142 research outputs found
Measuring soil frost depth in forest ecosystems with ground penetrating radar
Soil frost depth in forest ecosystems can be variable and depends largely on early winter air temperaturesand the amount and timing of snowfall. A thorough evaluation of ecological responses to seasonallyfrozen ground is hampered by our inability to adequately characterize the frequency, depth, durationand intensity of soil frost events. We evaluated the use of ground penetrating radar to nondestructivelydelineate soil frost under field conditions in three forest ecosystems. Soil frost depth was monitoredperiodically using a 900 MHz antenna in South Burlington, Vermont (SB), Sleepers River Watershed,North Danville, Vermont (SR) and Hubbard Brook Experimental Forest, New Hampshire (HBEF) duringwinter 2011–2012 on plots with snow and cleared of snow. GPR-based estimates were compared to datafrom thermistors and frost tubes, which estimate soil frost depth with a color indicating solution. In theabsence of snow, frost was initially detected at a depth of 8–10 cm. Dry snow up to 35 cm deep, enhancednear-surface frost detection, raising the minimum frost detection depth to 4–5 cm. The most favorablesurface conditions for GPR detection were bare soil or shallow dry snow where frost had penetrated to theminimum detectable depth. Unfavorable conditions included: standing water on frozen soil, wet snow,thawed surface soils and deep snow pack. Both SB and SR were suitable for frost detection most of thewinter, while HBEF was not. Tree roots were detected as point reflections and were readily discriminatedfrom continuous frost reflections. The bias of GPR frost depth measurements relative to thermistors wassite dependent averaging 0.1 cm at SB and 1.1 cm at SR, and was not significantly different than zero. Whenseparated by snow manipulation treatment at SR, overestimation of soil frost depth (5.5 cm) occurredon plots cleared of snow and underestimation (−1.5 cm) occurred on plots with snow. Despite somelimitations posed by site and surface suitability, GPR could be useful for adding a spatial component topre-installed soil frost monitoring networks
Asbestos Burden Predicts Survival in Pleural Mesothelioma
Background: Malignant pleural mesothelioma (MPM) is a rapidly fatal asbestos-associated malignancy with a median survival time of < 1 year following diagnosis. Treatment strategy is determined in part using known prognostic factors. Objective: The aim of this study was to examine the relationship between asbestos exposure and survival outcome in MPM in an effort to advance the understanding of the contribution of asbestos exposure to MPM prognosis. Methods: We studied incident cases of MPM patients enrolled through the International Mesothelioma Program at Brigham and Women’s Hospital in Boston, Massachusetts, using survival follow-up, self-reported asbestos exposure (n = 128), and a subset of cases (n = 80) with quantitative asbestos fiber burden measures. Results: Consistent with the established literature, we found independent, significant associations between male sex and reduced survival (p 1,099), suggested a survival duration association among these groups (p = 0.06). After adjusting for covariates in a Cox model, we found that patients with a low asbestos burden had a 3-fold elevated risk of death compared to patients with a moderate fiber burden [95% confidence interval (CI), 0.95–9.5; p = 0.06], and patients with a high asbestos burden had a 4.8-fold elevated risk of death (95% CI, 1.5–15.0; p < 0.01) versus those with moderate exposure. Conclusion: Our data suggest that patient survival is associated with asbestos fiber burden in MPM and is perhaps modified by susceptibility
The Effects of 11 Yr of CO2 Enrichment on Roots in a Florida Scrub-Oak Ecosystem
Uncertainty surrounds belowground plant responses to rising atmospheric CO2 because roots are difficult to measure, requiring frequent monitoring as a result of fine root dynamics and long-term monitoring as a result of sensitivity to resource availability. We report belowground plant responses of a scrub-oak ecosystem in Florida exposed to 11yr of elevated atmospheric CO2 using open-top chambers. We measured fine root production, turnover and biomass using minirhizotrons, coarse root biomass using ground-penetrating radar and total root biomass using soil cores. Total root biomass was greater in elevated than in ambient plots, and the absolute difference was larger than the difference aboveground. Fine root biomass fluctuated by more than a factor of two, with no unidirectional temporal trend, whereas leaf biomass accumulated monotonically. Strong increases in fine root biomass with elevated CO2 occurred after fire and hurricane disturbance. Leaf biomass also exhibited stronger responses following hurricanes. Responses after fire and hurricanes suggest that disturbance promotes the growth responses of plants to elevated CO2. Increased resource availability associated with disturbance (nutrients, water, space) may facilitate greater responses of roots to elevated CO2. The disappearance of responses in fine roots suggests limits on the capacity of root systems to respond to CO2 enrichment
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Surface-based GPR underestimates below-stump root biomass
Aims:
While lateral root mass is readily detectable with ground penetrating radar (GPR), the roots beneath a tree (below-stump) and overlapping lateral roots near large trees are problematic for surface-based antennas operated in reflection mode. We sought to determine if tree size (DBH) effects GPR root detection proximal to longleaf pine (Pinus palustris Mill) and if corrections for could be applied to stand-level estimates of root mass.
Methods:
GPR (1500 MHz) was used to estimate coarse root mass proximal to 33 longleaf pine trees and compared to the amount of biomass excavated from pits proportional in area to tree basal diameter. Lateral roots were excavated to a depth of 1 m and taproots were excavated in their entirety.
Results:
GPR underestimated longleaf pine below-stump mass and the magnitude of the underestimation increased with tree DBH. Non-linear regressions between GPR estimated root mass/excavated root mass and tree diameter at breast height (DBH) were highly significant for both below-stump (lateral + taproot) root mass (p < 0.0001, R² 0.77) and lateral coarse root mass (p < 0.0001, R² 0.65).
Conclusions:
GPR underestimates root mass proximal to trees, and this needs to be accounted for to accurately estimate stand-level belowground biomass.Keywords: GPR,
Longleaf pine,
Root mass,
Lateral root,
Below-stump,
Pinus palustris,
taprootThis is the publisher’s final pdf. The article is copyrighted by Springer and published for the Royal Netherlands Society of Agricultural Science. It can be found at: http://link.springer.com/journal/1110
Attenuation of lung fibrosis in mice with a clinically relevant inhibitor of glutathione-S-transferase π
Idiopathic pulmonary fibrosis (IPF) is a debilitating lung disease characterized by excessive collagen production and fibrogenesis. Apoptosis in lung epithelial cells is critical in IPF pathogenesis, as heightened loss of these cells promotes fibroblast activation and remodeling. Changes in glutathione redox status have been reported in IPF patients. S-glutathionylation, the conjugation of glutathione to reactive cysteines, is catalyzed in part by glutathione-S-transferase π (GSTP). To date, no published information exists linking GSTP and IPF to our knowledge. We hypothesized that GSTP mediates lung fibrogenesis in part through FAS S-glutathionylation, a critical event in epithelial cell apoptosis. Our results demonstrate that GSTP immunoreactivity is increased in the lungs of IPF patients, notably within type II epithelial cells. The FAS-GSTP interaction was also increased in IPF lungs. Bleomycin- and AdTGFβ-induced increases in collagen content, α-SMA, FAS S-glutathionylation, and total protein S-glutathionylation were strongly attenuated in Gstp(–/–) mice. Oropharyngeal administration of the GSTP inhibitor, TLK117, at a time when fibrosis was already apparent, attenuated bleomycin- and AdTGFβ-induced remodeling, α-SMA, caspase activation, FAS S-glutathionylation, and total protein S-glutathionylation. GSTP is an important driver of protein S-glutathionylation and lung fibrosis, and GSTP inhibition via the airways may be a novel therapeutic strategy for the treatment of IPF
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Modeling the effects of forest management on in situ and ex situ longleaf pine forest carbon stocks
Assessment of forest carbon storage dynamics requires a variety of techniques including simulation models. We developed a hybrid model to assess the effects of silvicultural management systems on carbon (C) budgets in longleaf pine (Pinus palustris Mill.) plantations in the southeastern U.S. To simulate in situ C pools, the model integrates a growth and yield model with species-specific allometric and biometric equations and explicitly accounts for the impacts of both thinning and prescribed fire. To estimate the ex situ C pool, the model used the outputs of merchantable products from the growth and yield model with current values of forest product conversion efficiencies and forest product decay rates. The model also accounts for C emissions due to transportation and silvicultural activities. Site productivity (site quality) was the major factor controlling stand C density followed by rotation length. Thinning reduced C sequestration, as the slow growth rate of longleaf pine reduced the potential of C sequestration in forest products. Prescribed burning reduced average C stock by about 16–19%, with the majority of the reduction in the forest floor. In a comparison of longleaf pine C dynamics with slash pine (Pinus elliottii Engelm.), both species reached a similar average C stock at age 75 years, but when averaged across the whole rotation, slash pine sequestered more C. Nevertheless, for medium quality sites, C sequestration was similar between thinned 75-year rotation longleaf pine and unthinned 25-year rotation slash pine. This longleaf pine plantation C sequestration model, based on empirical and biological relationships, provides an important new tool for developing testable research hypotheses, estimating C stocks for regional assessments or C credit verification, and for guiding future longleaf pine management.Keywords: Prescribed burning, Carbon stock modeling, Pinus palustris plantations, Silviculture, Biomas
Folliculin mutations are not associated with severe COPD
<p>Abstract</p> <p>Background</p> <p>Rare loss-of-function folliculin (<it>FLCN</it>) mutations are the genetic cause of Birt-Hogg-Dubé syndrome, a monogenic disorder characterized by spontaneous pneumothorax, fibrofolliculomas, and kidney tumors. Loss-of-function folliculin mutations have also been described in pedigrees with familial spontaneous pneumothorax. Because the majority of patients with folliculin mutations have radiographic evidence of pulmonary cysts, folliculin has been hypothesized to contribute to the development of emphysema.</p> <p>To determine whether folliculin sequence variants are risk factors for severe COPD, we genotyped seven previously reported Birt-Hogg-Dubé or familial spontaneous pneumothorax associated folliculin mutations in 152 severe COPD probands participating in the Boston Early-Onset COPD Study. We performed bidirectional resequencing of all 14 folliculin exons in a subset of 41 probands and subsequently genotyped four identified variants in an independent sample of345 COPD subjects from the National Emphysema Treatment Trial (cases) and 420 male smokers with normal lung function from the Normative Aging Study (controls).</p> <p>Results</p> <p>None of the seven previously reported Birt-Hogg-Dubé or familial spontaneous pneumothorax mutations were observed in the 152 severe, early-onset COPD probands. Exon resequencing identified 31 variants, including two non-synonymous polymorphisms and two common non-coding polymorphisms. No significant association was observed for any of these four variants with presence of COPD or emphysema-related phenotypes.</p> <p>Conclusion</p> <p>Genetic variation in folliculin does not appear to be a major risk factor for severe COPD. These data suggest that familial spontaneous pneumothorax and COPD have distinct genetic causes, despite some overlap in radiographic characteristics.</p
Modelling the limits on the response of net carbon exchange to fertilization in a south-eastern pine forest
Using a combination of model simulations and detailed measurements at a hierarchy of scales conducted at a sandhills forest site, the effect of fertilization on net ecosystem exchange ( NEE ) and its components in 6-year-old Pinus taeda stands was quantified. The detailed measurements, collected over a 20-d period in September and October, included gas exchange and eddy covariance fluxes, sampled for a 10-d period each at the fertilized stand and at the control stand. Respiration from the forest floor and above-ground biomass was measured using chambers during the experiment. Fertilization doubled leaf area index (LAI) and increased leaf carboxylation capacity by 20%. However, this increase in total LAI translated into an increase of only 25% in modelled sunlit LAI and in canopy photosynthesis. It is shown that the same climatic and environmental conditions that enhance photosynthesis in the September and October periods also cause an increase in respiration The increases in respiration counterbalanced photosynthesis and resulted in negligible NEE differences between fertilized and control stands. The fact that total biomass of the fertilized stand exceeded 2·5 times that of the control, suggests that the counteracting effects cannot persist throughout the year. In fact, modelled annual carbon balance showed that gross primary productivity ( GPP ) increased by about 50% and that the largest enhancement in NEE occurred in the spring and autumn, during which cooler temperatures reduced respiration more than photosynthesis. The modelled difference in annual NEE between fertilized and control stands (approximately 200 1;g 2;C 3;m −2 y −1 ) suggest that the effect of fertilization was sufficiently large to transform the stand from a net terrestrial carbon source to a net sink.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73712/1/j.1365-3040.2002.00896.x.pd
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