Thesis (Ph.D.) - University of KwaZulu-Natal, Pietermaritzburg, 2010. / Full text also available online. Scroll down for electronic link.

Thesis (Ph. D.)--University of Wisconsin--Madison, 2002. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.S.) University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 27, 2007) Includes bibliographical references.

This thesis describes the importance and use of permanent grasslands, or more so-called energy grasses used in the energy sector. For our study we examined these three grasses: Ovsík vyvýšený (Arrhenatherum elatius), Sveřep horský (Bromus carharticus) and Bojínek luční (Phleum pratense). Another, the main task was to determine their resistance to drought. The results based on laboratory work, which between them compared the two variants. One was simulated normal emergence of the species and the second emergence stressed by lack of water. Based on these results, we conclude that we can not say that it would be a downright drought-resistant types. For the two studied species of grasses (Bojínek and Ovsík) are obvious differences in resistance to drought. Sveřep horský (variety - Tacit), however, proved to be the most drought-resistant species. While most sprouted out bojínek luční (variety - Sobol).

Master of Science / Department of Biology / Jesse B. Nippert / The impacts of climate change over the next 100 years on North American grasslands are unknown. Climate change is projected to increase rainfall and seasonal temperature variability, leading to increased frequency of drought and decreased rainfall amounts for many grassland locations in the central Great Plains of North America. To increase our ability to predict the effects of a changing climate, I measured multiple morphological and physiological responses from a diverse suite of C3 and C4 grasses. Due to varying characteristics associated with the different photosynthetic pathways, these grass species respond differently to altered temperature and precipitation. I monitored grass physiology and microanatomy in conjunction with varying watered availability to replicate drought. In the second chapter, I observed leaf-level physiology and root level morphology of C3 and C4 grasses when exposed to 100% water reduction. Results indicated that response to water reduction are not always dependent on the photosynthetic pathway. Root-level morphological measurements were found to vary significantly between species in the same genus; F. ovina had the highest specific root length (SRL), which is an indicator of tolerance to environmental variability. Results also indicated that grasses of interest have thresholds that when passed result in a photosynthetically inactive plant; however it was shown that they are able to recover to near pre-drought gas exchange rates when water is re-applied. The third chapter investigated both leaf-level physiology and morphology in dominant C4¬ grasses across Kansas’ rainfall gradient over the growing season. I hypothesized that variation within a species’ physiology would be greater than its’ morphology. I also hypothesized that morphology would predict variability in a species physiological response to changes in climate. This research discovered within a location and species, leaf morphology is fixed across the growing season. Strong correlations between leaf physiology and morphology were observed, however, the strength and relationship changed among the species compared. A. gerardii and P. virgatum exhibited opposing relationships when comparing their photosynthetic rates to the amount of bundle sheath cells. This result highlights strong species-specific relationship between physiology and morphology. My results illustrate the importance of utilizing plant physiology and morphology to understand how grasses may respond to future climate change scenarios.

Linking annual tree growth with remotely-sensed terrestrial vegetation indices provides a basis for using tree rings as proxies for ecosystem primary productivity over large spatial and long temporal scales. In contrast with most previous tree ring/remote sensing studies that have focused on temperature-limited boreal and taiga environments, here we compare the normalized difference vegetation index (NDVI) with a network of Pinus brutia tree ring width chronologies collected along ecological gradients in semiarid Cyprus, where both radial tree growth and broader vegetation activity are controlled by drought. We find that the interaction between precipitation, elevation, and land-cover type generate a relationship between radial tree growth and NDVI. While tree ring chronologies at higher-elevation forested sites do not exhibit climatedriven linkages with NDVI, chronologies at lower-elevation dry sites are strongly correlated with NDVI during the winter precipitation season. At lower-elevation sites, land cover is dominated by grasslands and shrublands and tree ring widths operate as a proxy for ecosystem-scale vegetation activity. Tree rings can therefore be used to reconstruct productivity in water-limited grasslands and shrublands, where future drought stress is expected to alter the global carbon cycle, biodiversity, and ecosystem functioning in the 21st century.

Macromolecular structures, such as lignin and cellulose, are important components of soil organic carbon, the major terrestrial global carbon pool. The degradation of these macromolecules, including lignin and cellulose, in plant-derived soil organic matter, is important to the global carbon cycle. In grasslands, saprotrophic (decomposer) fungi are major decomposers of such organic material. Some of these compounds, such as lignin are relatively resistant to decay by the microbial community if compared with other compound classes such as cellulose. In this work we investigate the involvement of fungi in the decomposition of both lignin and cellulose and look to link the decomposition processes observed in the field to those observed in a laboratory-controlled environment. The key findings of this work are:- Field based experiments in both tropical and temperate environments indicated that lignin can be degraded completely, most likely by white-rot fungi, as shown by the shifts in the [Ac/Al]S, [Ac/Al]G and [S/G] relative lignin decomposition state proxies. The results confirm that even in a very low carbon environment, fungi are able to completely degrade lignin over time. However, lignin is degraded much faster in tropical environments. Culturing experiments showed that it was possible to isolate a number of fungi present on the degraded wheat straw collected in the field, especially soft-rot fungi. When used in microcosm experiments using a range of organic substrates, the relative lignin decomposition state proxies indicated that Absidia cylindrospora and Trichoderma koningii are not able to completely degrade lignin but preferentially degrade cellulose. Cellulose degradation rates are much higher than those of lignin in degraded field samples over time, confirming previous work.

This investigation has had for its purpose the determination of first, all members of the Gramineae (Grass) family found in the county; second, the incidence of each species with the various types of soil; third, the grazing value of each species; fourth, the life span of the parent plants; fifth, the present grassland status; and sixth, the potentialities of developing desirable grassland.

Livestock management influences the extent to which grazing lands provide resources for native species. We compared how livestock species – sheep or cattle – affected floral resources and bee and butterfly communities in low-diversity, post-Conservation Reserve Program (CRP) pastures managed with patch-burning. We sampled bees and butterflies three times per season 2017-2019 and counted flowering stems within 1 m of transects. Pastures grazed by sheep had significantly fewer flowers and significantly lower floral richness than cattle pastures. Native bees were three to sixteen times more abundant in cattle pastures compared to sheep. Butterfly communities were similar between grazing treatments, because agricultural-tolerant, habitat generalists comprised the majority of the butterfly community. Grassland-obligate butterflies comprised only 2% of observations. The dearth of grassland-obligate butterfly species and low native bee abundances suggest that post-CRP fields, especially those grazed by sheep, do not provide abundant and diverse floral resources for native bees and imperiled butterfly species.

Commercial forestry has expanded across the Rio de la Plata Grasslands (RPG) of South America in recent decades. I conducted a resource-use based study on bird communities during the 2013-2014 austral breeding season in northern Uruguay. I assessed relationships between habitat types and bird abundance as a function of vegetation structure. To compare avian responses to treatments, I included native environments, pine and eucalyptus plantations of different ages and thinning regimes. I detected differences in species richness and composition and species-specific responses in abundance along structural gradients sampled. Although poorer in species than native habitat types, tree plantations were extensively used by birds. Birds associated with plantations were primarily habitat generalists and forest dependent species, with low incidence of grassland specialists. Results of my study provide baseline information for stand-level management and future landscape design of timber plantations to benefit conservation of bird communities in afforested landscapes in the RPG.