Soil community dynamics in sagebrush and cheatgrass-invaded ecosystems of the northern Great Basin Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/m613n0587

Descriptions

Attribute NameValues
Creator
Abstract or Summary
  • Sagebrush steppe ecosystems in the Great Basin have become increasingly threatened by the proliferation of cheatgrass (Bromus tectorum L.), an invasive annual grass. Diverse sagebrush and perennial bunchgrass landscapes can be converted to homogenous cheatgrass grasslands mainly through the effects of fire. Although the consequences of this conversion are well understood in the context of plant community dynamics, information on changes to soil communities has not been well documented. I characterized soil surface, microbial, and nematode community dynamics in sagebrush steppe and cheatgrass-invaded areas across the northern Great Basin. I also examined how restoration treatments, such as seeding with a low impact rangeland drill and applying herbicide or sugar to plots, affected soil communities. Soil community functional diversity and structure were alike at sites where soil pH and percent bare ground were similar. Rangeland drill seeding and associated human trampling decreased biological soil crust cover at sites with high proportions of cyanobacteria. Herbicide treatments had little effect on soil communities, but addition of sugar to plots increased carbohydrate utilization and fungal biomass of cheatgrass- invaded soils. In studying paired intact and cheatgrass-invaded sagebrush plots, I found that microbial functional diversity and community composition were different in sagebrush, bunchgrass, cheatgrass, and interspace soils. Fungal biomass and species richness were highest under sagebrush and decreased under cheatgrass. To examine how soil community shifts might affect ecosystem processes, I investigated the contribution of fungi to inorganic nitrogen (N) mineralization in sagebrush and cheatgrass rhizospheres. Results from a ¹⁵N pool dilution experiment modified with the fungal protein synthesis inhibitor cycloheximide showed that gross and net N cycling rates did not differ between control sagebrush and cheatgrass soils and that fungi were important for gross NH₄⁺ production and consumption in both soil types. However, net nitrification increased in sagebrush soils after 24 h, suggesting that when organic matter decomposition by fungi ceased bacteria became carbon limited and could no longer assimilate NH₄⁺. These studies demonstrate that cheatgrass invasion into sagebrush steppe ecosystems can bring about significant changes to soil communities and that these changes may have repercussions for ecosystem functioning in the northern Great Basin.
Resource Type
Date Available
Date Issued
Degree Level
Degree Name
Degree Field
Degree Grantor
Commencement Year
Advisor
Committee Member
Academic Affiliation
Non-Academic Affiliation
Keyword
Subject
Rights Statement
Language
Replaces
Additional Information
  • description.provenance : Made available in DSpace on 2010-07-09T17:56:07Z (GMT). No. of bitstreams: 1 DeCrappeoNicoleM2010.pdf: 23637652 bytes, checksum: 201c8646434ffb9b1ecf819d6d836461 (MD5)
  • description.provenance : Approved for entry into archive by Laura Wilson(laura.wilson@oregonstate.edu) on 2010-07-09T17:56:07Z (GMT) No. of bitstreams: 1 DeCrappeoNicoleM2010.pdf: 23637652 bytes, checksum: 201c8646434ffb9b1ecf819d6d836461 (MD5)
  • description.provenance : Approved for entry into archive by Julie Kurtz(julie.kurtz@oregonstate.edu) on 2010-07-02T21:24:51Z (GMT) No. of bitstreams: 1 DeCrappeoNicoleM2010.pdf: 23637652 bytes, checksum: 201c8646434ffb9b1ecf819d6d836461 (MD5)
  • description.provenance : Submitted by Nicole De Crappeo (decrappn@onid.orst.edu) on 2010-07-02T20:30:01Z No. of bitstreams: 1 DeCrappeoNicoleM2010.pdf: 23637652 bytes, checksum: 201c8646434ffb9b1ecf819d6d836461 (MD5)

Relationships

In Administrative Set:
Last modified: 08/01/2017

Downloadable Content

Download PDF
Citations:

EndNote | Zotero | Mendeley

Items