Microbial and biogeochemical responses to changing precipitation patterns in grassland ecosystems

2012 Summer.Includes bibliographical references.Global circulation models predict that precipitation patterns in grasslands will both intensify and be characterized by more severe drought in the future. In these systems, the availability of water strongly controls ecosystem function, so changes in precipitation are likely to significantly alter biological communities and biogeochemical dynamics. Since these biogeochemical changes could feed back on climate drivers by influencing regional to global scale energy and water balance, predicted changes in grassland precipitation call for a better understanding of relationships between water availability and grassland biogeochemical dynamics. My dissertation aimed to address how changing rainfall patterns affect biogeochemical cycling and soil microbial communities in grasslands. I first tested the generality of controls over soil organic matter storage in temperate grasslands by studying existing spatial gradients in soil carbon and nitrogen, as they relate to the spatial variation in average precipitation and temperature, and soil texture. I found that statistical models developed in US grasslands overestimated soil organic carbon and underestimated soil organic nitrogen in Chinese grasslands. However, when I incorporated nitrogen deposition and historical land use using a simulation model, it resulted in more accurate model estimates for this region. This work suggests that nitrogen deposition and historical land use legacies may need to be considered to accurately describe biogeochemical dynamics in Chinese grasslands and better predict the vulnerability of global carbon stocks to loss. Responses of ecosystems to changes through time are often somewhat different than relationships gleaned from large-scale spatial gradients. At the local scale, I found that an 11-year drought can significantly alter biogeochemical and ecosystem dynamics in the highly drought-resistant shortgrass steppe. Here, soil inorganic nitrogen availability increased up to 4-fold in plots receiving 25% of summer precipitation. This accumulation of nitrogen under drought may explain the higher plant tissue nitrogen and N2 flux observed under recovery. A more "open" nitrogen cycle that I observed following severe drought could affect the impact of drought on grassland ecosystems, as well as the timescale of recovery. Soil microbial community composition was also altered by this 11-year drought manipulation in the shortgrass steppe, and these differences persisted even after communities were subject to the same moisture conditions for 36 hours in the lab. In this lab experiment, I also identified specific microbial groups that grew under a certain moisture levels, presenting evidence of moisture niche partitioning in microbial communities. However, this niche differentiation wasn't realized in the field; communities that grew under dry conditions in the lab were not similar to those that emerged under long-term drought plots. Overall, this work suggests that contrary to previous assumptions, microbial communities display legacies from long-term field treatments, and that although soil moisture has the potential to drive microbial community composition through niche partitioning, this factor may not always be the primary driver of long-term community composition. Microbial communities were also sensitive to altered precipitation timing in the tallgrass prairie. In addition, communities that were subject to intensified precipitation patterns in the field respired less than control soils after laboratory rewetting events, but respiration rates of the different field treatments converged after 100 days under the same conditions. Surprisingly, species composition of these communities was more sensitive to drying and rewetting pulses in the lab than those from the control. Together, these results show that microbial communities display legacies to altered precipitation timing, in addition to drought, but community composition is not necessarily tightly linked to respiration. Overall, my dissertation work suggests that grasslands will be sensitive to extreme shifts in precipitation, and that biogeochemical and microbial responses could influence how grasslands are altered under future precipitation regimes. However, my work also shows that precipitation is not the only factor controlling biogeochemical and microbial community dynamics in grasslands, even under rainfall manipulations and across precipitation gradients. Therefore, the response of grasslands to other environmental factors - that shift with precipitation changes or are predicted to change independently - should not be overlooked

An Ecological Study of the Anurans in Tea Plantations in a Biodiversity Hotspot

Increasing human population size is increasing the demand for resources like timber, oil, tea, coffee, and other crops. Plantation crops mimic some aspects of native habitats, and there are studies that report the presence of some native anuran biodiversity in plantations. I focused on tea plantations in the Western Ghats-Sri Lanka Biodiversity Hotspot and studied the diversity and health of anurans in different habitats found within a tea cultivation area, near Munnar region in the Western Ghats, India. The landscape includes tea bushes, native evergreen shola forest patches, and eucalyptus forest stands. I reviewed 40 studies comparing amphibian species richness in plantations and primary forests. The age of the plantation, type of plantation, presence in a biodiversity hotspot, number of species in the dominant plantation type, number of species in the paired forest habitat, and latitudinal zone of the study, did not correlate with species richness, but plantations that had periodic harvesting had higher species richness than plantations that practiced clear-cut harvesting. I tested different methods of standard amphibian sampling in the field season 2012 in Munnar, and found that Visual Encounter Surveys (VES) in the shola habitat and Stream Transects (ST) were the most efficient. Using the VES and ST methods, I sampled amphibians in three upland habitats (tea, shola, and eucalyptus) at four different sites, and 150m of stream transects at each site, for two consecutive monsoon seasons. Fourteen species were encountered in both years and the community structure was similar across the years. The community structure at the four sites that was driven by the presence of exclusive species at each site and species composition in streams was similar across the landscape and was driven by the presence of similar species in streams across the four sites. Two hundred and sixteen anurans of 17 species, were tested for the presence of the lethal fungus Batrachochytrium dendrobatidis. The preliminary results from the Polymerase Chain Reactions were negative. My study provides baseline data for anuran diversity, composition, and health in the Munnar region of India and results of this project can be compared with tea plantations around the world

Exploring patterns of phytodiversity, ethnobotany, plant geography and vegetation in the mountains of Miandam, Swat, Northern Pakistan

Das Miandam-Untersuchungsgebiet (35° 1′- 5′ N, 72° 30′-37′ E) liegt in der Swat-Region der Provinz Khyber Pakhtunkhwa (ehemals North West Frontier Province) im nördlichen Pakistan. Die vorliegende Arbeit berücksichtigt sowohl ethnobotanische und pflanzensoziologische Aspekte als auch die Pflanzenartendiversität innerhalb des Gebietes. Aufgrund der hohen Habitatvielfalt weist das Miandam-Gebiet einen großen Reichtum von Medizinalpflanzen auf. Die im Rahmen der Arbeit durchgeführte ethnobotanische Studie dokumentiert das Vorkommen der Medizinalpflanzen sowie deren Nutzung in der Region. Weiterhin wurden die durch Sammlerpräferierten Lebensräume bestimmt und evaluiert inwiefern die Heilpflanzen durch Sammlung und Habitatzerstörung bedroht werden. Insgesamt wurden 106 traditionelle Heilpflanzen aus 54 Pflanzenfamilien verzeichnet. Zu den am häufigsten gefundenen Wuchsformen zählten mehrjährige (43%) und kurzlebige Kräuter (23%), Sträucher (16%) und Bäume (15%). Ein Großteil der untersuchten Heilpflanzen und ihrer Produkte wird zur Behandlung von Magen-Darm-Erkrankungen eingesetzt. Die Produkte werden vorrangig als Sud oder Pulver zubereitet und oral angewendet. Achtzig der 106 traditionellen Heilpflanzen gehören der Gruppe der einheimischen Arten an. Fast 50% der Pflanzenarten treten dabei in synanthroper Vegetation auf, während der Rest in naturnaher Umgebung (z.B. extensiv beweidete Wald- und Graslandbereiche) vorgefunden werden kann. Wälder sind der Ursprung der meisten nicht synanthropen einheimischen Medizinalpflanzen. Drei Arten (Aconitum violaceum, Colchicum luteum, Jasminum humile) können als Folge intensiven Sammelns als bedroht eingestuft werden. Um die pflanzensoziologischen und phytogeografischen Aspekte des Projektes abzudecken wurde die Vegetation des Miandam-Gebietes mit einem Fokus auf Wäldern, Gebüschen und anderen Formationen untersucht. Die Ergebnisse der Vegetationserhebungen wurden mit denen anderer Studien in der weiteren Umgebung des Hindukush-Himalayas verglichen. Weiterhin wurde untersucht inwiefern die Waldökosysteme durch anthropogene Aktivitäten im Untersuchungsgebiet bedroht sind. Die im Gebiet verzeichneten Gefäßpflanzenarten umfassen insgesamt 33 Bäume, 52 Sträucher, 305 Kräuter und 11 Lianen. Basierend auf einer multivariaten Analyse konnten 12 Pflanzengesellschaften identifiziert werden. Die Spanne dieser Gesellschaften reichte von subtropischen semiariden Wäldern mit Ailanthus altissima im Tiefland zu alpinen Rasen von Sibbaldia cuneata durchsetzt mit Juniperus. Die dominierende Vegetation des Untersuchungsgebietes besteht aus von Abies pindrow und Viburnum grandiflorum Wäldern. Eine georeferenzierte Karte der Vegetation erleichtert die Lokalisierung der ökologisch interessanten Vegetation. Artenreichtum und –diversität wurden entlang eines Höhengradienten untersucht. Dazu wurde die Alpha- sowie Beta-Diversität verschiedener Wuchsformtypen bestimmt. Der Artenreichtum aller Gefäßpflanzenarten erreichte sein Maximum zwischen 2200-2500 m. Dagegen zeigte der Artenreichtum der Sträucher einen glockenkurvenartigen Verlauf mit einem Maximum zwischen 2000 und 2200 m. Die höchste Alpha-Diversität der Gefäßpflanzenarten wurde in den tieferen Lagen des Untersuchungsgebietes verzeichnet. Die Beta-Diversität aller Wuchsformtypen zeigte entlang des gesamten Höhengradienten hohe Werte und somit einen starken Artenwechsel. Die Beta-Diversität der Straucharten fluktuiert entlang des Höhengradienten und zeigt damit ein einzigartiges Muster

Historic Ohlone Resource Distribution within the Alameda Creek Watershed

The Alameda Creek watershed is located within the ancestral homeland of the Muwekma Ohlone Tribe of the San Francisco Bay Area. Their ancestors historically utilized a variety of plants for food, medicine, ceremonies, and building materials, with their understanding of the value of the plants based on traditional ecological knowledge (TEK). The arrival of Spanish, and later Anglo/American, colonists beginning in the mid-18th century introduced urbanization and European agricultural practices, which have degraded wildlands and impacted species richness and diversity. As interest in environmental restoration has been increasing in recent decades, the present-day Muwekma Ohlone Tribe has an opportunity to once again access ancestral lands and educate the public on their TEK practices. A vegetation survey was conducted to analyze the distribution of historic plant resources, native plants species, and non-native species in a riparian corridor in the Alameda Creek watershed. Areas with greater anthropogenic land use, specifically grazed lands and seasonal service roads, had the lowest levels of biodiversity, traditional plant resources, and native species presence. Undisturbed and restored sections of the corridor, in contrast, were found to have the greater amounts of resource presence and diversity. Although the effects of Western urban expansion have drastically altered the traditionally managed environment, reintroducing Ohlone TEK could help support ecological biodiversity and allow a marginalized group to reclaim their culture and traditions

Hunting and conservation of forest pigeons in São Tomé (West Africa)

Doutoramento em Biologia - Instituto Superior de AgronomiaOn the island of São Tomé, four endemic species of fruit pigeons are hunted as food and/or as an economic resource. This thesis intended to collect and analyze the baseline data required for the management of pigeons, which take into account their importance as a resource but also their overall conservation value. For this, I used a combination of biological and social sampling methods. The results show that harvest of endemic pigeons is performed predominantly for commercial purposes by a small and specialized group of hunters, but is also widely practiced opportunistically by most hunters and rural inhabitants. The hunting pressure on the two least abundant species already determines their patterns of distribution and abundance, and their extraction is probably unsustainable. Harvesting of the most hunted species is potentially sustainable, but more research is essential to the definition of measures to manage the species. Only one species is not commercially hunted and exploitation for subsistence is sustainable. The conservation of the species on the long term requires the development of specific measures; it is essential to promote legal restrictions on hunting and trading, to search for economic alternatives for bird hunting and define strategies of education / awareness of consumersFCT - PhD grant and the I&D project “Endemic pigeons of São Tomé: developing science-based conservation and sustainable use of African pigeons

Driving Forces of Forest Expansion Dynamics across the Iberian Peninsula (1987-2017) : A Spatio-Temporal Transect

This study analyzes the spatio-temporal dynamics of the drivers of forest expansion in the Iberian Peninsula for the periods 1987-2002-2017 through a 185 km-wide north-south Landsat scene transect. The analysis has considered a variety of biogeographical regions [0-3500 m.a.s.l, annual rainfalls 150-2200 mm] and 30 explanatory variables. A rigorous map production at 30 m resolution, including detailed filtering methods and uncertainty management at pixel scale, provided high-quality land cover maps. The main forest expansion trajectories were related to explanatory variables using boosted regression trees. Proximity to previous forests was a key common factor for forest encroachment in all forest types, with other factors being distance to the hydrographic network, temperature and precipitation for broadleaf deciduous forests (BDF), precipitation, temperature and solar radiation for broadleaf evergreen forests (BEF) and precipitation, distance to province capitals, and solar radiation for needleleaf evergreen forests (NEFs). Results also showed contrasting forest expansion trajectories and drivers per biogeographic region, with a high dynamism of grasslands towards new forest in the Eurosiberian and the mountainous Mediterranean regions, a high importance of croplands as land cover origin of new forest in the Mesomediterranean, and increasing importance over time of socioeconomic drivers (such as those employed in the industry sector and the utilized agricultural area) in the Supramediterranean region but the opposite pattern in the Southern Mesomediterranean. Lower precipitation rates favored new NEFs from shrublands in the Thermomediterraean region which, together with the Northern Mesomediterranean, exhibited the highest relative rates of new forests. These findings provide reliable insights to develop policies considering the ecological and social impacts of land abandonment and subsequent forest expansion

Mountain and meadow: A reconstruction of long-term pastoralist ecology in the Kashmir Valley

The cultural history of the Kashmir Valley in the Western Himalayas spans at least 4500 years, beginning with some of the known Neolithic Agricultural villages in the mountainous regions of the northern Indian Subcontinent. The development of agriculture in the valley, and subsequent periods of cultural expansion have been attributed to economic growth that capitalised on warm-humid climate phases in the region, often followed by periods of supposed social collapse driven by the onset of cold-arid conditions. More recently, Kashmiri archaeologists have argued that these near-Malthusian interpretations result from a methodological focus on a handful of large sites, and that the Kashmir Valley contains multiple ecological niches suitable for a wide range of economic or ecological adaptation. This study seeks to build on palaeoenvironmental and archaeological data that suggests a more complex picture of social and ecological change in the valley. Rather than using archaeological remains, this study draws on environmental signatures of pastoralist usage, enrichment or modification of environmental niches at middle and high altitudes, primarily on the western flank of the Kashmir Valley. These data include changes in pollen spectra, charcoal and fungal spore accumulation or sediment deposition that are indicative of pastoralist activity in mountain regions, and are interpreted through the lens of niche construction theory. The results indicate that pastoralist land usage in the upland areas of Kashmir was spatially and temporally discontinuous, and likely entangled with other environmental and historical processes. Stronger signatures for pastoralism often appear contemporary with drier conditions and periods of regional agricultural intensification, indicating that upland summer season herding may be an adaptive strategy to mitigate other ecological or economic pressures