Assignment 1

Contrasting ecosystem functioning on the UTM campus
 

This assignment is due in lecture on Friday January 28th and is worth 5% of the course grade. The late penalty is 10% per day, including weekend days. Assignments will not be accepted more than 4 days late (i.e. after 5pm on Tuesday February 1st), resulting in a mark of zero. There is a drop box outside the Geography main offices where late assignments must be turned in.


Introduction:

Ecosystem form or type based on dominant vegetation (e.g. grassland versus forest) and position on the landscape (e.g. wetland versus upland) has important implications regarding how ecosystems function and in particular how biotic components interact with physical components. Soil temperature is an important ecosystem parameter that in part determines the rate of organic matter decomposition by soil microorganisms including the release of carbon dioxide (the predominant mineral form of carbon) to the atmosphere and production and release of mineral forms of nutrients that supports future plant growth.

Across large spatial scales, climate conditions broadly determine differences in soil temperature (for example between arctic tundra and tropical forest systems). Within smaller regions however, physical and biological ecosystem characteristics play important roles in controlling soil temperature. Some important ecosystem properties that can influence soil temperature are (1) the stature and leaf area of dominant vegetation in an ecosystem that can block direct sunlight from reaching the soil, or exposed dark soil with a very low albedo that absorbs light; (2) rates of photosynthesis, which involves transpiring water that can keep a microenvironment cooler (i.e. energy is used to evaporate water instead of increasing temperature and water has a high heat of vaporization); (3) proximity to open water and presence of flooded soils can buffer changes in air temperature (H-bonding of water leads to a very high specific heat capacity); (4) during cold parts of the year, insulation in the form of a snowpack or fallen leaf or plant litter can play an important role in keeping soil warmer than air temperature and in many cases prevents hard freezing of soils.

In this assignment, real soil temperature data collected on the UTM campus across 3 contrasting ecosystems (a wetland, a grassland, and a forest) will be analyzed and interpreted to illustrate how ecosystem type mediates changes in soil temperature. The instructor will present an overview of the 3 ecosystems and monitoring equipment as well as give advice about the assignment in lecture on Friday January 21st. The TA who will mark the assignments, Varun Gupta, and the head TA will hold an optional tutorial focusing on data analyses using Microsoft Excel from 6-8pm on Monday January 24th in CCT 2160.


Objectives:

To access, analyze, and interpret environmental data collected across the UTM campus to address how soil temperatures vary across contrasting ecosystems (a wetland, grassland, and forest) during and after the 2010 growing season.


Specific instructions:

Data access, analysis, and graphing:

As well as this sheet, please refer to material presented in lecture on Friday January 21st.

Download or cut and paste the appropriate data needed below as/into a Microsoft Excel spreadsheet file. It will be easiest to cut and paste needed data into a new worksheet that has all of the sites on the same sheet. Data are accessible from the UTM Geography main page (http://www.utm.utoronto.ca/geography) under the menubar “Resources” and then “Environmental Datasets”. Note that ‘pond’ refers to the marsh adjacent to the pond, and ‘field’ refers to the grassland. Data are listed by calendar date and values are hourly averages listed using a 24hr time notation where 0:00 is midnight and represents the average recorded value from 0:00 to 1:00. Other campus weather data from a tall meteorological station are in the same “Resources” menubar under “Meteorological Station” and note that data here must be cut and pasted from html format in to Microsoft Excel. Data from the weather station are listed by Julian day (e.g. December 31 = 365 in a non-leap year) in 24-hour time format, though midnight is listed as 24:00 (and this value represents the 24:00 or 0:00 to 1:00 hour) and there is a second 24:00 value listed that is the daily average. There are 2 data formats for the UTM weather station: be sure to access and use format 1, which represents mean values of the hour time periods (in contrast to maximum or minimum values reported in format 2).

For the date of July 29, 2010 or Julian day 210 (i.e. mid summer), create a line graph or scatterplot with points connected by lines with time in hours on the x-axis and average hourly soil temperature in degrees C on the y-axis beginning at midnight and extending through the 23:00 hour (24 data points per site in total) for soil temperature in each of the three ecosystems and the air temperature from the met station that represents the average weather condition on campus. Soil temperature in each ecosystem and air temperature should be clearly represented by a unique data series and symbol or line color that is shown in a legend. Label this graph “Figure 1” as well as with an appropriate, succinct title.

Repeat for the date of December 24, 2010 or Julian day 358 (i.e. early winter). Note that by this date all of the deciduous trees in the forest had lost their leaves and both grasses and sedges in the grassland and marshes were brown and partially fallen on the soil surface. On this date, there was no snow cover in the marsh and grassland and a small snow cover in the forest. Label this graph “Figure 2” as well as with an appropriate, succinct title.

Both graphs must be labeled with a clear, legible, and appropriate figure title, axis titles, axis labels, and legend (adjust scale and font sizes appropriately). Figures may be printed on the same sheet as long as they are clearly legible. They must be handed in as well as the interpretation questions below.

If you are struggling with MS Excel, hand drawn to scale figures on graph paper are acceptable, but must be clearly legible.

Answer (typed/printed) the following short questions within the space provided (or the equivalent of 10 lines at 12pt Times New Roman Font).

Interpretation:

1) Based on Figure 1 for a clear summer day, which ecosystem experiences the most, intermediate, and the least diurnal (i.e. daily recurring or day-night) temperature fluctuation in relation to the air temperature? Briefly explain why these differences might exist between the three ecosystems (point form is acceptable).

2) For a cold early-winter day, do the same diurnal patterns still exist as in summer in general? Are there differences between the three ecosystems at this time and if so or if not, explain why (point form is acceptable).