Browsing by Subject "provenance"

Now showing 1 - 4 of 4
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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.
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    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.
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    Managing Data Quality in Observational Citizen Science
    (2017-12) Sheppard, S.
    Observational citizen science is an effective way to supplement the environmental datasets compiled by professional scientists. Involving volunteers in data collection has the added educational benefits of increased scientific awareness and local ownership of environmental concerns. This thesis provides an in-depth exploration of observational citizen science and the associated challenges and opportunities for HCI research. We focus on data quality as a key lens for understanding observational citizen science, and how it differs from the related domains of crowdsourcing, open collaboration, and volunteered geographic information. In order to understand data quality, we performed a qualitative analysis of data quality assurance practices in River Watch, a regional water quality monitoring program. We found that data quality in River Watch is primarily maintained through universal adherence to standard operating procedures, rather than through a computable notion of “accuracy”. We also found that rigorous data quality assurance practices appear to enhance rather than hinder the educational goals of the program participants. In order to measure data quality, we conducted a quantitative analysis of CoCoRaHS, a multinational citizen science project for observing precipitation. Given the importance of long-term participation to data consumers, we focused on volunteer retention as our primary metric for data quality. Through survival analysis, we found that participant age is a significant predictor of retention. Compared to all other age groups, participants aged 60-70 are much more likely to sign up for CoCoRaHS, and to remain active for several years. We propose that the nature of the task can profoundly influence the types of participants attracted to a project. In order to improve data quality, we derived a general workflow model for observational citizen science, drawing on our findings in River Watch, CoCoRaHS, and similar programs. We propose a data model for preserving provenance metadata that allows for ongoing data exchange between disparate technical systems and participant skill levels. We conclude with general principles that should be taken into consideration when designing systems and protocols for managing citizen science data.
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    Needle nutrients in geographically diverse Pinus sylvestris L. populations
    (2002) Oleksyn, Jacek; Reich, Peter B; Zythowiak, Roma; Karolewski, Piotr; Tjoelker, Mark G
    Nutrient availability differs across climatic gradients, yet the role of genetic variation in potentially adaptive traits related to nutrient acquisition remains poorly understood. We examined needles of diverse Scots pine provenances grown under common-garden conditions throughout their entire life span. Based on similarities in nutrient concentration patterns, two groups of populations were identified. One comprised northern populations from 60° to 56° N, and another included populations from locations between 56° and 49° N. Northern populations sustained significantly higher concentrations of N, P, Ca, Mg, Na, Zn, Cu and Pb. Only K concentration was persistently lower in northern plants. We conclude that intraspecific genetic differences exist in foliage nutrient concentration among diverse populations. Since in northern conditions nutrient availability is often limited as a result of interactions between temperature, litter quality and its mineralization, a tendency toward higher foliage concentrations of macronutrients can be an adaptive feature enhancing plants metabolic activity in their native habitats.