Plant production and soil microbial biomass (SMB) in grassland ecosystems are
linked by flows of carbon (C) and nitrogen (N) between the two groups of organisms. In
native mixed grasslands of the southern Great Plains, these cycles are strongly
influenced by climate. They may also be modulated by the timing and intensity of
disturbances such as fire and clipping. We assessed the relative influence of climate and
disturbance on plant community and soil C and N dynamics. Combined effects of fire
and clipping were assessed in a 2x3 factorial design including spring fire and light
clipping or continuous clipping. Seasonal fire effects were evaluated in a one-way
analysis incorporating spring and fall fire in unclipped plots. Plant cover and biomass
(by functional type), litter mass, SMB C and N, soil density fraction concentration and
composition, soil organic C, total N, and inorganic N, soil temperature and moisture, soil
respiration, and net N mineralization were measured at monthly intervals. C4 grasses
were unaffected by fire or clipping, probably as a result of summer drought in both studyyears. Clipping reduced cover of C3 annual grasses but increased that of C3 perennials,
resulting in no net change in C3 grass biomass. Fire did not affect C3 grass cover or
biomass. Both fire and clipping reduced litter mass. This was reflected in seasonal
declines in SMB C in fire treatments, suggesting that the primary input of microbial C in
this ecosystem occurs by decomposition of current-season plant litter. Litter removal
offers a single mechanism by which fire-induced increases in soil temperature and
reductions in light soil density fraction concentration, soil moisture, and net N
mineralization rates may be explained. Lack of treatment effects on soil respiration rates
suggest that plant roots represent an important component of the plant-soil C cycle, not
quantified in this research. Overall, treatment effects were relatively minor compared to
seasonal climate-related changes in response variables, particularly in light of repeated
summer drought.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/3911 |
| Date | 16 August 2006 |
| Creators | Harris, Wylie Neal |
| Contributors | Boutton, Thomas W. |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | 3459115 bytes, electronic, application/pdf, born digital |
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