Browsing by Subject "growth"

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Adaptation to changing environment in Scots pine populations across a latitudinal gradient
(1998) Oleksyn, Jacek; Tjoelker, Mark G; Reich, Peter B
In several growth chamber and field experiments we examined the growth response of Scots pine (Pinus sylvestris L.) populations from a wide latitudinal range to temperature and photoperiod. The duration of the shoot elongation period of one-year-old seedlings was affected by temperature and photoperiod. In contrasting temperatures, 23/20 °C, 20/17 °C, and 17/14 °C (day/night), shoot elongation period for all populations was shortest in the high and longest in the low temperature treatments. The northern populations from 61–57°N ceased height growth earlier than the other populations in the southern 50°N photoperiod. The order of growth cessation among populations at 50°N in the chamber experiment and at 52°N in the field experiment was similar and related to observed population differences in terminal leader growth and total tree height. Since the length of growing season is under strong environmentally-mediated genetic control in Scots pine, potential climatic changes such as increasing temperature will probably alter the length and timing of growth in aboveground tree parts, but likely in the opposite direction (a shorter growing season) than has been often hypothesized (a longer growing season). Tree-ring analyses of a provenance experiment established in 1912 indicate that the main climatic factors that limited ring-width growth in Scots pine were air temperatures in the winter months of December through March. Low winter temperatures were followed by the formation of narrow rings over the next summer. Based on responses to temperature, Scots pine populations from the continuous European range can be divided in several geographic groups along a latitudinal gradient. Our results suggest that in developing new models to predict the response of Scots pine to changing environmental conditions, it is necessary to include intraspecific differentiation in acclimation and adaptation to environmental factors.
Climate and competition affect growth and survival of transplanted sugar maple seedlings along a 1700‐km gradient
(Wiley, 2017) Putnam, Rachel C
Plant species distributions, broadly shaped by climate, may also be constrained by other species. The degree to which biotic factors affect range limits is unclear, however, and few experimental studies have investigated both biotic and abiotic factors across and beyond a species’ range. We examined seedling survival and net growth for three years in contrasting canopy type (closed canopy vs. gap) and neighbor density (clipped vs. unclipped) environments for northern, central, and southern populations of sugar maple (Acer saccharum) representing a climate- of- origin gradient, experimentally planted from Arkansas, USA to Ontario, Canada at ten forested sites along a 1700- km transect spanning beyond the species’ range. We hypoth-esized that each population’s highest survival and growth would occur in its region of origin, with poorer performance in cooler or warmer areas. Refuting this hypothesis, seedlings of all three populations had greater growth and survival in sites increasingly warmer than their point of origin, although they did show poorer growth and survival at increasingly colder sites. We also hypothesized that maple survival and net growth near and beyond range margins are con-strained primarily by cold temperature limitation in the north, where we expected neighbors to facilitate survival, and by competition in the south, where we expected to enhance survival and growth by reducing neighbor density. Results partially supported the hypothesis concerning biotic interactions: in canopy gaps, understory neighbors enhanced maple growth at the cool-est sites but did not suppress growth as expected at the warmest sites. As the northern popula-tion grew and survived reasonably well beyond the northern range limit, and as all populations performed best at warmer sites, including beyond the southern range limit, there was tepid, if any, support for the hypothesis that climate regulated the northern limit and absolutely no support for the hypothesis that competition regulated the southern limit. Together, these three- year ﬁndings with juvenile trees suggest that sugar maple range limits may instead be con-strained by factors besides climate and competition, by those factors at another life stage, and/or by climate events such as heat waves, droughts, and cold snaps that occur at longer return intervals.
Climate change‐associated trends in net biomass change are age dependent in western boreal forests of Canada
(Wiley, 2016) Chen, Han Y H; Luo, Yong; Reich, Peter B; Searle, Eric B; Biswas, Shekhar R
The impacts of climate change on forest net biomass change are poorly understood but critical for predicting forest's contribution to the global carbon cycle. Recent studies show climate change-associated net biomass declines in mature forest plots. The representativeness of these plots for regional forests, however, remains uncertain because we lack an assessment of whether climate change impacts differ with forest age. Using data from plots of varying ages from 17 to 210 years, monitored from 1958 to 2011 in western Canada, we found that climate change has little effect on net biomass change in forests ≤ 40 years of age due to increased growth offsetting increased mortality, but has led to large decreases in older forests due to increased mortality accompanying little growth gain. Our analysis highlights the need to incorporate forest age profiles in examining past and projecting future forest responses to climate change.
Costs and Benefits of Extended Leaf Phenology in Invasive Shrubs
(2019-01) O'Connell, Erin
Many woody invasive plants in North America develop leaves earlier and retain leaves later than their native associates, which could result in greater carbon gain. However, freezing temperatures and low light levels at northern latitudes constrain growing season length, potentially reducing the importance of spring and fall carbon gain. To investigate the costs and benefits of extended leaf phenology, I observed two years of leaf phenology and for one year estimated total carbon gain, measured growth, and tested the freezing tolerance of four native and four invasive woody shrubs growing in Duluth, MN. I conducted my study in a disturbed forest with greater canopy openness than commonly studied late successional forests, in order to explore these traits in a habitat typical of invasive species. The invaders leafed out simultaneously with native species in the spring and demonstrated an equally high freezing tolerance, but retained their leaves later in the autumn. In addition, invasive species assimilated less carbon during the summer than the native species. Therefore, extended fall phenology in invaders was critical to maintaining competitive levels of carbon gain and did not provide an advantage over native species. These findings suggest that invasive species may be able to take advantage of lengthening growing seasons and that freezing temperatures do not currently limit their northern expansion. Continued research should consider geography and latitude when studying woody invasive species phenology and physiology.
Data supporting "Adverse impacts of hypoxia on aquatic invertebrates: A meta-analysis"
(2018-10-29) Galic, Nika; Hawkins, Tanner; Forbes, Valery E.; nika.galic001@gmail.com; Galic, Nika; Department of Ecology, Evolution, and Behavior
The data set on responses of aquatic invertebrates to hypoxia was created by extracting and digitizing data from published studies. The raw data were scaled to controls (i.e., high levels of oxygen).
Data Supporting Reich et al 2022: Even modest climate change may lead to major transitions in boreal forests
(2022-06-27) Reich, Peter, B.; Bermudez, Raimundo; Montgomery, Rebecca, A.; Rich, Roy, L.; Rice, Karen, E.; Hobbie, Sarah, E.; Stefanski, Artur; preich@umn.edu; Reich, Peter, B.
To test the uncertainty of the sensitivity of forests to near–term warming and associated precipitation we used a five–year open–air experiment in southern boreal forest located at two research sites in northern Minnesota. The experiment used juveniles of nine temperate and boreal tree species that grew under ambient and seasonally warmed (+1.6C and +3.1C above- and belowground) and rainfall reduced (~30% less rainfall) conditions. Each year we surveyed all trees for their survival and growth and measured in situ light-saturated net photosynthesis (Anet) and leaf diffusive conductance (gs).
Dietary Niche and Growth Rate of the Nonnative Tubenose Goby (Proterorhinus semilunaris)
(2019-05) Dawson , Bradley
Basic life history knowledge is essential to determine if a nonnative species is potentially invasive. The nonnative tubenose goby (Proterorhinus semilunaris) arrived in the Great Lakes in the 1990s via ship ballast water, but remains poorly studied within North America, making it difficult to predict its effects on native ecosystems. Diet and growth patterns were examined from age-0 tubenose gobies within the estuary of the St. Louis River, a tributary to Lake Superior near Duluth, Minnesota. Dietary breadth and growth rates have important ramifications for survival, competitiveness, and dispersal ability of a fish species, influencing its potential success as an invasive species. I sampled tubenose gobies from shallow vegetated habitat via beach seine during summer and fall periods, and removed otoliths and aged fish on daily increments for growth modelling. Furthermore, stomach contents were identified and weighed to provide measures of fitness and dietary breadth between seasons (fall vs. summer) and between several locations within the estuary. Results suggest a low dietary breadth that overlaps with tadpole madtom (Noturus gyrinus); tubenose goby diet was mostly comprised of Crustacea, regardless of location or season. Growth modelling demonstrates that tubenose gobies reach a small maximum size and are short-lived, indicating an r-selected life history. The Gompertz function is preferred for modelling the growth of this species.
Essays on the effects of intellectual property rights on economic growth and production fragmentation, and the effects of unions on workplace safety
(2016-07) Yang, Jooyoung
The first essay entitled "What are the Effects of Intellectual Property Rights on Economic Growth? Empirical Analysis of East Asia, TRIPs and Development" estimates the effects of IPRs on economic growth in country level in four ways. First, I consider the growth effects of IPRs across all countries. Second, I consider whether the growth effects of IPRs are different for East Asia than for the rest of the world. Third, I consider whether the 1995 Agreement on Trade-Related Aspects of Intellectual Property Rights (TRIPs) altered the growth effects of IPRs. Fourth, I assess whether there is a tipping point in the relationship between IPRs and growth that is related to the development level of countries. I find that there is a (net) positive relationship between IPRs and economic growth across the countries of the world while the effect is ambiguous in East Asia. Also, the findings show evidence that growth in the post-TRIPs period deviates from that of the entire period in a positive way; yet these positive effects are more modest for East Asia. Finally I find there is a break point that alters the effects of IPRs before and after the TRIPs. The second essay, "Effects of Strengthening Intellectual Property Rights on Global Value Chain", studies the effects of IPRs on exports especially, exports embodying exchange of intermediate inputs. First I consider how stronger IPRs affect exports in sectoral level in generalized factor-proportions framework. To consider an exchange of intermediate inputs, I construct a measure of value added contents of exports and gross exports using global input-output data from World Input-Output Database (WIOD). Second, I investigate how IPRs affect production fragmentation estimated as VAX ratio which represents production fragmentation. I employ the empirical approach in which exports at the industry level are explained as a function of country factor endowment and interactions with industry factor intensities. The evidence shows that a high level of patent protection is associated with high value added exports and gross exports in patent-intensive industries. Second, I find that higher patent protection leads less international fragmentation in patent-intensive industries. In the third essay entitled "Effects of Unionization on Workplace-Safety Enforcement: Regression-Discontinuity Evidence", I study how union certification affects the enforcement of workplace-safety laws. To generate credible causal estimates of certification effects, I employ regression discontinuity. I compare changes in outcomes in establishments where unions barely won representation elections to changes in outcomes in establishments where union barely lost such elections. The study combines two main datasets: the census of National Labor Relations Board (NLRB) representation elections and the Occupational Safety and Health Administrationâ s (OSHA) enforcement database since 1985. From the results, I find evidence of positive effects of union certification on establishmentâ s rate of OSHA inspection, the share of inspections carried out in the presence of a labor representative, violations cited, and penalties assessed.
Growth and Predatory Demand of Cisco (Coregonus artedi) in Western Lake Superior
(2017-01) Harding, Ian
Lake Superior’s food web has been altered in recent decades by changes in fish populations as well as species invasions. In addition, warming surface waters may also effect food web interactions. Cisco (Coregonus artedi) is an abundant and important planktivorous fish in Lake Superior. Cisco link secondary production to top level predators and support a viable commercial fishery. However, it is unknown how these changes to the Lake Superior ecosystem have effected cisco growth rates and resource use in Lake Superior. I reconstructed growth histories of cisco from western Lake Superior from 1984-2013 and used bioenergetics modeling to explore how cisco have responded to changes in their density, the invasion of spiny water flea (Bythotrephes longimanus), and climate change. I also used bioenergetics modeling and concurrent estimates of calanoid copepod standing stock and production to estimate the current supply-demand relationship for this important prey resource of cisco in Lake Superior. Cisco growth rates have been relatively stable over the 25-year period analyzed in this study with the exception of the 1998 cohort. The 1998 cohort had reduced growth rates in comparison to other cohorts analyzed in this study which may be the result of a density dependent reduction in prey resources. Climate change and invasion by spiny water flea may not have effected cisco growth rates to date, however, bioenergetics modeling suggests spiny water flea are a poor prey item for cisco relative to native prey and could reduce growth rates of cisco that consume them. Cisco were the primary consumers of calanoid copepods in the offshore waters of Lake Superior in 2014-2015 and consumption of calanoid copepods by fish was approximately 15% of calanoid production from May 2015-October 2015. Cisco may have exerted top-down control on calanoid copepods from October 2014-May 2015 which could have increased intraspecific competition for prey resources during this time. This work helps to clarify how cisco have responded to perturbations to the Lake Superior food web. In addition, this work suggests cisco in western Lake Superior are not currently prey limited during the growing season (May-October). They may however, exert top-down control on their winter prey resource. Future studies concerning the winter ecology of cisco and calanoid copepods may improve our understanding of resource use by this important planktivore in Lake Superior.
Identification and characterization of EMS mutant trm5a-1 and its interactions with SPY
(2020-01) Grandt, Kristin
SPINDLY (SPY) is an O-fucosyltransferase involved in several processes in Arabidopsis thaliana, including gibberellin signaling, cytokinin signaling, and plant development. spy plants display a number of easily scored phenotypes such as increased stem elongation, decreased leaf serration, and early flowering. Despite its apparent importance, SPY’s function has not been fully characterized, as very few SPY substrates have been identified. In order to address this gap in knowledge, a suppressor screen was conducted to identify potential SPY interactors. An M2 population of ethyl methanesulfonate mutagenized spy-4 plants was screened for suppression of spy phenotypes. Three alleles that showed suppression of spy early flowering and spindly floral shoot phenotypes were identified. The strongest of those alleles was selected for analysis. However, spy-4 is partially male sterile, so the suppressor allele was crossed into spy-3 to facilitate genotypic and phenotypic analysis. Bulk segregant analysis using next generation sequencing was employed to identify the mutation responsible for the partial spy suppression observed. This analysis identified a point mutation that introduces a premature stop codon into the coding region of the TRM5a gene as the most likely candidate. This EMS allele is called trm5a-1 here-in. Analysis of another trm5a allele (T-DNA insertion line trm5a-2) and transgene rescue experiments confirmed that this mutation was responsible for suppressing spy. trm5a-1 and trm5a-2 mutants grow slowly and flower late, phenotypes that have been previously reported in other trm5a alleles. The trm5a-1/spy-3 double mutant phenotypes for these traits suggest a complex interaction between the two genes. Other phenotypes which have not been previously characterized in trm5a mutants are also observed. Exogenous application of cytokinin results in outgrowths at the valve margin in trm5a-1, trm5a-2, spy-3, and trm5a-1/spy-3, but not, at the concentrations used, in Col-0. In all trm5a-1, trm5a-2, and spy-3 single mutants, the outgrowths are small hair- or fan-like protrusions . However, in trm5a-1/spy-3, the outgrowths are larger and may even appear to have stigmatic papillae on their surface. There is also a phenotype of floral clustering in trm5a mutants, which is occasionally observed in some spy mutants but not spy-3. In trm5a-1 and trm5a-2 mutants, the phenotype manifests mainly as flower doublets with occasional small clusters of 4-5 flowers, while in trm5a-1/spy-3 the clusters are larger often comprised of ten or more flowers. The trend of trm5a-1/spy-3 plants to display more severe valve margin outgrowth and clustering phenotypes than the single mutants suggests additive or synergistic interactions between TRM5a and SPY. Broadly, the phenotypes of the trm5a-1, trm5a-2, and spy-3 demonstrate the importance of the genes in proper plant growth and development, and the phenotypes observed in the trm5a-1/spy-3 double mutant suggest a degree of genetic interaction between the two genes and areas of interest for future research into both.
Is my child too short? Answering your questions about your child’s height
(2009-09-16) Donahue, Rebecca
Children who are much shorter than others of the same gender and age, whose growth has slowed down, or those who are not on track to match the height of others in their family should see a specialist for evaluation of a growth disorder.
Mutually Humble Collaboration in College Literacy Courses: Same Papers, Dialogical Responses
(2017-05) Bouchard, Don
Abstract Each fall, first-year college students enter required composition courses with the expectation that they will learn the necessary skills to write competently for their collegiate careers. Quickly, students who survive and thrive discover that complex factors such as experience, academic cultural etiquette, self-regulation, and relationships with professors and classmates combine to set them on paths of success or failure. I examined the literacy induction experiences of college composition students at a private Christian college in the Midwestern United States through a constant comparative analysis framework utilized in a grounded theory research (Strauss & Corbin, 1998, 2008; and Charmaz, 2007.) Through surveys, interviews, and observations in three composition classrooms, I used social cognitive and sociocultural frameworks to focus on participants’ and their professors’ actions and perceptions. Using data from the interviews and observations in a positive deviance selection process (Pascale, Sternin & Sternin, 2010), I narrowed my focus to four participants whose narratives revealed grit (Duckworth, 2016), growth mindset (Dweck, 2015), and evidence of mutually humble collaboration (MHC), the theory that emerged from this study, which serves as the super framework over the themes I examine. My findings indicate that professors and students facing literacy challenges who engage in mutually humble collaboration establish dialogical relationships (Freire, 2009) that foster passion and perseverance leading to success. In this study I address the pragmatic question of how sociocultural concepts such as scaffolding (Vygotsky, 1978), and the dialogical relationship ending the oppressor - oppressed cycle described by Freire (2009) may be initiated. Keywords: mutually humble collaboration, grit, literacy
Plant phenology, growth, freezing damage, and carbon gain data observed from 2017 to 2018 on wood plants growing at Bagley Nature Area in Duluth, MN
(2020-05-26) O'Connell, Erin M; Savage, Jessica A; oconn877@d.umn.edu; O'Connell, Erin M; Savage research team
These data were collected for a project comparing the leaf phenology, carbon gain, growth, and freezing susceptibility of four invasive and four native species. Leaf phenology and stem growth were observed for ten individuals per understory wood shrubs species. Freezing damage was experimentally assessed for each species and minimum temperatures in the species' native and exotic ranges were determined. Carbon gain was modeled for six individuals per species based on photosynthetic light response curves, leaf phenology, and understory light.

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