Browsing by Subject "range limits"

Now showing 1 - 5 of 5
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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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    History, dispersal limitation, and environment shape the current and future ranges of forest herbs of the Southern Appalachians
    (2018-08) Erlandson, Stephanie
    As climate changes, favorable climatic conditions for some species might cease to overlap with their current geographic ranges, due to low dispersal rates, barriers to dispersal, or lack of microhabitats, among others. Here, we focus on herbaceous paleoendemics plants in the Southern Appalachian Mountains, possibly threatened by climate change. We developed species distribution models to identify areas of predicted current suitable habitat, both inside and outside of ranges, and evaluated the extent to which these areas shift or move northwards under various future climate scenarios. We discovered predicted suitable habitat in northern areas disjunct from current ranges, suggesting dispersal limitation. We also found severe reductions in predicted suitable habitat under future climate scenarios, both in geographic extent and in percent suitability. Results from models created using more widespread species reinforced these results. Thus, it is imperative to employ conservation efforts in order to prevent species declines or extinctions.
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    Leaf-level trade-offs between drought avoidance and desiccation recovery drive elevation stratification in arid oaks: site environmental data, individual tree stem and leaf physiological data, and analyses
    (2018-02-14) Fallon, Beth; Cavender-Bares, Jeannine; eafallon@umn.edu; Fallon, Beth
    This dataset and RStudio project includes all processed data, most raw data, and R scripts needed for analysis and figure construction included in the manuscript Fallon and J. Cavender-Bares 2018 (Fallon B. and J. Cavender-Bares. 2018. Leaf-level trade-offs between drought avoidance and desiccation recovery drive elevation stratification in arid oaks. Ecosphere. in press). We investigated whether oak species in the Chiricahua Mountains were 1) elevationally stratified, 2) whether that stratification was correlated with temperature minima, maxima, and water availability, 3) if physiological tolerances to freezing or drought stress correlated with elevation ranges, and 4) if traits important to local (elevation) distributions were correlated with climatic values of the wider species ranges. Data were collected at field sites from wild, adult trees in the Chiricahua Mountains, Arizona, USA from 2014-2015.This research was done with funding to B. Fallon from the Southwestern Research Station (SWRS, American Museum of Natural History), the University of Minnesota Charles J. Brand, Carolyn Crosby, and Dayton Bell Fellowships, and the Department of Plant and Microbial Biology. Additional funding was provided by NSF Award 1146380 (J. Cavender-Bares PI). We performed all data collection under permit with the Coronado National Forest, Douglas Ranger District, managed by the United States Forest Service (USDA).
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    Physiological evidence for climate limitations of oak distributions at local and regional scales
    (2017-11) Fallon, Beth
    Understanding the extent to which physiological tolerances of climate may limit plant distributions is critical to predicting the effects of a changing climate. This dissertation research focuses on how responses to drought and cooling influence species ranges among oaks (Quercus L.), a globally-distributed woody genus that is highly diverse within the Americas. I used functional and physiological traits to investigate correlations between cold and drought resistances and climate at two scales: 1) local species elevation limits in a semi-arid montane system and 2) regional range limits among North and Central American oaks. In Chapter 1, I found that a trade-off between the leaf-level drought resistance traits of avoidance (leaf abscission) and desiccation recovery (leaf capacitance), and not stem freezing tolerance, influenced species sorting by elevation in a semi-arid mountain system in the southwestern US. In Chapter 2, I found that stem drought tolerance (xylem vulnerability) is correlated with aridity of climate of origin among oaks from across the Americas, but that the seasonality of precipitation best predicted leaf level drought avoidance (leaf habit and stomatal closure). Finally, in Chapter 3, I found that oak species in the Americas have different leaf level cooling responses (chlorophyll fluorescence measurements of photosynthetic stress and yield) that were correlated with minimum temperatures in their climate of origin, but that ability to acclimate to cold temperatures was best predicted by leaf phenology, not climate of origin. I also found that we could predict chlorophyll fluorescence measurements with models created from hyperspectral reflectance data measured on the same leaves. These models included regions of important biological significance, including wavelengths corresponding with reflectance of photosynthetic and protective pigments. Overall, there I found significant evidence that species distributions are strongly influenced by climate. Oak species have suites of traits as mechanisms of drought resistance, and these strategies are correlated with not only overall aridity in their current habitats, but with the seasonality of precipitation. Oak species may also be able to acclimate to cooler temperatures outside of those commonly experienced in their current range. Oak species within the Americas and the mountainous, arid southwest US, may be vulnerable to range shifts as global temperatures continue to rise and precipitation regimes change.
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    Sugar maple (Acer saccharum Marsh.) provenances differ with climate of origin in survival, growth, and traits along a climate gradient: implications for the species' distribution under climate change
    (2015-12) Putnam, Rachel
    Plant ranges, broadly constrained by climate, may be further shaped by interspecific interactions and intraspecific variation in growth and traits. Changing climate and species composition in plant communities lends urgency to the need to better define the factors determining species’ distributions. This research seeks to determine the effects of temperature and neighbors on sugar maple (Acer saccharum) seedling survival, growth, biomass allocation, and functional traits, and whether this response varies with populations’ climate of origin. I first examine survival and growth of forest-planted seedlings across a natural climate gradient and beyond range limits to determine whether populations’ climate of origin and contrasting neighbor density and light environments affect performance. I find no evidence of climate or competition limitation beyond range margins for populations grown near their region of origin, but populations differ in survival and net growth in a manner consistent with local adaptation and contrasting growth strategies: the northern population has high survival across sites but lower mass than the southern population, which has low survival and growth facilitated by neighbors at northern sites. I then examine whether patterns of root biomass allocation of these same seedlings is affected by climate of the planting site or each populations’ region of origin. I find higher root mass in southern population seedlings than in similarly sized northern population seedlings, and higher root mass fraction at colder sites in the southern (but not northern) population. Finally, I use growth chambers to examine the effects of temperature and light on growth rate and traits for three climatically distinct populations. Growth rate declines with increasing latitude of origin and is lower in the temperature treatment corresponding to the climate of origin for the southern population. High-latitude populations have low SLA and LMF, but populations do not differ in photosynthetic rates. In conclusion, I find potentially adaptive differences in populations’ growth, survival, and plant traits but no direct evidence of climate or competition limitation across the range. This study highlights intraspecific variation in growth and traits, its relevance at range limits, and the need to identify whether reproductive or phenological traits also vary within species.