In the southern Great Plains, the encroachment of grassland ecosystems by
mesquite (Prosopis glandulosa), is widespread, and prescribed fire is commonly used in
its control. Despite this, substantial quantitative information concerning their influences
on the community composition, functional dynamics, and soil organic carbon (SOC)
storage potential of grassland ecosystems is lacking. The objectives of this study were to:
a) quantify the effects of seasonal prescribed fire treatments and mesquite encroachment
on aboveground net primary productivity (ANPP) and herbaceous community
composition; b) characterize SOC pool sizes, turnover, and storage potential relative to
vegetation type and fire treatment; c) evaluate the structure and diversity of soil
microbial communities relative to vegetation type; and d) characterize the functional
diversity of these same microbes using the GeoChip functional gene microarray.
Repeated winter and summer fires led to increased ANPP rates (average, 434 and
313 g m-2 y-1, respectively), relative to unburned controls (average, 238 g m-2 y-1),
altered herbaceous community composition, and increased the storage of resistant forms
of SOC, but did not affect overall SOC storage. Herbaceous ANPP rates did not differ
significantly as a result of mesquite encroachment, but herbaceous community
composition and SOC storage did. Mesquite soils contained significantly more total,
slow-turnover, and resistant forms of SOC than those that occurred beneath C3 or C4
grasses. Similarity among the soil bacterial and fungal communities associated with the
major vegetation types in this system was low to moderate. Significant differences were
detected among soil fungi, with the mesquite-associated fungi harboring significant differences in community structure relative to the fungal communities associated with
each of the other vegetation types examined. Despite this result, few significant
differences were detected with respect to the functional diversity of these communities,
suggesting either a high degree of functional redundancy, or that the functional
differences harbored by these communities are beyond the scope of the GeoChip. The
results of this study demonstrate that both fire and mesquite encroachment have the
potential to alter ecosystem components and processes significantly, providing new
insight regarding the effects of these widespread land use and land cover changes on
ecosystem structure and function.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2780 |
| Date | 15 May 2009 |
| Creators | Hollister, Emily Brooke |
| Contributors | Boutton, Thomas W. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | electronic, application/pdf, born digital |
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