Life Sciences Commons^™

Future Forest Composition Under A Changing Climate And Adaptive Forest Management In Southeastern Vermont, Usa, Matthias Taylor Nevins

Graduate College Dissertations and Theses

Global environmental change represents one of the greatest challenges facing forest resource managers today. The uncertainty and variability of potential future impacts related to shifting climatic and disturbance regimes on forest systems has led resource managers to seek out alternative management approaches to sustain the long-term delivery of forest ecosystem services. To this end, forest managers have begun incorporating adaptation strategies into resource planning and are increasingly utilizing the outcomes of forest landscape simulation and climate envelope models to guide decisions regarding potential strategies to employ. These tools can be used alongside traditional methods to assist managers in understanding the …

Growth Dynamics Of Black Spruce (Picea Mariana) Across Northwestern North America, Anastasia E. Sniderhan

Theses and Dissertations (Comprehensive)

The impacts of climate change have been widely documented around the world. One of the most rapidly changing areas is the boreal forest of North America. The extent of change has been such that there have been shifts in long-standing climate-growth relationships in many boreal tree species; while the growth of many of these high-latitude forests were formerly limited by temperature, warming has increased the evapotranspirative demands such that there is widespread drought stress limiting productivity in the boreal forest. With the importance of the boreal forest as a global carbon sink, it is imperative to understand the extent of …

Drivers Of Post-Fire Vascular Plant Regeneration In The Conifer-Dominated Boreal Forest Of Southern Northwest Territories, Alison White

Theses and Dissertations (Comprehensive)

In recent years, climate warming has led to an increase in the severity and frequency of naturally occurring fires in boreal ecosystems globally. In 2014, an unprecedented 3.4 million hectares of boreal forest burned in the Northwest Territories (NWT). While much research has focused on post-fire succession of serotinous tree species such as Picea mariana (black spruce) and Pinus banksiana (jack pine), the understory community of vascular plants play an important role in ecosystem functioning but less is known about the response of this component of the system to changing fire regimes. Regeneration strategies such as the ability to resprout …

Remote Sensing Methods And Applications For Detecting Change In Forest Ecosystems, David James Gudex-Cross

Graduate College Dissertations and Theses

Forest ecosystems are being altered by climate change, invasive species, and additional stressors. Our ability to detect these changes and quantify their impacts relies on detailed data across spatial and temporal scales. This dissertation expands the ecological utility of long-term satellite imagery by developing high quality forest mapping products and examining spatiotemporal changes in tree species abundance and phenology across the northeastern United States (US; the ‘Northeast’).

Species/genus-level forest composition maps were developed by integrating field data and Landsat images to model abundance at a sub-pixel scale. These abundance maps were then used to 1) produce a more detailed, accurate …

Estimating The Range Shift And Harvesting Intensity Of Junipers In Bhutan (Eastern Himalaya), Rinchen Namgay

Theses

The authors of more than 97% of the scientific publications on climate change agree that global temperature has increased in the last six decades and is caused by human beings via emission of greenhouse gases in the atmosphere. This phenomenon has altered natural ecosystem functions, causing many species to shift to a more suitable habitat. Throughout the world, because of recent climate warming, many forms of range shift associated with climate warming has occurred. While animals can move as warming happens, plants being stationary organisms cannot move, so the difference in the distribution of different plant life stages is an …

Elevated Temperature And Co2 Concentrations Affect Carbon Flux In Two Boreal Conifers, Sasha Madhavji

Electronic Thesis and Dissertation Repository

Elevated temperatures and CO₂ will alter carbon flux in two dominant boreal tree species Picea mariana (black spruce) and Larix laricina (tamarack). Trees were grown in three temperature treatments (ambient, ambient +4 °C, and ambient +8 °C) at either 400 ppm or 750 ppm CO₂, to simulate climate conditions between now and the year 2100. Spruce acclimated to increasing temperature detractively; warming scenarios reduced spruce net carbon gain. Tamarack maintained comparable levels of net photosynthesis (A_net) across warming treatments and both species acclimated respiration (R_dark) with increasing growth temperature. Elevated CO₂-grown …

Effects Of In-Situ Leaf-Level Canopy Warming In A Northern Hardwood Forest, Kelsey Carter

Dissertations, Master's Theses and Master's Reports

Rising mean annual temperatures due to climate change have intensified the need to understand the effects of warming on plant physiological processes. Forest photosynthesis is the most important pathways of terrestrial carbon sequestration, yet continued warming could reduce this important carbon sink. Photosynthesis is highly sensitive to temperature and begins to decline after an optimum temperature (T_opt) is reached, leading to reduced carbon uptake. To date, logistical difficulties have limited our ability to test photosynthetic responses to sustained warming in mature forest canopies. In order to understand how elevated temperatures will affect forest ecosystems, we need to be …

Exploring Historical Coffee And Climate Relations In Southern Guatemala: An Integration Of Tree Ring Analysis And Remote Sensing Data, Diego Pons

Electronic Theses and Dissertations

This dissertation makes use of a physical geography perspective to examine the relationship between agriculture and climate in Guatemala using dendrochronology. I examined the potential of high-resolution climate proxy data from dendrochronology to help fill in the gaps of past climate information to better understand the natural and anthropogenic variability of precipitation which, in turn, can inform Guatemala’s agriculture sector. This research has demonstrated successful cross-dating and climate sensitivity of Abies guatemalensis in the Pacific slope of Guatemala. Based on this, I have produced a 124-year record of mean precipitation from June-July-August. The mean precipitation from June-July-August at this site …

Quantifying Tree Response To Alterations In Pollution Deposition And Climate Change In The Northeastern Us, Alexandra M. Kosiba

Graduate College Dissertations and Theses

Understanding tree physiological responses to climate change is critical for quantifying forest carbon, predicting species' range change, and forecasting growth trajectories. Continued increases in temperature could push trees into conditions to which they are ill adapted -- such as decreased depth of winter snow cover, altered water regimes, and a lengthened effective growing season. A complicating factor is that in the northeastern United States, climate change is occurring on a backdrop of acid deposition and land-use change. In this dissertation, I used three studies to investigate the spatiotemporal nuances of resultant tree and sapling physiology to environmental change.

First, I …

A Systems Approach To Modelling The Effects Of Climate Change On Agroforestry: A Case Study In Western Tanzania, Elaine M. Samuel

Electronic Thesis and Dissertation Repository

Climate change is anticipated to have significant effects on agricultural production in sub-Saharan Africa as the magnitude of weather events increase in severity. Smallholder farmers in western Tanzania are potentially vulnerable to climate change impact as crops rely on precipitation as the only source of water. It is prudent to evaluate different modes of agricultural adaptations, such as agroforestry, that these farmers can easily adopt to improve their resiliency to the effects of climate change. System dynamics modelling is a cost-effective tool to simulate the long-term behaviour of agroforestry systems under future climate conditions. Water, Nutrient, and Light Capture in …

Instantaneous Photosynthetic Response To Temperature Of Mature Forest Canopies And Experimentally Warmed Seedlings, Alida C. Mau

Dissertations, Master's Theses and Master's Reports - Open

Tropical trees have been shown to be more susceptible to warming compared to temperate species, and have shown growth and photosynthetic declines at elevated temperatures as little as 3oC above ambient. However, regional and global vegetation models lack the data needed to accurately represent physiological response to increased temperatures in tropical forests. We compared the instantaneous photosynthetic responses to elevated temperatures of four mature tropical rainforest tree species in Puerto Rico and the temperate broadleaf species sugar maple (Acer saccharum) in Michigan. Contrary to expectations, leaves in the upper canopy of both temperate and tropical forests had temperature …

Carbon Life-Cycle And Economic Analysis Of Forest Carbon Sequestration And Woody Bioenergy Production, Prativa Shrestha

Theses and Dissertations--Forestry and Natural Resources

Sequestering carbon in standing biomass, using woody bioenergy, and using woody products are the three potential ways to utilize forests in reducing greenhouse gases (GHGs) and mitigating climate change. These forestry related strategies are, however, greatly influenced by the existing markets and market based policies. This study focuses on the first two forest strategies. It investigates the combined impact of carbon and woody bioenergy markets on two different types of forests in the US – oak dominated mixed hardwood forests in the Central Hardwood Forests Region and loblolly pine forests in the southeastern US. A modification of the Harman model …

Tree Growth Dynamics, Fire History, And Fire-Climate Relationships In Pine Rocklands Of The Florida Keys, U.S.A., Grant Logan Harley

Doctoral Dissertations

Pine rocklands are globally endangered, fire-maintained communities currently restricted to small habitat areas in southern Florida, Cuba, and the Bahamas. The purpose of this dissertation research was to identify the long-term ecological disturbance regimes and climatic trends responsible for the persistence of pine rocklands, and examine how human-induced changes during the 20^th century contributed to decline of these communities. This research applied techniques of dendrochronology in extreme southern Florida, in a subtropical region where tree‐ring science has never been applied, to increase the understanding of how anthropogenic and natural disturbance events have decreased the spatial distribution of South Florida …

Warming Alters Photosynthetic Rates Of Sub-Boreal Peatland Vegetation, Arvo Aljaste

Dissertations, Master's Theses and Master's Reports - Open

Boreal peatlands are important in the global carbon cycle. Despite covering only 3% of the global land area, peatlands store approximately one third of all soil carbon. Temperature is one of the major drivers in peatland carbon cycling as it affects both plant production and CO₂ fluxes from soils. However, it is relatively unknown how boreal peatland plant photosynthesis is affected by higher temperatures. Therefore, we measured plant photosynthetic rates under two different warming treatments in a poor fen in Northern Michigan. Eighteen plots were established that were divided into three treatments: control, open-top chamber (OTC) warming and infrared …