Biology subjects

Branoff, B.

Publications and source records attributed to Branoff, B..

6 recordsLinked to original sources

bioRxiv2025

Evaluating tree biomass estimation in trans-Atlantic mangrove species: comparing bole diameter measurements for improved accuracy

Estimating the biomass of terrestrial forests generally, and mangrove forests in particular, is an area of considerable interest. Most approaches rely on empirically derived allometric models to predict tree biomass. The single parameter with the strongest predictive ability in most studies is diameter at breast height (DBH), however the use of DBH arose primarily out of convenience, not from an analysis of tree form. While DBH explains a lot of variability in other tree metrics such as height or above ground biomass, its utility in smaller species is uncertain. Here we used measurements from 302 destructively sampled mangrove trees of four species to test which of three bole diameter measurements, basal stem diameter (BSD), diameter at 30 cm (D30), and DBH, is the best predictor of above ground biomass. D30 had the highest mean coefficient of determination (R2) and lowest mean root mean squared error (RMSE) across all site/species combinations. However, the improvement over DBH was modest, with a mean across all site/species combinations of 1.58 kg RMSE and R2 of 0.948 for D30, compared to 1.63 kg RMSE and R2 of 0.917 for DBH. Nevertheless, D30 may have utility in future studies as it allows for lower size thresholds and has better overall explanatory power than DBH.

plant biology↗

bioRxiv2024

Partitioning biota along the Elbe River estuary: where are the community transitions?

Estuarine zonation and community assemblages are frequently correlated with salinity, although the extent or nature of this correlation varies considerably among the published studies. While a smooth transition in biological communities is often conceptualized in association with estuarine fresh, brackish, and marine conditions, many studies have shown more distinct communities and the altogether absence of a brackish community. We explore these viewpoints in light of plant observations and soil and aquatic microbial analyses from permanent plots established on the Elbe River Estuary of northern Germany. Generally, two distinct communities were observed, a polyhaline assemblage towards the mouth of the system, and another that was associated with both the fresh and brackish mesohaline regimes further upriver. This was most pronounced among plant and soil bacteria communities, while aquatic 16S assemblages reflected little distinction at all. The proportion of marine classified taxa declined from the mouth to upriver and suggests that while the transition from marine to brackish or fresh vegetation falls within the sampled area, the same transition for microbial taxa could not be observed and may be further upriver. Thus, although we were able to identify two distinct communities, the "limit" of marine taxa was only evident for vegetation. While tidal and weather-related hydrology, as well as soil properties were also influential in distinguishing the communities, much of the variance remains unexplained. Further sampling, classification, and partitioning is necessary to determine the origin and/or autochthonous habitat, if any, for the Elbe River estuarine taxa. Geographic boundsbottom left: 53.556216{degrees}N, 8.824398{degrees}E top right: 53.917760 {degrees}N, 10.155669 {degrees}E

ecology↗

bioRxiv2018

Urbanization drives the acoustic diversity of mangrove anurans and avifauna in Puerto Rico

The mangroves of Puerto Rico occupy a broad gradient of urbanization that offers a chance to test hypotheses on urban faunal communities from both terrestrial and mangrove systems. These hypotheses state that urban avifaunal communities are less diverse, with greater representation by generalists, but that certain mangrove specialists can utilize urban landscapes. Much of this is said to be driven by food resources, with frugivores and nectarivores benefiting from abundant residential flowers and fruits, while insectivores are driven away by low food resources. This study used passive acoustic monitoring to identify the audible anuran and avifaunal species in mangroves across the urban gradient of Puerto Rico. Three anurans and twenty-four avian species were detected across all sites, with eighteen species found at the most diverse site, and six at the least diverse site. The most urban communities were more similar to each other and characterized by low diversity, especially of invertivores, mangrove specialists, and endemics. The least urban communities, however, were less like each other and more diverse than their more urban counterparts. Greater surrounding vegetation cover was the strongest overall predictor of increased faunal diversity, although urban coverage and population density were also strongly correlated with some guilds and species. Soundscape analyses showed that acoustic space use was a strong predictor of site diversity and is thus a sufficiently accurate faster alternative to detecting individual species. This will be an important tool in the continued monitoring of these forests, which may experience changes associated with ongoing urbanization and sea-level rise.

ecology↗

bioRxiv2018

Mangrove leaf and root traits and their relation to urbanization

Root and leaf traits are one means of understanding plant ecophysiological responses to environmental variation and disturbance. In mangroves, both chemical and morphological variations have been recorded in response to changes in inundation, salinity, and nutrient levels. Some have also been noted in urban environments, primarily in response to elevated nutrients and toxic substances. Yet these studies have not attempted to isolate the urban from the non-urban influences on both morphological and chemical traits. This study measured mangrove leaf and root chemical and morphological traits in herbarium samples and in field collected leaves and roots along a quantified urban gradient in three watersheds of Puerto Rico. It then correlated these traits with predictors of surrounding land cover, as well as with metrics of flooding and water chemistry. There were significant lines of evidence leading to an influence of urban sewage and roads on leaf and root traits. Leaf percent nitrogen increased with urbanization and with surface water nitrogen and phosphorus concentrations, but its isotopic content decreased with increasing phosphorus, leading to the hypothesis that both nitrogen and phosphorus are fueling an otherwise co-limited community of mangroves and nitrogen fixing microbes. The most urban site harbored some of the highest metal concentrations, and there was evidence that elevated concentrations primarily influence fine roots. Other morphological traits are more likely explained by both water chemistry and leaf chemistry and should be considered when interpreting the influence of urban landscapes on mangroves. Percent nitrogen in herbarium samples increased at the least urban site, but remained unchanged at the most urban site, reflecting the relative levels of urbanization at the time of the first samples and their subsequent changes. Most metals from herbarium samples decreased or remained unchanged, suggesting regulation and infrastructure have helped to reduce the release of trace metals to the estuaries. Understanding the influence of urbanization in the context of water chemistry and flooding dynamics will aid in the management of these systems as global urbanization continues.

ecology↗

bioRxiv2018

Mangrove forest structure and composition along urban gradients in Puerto Rico

Urban forests are repeatedly characterized as distinct in composition and structure in comparison with their non-urban counterparts. This holds true for mangroves, although previous studies lack quantified representations of urbanness as well as any inclusion of hydrology or water chemistry, which are important influences on mangrove forest structure, composition, and function. This study uses LiDAR and ground-based measurements of mangroves within well quantified urban gradients in Puerto Rico to test for the relative importance of urbanization alongside flooding metrics and surface water chemistry in explaining observed patterns of forest structure and composition. In simple regression, urban metrics were the most powerful predictors of forest composition but not structure. Results show higher tree diversity but lower mangrove diversity in the most urban forests. Structural measurements, however, were best explained by flooding, surface water chemistry, and non-urban land cover metrics. Nitrogen concentrations best explained stem density and tree size, while flooding metrics best explained stand biomass and basal area, and surrounding vegetation cover best explained canopy cover and height metrics. In multiple regression, land cover and surface water chemistry were more important than flooding, with population density again being the most important variable in explaining mangrove forest diversity. Results show that urbanization is an important influence on mangrove composition and basal area, leading to higher tree diversity and lower basal area, consistent with patterns in terrestrial forests. But urban mangrove forests are also lower in mangrove diversity and tend to have representation only by Laguncularia racemosa. Nitrogen concentrations and surrounding vegetation cover, both of which are indirectly influenced by urbanization, were positively related to tree size and canopy cover and height, respectively. These tests suggest urbanization is an important influence on mangrove forest structure and composition, but that flooding and water chemistry must also be considered when managing these forests.

ecology↗

bioRxiv2018

Changes in mangrove tree mortality, forest canopy, and aboveground biomass accumulation rates following the 2017 hurricane season in Puerto Rico and the role of urbanization

Mangrove ecosystem responses to tropical cyclones have been well documented over the last half a century, resulting in repeated measures of tree mortality, aboveground biomass reduction, and recovery by species, size, and geomorphology. However, no studies have investigated the role of urbanization in mangrove hurricane resistance and resilience, despite increasing urbanization of tropical shorelines. This study gauges the initial response and short-term recovery of Puerto Ricos mangroves along well defined and quantified urban gradients following the 2017 hurricane season. Survival probability of tagged trees decreased with time, and the mean mortality across all sites was 22% after eleven months. Mean canopy closure loss was 51% one month after the hurricanes, and closure rates also decreased with time following the storms. Aboveground biomass accumulation decreased by 3.5 kg yr-1 per tree, corresponding to a reduction of 4.5 Mg ha-1 yr-1 at the stand level. One year later, the mangroves have recovered to 72% canopy closure and to nearly 60% of their pre-storm growth rates. No connection to urbanization could be detected in the measured dynamics. Instead, species, size and geomorphology were found to play a role. Larger trees suffered 25% more mortality than smaller size classes, and Laguncularia racemosa suffered 11% less mortality than other species. Hydro-geomorphology was also found to play a role, with forests in tidally restricted canals experiencing more canopy loss but faster recovery than open embayment systems. These findings suggest size, species, and geomorphology are important in mangrove resistance and resilience to tropical storms, and that urbanization does not play a role. Managing mangrove ecosystems for optimal shoreline protection will depend upon knowing which forests are at greatest risk in a future of increasing urbanization.

ecology↗