Environmental determinants and controls of skin color change in neotropical anurans

Physiological color change is a strategy present in many groups of vertebrates and invertebrates. Animals showing this behavior have become model taxa in the study of camouflage because they are able to respond dynamically to changes in the environment. A number of studies have looked at the ability of amphibians to change skin coloration, in a phenomena known as physiological color change. In the physiological response, dermal pigment-containing cells rapidly react by modifying the distribution of pigments. Environmental factors such as light intensity and background color have been known to be very important cues on amphibian physiological color change, but the ecological function of these changes, in the context of a changing environment, is still unclear. Additionally, due to the presence of visual pigments in chromatophores, amphibians can aggregate or disperse pigments in specific areas of the skin, as a direct response to changes in the intensity of light; response that raises new questions about the benefits and drawbacks than an (visually) uncontrolled change might have on anuran ecology. However, studies have been limited to early stages. This study investigates how environmental factors affect color change in anurans and to what extent these changes are controlled by the individual. First, I present a review of the importance of coloration for anuran ecology and discuss the current issues dealing with color change experiments (Chapter I). Then, I present the results of the first experiment, in which I tested the ability of the Panamanian frogs Gastrotheca cornuta and Strabomantis bufoniformis to change skin coloration in response to light intensity and background coloration (Chapter II). I show that both species respond to changes in light and background color, but there are interspecific differences, probably due to the species-specific habitat characteristics (i.e. Forest canopy and floor respectively). Then, in a second experiment on Hypsiboas rosenbergi adults, I demonstrate the ability to change skin coloration as a direct, visually uncontrolled and localized response to light. These findings suggest that changes in adult frog skin coloration play an important role in camouflage and thermoregulation, and give a key, yet missing, component in understanding the behavioral and evolutionary implications of color change in animals

Tree Species Effects on Soil C Dynamics in Temperate Forests

Terrestrial ecosystems account for two-fifths of the total exchange of CO2 between the earth and the atmosphere, with forests contributing 80% of that exchange. Forest biomass and forest soils are particularly important carbon (C) sinks, however forest soil C stocks can vary widely, depending on the dominant tree species. Species specific differences in the quality and quantity of plant litter inputs can influence soil C dynamics and storage because they control decomposition processes, altering soil respiration and soil properties. However, our knowledge of how tree species identity influences the interactions between decomposition processes, soil C dynamics and soil C storage is still deficient. Resolving this knowledge gap is important to determine how tree species selection for afforestation might help us increase soil C sequestration and mitigate the effects of climate change. Using microcosm experiments and in situ mesocosms, I studied interactions between litter quality and soil properties for different temperate tree species in the UK. I measured key litter properties, and quantified the effect of litter quality and quantity on soil CO2 efflux and soil properties. My results show that litter quality, represented by nitrogen and lignin content, plays a major role in regulating soil C dynamics via litter decomposition. Litter quality also modified changes in soil CO2 efflux in response to altered litter inputs but the effect varied strongly by species. Using reciprocal transplant experiments in single species stands of alder, oak, and pine, I demonstrate variable influences of litter quality and the ‘home field advantage’ on decomposition and soil CO2 efflux. The present work provides an insight into the linkages between litter quality, decomposition and soil respiration in temperate forests. My results represent an important first step in identifying the future role of different tree species on soil C dynamics under climate change, which could inform forestry rotation and reforestation practices

The Automated Root Exudate System (ARES): a method to apply solutes at regular intervals to soils in the field.

Root exudation is a key component of nutrient and carbon dynamics in terrestrial ecosystems. Exudation rates vary widely by plant species and environmental conditions, but our understanding of how root exudates affect soil functioning is incomplete, in part because there are few viable methods to manipulate root exudates in situ. To address this, we devised the Automated Root Exudate System (ARES), which simulates increased root exudation by applying small amounts of labile solutes at regular intervals in the field. The ARES is a gravity-fed drip irrigation system comprising a reservoir bottle connected via a timer to a micro-hose irrigation grid covering c. 1 m2; 24 drip-tips are inserted into the soil to 4-cm depth to apply solutions into the rooting zone. We installed two ARES subplots within existing litter removal and control plots in a temperate deciduous woodland. We applied either an artificial root exudate solution (RE) or a procedural control solution (CP) to each subplot for 1 min day-1 during two growing seasons. To investigate the influence of root exudation on soil carbon dynamics, we measured soil respiration monthly and soil microbial biomass at the end of each growing season. The ARES applied the solutions at a rate of c. 2 L m-2 week-1 without significantly increasing soil water content. The application of RE solution had a clear effect on soil carbon dynamics, but the response varied by litter treatment. Across two growing seasons, soil respiration was 25% higher in RE compared to CP subplots in the litter removal treatment, but not in the control plots. By contrast, we observed a significant increase in microbial biomass carbon (33%) and nitrogen (26%) in RE subplots in the control litter treatment. The ARES is an effective, low-cost method to apply experimental solutions directly into the rooting zone in the field. The installation of the systems entails minimal disturbance to the soil and little maintenance is required. Although we used ARES to apply root exudate solution, the method can be used to apply many other treatments involving solute inputs at regular intervals in a wide range of ecosystems

Recruitment limitation in three large‐seeded plant species in a tropical moist forest

Recruitment limitation—the failure of a species to establish recruits at an available site—is a potential determinant of plant communities’ structure, causing local communities to be a limited subset of the regional species pool. Recruitment limitation results from three mechanisms: (i) lack of seed sources (i.e., source limitation), (ii) failure of available seeds to reach recruitment sites (i.e., dispersal limitation), and (iii) failure of arrived seeds to establish at a location (i.e., establishment limitation). Here, we evaluated the relative importance of these mechanisms in three co-occurring tree species (Dipteryx oleifera, Attalea butyracea, and Astrocaryum standleyanum) that share seed dispersers/predators. The study was set up on Barro Colorado Island (Panama) at 62 one-ha sites with varying tree densities. Source limitation was estimated as the proportion of sites that would be reached by seeds if seeds were distributed uniformly. Dispersal limitation was estimated from the number of sites with seeds in the soil bank. Establishment limitation was evaluated by measuring germination and 1-year survival in seed addition experiments. The effect of conspecific and heterospecific densities on the mechanisms was evaluated at three spatial scales (1, 5, and 9 ha). For all species, seed predation was the most important recruitment component (~80% decrease in seed survival). Establishment varied among species and was affected by conspecific and heterospecific species densities across spatial scales. Given that species identity, distribution, and seed dispersal/predation affect recruitment at multiple scales, multiscale studies are required to understand how recruitment limitation determines community structure in tropical forests

Evolving trends in the management of acute appendicitis during COVID-19 waves. The ACIE appy II study

Background: In 2020, ACIE Appy study showed that COVID-19 pandemic heavily affected the management of patients with acute appendicitis (AA) worldwide, with an increased rate of non-operative management (NOM) strategies and a trend toward open surgery due to concern of virus transmission by laparoscopy and controversial recommendations on this issue. The aim of this study was to survey again the same group of surgeons to assess if any difference in management attitudes of AA had occurred in the later stages of the outbreak. Methods: From August 15 to September 30, 2021, an online questionnaire was sent to all 709 participants of the ACIE Appy study. The questionnaire included questions on personal protective equipment (PPE), local policies and screening for SARS-CoV-2 infection, NOM, surgical approach and disease presentations in 2021. The results were compared with the results from the previous study. Results: A total of 476 answers were collected (response rate 67.1%). Screening policies were significatively improved with most patients screened regardless of symptoms (89.5% vs. 37.4%) with PCR and antigenic test as the preferred test (74.1% vs. 26.3%). More patients tested positive before surgery and commercial systems were the preferred ones to filter smoke plumes during laparoscopy. Laparoscopic appendicectomy was the first option in the treatment of AA, with a declined use of NOM. Conclusion: Management of AA has improved in the last waves of pandemic. Increased evidence regarding SARS-COV-2 infection along with a timely healthcare systems response has been translated into tailored attitudes and a better care for patients with AA worldwide

Data from: The Automated Root Exudate System (ARES): a method to apply solutes at regular intervals to soils in the field

1) Root exudation is a key component of nutrient and carbon dynamics in terrestrial ecosystems. Exudation rates vary widely by plant species and environmental conditions but our understanding of how root exudates affect soil functioning is incomplete, in part because there are few viable methods to manipulate root exudates in situ. To address this, we devised the Automated Root Exudate System (ARES), which simulates increased root exudation by applying small amounts of labile solutes at regular intervals in the field. 2) The ARES is a gravity-fed drip irrigation system comprising a reservoir bottle connected via a timer to a micro-hose irrigation grid covering c. 1 m2; 24 drip-tips are inserted into the soil to 4-cm depth to apply solutions into the rooting zone. We installed two ARES subplots within existing litter removal and control plots in a temperate deciduous woodland. We applied either an artificial root exudate solution (RE) or a procedural control solution (CP) to each subplot for 1 min d-1 during two growing seasons. To investigate the influence of root exudation on soil carbon dynamics, we measured soil respiration monthly and soil microbial biomass at the end of each growing season. 3) The ARES applied the solutions at a rate of c. 2 L m-2 wk-1 without significantly increasing soil water content. The application of RE solution had a clear effect on soil carbon dynamics but the response varied by litter treatment. Across two growing seasons, soil respiration was 25% higher in RE compared to CP subplots in the litter removal treatment, but not in the control plots. By contrast, we observed a significant increase in microbial biomass carbon (33%) and nitrogen (26%) in RE subplots in the control litter treatment. 4) The ARES is an effective, low-cost method to apply experimental solutions directly into the rooting zone in the field. The installation of the systems entails minimal disturbance to the soil and little maintenance is required. Although we used ARES to apply root exudate solution, the method can be used to apply many other treatments involving solute inputs at regular intervals in a wide range of ecosystems

ARES soil variables

This dataset describes soil variables (0-10-cm depth) measured in subplots with daily applications of root exudate solution (RE) or a procedural control solution (CP), applied using the Automated Root Exudate System (ARES) within experimental litter removal (0L) and control plots (1L) in an old-growth deciduous woodland in Wytham, Oxfordshire, UK. Full descriptions of the study site and experimental design are given in the paper and appendices. Data included in this file are: soil water content, soil pH and microbial biomass carbon and nitrogen measured in the subplots at the end of the growing season in the first and second year of treatments (September 2015 and 2016) as well as fine root biomass in the second year of the study (July 2016). Column headings and abbreviations are as follows: block = replicate block A-E; Plot = unique experimental plot identifier P1-P15; treatm = litter manipulation treatment, where 0L is litter removal and 1L is control; ARES = subplot treatment, where RE is root exudate solution and CP is procedural control; year = year of study; swc = gravimetric soil water content in %; pH = soil pH; MBC and MBN = microbial biomass carbon and nitrogen, respectively, in ug g-1; fine.roots = fine root biomass in g m-2

ARES soil respiration data

This dataset describes monthly measurements of soil CO2 efflux, soil water content, and soil temperature in subplots with daily applications of root exudate solution (RE) or a procedural control solution (CP), applied using the Automated Root Exudate System (ARES) within experimental litter removal (0L) and control plots (1L) in an old-growth deciduous woodland in Wytham, Oxfordshire UK. Full descriptions of the study site and experimental design are given in the paper and appendices. Column headings and abbreviations are as follows: block = replicate block A-E; Plot = unique experimental plot identifier P1-P15; treatm = litter manipulation treatment, where 0L is litter removal and CT is control; ARES = subplot treatment, where RE is root exudate solution, CP is procedural control and 'plot' is the main litter manipulation plot; year = year of study; month = month of measurement; nom.date = nominal date of measurement (set at 1st of the month); time = consecutive time point during the study; swc = soil water content at 0-6 cm depth in %; temp10 = soil temperature at 0-10 cm depth; Rsoil = soil CO2 efflux in mg C m2-1 h-1; Flux = soil CO2 efflux in umol m-2 s-1; Comments = reasons for outliers and missing values; ObsDateTime = actual date and time of each measurement

Evolving trends in the management of acute appendicitis during COVID-19 waves. The ACIE appy II study (vol 46, pg 2021, 2022)

N/