ESSCOSMOS/2009:Diversity

Overview

Humans substantially impact the functioning of ecosystems that we manage. Lawns are a ubiquitous component of suburban development in the United States that was popularized by Frederick Olmstead. As southern California (and other regions) enter into future climates, residents may no longer be able to provide the large amount of water that is required to maintain lawns in such arid environments.

In the arid climate of southern California, the difference between unmanaged and managed ecosystems is easily observed: the grasses in lawns remain green and growing year-round despite the hot dry summer. Meanwhile, the surrounding grassland ecosystems thrive during the wet winter months and become brown and dormant during the summer.

In this activity, we will investigate the impact of lawn management on the abundance and diversity of plants and insects.

Objectives

The objectives of this activity are to:

1. Learn how to measure diversity and calculate diversity indices
2. Observe and calculate the magnitude of human impacts on diversity and abundance
3. Predict the long term consequences (both positive and negative) of maintaining perennially green lawns.

Materials

• Data Sheet
• GPS Device
• TDR probe for measuring soil moisture
• Thermometer for measuring soil temperature
• Trowel
• plastic tubs
• paper plates
• 0.5 x 0.5 m frame for measuring plant diversity
• Data entry form
• Underground Adventure Soil Critter Field Guide
• forceps
• tubes for collecting insects

Methods

Class will be divided into five groups of four, and each group will be responsible for taking data from a single plot at each of the two sites. One pair will collect plant data and the other pair will collect insect data. A total of five plots, one per group, will be studied at each site.

Sites

We will be comparing biodiversity of plants and insects at two sites. The first is an unmanaged grassland, and the second is a lawn within a nearby residential neighborhood.

Soils

soil moisture

• Use probe to measure soil moisture

soil temperature

• Use probe to measure soil temperature

Measuring Biodiversity

Percent Cover

1. toss the 0.5 m x 0.5 m quadrat to a randomly selected location
2. record the identity and percent cover of each plant species
3. for any unknown species, keep a sample to compare with other groups

Insect Diversity

1. Using a trowel, remove a 10 x 10 x 10 cm cube of soil and place it in a bin
2. mix the core well
3. count the number insects in each morphological group
4. replace soil, insects, and grass

Data Collection

Record the latitude and longitude at each site. Record the total number of plant species and the percent cover of each species. For insects, count the total number of groups represented and the number of individuals found in each group.

Results

• For both plants and insects at each site

1. calculate the Species Richness: the total number of species present
2. calculate the Shannon Weiner Index ([math]\displaystyle{ H^\prime }[/math]) of diversity for plants and animals

[math]\displaystyle{ H^\prime = -\sum_{i=1}^S p_i \ln p_i }[/math]

• [math]\displaystyle{ S }[/math] The number of species. Also called species richness.
• [math]\displaystyle{ p_i }[/math] The proportional abundance of each species or group, calculated as the proportion of individuals of a given species to the total number of individuals in the community: [math]\displaystyle{ n_i\over N }[/math]

1. enter these data into the data sheet form for this lab