The long-term effects of pre-commercial thinning on carbon storage and distribution in western larch (Larix occidentalis) stands of the Northern Rockies: Insights from a long-term silvicultural experiment.

The long-term effects of pre-commercial thinning on carbon storage and distribution in western larch (Larix occidentalis) stands of the Northern Rockies: Insights from a long-term silvicultural experiment. Principle investigator: Michael Schaedel Using forests to sequester and store carbon in order to mitigate climate change has gained interest in public policy discussions and is increasingly becoming a land management objective. Research indicates that forests currently sequester approximately 10% of annual US fossil fuel emissions and it is suggested that through intentional carbon management that this rate could be increased. Forests store atmospheric carbon in biomass through photosynthetic uptake. Many studies show that high tree densities may store the greatest amount of on-sight carbon. However, there are trade-offs to managing forests solely for carbon sequestration, namely a decrease in forest resilience that may lead to a higher frequency and severity of fires, insect outbreaks, and disease. These large scale disturbances cause the release of much of the stored carbon in the forest ecosystem. Tree density management, often accomplished through thinning, is one of the major tools foresters employ in order to improve forest health and resilience. While thinning is a common practice in restoring resilience to forest ecosystems and managing forests for the production of wood products little is known about the long-term effects of thinning on the ability of forest to act as carbon sinks. This study examines how the common practice of forest thinning affects carbon storage in western larch dominated mixed-conifer forests in the Northern Rockies. Past studies of the effects of thinning and partial harvest on carbon storage have contradictory findings; some studies show that thinning causes increased carbon storage, attributable to increased growth rates of residual trees, while other studies find a decrease in carbon storage due to the removal of tree biomass from the forest stand. These conflicting results are potentially caused by several differences in study designs: 1) thinning objectives, 2) carbon storage pools measured, 3) length of the study and, 4) age of the stand when thinned. The five major pools of carbon storage are live-tree biomass, live-understory biomass, dead woody detritus, forest floor litter and duff, and mineral soil. This study is superimposed on a long-term western larch spacing study established in northern Montana in 1961. The larch spacing study used a 3x3 factorial design made up of three thinning intensities (residual tree densities of 494 TPH, 890 TPH, and 1640 TPH) and three thinning intervals ( entries every 10 years (4 entries), every 20 years (2 entries), and every 40 years (1 entry)). Data was collected at a five year intervals from 1961 to 2001 on a suite of attributes of tree growth and vigor. For this study, carbon will be measure in five major pools: live tree, understory vegetation, woody detritus and snags, forest floor, and mineral soil. To capture live-tree biomass a re-measurement of the larch spacing study will be completed to capture tree attributes on all of the 0.04 ha treatment plots. Allometric equations will be used to convert tree volume to carbon biomass. Understory vegetation will be sampled in 0.25 subplots by clipping the vegetation and taking it back to a lab to analyze carbon content. Dead woody detritus will be measured by doing a census of woody debris in the 0.04 ha plot and converting the volume to carbon using established equations that take into account changes in wood density due to the stages of woody decay. The forest floor will be sampled in 0.05 circular plots where all organic material is taken to a lab and burned to analyze carbon content. Mineral soil will be sampled using soil cores taken to a depth of 30cm and analyzed by burning the soil to measure the carbon content. Measurements will be taken in the summer of 2015. Live tree and understory carbon will be tracked through time using the new data in conjunction with the data from the long-term western larch spacing study. An oral presentation of this study will include an analysis of live tree and understory carbon storage trends through time utilizing existing data from the larch spacing study. By measuring 5 major carbon pools and using a long- term data set this study will be able to provide more conclusive information on the effects of thinning on carbon storage. This data will help land managers identify effective ways of managing mixed-conifer forests as carbon sinks and asses any carbon storage trade-offs made while managing for other objectives, such as forest resilience and wood production

DENSITY MANAGEMENT IN YOUNG WESTERN LARCH STANDS: TREE GROWTH, STAND YIELD, AND CARBON STORAGE 54 YEARS AFTER THINNING

Long-term silvicultural experiments can be used to test novel ecological hypotheses and answer contemporary management questions that were not envisioned at study initiation. We used a 54-year old western larch precommercial thinning (PCT) study in northwest Montana to examine two sets of questions: (1) how different PCT regimes affect long-term stand yield and tree growth, and (2) how PCT affects total aboveground carbon (C) storage and distribution among C pools. The study has three target densities (494 trees ha-1, 890 trees ha-1, and 1680 trees ha-1) and three numbers of entries to achieve those target densities (1, 2, and 4 entries). We included unthinned plots for comparison in our C analysis. We measured multiple tree attributes and sampled three additional aboveground C pools: understory/ mid-story vegetation, woody detritus, and forest floor material. Tree measurements were used to calculate tree- and stand-level attributes, as well as total live tree C. Carbon samples from other pools were processed in a lab. ANOVA and linear contrasts were used to test specific research questions. Results from our yield analysis found long-term constant yield and constant volume growth over a range of densities. The primary effect of early thinning is to control whether volume and tree crown are concentrated on few large individuals or spread over a greater number of small individuals. Top height was negatively affected by higher densities. Height to diameter ratio, an attribute related to tree stability, acted to increase mortality in high density plots, decreasing yield at higher densities. Three main conclusions follow from our examination of effects of early thinning on total aboveground C. (1) Fifty-four years after treatment total aboveground C of stands precommercially thinned to a wide range of densities is similar, due primarily to the increase in mean tree C of trees grown at lower stand densities. (2) Sixty-two years after stand replacing disturbance deadwood legacies from the pre-disturbance forest still play an important role in long-term C storage. (3) Given enough time since early thinning, there is no trade-off between managing stands to promote individual tree growth, and maximizing stand level accumulation of aboveground C

The Effects of Forest Litterfall on Snow Melting Rates in Northern Rockies Mixed-Conifer Forests

Forest litter within a snowpack changes the snow albedo, affecting springtime melt rates. Albedo, the percent of shortwave radiation a surface reflects, is high in snow and low in forest litter. Litter absorbs shortwave radiation and reemits longwave radiation, which should increase snowmelt rates. We are conducting a two-part study to (1) quantify winter litterfall rates in relation to canopy cover and local tree spacing, and (2) to determine the effects of litterfall density on melt rates. We predicted litterfall will be greatest in tree clumps, less near individual trees, and least in canopy openings; and that snow melt rates will increase with litter inputs, but potentially decrease at very high litterfall rates due to an insulation effect. The research takes place at Lubrecht Experimental Forest, at 1260 m of elevation. To quantify litterfall rates we deployed litter traps (1 m2) beneath six randomly selected tree clumps, individual trees, and canopy openings (n = 18 traps total). Traps will be collected after melting is complete and litter weighed. We are using a litter addition experiment (randomized block design) to investigate litterfall effects on snow attributes. Experimental blocks are placed in large canopy openings to limit natural litter inputs. Four litter addition amounts (0.1 kg/m2, 0.4 kg/m2, 1 kg/m2, and 4 kg/m2) or a control treatment are applied at random to 1 m2 plots, replicated in nine blocks. During melt season we will measure snow depth, snow water equivalent, albedo, percent snow coverage, and date of snow disappearance in each plot. The results of this research will give land managers more information on how changes to forest canopy cover, and the resulting change in litter fall, will affect snowmelt. This will allow land managers to design forest thinning and restoration prescriptions with a better understanding of the effects on water yield

Intra-abdominal hypertension due to heparin - induced retroperitoneal hematoma in patients with ventricle assist devices: report of four cases and review of the literature

<p>Abstract</p> <p>Introduction</p> <p>Elevated intra-abdominal pressure (IAP) has been identified as a cascade of pathophysiologic changes leading in end-organ failure due to decreasing compliance of the abdomen and the development of abdomen compartment syndrome (ACS). Spontaneous retroperitoneal hematoma (SRH) is a rare clinical entity seen almost exclusively in association with anticoagulation states, coagulopathies and hemodialysis; that may cause ACS among patients in the intensive care unit (ICU) and if treated inappropriately represents a high mortality rate.</p> <p>Case Presentation</p> <p>We report four patients (a 36-year-old Caucasian female, a 59-year-old White-Asian male, a 64-year-old Caucasian female and a 61-year-old Caucasian female) that developed an intra-abdominal hypertension due to heparin-induced retroperitoneal hematomas after implantation of ventricular assist devices because of heart failure. Three of the patients presented with dyspnea at rest, fatigue, pleura effusions in chest XR and increased heart rate although b-blocker therapy. A 36-year old female (the forth patient) presented with sudden, severe shortness of breath at rest, 10 days after an "acute bronchitis". At the time of the event in all cases international normalized ratio (INR) was <3.5 and partial thromboplastin time <65 sec. The patients were treated surgically, the large hematomas were evacuated and the systemic manifestations of the syndrome were reversed.</p> <p>Conclusion</p> <p>Identifying patients in the ICU at risk for developing ACS with constant surveillance can lead to prevention. ACS is the natural progression of pressure-induced end-organ changes and develops if IAP is not recognized and treated in a timely manner. Failure to recognize and appropriately treat ACS is fatal while timely intervention - if indicated - is associated with improvements in organ function and patient survival. Means for surgical decision making are based on clinical indicators of adverse physiology, rather than on a single measured parameter.</p

Reduced fire severity offers near-term buffer to climate-driven declines in conifer resilience across the western United States

Increasing fire severity and warmer, drier postfire conditions are making forests in the western United States (West) vulnerable to ecological transformation. Yet, the relative importance of and interactions between these drivers of forest change remain unresolved, particularly over upcoming decades. Here, we assess how the interactive impacts of changing climate and wildfire activity influenced conifer regeneration after 334 wildfires, using a dataset of postfire conifer regeneration from 10,230 field plots. Our findings highlight declining regeneration capacity across the West over the past four decades for the eight dominant conifer species studied. Postfire regeneration is sensitive to high-severity fire, which limits seed availability, and postfire climate, which influences seedling establishment. In the near-term, projected differences in recruitment probability between low- and high-severity fire scenarios were larger than projected climate change impacts for most species, suggesting that reductions in fire severity, and resultant impacts on seed availability, could partially offset expected climate-driven declines in postfire regeneration. Across 40 to 42% of the study area, we project postfire conifer regeneration to be likely following low-severity but not high-severity fire under future climate scenarios (2031 to 2050). However, increasingly warm, dry climate conditions are projected to eventually outweigh the influence of fire severity and seed availability. The percent of the study area considered unlikely to experience conifer regeneration, regardless of fire severity, increased from 5% in 1981 to 2000 to 26 to 31% by mid-century, highlighting a limited time window over which management actions that reduce fire severity may effectively support postfire conifer regeneration. © 2023 the Author(s)

Online chemical adsorption studies of Hg, Tl, and Pb on SiO2 and Au surfaces in preparation for chemical investigations on Cn, Nh, and Fl at TASCA

Online gas-solid adsorption studies with single-atom quantities of Hg, Tl, and Pb, the lighter homologs of the superheavy elements (SHE) copernicium (Cn, Z =112), nihonium (Nh, Z =113), and flerovium (Fl, Z =114), were carried out using short-lived radioisotopes. The interaction with Au and SiO 2 surfaces was studied and the overall chemical yield was determined. Suitable radioisotopes were produced in fusion-evaporation reactions, isolated in the gas-filled recoil separator TASCA, and flushed rapidly to an adjacent setup of two gas chromatography detector arrays covered with SiO 2 (first array) and Au (second array). While Tl and Pb adsorbed on the SiO 2 surface, Hg interacts only weakly and reached the Au-covered array. Our results contribute to elucidating the influence of relativistic effects on chemical properties of the heaviest elements by providing experimental data on these lighter homologs

Biomass offsets little or none of permafrost carbon release from soils, streams, and wildfire : an expert assessment

As the permafrost region warms, its large organic carbon pool will be increasingly vulnerable to decomposition, combustion, and hydrologic export. Models predict that some portion of this release will be offset by increased production of Arctic and boreal biomass; however, the lack of robust estimates of net carbon balance increases the risk of further overshooting international emissions targets. Precise empirical or model-based assessments of the critical factors driving carbon balance are unlikely in the near future, so to address this gap, we present estimates from 98 permafrost-region experts of the response of biomass, wildfire, and hydrologic carbon flux to climate change. Results suggest that contrary to model projections, total permafrost-region biomass could decrease due to water stress and disturbance, factors that are not adequately incorporated in current models. Assessments indicate that end-of-the-century organic carbon release from Arctic rivers and collapsing coastlines could increase by 75% while carbon loss via burning could increase four-fold. Experts identified water balance, shifts in vegetation community, and permafrost degradation as the key sources of uncertainty in predicting future system response. In combination with previous findings, results suggest the permafrost region will become a carbon source to the atmosphere by 2100 regardless of warming scenario but that 65%-85% of permafrost carbon release can still be avoided if human emissions are actively reduced.Peer reviewe

Greenhouse treatments before planting enhance ponderosa pine reforestation success

Global environmental change has increasingly negative direct and indirect effects on forests. Indirectly, hotter and drier conditions make fires more frequent and more severe. Large patches of stand-replacing fire can result in forest loss by killing resilient adult trees and thus limiting seed sources at the site. Even if seeds are available, hotter and drier conditions also directly limit seedling establishment post-fire, especially if there was significant adult tree mortality and thus less canopy shade. Combined, the direct and indirect effects of global environmental change threaten western USA forests, and reforestation is common practice to mitigate ecosystem change. While standard operating procedures for reforestation are informed by decades of research and are necessities for coordinating planting, recent plant ecophysiological research suggests a revision may increase seedling drought tolerance, survival, and post-fire restoration success. Two key steps in the reforestation pipeline, freezer and cooler storage of the seedlings, likely reduce plant carbohydrate storage. This is concerning because reduced carbohydrate storage decreases seedling drought tolerance in several woody species. Generally, carbohydrate-depleted plants die more frequently and faster under droughts. In summer 2021, I investigated whether manipulations to increase seedling carbohydrate storage prior to planting improve conifer seedling drought tolerance, survival, and post-fire restoration success. I grew ponderosa pine seedlings in a greenhouse for three weeks in full light (“light seedlings”) or 3% light (“shade seedlings”) to elevate or further decrease, respectively, carbohydrate storage before planting. A control group of seedlings were subjected to standard reforestation procedures (“control seedlings”; no greenhouse treatment). I planted seedlings in early May and monitored them throughout the following summer and fall. Overall, my preliminary results suggest that greenhouse light treatments, intended to increase carbohydrate storage before planting, improved conifer seedling water relations and overall health relative to shade or control treatments. Specifically, I found that the greenhouse light treatment resulted in less needle dieback, more root biomass, less drought stress, and improved survival when compared to shade and control treatments in the field. These results suggest that changes to reforestation procedures will improve reforestation outcomes in a hotter, drier world of the future. Producing more resilient, drought- and heat-tolerant conifer seedlings is critical for cost-efficiently restoring western USA forests post-fire