Mean Mass Loss Research Articles

Coupling a CFD code with a solid-phase combustion model

A one-dimensional and unsteady model for the gasification/combustion of thick wood is developed and coupled with a two-dimensional CFD model for the gaseous phase processes, solved by the commercial code CFX4.4. Simulations of the combustion of single wood logs, as obtained with the coupled solid- and gas-phase models and with a solid-phase model alone, are compared with experimental measurements. Acceptable agreement is obtained in the first case, whereas the solid-phase model alone highly underestimates the conversion time and overestimates the mean mass loss rates. A two-dimensional formulation of the equations for the solid-phase does not affect significantly the global parameters.

Reconciling Change in Oi‐Horizon Carbon‐14 with Mass Loss for an Oak Forest

First‐year litter decomposition was estimated for an upland‐oak (Quercus spp.) forest ecosystem using enrichment or dilution of the 14C‐signature of the Oi‐horizon. These isotopically based mass‐loss estimates were contrasted with measured mass‐loss rates from past litterbag studies. Mass‐loss derived from changes in the 14C‐signature of the Oi‐horizon suggested mean mass loss over 9 mo of 45%, which was higher than the corresponding 9‐mo rate extrapolated from litterbag studies (∼35%). Greater mass loss was expected from the isotopic approach because litterbags are known to limit mass loss processes driven by soil macrofauna (e.g., fragmentation and comminution). Although the 14C‐isotope approach offers the advantage of being a non‐invasive method, it exhibited high variability that undermined its utility as an alternative to routine litterbag mass loss methods. However, the 14C approach measures the residence time of C in the leaf litter, rather than the time it takes for leaves to disappear; hence radiocarbon measures reflect C immobilization and recycling in the microbial pool, and do not necessarily replicate results from litterbag mass loss. The commonly applied two‐compartment isotopic mixing model was appropriate for estimating decomposition from isotopic enrichment of near‐background soils, but it produced divergent results for isotopic dilution of a multi‐layered system with litter cohorts having independent 14C‐signatures. This discrepancy suggests that cohort‐based models are needed to adequately capture the complex processes involved in C transport associated with litter mass‐loss. Such models will be crucial for predicting intra‐ and interannual differences in organic horizon decomposition driven by scenarios of climatic change.

Wood Decomposition of Cyrilla racemiflora (Cyrillaceae) in Puerto Rican Dry and Wet Forests: A 13‐year Case Study1

ABSTRACTWe studied the decomposition of Cyrilla racemiflora logs over a 13‐yr period in tropical dry and wet forests in Puerto Rico. The mean mass loss, ratio of soft to hard wood, nutrient concentrations, and the diversity of wood‐inhabiting organisms were greater in logs decomposing in the dry forest than in the wet forest. Termites were also more abundant in the logs collected from the tropical dry forest than the tropical wet forest. High moisture content and a low animal diversity on the logs in the wet forest seem to retard wood decay in this habitat. Wood decay rates in the tropical dry forest can be related to the high diversity of species and functional groups of wood‐inhabiting organisms.

REPEATED CAPTURE OF BEACH MICE (PEROMYSCUS POLIONOTUS PHASMA AND P. P. NIVEIVENTRIS) REDUCES BODY MASS

Body mass is commonly used as an indicator of habitat quality and body condition in small-mammal populations. We examined the effects of consecutive days of livetrapping on body mass of 2 federally listed subspecies of beach mice on the eastern coast of Florida: the Anastasia Island beach mouse (Peromyscus polionotus phasma) and the southeastern beach mouse (P. p. niveiventris). Mean mass loss (approximately 0.5 g/recaptured day) was additive and occurred for Anastasia Island beach mice over 2 consecutive days and for southeastern beach mice over 3 consecutive days. Researchers should exercise caution when their trapping protocols call for consecutive nights of trapping.

Effects of nonuniform heating and thermocapillarity in evaporating films falling down an inclined plate

The dynamics of a thin evaporating liquid film falling down an inclined plate is studied in the cases of both uniformly and nonuniformly heated plates. The film flow is influenced by gravity, mean surface tension, thermocapillary force and mass loss. The dynamics of the two-dimensional evaporating film is studied by the use of long-wavelength theory. Numerical solution of the evolution equation indicates that the evaporation has a strong stabilizing effect on the film instability and that a sequence of instability, stability and then instability of the falling film during its evaporation exists. The effect of nonuniform heating is dominant prior to film disappearance and it enforces film rupture. Due to the joint action of thermocapillarity and evaporating mass loss, the film evolution exhibits the formation of multi-hump structures, the downstream propagation of which is suppressed. When the nonuniformities in the imposed temperature differences are increased, large deformations of the liquid-vapor interface occur that lead to an enhancement of the heat transfer processes.

Slow initial decomposition and fungal colonization of pine branches in a nutrient-rich lowland stream

Mass loss, fungal colonization, and chemical changes of submerged pine (Pinus sylvestris) branches were monitored in a nutrient-rich lowland stream. Branches retrieved from the stream were analyzed for water-soluble substances to assess mass loss by leaching. Concentrations of substances soluble in hot 1% NaOH were determined in order to detect changes in wood-tissue structure indicating microbial degradative activity, and fungal colonization was estimated as ergosterol concentration. Decomposition of the pine branches was slow, with a mean mass loss of 8.3% within 13 months and an overall decay coefficient, k, of 0.074·year–1. Concentrations of water-soluble substances in wood decreased from 2.8% to 1.7% after 5 weeks and in bark from 5.6% to 3.8% within 2 weeks. No further losses were noted, nor were significant changes observed in concentrations of substances soluble in hot dilute NaOH. Fungal biomass in bark increased within the first 5 weeks (14–69 µg ergosterol·g–1dry mass) but was invariably low in wood. These results indicate that decomposition of intact fully corticated pine branchwood in streams proceeds very slowly, with little fungal colonization and no notable changes in wood structure occurring after more than a year even when dissolved nutrients in stream water are readily available.

DECOMPOSITION PARAMETERS FOR STRAW EROSION CONTROL BLANKETS

Increased environmental concerns and regulations have mandated proper planning to control erosion and sediments from construction sites. A field experiment was conducted to evaluate decomposition rates of single- and double-layer straw erosion-control blankets and to estimate their surface decomposition parameter. Single (DS1, S1) and double (DS2, S2) layer applications of two common types of straw erosion-control blankets (DS150, S150) were used as treatments in the study. The netting material for DS150 was described as having the quality of degrading more quickly than that of S150. Using randomized block design, nine single- and double-layer applications of each material type were placed within plots of a freshly tilled Plano silt loam soil (fine-silty, mixed, mesic, Typic Argiudolls). Each corner was secured in place using U-shaped wires. Every two weeks, starting at week 2, a randomly designated sample of all treatment combinations was permanently removed and analyzed for mass loss. For the 14-week study period, average percent mass loss was significantly higher for treatment DS150 (40%) than for S150 (29%) at the 0.05 level. Within each erosion-control blanket of the same netting material, mean percent mass loss for a single layer was significantly greater (. = 0.05) than that for a double layer. Mean percent mass losses were 50%, 34%, 30%, and 24% in 14 weeks for DS1, S1, DS2, and S2, respectively. Material type (P < 0.0001), time (P < 0.0001), and their interaction (P < 0.0237) were statistically significant. The decay constant for winter wheat (p = 0.0175) in the RUSLE crop database was found to have adequately predicted observed decomposition for DS1 straw blanket. However, it overestimated decomposition rates for all other straw blankets.

Continuous and Surge Irrigation Effects on Hydraulic Parameters and Water Quality

Abstract Limited information exists on comparing the effect of continuous and surge irrigation on hydraulic parameters and water quality under border-strip irrigation in the Canadian Prairies. A site on a clay loam soil in southern Alberta was used to compare these two irrigation methods (three replicates) on plots seeded to barley (Hordeum vulgare) in 1996 and 1997. Irrigation was conducted on border-strip plots in July and August of each year. Irrigation hydraulic parameters, soil water content, chloride and sediment in runoff, chloride in suction lysimeters, soil and shallow groundwater, and the water table level were measured before and after irrigation. Surge irrigation significantly (P ≤ 0.10) reduced the following hydraulic parameters compared to continuous irrigation: irrigation water applied (129–304%), total surface runoff (93–257%), maximum outflow rate (25–146%), advance time to the end of the field (214–273%), total infiltration depth of water (135–390%), and total irrigation time. However, irrigation treatment had no significant effect on surface runoff and infiltration depth of water when expressed as a percentage of the total amount of irrigation water applied. Surge had little or no effect on the concentration, flow-weighted mean concentration (FWMC) and mass loss of chloride and sediment in runoff. The exceptions were in July 1996, where mass loss of chloride was 180% lower under surge; and in August 1997, where the concentration of chloride was 44% lower under surge. Irrigation method had little or no significant effect on the soil water content, concentration of chloride in suction lysimeters and groundwater, the total mass of chloride in the soil profile, and the water table level. However, there was a trend towards lower chloride values under continuous than surge irrigation in the lysimeters and soil, suggesting a potential for greater leaching under the former method. Although surge irrigation had little or no positive effect on water quality compared to continuous irrigation, surge is still the preferred irrigation method because of its many improvements in hydraulic parameters.

Decomposition of sun and shade leaves from three deciduous tree species, as affected by their chemical composition

Freshly fallen leaf litter from sweet chestnut (Castanea sativa Mill), oak (Quercus robur L.) and beech (Fagus sylvatica L.) trees were classified into sun, intermediate and shade leaf types and analysed for N, acid detergent fibre, holocellulose, and lignin. In addition, the sugar constituents of structural polysaccharides (mainly from hemicelluloses) were determined after trifluoracetic acid (TFA) hydrolysis, and the phenylpropanoid (PPD) derivatives of lignin after alkaline CuO oxidation. The litters were decomposed in laboratory microcosms for 2 years. Decomposition rates were initially rapid and then plateaued, but differences in mass losses for the leaf litter categories, and between the three species, were significant at 6, 12, 18 and 24 months. Mean mass losses after 24 months were 49.6% for chestnut, 40.4% for oak and 26.3% for beech. Mean losses for chestnut, oak and beech litter categories were 48.6%, 38.2% and 24.6%, respectively, for sun leaves, and 51.0%, 44.5% and 28.5%, respectively, for shade leaves. Initial lignin concentrations showed a negative correlation with mass losses over the first 6 months but initial acid detergent fibre was a better predictor of decomposition rates after 24 months. Within species, however, total extractable sugars and PPD concentrations reflected differences in decomposition rates between the different categories of leaf types. The analysis for specific carbohydrates and lignin derivatives improved the resolution of litter quality characterisation but did not explain the observed patterns of decomposition in long-term laboratory incubations. It is suggested that these may be affected by influence of the culture conditions on the composition of fungal communities.

Interactions between litter quality, decomposition and soil fertility: a laboratory study

Leaf litters from beech ( Fagus sylvatica L.) and oak ( Quercus robur L.) trees were collected from mixed, deciduous woodlands growing on three soil types that varied in mineral nutrient concentrations and N mineralisation potential. Litter quality, including %N, %Mn, %P, acid detergent fibre, cellulose, Klason lignin, phenylpropanoid constituents of lignin, hexose and pentose sugar (mainly from hemicelluloses) varied within species according to soil type. However, oak and beech showed the opposite responses to soil nutrient status for most of these variables. The litters were incubated in the laboratory for 12 months (at 18 °C and constant moisture) on beds of forest floor material from two soils of contrasting high nutrient material (HNM) or low nutrient material (LNM) nutrient status to investigate litter quality and substrate interactions. At 4, 8 and 12 months there were significant differences in mass losses from oak and beech litters from all sites, and for each litter type exposed to the HNM and LMN soils. At 12 months mean mass losses were higher for HNM treatment (38.7% oak, 27.8% beech) than for the LNM treatment (30.6% oak, 25.5% beech). However, the beech and oak litters from the different sites consistently responded in opposite ways on the same soil treatment reflecting site-related effects on litter quality. Initial concentration of Klason lignin was the best predictor for mass losses from litter species and litter types. Intra-specific variation in rates of litter decomposition of beech and oak litters from different sites, and differences in their interactions with the two forest floor materials, illustrate the complexities of proximate controls on decomposition that are often masked in system-level studies.

Gold fragmentation induced by stopped antiprotons

A natural gold target was irradiated with the antiproton beam from the low-energy antiproton ring at CERN. Antiprotons of $200\mathrm{MeV}/c$ momentum were stopped in a thick target, products of their annihilations on Au nuclei were detected using the off-line $\ensuremath{\gamma}$-ray spectroscopy method. In total, yields for 114 residual nuclei were determined, providing a dataset to deduce the complete mass and charge distribution of all products with $A\ensuremath{\gtrsim}20$ from a fitting procedure. The contribution of evaporation and fission decay modes to the total reaction cross section as well as the mean mass loss were estimated. The fission probability for Au absorbing antiprotons at rest was determined to be equal to $(3.8\ifmmode\pm\else\textpm\fi{}0.5)%,$ in good agreement with an estimation derived using other techniques. The mass-charge yield distribution was compared with the results obtained for proton and pion induced gold fragmentation. On average, the energy released in $\overline{p}$ annihilation is similar to that introduced by $\ensuremath{\approx}1\mathrm{GeV}$ protons. However, compared to proton bombardment products, the yield distribution of antiproton absorption residues in the $N\ensuremath{-}Z$ plane is clearly distinct. The data for antiprotons exhibit also a substantial influence of odd-even and shell effects.

Change in body mass associated with long-term fasting in a marine reptile: the case of green turtles (Chelonia mydas) at Ascension Island

Female green sea turtles (Chelonia mydas) nesting at Ascension Island (7°57'S, 14°22'W) in the middle of the Atlantic Ocean had a mean body mass (post oviposition) of 166.3 kg (range 107.5–243.5 kg, n = 119). Individuals lost mass slowly during the nesting season (mean mass loss 0.22 kg·d–1, n = 14 individuals weighed more than once). Gut-content analysis and behavioural observations indicated a lack of feeding. Females of equivalent-sized pinniped species that also do not feed while reproducing (nursing pups) on islands lose mass about 17 times faster. This comparatively low rate of mass loss by green turtles probably reflects their ectothermic nature and, consequently, their low metabolic rate. We estimate that a female turtle would lose only 19% of her body mass during the 143-day, 4400-km round trip from Brazil if she did not eat, laid 3 clutches of eggs, and lost 0.22 kg·d–1.

Genetic variation in the decay resistance of Scots pine wood against brown rot fungus

The role of genotype in the durability of Scots pine (Pinus sylvestris L.) wood against decay by brown rot fungus (Coniophora puteana (Schum. ex Fr.) Karst. (strain Bam EBW 15)) was studied in a laboratory test. The wood material was obtained from 32-year-old half-sib progenies of Scots pine. The increment core samples of sapwood and juvenile heartwood were decayed using a modification of the standardized EN 113 method. The mean densities of the sapwood and heartwood samples were 391 and 337 mg·cm–3, respectively, and the mean mass losses were 114 and 80 mg·cm–3, respectively. The additive genetic components were small compared with the total phenotypic variance, which resulted in small narrow-sense heritabilities in mass loss. The most marked feature was the wide phenotypic variation in mass loss observed in heartwood (range 199 mg·cm–3) compared with sapwood (range 72 mg·cm–3) samples. Low heritability, together with the relatively high coefficient of additive genetic variation (CVA) in heartwood mass loss, suggests that advances in breeding can only be made through intensive testing in the environments which the studied experiment represents.

Respiration from coarse wood litter in central Amazon forests

Respiration from coarse litter (trunks and large branches >10 cm diameter) was studied in central Amazon forests. Respiration ratesvaried over almost two orders of magnitude (1.003–0.014 µg Cg−1 C min−1, n = 61), and weresignificantly correlated with wood density (r2adj= 0.42), and moisture content (r2adj= 0.39). Additional samples taken from a nearby pasture indicatedthat wood moisture content was the most important factor controllingrespiration rates across sites (r2adj =0.65). Based on average coarse litter wood density and moisture content,the mean long-term carbon loss rate due to respiration was estimated tobe 0.13 yr−1 (range of 95% prediction interval(PI) = 0.11–0.15 yr−1). Comparing meanrespiration rate with mean mass loss (decomposition) rate from aprevious study, respiratory emissions to the atmosphere from coarselitter were predicted to be 76% (95% PI =65–88%) of total carbon loss, or about 1.9 (95% PI= 1.6–2.2) Mg C ha−1yr−1. Optimum respiration activity corresponded toabout 2.5 g H2O g−1 dry wood, and severelyrestricted respiration to < 0.5 g H2O g−1dry wood. Respiration from coarse litter in central Amazon forests iscomparable in magnitude to decomposing fine surface litter (e.g. leaves,twigs) and is an important carbon cycling component when characterizingheterotrophic respiration budgets and net ecosystem exchange(NEE).

Determination of gold alloy loss during the production of cast dental restorations.

Values for the loss of high gold content dental alloy during the fabrication of three types of cast dental restorations were determined. The mass changes measured were for the melting, casting and cleaning processes and the docking and laboratory finishing procedures involved in producing the final restoration. The casting yield from the alloy cast was also determined. Five Brisbane dental laboratories participated and 407 cast restorations were assessed. The mean mass loss for the melting and casting process was 0.109 g (SD 0.326) per cast restoration, and 0.827 per cent (SD 1.805) of the total mass of alloy melted. The data were analysed in four categories: alloy crowns, metal-ceramic crowns, metal-ceramic bridges, and combined. The mean total mass loss per restoration from docking and finishing for each of the four groups of cast dental restorations examined was 0.329 g, 0.350 g, 0.927 g and 0.363 g; 13.11, 28.30, 22.07 and 22.18 as a per cent of the mass of the docked casting respectively. The yield of casting masses from the alloy cast were 19.97, 9.11, 29.10 and 13.71 per cent respectively, with all differences significant at the 0.001 level. These values indicate that the recommendation for 50 per cent addition of new alloy for each cast is impractical. The wide spread of the data precludes the establishment of a precise agreed value between dentists and technicians for expected loss. However, the use of the median or mean would provide a value which might be an equitable indicator in the long term. Alternatively, working values can be developed for individual dentist/technician partnerships.

P4F14S - Isolation of multiple CYP4 sequences using degenerate primersin twoaustralian termites: Mastotermes darwiniensis and coptotermes acinaciformis

The solubility of permethrin in supercritical carbon dioxide (scCO2) was determined, with optimal solubility for the timber impregnation trial and the specific operating conditions examined occurring at 50 °C. Methanol as co-solvent improved solubility, but was not needed for timber impregnation. Eucalyptus obliqua heartwood (a refractory timber), Pinus radiata sapwood and P. radiata LVL were impregnated in a treatment cylinder, and their resistance to attack by termites was compared to that of material protected with standard permethrin treatments using light organic solvent preservative (LOSP). Termite field tests were conducted against Coptotermes acinaciformis and Mastotermes darwiniensis. The choice of solvent system did not affect permethrin efficacy in P. radiata sapwood against termites. P. radiata LVL specimens treated using scCO2 had slightly lower mean mass losses than those impregnated with LOSP, reflecting slightly higher permethrin uptakes in the former. E. obliqua heartwood was completely destroyed by M. darwiniensis when impregnated with LOSP, but was mostly sound when scCO2 was used. These results show that scCO2 did not alter the effectiveness of the insecticide, while giving the added benefit of allowing the impregnation of timbers previously considered refractory to treatment.

Microbial enzyme activities as indicators of organic matter processing rates in a Lake Erie coastal wetland

SUMMARY1. Particulate organic material (POM) is an important source of energy and nutrients in aquatic ecosystems. The decomposition of this material is typically studied using the litter bag technique. However, this method has inherent limitations that can preclude the estimation of in situ decomposition rates, especially for fine particles. In this study, we tried to circumvent these limitations through the use of enzymatic decomposition models (EDMs), which relate mass loss rates to lignocellulase activities. With this approach, we investigated the in situ processing of three size ranges of detritus in a Typha wetland.2. Litter was collected, dried and sorted into three size ranges [coarse (C) &gt; 4, medium (M) 0.5–4 and fine (F) 0.063–0.5 mm] and placed in litter bags that were attached to the sediment surface at two sites in a Typha wetland in May 1994. Over a 7‐month period, litter bags were collected and analysed for mass loss and the activities of six extracellular enzymes involved in the degradation of lignocellulose. In situ POM was collected concurrently, sorted into the same three size ranges and assayed for the same suite of enzymes. Additional cores were taken for the determination of organic matter standing stocks and particle size distribution.3. Mean mass loss rates for CPOM, MPOM and FPOM were ‐0.139, ‐0.073 and ‐0.053% day−1, respectively. Only CPOM rates were significantly different between sites. For CPOM and FPOM there were strong linear relationships between mass loss and cumulative enzyme activities; the mass loss data for MPOM were erratic and precluded the development of reliable enzyme models. EDMs for CPOM and FPOM were constructed from regressions relating mass loss to average cumulative lignocellulase activity, and used to estimate instantaneous in situ decomposition rates. These rates varied by site and throughout the year but averaged ‐0.204 and ‐0.045% day−1, respectively. Based upon measurements of OM standing stock and particle size distributions, POM processing rates of 1100–1400 g m2 yr−1 were calculated. These rates are near the upper end of the range for net annual production in Typha wetlands, suggesting that there is little net accumulation of POM.4. Despite some problems, the EDM method has the potential to facilitate studies of detrital dynamics in large, heterogeneous systems.

Birds Conserve Plasma Volume during Thermal and Flight-Incurred Dehydration

Dehydration tolerance in mammals is associated with the degree to which an animal is able to maintain plasma volume. During thermal dehydration, rock pigeons (Columba livia), quail (Coturnix coturnix japonica), and white-necked ravens (Corvus cryptoleucus) maintained nearly constant volumes despite mean body mass losses of 17%, 15%, and 13%, respectively. During flight-incurred dehydration in tippler pigeons (C. livia), no changes occurred in plasma volume although the birds lost 6%-10% of their preflight body mass. Thus, dehydrated birds were found to be excellent plasma volume conservers, like the most xericadapted mammal species. We suggest that plasma volume conservation in birds is an adaptation associated with high heat loads incurred during flight. In contrast, plasma conservation in mammals is associated with their ability to inhabit arid environments.

Moult energetics of the northern elephant seal (Mirounga angustirostris)

Northern elephant seals, Mirounga angustirostris, undergo an annual moult during which they shed all of their pelage and underlying epidermis. Moulting takes place on land and lasts a mean of 32.0±6.6 days. During this time the mean mass loss of adult females was 24.7±6.1%. Mean body composition at arrival (25.6±4.8%fat) did not differ significantly from that at departure (24.9±3.2%fat). Fat catabolism accounted for 93.6%of derived energy and 41%of mass lost. Approximately 3.5%of total mass loss was associated with the shedding of the pelage and epidermis. Moulting female northern elephant seals express an average daily metabolic rate of 2.0±0.6 times that predicted for adult terrestrial mammals. This energy demand was met by losing 3.0 kg d‐1 of total body mass. These energy expenditures suggest that, similar to data for harbour seals, the moult period is a time of relatively low energy expenditure.

Mass Changes and Metabolism in Territorial Male Antarctic Fur Seals (Arctocephalus gazella)

Energy expenditure of fasting territorial male Antarctic fur seals at South Georgia was measured by mass loss and analysis of carcass composition using tritium dilution in 1987 and 1988. Mean mass loss was 1.52 ± 0.04 kg • d⁻¹, mean length of territory tenure was 30.7 ± 2.21 d, mean mass at the start of tenure was 188.0 ± 1.92 kg; there were no differences between the two years (P > 0.1). Mass loss was 53.8% fat (80% of which was from blubber), 36% water, and 10.2% protein. Fat accounted for 91.6% of energy expenditure, the remainder being from protein. Energy expenditure was 42.1 ± 2.34 MJ • d⁻¹, or 3.16 ± 0.34 W • kg⁻¹, which is 3.3 times the predicted basal metabolic rate. Large body size in male compared to female fur seals may be related to the energy requirements of territoriality, but only in 1988 was there a significant correlation between starting mass and duration of tenure. This suggests that energy reserves are only one of several factors influencing tenure duration. Male fur seals are compose...