Name:________________________________________________             Section:________________

part 1:  Bioclimatic Transects

            Six sites comprise a transect (a transect is simply a route along which you make observations) across latitude, as shown in Figure 13.2.  The latitudinal transect crosses almost 10,000 kilometers, but all six sites are within 550 meters of sea level. 

Figure 13.2  Data Collection Sites

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


1.   Complete Table 13.2 for sites along the middle longitudes of North America.  Climatic data are found in Table 13.3.  Calculate the climatic index variables to the nearest .01, then use the Life Zone Triangle to predict vegetation and other zones.  Use an atlas vegetation map and photographs (Figure 13.4) to confirm or refute the initial predictions.  Kugluktuk is complete as an example. 

TABLE 13.2  Latitude Transect for Central North America

 

 

Kugluktuk

 

Hay River

 

Williston

 

Concordia

New Orleans

 

Merida

TB

2.08

4.49°C

8.05°C

12.32

20.58°C

25.83°C

PE

121.53

262 mm

470 mm

720 mm

1203 mm

1509 mm

PE/P

0.51

0.80

1.31

1.06

0.79

0.95

Life Zone

tundra

Forest

Grassland

Savanna

Forest

Savanna

Growing Zone

frigid

Cold

Cool

Warm

Warm

Hot

Altitude Zone

alpine

Subalpine

Montane

Foothills

Foothills

Lowland

Latitude Zone

subarctic

Boreal

Temperate

Subtropical

Subtropical

Tropical

Map Community

tundra

Taiga

Grassland

Grassland

Broadleaf forest

Savanna

Photograph Community

tundra

Taiga

Grassland

Grassland

Broadleaf forest

Woodland Savanna

TABLE 13.3  Mean Monthly Climate Data for the Latitude Transect

             Jan       Feb      Mar      Apr     May       Jun        Jul      Aug       Sep      Oct     Nov      Dec

Hay River, Northwest Territories (61°N, 116°W, elevation 166m)

T (°C)     -25        -22        -17         -4          5         11         16         14          8          0        -12        -21

P (mm)    19         17         16         16         22         31         40         43         38         21         31         22

Williston, North Dakota (48°N, 104°W, elevation 549m)

T (°C)     -13        -11         -4          6         12         17         21         20         14          7         -2         -9

P (mm)    13         11         19         29         47         77         49         37         31         19         14         13

Concordia, Kansas (40°N, 098°W, elevation 454m)

T (°C)       -3          0          5         12         17         23         26         25         20         14          5          0

P (mm)    15         22         40         57       105       111         86         82         69         47         26         18

New Orleans, Louisiana (30°N, 090°W, elevation 1m)

T (°C)      12         14         17         20         24         27         28         28         26         22         16         13

P (mm)  118        119       129       124       117       145       171       156       132         84       100       122

Merida, Yucatan (21°N, 090°W, elevation 22m)

T (°C)      23         24         26         27         28         28         27         27         27         26         24         23

P (mm)    63         92         24         47         96       189       130       150       223       269       174       130

2.   How consistently are the predicted vegetation communities correct, as verified by documentary data, for the latitudinal transect?

a.   Number of sites correct (out of six):     4/6

b.   List any erroneous sites:           Concordia, possibly New Orleans (marsh)

 

c.   What might account for the mispredictions at any erroneous sites?

Concordia:  marginal life zone position near savanna/grassland/forest boundary

New Orleans:  marginal location near marsh on map

 

3.   How consistently are the biotemperature zones (to left side of the triangle) correct, as verified by documentary data, for the latitudinal transect?

a.   Number of sites correct (out of six): 6/6

b.   List any erroneous sites: none

 

c.   What might account for the mispredictions at any erroneous sites?

 

 

 

4.   a.   What is the gradient of mean annual temperature (MAT) across the 47° of latitude difference between Kugluktuk and Merida?  (Retain any signs!)

     MAT2 – MAT1         =

Latitude2 – Latitude1

(-11.4 – 25.8)/(68 – 21) = - 0.79°C [per1°latitude]

b.   What is the gradient of mean annual biotemperature (TB) across the 47° of latitude difference between Kugluktuk and Merida?  (Retain any signs!)

         TB 2 – TB 1               =

Latitude2 – Latitude1

(2.04-25.8)/(68-21) = - 0.51°C [per1°latitude]

 

c.   Why is the biotemperature gradient less than the MAT gradient?

TB is only for the “growing season”, and ignores temperatures <0.  During the summer growing season temperature fradients across latitude are smaller than in winter.

 

5.   What generalization can you make about the progression of life zones from low to high latitude along this central North America transect?

Tropical/subtropical forests, then continental interior grasslands, then subarctic needleleaf forest (taiga), and finally tundra

6.   Table 13.4 provides data for a latitude transect along the west coast of North America. 

TABLE 13.4  Latitude Transect for Western North America

 

Fairbanks, Alaska (65°N, 148°W, elevation 147m)

Sitka, Alaska (57°N, 136°W, elevation 20m)

Vancouver, British Columbia (49°N, 123°W, elevation 3m)

Eureka, California (41°N, 124°W, elevation 13m)

El Rosario, Baja California (30°N, 115°W, elevation 82m)

Manzanillo, Colima (19°N, 105°W, elevation 3m)

TB

4.92

6.33

9.82

11.14

22.46

26.48

PE

287.28

369.57

573.79

651.01

1312.24

1547.42

PE/P

0.91

0.16

0.52

0.67

7.36

1.52

Life Zone

forest

rainforest

forest

forest

hot desert

savanna

Growing Zone

cold

cool

cool

cool

warm

hot

Altitude Zone

subalpine

montane

montane

montane

foothills

lowland

Latitude Zone

boreal

temperate