Biogeochemical Modeling of the Response of Forest Watersheds in the Northeastern U.S. to Future Climate Change

In this dissertation I assessed the potential hydrochemical responses of future climate change conditions on forested watersheds in the northeastern U.S. using climate projections from several atmosphere ocean general circulation models (AOGCMs) under different carbon dioxide (CO2) emissions scenarios. The impacts of changing climate on terrestrial ecosystems have been assessed by observational, gradient, laboratory and field studies; however, state-of-the-art biogeochemical models provide an excellent tool to investigate climatic perturbations to these complex ecosystems. The overarching goal of this dissertation was to apply a fully integrated coupled hydrological and biogeochemical model (PnET-BGC) to evaluate the effects of climate change and increasing concentrations of atmospheric CO2 at seven diverse, intensively studied, high-elevation watersheds and to evaluate aspects of these applications. I downscaled coarse scale results to local watersheds and applied these values as input to a biogeochemical model, PnET-BGC. I conducted my research in this dissertation in three phases. In phase one, I used PnET-BGC to evaluate the direct and indirect effects of global change drivers (i.e., temperature, precipitation, solar radiation, CO2) on biogeochemical processes in a northern hardwood forest ecosystem at the Hubbard Brook Experimental Forest (HBEF) New Hampshire, USA. A sensitivity analysis was conducted to better understand how the model responds to variation in climatic drivers, showing that model results are sensitive to temperature, precipitation and photosynthetically active radiation inputs. Model calculations suggested that future changes in climate that induce water stress (decreases in summer soil moisture due to shifts in hydrology and increases in evapotranspiration), uncouple plant-soil linkages allowing for increases in net mineralization/nitrification, elevated leaching losses of NO3- and soil and water acidification. Anticipated forest fertilization associated with increases in CO2 appears to mitigate this perturbation somewhat. In phase two, I compared the use of two different statistical downscaling approaches- Bias Correction-Spatial Disaggregation (BCSD) (Grid-based) and Asynchronous Regional Regression Model (ARRM) (station-based) - on potential hydrochemical projections of future climate at the HBEF. The choice of downscaling approach has important implications for streamflow simulations, which is directly related to the ability of the downscaling approach to mimic observed precipitation patterns. The climate and streamflow change signals indicate that the current flow regime with snowmelt-driven spring-flows in April will likely shift to conditions dominated by larger flows throughout winter. Model results from BCSD downscaling show that warmer future temperatures cause midsummer drought stress which uncouples plant-soil linkages, leading to an increase in net soil nitrogen mineralization and nitrification, and acidification of soil and streamwater. In contrast, the precipitation inputs depicted by ARRM downscaling overcame the risk of drought stress due to greater estimates of precipitation inputs. In phase three of this research, I conducted a cross-site analysis of seven intensive study sites in the northeastern U.S. with diverse characteristics of climate, soil and vegetation type, and historical land disturbances to assess the range of forest-watershed responses to changing climate. Model results show that evapotranspiration increases across all sites under potential future conditions of warmer temperature and longer growing season. Modeling results indicate that spruce-fir forests will likely experience temperature stress and decline in productivity, while some of the northern hardwood forests are likely to experience water stress due to early loss of snowpack, longer growing season and associated water deficit. This latter response is somewhat counter-intuitive as most sites are expected to have increases in precipitation. Following increases in temperature, ET and water stress associated with future climate change scenarios, a shifting pattern in carbon allocation in plants was evident causing significant changes in NPP. The soil humus C pool decreased significantly across all sites and showed strong negative relationship with increases in temperature. Cross-site analysis among different watersheds in the Northeast indicated that dominant type of vegetation, and historical land disturbances coupled with climate variability will influence future responses of watersheds to climate change. The variability in hydrochemical response across sites is due to vegetation type, soil and geological characteristics, and historical land disturbances

The Tao of open science for ecology

The field of ecology is poised to take advantage of emerging technologies that facilitate the gathering, analyzing, and sharing of data, methods, and results. The concept of transparency at all stages of the research process, coupled with free and open access to data, code, and papers, constitutes “open science.” Despite the many benefits of an open approach to science, a number of barriers to entry exist that may prevent researchers from embracing openness in their own work. Here we describe several key shifts in mindset that underpin the transition to more open science. These shifts in mindset include thinking about data stewardship rather than data ownership, embracing transparency throughout the data life‐cycle and project duration, and accepting critique in public. Though foreign and perhaps frightening at first, these changes in thinking stand to benefit the field of ecology by fostering collegiality and broadening access to data and findings. We present an overview of tools and best practices that can enable these shifts in mindset at each stage of the research process, including tools to support data management planning and reproducible analyses, strategies for soliciting constructive feedback throughout the research process, and methods of broadening access to final research products

Interactive Effects of Climate Change with Nutrients, Mercury, and Freshwater Acidification on Key Taxa in the North Atlantic Landscape Conservation Cooperative Region

The North Atlantic Landscape Conservation Cooperative LCC (NA LCC) is a public–private partnership that provides information to support conservation decisions that may be affected by global climate change (GCC) and other threats. The NA LCC region extends from southeast Virginia to the Canadian Maritime Provinces. Within this region, the US National Climate Assessment documented increases in air temperature, total precipitation, frequency of heavy precipitation events, and rising sea level, and predicted more drastic changes. Here, we synthesize literature on the effects of GCC interacting with selected contaminant, nutrient, and environmental processes to adversely affect natural resources within this region. Using a case study approach, we focused on 3 stressors with sufficient NA LCC regionspecific information for an informed discussion. We describe GCC interactions with a contaminant (Hg) and 2 complex environmental phenomena—freshwater acidification and eutrophication. We also prepared taxa case studies on GCCand GCC-contaminant/nutrient/process effects on amphibians and freshwater mussels. Several avian species of high conservation concern have blood Hg concentrations that have been associated with reduced nesting success. Freshwater acidification has adversely affected terrestrial and aquatic ecosystems in the Adirondacks and other areas of the region that are slowly recovering due to decreased emissions of N and sulfur oxides. Eutrophication in many estuaries within the region is projected to increase from greater storm runoff and less denitrification in riparian wetlands. Estuarine hypoxia may be exacerbated by increased stratification. Elevated water temperature favors algal species that produce harmful algal blooms (HABs). In several of the region\u27s estuaries, HABs have been associated with bird die-offs. In the NA LCC region, amphibian populations appear to be declining. Some species may be adversely affected by GCC through higher temperatures and more frequent droughts. GCC may affect freshwater mussel populations via altered stream temperatures and increased sediment loading during heavy storms. Freshwater mussels are sensitive to un-ionized ammonia that more toxic at higher temperatures. We recommend studying the interactive effects of GCC on generation and bioavailability of methylmercury and how GCC-driven shifts in bird species distributions will affect avian exposure to methylmercury. Research is needed on how decreases in acid deposition concurrent with GCC will alter the structure and function of sensitive watersheds and surface waters. Studies are needed to determine how GCC will affect HABs and avian disease, and how more severe and extensive hypoxia will affect fish and shellfish populations. Regarding amphibians, we suggest research on 1) thermal tolerance and moisture requirements of species of concern, 2) effects of multiple stressors (temperature, desiccation, contaminants, nutrients), and 3) approaches to mitigate impacts of increased temperature and seasonal drought. We recommend studies to assess which mussel species and populations are vulnerable and which are resilient to rising stream temperatures, hydrological shifts, and ionic pollutants, all of which are influenced by GCC

Construction and Climate Change; Challenges and Opportunities: A Case Study of the Northeast U.S

Abstract The Northeast megalopolis of the United States, which covers a high-density corridor from Washington, D.C., north to Boston, is one of the most developed environments in the world. It contains a gigantic, complicated, and intertwined network of supporting infrastructure with average score of D+, hence requiring substantial rehabilitation and renewal. The 2020 North American Construction report forecasted a CAGR of 8.4% by 2024 despite the pandemic. The pace of growth will recover from 2021 onwards as the ongoing infrastructure investments and smart city projects will add momentum for the region’s construction industry. On the other hand, climate change impacts are underway across the globe and the Northeast of the U.S. is not an exception. Populations and aging infrastructures that they depend on, are highly vulnerable to climate hazards including heat waves, as well as flooding due to a combination of sea level rise, storm surge, and extreme precipitation events. In this study, future projections of climate change in the Northeast of the U.S. were used to explore their potential impacts on construction industry including but not limited to safety of workforce, selection of building materials and their lifecycle, logistics, scheduling, costs, and insurance. The challenges and opportunities that construction industry faces under climate change were also covered. Later, the feedback loop between the construction and climate change were discussed as well as how sustainable construction practices could mitigate climate change impacts while providing safety for construction workforce. Finally, this paper focuses on resilience, buildings carbon footprint, green infrastructure, sustainability, and a prototype decision-support tool for construction projects to better manage weather risk from contract to project completion, known as Climate-i Construction, and how construction industry can benefit from them under 21st century changing climate.</jats:p

Enhancing Student Learning Experience by Incorporating Virtual Reality into Construction Safety and Risk Management Class

For years, the construction industry was notorious for being slow in adopting new technologies. However, in the past decade, this trend started to change. Technologies such as building information modeling (BIM), drone, autonomous equipment, 3D printing, artificial intelligence (AI), virtual reality (VR), and augmented reality (AR) were developed and used by the industry at a breakneck speed. While VR/AR technologies have been around for quite a long time, they have been gaining more attention by the AEC (Architecture, Engineering, and Construction) industry recently. These technologies have proven to benefit construction projects in many ways. From preconstruction to construction, they can add value and save time and money. One of the great advantages of these technologies is training for jobsite safety and hazard recognition. To create more interactive learning experience and prepare students for a rapidly changing industry, VR technology was utilized in Construction Safety and Risk Management class in the Construction Management program at Wentworth Institute of Technology. This paper describes how VR technology was incorporated as a pilot study into the class curriculum and provided students with a different and more engaging learning experience, as well as how it helped them learn the subject matter better.</jats:p