The boundary between these two biomes is marked by the tree line: an area above which trees do not occur. Tree lines occur at high latitudes (boreal tree line) and high elevations (alpine tree line). In this exercise, we will explore the relationship between tree line locations and changes in temperature.
Textbook Figure 6.2
Biomes vary with average annual temperatures and precipitation. Harsch et al 2009 looked at several hundred studies on changes in tree line. They analyzed data from 166 sites to see if general patterns associated with tree line change could be determined. The authors found that 52% of tree lines were advancing (moving toward higher latitudes or elevations), 1% of tree lines were receding, and the remaining were not changing.
Fig. 1:
Map of locations included in the tree line analysis and whether they were advancing or not. (After M. A. Harsch et al. 2009. Ecol Lett
12: 1040-1049.)
Two predictors emerged from this analysis of tree line advance: Tree lines that experienced strong winter warming were more likely to have advanced, and tree lines with a diffuse form (
Figure 2
) were more likely to have advanced than those with an abrupt form (
Figure 3
).
Fig. 2:
Diffuse-form tree line, California. (Courtesy of Melanie Harsch.)
Fig. 3
: Abrupt-form tree line, New Zealand. (Courtesy of Melanie Harsch.)
An increase in winter temperature may lead to better survival of seedlings over the harsh winter period. Diffuse-form tree lines are less likely than abrupt tree lines to be limited by
factors other than temperature, such as microclimatic conditions or water availability, so as temperatures increase, they will advance more readily.
QUESTIONS
Question 1
Now, let’s look at climate data from a few locations to see if temperature patterns would predict an advance in tree line. You can obtain climate data for locations in the United States from several sources, but one of the most useful for high-elevation sites is the Natural Resources Conservation Service SNOTEL site listed below.
Below are mean daily temperature records for several locations for the three months of winter (December–February).
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Year
Brown
Duck,
UT
Columbine
Pass, CO
Lemhi
Ridge,
MT
Lake
Fork
#1, UT
MF
Nooksack,
WA
Truckee
#2, CA
Indian
Pass
AK
1982
-9.33
1983
-5.33
1984
-6
1985
-6
1986
-4
1987
-10.33
-6
-10.66
-3.66
1988
-10.66
-6.67
-10.66
-5.33
1989
-11.33
-6.33
-11.66
-9.66
1990
-10.33
-5.67
-12.66
-8.33
1991
-10
-5.5
-10
-11
-1
-7
1992
-9
-5.33
-5.33
-10
0.33
-6.66
1993
-11.33
-6.33
-9.67
-12
-1.66
-7.66
1994
-10.33
-6.33
-7.33
-10.66
-1.33
-6
1995
-8.66
-4
-6.33
-10
1
-6.66
1996
-9
-4
-7.33
-9.66
1
0.33
-8.33
1997
-10
-6
-6.67
-10.33
-0.33
0
-5.33
1998
-9.66
-6
-5.67
-10.66
0.66
-1.66
-5.66
1999
-9.33
-4.33
-6.67
-9
-1
-2
-9.33
2000
-8.33
-4.67
-4.67
-8.33
0.66
-0.66
-7.33
2001
-9.33
-5.33
-6
-9.66
0.66
-2
-3
2002
-7.66
-6.33
-6.67
-10.66
-0.33
-1.66
-7.33
2003
-6.33
-5
-4.67
-9.66
3
1.33
-3.33
2004
-8
-6.33
-5.67
-10.33
1.66
0
-6.33
2005
-6.33
-4.67
-4.67
-8.33
3
0.66
-5.66
2006
-8
-4
-6.33
-8
1.66
0.66
-6.66
2007
-7.33
-4.33
-5.67
-8
1.66
-0.33
-8
2008
-9.66
-6.33
-7.67
-10
0.33
-1.33
-8.66
2009
-7.33
-4
-6
-7.66
1
0
-9
2010
-8.33
-5.33
-6.67
-9.66
2.33
0
-3.66
2011
-7.66
-4.66
-6.33
-7.66
1
0.33
-8.33
2012
-7.33
-3.66
-5.66
-8
0.66
1
-8.66
2013
-8.66
-5.33
-6.33
-9.33
0.66
-1
-6
2014
-7.13
-3.7
-6.5
-6.97
-3.17
1.47
-5
2015
-5.07
-1.97
-3.27
-5.7
2.13
2.97
-3.33
2016
-7.07
-3.77
-4.6
-7.63
.5
0.7
-2.97
Harsch and colleagues looked at both winter and summer air temperatures (winter was defined as December–February and summer as June–August for the Northern
Hemisphere) and found that mean winter air temperatures were more predictive of tree line change. Note: data presented in the table above represent winter temperature readings only. In this exercise, we would work in groups to analyze the data and interpret the pattern. To do so, plot mean annual winter temperature over all the years of available data. Draw a best-fit line for the plot to estimate the slope of temperature by year. Do this
for one or two locations.
1. Q.1 i. Do your data show a positive or negative slope? It shows a positive slope overall in Colbine Pass, CO. ii. Would these locations be likely to exhibit an advancing tree line? Why or why not? It would be because the temperature is slightly rising with precipitation which also always for better plant seed survival.
iii. What other factors do you think would be likely to influence tree line dynamics? I think that precipitation, soil quality, and seed distribution can all be positive factors. Other questions
1.
The map shows locations of biomes across the world. To which biome do New Zealand and the southeast section of Australia belong?
Answer___
Temperate evergreen forest
___________________________________
2.
Going south from the Sahara Desert, you would most likely encounter which biome next?
Answer_
Temperate shrubland and woodland
____________________________________
3. Based on the climate diagram above, this location is likely in which biome?
Answer__
Tropical rainforest
_____________________________
4. Using the climate diagram above, a plant requires a minimum of 50 mm of precipitation per month to grow. Its water requirements increase with increasing temperature, such that for every 1°C that the average monthly temperature is above freezing, it requires an additional 1 mm of precipitation. Based on the climate diagram, and assuming the weather reflects long-term climatic averages, this plant should be able to grow during how many months of the year?
a. 6
b. 9
c. 11
d. 12
5. Which biome contains only 11% of Earth’s terrestrial vegetation cover, but is home to about half of Earth’s species?
Answer__
Tropical rainforest______________________________
16. The climate of a certain region is warm to hot, with little seasonal variation in temperature, but with a pronounced dry season. The vegetation is mostly grasses, but there are some shrubs and trees. This region is most likely a
Answer__
Tropical seasonal forest
_______________________________
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6. The blue candle cactus, found in Mexico’s Chihuahuan Desert, and Euphorbia polyacantha
, found in the Eastern Hemisphere, both have succulent upright stems and protective spines. These similar characteristics result from
Answer___
Convergence
___________________________________