Life Sciences Commons^™

Climate Interactions Drive Tree Physiology And Growth In A Northeastern Forest Ecotone, Alexandra M. Barry

Electronic Theses and Dissertations

Climate change is a threat to global forest ecosystems. In the northeastern United States, forest trees are facing rising temperatures and increasingly inconsistent moisture regimes. In addition to long-term changes in climate conditions, there is concern about the potential for more frequent and intense climate extremes, which can have severe and rapid negative effects on tree physiology and growth. Further, climate extremes may co-occur to produce a greater magnitude of effect than the sum of their parts, with a prominent example being hot droughts, which are increasing in occurrence and severity. The impact of these and other extreme climate interactions …

A Silvicultural Approach To Increase Drought Resistance And Resilience In Longleaf Pine, Kyle R. Dues

Theses and Dissertations

Droughts are a common disturbance experienced by forest systems across the southeastern United States and are expected to increase in frequency in the near future. Few empirical studies have evaluated the response of individual tree resistance and resilience following silvicultural treatment in longleaf pine (Pinus palustris Mill.). This study evaluates the differences in drought responses between two forests during three different periods. The first period evaluated pretreatment (2000) conditions, while the second (2006), and third (2011) compared conditions after the implementation of five silvicultural treatments. The main findings are that, as additional basal area is removed, both individual tree …

Assessment Of Drought Stress Responsive Genes Expression Profiles And Proline Accumulation In A Diverse Set Of Grapevine Rootstocks, Canan Yüksel Özmen, Funda Yilmaz Baydu, Mohammad Hasanzadeh, Mert Öktem, Günseli̇ Babaoğlu, Umut Ki̇bar, Saber Delpasand Khabbazi, Kemal Kazan, Ali̇ Ergül

Turkish Journal of Agriculture and Forestry

In order to study plant responses to drought stress, it is important to have markers for such responses. This issue has been a challenge for decades and numerous traits have been used for this purpose. In the current study, the influence of drought stress on proline biosynthesis, leaf water potential, and also gene expression levels of 10 genes probably involved in drought stress response regulation pathways were investigated. Also, all experiments were performed in both root and leaf tissues of studied rootstocks to investigate the response of plant tissues which is more suitable for the assessment of possible markers. As …

Determination Of Cadmium And/Or Drought Stress Effects On Some Plant Phytohormone Contents And Hormone Gene Expressions In Bean (Phaseolus Vulgaris L), Melek Eki̇nci̇, Ertan Yildirim, Güleray Ağar, Esra Arslan Yüksel, Murat Aydin, Selda Örs, Razi̇ye Kul

Turkish Journal of Agriculture and Forestry

Plants can sometimes be under the influence of more than one stress factor. In this case, combined stress factors can cause different responses in plants. In this study, the phytohormonal activity and hormone gene expressions of beans (Phaseolus vulgaris L.) were investigated in different drought levels and soils with different levels of cadmium accumulation. Plants were grown at 4 different cadmium (Cd) levels (Cd: 0, Cd1: 100, Cd2: 150, and Cd3: 200 mg kg$^{-1}$) and 3 irrigation levels (D0: 100%, D1: 75%, and D2: 50% of field capacity). Abscisic acid (ABA), indole acetic acid (IAA), gibberellic acid (GA), salicylic acid …

Quantifying And Predicting Drought Performance In Woody Semi-Arid Seedlings In South Texas: Implications For Enhancing Drought Resilience In Restoration, Zarek Contreras

Theses and Dissertations

Increasingly frequent and severe droughts in the Lower Rio Grande Valley National Wildlife Refuge have been observed to cause large variation in species-specific mortality patterns in young seedlings, spanning 6 – 43 % mortality within the first year. To understand the underlying mechanisms behind this, we subjected seedlings of five woody semi-arid species (Celtis pallida, Forestiera angustifolia, Sideroxylon celastrinum, Phaulothalmnus spinescens, and Zanthoxylum fagara) to a point-of-no-return drought experiment in order to (1) identify potential metrics capable of predicting species wilting and mortality responses, and (2) to understand the underlying mechanisms that correspond to species drought performance …

Understory Plant Communities Show Resistance To Drought, Hurricanes, And Experimental Warming In A Wet Tropical Forest, Aura M. Alonso-Rodríguez, Tana E. Wood, Jamarys Torres-Díaz, Molly A. Cavaleri, Sasha C. Reed, Benedicte Bachelot

Michigan Tech Publications

Global climate change has led to rising temperatures and to more frequent and intense climatic events, such as storms and droughts. Changes in climate and disturbance regimes can have non-additive effects on plant communities and result in complicated legacies we have yet to understand. This is especially true for tropical forests, which play a significant role in regulating global climate. We used understory vegetation data from the Tropical Responses to Altered Climate Experiment (TRACE) in Puerto Rico to evaluate how plant communities responded to climate warming and disturbance. The TRACE understory vegetation was exposed to a severe drought (2015), 2 …

Disturbance Reduces Fungal White-Rot Litter Mat Cover In A Wet Subtropical Forest, D. Jean Lodge, Ashley E. Van Beusekom, Grizelle González, Mareli Sánchez-Julia, Sarah Stankavich

USDA Forest Service / UNL Faculty Publications

Fungi that bind leaf litter into mats and produce white-rot via degradation of lignin and other aromatic compounds influence forest nutrient cycling and soil fertility. Extent of white-rot litter mats formed by basidiomycete fungi in Puerto Rico decreased in response to disturbances—a simulated hurricane treatment executed by canopy trimming and debris addition in 2014, a drought in 2015, a treefall, and two hurricanes 10 days apart in September 2017. Percent fungal litter mat cover ranged from 0.4% after Hurricanes Irma and Maria to a high of 53% in forest with undisturbed canopy prior to the 2017 hurricanes, with means mostly …

Drought, Tree Mortality, And Regeneration In Northen California, Sophia Lb Lemmo

Cal Poly Humboldt theses and projects

The 2012-2016 California drought was the most severe in the state’s recorded history, contributing to the death of millions of trees. While the effects of this drought on forests are relatively well studied in the central and southern Sierra Nevada, less is known about its effects on the heavily timbered and diverse forests of northern California. Through sampling 54 0.25 ha plots in northern California, this study compared tree mortality and regeneration patterns before, during, and after California’s most recent record-setting drought. This study evaluated 1) the influence of habitat and competitive covariates on mortality and regeneration trends using ridge …

Poor Acclimation To Experimental Field Drought In Subalpine Forest Tree Seedlings, Alex Goke, Patrick H. Martin

Biological Sciences: Faculty Scholarship

The ability of tree species to acclimate and tolerate projected increases in drought frequency and intensity has fundamental implications for future forest dynamics with climate change. Inquiries to date on the drought tolerance capacities of tree species, however, have focused almost exclusively on mature trees with scant in situ work on seedlings, despite the central role that regeneration dynamics play in forest responses to changing conditions. We subjected naturally established seedlings of co-dominant subalpine conifer species (Abies lasiocarpa and Picea engelmannii) in the southern Rocky Mountains to 2 years of in situ summer precipitation exclusion, simulating summer drought …

Hydraulic Architecture Explains Species Moisture Dependency But Not Mortality Rates Across A Tropical Rainfall Gradient, Alexandria L. Pivovaroff, Brett T. Wolfe, Nate G. Mcdowell, Bradley O. Christoffersen, Stuart J. Davies, L. Turin Dickman, Charlotte Grossiord, Riley T. Leff, Alistair Rogers, Shawn P. Serbin

Biology Faculty Publications and Presentations

Intensified droughts are affecting tropical forests across the globe. However, the underlying mechanisms of tree drought response and mortality are poorly understood. Hydraulic traits and especially hydraulic safety margins (HSMs), that is, the extent to which plants buffer themselves from thresholds of water stress, provide insights into species-specific drought vulnerability. We investigated hydraulic traits during an intense drought triggered by the 2015–2016 El Niño on 27 canopy tree species across three tropical forest sites with differing precipitation. We capitalized on the drought event as a time when plant water status might approach or exceed thresholds of water stress. We investigated …

Splitting The Difference: Heterogeneous Soil Moisture Availability Affects Aboveground And Belowground Reserve And Mass Allocation In Trembling Aspen, Ashley T. Hart, Morgane Merlin, Erin Wiley, Simon M. Landhäusser

Aspen Bibliography

When exploring the impact of resource availability on perennial plants, artificial treatments often apply conditions homogeneously across space and time, even though this rarely reflects conditions in natural systems. To investigate the effects of spatially heterogeneous soil moisture on morphological and physiological responses, trembling aspen (Populus tremuloides) saplings were used in a split-pot experiment. Following the division of the root systems, saplings were established for a full year and then subjected to either heterogeneous (portion of the root system exposed to non-lethal drought) or homogeneous (whole root system exposed to non-lethal drought or well-watered) treatments. Above- and belowground …

Loblolly Pine (Pinus Taeda) Leaf-Level Physiology And The Influence Of Genotype, Drought, And Thinning, Norman Jesse Cone Iv

Master's Theses

The Southeastern U.S. is known as the “Wood Basket” for producing the vast majority of U.S. timber, but projected increases in the frequency of severe drought events could threaten timber plantations. Loblolly pine (Pinus taeda) is the principle timber species of the southeast and is distributed across the Atlantic Coastal Plains and west into Texas. Western Gulf states (LA, TX, AR, and OK) lie at the edge of the range for loblolly pine and are particularly vulnerable to any changes in precipitation or temperature. Current research suggests two main methods to increase plantation drought resistance: plant drought resistant seedlings or …

Assessing And Mapping The Spatial-Temporal Change In Forest Phenology Of Arabuko-Sokoke Forest Using Moderate Resolution Satellite, Bailey Ytterdahl

Independent Study Project (ISP) Collection

This study focuses on coastal forests in Kenya that have some of the highest variety of flora and fauna, specifically Arabuko Sokoke Forest. Arabuko Sokoke Forest is located 110 miles north of Mombasa and 18 kilometers south of Malindi. This forest is known to be a worldwide biodiversity hotspot that is home to endemic and rare plants and animals. Within the Arabuko Sokoke Forest ecosystem, there are two main issues that challenge the conservation of the area. First, there has been more competition for land, primarily for agriculture and development. Second, there is an increase demand for forest resources due …

Effects Of Thinning On Dynamics And Drought Resistance Of Aspen-White Spruce Mixtures: Results From Two Study Sites In Saskatchewan, Philip G. Comeau

Aspen Bibliography

Drought stress associated with warm temperatures is causing increased mortality and reduced growth of trees in drier portions of the boreal forests of western Canada with both warming and drought expected to increase over the coming decades. While thinning is often shown to reduce drought stress, there is little information on its effects in stands comprised of mixtures of trembling aspen and white spruce that are common in the forests of this region. This study examined effects of pre-commercial thinning on aspen and spruce growth, response to drought stress, and stand dynamics for two study sites located in Saskatchewan, Canada. …

Influences On Conifer Drought Responses In Northern California, Wallis L. Robinson

Cal Poly Humboldt theses and projects

California is experiencing increasingly severe and prolonged droughts, which are contributing to changes in tree stress and forest mortality. Many factors affect a tree’s drought response, including competition, climate, and site and tree characteristics. Northern California provides a suitable venue to explore the effects of these factors, as it spans a variety of site conditions and includes habitat for conifers with different adaptations and requirements. This study used annual ¹³C discrimination and growth metrics to assess differences in drought resistance and resilience in conifers adapted to coastal and montane ranges at both wet and dry sites, as well as …

Inoculum Potential Of Pinus Edulis-Associated Ectomycorrhizal Fungi Across A Forest Extirpation Chronosequence, Annie M. Montes

Biology ETDs

Few studies have examined inoculum potential of ectomycorrhizal fungi (EMF) in the absence of plant hosts, yet persistence of these fungi may be paramount to resilience of Pinus edulis and other mycorrhizal plant species. We conducted a study in which seven sites were selected in northwestern New Mexico with known dates of P. edulis extirpation and a lack of regeneration. Age classes included: two sites extirpated 10-20 years ago, two extirpated 55-65 years ago, two extirpated 500+ years ago, and one extirpated 11,000+ years ago. At each site, two plots were paired: an extirpated plot and the nearest live adult …

Drought- Conditioning Of Quaking Aspen (Populus Tremuloides Michx.) Seedlings During Nursery Production Modifies Seedling Anatomy And Physiology, Joshua L. Sloan, Owen T. Burney, Jeremiah R. Pinto

Aspen Bibliography

In the western US, quaking aspen (Populus tremuloides Michx.) regenerates primarily by root suckers after disturbances such as low to moderate severity fires. Planting aspen seedlings grown from seed may provide a mechanism to improve restoration success and genetic diversity on severely disturbed sites. However, few studies have examined the use of container-grown aspen seedlings for restoration purposes from both the outplanting and nursery production perspective. Thus, the purpose of this novel study was to examine how alterations in irrigation levels during nursery production across three seed sources would impact seedling performance attributes on harsh, dry outplanting sites. Irrigation …

Influence Of Forest-To-Silvopasture Conversion And Drought On Components Of Evapotranspiration, Adam P. Coble, Alexandra R. Contosta, Richard G. Smith, Nathan W. Siegert, Matthew A. Vadeboncoeur, Katie A. Jennings, Anthony J. Stewart, Heidi Asbjornsen

Natural Resources & the Environment

The northeastern U.S. is projected to experience more frequent short-term (1-2 month) droughts interspersed among larger precipitation events. Agroforestry practices such as silvopasture may mitigate these impacts of climate change while maintaining economic benefits of both agricultural and forestry practices. This study evaluated the effects of forest-to-silvopasture (i.e., 50% thinning) conversion on the components of evapotranspiration (transpiration, rainfall interception, and soil evaporation) during the growing season of 2016. The study coincided with a late-summer drought throughout the northeastern U.S., which allowed us to also evaluate the effects of forest-to-silvopasture conversion on drought responses of multiple tree species, including Pinus strobus, …

Drought In Temperate Mesic Regions Leads To Micro-Density Anomalies In White Pine, Elise Miller

CSB/SJU Distinguished Thesis

Wood density and wood volume determine the amount of carbon fixed by trees; however, while we are beginning to understand normal seasonal variation in wood density, anomalies are common, and their drivers are poorly understood. In conifers, wood density normally increases continuously throughout the season, but intra-annual fluctuations in wood density can occur and have been linked to climatic events. The causes of these fluctuations in density at the micro-scale (hereafter micro-density anomalies) are still debated.

Mesic regions are experiencing more droughts, but micro-density anomalies are rarely studied in these ecosystems. This study examined micro-density anomaly distribution within the boles …

Subalpine Forest Tree Seedling Response To Drought, Alex Goke

Electronic Theses and Dissertations

Knowledge of tree species’ ability to tolerate drought is necessary to anticipate future forest dynamics with climate change, especially at the seedling stage given their role in shaping forest structure. We used precipitation reduction shelters to mimic drought for subalpine conifer seedlings (A. lasiocarpa and P. engelmannii) in the Rocky Mountains and compared survivorship and morphological and physiological responses to assess relative degrees of drought tolerance. We detected no significant investment in morphological tolerance traits (e.g. root biomass, leaf:stem area ratio) but substantial reductions in net photosynthesis. While shading partially ameliorated drought effects when precipitation reduction was moderate, …

Leaf Angle And Leaf Stomata Responses To Experimental Drought In Quercus Velutina And Acer Saccharum, Brittany Nichole Casey

Graduate Theses, Dissertations, and Problem Reports

The possibility of increased severity and frequency of drought conditions, as a result of global climate variability, greatly complicates our ability to forecast future forest functions such as productivity and carbon sequestration. Assessing how tree species vary in their response to drought can aid in predicting the impact on forest ecosystems as a whole. Throughfall exclusion (TfE) experiments are potentially useful tools to simulate realistic drought conditions within intact forest ecosystems. We employed a TfE experiment during the 2018 growing season within the WV Land Trust’s Elizabeth’s Woods Nature Preserve, near Morgantown, WV, to assess the leaf angle and leaf …

Spatial Upscaling Of Forest Response To Drought, Wei Fang, Peipei Xu, Tao Zhao, Xiang Zhao, Hui Luo, George Hendrey, Chuixiang Yi

Publications and Research

We have integrated the observational capability of satellite remote sensing with plot-scale tree ring data to up-scale the evaluation of forest responses to drought. Satellite data, such as Normalized Difference Vegetation Index (NDVI), can provide a spatially continuous measure with limited temporal coverage, while tree Ring Width Index (RWI) provides accurate assessment with much longer time series local scales. Here, we explored the relationship between RWI and NDVI of three dominant species in the Southwestern United States (SWUS), and predicted RWI spatial distribution from 2001 to 2017 based on MODIS 1-km resolution NDVI data with stringent quality control. We detected …

Sudden Aspen Decline: A Review Of Pattern And Process In A Changing Climate, Jack A. Singer, Rob Turnbull, Mark Foster, Charles Bettigole, Brent R. Frey, Michelle C. Downey, Kristofer R. Covey, Mark S. Ashton

Aspen Bibliography

The American quaking aspen (Populus tremuloides Michx.) and its close relative, the Eurasian quaking aspen (Populus tremula L.), cover a realm that is perhaps the most expansive of all tree species in the world. In North America, sudden aspen decline (SAD) is a growing concern that marks the rapid decline of quaking aspen trees leading to mortality at the stand and landscape scale. Research suggests that drought and water stress are the primary causes of SAD. Predisposing factors (age, structure, and landscape position), as well as associated stressors (i.e., pests and pathogens), have been linked to mortality in affected stands. …

Will Seasonally Dry Tropical Forests Be Sensitive Or Resistant To Future Changes In Rainfall Regimes?, Kara Allen, Juan Manuel Dupuy, Maria G. Gei, Catherine Hulshof, David Medvigy, Camila Pizano, Christina M. Smith, Annette Trierweiler, Skip J. Van Bloem, Bonnie G. Waring, Xiangtao Xu, Jennifer S. Powers

Skip Van Bloem

Seasonally dry tropical forests (SDTF) are located in regions with alternating wet and dry seasons, with dry seasons that last several months or more. By the end of the 21st century, climate models predict substantial changes in rainfall regimes across these regions, but little is known about how individuals, species, and communities in SDTF will cope with the hotter, drier conditions predicted by climate models. In this review, we explore different rainfall scenarios that may result in ecological drought in SDTF through the lens of two alternative hypotheses: 1) these forests will be sensitive to drought because they are already …

Competition, Climate, And Drought Effects On Tree Growth In An Encroached Oak Woodland In Northern California, Jill J. Beckmann

Cal Poly Humboldt theses and projects

Oregon white oak (Quercus garryana Douglas ex Hook.) is experiencing increasing competition from Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) across its range at the same time as climate models are predicting increasing climate variability, including drought. Management recommendations that consider competition dynamics between these species under a changing climate are therefore needed for oak woodlands, but we do not currently understand the combined effects of competition, climate, and drought in this ecosystem. This research examines radial tree growth and drought response in Oregon white oak and Douglas fir in an encroached oak woodland near Kneeland, California. Stem maps …

Increased Soil Temperature Stimulates Changes In Carbon, Nitrogen, And Mass Loss In The Fine Roots Of Pinus Koraiensis Under Experimental Warming And Drought, Seung Hyun Han, Seongjun Kim, Hanna Chang, Guanlin Li, Yowhan Son

Turkish Journal of Agriculture and Forestry

The effects of warming (+3 °C) and drought (-30% precipitation) on the fine root decomposition of Pinus koraiensis seedlings were examined using a litter bag method. The study site included a full factorial design with two temperature and two precipitation levels, with three replicates. Litter bags containing fine root litter of 2-year-old P. koraiensis seedlings were retrieved after 3, 6, and 12 months of decomposition. After 12 months, the mass loss of fine roots was significantly increased in response to warming (control = 31.1%, warming = 35.9%, drought = 29.2%, and warming plus drought = 35.5%); no change was observed …

Tamm Review: Reforestation For Resilience In Dry Western U.S. Forests, Malcolm P. North, Jens T. Stevens, David F. Greene, Michelle Coppoletta, Eric E. Knapp, Andrew M. Latimer, Christina M. Restaino, Ryan E. Tompkins, Kevin R. Welch, Rob A. York, Derek J.N. Young, Jodi N. Axelson, Tom N. Buckley, Becky L. Estes, Rachel N. Hager, Jonathan W. Long, Marc D. Meyer, Steven M. Ostoja, Hugh D. Safford, Kristen L. Shive, Carmen L. Tubbesing, Dana Walsh, Chhaya M. Werner, Peter Wyrsch, Heather Vice

USDA Forest Service / UNL Faculty Publications

The increasing frequency and severity of fire and drought events have negatively impacted the capacity and success of reforestation efforts in many dry, western U.S. forests. Challenges to reforestation include the cost and safety concerns of replanting large areas of standing dead trees, and high seedling and sapling mortality rates due to water stress, competing vegetation, and repeat fires that burn young plantations. Standard reforestation practices have emphasized establishing dense conifer cover with gridded planting, sometimes called 'pines in lines', followed by shrub control and pre-commercial thinning. Resources for such intensive management are increasingly limited, reducing the capacity for young …

Will Seasonally Dry Tropical Forests Be Sensitive Or Resistant To Future Changes In Rainfall Regimes?, Kara Allen, Juan Manuel Dupuy, Maria G. Gei, Catherine Hulshof, David Medvigy, Camila Pizano, Christina M. Smith, Annette Trierweiler, Skip J. Van Bloem, Bonnie G. Waring, Xiangtao Xu, Jennifer S. Powers

Publications

Seasonally dry tropical forests (SDTF) are located in regions with alternating wet and dry seasons, with dry seasons that last several months or more. By the end of the 21st century, climate models predict substantial changes in rainfall regimes across these regions, but little is known about how individuals, species, and communities in SDTF will cope with the hotter, drier conditions predicted by climate models. In this review, we explore different rainfall scenarios that may result in ecological drought in SDTF through the lens of two alternative hypotheses: 1) these forests will be sensitive to drought because they are already …

In The Face Of Drought: Do Fuel Treatments Promote Resistance To Multi-Year Drought In A Mixed-Conifer Forest Of Northern California?, Michael Vernon

Cal Poly Humboldt theses and projects

Climate change is predicted to increase the frequency, duration, and severity of drought events across many bioregions. Forest managers have two active management techniques to promote resistance and resilience to drought: prescribed fire and mechanical thinning. Generally applied to reduce fuels and fire hazard, treated areas may also reduce competition for resources that may improve tree-growth during drought and reduce mortality. The recent severe and prolonged drought in California allowed me to investigate the effects of climate stress and fuel treatments on tree growth responses in a dry mixed-conifer forest ecosystem.

To assess tree-growth responses to fuel treatments during severe …

Agricultural Trade Publications And The 2012 Midwestern U.S. Drought: A Missed Opportunity For Climate Risk Communication, Sarah P. Church, Tonya Haigh, Melissa Widhalm, Silvestre Garcia De Jalon, Nicholas Babin, Stuart Carlton, Michael Dunn, Katie Fagan, Cody L. Knutson, Linda Stalker Prokopy

Department of Forestry & Natural Resources Faculty Publications

The Midwestern United States experienced a devastating drought in 2012, leading to reduced corn and soybean yields and increased instances of pests and disease. Climate change induced weather variability and extremes are expected to increase in the future, and have and will continue to impact the agricultural sector. This study investigated how agricultural trade publications portrayed the 2012 U.S. Midwestern drought, whether climate change was associated with drought, and whether these publications laid out transformative adaptation measures farmers could undertake in order to increase their adaptive capacity for future climate uncertainty. We performed a content analysis of 1000 media reports …