Decay Class Research Articles

A comparison of selected parametric and imputation methods for estimating snag density and snag quality attributes

Snags (standing dead trees) are an essential structural component of forests. Because wildlife use of snags depends on size and decay stage, snag density estimation without any information about snag quality attributes is of little value for wildlife management decision makers. Little work has been done to develop models that allow multivariate estimation of snag density by snag quality class. Using climate, topography, Landsat TM data, stand age and forest type collected for 2356 forested Forest Inventory and Analysis plots in western Washington and western Oregon, we evaluated two multivariate techniques for their abilities to estimate density of snags by three decay classes. The density of live trees and snags in three decay classes (D1: recently dead, little decay; D2: decay, without top, some branches and bark missing; D3: extensive decay, missing bark and most branches) with diameter at breast height (DBH)⩾12.7cm was estimated using a nonparametric random forest nearest neighbor imputation technique (RF) and a parametric two-stage model (QPORD), for which the number of trees per hectare was estimated with a Quasipoisson model in the first stage and the probability of belonging to a tree status class (live, D1, D2, D3) was estimated with an ordinal regression model in the second stage. The presence of large snags with DBH⩾50cm was predicted using a logistic regression and RF imputation. Because of the more homogenous conditions on private forest lands, snag density by decay class was predicted with higher accuracies on private forest lands than on public lands, while presence of large snags was more accurately predicted on public lands, owing to the higher prevalence of large snags on public lands. RF outperformed the QPORD model in terms of percent accurate predictions, while QPORD provided smaller root mean square errors in predicting snag density by decay class. The logistic regression model achieved more accurate presence/absence classification of large snags than the RF imputation approach. Adjusting the decision threshold to account for unequal size for presence and absence classes is more straightforward for the logistic regression than for the RF imputation approach. Overall, model accuracies were poor in this study, which can be attributed to the poor predictive quality of the explanatory variables and the large range of forest types and geographic conditions observed in the data.

LHC as a complementary probe to study 0 νββ mechanisms

We discuss the possibility of relating observation of resonant production of charged particle, followed by decay into a pair of same sign di-electrons in association with two jets at the LHC, to a class of neutrinoless double beta decay (0 νββ ) mechanisms where the intermediate particles all have TeV scale masses. A specific example in the context of SUSY with lepton number violation is presented.

Stocks and decay dynamics of above- and belowground coarse woody debris in managed Sitka spruce forests in Ireland

Coarse woody debris (CWD) has become recognised as an important component of the carbon (C) pool in forest ecosystems. In Ireland, managed Sitka spruce ( Picea sitchensis (Bong) Carr.) forests account for 52.3% of the total forest estate. To determine the stock and decay dynamics of above and belowground CWD, field surveys using fixed area sample plots, were conducted in six even-aged Sitka spruce stands, representing the young, intermediate and mature stages of a typical commercial rotation. The volume, mass, density loss and C:N ratio of all CWD types (logs, stumps, and coarse roots) were determined using a five-decay class (DC) system. The decay rates and half life of CWD was also determined. To estimate CWD coarse root mass; roots associated with stumps classified in different decay classes were excavated. The coarse roots were categorised into small (2–10 mm), medium (10–50 mm) and large (>50 mm) diameter classes. CWD C-mass ranged from 6.98 to 18.62 Mg ha −1 and was highest in an intermediate forest (D35), while the aboveground volume varied from 6.31 to 42.27 m 3 ha −1. Coarse roots accounted for 21% to 85% of the total CWD C-pool in the surveyed stands. The total CWD C-mass was poorly correlated with the number of thinning events ( R 2 = 0.29), when data from D35 was excluded. The density loss was significant in logs (45%), stumps (58%), and small- (38%), medium- (50%) and large roots (38%) as decay progress from DC 0 to 4. There was a 46%, 41%, 51%, 72% and 57% decline in C:N ratio of logs, stumps, small-, medium- and large roots, respectively, as decay progressed from DC 0 to 4. The density decay rates were 0.059, 0.048 and 0.036 kg m −3 year −1 for logs, stumps and coarse roots, respectively. The size classification of roots did not significantly affect their decay rate. The half life (50% decomposition) of CWD was estimated has 12-, 14- and 19 years for logs, stumps and roots of Sitka spruce. Regression curves showed a strong correlation between the density and C:N ratio ( R 2 = 0.69, 0.74 and 0.93 for logs, stumps and coarse roots, respectively). The long term storage of C and its slow rate of decomposition make CWD a vital structural and functional component of the CWD C-pool and a major controller of forest ecosystem C-retention.

Retention of aspen ( Populus tremulae) at final cuttings – The effect of dead wood characteristics on saproxylic beetles

To preserve biodiversity in managed forest landscapes dead and living trees are retained at final cuttings. In the present study we evaluated the effect of these practices for saproxylic (wood-dependent) beetles inhabiting dead aspen trees ( Populus tremulae). For saproxylic beetles, tree retention at final cuttings can be expected to be especially valuable for species adapted to sun-exposed dead wood, a substrate that only rarely occurs in well managed forest stands. Therefore, the current evaluation was conducted as a comparison of species richness, species density (number of species per sample), assemblage composition and occurrence of individual species between clear-cuts, where aspen trees were retained, and closed forest stands with aspen trees. The study was conducted in central Sweden and the beetles were sampled by sieving of bark from CWD (coarse woody debris) of aspen. There was no significant difference in rarefied species richness between forest and clear-cut sites. Species composition differed significantly between the two stand types. Generalized linear mixed-effects models predicted the species density to be 34% lower in CWD objects in forest sites than on clear-cuts. This pattern could partly be explained by differences in CWD diameter, decay class and bark types between the two stand types (clear-cut/forest). Stand type was a significant predictor of occurrence in individual CWD objects for 30% of analysed individual beetle species. For all species except one, the variable stand type predicted higher occurrence on clear-cuts than in forest stands. To conclude, our results demonstrate that retention of aspen on clear-cuts contributes to population recruitment of a different assemblage of species than CWD within stands.

Variability of moisture in coarse woody debris from several ecologically important tree species of the Temperate Zone of Europe

ABSTRACTDeadwood moisture affects multiple functions of downed logs in forest ecosystems. They include provision of habitats for xylobionts, additional water stores and organic carbon stocks. In contrast to Northern American forests, little is known about moisture variability in downed logs of important tree species within the Temperate Zone of Europe. Therefore, our study aimed at elucidating this variability according to species, site and decay class (DC). Measurements were taken by TDR during two vegetation periods in eight Carpathian natural forests representing distinct site conditions, ranging from xerothermophilous to subalpine. Downed logs of Quercus spp., Abies alba Mill., Fagus sylvatica L., and Picea abies L., belonging to various DCs, were selected and instrumented with TDR probes. Species and DC‐specific TDR calibration showed the importance of intrinsic wood porosity. The course of deadwood moisture consisted of drying during the early decay stage, except for A. alba and F. sylvatica, and an intense water reabsorption at later decay stages. Average moisture for all species and sites displayed seasonal trends, reflecting the occurrence of precipitation clusters and dry periods, as well as short‐term fluctuations. Cross‐spectral analysis revealed that both sapwood and heartwood participated in wetting and drying processes, but only after reaching an advanced stage of decay. New findings can be applied in interpreting, modelling and predicting deadwood water stores, habitat properties and respiration. Copyright © 2011 John Wiley & Sons, Ltd.

Logging Residue Volumes and Characteristics following Integrated Roundwood and Energy-Wood Whole-Tree Harvesting in Central Maine

Abstract Integrated roundwood and energy-wood whole-tree, partial harvesting has become common in Maine over the past decade, yet there is limited information about the volume and characteristics of logging residues left behind on such harvest sites. To better inform forest managers about the downed woody material remaining after whole-tree partial harvesting, we measured downed wood volume and characteristics on 12 harvested sites in central Maine using line intersect sampling. All sites were harvested using mechanical systems (feller-bunchers and grapple skidders) within a year prior to sampling. The mean volume of downed wood across all sites was 726 ± 57 ft3/ac (±SE), 47% of which was residue generated by the harvest. The variability of residue volumes was higher within sites (coefficients of variation between 36 and 69%) than between sites (coefficient of variation, 27%). Coarse woody material between 3 and 6 in. in diameter at the large end dominated the postharvest debris, while logs greater than 10 in. in diameter were scarce. The majority of harvest-generated downed wood was in decay class 1, whereas preharvest debris consisted of mostly decay classes 2, 3, and 4. The volumes of downed wood remaining on the study sites were within the range of volumes found on other managed sites of similar forest types. However, further research is necessary to assess whether these amounts and characteristics are adequate for long-term maintenance of ecological processes.

A Practical Emergence Chamber for Collecting Coleoptera from Rotting Wood, with a Review of Emergence Chamber Designs to Collect Saproxylic Insects

ABSTRACT A detailed and accurate survey of the insect fauna of rotting wood can be difficult due to the physical and mechanical properties of the habitat. Quarantining pieces or parts of dead wood in emergence chambers and collecting the insects that emerge is an effective survey method. Here we describe an inexpensive emergence chamber made from an 18-gallon (ca. 68-L) Sterilite® plastic tote box that was modified by adding a removable bottom collection jar and ventilation to the top and side. Ninety of these emergence chambers were three-fourths filled with dead wood (2.5–20 cm diameter) of various decay classes, and run for 24 months in Great Smoky Mountains National Park. A total of 5,692 adult Coleoptera specimens representing 50 families, 226 genera, and 275+ species were collected. Selected results are presented to illustrate the effectiveness of the design. Five fundamental axes of emergence chamber design are identified and discussed. We also compare this design to other published emergence chamb...

How well does a log decay-class system capture the ecology of decomposition? – A case-study from Tasmanian Eucalyptus obliqua forest

The use of decay-class systems in characterising the state of decomposition of a forest’s complement of rotting logs is widespread. While most systems are based on an assessment of logs’ external characteristics, there is an implicit assumption that doing so captures important information on the underlying processes of internal decomposition. However, the validity of this remains largely untested. We explored the relationship between decay-class and internal state of decomposition in logs of Eucalyptus obliqua in the lowland wet eucalypt forests of Southern Tasmania, Australia. We examined rotten-wood samples from a large population of logs across a wide range of diameters. From this we determined that smaller-diameter (<60 cm: regrowth-sized) logs differ from larger-diameter (>60 cm: mature-sized) logs in their pathways of internal decomposition. Decomposition in regrowth-sized logs is characterised by greater activity of surface rots, with white rot-types predominating. Decomposition in mature-sized logs is more concentrated in the interior of the log, with brown rot-types tending to dominate. These differences probably both reflect and help shape the communities of organisms inhabiting logs of different origins. Despite these differences, regrowth and mature-sized logs show the same general progression of internal decomposition across the five decay-classes, to the extent that each class represents logs that have lost a predictable proportion of their original mass. We conclude that a decay-class system that is restricted to a single dimension, such as the five-class system used for E. obliqua, will be quite able to capture the main trajectory of biomass loss, but will not be able to characterise the complexity of the ecological processes giving rise to this loss. Studies that employ single-dimension decay classes, and which aggregate decay-class data across logs, can be given added ecological meaning by first partitioning logs into diameter-classes that reflect the underlying differences in the maturity of the trees giving rise to the logs. For E. obliqua logs, a cut-off diameter of 60 cm offers an appropriate distinction between regrowth-aged and mature-aged trees.

Managed vs. unmanaged. Structure of beech forest stands (Fagus sylvatica L.) after 50 years of development, Central Bohemia

In this study, the structure and spatial patterns of adjacent beech (Fagus sylvatica L.) forest stands, both those having undergone intensive management and those without management intervention over the last 50 years were analyzed. Data was collected from six 1ha permanent research plots. Four plots were established in varying parts of the reserve, comprising entirely of even-aged managed forest stands; two 1-ha permanent plots were located in a non-interventional stand. For each woody stem, basic dendrometrical data and coordinates were measured. The total volume of dead wood (standing and fallen) and its classes of decay were recorded. The structure and species diversity of forest stands were analyzed using skewness and the coefficient of variation of dbh distribution, the Gini index, the Shannon index, the mingling index, the Pielou index of segregation and the Hopkins-Skellam, Pielou-Mountford, Clark-Evans aggregation indices, the diameter differentiation index and Ripley K function. The diameter distribution of the managed stands was generally normal, albeit with a large diameter range and with a typical flat diameter curve. A general lack of giant trees, lower rates of coarse woody debris (from 0.2 to 0.5% of the total living volume) and random tree distribution were also confirmed. Within the investigated area, the diameter differentiation and Gini indices along with the degree of skewness and the coefficient of variation made it possible to monitor the shift from even-aged forest management to spontaneous forest development. In general, spontaneous development was marked mainly by aggregated tree distribution in the middle and lower layer, and a shift from normal to reversed J-shaped dbh distribution. The total volume of deadwood in one of the unmanaged plots amounted to 48.10 m3/ha (9.5% of living wood volume). The use of adequate structural and spatial analysis as indicators of natural forest development are discussed.

Mesostigmatid mites in four classes of wood decay

We studied the mesostigmatid mite community in four classes of wood decay in mixed (pine-oak) forest stands in the Wielkopolska region, Cental-West Poland. A total of 80 samples, including bark, phloem and rotten wood of coniferous and deciduous species logs, were taken in August 2006 and 2007. Decay classes were a qualitative, categorical index based on visual assessment of decomposition in coarse woody debris. A total of 3621 mesostigmatid mites were counted and identified to 91 species. In general the total number of species was diverse in the decay classes and ranged from 35 (classes I and II) to 58 (class IV). The average number of species did not differ significantly among wood decay classes. Also the abundance of mesostigmatids did not differ significantly among wood decay classes, but the highest abundance was observed in the last class (IV). Cluster analysis of the species identity index showed that the microhabitats were divided into two main clusters: relatively undecayed wood and decayed wood. Species accumulation curves showed that relatively decayed wood (class IV) had a greater rate of species accumulation than undecayed wood from the class I decomposition.

Legacies from natural forest dynamics: Different effects of forest management on wood-inhabiting fungi in pine and spruce forests

The species composition of wood-inhabiting fungi (polypores and corticoids) was investigated on 1138 spruce logs and 992 pine logs in 90 managed and 34 natural or near-natural spruce and pine forests in SE Norway. Altogether, the study included 290 species of wood-inhabiting fungi. Comparisons of logs with similar properties (standardized tree species, decay class, dimension class) in natural and managed forests showed a significant reduction in species number per log in managed spruce forests, but not in managed pine forests. The species number per log in managed spruce forests was 10–55% lower than on logs from natural spruce forests. The reduction was strongest on logs of large dimensions. A comparison of 200–400 spruce logs from natural and managed forests showed a 25% reduction in species richness corresponding to a conservative loss of ca. 40 species on a regional scale. A closer inspection revealed that species confined to medium and very decayed spruce logs were disfavored in managed forests, whereas species on early decay classes and decay generalists were unaffected. Similarly, species preferring large spruce logs were disfavored in managed forests. Forest management had strongest impact on low-frequent species in the spruce forests (more than 50% reduction), whereas common species were modestly affected. Corticoid fungi were more adversely affected than polypore fungi. These results indicate that wood-decaying fungi in pine forests are more adapted to forest disturbances than spruce-associated species. Management measures securing a continuous supply of dead wood are more important in spruce forests than in pine forests.

Response of saprophagous wood-boring beetles (Coleoptera: Cerambycidae) to severe habitat loss due to logging in an aspen-dominated boreal landscape

Logging significantly reduces the proportion of late-seral stands in managed boreal landscapes. Availability of habitat elements typical of these stand types, such as standing dead wood, decreases, and dependant species may have their abundance reduced or become locally extirpated, potentially affecting the ecosystem processes/services in which they take part. We evaluated the impact of habitat loss on saprophagous wood-boring beetles (Coleoptera: Cerambycidae) in an aspen-dominated landscape intensively logged for the past 30 years. Sixty natural snags of middle decay class were chosen along a gradient of habitat loss and disturbance age, cut down and dissected for beetle larvae. We then assessed relationships between species occurrence and percentage of residual cover and age of disturbance at spatial scales ranging from 40 to 2000 m radii. The most common species, Anthophylax attenuatus, showed no response, being abundant regardless of the intensity of habitat loss. The second most common species, Bellamira scalaris, showed a negative response, especially in sites which had been fragmented for a longer time. A third species, Trachysida mutabilis, showed an inverse trend, having a higher probability of presence where habitat loss was more severe. Our study shows that some saprophagous wood-borers do react negatively to habitat loss, but that within a relatively homogenous group the response can vary significantly between species. Saprophagous wood-borers should be considered potentially sensitive to habitat loss, and their response to fragmentation remains to be evaluated on a longer time frame.

Abundance and function of large woody debris in small, headwater streams in the Rocky Mountain foothills of Alberta, Canada

AbstractLarge woody debris (LWD) significantly influences the structure and function of small headwater streams. However, what it contributes to geomorphic function depends on where it is located relative to the stream channel. We quantified LWD abundance and tested for associations among decay, position, orientation and function classes in 21 streams near Hinton, Alberta, Canada. LWD was more frequent (64.0 ± 3.3 LWD 100 m−1) in streams in the Alberta foothills than it was in small streams in mountain, coastal, broadleaf deciduous and boreal forests, likely due to the narrow channel widths and low capacity of our study streams to transport logs downstream. LWD volumes were greater in coastal streams than in the Alberta foothills, likely due to differing tree sizes and decay rates. LWD morphology changed significantly as logs decayed and transitioned to different position and orientation classes. LWD in decay classes I and II were longest, most commonly in the bridge and partial bridge position classes, oriented perpendicular to stream flow, suspended above the channel and contributing least to stream geomorphic functions. LWD length and volume (but not diameter) decreased as decay advanced, making logs less stable. LWD in decay classes III and IV were strongly associated with partially bridged, loose, and buried position classes. They were more commonly diagonal or parallel to stream flow and contributed to bank stability, sediment retention, debris jams and riffle and pool formations. These results have been integrated into a conceptual model of LWD dynamics that provides a framework for future research on the mechanisms and rates of LWD recruitment, decay, transport and function. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Coarse woody debris mass dynamics in temperate natural forests of Mt. Jumbong, Korea

Coarse woody debris (CWD) mass dynamics in three temperate natural forests, dominated by Quercus mongolica, Abies holophylla, and Pinus densiflora, were studied for 5 to 8 years in a Korea National Long-Term Ecological Research (KNLTER) site located in Mt. Jumbong, Korea. CWD mass (Mg/ha), input rate of CWD mass (Mg <TEX>$ha^{-1}\;y^{-1}$</TEX>), and decay rate constant (1/y) were 20.6, 1.20, and 0.058 for Q. mongolica forest, 12.2, 0.44, 0.106 for A. holophylla forest, and 5.0, 0.00, and 0.086 for P. densiflora forest, respectively. CWD mass was classified into species, types (log, snag, and stump), and decay classes (I-V). The proportion of logs was higher than that of the other CWD types in Q. mongolica forest because of wind-related mortality, whereas the proportion of logs was similar to the proportion of snags in A. holophylla forest and P. densiflora forest. CWD mass, input rate, decay rate, and distribution reflected the status of forest regeneration and succession for three forests. Mass dynamics were affected interactively by a variety of factors including species, microclimate, and topography, but these effects were hardly distinguishable in this study because of the limited number of comparable sites and pieces of CWD. Thus, further studies will require data regarding long-term microclimate and CWD mass dynamics in a variety of forest types, which could represent diverse environmental factors.

Post-harvest windthrow and recruitment of large woody debris in riparian buffers on Vancouver Island

Large woody debris (LWD) provides structural complexity to small streams. Riparian buffers are intended to provide long-term vegetation cover and supplies of LWD, but post-harvest windthrow often occurs. To evaluate the impacts of windthrow in riparian buffers and identify the components for a small stream LWD recruitment model, we sampled 26 streams in immature and older stands in wind-exposed areas of southwestern and northern Vancouver Island. These treed buffer strips had been exposed following clearcut harvest of adjacent timber on both sides 1–20 years previously. For stream sections 100 m long in each buffer, all logs greater than 7.5 cm diameter that spanned at least part of stream channel were measured. A total of 658 logs were recorded. Windthrown trees were comparable in characteristics to the trees that made up the buffer. The majority of logs derived from windthrown trees were oriented perpendicular to the stream channel and were suspended above the stream channel. Even 20 years after harvesting, two-thirds of the logs were still suspended above the stream. Logs in older buffers were more decayed, and the decay rate depended on tree species and initial diameter. Log height above stream was negatively correlated with log decay class and time since logging. Log length declined with time since harvest exposure and decay class. Sediment was exposed on upturned roots and within mineral soil pits. The volume of soil retained on upturned rootwads declined over time, but some soil remained even after 20 years. Very little of this exposed sediment was close enough to the creek to result in sediment delivery.

Species Composition of Saproxylic Fungal Communities on Decaying Logs in the Boreal Forest

Coarse woody debris supports large numbers of saproxylic fungal species. However, most of the current knowledge comes from Scandinavia and studies relating the effect of stand or log characteristics on the diversity and composition of decomposer fungi have not been conducted in Northeastern Canada. Logs from five tree species were sampled along a decomposition gradient in nine stands representing three successional stages of the boreal mixed forest of Northwestern Quebec, Canada. Using a molecular fingerprinting technique, we assessed fungal community Shannon-Weaver diversity index, richness, and composition. We used linear mixed models and multivariate analyses to link changes in fungal communities to log and stand characteristics. We found a total of 33 operational taxonomic units (OTUs) including an indicator species for balsam fir (similar to Athelia sp.) and one found only in aspen stands (similar to Calocera cornea). Spruce logs supported the highest fungal Shannon-Weaver diversity index and OTU number. Our results support the hypothesis that log species influences fungal richness and diversity. However, log decay class does not. Stand composition, volume of coarse woody debris, and log chemical composition were all involved in structuring fungal communities. Maintaining the diversity of wood-decomposing communities therefore requires the presence of dead wood from diverse log species.

Nutrient concentration of down woody debris in mixedwood forests in central Maine, USA

Both nutrient concentrations and pre- and post-harvest pool sizes were determined across down woody debris decay classes of several hardwood and softwood species in a long-term, natural disturbance based, silvicultural experiment in central Maine. Concentrations of N, P, Ca, Mg, Cu, Fe, and Zn generally increased 2- to 5-fold with increasing decay class. Concentrations of Mn, Al and B did not differ among decay classes, while K decreased by 20–44% from decay class 1 to class 4. C:N-ratios declined with increasing decay class, while N:P-ratios increased from decay class 1 to 2 and then plateaued with further decay. Within decay classes, softwoods generally had lower nutrient concentrations and higher C:N-ratios than hardwoods; N:P-ratios did not differ between hardwoods and softwoods. Although gap harvesting increased the size of the overall down woody debris nutrient pools, mostly through a large pulse of decay class 1 material, harvesting generally reduced the nutrients held in advanced decay classes. Pre-harvest down woody debris pools for N, P, K and Ca were 11.0, 0.6, 2.1 and 21.1 kg ha, respectively, while postharvest were 20.0, 1.3, 6.2 and 46.2 kg ha, respectively. While the gap-based silvicultural systems sampled in this study doubled the size of the pre-harvest, downed woody debris nutrient pools, the post-harvest pools were estimated to be only 3.2–9.1% of aboveground nutrients.–1–1

Temporal variability of deadwood volume and quality in boreal old-growth forests

Reference deadwood volumes from natural forests for forest management and restoration are often derived from one-time measurements or from repeated measurements over short time-scales. Such an approach often assumes an equilibrium state between tree mortality and decomposition, which is questionable in many boreal forest ecosystems due to the occurrence of allogenic disturbances. Using a simulation model based on empirical estimates of tree mortality, disturbance chronologies and models of wood decay class dynamics, this study aimed at characterizing variability in the volume and quality of deadwood for the past 200 years. The variability of deadwood volumes in old-growth forests, arising from differences in disturbance regimes and differing decay rates, was exemplified in two areas of Picea abies-dominated forests in northern Europe. The results imply that with stable deadwood input and slow decay rates the deadwood volume may be in an equilibrium state. On the contrary, if moderate-severity disturbances occur such a state seems improbable. Both study areas displayed continuity in deadwood availability, although temporary paucity in the early decay classes with shortest residence times was also observed. The results stress the importance of understanding the dynamic nature of deadwood in old-growth forests, instead of the traditional view of deadwood as a static ecosystem component.

Ultraviolet Fluorescence to Identify Navel Oranges with Poor Peel Quality and Decay

Navel oranges (Citrus sinensis) were sorted into four groups under ultraviolet illumination in commercial packinghouse black light rooms based upon the amount of fluorescence visible on each fruit to determine if fluorescence was predictive of peel quality. The groups corresponded to fruit with 1) little or no fluorescence (group 0), 2) low fluorescence (group 1), 3) moderate fluorescence (group 2), and 4) large fluorescent areas (group 3) that were indicative of developing decay lesions. Identification and elimination of group 3 fruit in black light rooms is a common practice now, but the other groups pass through these rooms. Six tests were conducted over a 2-year period during different times in the mid to late navel orange season. Fruit were visually evaluated for peel quality within 24 hours of their initial segregation into fluorescence groups and again following 3 weeks of storage at 15 °C. Peel quality assessment was based upon commercial grading practices, and the fruit were placed into fancy, choice, juice, or decay classes. Fruit with low to no peel fluorescence (groups 0 and 1) had numerous fancy-grade fruit and few juice- and decay-grade fruit in comparison with the other two groups. In contrast, fruit with moderate fluorescence (group 2) were of poor peel quality. In the initial evaluation, this group had 28% fewer fancy fruit and 19% more juice fruit than did group 0. During storage, group 2 fruit declined markedly in quality and numerous fruit of group 2 in the choice and juice classes decayed; the percentage of decayed fruit increased from 1% initially to 29% after 3 weeks of storage. Navel oranges in group 3, with numerous and obvious fluorescent decay lesions, mainly consisted of either juice grade or decayed fruit; 70% of group 3 decayed after 3 weeks. In addition to removing fluorescing fruit that have obvious indications of decay (group 3), it would be advantageous to remove or otherwise recognize that fruit with moderate levels of fluorescence (group 2) are also of lower quality and that they should not be selected for long storage or distant transport. Their identification may be most practical with an automated system using machine vision and ultraviolet illumination.

Snag Longevity and Decay Class Development in a Recent Jack Pine Clearcut in Michigan

Abstract To better understand the factors that influence the longevity and decay class development of natural and girdled snags in jack pine (Pinus banksiana Lamb.) plantations managed for Kirtland's warbler (Dendroica kirtlandii Baird) breeding habitat in the northern Lower Peninsula of Michigan, we followed the fate of 335 jack pine and oak (Quercus spp.) snags. After 2.5 years, 41% of snags snapped or uprooted, with most snapping or uprooting occurring within the first year. Jack pine snags experienced higher rates of snapping or uprooting than oak or all other snags combined, regardless of whether natural or girdled. Girdling by itself or as an interaction term had no significant effect on snapping or uprooting for either jack pine or oak, but both diameter (P = 0.03) and height (P = 0.01) influenced snapping and uprooting in oak. Thirty months after treatment, the percentage of snags among decay classes differed between species of snag and snag types (natural-girdled), with snag height inversely related to snag decay class development. These results suggest that snag development will occur rapidly in recently clearcut jack pine stands and that higher densities of snags may be needed to be retained or created if management goals are to emulate more natural conditions.