Tree Island Research Articles

Ability to home in small site-attached coral reef fishes.

The ability of two common, site-attached coral-reef fishes to return to their home corals after displacement was investigated in a series of field experiments at One Tree Island, southern Great Barrier Reef. The humbug Dascyllus aruanus was displaced up to 250 m, with 42% of individuals returning home, irrespective of body size, displacement, direction (up or across currents) and route complexity, while for the lemon damselfish Pomacentrus moluccensis 35% of individuals returned overall, with 33% from the greatest displacement, 100 m along a reef edge. Given that the home range of both species is <1 m(2) , over their 10+ year life span, the mechanisms and motivations for such homing ability are unclear but it may allow resilience if fishes are displaced by storm events, allowing rapid return to home corals.

Tropical forest restoration enriches vascular epiphyte recovery

AbstractQuestionsVascular epiphytes constitute a large proportion of tropical forest plant biodiversity, but are among the slowest plants to recolonize secondary forests. We asked whether tree planting for ecological restoration accelerates epiphyte community recovery. Does the spatial configuration of tree planting matter? What landscape contexts are most suitable for epiphyte restoration?LocationRestored pastures in premontane Coto Brus County, Puntarenas, Costa Rica.MethodsWe surveyed vascular epiphyte species growing on the lower trunks of 1083 trees in 13 experimental restoration sites. Each site contained three 0.25‐ha treatment plots: natural regeneration, trees planted in patches or ‘islands’ and tree plantations. Sites spanned elevational (1100–1430 m) and deforestation (4–94% forest cover within a 100‐m radius around each site) gradients.ResultsVascular epiphytes were twice as diverse in planted restoration plots (islands and plantations) as in natural regeneration; we observed this at the scale of individual host trees and within 0.25‐ha treatment plots. Contributing factors included that trees in planted restoration plots were larger, older, more abundant and composed of different species than trees in naturally regenerating plots. Epiphyte species richness increased with surrounding forest cover within 100–150 m of restoration plots. Epiphyte communities were also twice as diverse at higher (1330–1430 m) vs lower (1100–1290 m) elevation sites. Epiphyte groups responded differently to restoration treatments and landscape factors; ferns were responsible for higher species richness in planted restoration plots, whereas angiosperms drove elevation and forest cover effects.ConclusionsTree planting for ecological restoration enriched epiphyte communities compared to natural regeneration, likely because planted forests contained more, bigger and older trees. Tree island plantings were equally effective compared to larger and more expensive plantations. Restoration sites nearer to existing forests had richer epiphyte recolonization, likely because nearby forests provisioned restoration sites with angiosperm seeds. Collectively, results suggest that restoration practitioners can enrich epiphyte community development by planting trees in areas with higher surrounding forest cover, particularly at higher elevations.

The Importance of Conifers for Facilitation at Treeline: Comparing Biophysical Characteristics of Leeward Microsites in Whitebark Pine Communities

ABSTRACTIn many of the alpine-treeline ecotones (ATE) of the Rocky Mountains, Pinus albicaulis (whitebark pine) is the most common conifer initiating tree islands through facilitation. We examined whether microsites leeward of P. albicaulis experience more moderate microclimate, less sky exposure, and more total soil carbon and nitrogen than other common types of leeward microsites. From July to September 2010, 2011, and 2012, in two study areas on the eastern Rocky Mountain Front, we compared microclimate, sky exposure, and total soil carbon and nitrogen leeward of four common microsites, P. albicaulis, Picea engelmannii (Engelmann spruce), rock, and unprotected (exposed). Microsites leeward of P. albicaulis did not consistently experience the most moderate microclimate, but both P. albicaulis and P. engelmannii leeward microsites had lower daily photosynthetically active radiation (PAR), lower average wind speeds, lower soil temperature maxima, and higher soil temperature minima. In general, conifer microsites had significantly lower values for sky exposure; but, the performance of each microsite type varied from micro to study-area scales. Our results highlight the importance of conifers as nurse objects for facilitating treeline community development in the ATE, and especially P. albicaulis because of its high abundance. High losses of P. albicaulis from infection by Cronartium ribicola may alter community dynamics and treeline response to climate warming.

Trees: a powerful geomorphic agent governing the landscape evolution of a subtropical wetland

Transpiration-driven ion accumulation in soil has been invoked as a biological and physical feedback mechanism in wetlands that governs topographic differences by regulating soil accretion—with greater transpiration, ion accumulation and soil accretion occurring on tree islands as compared to the surrounding marsh. The strength of this mechanism is hypothesized to be controlled by the ratio of evapotranspiration (ET) to precipitation (P), where under greater ET to P conditions soil accretion may move from organic to mineral in nature. We tested the existence of this mechanism on tree islands in a subtropical wetland, determined if it supports mineral soil formation, and assessed its control on the development of nutrient resource contrasts (tree islands–marsh). To test our hypotheses, biannual measurements of groundwater, surface water and aboveground biomass were made from 2007 to 2012. Water samples were analyzed for water isotopes, concentrations of major ions, and total and dissolved nutrients on constructed tree islands. We found that tree transpiration led to the advective movement of water and associated ions toward the center of the tree islands, supporting CaCO3 precipitation. CaCO3 accretion on the tree islands was estimated at roughly 1 mm per decade, and represented 5 % of the total soil accretion since the islands’ planting. We also observed depletion in groundwater nutrient concentrations as tree biomass accumulated, indicative of tight nutrient cycling. This work provides direct evidence that trees can act as powerful geomorphic agents in wetland systems, forming mineral soils that support landscape heterogeneity on time scales of centuries to millennia.

Tree island pattern formation in the Florida Everglades

The Florida Everglades freshwater landscape exhibits a distribution of islands covered by woody vegetation and bordered by marshes and wet prairies. Known as “tree islands”, these ecogeomorphic features can be found in few other low gradient, nutrient limited freshwater wetlands. In the last few decades, however, a large percentage of tree islands have either shrank or disappeared in apparent response to altered water depths and other stressors associated with human impacts on the Everglades. Because the processes determining the formation and spatial organization of tree islands remain poorly understood, it is still unclear what controls the sensitivity of these landscapes to altered conditions. We hypothesize that positive feedbacks between woody plants and soil accretion are crucial to emergence and decline of tree islands. Likewise, positive feedbacks between phosphorus (P) accumulation and trees explain the P enrichment commonly observed in tree island soils. Here, we develop a spatially-explicit model of tree island formation and evolution, which accounts for these positive feedbacks (facilitation) as well as for long range competition and fire dynamics. It is found that tree island patterns form within a range of parameter values consistent with field data. Simulated impacts of reduced water levels, increased intensity of drought, and increased frequency of dry season/soil consuming fires on these feedback mechanisms result in the decline and disappearance of tree islands on the landscape.

Tardigrades of the Canopy: Argentine SpeciesMilnesium beataeRoszkowska, Ostrowska and Kaczmarek, 2015 (Eutardigrada, Milnesidae) Discovered in the Trees of Kansas, U.S.A.

During the summer of 2015, a recently described species of tardigrade from southern Argentina, Milnesium beatae Roszkowska, Ostrowska and Kaczmarek, 2015, was discovered in the canopy of trees in Kansas, USA. Seven specimens of the southern hemisphere species were collected from lichen habitat above six meters on red oak tree substrates in a tree island on the edge of the tall grass prairie. Statistical comparison of the characteristics of the specimens of the two populations demonstrates that they are morphologically the same. Two new characters are described: first, small cuticular bars at the base of legs IV and second, thin plates (pseudoplates) in the dorsal and lateral cuticle are exposed by UV fluorescence imagery. Bird nesting habits and migration patterns are explored to explain how the same species of microscopic water bear is known to only occur at disparate locations 9,000 km apart in different hemispheres.

Evolutionary history shapes the susceptibility of an island tree flora to an exotic pathogen

With globalisation, the world’s native biotas are increasingly exposed to disease, parasitism, herbivory and competition from exotic organisms. The vulnerability of native biota to these exotic invasions is exacerbated by human disturbance and global climate change. Rust pathogens are some of the most important plant pathogens, including Puccinia psidii (myrtle rust or guava rust) that is now spreading worldwide at an alarming rate. P. psidii is native to South America and affects species in the family Myrtaceae, including the economically and ecologically important eucalypts. The Australian continent has a rich myrtaceous flora and is the centre of origin of most eucalypt species. P. psidii was first detected in Australia in 2010 and has since rapidly spread along its east coast. We assess the risk this exotic pathogen poses to the eucalypt flora of the southern Australian island of Tasmania, where the first incursion of P. psidii was detected in early 2015. Specifically, we tested the relative importance of phylogenetic history, habitat, endemism, and range size in predicting host susceptibility.Rust screening of seedlings from one to four populations of each of the 30 eucalypt species which are native to Tasmania, revealed significant genetic-based variation in response among host species and populations within the species. Significant population differences in susceptibility were detected in threatened, rare and endemic eucalypt species, as well as Australia’s main plantation eucalypt (Eucalyptus globulus) and the world’s tallest angiosperm species (Eucalyptus regnans). A significant proportion of the variation in host species susceptibility to this exotic pathogen was explained by phylogenetic history, while factors such as habitat, endemism and range size had no detectable effect. Species from subgenus Eucalyptus (13 species) were more susceptible than those from subgenus Symphyomyrtus (17 species) due to differences between the subgenera in the proportion of plants showing a symptomless response. These subgenera are here shown to differ in their leaf oil and wax chemistry. The potential contribution of these differences and other possible mechanisms causing these subgeneric differences in susceptibility are discussed. This study demonstrates the power of a phylogenetic approach to risk assessment for biosecurity and highlights the need for broader resistance screening within and between populations of species of high conservation or economic value.

Prehistoric human impact on tree island lifecycles in the Florida Everglades

The current study provides a fine-grained analysis of evidence for sustained pre-Columbian human occupation and socio-ecological interaction within Everglades National Park. Utilizing archaeological data on dietary and cultural patterns recovered from recent excavations at a prehistoric tree island site, we argue the role of ancient human populations in the formation or augmentation of tree islands should be incorporated into environmental models of the tree island lifecycle. High phosphorus levels in human waste, especially the largely organic waste of prehistoric populations, as well as other anthropogenic factors have not been adequately factored into current environmental models of tree island formation or the ecological evolution of the Everglades. More broadly, while socio-ecological modeling is at the core of current scholarly and restoration paradigms, expanded collaboration between environmental scientists and archaeologists will lead to more accurate identification of anthropogenic environmental impacts over time.

Early human settlement and natural formation of the Florida Everglades, USA: The Ichthyoarchaeological evidence

The Everglades, the largest subtropical wetland in North America, was initially formed by natural processes approximately 5000years ago and has since dominated the interior landscape of south Florida. Scattered throughout this vast freshwater marsh are tree islands, small clusters of trees situated on slightly elevated ground, which stand out conspicuously amid the surrounding lower vegetation. As the only dry land available, tree islands were ideal for human settlements in the distant past and contain numerous archeological sites. Recent excavations at several sites lend further support to existing evidence that human populations had initially camped on these interior tree islands quite early in time. One such site is Heartleaf Hammock, where rich well-preserved midden deposits demonstrate that people intensively occupied and used locally available aquatic resources, especially fish, as early as 4400years ago. Moreover, the kinds and relative quantities of fish and other freshwater fauna represented indicate that the Everglades wetland marsh ecosystem was already in existence at the time of this early human occupation.

Movements, Home Range and Site Fidelity of Snapper (Chrysophrys auratus) within a Temperate Marine Protected Area.

Understanding the movement dynamics of marine fish provides valuable information that can assist with species management, particularly regarding protection within marine protected areas (MPAs). We performed an acoustic tagging study implemented within the Port Stephens-Great Lakes Marine Park on the mid-north coast of New South Wales, Australia, to assess the movement patterns, home range and diel activity of snapper (Chrysophrys auratus; Sparidae); a species of significant recreational and commercial fishing importance in Australia. The study focused on C. auratus movements around Cabbage Tree Island, which is predominantly a no-take sanctuary zone (no fishing), with an array of acoustic stations deployed around the island and adjacent reefs and islands. Thirty C. auratus were tagged with internal acoustic tags in November 2010 with their movements recorded until September 2014. Both adult and juvenile C. auratus were observed to display strong site fidelity to Cabbage Tree Island with a mean 12-month residency index of 0.83 (range = 0 low to 1 high). Only three fish were detected on acoustic receivers away from Cabbage Tree Island, with one fish moving a considerable distance of ~ 290 kms over a short time frame (46 days). The longest period of residency recorded at the island was for three fish occurring regularly at the site for a period of 1249 days. Chrysophrys auratus displayed strong diurnal behaviour and detection frequency was significantly higher during the day than at night; however, there was no significant difference in detection frequency between different hours. This study demonstrates that even small-scale protected areas can benefit C. auratus during multiple life-history stages as it maintains a small home range and displays strong site fidelity over a period of 3 years.

Winter conditions – not summer temperature – influence establishment of seedlings at white spruce alpine treeline in Eastern Quebec

AbstractAimsWhile treeline positions are globally correlated to growing season temperatures, seedling establishment, an important process of alpine treeline dynamics, is additionally controlled by regional‐scale factors such as snow cover duration, desiccating winds and biotic interactions. Knowing that alpine treelines have shown contrasting responses to climate change, we determined the relative importance of key abiotic and biotic factors involved in seedling survival and growth.LocationMcGerrigle Mountains, Parc National de la Gaspésie, Appalachian Range, eastern Quebec, Canada.MethodsIn two white spruce (Picea glauca) treeline sites, we used the microclimate in the vicinity of tree islands, densely packed clusters of trees isolated from each other by alpine tundra vegetation, to assess the effects of abiotic variables (sum of degree days [DD], snowpack duration and a wind exposure index) as well as the effects of biotic interactions with neighbouring vegetation on the survival and growth of transplanted white spruce seedlings. For 3 yr, we surveyed seedling survival twice a year to discriminate between winter and summer survival, and measured seedling growth at the end of each growing season. We used Bayesian hierarchical models to estimate the relative effects of covariates on survival and growth.ResultsSurvival probability decreased in microsites where winter DD was high, and increased in microsites with longer snowpack duration. In wind‐exposed microsites, seedling survival increased when neighbouring vegetation was present, indicating facilitative mechanisms. Seedling growth was positively affected by the duration of snow cover and tended to increase with higher DD during the previous year. In wind‐sheltered microsites, seedling growth tended to be negatively affected by neighbouring vegetation, indicating competitive mechanisms.ConclusionsOur study demonstrates that seedling establishment is more sensitive to winter conditions, notably to the length of snow cover (which protects seedlings from frost and desiccation), than to summer temperature. Biotic interactions increased seedling establishment when environmental stresses were higher. We suggest that regional‐scale factors such as winter climate and biotic interactions should be included in modelling exercises to improve future treeline location forecasts.

Scale‐dependent effects of forest restoration on Neotropical fruit bats

Neotropical fruit bats (family Phyllostomidae) facilitate forest regeneration on degraded lands by dispersing shrub and tree seeds. Accordingly, if fruit bats can be attracted to restoration sites, seed dispersal could be enhanced. We surveyed bat communities at 10 sites in southern Costa Rica to evaluate whether restoration treatments attracted more fruit bats if trees were planted on degraded farmlands in plantations or island configurations versus natural regeneration. We also compared the relative influence of tree cover at local and landscape spatial scales on bat abundances. We captured 68% more fruit bat individuals in tree plantations as in controls, whereas tree island plots were intermediate. Bat activity also responded to landscape tree cover within a 200‐m radius of restoration plots, with greater abundance but lower species richness in deforested landscapes. Fruit bat captures in controls and tree island plots declined with increasing landscape tree cover, but captures in plantations were relatively constant. Individual species responded differentially to tree cover measured at different spatial scales. We attribute restoration effects primarily to habitat structure rather than food resources because no planted trees produced fruits regularly eaten by bats. The magnitude of tree planting effects on fruit bats was less than previous studies have found for frugivorous birds, suggesting that bats may play a particularly important role in dispersing seeds in heavily deforested and naturally regenerating areas. Nonetheless, our results show that larger tree plantations in more intact landscapes are more likely to attract diverse fruit bats, potentially enhancing seed dispersal.

Wading bird guano enrichment of soil nutrients in tree islands of the Florida Everglades

Differential distribution of nutrients within an ecosystem can offer insight of ecological and physical processes that are otherwise unclear. This study was conducted to determine if enrichment of phosphorus (P) in tree island soils of the Florida Everglades can be explained by bird guano deposition. Concentrations of total carbon, nitrogen (N), and P, and N stable isotope ratio (δ15N) were determined on soil samples from 46 tree islands. Total elemental concentrations and δ15N were determined on wading bird guano. Sequential chemical extraction of P pools was also performed on guano. Guano contained between 53.1 and 123.7g-Nkg−1 and 20.7 and 56.7g-Pkg−1. Most of the P present in guano was extractable by HCl, which ranged from 82 to 97% of the total P. Total P of tree islands classified as having low or high P soils averaged 0.71 and 40.6gkg−1, respectively. Tree island soil with high total P concentration was found to have a similar δ15N signature and total P concentration as bird guano. Phosphorus concentrations and δ15N were positively correlated in tree island soils (r=0.83, p<0.0001). Potential input of guano with elevated concentrations of N and P, and 15N enriched N, relative to other sources suggests that guano deposition in tree island soils is a mechanism contributing to this pattern.

Seed dispersal limitations shift over time in tropical forest restoration.

Past studies have shown that tropical forest regeneration on degraded farmlands is initially limited by lack of seed dispersal, but few studies have tracked changes in abundance and composition of seed rain past the first few years after land abandonment. We measured seed rain for 12 months in 10 6-9-year-old restoration sites and five mature, reference forests in southern Costa Rica in order to learn (1) if seed rain limitation persists past the first few years of regeneration; (2) how restoration treatments influence seed community structure and composition; and (3) whether seed rain limitation is contingent on landscape context. Each restoration site contained three 0.25-ha treatment plots: (1) a naturally regenerating control, (2) tree islands, and (3) a mixed-species tree plantation. Sites spanned a deforestation gradient with 9-89% forest area within 500 m around the treatment plots. Contrary to previous studies, we found that tree seeds were abundant and ubiquitous across all treatment plots (585.1 ± 142.0 seeds · m(-2) · yr(-1) [mean ± SE]), indicating that lack of seed rain ceased to limit forest regeneration within the first decade of recovery. Pioneer trees and shrubs comprised the vast majority of seeds, but compositional differences between restoration sites and reference forests were driven by rarer, large-seeded species. Large, animal-dispersed tree seeds were more abundant in tree islands (4.6 ± 2.9 seeds · m(-2) · yr(-1)) and plantations (5.8 ± 3.0 seeds · m(-2) · yr(-1)) than control plots (0.2 ± 0.1 seeds · m(-2) · yr(-1)), contributing to greater tree species richness in actively restored plots. Planted tree species accounted for < 1% of seeds. We found little evidence for landscape forest cover effects on seed rain, consistent with previous studies. We conclude that seed rain limitation shifted from an initial, complete lack of tree seeds to a specific limitation on large-seeded, mature forest species over the first decade. Although total seed abundance was equal among restoration treatments, tree plantations and tree islands continued to diversify seed rain communities compared to naturally regenerating controls. Compositional differences between regenerating plots and mature forests suggest that large-seeded tree species are appropriate candidates for enrichment planting.

Even the smallest non-crop habitat islands could be beneficial: distribution of carabid beetles and spiders in agricultural landscape.

Carabid beetles and ground-dwelling spiders inhabiting agroecosystems are beneficial organisms with a potential to control pest species. Intensification of agricultural management and reduction of areas covered by non-crop vegetation during recent decades in some areas has led to many potentially serious environmental problems including a decline in the diversity and abundance of beneficial arthropods in agricultural landscapes. This study investigated carabid beetle and spider assemblages in non-crop habitat islands of various sizes (50 to 18,000 square metres) within one large field, as well as the arable land within the field, using pitfall traps in two consecutive sampling periods (spring to early summer and peak summer). The non-crop habitat islands situated inside arable land hosted many unique ground-dwelling arthropod species that were not present within the surrounding arable land. Even the smallest non-crop habitat islands with areas of tens of square metres were inhabited by assemblages substantially different from these inhabiting arable land and thus enhanced the biodiversity of agricultural landscapes. The non-crop habitat area substantially affected the activity density, recorded species richness and recorded species composition of carabid and ground-dwelling spider assemblages; however, the effects were weakened when species specialised to non-crop habitats species were analysed separately. Interestingly, recorded species richness of spiders increased with non-crop habitat area, whereas recorded species richness of carabid beetles exhibited an opposite trend. There was substantial temporal variation in the spatial distribution of ground-dwelling arthropods, and contrasting patterns were observed for particular taxa (carabid beetles and spiders). In general, local environmental conditions (i.e., non-crop habitat island tree cover, shrub cover, grass cover and litter depth) were better determinants of arthropod assemblages than non-crop habitat island size, indicating that the creation of quite small but diversified (e.g., differing in vegetation cover) non-crop habitat islands could be the most efficient tool for the maintenance and enhancement of diversity of ground-dwelling carabids and spiders in agricultural landscapes.

Home range, habitat use, and movement patterns of non-native Burmese pythons in Everglades National Park, Florida, USA

Studies on the spatial ecology of invasive species provide critical information for conservation managers such as habitat preferences and identification of native species at risk of predation. To understand the spatial ecology of non-native Burmese pythons (Python molurus bivittatus), now well-established in Everglades National Park and much of South Florida USA, we radio-tracked 19 wild-caught adult pythons, 16 with VHF tags during 2006 through 2009 and 3 by GPS tags between 2010 and 2011. Our goal was to identify individual core-use areas and quantify home ranges, as well as to explore correlations of python movements with environmental parameters such as the presence of surface water. Radio-tracking periods ranged from 87 to 697 days for snakes with VHF tags, with a total of 5,119 tracking days (mean ± 1 SD = 319.9 ± 184.3 days); GPS tracking periods ranged from 12 to 93 days, with a total of 146 tracking days (mean ± 1 SD = 48.7 ± 40.7 days). We observed mean individual radio-tracked python home ranges of 22.5 km2 (2250 ha) with overall low site fidelity; all home ranges were within the park boundary. Python core-use areas included slough and coastal habitat types, and we delineated 18 common-use areas (that is, areas where individual core-use areas spatially overlapped). Tree islands were a principal feature of common-use areas, even if they were not the predominant habitat type. Multiple common-use areas were in proximity to roads. The longest movements of individual pythons correlated well with presence of surface water, and occurred during both wet and dry seasons. High-use areas determined from python habitat-use and movement data may be optimal locations for targeted control efforts and further studies on impacts to native fauna.

Natural in situ relationships suggest coral reef calcium carbonate production will decline with ocean acidification

AbstractThere are few in situ studies showing how net community calcification (Gnet) of coral reefs is related to carbonate chemistry, and the studies to date have demonstrated different predicted rates of change. In this study, we measured net community production (Pnet), Gnet, and carbonate chemistry of a reef flat at One Tree Island, Great Barrier Reef. Diurnal pCO2 variability of 289–724 μatm was driven primarily by photosynthesis and respiration. The reef flat was found to be net autotrophic, with daily production of ∼ 35 mmol C m−2 d−1 and net calcification of ∼ 33 mmol C m−2 d−1. Gnet was strongly related to Pnet, which drove a hysteresis pattern in the relationship between Gnet and aragonite saturation state (Ωar). Although Pnet was the main driver of Gnet, Ωar was still an important factor, where 95% of the variance in Gnet could be described by Pnet and Ωar. Based on the observed in situ relationship, Gnet would be expected to reach zero when Ωar is ∼ 2.5. It is unknown what proportion of a decline in Gnet would be through reduced calcification and what would occur through increased dissolution, but the results here support predictions that overall calcium carbonate production will decline in coral reefs as a result of ocean acidification.

Predicted changes in interannual water-level fluctuations due to climate change and its implications for the vegetation of the Florida Everglades.

The number of dominant vegetation types (wet prairies, sawgrass flats, ridges and sloughs, sloughs, and tree islands) historically and currently found in the Everglades, FL, USA, as with other wetlands with standing water, appears to be primarily a function of the magnitude of interannual water-level fluctuations. Analyses of 40 years of water-depth data were used to estimate the magnitude of contemporary (baseline) water-level fluctuations in undisturbed ridge and slough landscapes. Baseline interannual water-level fluctuations above the soil surface were at least 1.5 m. Predicted changes in interannual water-level fluctuations in 2060 were examined for seven climate change scenarios. When rainfall is predicted to increase by 10 %, the wettest scenario, the interannual range of water-level fluctuation increases to 1.8 m above the soil surface in sloughs. When rainfall is predicted to decrease by 10 % and temperatures to increase by 1.5 °C, the driest scenario, the range of interannual range of water-level fluctuations is predicted to decrease to 1.2 m above the soil surface in sloughs. A change of 25-30 cm in interannual water-level fluctuations is needed to change the number of vegetation types in a wetland. This suggests that the two most extreme climate change scenarios could have a significant impact on the overall structure of wetland vegetation, i.e., the number of vegetation types or zones, found in the Everglades.

Bringing the Benefits of Tree Islands Back to the Everglades

Bringing the Benefits of Tree Islands Back to the Everglades

Assessing Functional Role and Community Dynamics of Whitebark Pine at Alpine Treeline, Grand Teton National Park

Whitebark pine (Pinus albicaulis) is a keystone and foundation tree species in high elevation ecosystems of the Rocky Mountains. At alpine treelines along the eastern Rocky Mountain Front and in the Greater Yellowstone Ecosystem, whitebark pine often initiates tree islands through facilitation, thereby shaping vegetation pattern. This role will likely diminish if whitebark pine succumbs to white pine blister rust infection, climate change stress, and mountain pine beetle infestations. Here, we established baseline measurements of whitebark pine’s importance and blister infection rates at two alpine treelines in Grand Teton National Park. Our specific objectives were to: 1) examine the potential relationship between whitebark pine establishment and krummholz tree island formation at the upper alpine treeline ecotone in GTNP; 2) characterize blister rust infection rate and intensity at two treeline study areas and in whitebark pine growing both solitarily and within tree islands; and 3) characterize the biophysical environments a) where whitebark pine is/is not a majority tree island initiator, and b) with varying blister rust infection rates in treeline whitebark pine. In July 2015, we field-sampled treeline composition and blister rust infection in all krummholz whitebark pine in a total of 40 study plots. Preliminary results reveal: 1) that whitebark pine is a substantial component of treeline ecosystems, but is not a significant majority tree island initiator, and 2) blister rust infection levels for both study areas combined is 15.65%. Blister rust and mountain pine beetle interactions were not evident at the two study areas. This work provides important baseline measurements for understanding how community structure and composition may be altered given infestation by pathogens and pests in GTNP, especially in light of changing climate regimes.