Symmetry, intensity, and additivity: Belowground interactions in an early successional field.

Format:

Book

Thesis/Dissertation

Author/Creator:

Cahill, James F., Jr.

Contributor:

Casper, Brenda B., advisor.

University of Pennsylvania.

Language:

English

Subjects (All):

Ecology.

Botany.

0309.

0329.

Penn dissertations--Biology.

Biology--Penn dissertations.

Local Subjects:

Penn dissertations--Biology.

Biology--Penn dissertations.

0309.

0329.

Physical Description:

186 pages

Contained In:

Dissertation Abstracts International 58-07B.

System Details:

Mode of access: World Wide Web.

text file

Summary:

Although competition for belowground resources can reduce plant growth, surprising little work has been conducted characterizing the effects of belowground competition and soil resource distributions on population and community level dynamics in natural communities. Several field and pot experiments were conducted to: (1) Measure the effects of soil resource heterogeneity on interspecific encounters, (2) Characterize the intensity and symmetry of belowground competition, and (3) Determine how above- and belowground interact to affect plant growth in a natural community. Localized resource distributions were found to increase plant size when plants were grown individually, but it had no effect when plants were grown in interspecific mixtures. Using a novel technique to manipulate the ability of neighbor roots to interact with target plants, a strong correlation was found between neighbor root biomass and belowground competitive intensity. The form of this interaction suggests exploitative belowground competition is symmetric. Results also suggest that small variations in root biomass could lead to large variations in the intensity of belowground competition.. This was confirmed in a field study which found a reduced intensity of belowground interactions inside of gaps than within the surrounding vegetation. Small gaps may have important community level effects as "safe-sites" for poor belowground competitors. Finally, belowground and aboveground competition were shown to interact in a non-additive manner to affect plant growth. In unfertilized plots, the actual intensity of competition was less than the sum of aboveground and belowground competition when measured independently, with fertilization total competitive intensity was greater then the sum of above- and belowground competition. When fertilized, aboveground interactions with neighbors had no effect on plant growth for plants growing in the absence of belowground interaction. Only when belowground interactions were present was the net effect of aboveground interactions negative. If we are to understand competition in natural systems it is essential we allow for the existence of non-additive and complex interactions between above- and belowground competition.

Notes:

Thesis (Ph.D. in Biology) -- University of Pennsylvania, 1997.

Source: Dissertation Abstracts International, Volume: 58-07, Section: B, page: 3425.

Supervisor: Brenda B. Casper.

Local Notes:

School code: 0175.

ISBN:

9780591501247

Access Restriction:

Restricted for use by site license.