|Plants & Human Affairs (BIOL106) - Stephen G. Saupe, Ph.D.; Biology Department, College of St. Benedict/St. John's University, Collegeville, MN 56321; firstname.lastname@example.org; http://www.employees.csbsju.edu/ssaupe|
Are Leaves Good Predictors of Climate?
Objectives: The purpose of this lab is to:
Since plants are stationary they must respond developmentally, and ultimately evolutionarily, to their environment. As a result, it's not surprising that leaf morphology (shape) has been shown to be related to climate. For example, some the following correlations have been reported (Wiemann et al, 1998): (a) leaf length is directly related to the mean annual temperature (MAT), (b) leaf area is directly correlated to both mean annual precipitation (MAP) and MAT; and (c) leaf width is directly correlated with MAP. Thus, leaves are longer and larger in climates with warmer temperatures and higher rainfall.
Another interesting observation that was first reported more than 100 year ago is that woody deciduous plants having leaves with toothed margins (termed serrate) predominate in temperate climates while species with smooth (termed entire) leaf margins predominate in frigid (arctic) and tropical climates. This relationship has been used to derive a mathematical model for predicting climate from leaf margins. This has been particularly useful in determining MAT in the geological past by analyzing the leaf margins of fossil plants.
It is not clear why there should be such a strong correlation between leaf margin and temperature. It is suggested that teeth may help to increase sap flow in plants which may be a benefit in temperate environments.
Wiemann et al, (1998) report that the following equations have been derived to predict MAT (in degrees C) or MAP (in cm) from leaf margin structure (% is expressed as a whole number, not a decimal):
The purpose of today's lab is to test the accuracy of these models for our area.
|Table 1. Margins and size of leaves of native deciduous woody plants in Central Minnesota|
|Common Name||Margin (E = entire or S = serrate)||Leaf Size (L = large > 33 cm2; S = small, < 33 cm2)|
|Table 2. Data Summary|
|species with entire leaves|
|% species with entire leaves [= (# entire/total) x 100)|
|species with large leaves|
|% species with large leaves (= # large lvs / total x 100)|
|Table 3. Predicted MAT for central Minnesota|
|predicted MAT (based on equation 1)|
|predicted MAT (based on equation 2)|
|predicted MAT (based on equation 3)|
|mean MAT (from three equations)|
|Table 4. Predicted MAP for central Minnesota|
|predicted MAP (based on equation 4)|
|Table 5. Actual Climate Data for Central Minnesota|
|MAP||deg C||deg F|
|if web site, date accessed:|
Bailey, IW, EW Sinnott (1916) The climatic distribution of certain types of angiosperm leaves. American Journal of Botany 3: 24 - 39.
Sinnott, EW, IW Bailey (1915) Investigations on the phylogeny of the angiosperms. 5. Foliar evidence as to the ancestry and early climatic environment of the angiosperms. American Journal of Botany 2: 1 - 22.
Wiemann, MC, SR Manchester, DL Dilcher, LF Hinojosa, EA Wheeler (1998) Estimation of temperature and precipitation from morphological characters of dicotyledonous leaves. American Journal of Botany 85: 1796 - 1802.
Wilf, P (1997) When are leaves good thermometers? A new case for leaf margin analysis. Paleobiology 23: 373 - 390.
Last updated: 09/21/2005 � Copyright by SG Saupe