Strategic application of wildland fire suppression in the southwestern United States.

Much of the western United States is experiencing longer fire seasons with an increased frequency of high-severity fires and fire risk. Fire managers in the southwestern United States have increased efforts to reduce fire risk by managing more fires to meet resource objectives (e.g. thin forests, reduce hazardous fuel loads, and restore the landscape). However, little is known about the situational circumstances and decision space that inform the strategic response to wildland fire. Using generalized and time-to-event modeling techniques, we examined how fire management decisions are reached in a context informed by weather, burning conditions, and subsequent fire behavior. Modeling results captured daily containment probabilities along a gradient from limiting natural conditions to suppression invoked containment. Results inform fire management decisions, future research efforts, and the simulation of wildland fires with resource objectives.

Adolescent cannabis exposure interacts with mutant DISC1 to produce impaired adult emotional memory.

Cannabis is an increasingly popular and controversial drug used worldwide. Cannabis use often begins during adolescence, a highly susceptible period for environmental stimuli to alter functional and structural organization of the developing brain. Given that adolescence is a critical time for the emergence of mental illnesses before full-onset in early adulthood, it is particularly important to investigate how genetic insults and adolescent cannabis exposure interact to affect brain development and function. Here we show for the first time that a perturbation in disrupted in schizophrenia 1 (DISC1) exacerbates the response to adolescent exposure to delta-9-tetrahydrocannabinol (Δ(9)-THC), a major psychoactive ingredient of cannabis, consistent with the concept that gene-environment interaction may contribute to the pathophysiology of psychiatric conditions. We found that chronic adolescent treatment with Δ(9)-THC exacerbates deficits in fear-associated memory in adult mice that express a putative dominant-negative mutant of DISC1 (DN-DISC1). Synaptic expression of cannabinoid receptor 1 (CB1R) is down-regulated in the prefrontal cortex, hippocampus, and amygdala, critical brain regions for fear-associated memory, by either expression of DN-DISC1 or adolescent Δ(9)-THC treatment. Notably, elevation of c-Fos expression evoked by context-dependent fear memory retrieval is impaired in these brain regions in DN-DISC1 mice. We also found a synergistic reduction of c-Fos expression induced by cue-dependent fear memory retrieval in DN-DISC1 with adolescent Δ(9)-THC exposure. These results suggest that alteration of CB1R-mediated signaling in DN-DISC1 mice may underlie susceptibility to detrimental effects of adolescent cannabis exposure on adult behaviors.

A new method for studying social eavesdropping using male golden hamsters.

Social eavesdropping is a special type of social learning and it is defined as the act of extracting information from social interactions between conspecifics. Social eavesdropping has advantages in information gathering and has attracted increasing attention. Emerging studies on social eavesdropping have been reported in several species, but the lack of suitable and manipulable laboratory rodent models remains a challenge to the study of the underlying mechanisms of social eavesdropping. The aim of this study was to take advantage of golden hamsters and their agonistic behaviors to develop a new laboratory method to study social eavesdropping. Male hamsters with or without a defeat experience were used as bystanders and were exposed to either a fighting interaction or a neutral encounter between two male demonstrators in a social learning chamber for a 3-day social learning. The behavioral responses of the bystanders toward observed demonstrators were tested in a U-shaped maze before and after the 3-day social learning. We found that (1) bystanders were attracted to the winning demonstrators in both short-term and long-term tests in experiment 1; (2) bystanders with a brief defeat experience displayed the opposite behavioral pattern and avoided approaching the winning demonstrator in experiment 2. It is evident that these hamsters acquired information about the relative qualities and dominance of the demonstrators and behaved differently toward different conspecifics afterward. Collectively, male hamsters are capable of social eavesdropping and prior experience of defeat has a significant impact on their consequent behaviors. Our newly developed behavioral method offers several advantages and it is useful for the study of social eavesdropping and its underlying mechanisms.

Investigation of gene effects and epistatic interactions between Akt1 and neuregulin 1 in the regulation of behavioral phenotypes and social functions in genetic mouse models of schizophrenia.

Accumulating evidence from human genetic studies has suggested several functional candidate genes that might contribute to susceptibility to schizophrenia, including AKT1 and neuregulin 1 (NRG1). Recent findings also revealed that NRG1 stimulates the PI3-kinase/AKT signaling pathway, which might be involved in the functional outcomes of some schizophrenic patients. The aim of this study was to evaluate the effect of Akt1-deficiency and Nrg1-deficiency alone or in combination in the regulation of behavioral phenotypes, cognition, and social functions using genetically modified mice as a model. Male Akt1 (+/-), Nrg1 (+/-), and double mutant mice were bred and compared with their wild-type (WT) littermate controls. In Experiment 1, general physical examination revealed that all mutant mice displayed a normal profile of body weight during development and a normal brain activity with microPET scan. In Experiment 2, no significant genotypic differences were found in our basic behavioral phenotyping, including locomotion, anxiety-like behavior, and sensorimotor gating function. However, both Nrg1 (+/-) and double mutant mice exhibited impaired episodic-like memory. Double mutant mice also had impaired sociability. In Experiment 3, a synergistic epistasis between Akt1 and Nrg1 was further confirmed in double mutant mice in that they had impaired social interaction compared to the other 3 groups, especially encountering with a novel male or an ovariectomized female. Double mutant and Nrg1 (+/-) mice also emitted fewer female urine-induced ultrasonic vocalization calls. Collectively, our results indicate that double deficiency of Akt1 and Nrg1 can result in the impairment of social cognitive functions, which might be pertinent to the pathogenesis of schizophrenia-related social cognition.

Toward full economic valuation of forest fuels-reduction treatments.

Our goal was to move toward full economic valuation of fuels-reduction treatments applied to ponderosa pine (Pinus ponderosa) forests. For each of five fuels-reduction projects in northern Arizona, we calculated the economic value of carbon storage and carbon releases over one century produced by two fuels-reduction treatments of thinning following by prescribed burning every one (Rx10) or two (Rx20) decades and for no treatment followed by intense wildfire once in the first 50 years (HF50) or once in the first 100 years (HF100). Our estimates include two uses of harvested wood, the current use as pallets, and multiproduct use as paper, pallets, and construction materials. Additionally, we included the economic value of damage and loss from wildfire. Results indicate that treatments increase carbon stock in live trees over time; however, the inclusion of carbon emissions from treatments reduces net carbon storage and thereby carbon credits and revenue. The economic valuation shows that the highest net benefit of $5029.74 ha(-1) occurs for the Rx20 treatment with the HF50 baseline and the high estimated treatment benefits of avoided losses, regional economic benefits, and community value of fire risk reduction. The lowest net benefit of -$3458.02 ha(-1) occurs for the Rx10 treatment with the HF100 baseline and the low estimated treatment benefits. We conclude that current nonmarket values such as avoided wildfire damage should be included with values of traditional wood products and emerging values of carbon storage to more appropriately estimate long-term benefits and costs of forest fuels-reduction treatments.

Characterization of behavioural responses in different test contexts after a single social defeat in male golden hamsters (Mesocricetus auratus).

The objective of the present study was to characterize behavioural responses of male hamsters in each of three test contexts after they had experienced either a single social defeat or a neutral encounter. In experiment 1, hamsters were observed in a familiar social context (i.e., their home cages), and defeated males displayed different amounts of time and submissive behaviours towards a known opponent than a novel intruder, whereas males in the neutral-encounter groups did not show such differences. In experiment 2, in an unfamiliar social context (i.e., a Y-maze), defeated males generated submissive behaviours and fear memory towards a known opponent that they re-encountered 5-min and 24-h after the defeat. The formation of long-term memory was interrupted by an injection of anisomycin (210 mg/kg). In experiment 3, in a non-social, anxiogenic context, hamsters that had previously had different social experiences did not demonstrate additional anxiety in an elevated plus-maze, with the exception of males that had previously experienced repeated social defeats. Our data suggested that hamsters' behavioural changes following defeat are context-dependent and stimulus-specific. The experience of a single social defeat is sufficient to regenerate submissive behaviours and fear memory when reencountering a known opponent.

Extra-cellular signal-regulated kinase 1/2 (ERK1/2) activated in the hippocampal CA1 neurons is critical for retrieval of auditory trace fear memory.

The brain regions involved with trace fear conditioning (TFC) and delayed fear conditioning (DFC) are well-characterized, but little is known about the cellular representation subsuming these types of classical conditioning. Previous evidence has shown that activation of the amygdala is required for both TFC and DFC, while TFC also involves the hippocampus for forming conditioned response to tone. Lesions of the hippocampus did not affect tone learning in DFC, but it impaired learning in TFC. Synaptic plasticity in the hippocampus, underlying a cellular representation subsuming learning and memory, is in part modulated by extra-cellular signal-regulated kinase (ERK) signaling pathway. ERK1/2 activation is required for both TFC and DFC during memory formation, but whether this pathway is involved in memory retrieval of TFC is still unknown. In the present study, we investigated changes in ERK1/2 phosphorylation after memory retrieval in groups of mice that received TFC, DFC, tone-shock un-paired conditioning, and naïve control. Our results showed that ERK1/2 phosphorylation was elevated in the hippocampal CA1 region after retrieval of all conditioned fear responses. In particular, in the TFC group, immunohistochemistry indicated higher level of ERK1/2 phosphorylation in the hippocampal pyramidal neurons 30min after tone testing. Inhibition of the ERK1/2 signaling pathway diminished fear memory elicited by a tone in TFC. Together these results suggest that the memory retrieval process in TFC is more dependent on ERK1/2 signaling pathway than that in DFC. ERK1/2 signaling is critical for retrieval associative memory of temporally noncontiguous stimuli.

Modeling the impacts of two bark beetle species under a warming climate in the southwestern USA: Ecological and economic consequences.

Predicted climate warming is expected to have profound effects on bark beetle population dynamics in the southwestern United States. Temperature-mediated effects may include increases in developmental rates, generations per year, and changes in habitat suitability. As a result, the impacts of Dendroctonus frontalis and Dendroctonus mexicanus on forest resources are likely subject to amplification. To assess the implications of such change, we evaluated the generations per year of these species under three climate scenarios using a degree-day development model. We also assessed economic impacts of increased beetle outbreaks in terms of the costs of application of preventative silvicultural treatments and potential economic revenues forgone. Across the southwestern USA, the potential number of beetle generations per year ranged from 1-3+ under historical climate, an increase of 2-4+ under the minimal warming scenario and 3-5+ under the greatest warming scenario. Economic benefits of applying basal area reduction treatments to reduce forest susceptibility to beetle outbreaks ranged from $7.75/ha (NM) to $95.69/ha (AZ) under historical conditions, and $47.96/ha (NM) to $174.58/ha (AZ) under simulated severe drought conditions. Basal area reduction treatments that reduce forest susceptibility to beetle outbreak result in higher net present values than no action scenarios. Coupled with other deleterious consequences associated with beetle outbreaks, such as increased wildfires, the results suggest that forest thinning treatments play a useful role in a period of climate warming.

Economic analysis of sequestering carbon in green ash forests in the Lower Mississippi River Valley.

Since the U.S. is the largest emitter of carbon dioxide (CO2), it has become crucial to develop options that are both cost effective and supportive of sustainable development to reduce atmospheric CO2. Electric utility companies have the options of reducing their use of fossil fuels, switching to alternative energy sources, increasing efficiency, or offsetting carbon emissions. This study determined the cost and profitability of sequestering carbon in green ash plantations, and the number of tons of carbon that can be sequestered. The profitability of green ash is 2,342 dollars and 3,645 dollars per acre on site indices (measurement of soil quality) 65 and 105 land, respectively, calculated with a 2.5% alternative rate of return (ARR). These figures shift to -248 dollars and -240 dollars calculated with a 15.0% ARR. If landowners who have an ARR of 2.5% can sell carbon credits for 10 dollars per ton of carbon, profits will increase by 107 dollars per acre on poor sites and 242 dollars on good sites. Over one rotation (cutting cycle), 38.56 net tons of carbon can be sequestered on an acre of poor quality land and 51.35 tons on good quality land. The cost of sequestering carbon, without including revenues from timber production and carbon credits, ranges from a high of 15.20 dollars per ton on poor sites to 14.41 dollars on good sites, calculated with a 2.5% ARR; to a high of 8.51 dollars per ton on poor sites to 7.63 dollars on good sites, calculated with a 15.0% ARR. The cost of storing carbon can be reduced significantly if the trees can be sold for wood products.