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15 results for “tree demography”
Forest Inventory for Tree Demography and Carbohydrate Reserves at Harvard Forest 2009-2011
The objective of this study is to establish a network of forest plots spanning the eastern U.S. focused on understanding how regional scale climate patterns affect patterns of tree demography (e.g. growth, mortality, dieback). Within each research site we also aim to understand the landscape-scale variability in demographic rates and how these rates are affected by edaphic variables by aligning plots along primary environmental gradients (elevation, soils, hydrology, fire return interval). The demographic data obtained will also be compared to regional and landscape-scale patterns in carbon reserves in adults and sapling by sampling root and stem concentrations of nonstructural carbohydrates (TNC) and relate these to demographic patterns, life-history traits, and plant C:N ratios. Besides addressing important ecological questions directly, this study is designed to improve the representations of vegetation dynamics and carbohydrate reserves in regional and landscape-scale forest ecosystem models--two of the least data-constrained processes in such models--by parameterizing and validating the modules for these processes in the Ecosystem Demography model (ED v2.1). This data set contains two years of census data for eight mapped plots distributed across Harvard Forest along the aforementioned primary environmental gradients.
Long-term (1962-2019) tree demography on permanent plots in old-growth northern hardwood forests of the Huron Mountains, Marquette Co., Michigan.
This package contains tree demographic data from multiple remeasurements of several sets of permanent study plots in old-growth hemlock-northern hardwood forests in northern Marquette Co., Michigan. Plots were established from 1962-2001, with five to nine censuses over the study period. Plots are distributed over a large and diverse area of old-growth forests protected since ca. 1880, with no commercial management and active management limited to maintenance of trails and tracks. Most plots have not experienced stand-originating disturbances for at least 400 years (based on increment cores); three plots are in stands originating following a fire ca. 1830 ("Bourdo plots" 7094-7096). Forests are dominated by sugar maple (Acer saccharum) and eastern hemlock (Tsuga canadensis); secondary species include yellow birch (Betula alleghaniensis), basswood (Tilia americana), and hop-hornbeam (Ostrya virginiana). Soils are variable, ranging from deep sandy outwash to thin layers of rocky till over bedrock. Mortality and diameter growth of all trees were recorded at each remeasurement. Protocols for measurement and stem-mapping are described in Methods. Several publications use some of the data included in this package -- see 'journal citations'. (identified as Kalkaska series) are developed on deep sandy glacial outwash. The plot is within a much larger region of old-growth forest, protected since ca. 1880, with only minimal disturbance associated with access tracks and trails. Numerous other forest community and dendrochronological studies support the interpretation that the area around the study plot has not experienced stand-initiating disturbance for at least 400 years. Initial mapping and measurements (1993-1995 for 2.52 ha; an additional 0.2 ha added in 1999) used a 20x20 m grid established in a near-level area of uniform substrate. All stems were identified to species, mapped on polar coordinates from the center of each grid cell (including, at first measurement, identif
University of Kansas Field Station: Forest demography, 1980 – 2015. On ten study plots established on three management units all live trees with a dbh > 7.5 cm (3 in) were identified to species, measured, and tagged. Trees were initially measured in 1980/1981 and re-measured in three successive time periods: 1993/95; 2002/03; and 2014/15. Trees will be measured again in 2025/26.
In 1980 researchers at the University of Kansas initiated a long-term experiment monitoring the composition of oak-hickory forest communities at the University’s field station near Lawrence, Kansas. The purpose of the study was to determine how forest species composition varied temporally across distinct habitats that varied in topography, elevation, sun exposure, management history and successional stage. Ten permanent sites were sampled approximately each decade with data collection periods of 1980/81, 1993/95, 2002/03, and 2014/15. Trees with a minimum diameter at breast height (dbh) of ≥ 7.5 cm were tagged, identified to species and measured. Trees will be measured again in 2025/26.
Tree census, demography, and exposed canopy area data at the Coweeta LTER Terrestrial Gradient Sites, Coweeta Hydrological Laboratory, Otto, NC from 1993 to 2016
The five Terrestrial Gradient sites were established in the early 1990s as part of the 1990 Coweeta LTER Renewal. The original terrestrial gradient sites were 20 x 40-m. In the late 1990s the plots were expanded to 80 x 80-m and later (around 1998) they were slope-corrected by Clark's lab using survey equipment. Much of the Coweeta LTER “core” datasets have been collected from the gradient plots. This study is one of the long-term studies that are ongoing with defined sampling intervals. The tree demography and census study consists of trees census every two years and seeds collected ~5 x each year.
Long-term study of tree cholla demography in the Los Pinos mountains, Sevilleta National Wildlife Refuge
This study was initiated in 2004 by TEX Miller to quantify individual-level demographic rates of tree cholla cacti (Cylindriopuntia imbricata) at the Sevilleta National Wildlife Refuge, Socorro Co., NM. This data package spans 2004-2018, though the study is maintained through the present. In each year, censuses were conducted over several days in the last week of May and/or the first week of June. Individuals were marked with aluminum tags and tracked longitudinally through time, with annual measures of survival, size, reproductive output, and interactions with insect herbivores and mutualists (extra-floral nectar-feeding ants). For the years 2004-2008, plants were grouped into spatial blocks (T1, T2, T3) lacking defined boundaries. Beginning in 2009, the study design changed to 30m x 30m plots (Plots 1-8) with an entirely new cohort of individuals that does not overlap with the 2004-2008 data. From 2009 onward, plots were searched each year and new plants were added to the census as they were discovered. Seedlings typically require several years of growth before they are detectable in our census, so counts of new plants in a given year do not necessarily reflect recruitment in that year. The data frame is set up such that one row is a transition year (May of year t to May of year t+1) for one individual; this means that all but the first and last years’ observations occur twice, once as the start of a transition year and once as the end.
Data from: The demography of a resource specialist in the tropics: Cecropia trees and the fitness of three-toed sloths
Resource specialists persist on a narrow range of resources. Consequently, the abundance of key resources should drive vital rates, individual fitness and population viability. While Neotropical forests feature both high levels of biodiversity and numbers of specialist species, no studies have directly evaluated how the variation of key resources affects the fitness of a tropical specialist. Here, we quantified the effect of key tree species density and forest cover on the fitness of three-toed sloths (Bradypus variegatus), an arboreal folivore strongly associated with Cecropia trees, in Costa Rica using a multi-year demographic, genetic and space use dataset. We found that the density of Cecropia trees was strongly and positively related to both adult survival and reproductive output. A matrix model parameterized with Cecropia-demography relationships suggested positive growth of sloth populations, even at low densities of Cecropia (0.7 trees/ha). Our study shows the first direct link between the density of a key resource to demographic consequences of a tropical specialist, underscoring the sensitivity of tropical specialists to the loss of a single key resource, but also point to targeted conservation measures to increase that resource. Finally, our study reveals that previously disturbed and regenerating environments can support viable populations of tropical specialists.
Twenty-five years of tree demography in a frequently burned oak woodland
<p>Due to decades of fire suppression, much of the Upper Midwest savanna habitat has converted to oak woodland. In efforts to restore oak savanna habitat, fire has been re-introduced in many of these woodlands. A primary purpose of these burns is to kill the fire-sensitive mesophytic tree species, which had established themselves during the decades of fire suppression, reduce the number of understory trees, and preserve the larger more widely spaced oaks. It is clear from ongoing efforts that restoring oak savannas will require frequent fires over decades. But frequent fires over the long term can also threaten the desirable oaks. Long-term demographic studies at savanna restoration sites experiencing frequent fires are necessary to determine the extent to the frequent burns are supporting and/or confounding restoration goals. Results presented here are from a twenty-five-year demographic study of an Upper Midwest bur oak (<i>Quercus macrocarpa</i>)<i> </i>savanna/woodland experiencing frequent fire, during which both the survival and growth of more than 9,000 trees were documented. Survival was assessed annually and growth every five years. In the face of frequent fires, stem survival was found to be strongly associated with tree species, stem size, and stem growth. In turn, stem growth was found to be related to tree species and stem size. Decades of frequent burning in this oak woodland have substantially reduced the abundance of unwanted trees, specifically mesophytic species and <i>Q. ellipsoidalis</i>, the latter which outcompetes <i>Q. macrocarpa </i>in the absence of fire. While <i>Q. macrocarpa</i> mid-sized (10-25 cm dbh) and large (<u>></u> 25 cm dbh) trees are quite resistant to fire and now dominate the savanna landscape, they are not immune from fire-induced mortality. It is recommended that the number and density of these trees should be re-evaluated every few years to ensure that desirable numbers remain. If necessary, fires should be suspended for a period of time. This will give smaller <i>Q. macrocarpa </i>trees time to grow larger and become more fire-resistant, thereby ensuring successive generations of <i>Q. macrocarpa</i>. </p>
Data from: Trait interactions effects on tropical tree demography depend on the environmental context
<p><span class="fontstyle0">Although functional traits are defined based on their impact on demographic parameters, trait-demography relationships are often reported as weak. These weak relationships might be due to disregarding trait interactions and environmental contexts, which should modulate species trait-demography relationships. We applied different models, including boosted regression tree (BRT) models, to investigate changes in the relationship between traits and demographic rates of tropical tree species in plots along an elevational gradient and among time intervals between censuses, analyzing the effect of a strong drought event. Based on a large dataset of 18,000 tree individuals from 133 common species, distributed among twelve 1-ha plots (habitats) in the Atlantic Forest (Brazil), we evaluated how trait interactions and the environmental context influence the demographic rates (growth, mortality, and recruitment). Functional traits, trait-trait, and trait-habitat interactions predicted demography with a good fit through either BRTs or linear mixed-models. Changes in growth rates were best related to size (diameter), and mortality rates to habitats, while changes in recruitment rates were best related to the specific leaf area. Moreover, the influence of traits differed among time intervals, and for demographic parameters, habitat affected growth and mortality by interacting with diameter. Here, we provide evidence that trait-demography relationships can be improved when considering the environmental context (space and time) and trait interactions to cope with the complexity of changes in the demography of tropical tree communities. Thus, to expand predictions of demography based on functional traits, we show that it is useful to fully incorporate the concept of multiple trait-fitness optima, resulting from trait interactions in different habitats and growth conditions.</span> </p>
Data from: The demography of a resource specialist in the tropics: Cecropia trees and the fitness of three-toed sloths
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Twenty-five years of tree demography in a frequently burned oak woodland
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Data from: Trait interactions effects on tropical tree demography depend on the environmental context
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Data and code from: Climate change, tree demography, and thermophilization in western US forests
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Data from: Demography and growth of subadult savanna trees: interactions of life history, size, fire season, and grassy understory
Tree populations in mesic (>650 mm precipitation/yr) savannas of the world have strong demographic bottlenecks to the transition of subadult trees to the canopy layer. Although such bottlenecks are a major determinant of savanna physiognomy, the factors that allow subadults to traverse the bottleneck are little studied. In a landscape-scale field experiment in a northern Australia savanna, we determined the survival and growth of 1506 permanently marked juveniles (<150 cm tall) and saplings (150–599 cm tall) of canopy species in response to season of fire (early dry season, late dry season, wet season, and unburned), and understory type (herbaceous forbs vs. sorghum [native annual grass]) that differ in seasonal growth patterns and competitive regimes. Trees were assessed before fires and at the end of the following growing season, without repeat fires. We used Akaike-information-criterion-based model selection and multi-model inference for data analyses. Initial height was an important explanatory variable for all responses except genet mortality wherein fire season was important for juveniles and understory type for saplings. Fire season was important to height growth of large juveniles and small saplings (enhanced the year following dry-season fires). Fire season × understory interactions were important for height growth of small juveniles and for the proportion of juveniles transitioning to saplings. Changes in stem numbers were affected by all explanatory variables. All fires topkilled most juveniles (fewer in early dry-season fires in herbaceous understory), but genet death was rare. Late dry-season fires topkilled most saplings; they failed to regain previous height and some died the following year. Given no further fires, persistent large juveniles can grow to sapling size within a year; whereas sapling success is severely hampered by late-dry-season fires, especially in grassy understory. Differences in seasonal phenological patterns of both understory vegetation and trees that vary with size and life history stage are among suggested explanatory mechanisms. Weighted averaged model coefficients for all responses to the explanatory variables are provided for use in population dynamics models. A conceptual framework links landscape-scale variables to tree attributes and responses, with implications for population ecology and community assembly.
Data from: The population demography of Betula maximowicziana, a cool temperate tree species in Japan, in relation to the last glacial period: Its admixture-like genetic structure is the result of simple population splitting not admixing
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Data from: Demography and growth of subadult savanna trees: interactions of life history, size, fire season, and grassy understory
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