Upland Species Research Articles

Short‐term survival and growth of 32 native boreal plants on treated oil sands tailings

AbstractThe consolidation of oil sands tailings is a cost‐ and time‐consuming process that requires treatment via active (e.g., centrifugation) and passive (e.g., self‐weight consolidation) methods. The use of plants to dewater tailings is a promising concept and has previously been evaluated using agronomic grass species in greenhouse studies. This greenhouse study evaluated the short‐term survivorship and growth of 32 upland and lowland native plant species (12 forbs, 14 graminoids, and six woody plants) in centrifuged tailings and benchmarked their performance against reclamation soil and undisturbed forest soil. All plant species were propagated from seed and transplanted as seedlings into containers filled with one of the three substrates. After 42 days, the height (woody species only) and total aboveground biomass were determined for all living plants. As expected, the mortality of seedlings in tailings was higher than plants grown in the other two substrates. Graminoid species, regardless of species community type (wetland or upland), had higher survival probabilities and growth compared to forb or woody species across all substrates. Of forbs and woody species evaluated, Geum aleppicum and Populus tremuloides showed the most promise amongst the upland species, and Rumex occidentalis was the wetland equivalent.

Exogenous abscisic acid induces the formation of a suberized barrier to radial oxygen loss in adventitious roots of barley (Hordeum vulgare).

Internal root aeration is essential for root growth in waterlogged conditions. Aerenchyma provides a path for oxygen to diffuse to the roots. In most wetland species, including rice, a barrier to radial oxygen loss (ROL) allows more of the oxygen to diffuse to the root tip, enabling root growth into anoxic soil. Most dryland crops, including barley, do not form a root ROL barrier. We previously found that abscisic acid (ABA) signalling is involved in the induction of ROL barrier formation in rice during waterlogging. Although rice typically does not form a tight ROL barrier in roots in aerated conditions, an ROL barrier with suberized exodermis was induced by application of exogenous ABA. Therefore, we hypothesized that ABA application could also trigger root ROL barrier formation with hypodermal suberization in barley. Formation of an ROL barrier was examined in roots in different exogenous ABA concentrations and at different time points using cylindrical electrodes and Methylene Blue staining. Additionally, we evaluated root porosity and observed suberin and lignin modification. Suberin, lignin and Casparian strips in the cell walls were observed by histochemical staining. We also evaluated the permeability of the apoplast to a tracer. Application of ABA induced suberization and ROL barrier formation in the adventitious roots of barley. The hypodermis also formed lignin-containing Casparian strips and a barrier to the infiltration of an apoplastic tracer (periodic acid). However, ABA application did not affect root porosity. Our results show that in artificial conditions, barley can induce the formation of ROL and apoplastic barriers in the outer part of roots if ABA is applied exogenously. The difference in ROL barrier inducibility between barley (an upland species) and rice (a wetland species) might be attributable to differences in ABA signalling in roots in response to waterlogging conditions.

Response of tree species in cypress (Taxodium spp.) domes of central Florida to a hydrologic gradient

Cypress domes are isolated wetlands dominated by cypress (Taxodium spp.) with multiple subdominant species. Although one of the most common wetlands in the southeastern United States, the number and extent of cypress domes are progressively declining. While tree communities must be resilient to survive both extended periods of flooding and desiccation associated with climate cycles, ongoing changes in land use and climate are altering hydrologic extremes and potentially exceeding the resilience of species. Upland species such as pines and oaks can increase in density in response to persistent shortened hydroperiod, while mature wetland trees including cypress and tupelo can persist for extended periods. This study investigated tree community structure in cypress domes across a gradient of hydroperiods and water depths potentially experienced by cypress domes with altered hydrology. Three decades of water level data were used to describe cypress dome tree community responses to long-term, chronic alterations to hydrology.The tree community structure of cypress dome was correlated with average annual hydroperiod and water depth, but maximum water depth was not significant. Nyssa sylvatica was correlated with extended hydroperiods/deeper water depths, while both Quercus laurifolia and Pinus elliottii correlated with reduced hydrology. The presence of cypress was not correlated with hydrology, presumably because of its dominance in all sample wetlands. Mature (>6 m) wetland trees remained dominant in all sample wetlands with non-wetland trees showing increased abundance when hydroperiods and water depths were below 3 months and 0.075 m, respectively. Sub-adult (<6 m) non-wetland trees became increasingly important when hydroperiods fell below 6 months and were dominant below 3 months. Wetland tree recruitment was reduced when hydroperiods were altered to less than three months and longer than nine months; and average water depths were altered to <0.075 m and>0.225 m. Our study indicates that cypress dome communities may not be as resilient as previously thought. The long-term persistence of cypress domes is not dependent on the ability of mature wetland trees to survive extended periods of flood and drought, but instead maintaining hydrology and recruitment of wetland trees. By utilizing a long-term hydrologic database, a tipping point for cypress domes was observed for water depth and duration of inundation, beyond which the long-term persistence of these systems is in jeopardy.

Ambient ozone – New threat to birds in mountain ecosystems?

Mountain ecosystems are inhabited by species with specific characteristics enabling survival at high altitudes, which make them at risk from various pressures. In order to study these pressures, birds represent excellent model organisms due to their high diversity and position at the top of food chains. The pressures upon mountain bird populations include climate change, human disturbance, land abandonment, and air pollution, whose impacts are little understood. Ambient ozone (O3) is one of the most important air pollutants occurring in elevated concentrations in mountain conditions. Although laboratory experiments and indirect course-scale evidence suggest its negative effects on birds, population-level impacts remain unknown. To fill this knowledge gap, we analysed a unique 25-years long time series of annual monitoring of bird populations conducted at fixed sites under constant effort in a Central European mountain range, the Giant Mountains, Czechia. We related annual population growth rates of 51 bird species to O3 concentrations measured during the breeding season and hypothesized (i) an overall negative relationship across all species, and (ii) more negative O3 effects at higher altitudes due to increasing O3 concentration along altitudinal gradient. After controlling for the influence of weather conditions on bird population growth rates, we found an indication of the overall negative effect of O3 concentration, but it was insignificant. However, the effect became stronger and significant when we performed a separate analysis of upland species occupying the alpine zone above treeline. In these species, populations growth rates were lower after the years experiencing higher O3 concentration indicating an adverse impact of O3 on bird breeding. This impact corresponds well to O3 behaviour and mountain bird ecology. Our study thus represents the first step towards mechanistic understanding of O3 impacts on animal populations in nature linking the experimental results with indirect indications at the country-level.

Preliminary evidence of upland plant encroachment in high‐elevation wetlands of Volcanoes National Park, Rwanda

AbstractWetland ecosystems are increasingly altered by anthropogenic activities, with upland plant encroachment as one possible outcome. Here, we present preliminary evidence that encroachment by herbaceous and woody upland species is ongoing in five small Afromontane wetlands straddling high elevations (~2600–3400 m a.s.l.) in Volcanoes National Park (Rwanda). Although encroachment seems to commence at wetland edges it reaches waterlogged soils at wetland centres. This evidence of the spread of upland plants in these wetlands should be followed by additional research efforts focused on possible causes and consequences of this encroachment as well as the exploration of potential management and mitigation efforts.

The climatic drivers of long-term population changes in rainforest montane birds.

Climate-driven biodiversity erosion is escalating at an alarming rate. The pressure imposed by climate change is exceptionally high in tropical ecosystems, where species adapted to narrow environmental ranges exhibit strong physiological constraints. Despite the observed detrimental effect of climate change on ecosystems at a global scale, our understanding of the extent to which multiple climatic drivers affect population dynamics is limited. Here, we disentangle the impact of different climatic stressors on 47 rainforest birds inhabiting the mountains of the Australian Wet Tropics using hierarchical population models. We estimate the effect of spatiotemporal changes in temperature, precipitation, heatwaves, droughts and cyclones on the population dynamics of rainforest birds between 2000 and 2016. We find a strong effect of warming and changes in rainfall patterns across the elevational-segregated bird communities, with lowland populations benefiting from increasing temperature and precipitation, while upland species show an inverse strong negative response to the same drivers. Additionally, we find a negative effect of heatwaves on lowland populations, a pattern associated with the observed distribution of these extreme events across elevations. In contrast, cyclones and droughts have a marginal effect on spatiotemporal changes in rainforest bird communities, suggesting a species-specific response unrelated to the elevational gradient. This study demonstrated the importance of unravelling the drivers of climate change impacts on population changes, providing significant insight into the mechanisms accelerating climate-induced biodiversity degradation.

Temperature, nutrient availability, and species traits interact to shape elevation responses of Australian tropical trees

Elevation gradients provide natural laboratories for investigating tropical tree ecophysiology in the context of climate warming. Previously observed trends with increasing elevation include decreasing stem diameter growth rates (GR), increasing leaf mass per area (LMA), higher root-to-shoot ratios (R:S), increasing leaf δ13C, and decreasing leaf δ15N. These patterns could be driven by decreases in temperature, lower soil nutrient availability, changes in species composition, or a combination thereof. We investigated whether these patterns hold within the genus Flindersia (Rutaceae) along an elevation gradient (0–1,600 m) in the Australian Wet Tropics. Flindersia species are relatively abundant and are important contributors to biomass in these forests. Next, we conducted a glasshouse experiment to better understand the effects of temperature, soil nutrient availability, and species on growth, biomass allocation, and leaf isotopic composition. In the field, GR and δ15N decreased, whereas LMA and δ13C increased with elevation, consistent with observations on other continents. Soil C:N ratio also increased and soil δ15N decreased with increasing elevation, consistent with decreasing nutrient availability. In the glasshouse, relative growth rates (RGR) of the two lowland Flindersia species responded more strongly to temperature than did those of the two upland species. Interestingly, leaf δ13C displayed an opposite relationship with temperature in the glasshouse compared with that observed in the field, indicating the importance of covarying drivers in the field. Leaf δ15N increased in nutrient-rich compared to nutrient-poor soil in the glasshouse, like the trend in the field. There was a significant interaction for δ15N between temperature and species; upland species showed a steeper increase in leaf δ15N with temperature than lowland species. This could indicate more flexibility in nitrogen acquisition in lowland compared to upland species with warming. The distinguishing feature of a mountaintop restricted Flindersia species in the glasshouse was a very high R:S ratio in nutrient-poor soil at low temperatures, conditions approximating the mountaintop environment. Our results suggest that species traits interact with temperature and nutrient availability to drive observed elevation patterns. Capturing this complexity in models will be challenging but is important for making realistic predictions of tropical tree responses to global warming.

Effects of hurricane canopy gaps on longleaf pine and upland oak sapling growth

Longleaf pine forests and woodlands are an ecologically important ecosystem that once dominated much of the southeastern U.S. Frequent fire is well-known to be a driver of forest dynamics in these systems, but far less is known about how wind disturbance may reorganize plant communities. To gain a better understanding of how hurricane impacts may alter dynamics in a second-growth longleaf pine woodland, we investigated growth response of saplings from three competing upland species (Pinus palustris, Quercus falcata, Q. margaretta) following Hurricane Michael (2018) in southwest Georgia, United States. We used maximum likelihood to model height and radial growth of saplings as species-specific Michaelis-Menten functions of light availability and examined the effect of sapling size, soil water holding capacity, and annual precipitation using a model comparison approach. The best model for both height and radial growth included species-specific growth rates, a power function for sapling size, and an effect of 2-year lagged precipitation. Overall, we found that height growth rate increased with irradiance for all species, but asymptotic height growth rate for all species was approached at low irradiance. Rates of radial growth also increased with irradiance and were more strongly differentiated among species. Radial growth in longleaf pine and southern red oak responded most strongly to increasing irradiance. Our findings suggest that increases in light availability from hurricanes has direct effects on altering growth dynamics of saplings. Further, because stem radius is a strong predictor of survival from surface fires, hurricane damage may also have an indirect effect on sapling dynamics, by altering survival in future fires. Our results suggest that hurricanes can reinforce the dominance of longleaf pine and potentially play a role in stabilizing community structure. Understanding the effects of common disturbances like wind and fire—together and individually—can reveal important mechanisms that shape the structure and function of fire-prone ecosystems.

Guiding Conservation for Mountain Tree Species in Lebanon

The objective of this study is to contribute to the conservation of upland tree species in the face of climate change. We used a conservation index to prioritize the areas and populations of three conifer species in the mountains of Lebanon. This conservation index integrates (1) mountain topography to identify areas that could provide a suitable microclimate, (2) genetic diversity to assess the adaptive capacity of populations in these mountain areas, and (3) a hypothetical climate change scenario that could affect this Mediterranean region. The idea of this index is to prioritize protected areas based on a match between the relevance of the area to be protected and the populations that need local and long-term protection. The stronger the match, the higher the priority of the area to be protected. We applied this conservation index to 36 populations of 15 fir, 15 cedar, and 6 juniper. These populations were genotyped by different authors whose published data we used. The results show that 10 populations of the 3 species have a very high index and 9 others have a lower but still high index, indicating a high conservation priority. These 19 populations occur in 5 different areas that we delineated and that form a network along the Lebanon Mountains. We hypothesize that the conservation of these 19 populations across the Lebanon Mountains could contribute to the long-term sustainability of the 3 species in the face of a 2 °C increase in mean seasonal temperature and a 20% decrease in seasonal precipitation compared to the current climate.

Estimating the aboveground biomass and carbon stocks of tall shrubs in a prerestoration degraded salt marsh

Wetlands play a vital role in Earth's carbon cycle and provide important ecosystem services. Their ability to perform their roles can be compromised by human activities that destroy or impair their functioning. The restoration of degraded wetlands may allow carbon cycle functioning, as well as other services, to be recovered. Predicting the potential outcomes from any restoration project requires upfront consideration, including via modeling possible changes in carbon stocks. In this study, we quantified the carbon stocks in tall shrub vegetation proliferating in a degraded salt marsh that is currently the subject of an extensive restoration project. We produced allometric models to estimate biomass and carbon stocks for three tall shrub species, which, along with other freshwater and upland species in the area, will die with continued restoration. Therefore, estimating the potential for carbon losses in biomass is important. We also developed a means of estimating carbon stocks in other nontree plants in the estuary area. Useful equations for estimating the biomass of tall shrubs are limited in general and lacking for degraded systems. Our study adds to the literature on carbon stocks in shrub species and fills a data gap for degraded ecosystems. It also contributes to the broader carbon feasibility study of the aforementioned restoration project that was designed to predict the overall net impact of the project on greenhouse gas emissions in the ecosystem.

Predicted alteration of vertebrate communities in response to climate‐induced elevational shifts

AbstractAimClimate change is driving species to migrate to novel areas as current environments become unsuitable. As a result, species distributions have shifted uphill in montane ecosystems globally. Heterogeneous dispersal rates among shifting species could result in complex changes to community assemblages. For example, interspecific differences in dispersal ability could lead to the disruption, or creation, of species interactions and processes within communities, likely amplifying the impact of climate change on ecosystems. Here, we studied the dispersal success of vertebrate species in a tropical montane ecosystem under a climate‐induced uphill shift and assessed the derived impacts on community structures.LocationThe Australian Wet Tropics bioregion.MethodWe simulated the uphill shift of 7613 community assemblages across the elevational gradient using thermal resistance layers for movement analyses. Dispersal success was calculated as the probability of shifting given species’ dispersal ability and landscape composition. We then used dissimilarity indices to measure the potential changes in community structures resulting from the heterogeneous dispersal success among migrating species.ResultsDispersal success was strongly influenced by species’ dispersal ability, landscape composition and climate change. The heterogeneous dispersal success among migrating species induced marked temporal changes between community assemblages along the elevational gradient. The local extinction rate (i.e. the proportion of species unable to shift) was especially remarkable at high elevations, suggesting potential mass local extinctions of upland species. Furthermore, the increasing local extinction rate with elevation resulted in substantial declines in species co‐occurrence in high‐altitude ecosystems.Main conclusionsOur study highlights the escalating impact of climate change on community assemblages in response to climate‐induced elevational shifts, providing a classic example of the "escalator to extinction." Future predictions of the impacts of climate change on ecosystems will benefit from improvements in understanding species interactions, population dynamics and species potential to adapt to a changing environment.

Sexual reproduction is light-limited as marsh grasses colonize maritime forest.

Climate change is driving abiotic shifts that can threaten the conservation of foundation species and the habitats they support. Directional range shifting is one mechanism of escape, but requires the successful colonization of habitats where interspecific interactions may differ from those to which a species has adapted. For plants with multiple reproductive strategies, these range-edge interactions may alter the investment or allocation toward a given reproductive strategy. In this study, we quantified sexual reproduction of the clonal marsh grass Spartina patens across an inland colonization front into maritime forest being driven by sea-level rise. We find that flowering is variable across S. patens meadows, but consistently reduced in low light conditions like those of the forest understory. Observational surveys of S. patens flowering at four sites in the Delmarva Peninsula agreed with the results of two experimental manipulations of light availability (shading experiment in S. patens-dominated marsh and a forest dieback manipulation). These three approaches pinpointed light limitation as a principal control on S. patens flowering capacity, suggesting that light competition with taller upland species can suppress S. patens flowering along its upland migration front. Consequently, all propagation in shaded conditions must occur clonally or via seeds from the marsh, a reproductive restriction that could limit the potential for local adaptation and reduce genetic diversity. Future research is needed to determine whether the lack of flowering is the result of a trade-off between sexual and clonal reproduction or results from insufficient photosynthetic products needed to achieve either reproductive method.

Why may the same species have different elevational ranges at different sites in New Guinea?

Species in mountainous areas have characteristic elevational ranges, but with some variation from site to site. Such variation has been studied extensively elsewhere in the world, but not yet for New Guinea bird species. Hence, we examined five sources of that variation for New Guinea birds: latitude, competition, slope, the Massenerhebung effect, and physical barriers. Decreases of species elevational ranges with latitude are illustrated by three sets of examples: 20 species confined to New Guinea's mountains, but which descend to sea level at higher latitudes in Australia (joined to New Guinea at Pleistocene times of low sea level); 13 sea-level populations of some of the same New Guinea upland species on New Guinea's Fly River bulge; and 11 populations on the Aru Islands (part of Pleistocene New Guinea and Australia). Many New Guinea species contract or expand their elevational ranges, associated with the presence or absence of competing congenerics, which segregate by elevation at sites of sympatry. The flat Karimui Basin at an elevation of 1,110 m illustrates effects of slope, because the basin supports populations of many species otherwise characteristic of the flat lowlands, and lacks populations of many hill forest species characteristic of the sloping terrain found at that elevation elsewhere in New Guinea. We provide three sets of New Guinea examples of the Massenerhebung effect described for mountains elsewhere in the world: shifts of species to higher elevations on large high mountains far from the sea than on small coastal mountains or isolated mountains. Finally, we suggest that very steep high ridges boxing in a watershed on the Foja Mts. constitute dispersal barriers that have prevented 33 species expected at that watershed's elevation from arriving or establishing themselves.

Drivers of change in mountain and upland bird populations in Europe

Mountain ecosystems have special significance for biodiversity and are vulnerable to climate and other environmental changes. However, few assessments of drivers of change have been conducted in these areas in comparison to other more accessible biomes. In this study, we developed an objective and broad definition of a mountain bird, and systematically reviewed the existing literature for the 34 European mountain and upland species identified in order to quantify which drivers of environmental change have been most consistently associated with positive or negative demographic responses. Raptors and gamebirds were the most‐studied species, whereas mountain specialists and arctic–alpine species were little studied. Using a standardized threat classification, the analyses reported significant negative impacts of hunting, collision with energy‐generation infrastructures, predation by competitive species, human disturbance and poisoning. There were significant positive effects for management of non‐target species, but less support for effects of drivers operating over longer timescales, such as climate and land‐use changes. Analysis of trends in drivers found evidence of increasing temperatures and vegetation encroachment, whereas agricultural impacts decreased, which was largely related to abandonment of grazing. A lack of fine‐grained studies investigating ecological mechanisms and population responses to widespread impacts were highlighted. We have found that some drivers are well studied, but we need to collect more detailed and longer‐term data on species requirements and on the impacts that bird populations face to devise priorities for conservation action and research for mountain and upland birds.

Ecological impacts of shortening fire return intervals on boreal peatlands and transition zones using integrated in situ field sampling and lidar approaches

AbstractAridity associated with rising air temperatures in northern latitudes is expected to contribute to increased frequency of wildland fires. Here, we examined regenerating vegetation following short return interval (SRI) fire (56 years post‐fire) compared to long return interval (LRI) fire (&gt;80 years post‐fire) in boreal peatlands and their adjacent transitional areas. The objectives of this study were to quantify if differences exist between (1) peatland and transitional soil characteristics in LRI versus SRI areas and (2) regenerating vegetation species, structural characteristics and diversity. We also determined if patterns of vegetation structural characteristics observed using field data also occur across the broader landscape using airborne lidar data. The Utikuma Region Study Area (URSA) is located in central Alberta, Canada. Here, 19 peatlands were sampled, coincident with an airborne lidar survey of the broader region, where 120 peatlands in short and long fire return intervals were identified. We found that SRI transitional areas had significantly deeper organic soil deposits than those found in LRI (p &lt; 0.0001). Proportions of regenerating species differed significantly between peatlands and transitional areas in SRI versus LRI, where greater proportion of coniferous species were observed in LRI. Deciduous transitional–upland species and taller post‐fire vegetation heights were more commonly found SRI peatlands compared with LRI. This suggest that fires with SRIs in this region may result in enhanced deciduous succession, which may transition boreal peatlands into ecosystems that have some characteristics of transitional and upland forests.

Temperature and soils predict the distribution of plant species along the Himalayan elevational gradient

AbstractTropical montane systems are characterized by a high plant species diversity and complex environmental gradients. Climate warming may force species to track suitable climatic conditions and shift their distribution upward, which may be particularly problematic for species with narrow elevational ranges. To better understand the fate of montane plant species in the face of climate change, we evaluated a) which environmental factors best predict the distribution of 277 plant species along the Himalayan elevational gradient in Nepal, and b) whether species elevational ranges increase with increasing elevation. To this end, we developed ecological niche models using MaxEnt by combining species survey and presence data with 19 environmental predictors. Key environmental factors that best predicted the distribution of Himalayan plant species were mean annual temperature (for 54.5% of the species) followed by soil clay content (10.2%) and slope (9.4%). Although temperature is the best predictor, it is associated with many other covariates that may explain species distribution, such as irradiance and potential evapotranspiration. Species at both ends of the Himalayan elevational gradient had narrower elevational ranges than species in the middle. Our results suggest that with further global warming, most Himalayan plant species have to migrate upward, which is especially critical for upland species with narrow distribution ranges.

Avifauna of the Van Rees Mountains, New Guinea

We describe results of the first ornithological exploration of the uplands of the Van Rees Mts., the lowest of New Guinea's ten outlying mountain ranges. The narrow Mamberamo River gorge separates them from the higher and more species-rich Foja Mts. The known avifauna of Van Rees comprises 223 species, of which 17 are winter visitors from Australia or the Palearctic (occurring overwhelmingly in open non-forest habitats), and 37 are upland species. Whilst most of the Van Rees upland species occur in the Foja Mts., conversely most Foja upland species are unrecorded from Van Rees. Of course, upland species whose Foja elevational floors lie above the Van Rees summit are predictably absent from the latter. However, there are also many ‘flagrant absentees’ from Van Rees—i.e., conspicuous or abundant Foja species that could or ‘should’ occur in Van Rees because their Foja floors lie well below the Van Rees summit. The percentage of Foja upland species occurring in Van Rees increases with decreasing Foja floor elevation. That is, availability of elevationally suitable habitat does not provide an all-or-nothing explanation, but only increases the probability, of upland species success in colonising Van Rees. Our Van Rees records of non-forest species at natural clearings in forest—landslides, mud volcanoes, streams and lakes—illustrate how the region’s endemic non-forest bird species may have evolved, despite forest being the climax vegetation over most of New Guinea. The lake Danau Bira and its surrounding marsh, created by a mud volcano damming a stream, support at least 23 water and marsh species. An appendix summarises records and elevational ranges of all 223 species recorded in the Van Rees Mts.

Characterizing past fire occurrence in longleaf pine ecosystems with the Mid-Infrared Burn Index and a Random Forest classifier

Prior to European settlement the longleaf pine (Pinus palustris) ecosystem covered over 92 million hectares in the southeastern United States. Historically, fire was an important driver of species composition in the longleaf pine ecosystem, but fire exclusion since the early 20th century has led to the degradation of longleaf pine communities and has had a detrimental effect on the large number of rare and endemic species found within this system. Thus, accurate estimates of fire history are important for better informed management of longleaf pine communities. Recently, satellite imagery has been used to identify burned areas. However, results have been inconsistent across physiographic regions and vegetation types (e.g. wetlands under high canopy). We developed a model using Landsat satellite imagery, coupled with a Random Forest (RF) machine learning algorithm, to identify burned areas and estimate the fire history from 1991 to 2019 for Fort Bragg, NC, one of the largest contiguous areas of longleaf pine ecosystem remaining. We calculated six spectral indices from the Landsat band values, including the Mid-Infrared Burn Index (MIRBI) and the change in MIRBI through time (ΔMIRBI), and used them as predictors in our RF model. We used the developed RF model to estimate the fire history for all known populations of 24 rare upland and wetland plant species found on Fort Bragg. We compared our results to a recent continental U.S. fire occurrence dataset, as well as the prescribed fire records from Fort Bragg. The overall AUC (area under the curve) for our RF model (0.74) compared favorably to the continental U.S. dataset results for Fort Bragg (0.69), and was able to capture the reduced fire frequency in wetlands. The most important predictor in our RF model was ΔMIRBI. Depending on the model, individual plant species were estimated to have experienced significant differences in fire frequency relative to the prescribed fire records. For our RF model, we estimated that 50% of wetland and 25% of upland species experienced a lower fire frequency relative to that represented in the prescribed fire records. The burn probability and classification tool generated in this paper provides land managers in the southeastern U.S. with a novel approach for accurately identifying burned areas and estimating local fire frequency across landscapes.

Evidence of Range Shifts in Riparian Plant Assemblages in Response to Multidecadal Streamflow Declines

Riparian corridors are thought to form hydrological refugia that may buffer species and communities against regional climate changes. In regions facing a warming and drying climate, however, the hydrological regime driving riparian communities is also under threat. We examined recruitment in response to streamflow declines for species inhabiting the riparian zone in southwest Western Australia, testing the extent to which the riparian system has buffered riparian communities from the drying climate. We stratified 49 vegetation transects across the &amp;gt;600 mm per annum regional rainfall gradient encompassed by the Warren River Catchment. Local hydrological conditions were estimated over two 10-year periods; 1980–1989, and 2001–2010, to quantify changes in the flood regime. Mixed effects models tested the relationship between rainfall and flooding on the relative frequency of immature to mature individuals of 17 species of trees and shrubs common to the riparian zones. At the low-rainfall extent of their geographic range, the relative frequency of immature riparian species decreased with declining flow, whereas at the high-rainfall extent of their geographic range the relative frequency of immature individuals increased with declining flow. These results suggest that the geographic ranges of riparian species may be contracting at the low-rainfall margin of their range, while at the high-rainfall margin of their geographic range, reduced flooding regimes appear to be opening up new habitat suitable for recruitment and narrowing the river corridor. No such patterns were observed in upland species, suggesting the river may be buffering upland species. We discuss these findings and their implications for ongoing management and species conservation in a region projected to face further, significant rainfall declines.

Disparate origins for endemic bird taxa from the ‘Gondwana Rainforests’ of Central Eastern Australia

Abstract Subtropical and temperate rainforests of Central Eastern Australia are some of the largest remaining fragments of their kind globally. The biota of these rainforests appears to comprise two broad biogeographical elements: a more ancient (Miocene or older) and typically upland temperate (‘Gondwanan’) element and a younger (Plio-Pleistocene) lowland tropical element. We present the first phylogenetic synthesis of the spatiotemporal origins for the eight bird taxa endemic to Central Eastern Australian Rainforests. At least five of these eight focal taxa show Plio-Pleistocene divergences from their respective northern sister taxa, consistent with origins driven by recent expansion and contraction of lowland rainforest. In contrast, two more strictly upland species, the rufous scrub-bird (Atrichornis rufescens) and the logrunner (Orthonyx temminckii), diverged from their nearest living relatives during the Miocene, suggesting potentially longer histories of persistence and more temperate origins. Finally, we did not recover reciprocal monophyly in mitogenomes from the two extant lyrebirds, Albert’s lyrebird (Menura alberti) and the superb lyrebird (Menura novaehollandiae). The disparate divergence ages recovered among all eight taxa are consistent with the biota of the Central Eastern Australian Rainforests comprising isolates either of younger age and tropical lowland origins or of older age and temperate upland origins.