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Anthropogenically elevated inputs of nitrogen (N), phosphorus (P), and potassium (K) can affect the carbon (C) budget of nutrient-poor peatlands. Fungi are intimately tied to peatland C budgets due to their roles in organic matter decomposition and symbioses with primary producers; however, the influence of fertilization on peatland fungal composition and diversity remains unclear. Here, we examined the effect of fertilization over 10 years on fungal diversity, composition, and functional guilds along an acrotelm (10-20 cm), mesotelm (30-40 cm), and catotelm (60-70 cm) depth gradient at the Mer Bleue bog, Canada. Simultaneous N and PK additions decreased the relative abundance of ericoid mycorrhizal fungi and increased ectomycorrhizal fungi and lignocellulose-degrading fungi. Fertilization effects were not more pronounced in the acrotelm relative to the catotelm, nor was there a shift toward nitrophilic taxa after N addition. The direct effect of fertilization significantly decreased the abundance of Sphagnum-associated fungi, primarily owing to the overarching role of limiting nutrients rather than a decline in Sphagnum cover. Increased nutrient loading may threaten peatland C stocks if lignocellulose-degrading fungi become abundant and accelerate decomposition of recalcitrant organic matter. Additionally, future changes in plant communities, strong water table fluctuations, and peat subsidence after long-term nutrient loading may also influence fungal functional guilds and depth-dependencies of fungal community structure., (© 2024 John Wiley & Sons Ltd.)

Peatlands are globally significant sources of atmospheric methane (CH 4 ). While several studies have examined the effects of nutrient addition on CH 4 dynamics, there are few long-term peatland fertilization experiments, which are needed to understand the aggregated effects of nutrient deposition on ecosystem functioning. We investigated responses of CH 4 flux and production to long-term field treatments with three levels of N (1.6-6.4 g m -2 yr -1 as NH 4 NO 3 ), potassium and phosphorus (PK, 5.0 g P and 6.3 g K m -2 yr -1 as KH 2 PO 4 ), and NPK in a temperate bog. Methane fluxes were measured in the field from May to August in 2005 and 2015. In 2015 CH 4 flux was higher in the NPK treatment with 16 years of 6.4 g N m -2 yr -1 than in the control (50.5 vs. 8.6 mg CH 4 m -2 d -1 ). The increase in CH 4 flux was associated with wetter conditions derived from peat subsidence. Incubation of peat samples, with and without short-term PK amendment, showed that potential CH 4 production was enhanced in the PK treatments, both from field application and by amending the incubation. We suggest that changes in this bog ecosystem originate from long-term vegetation change, increased decomposition and direct nutrient effects on microbial dynamics.

To study vegetation feedbacks of nutrient addition on carbon sequestration capacity, we investigated vegetation and ecosystem CO2 exchange at Mer Bleue Bog, Canada in plots that had been fertilized with nitrogen (N) or with N plus phosphorus (P) and potassium (K) for 7-12 years. Gross photosynthesis, ecosystem respiration, and net CO2 exchange were measured weekly during May-September 2011 using climate-controlled chambers. A substrate-induced respiration technique was used to determine the functional ability of the microbial community. The highest N and NPK additions were associated with 40% less net CO2 uptake than the control. In the NPK additions, a diminished C sink potential was due to a 20-30% increase in ecosystem respiration, while gross photosynthesis rates did not change as greater vascular plant biomass compensated for the decrease in Sphagnum mosses. In the highest N-only treatment, small reductions in gross photosynthesis and no change in ecosystem respiration led to the reduced C sink. Substrate-induced microbial respiration was significantly higher in all levels of NPK additions compared with control. The temperature sensitivity of respiration in the plots was lower with increasing cumulative N load, suggesting more labile sources of respired CO2 . The weaker C sink potential could be explained by changes in nutrient availability, higher woody : foliar ratio, moss loss, and enhanced decomposition. Stronger responses to NPK fertilization than to N-only fertilization for both shrub biomass production and decomposition suggest that the bog ecosystem is N-P/K colimited rather than N-limited. Negative effects of further N-only deposition were indicated by delayed spring CO2 uptake. In contrast to forests, increased wood formation and surface litter accumulation in bogs seem to reduce the C sink potential owing to the loss of peat-forming Sphagnum., (© 2013 John Wiley & Sons Ltd.)

Plants in nutrient-poor environments typically have low foliar nitrogen (N) concentrations, long-lived tissues with leaf traits designed to use nutrients efficiently, and low rates of photosynthesis. We postulated that increasing N availability due to atmospheric deposition would increase photosynthetic capacity, foliar N, and specific leaf area (SLA) of bog shrubs. We measured photosynthesis, foliar chemistry and leaf morphology in three ericaceous shrubs (Vaccinium myrtilloides, Ledum groenlandicum and Chamaedaphne calyculata) in a long-term fertilization experiment at Mer Bleue bog, Ontario, Canada, with a background deposition of 0.8 g N m(-2) a(-1). While biomass and chlorophyll concentrations increased in the highest nutrient treatment for C. calyculata, we found no change in the rates of light-saturated photosynthesis (A(max)), carboxylation (V(cmax)), or SLA with nutrient (N with and without PK) addition, with the exception of a weak positive correlation between foliar N and A(max) for C. calyculata, and higher V(cmax) in L. groenlandicum with low nutrient addition. We found negative correlations between photosynthetic N use efficiency (PNUE) and foliar N, accompanied by a species-specific increase in one or more amino acids, which may be a sign of excess N availability and/or a mechanism to reduce ammonium (NH(4)) toxicity. We also observed a decrease in foliar soluble Ca and Mg concentrations, essential minerals for plant growth, but no change in polyamines, indicators of physiological stress under conditions of high N accumulation. These results suggest that plants adapted to low-nutrient environments do not shift their resource allocation to photosynthetic processes, even after reaching N sufficiency, but instead store the excess N in organic compounds for future use. In the long term, bog species may not be able to take advantage of elevated nutrients, resulting in them being replaced by species that are better adapted to a higher nutrient environment.

Although oppositional defiant disorder (ODD) and anxiety disorders (ADs) often co-occur, the literature is mixed regarding the effects of such co-occurrence. For example, there is evidence that AD symptoms may mitigate ODD symptoms (buffer hypothesis) or exacerbate ODD symptoms (multiple problem hypothesis). A dual-pathway model incorporates previous research and addresses both hypotheses. We describe several possible etiological or risk processes that may underlie each of these ODD-AD pathways, including child temperament, aggression, limbic system processes, executive functioning abilities, and social information-processing biases, and suggest an integrated model. We conclude with implications for the model and directions for future research involving co-occurring ODD and ADs.

The current review uses a developmental perspective to examine processes that may underlie and partially account for the association between anxiety disorders and disruptive behavior disorders among children and adolescents. We propose that one way to understand development of comorbid anxiety and disruptive behavior disorders is to examine symptoms that are precursors for or part of these syndromes, such as anxious symptoms and reactive aggression. We use a framework that considers these issues first at the syndrome or disorder level (e.g., anxiety disorders, disruptive behavior disorders), then at the symptom level (e.g., anxious symptoms and reactive aggression), and finally at the risk factor level (e.g., factors associated with anxious symptoms and/or reactive aggression). We apply various frameworks that have been put forth for understanding comorbidity of psychological syndromes to the co-occurrence of anxiety and disruptive behavior disorders and to the co-occurrence of reactive aggression and anxious symptoms where possible. We then identify gaps in the literature with regard to anxiety and reactive aggression, as well as anxiety and disruptive behavior disorders more generally. Finally, we provide a conceptual model describing how the relation of anxiety and reactive aggression may develop into clinically identifiable, comorbid anxiety and disruptive behavior disorders.

Although previous research has identified various child-specific and contextual risk factors associated with externalizing behaviors, there is a dearth of literature examining child x context interactions in the prospective prediction of externalizing behaviors. To address this gap, we examined autonomic functioning as a moderator of the relation between contextual factors (i.e., neighborhood cohesion and harsh parental behaviors) and externalizing behaviors. Participants were an ethnic minority, inner-city sample of first through fourth grade children (N = 57, 50% male) and their primary caregivers who participated in two assessments approximately 1 year apart. Results indicated that baseline sympathetic functioning moderated the relation between (a) neighborhood cohesion and externalizing behaviors and (b) harsh parental behaviors and externalizing behaviors. Post-hoc probing of these interactions revealed that higher levels of neighborhood cohesion prospectively predicted (a) higher levels of externalizing behaviors among children with heightened baseline sympathetic functioning, and (b) lower levels of externalizing behaviors among children with attenuated baseline sympathetic functioning. In addition, among children with heightened baseline sympathetic functioning, higher levels of harsh parental behaviors prospectively predicted higher levels of externalizing behaviors., ((PsycINFO Database Record (c) 2009 APA, all rights reserved).)

We tested a conceptual model involving the inter-relations among affective decision-making (indexed by a gambling task), autonomic nervous system (ANS) activity, and attention-deficit/hyperactivity disorder (ADHD) and oppositional defiant disorder (ODD) symptoms in a largely impoverished, inner city sample of first through third grade children (N=63, 54% male). The present study hypothesized that impaired affective decision-making and decreased sympathetic and parasympathetic activation would be associated with higher levels of ADHD and ODD symptoms, and that low sympathetic and parasympathetic activation during an emotion-inducing task would mediate the relation between affective decision-making and child externalizing symptoms. In support of our model, disadvantageous decision-making on a gambling task was associated with ADHD hyperactivity/impulsivity symptoms among boys, and attenuated sympathetic activation during an emotion-inducing task mediated this relation. Support for the model was not found among girls.

Can short, ungraded, free-writing assignments promote learning of course material? We randomly assigned introductory psychology recitation sections ( N = 978 students) to writing or thinking conditions. For all sections, teaching assistants presented students with a discussion topic based in current coursework. Students either wrote or thought about the topic for 5 min. All sections then discussed the topic for approximately 10 min. Exams included questions related to the discussion topics. Students in the writing condition attended class more often and performed better on factual and conceptual multiple-choice exam questions than students in the thinking condition, even after controlling for measures of student quality. The results suggested that brief free writing improved factual and conceptual learning.

Wetlands are significant sources of atmospheric methane, an important radiatively active 'greenhouse' gas that accounts for an estimated 12% of total greenhouse warming. Since global climate models predict the greatest temperature and precipitation changes at high latitudes, and as the largest areas of wetland (346 × 10(6)ha) are in the boreal and subarctic regions (40-70°N), recent research has focused on Identifying the factors that control methane emission from northern wetlands. Over the past few years, the database has expanded tremendously, and much progress has been made in understanding the environmental controls on methane emission at small spatial and temporal scales. However, we now need to broaden our understanding of regional differences in methane emission, ecological responses of northern wetlands to climate change, and the effect of other perturbations such as drainage and flooding., (Copyright © 1994. Published by Elsevier Ltd.)