AIM: We developed a set of statistical models to improve spatial estimates of mangrove aboveground biomass (AGB) based on the environmental signature hypothesis (ESH). We hypothesized that higher ...tidal amplitudes, river discharge, temperature, direct rainfall and decreased potential evapotranspiration explain observed high mangrove AGB. LOCATION: Neotropics and a small portion of the Nearctic region. METHODS: A universal forest model based on site‐level forest structure statistics was validated to spatially interpolate estimates of mangrove biomass at different locations. Linear models were then used to predict mangrove AGB across the Neotropics. RESULTS: The universal forest site‐level model was effective in estimating mangrove AGB using pre‐existing mangrove forest structure inventories to validate the model. We confirmed our hypothesis that at continental scales higher tidal amplitudes contributed to high forest biomass associated with high temperature and rainfall, and low potential evapotranspiration. Our model explained 20% of the spatial variability in mangrove AGB, with values ranging from 16.6 to 627.0 t ha⁻¹ (mean, 88.7 t ha⁻¹). Our findings show that mangrove AGB has been overestimated by 25–50% in the Neotropics, underscoring a commensurate bias in current published global estimates using site‐level information. MAIN CONCLUSIONS: Our analysis show how the ESH significantly explains spatial variability in mangrove AGB at hemispheric scales. This finding is critical to improve and explain site‐level estimates of mangrove AGB that are currently used to determine the relative contribution of mangrove wetlands to global carbon budgets. Due to the lack of a conceptual framework explicitly linking environmental drivers and mangrove AGB values during model validation, previous works have significantly overestimated mangrove AGB; our novel approach improved these assessments. In addition, our framework can potentially be applied to other forest‐dominated ecosystems by allowing the retrieval of extensive databases at local levels to generate more robust statistical predictive models to estimate continental‐scale biomass values.
Human brain activity is intrinsically organized into resting-state networks (RSNs) that transiently activate or deactivate at the sub-second timescale. Few neuroimaging studies have addressed how ...Alzheimer's disease (AD) affects these fast temporal brain dynamics, and how they relate to the cognitive, structural and metabolic abnormalities characterizing AD. We aimed at closing this gap by investigating both brain structure and function using magnetoencephalography (MEG) and hybrid positron emission tomography-magnetic resonance (PET/MR) in 10 healthy elders, 10 patients with subjective cognitive decline (SCD), 10 patients with amnestic mild cognitive impairment (aMCI) and 10 patients with typical Alzheimer's disease with dementia (AD). The fast activation/deactivation state dynamics of RSNs were assessed using hidden Markov modeling (HMM) of power envelope fluctuations at rest measured with MEG. Correlations were sought between temporal properties of HMM states and participants' cognitive test scores, whole hippocampal grey matter volume and regional brain glucose metabolism. The posterior default-mode network (DMN) was less often activated and for shorter durations in AD patients than matched healthy elders. No significant difference was found in patients with SCD or aMCI. The time spent by participants in the activated posterior DMN state did not correlate significantly with cognitive scores, nor with the whole hippocampal volume. However, it correlated positively with the regional glucose consumption in the right dorsolateral prefrontal cortex (DLPFC). AD patients present alterations of posterior DMN power activation dynamics at rest that identify an additional electrophysiological correlate of AD-related synaptic and neural dysfunction. The right DLPFC may play a causal role in the activation of the posterior DMN, possibly linked to the occurrence of mind wandering episodes. As such, these data might suggest a neural correlate of the decrease in mind wandering episodes reported in pathological aging.
Mangroves are one of the most carbon‐dense forests on the Earth and have been highlighted as key ecosystems for climate change mitigation and adaptation. Hundreds of studies have investigated how ...mangroves fix, transform, store, and export carbon. Here, we review and synthesize the previously known and emerging carbon pathways in mangroves, including gains (woody biomass accumulation, deadwood accumulation, soil carbon sequestration, root and litterfall production), transformations (food web transfer through herbivory, decomposition), and losses (respiration as CO2 and CH4, litterfall export, particulate and dissolved carbon export). We then review the technologies available to measure carbon fluxes in mangroves, their potential, and their limitations. We also synthesize and compare mangrove net ecosystem productivity (NEP) with terrestrial forests. Finally, we update global estimates of carbon fluxes with the most current values of fluxes and global mangrove area. We found that the contributions of recently investigated fluxes, such as soil respiration as CH4, are minor (<1 Tg C year−1), while the contributions of deadwood accumulation, herbivory, and lateral export are significant (>35 Tg C year−1). Dissolved inorganic carbon exports are an order of magnitude higher than the other processes investigated and were highly variable, highlighting the need for further studies. Gross primary productivity (GPP) and ecosystem respiration (ER) per area of mangroves were within the same order of magnitude as terrestrial forests. However, ER/GPP was lower in mangroves, explaining their higher carbon sequestration. We estimate the global mean mangrove NEP of 109.1 Tg C year−1 (7.4 Mg C ha−1 year−1) or through a budget balance, accounting for lateral losses, a global mean of 66.6 Tg C year−1 (4.5 Mg C ha−1 year−1). Overall, mangroves are highly productive, and despite losses due to respiration and tidal exchange, they are significant carbon sinks.
This article identifies the major principles of general assessment theory, examines how these principles can be applied to an online environment, and identifies and describes several assessment ...issues that have special significance in a virtual classroom. In particular, the issues of proctored testing, identity security, academic honesty, and use of online discussions for assessment purposes are examined. Practical suggestions are included to assist both first-time and experienced online instructors develop assessment components for their online courses. Throughout this article the emphasis is on the creation of assessments in a constructivist environment where the emphasis is on relationships, inquiry, invention, and the construction of understanding through collaborative work and discussions.
Since the fifties the Baixada Santista’s landscape has been intensively modified by spreading unplanned and illegal human settlements, mainly by industrial and harboring activities. On 3rd September ...1998, a portion of the mangrove forests that surround the Barnabé Island, Santos, State of São Paulo, Brazil (23°55’23”S; 46°19’28”W) was affected by a fire due to the accidental spillage of a flammable chemical substance called dicyclopentadiene (DCPD). The goals of the current study were to determine the impacts as well as to assess the initial natural recovery of this mangrove forest. Six permanent plots, were established. Three of them were used to gather data from the adult individuals that survived after spillage (M1, M2 and M3) and the others to investigate the recruitments presents in the natural recovery (RN1, RN2 e RN3) using standardized methodology. Among the adult individuals, Laguncularia racemosa was the dominant species. The densities of dead stems for these quadrants, especially for M1 and M3, were very high reaching 65.39% and 48.97%, respectively. The RN1 and RN2 plots were also dominated by L. racemosa with 100% of the stems alive. RN3 was dominated by Avicennia schaueriana but showed a decrease in the proportion of alive stems (89.09%). The magnitude of the accident is evidenced considering half (M3) or more (M1) out of the total number of stems were found dead. Yet simple and inexpensive, the methodology applied in the current study showed to be an effective tool to evaluate impacts over mangrove stands. Finally, we recommend that Baixada Santista’s integrated coastal management process must incorporate long-term mangrove monitoring.
•Pneumatic artificial muscle-based devices can be used safely in the MRI setting.•They do not induce any significant decrease in the SNR of fMRI data.•Such devices are suitable to generate passive ...movements of different body parts.•They allow to map the contralateral primary sensorimotor cortex in healthy subjects.•The increase in BOLD signal is lower as compared to analogous active movements.
Two major concerns with respect to task-based motor functional magnetic resonance imaging (fMRI) are inadequate participants’ performance as well as intra- and inter-subject variability in execution of the motor action.
This study validates the use of an MRI-compatible stimulator based on a pneumatic artificial muscle (PAM) for block-design fMRI mapping of the primary sensorimotor (SM1) cortex in a series of fifteen right-handed healthy subjects. The PAM stimulator elicits computer-controlled timely and reproducible passive movements of fingers/toes. Participants performed comparable active and passive PAM-induced flexion-extensions of the index fingers.
Passive movement of the right index finger and passive alternating right and left index finger movement resulted in a significant increase in blood-oxygen-level-dependent (BOLD) signal in contralateral SM1 cortex in 14/15 and 15/15 subjects respectively. Similar networks were recruited by active and passive index finger movements. However, at the group level, active movement induced significantly higher increases in BOLD signal than passive movement in contralateral SM1 cortex (p < 0.05 Family Wise Error FWE corrected), supplementary motor area (p < 0.001 uncorrected), ipsilateral cerebellum (p < 0.001 uncorrected), and bilateral putamina (p < 0.001 uncorrected).
As compared to the several MRI-compatible robotic devices for computer-controlled passive movement of the fingers that were introduced in the past decades, the proposed PAM-based stimulator is smaller, handier, and easier to use in the MRI setting.
PAM-based stimulators can be reliably used for passive sensorimotor fMRI mapping in healthy subjects. Using this approach, bilateral SM1 cortices can be mapped accurately during a single 6-min block-design fMRI protocol.
The purpose of this study was to measure sense of classroom community in a television-based higher education distance education course and in the same course taught by the same instructor in a ...traditional face-to-face learning environment, in order to determine if differences existed and if so to identify the nature of these differences. Participants for this study consisted of 120 adult learners who were enrolled in either of two sections of a semester-long undergraduate educational technology course offered by an urban state university. One section was taught traditionally and the other section was taught to a small studio audience and at a distance to 24 remote classroom sites using synchronous one-way television and two-way audio technologies. Study results revealed a significantly lower sense of classroom community among learners in the distance education course, to include the studio audience.
The purpose of this study was to analyze a five-week graduate-level education course taught entirely at a distance via the Internet using the Blackboard.com℠ e-learning system, with emphasis on ...exploring the dynamics of sense of classroom community. Subjects were 20 adult learners, evenly divided between males and females, who were administered the sense of classroom community index at the beginning and end of the course in order to measure classroom community. Findings indicated that on-line learners took advantage of the "learn anytime" characteristics of the Internet by accessing the course seven days per week, 24 hours per day. Sense of classroom community grew significantly during the course. Females manifested a stronger sense of community than their male counterparts both at the start and end of the course. Additionally, female students exhibited a mostly connected communication pattern while the communication pattern of males was mostly independent.
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