398 research outputs found
Diverging temperature response of tree stem CO2 release under dry and wet season conditions in a tropical montane moist forest
No full textIt is commonly presumed that plant respiratory CO2 release increases with increasing temperature. However, we report on very contrasting stem CO2 release (R (S))-temperature relationships of trees in a species-rich tropical montane forest of southern Ecuador under dry and wet season conditions. Rates of R (S) were low and completely uncoupled from the dial temperature regime during the humid season. In contrast, during the dry season, R (S) was generally higher and temperature sensitivity of R (S) differed greatly in degree and even in the direction of response, indicating that temperature might not be the only determinant of R (S). In order to explain the heterogeneity of R (S), we related R (S) to vapour pressure deficit, wind speed and solar radiation as important abiotic drivers influencing transpiration and photosynthesis. Stepwise multiple regression analyses with these meteorological predictors either were biased by high collinearity of the independent variables or could not enhance the ability to explain the variability of R (S). We assume maintenance respiration to dominate under humid conditions unfavourable for energy acquisition of the tree, thus explaining the pronounced uncoupling of R (S) from atmospheric parameters. In contrast, the drier and hotter climate of the dry season seems to favour R (S) via enhanced assimilatory substrate delivery and stem respiratory activity as well as elevated xylem sap CO2 imports with increased transpiration. In addition, tree individual differences in the temperature responses of R (S) may mirror diverging climatic adaptations of co-existing moist forest tree species which have their distribution centre either at higher or lower elevations
Elevational change in woody tissue CO2 efflux in a tropical mountain rain forest in southern Ecuador
No full textMuch uncertainty exists about the magnitude of woody tissue respiration and its environmental control in highly diverse tropical moist forests. In a tropical mountain rain forest in southern Ecuador, we measured the apparent diurnal gas exchange of stems and coarse roots (diameter 1-4 cm) of trees from representative families along an elevational transect with plots at 1050, 1890 and 3050 m a.s.1. Mean air temperatures were 20.8, 17.2 and 10.6 degrees C, respectively. Stem and root CO2 efflux of 13 to 21 trees per stand from dominant families were investigated with an open gas exchange system while stand microclimate was continuously monitored. Substantial variation in respiratory activity among and within species was found at all sites. Mean daily CO2 release rates from stems declined 6.6-fold from 1.38 mu mol m(-2) s(-1) at 1050 m to 0.21 mu mol m(-2) s(-1) at 3050 m. Mean daily CO2 release from coarse roots decreased from 0.35 to 0.20 mu mol m(-2) s(-1) with attitude, but the differences were not significant. There was, thus, a remarkable shift from a high ratio of stem to coarse root respiration rates at the lowest elevation to an apparent equivalence of stem and coarse root CO2 efflux rates at the highest elevation. We conclude that stem respiration, but not root respiration, greatly decreases with elevation in this transect, coinciding with a substantial decrease in relative stem diameter increment and a large increase in fine and coarse root biomass production with elevation
Carbon Turnover and Carbon‐13 Natural Abundance under Land Use Change in Semiarid Savanna Soils of La Pampa, Argentina
No full textHalf-lives of 50 to 1.00 yr have been reported for native soil C in temperate Mollisols taken under cultivation, whereas some C fractions have shown mean residence times of hundreds of years. In the Tropics, C turnover is much more rapid. This lower C stability may be attributable to climate or to a mineral suite with low C stabilization potential typical of many tropical soils. We present data on the mineralization and accretion pattern of organic C under land use conversion in illitic loessial loams of the semiarid, warm temperate Province of La Pampa, Argentina. These soils should have a low C stabilization potential, and the semiarid temperate climate should provide for relatively slow turnover compared with tropical conditions. Using C-13-natural abundance and soil fractionation, we determined soil C derived from C3 and C4 plants under land use changes between native Calden savannah, pastures, and arable fields, specifically: (i) the conversion of C3 natural savannah to agriculture that includes (C4) maize in the rotation, (ii) the conversion of a 40-yr-old C4 pasture into arable land under C3 crops, and (iii) the reclamation of highly degraded C3 cultivated land with C4 pastures. Although none of the land cover changes represented 100% conversions between plants of C4 and C3 metabolism, C turnover could still be determined. All sites provided evidence for rapid C losses with C half-lives just above 10 yr and no evidence for long-term stabilized C in any soil fractions. Soil under long-term pasture or the natural vegetation of the region, with initial C contents between 24 and 33 mg C g(-1) bulk soil, lost 33 to 57% of this original bulk soil C within 12 to 18 yr of continuous cultivation. On degraded soils under restoration with C4 pasture, C accretion was also rapid but leveled off well below the original C levels. Theses results provide evidence for potentially irreversible soil degradation and corroborate local practical experience that these temperate, coarse-textured, illitic soils are highly susceptible to degradation and should be managed carefully
Patterns of wood carbon dioxide efflux across a 2,000-m elevation transect in an Andean moist forest
No full textDuring a 1-year measurement period, we recorded the CO(2) efflux from stems (R (S)) and coarse woody roots (R (R)) of 13-20 common tree species at three study sites at 1,050, 1,890 and 3,050 m a.s.l. in an Andean moist forest. The objective of this work was to study elevation changes of woody tissue CO(2) efflux and the relationship to climate variation, site characteristics and growth. Furthermore, we aim to provide insights into important respiration-productivity relationships of a little studied tropical vegetation type. We expected R (S) and R (R) to vary with dry and humid season conditions. We further expected R (S) to vary more than R (R) due to a more stable soil than air temperature regime. Seasonal variation in woody tissue CO(2) efflux was indeed mainly attributable to stems. At the same time, temperature played only a small role in triggering variations in R (S). At stand level, the ratio of C release (g C m(-2) ground area year(-1)) between stems and roots varied from 4:1 at 1,050 m to 1:1 at 3,050 m, indicating the increasing prevalence of root activity at high elevations. The fraction of growth respiration from total respiration varied between 10 (3,050 m) and 14% (1,050 m) for stems and between 5 (1,050 m) and 30% (3,050 m) for roots. Our results show that respiratory activity and hence productivity is not driven by low temperatures towards higher elevations in this tropical montane forest. We suggest that future studies should examine the limitation of carbohydrate supply from leaves as a driver for the changes in respiratory activity with elevation
Reply to Crispin Wright and Richard Zach
No full textI am very grateful to Crispin Wright and Richard Zach for their thoughtful and penetrating comments on my book, The Boundary Stones of Thought (henceforth BST; unadorned page numbers below refer to this volume). The author of any reasonably long philosophical work will feel more confident in some of his claims than in others, and in studying Wright’s and Zach’s essays I have been struck by how often they home in on elements which gave me most trouble when writing the book and of which I was least certain having finished it. While that makes the job of defending my position harder, it is in one important respect comforting, for it suggests that the book was sufficiently clearly written to have enabled this meeting of minds. In a symposium of this kind, there can be few things more depressing than for the author to have to write: ‘X attributes to me such-and-such an argument, but what I really meant was instead this’. Thankfully, very little of that will be needed here.
While Wright and Zach focus on different parts of BST (Zach on Chapters 6–8, Wright on Chapters 9 and 10), there are many thematic connections between their commentaries. Rather than give separate replies, then, I shall address the relevant topics in the order in which they appear in my book, dealing (as I hope) with all their main points as I go
Zach\u27s News
No full textVideo from our Farm to Table Dinner Scholar Lions in London Story of author of Statesboro Blues\u27 comes home EBSCO Changing Default Result Sort Orde
The new test for dishonesty in criminal law – lessons from the courts of equity?
No full textThe Supreme Court decision in Ivey v Genting Casinos rejected the two stage test for dishonesty set out in R v Ghosh and replaced it with a single, objective test which transcends both criminal and civil law. This article asks whether it was correct to create a single test for dishonesty and in doing so, what role will subjectivity now play in the criminal law’s application of what is considered dishonest behaviour. Historically, the civil courts have beset with confusion as to the role of subjectivity in the test for dishonesty in light of Royal Brunei Airlines v Tan. The author will consider whether lessons can be learned from the civil courts and whether similar problems will trouble criminal law, particularly in light of criticism of the Ivey test and a preference, by some, for subjectivity to play a greater role in criminal liability for theft and other dishonesty offences
Development of composite calibration standard for quantitative NDE by ultrasound and thermography
No full textInspection of aircraft components for damage utilizing ultrasonic Non-Destructive Evaluation (NDE) is a time intensive endeavor. Additional time spent during aircraft inspections translates to added cost to the company performing them, and as such, reducing this expenditure is of great importance. There is also great variance in the calibration samples from one entity to another due to a lack of a common calibration set. By characterizing damage types, we can condense the required calibration sets and reduce the time required to perform calibration while also providing procedures for the fabrication of these standard sets. We present here our effort to fabricate composite samples with known defects and quantify the size and location of defects, such as delaminations, and impact damage. Ultrasonic and Thermographic images are digitally enhanced to accurately measure the damage size. Ultrasonic NDE is compared with thermography.This proceeding may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing.
This proceeding appeared in Dayal, Vinay, Zach G. Benedict, Nishtha Bhatnagar, and Adam G. Harper. "Development of composite calibration standard for quantitative NDE by ultrasound and thermography." In AIP Conference Proceedings, vol. 1949, no. 1, p. 060006. AIP Publishing LLC, 2018, and may be found at
DOI: 10.1063/1.5031552.
Copyright 2018 The Author(s).
Posted with permission
Colorado Water Institute, FY2008/2009 activities and impact report
No full textAssembled and reviewed by: Reagan Waskom, Nancy Grice, Zach Hittle
Springdale, Leavenworth County
No full textBaker, Zach, “Springdale, Leavenworth County,” Chapman Center Research Collections, https://ccrsresearchcollections.omeka.net/items/show/3.The author describes the life of an early Irish Catholic settlement in eastern Kansas. Originally a Quaker community, Irish immigration "exploded" there just after the Civil War, eventually stamping the town with a particular religious culture. After railroads made the Fort Riley mail road obsolete, Springdale declined. St. Thomas Catholic Church was a vital center for decades
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