Carbon Dynamics and Land-use Choices: Building a Regional-scale Multidisciplinary Model

Policy enabling tropical forests to approach their potential contribution to global-climate-change mitigation requires forecasts of land use and carbon storage on a large scale over long periods. In this paper, we present an integrated modeling methodology that addresses these needs. We model the dynamics of the human land-use system and of C pools contained in each ecosystem, as well as their interactions. The model is national scale, and is currently applied in a preliminary way to Costa Rica using data spanning a period of over fifty years. It combines an ecological process model, parameterized using field and other data, with an economic model, estimated using historical data to ensure a close link to actual behavior. These two models are linked so that ecological conditions affect land-use choices and vice versa. The integrated model predicts land use and its consequences for C storage for policy scenarios. These predictions can be used to create baselines, reward sequestration, and estimate the value in both environmental and economic terms of including C sequestration in tropical forests as part of the efforts to mitigate global climate change. The model can also be used to assess the benefits from costly activities to increase accuracy and thus reduce errors and their societal costs.carbon, sequestration, climate change, land use, modelling

Carbon Dynamics and Land-Use Choices: Building a Regional-Scale Multidisciplinary Model

Policy enabling tropical forests to approach their potential contribution to global-climate-change mitigation requires forecasts of land use and carbon storage on a large scale over long periods. In this paper, we present an integrated modeling methodology that addresses these needs. We model the dynamics of the human land-use system and of C pools contained in each ecosystem, as well as their interactions. The model is national scale, and is currently applied in a preliminary way to Costa Rica using data spanning a period of over fifty years. It combines an ecological process model, parameterized using field and other data, with an economic model, estimated using historical data to ensure a close link to actual behavior. These two models are linked so that ecological conditions affect land-use choices and vice versa. The integrated model predicts land use and its consequences for C storage for policy scenarios. These predictions can be used to create baselines, reward sequestration, and estimate the value in both environmental and economic terms of including C sequestration in tropical forests as part of the efforts to mitigate global climate change. The model can also be used to assess the benefits from costly activities to increase accuracy and thus reduce errors and their societal costs.carbon, sequestration, climate change, land use, modelling

Minimizing Bias in Biomass Allometry: Model Selection and Log‐Transformation of Data

Nonlinear regression is increasingly used to develop allometric equations for forest biomass estimation (i.e., as opposed to the traditional approach of log‐transformation followed by linear regression). Most statistical software packages, however, assume additive errors by default, violating a key assumption of allometric theory and possibly producing spurious models. Here, we show that such models may bias stand‐level biomass estimates by up to 100 percent in young forests, and we present an alternative nonlinear fitting approach that conforms with allometric theory

Novel Forests Maintain Ecosystem Processes After the Decline of Native Tree Species

The positive relationship between species diversity (richness and evenness) and critical ecosystem functions, such as productivity, carbon storage, and nutrient cycling, is often used to predict the consequences of extinction. At regional scales, however, plant species richness is mostly increasing rather than decreasing because successful plant species introductions far outnumber extinctions. If these regional increases in richness lead to local increases in diversity, a reasonable prediction is that productivity, carbon storage, and nutrient cycling will increase following invasion, yet this prediction has rarely been tested empirically. We tested this prediction in novel forest communities dominated by introduced species (~90% basal area) in lowland Hawaiian rain forests by comparing their functionality to that of native forests. We conducted our comparison along a natural gradient of increasing nitrogen availability, allowing for a more detailed examination of the role of plant functional trait differences (specifically, N2 fixation) in driving possible changes to ecosystem function. Hawaii is emblematic of regional patterns of species change; it has much higher regional plant richness than it did historically, due to \u3e1000 plant species introductions and only ~71 known plant extinctions, resulting in an ~100% increase in richness. At local scales, we found that novel forests had significantly higher tree species richness and higher diversity of dominant tree species. We further found that aboveground biomass, productivity, nutrient turnover (as measured by soil-available and litter-cycled nitrogen and phosphorus), and belowground carbon storage either did not differ significantly or were significantly greater in novel relative to native forests. We found that the addition of introduced N2-fixing tree species on N-limited substrates had the strongest effect on ecosystem function, a pattern found by previous empirical tests. Our results support empirical predictions of the functional effects of diversity, but they also suggest basic ecosystem processes will continue even after dramatic losses of native species diversity if simple functional roles are provided by introduced species. Because large portions of the Earth\u27s surface are undergoing similar transitions from native to novel ecosystems, our results are likely to be broadly applicable

Effects of deforestation and land use on biomass, carbon, and nutrient pools in the Los Tuxtlas Region, Mexico

Land-use change in forested regions of the tropics is currently one of the largest anthropogenic perturbations on earth; it is a force capable of altering biogeochemical cycles at local, regional, and global scales. However, significant uncertainties exist concerning the impact of land-use change on biomass and elemental pools of tropical forests. To evaluate the response of biomass and elemental pools to deforestation and land-use in the Los Tuxtlas Region, Mexico, total aboveground biomass (TAGB), C, N, S, and P pools were quantified along a land-use gradient that included primary forests, pastures, cornfields, and secondary forests. TAGB of primary forests averaged 403 Mg/ha; pastures and cornfields averaged 24 and 23 Mg/ha, respectively. Conversion of primary forests to pastures or cornfields resulted in declines of 94% of aboveground C pools, 92% of aboveground N, 83% of aboveground P, and between 89% and 95% of aboveground S. Soil pools of C, N, and S did not differ significantly between primary forests, pastures, and cornfields. Soil C to a 1 m depth ranged from 166-210 Mg/ha; N and S ranged from 16,O00-2O,000 kg/ha and 340O-38OO kg/ha, respectively. In secondary forests, TAGB increased with increasing forest age; accumulations ranged from 4.8 Mg/ha in a 6-month- old site to 287 Mg/ha in a 50-year-old site. Results indicate that secondary forests will attain the equivalent of primary forest TAGB in 73 years. However, rates of TAGB accumulation were constrained by land-use history; rates decreased with increasing duration of land use prior to abandonment. Soil pools of secondary forests were not correlated to forest age or prior land-use history and did not differ significantly from soil pools of primary forests, pastures, or cornfields. As a group, soils of primary and old secondary forest sites had significantly larger pools of available N and higher rates of nitrification and N mineralization than the combined group of pastures, cornfields, and recently abandoned sites. Currently, the Los Tuxtias Region functions as a net source of greenhouse gases. Regenerating secondary forests have the capacity to counterbalance emissions resulting from deforestation, but presently constitute only a small percentage of the the regional landscape

Limited native plant regeneration in novel, exotic-dominated forests on Hawai’i

Ecological invasions are a major driver of global environmental change. When invasions are frequent and prolonged, exotic species can become dominant and ultimately create novel ecosystem types. These ecosystems are now widespread globally. Recent evidence from Puerto Rico suggests that exotic-dominated forests can provide suitable regeneration sites for native species and promote native species abundance, but this pattern has been little explored elsewhere. We surveyed 46 sites in Hawai’i to determine whether native species occurred in the understories of exotic-dominated forests. Native trees smaller than 10 cm in diameter were absent in 28 of the 46 sites and rare in the others. Natives were never the dominant understory species; in fact, they accounted for less than 10% of understory basal area at all but six sites, and less than 4% on average. Sites with native species in the understory tended to be on young lava substrate lacking human disturbance, and were mostly located close to intact, native-dominated forest stands. Even where we found some native species, however, most were survivors of past exotic encroachment into native forest, rather than products of active recolonization by native species. In contrast with successional trajectories in Puerto Rico, Hawaii\u27s exotic-dominated forests can emerge, via invasion, without human disturbance and native Hawaiian plants are largely unable to colonize them once they appear. We suggest that a wide diversity of growth strategies among the exotic species on Hawai’i may limit the opportunities for native plants to colonize exotic-dominated forests

Coping with psychological distress during COVID-19: a cautionary note of self-criticalness and personal resilience among healthcare workers

PURPOSE: The COVID-19 pandemic resulted in immense pressure on healthcare workers (HCWs) and healthcare systems worldwide. The current multi-centre evaluation sought to explore the association between coping behaviours and levels of psychological distress among HCWs working during the initial onset of COVID-19. DESIGN/METHODOLOGY/APPROACH: Between April and July 2020 HCWs at three urban hospitals in England were invited to complete an online survey measuring personal and professional characteristics, psychological distress and coping. A principal component analysis (PCA) identified components of coping and structural equation modelling (SEM) was used to test the relationship between components of coping and psychological distress. FINDINGS: A total of 2,254 HCWs participated (77% female, 67% white, 66% in clinical roles). Three components for coping were retained in the PCA analysis: external strategies, internal strategies and self-criticalness/substance use. SEM indicated that internally based coping was associated with lower levels of psychological distress, whereas externally based coping and self-criticalness were associated with greater psychological distress. The final model accounted for 35% of the variance in psychological distress. ORIGINALITY/VALUE: This multi-centre evaluation provides unique insight into the level of psychological distress among HCWs during the initial onset of the COVID-19 pandemic (2020) and associated coping strategies. Addressing self-criticalness and supporting cognitive-based internal coping strategies among HCWs may protect against prolonged exposure to psychological distress. Findings highlight the importance of developing a culture of professional resilience among this vital workforce as a whole rather than placing pressure on an individual's personal resilience

Effects of Early Surgical Exploration in Suspected Barotraumatic Perilymph Fistulas

ObjectivesTreatment of traumatic perilymph fistula (PLF) remains controversial between surgical repair and conservative therapy. The aim of this study is to analyze the outcomes of early surgical exploration in suspected barotraumatic PLF.MethodsNine patients (10 cases) who developed sudden sensorineural hearing loss and dizziness following barotrauma and underwent surgical exploration with the clinical impression of PLF were enrolled. Types of antecedent trauma, operative findings, control of dizziness after surgery, postoperative hearing outcomes, and relations to the time interval between traumatic event and surgery were assessed retrospectively.ResultsAll patients had sudden or progressive hearing loss and dizziness following trauma. Types of barotrauma were classified by the origin of the trauma: 4 external (car accident, slap injury) and 6 internal traumas (lifting, nasal blowing, straining). Surgical exploration was performed whenever PLF was suspected with the time interval of 2 to 47 days after the trauma. The possible evidence of PLF was found during surgery in 9 cases: a fibrous web around the oval window (n=3), fluid collection in the round window (RW; n=6) and bulging of the RW pseudomembrane (n=1). In every patient, vestibular symptoms disappeared immediately after surgery. The hearing was improved with a mean gain of 27.0±14.9 dB. When the surgical exploration was performed as early as less than 10 days after the trauma, serviceable hearing (≤40 dB) was obtained in 4 out of 7 cases (57.1%).ConclusionSudden or progressive sensorineural hearing loss accompanied by dizziness following barotrauma should prompt consideration of PLF. Early surgical exploration is recommended to improve hearing and vestibular symptoms

DNA repair systems and the pathogenesis of Mycobacterium tuberculosis: varying activities at different stages of infection

Mycobacteria, including most of all MTB (Mycobacterium tuberculosis), cause pathogenic infections in humans and, during the infectious process, are exposed to a range of environmental insults, including the host's immune response. From the moment MTB is exhaled by infected individuals, through an active and latent phase in the body of the new host, until the time they reach the reactivation stage, MTB is exposed to many types of DNA-damaging agents. Like all cellular organisms, MTB has efficient DNA repair systems, and these are believed to play essential roles in mycobacterial pathogenesis. As different stages of infection have great variation in the conditions in which mycobacteria reside, it is possible that different repair systems are essential for progression to specific phases of infection. MTB possesses homologues of DNA repair systems that are found widely in other species of bacteria, such as nucleotide excision repair, base excision repair and repair by homologous recombination. MTB also possesses a system for non-homologous end-joining of DNA breaks, which appears to be widespread in prokaryotes, although its presence is sporadic within different species within a genus. However, MTB does not possess homologues of the typical mismatch repair system that is found in most bacteria. Recent studies have demonstrated that DNA repair genes are expressed differentially at each stage of infection. In the present review, we focus on different DNA repair systems from mycobacteria and identify questions that remain in our understanding of how these systems have an impact upon the infection processes of these important pathogens