Matching Items (11)

150070-Thumbnail Image.png

Vegetation modeling of Holocene landscapes in the southern Levant

Description

This dissertation creates models of past potential vegetation in the Southern Levant during most of the Holocene, from the beginnings of farming through the rise of urbanized civilization (12 to

This dissertation creates models of past potential vegetation in the Southern Levant during most of the Holocene, from the beginnings of farming through the rise of urbanized civilization (12 to 2.5 ka BP). The time scale encompasses the rise and collapse of the earliest agrarian civilizations in this region. The archaeological record suggests that increases in social complexity were linked to climatic episodes (e.g., favorable climatic conditions coincide with intervals of prosperity or marked social development such as the Neolithic Revolution ca. 11.5 ka BP, the Secondary Products Revolution ca. 6 ka BP, and the Middle Bronze Age ca. 4 ka BP). The opposite can be said about periods of climatic deterioration, when settled villages were abandoned as the inhabitants returned to nomadic or semi nomadic lifestyles (e.g., abandonment of the largest Neolithic farming towns after 8 ka BP and collapse of Bronze Age towns and cities after 3.5 ka BP during the Late Bronze Age). This study develops chronologically refined models of past vegetation from 12 to 2.5 ka BP, at 500 year intervals, using GIS, remote sensing and statistical modeling tools (MAXENT) that derive from species distribution modeling. Plants are sensitive to alterations in their environment and respond accordingly. Because of this, they are valuable indicators of landscape change. An extensive database of historical and field gathered observations was created. Using this database as well as environmental variables that include temperature and precipitation surfaces for the whole study period (also at 500 year intervals), the potential vegetation of the region was modeled. Through this means, a continuous chronology of potential vegetation of the Southern Levantwas built. The produced paleo-vegetation models generally agree with the proxy records. They indicate a gradual decline of forests and expansion of steppe and desert throughout the Holocene, interrupted briefly during the Mid Holocene (ca. 4 ka BP, Middle Bronze Age). They also suggest that during the Early Holocene, forest areas were extensive, spreading into the Northern Negev. The two remaining forested areas in the Northern and Southern Plateau Region in Jordan were also connected during this time. The models also show general agreement with the major cultural developments, with forested areas either expanding or remaining stable during prosperous periods (e.g., Pre Pottery Neolithic and Middle Bronze Age), and significantly contracting during moments of instability (e.g., Late Bronze Age).

Contributors

Agent

Created

Date Created
  • 2011

154001-Thumbnail Image.png

Understanding environmental change and biodiversity in a dryland ecosystem through quantification of climate variability and land modification: the case of the Dhofar cloud forest, Oman

Description

The Dhofar Cloud Forest is one of the most diverse ecosystems on the Arabian Peninsula. As part of the South Arabian Cloud Forest that extends from southern Oman to Yemen,

The Dhofar Cloud Forest is one of the most diverse ecosystems on the Arabian Peninsula. As part of the South Arabian Cloud Forest that extends from southern Oman to Yemen, the cloud forest is an important center of endemism and provides valuable ecosystem services to those living in the region. There have been various claims made about the health of the cloud forest and its surrounding region, the most prominent of which are: 1) variability of the Indian Summer Monsoon threatens long-term vegetation health, and 2) human encroachment is causing deforestation and land degradation. This dissertation uses three independent studies to test these claims and bring new insight about the biodiversity of the cloud forest.

Evidence is presented that shows that the vegetation dynamics of the cloud forest are resilient to most of the variability in the monsoon. Much of the biodiversity in the cloud forest is dominated by a few species with high abundance and a moderate number of species at low abundance. The characteristic tree species include Anogeissus dhofarica and Commiphora spp. These species tend to dominate the forested regions of the study area. Grasslands are dominated by species associated with overgrazing (Calotropis procera and Solanum incanum). Analysis from a land cover study conducted between 1988 and 2013 shows that deforestation has occurred to approximately 8% of the study area and decreased vegetation fractions are found throughout the region. Areas around the city of Salalah, located close to the cloud forest, show widespread degradation in the 21st century based on an NDVI time series analysis. It is concluded that humans are the primary driver of environmental change. Much of this change is tied to national policies and development priorities implemented after the Dhofar War in the 1970’s.

Contributors

Agent

Created

Date Created
  • 2015

150960-Thumbnail Image.png

Quantifying percent-cover in Prescott National Forest, Arizona through the integration of Landsat imagery, vegetation Indices, and spatial transformations

Description

Accurate characterization of forest canopy cover from satellite imagery hinges on the development of a model that considers the level of detail achieved by field methods. With the improved precision

Accurate characterization of forest canopy cover from satellite imagery hinges on the development of a model that considers the level of detail achieved by field methods. With the improved precision of both optical sensors and various spatial techniques, models built to extract forest structure attributes have become increasingly robust, yet many still fail to address some of the most important characteristics of a forest stand's intricate make-up. The objective of this study, therefore, was to address canopy cover from the ground, up. To assess canopy cover in the field, a vertical densitometer was used to acquire a total of 2,160 percent-cover readings from 30 randomly located triangular plots within a 6.94 km2 study area in the central highlands of the Bradshaw Ranger District, Prescott National Forest, Arizona. Categorized by species with the largest overall percentage of cover observations (Pinus ponderosa, Populus tremuloides, and Quercus gambelii), three datasets were created to assess the predictability of coniferous, deciduous, and mixed (coniferous and deciduous) canopies. Landsat-TM 5 imagery was processed using six spectral enhancement algorithms (PCA, TCT, NDVI, EVI, RVI, SAVI) and three local windows (3x3, 5x5, 7x7) to extract and assess the various ways in which these data were expressed in the imagery, and from those expressions, develop a model that predicted percent-cover for the entire study area. Generally, modeled cover estimates exceeded actual cover, over predicting percent-cover by a margin of 9-13%. Models predicted percent-cover more accurately when treated with a 3x3 local window than those treated with 5x5 and 7x7 local windows. In addition, the performance of models defined by the principal components of three vegetation indices (NDVI, EVI, RVI) were superior to those defined by the principal components of all four (NDVI, EVI, RVI, SAVI), as well as the principal and tasseled cap components of all multispectral bands (bands 123457). Models designed to predict mixed and coniferous percent-cover were more accurate than deciduous models.

Contributors

Agent

Created

Date Created
  • 2012

150777-Thumbnail Image.png

Zingiberalean fossils from the late Paleocene of North Dakota, USA and their significance to the origin and diversification of Zingiberales

Description

The Zingiberales, including the gingers (Zingiber), bananas (Musa) and ornamental flowers (Strelitzia, Canna, and Heliconia) are a diverse group of monocots that occupy the tropics and subtropics worldwide. The monophyly

The Zingiberales, including the gingers (Zingiber), bananas (Musa) and ornamental flowers (Strelitzia, Canna, and Heliconia) are a diverse group of monocots that occupy the tropics and subtropics worldwide. The monophyly of the order is well supported, although relationships between families are not well resolved. A rapid divergence of the Zingiberales has been proposed to explain the poor resolution of paraphyletic families in the order, and direct fossil evidence shows members of both of these lineages of Zingiberaceae and Musaceae were present by the Late Cretaceous. Comparisons of the fossils with extant relatives and their systematic placement have been limited because variation within modern taxa is not completely known. The current study focuses on describing zingiberalean fossil material from North Dakota that includes seeds, leaves, buds, adventitious roots and rhizomes. A survey of extant zingiberalean seeds was conducted, including descriptions of those for which data were previously unknown, in order to resolve the taxonomic placement of the fossil material. Upon careful examination, anatomical characters of the seed coat in fossil and extant seeds provide the basis for a more accurate taxonomic placement of the fossils and a better understanding of character evolution within the order.

Contributors

Agent

Created

Date Created
  • 2012

151900-Thumbnail Image.png

Assessment of environmental change in the Near Eastern Bronze Age

Description

This dissertation research investigates both spatial and temporal aspects of Bronze Age land use and land cover in the Eastern Mediterranean using botanical macrofossils of charcoal and charred seeds as

This dissertation research investigates both spatial and temporal aspects of Bronze Age land use and land cover in the Eastern Mediterranean using botanical macrofossils of charcoal and charred seeds as sources of proxy data. Comparisons through time and over space using seed and charcoal densities, seed to charcoal ratios, and seed and charcoal identifications provide a comprehensive view of island vs. mainland vegetative trajectories through the critical 1000 year time period from 2500 BC to 1500 BC of both climatic fluctuation and significant anthropogenic forces. This research focuses particularly on the Mediterranean island of Cyprus during this crucial interface of climatic and human impacts on the landscape. Macrobotanical data often are interpreted locally in reference to a specific site, whereas this research draws spatial comparisons between contemporaneous archaeological sites as well as temporal comparisons between non-contemporaneous sites. This larger perspective is particularly crucial on Cyprus, where field scientists commonly assume that botanical macrofossils are poorly preserved, thus unnecessarily limiting their use as an interpretive proxy. These data reveal very minor anthropogenic landscape changes on the island of Cyprus compared to those associated with contemporaneous mainland sites. These data also reveal that climatic forces influenced land use decisions on the mainland sites, and provides crucial evidence pertaining to the rise of early anthropogenic landscapes and urbanized civilization.

Contributors

Agent

Created

Date Created
  • 2013