02769nas a2200145   4500008004100000245009300041210006900134300001500203490000700218520223400225100001302459700001902472700002002491856011202511       2005                        eng d00aEcological consequences of C4 grass invasion of a C4 grassland: A dilemma for management0 aEcological consequences of C4 grass invasion of a C4 grassland A  a1560 -15690 v153 aMany successful exotic invasive species are functionally distinct from the dominant native species they displace. Occasionally invasion occurs where the exotic species possesses functional traits relatively similar to those of the dominant native. We examined the ecological consequences of such an invasion within a mesic, temperate grassland at the Konza Prairie Long-Term Ecological Research site. We assessed potential changes in carbon (C) and nitrogen (N) cycling and plant diversity following the invasion of a C4 bunch grass species, Andropogon bladhii, into a tallgrass prairie dominated by the native C4 grass species, A. gerardii. In these prairies burning is an important management tool used to maintain native-species dominance. We determined how frequent spring fires affected the impacts of A. bladhii in this system. Over a two-year study our results show that burning regulated the effects that the invasive species has on the native prairie. Compared to the native species, A. bladhii exhibited significantly greater plant biomass, significantly lower pools of soil N, significantly lower rates of decay and C cycling, and higher foliar and root tissue C:N ratio in response to burning. Notable spatial heterogeneity in C and N cycling was evident in areas dominated by the invasive bunch grass. In addition to altered ecosystem processes, areas dominated by the invasive, A. bladhii, had significantly lower plant species diversity. In a grassland ecosystem where burning is an important management tool for controlling exotic-species establishment, maintaining native-species dominance, and increasing productivity, A. bladhii may be able to successfully out-compete the native C4 grass species by using traits typically used to explain the dominance of the native species. With frequent fire, the invasive species has the potential to decrease long-term fertility by lowering N inputs in litter and increasing erosion in non-vegetated soil between bunches, while also having a negative effect on plant diversity. By using fire to promote native C4 grasses and maintain these tallgrass prairies, the threat of invasion by nonnative C4 species may raise a dilemma for future management of these C4 grasslands.1 aReed, H.1 aSeastedt, T.R.1 aBlair, John, M.  uhttp://lter.konza.ksu.edu/content/ecological-consequences-c4-grass-invasion-c4-grassland-dilemma-management03071nas a2200133   4500008004100000245012600041210006900167260004000236300001100276490002100287520246300308100001302771856015302784       2005                        eng d00aEffects of fire and plant invasion on aspects of aboveground and belowground interactions in an eastern tallgrass prairie0 aEffects of fire and plant invasion on aspects of aboveground and  aBoulder, CObUniversity of Colorado  a1 -1720 vPhD Dissertation3 a<p>This thesis is comprised of three studies evaluating whether shifts in soil or plant communities affect each other as well as ecosystem processes. I used contrasting fire regimes and a plant species invasion to test hypotheses regarding the biological effects of composition on decomposition, plant species effects on ecosystem functioning, and root-associated bacterial relationships with plant species. All studies were conducted at the Konza Prairie Biological Station (KPBS), a representative tallgrass prairie ecosystem of the United States. I compared soil biota effects on decomposition and decomposition stability in burned and unburned prairie. Upon assessing effects of soil biota composition on decomposition rates and decomposition stability of various surface and buried substrates, I found no consistent effect of community composition on decomposition or decomposition stability. Rather, a complex interaction between community composition and substrate type mediated responses. Burn regimes influenced the effects of soil communities on decomposition stability and suggested effects on functional stability should be considered when managing ecosystems. The second and third studies used the invasion of Andropogon bladhii, a C4 grass species, onto KPBS to examine whether displacement of a native C4 dominant (Andropogon gerardii ) by the non-native C4 species affects ecosystem properties and community structure. I measured plant species diversity, pools and cycling rates of C and N in native and invasive dominated sites. The invasive species imposes spatial heterogeneity in soil properties, creates a potential to decrease ecosystem N availability, and reduces plant species diversity. A positive response to burning exacerbates this species&#39; ecosystem effects and thwarts management practices to exclude invasive species. Finally, I compared root-associated bacterial communities of each plant species in the first known study to use a molecular phylogenetic approach to examine root-bacteria in a non-agriculture system. The two plant species harbor similar bacteria groups when examined at a broad taxonomic scale; but distinct communities are evident when compared at finer taxonomic resolutions. A large effect on root bacteria as a possible invasion mechanism was not evident, however, the role of these bacteria in assisting the invasive plant in altering biogeochemical properties of the prairie cannot be ruled out.</p>1 aReed, H.  uhttps://instaar.colorado.edu/research/publications/theses-dissertations/effects-of-fire-and-plant-invasion-on-aspects-of-aboveground-and-belowgroun/