Crown In Jury Research Articles

Nonstructural carbohydrates explain post-fire tree mortality and recovery patterns.

Trees use nonstructural carbohydrates (NSCs) to support many functions, including recovery from disturbances. However, NSC's importance for recovery following fire and whether NSC depletion contributes to post-fire delayed mortality are largely unknown. We investigated how fire affects NSCs based on fire-caused injury from a prescribed fire in a young Pinus ponderosa (Lawson & C. Lawson) stand. We assessed crown injury (needle scorch and bud kill) and measured NSCs of needles and inner bark (i.e., secondary phloem) of branches and main stems of trees subject to fire and at an adjacent unburned site. We measured NSCs pre-fire and at six timesteps post-fire (4days-16months). While all trees initially survived the fire, NSC concentrations declined quickly in burned trees relative to unburned controls over the same post-fire period. This decline was strongest for trees that eventually died, but those that survived recovered to unburned levels within 14months post-fire. Two months post-fire, the relationship between crown scorch and NSCs of the main stem inner bark was strongly negative (Adj-R2=0.83). Our results support the importance of NSCs for tree survival and recovery post-fire and suggest that post-fire NSC depletion is in part related to reduced photosynthetic leaf area that subsequently limits carbohydrate availability for maintaining tree function. Crown scorch is a commonly measured metric of tree-level fire severity and is often linked to post-fire tree outcome (i.e., recovery or mortality). Thus, our finding that NSC depletion may be the mechanistic link between the fire-caused injury and tree outcome will help improve models of post-fire tree mortality and forest recovery.

Predicting snag fall in an old-growth forest after fire

BackgroundSnags, standing dead trees, are becoming more abundant in forests as tree mortality rates continue to increase due to fire, drought, and bark beetles. Snags provide habitat for birds and small mammals, and when they fall to the ground, the resulting logs provide additional wildlife habitat and affect nutrient cycling, fuel loads, and fire behavior. Predicting how long snags will remain standing after fire is essential for managing habitat, understanding chemical cycling in forests, and modeling forest succession and fuels. Few studies, however, have quantified how fire changes snag fall dynamics.ResultsWe compared post-fire fall rates of snags that existed pre-fire (n = 2013) and snags created during or after the fire (n = 8222), using 3 years of pre-fire and 5 years of post-fire data from an annually monitored, 25.6-ha spatially explicit plot in an old-growth Abies concolor–Pinus lambertiana forest in the Sierra Nevada, CA, USA. The plot burned at low to moderate severity in the Rim Fire of 2013. We used random forest models to (1) identify predictors of post-fire snag fall for pre-existing and new snags and (2) assess the influence of spatial neighborhood and local fire severity on snag fall after fire. Fall rates of pre-existing snags increased 3 years after fire. Five years after fire, pre-existing snags were twice as likely to fall as new snags. Pre-existing snags were most likely to persist 5 years after fire if they were > 50 cm in diameter, > 20 m tall, and charred on the bole to heights above 3.7 m. New snags were also more likely to persist 5 years after fire if they were > 20 m tall. Spatial neighborhood (e.g., tree density) and local fire severity (e.g., fire-caused crown injury) within 15 m of each snag barely improved predictions of snag fall after fire.ConclusionsLand managers should expect fall rates of pre-existing snags to exceed fall rates of new snags within 5 years after fire, an important habitat consideration because pre-existing snags represent a wider range of size and decay classes.

Tree crown injury from wildland fires: causes, measurement and ecological and physiological consequences.

SummaryThe dead foliage of scorched crowns is one of the most conspicuous signatures of wildland fires. Globally, crown scorch from fires in savannas, woodlands and forests causes tree stress and death across diverse taxa. The term crown scorch, however, is inconsistently and ambiguously defined in the literature, causing confusion and conflicting interpretation of results. Furthermore, the underlying mechanisms causing foliage death from fire are poorly understood. The consequences of crown scorch – alterations in physiological, biogeochemical and ecological processes and ecosystem recovery pathways – remain largely unexamined. Most research on the topic assumes the mechanism of leaf and bud death is exposure to lethal air temperatures, with few direct measurements of lethal heating thresholds. Notable information gaps include how energy transfer injures and kills leaves and buds, how nutrients, carbohydrates, and hormones respond, and what physiological consequences lead to mortality. We clarify definitions to encourage use of unified terminology for foliage and bud necrosis resulting from fire. We review the current understanding of the physical mechanisms driving foliar injury, discuss the physiological responses, and explore novel ecological consequences of crown injury from fire. From these elements, we propose research needs for the increasingly interdisciplinary study of fire effects.

Residual stand damage from selective logging of tropical forests: A comparative case study in central Kalimantan and West Sumatra, Indonesia

Selective logging in natural forests in Indonesia involves logging trees with a diameter at breast height (dbh) of >50 cm and leads to damage to residual stands. This research was conducted on forest concession areas in West Sumatra and Central Kalimantan to analyze residual stand damage. The type and percentage of damage were calculated at both locations by evaluating 10 plots of 1 ha at each site. All trees with a dbh of >20 cm were measured and classified before and after felling and skidding. The stand density and felling intensity were analyzed to determine the factors affecting the amount of damage. Results indicated six types of damages: broken stem, crown injury, fallen or uprooted trees, leaning, bark and stem injuries, and buttress injury. All six types of damages were found in Central Kalimantan, whereas five types of damages (except buttress injury) were found in West Sumatra. On comparing pre- and post-logging conditions, a higher percentage of damage was identified in Central Kalimantan (27.8%) than in West Sumatra (22.4%). The percentage of tree damage increased in line with the increasing felling intensity at both locations. It was concluded that a higher tree density and felling intensity resulted in a greater residual stand damage both in Central Kalimantan and West Sumatra.

Persistence of fire-killed conifer snags in California, USA

BackgroundCoarse woody debris has numerous functions in forest ecosystems, including wildlife habitat, fuel loading, and nutrient cycling. Standing dead trees, or snags, are particularly important resources for wildlife, and guidelines for snag recruitment and retention are integral parts of forest management. However, snag persistence is not well understood and existing models are poorly validated. We monitored fire-killed conifer snag persistence after four California wildfires and one prescribed fire. Species sampled included white fir (Abies concolor [Gord. & Glend.] Lindl. ex Hildebr.), incense-cedar (Calocedrus decurrens [Torr.] Florin), Jeffrey pine (Pinus jeffreyi [Balf.]), sugar pine (Pinus lambertiana Douglas), and ponderosa pine (Pinus ponderosa Lawson & C. Lawson var. ponderosa C. Lawson).ResultsFire-injured trees that survived at least one year post fire were monitored for 10 years after they died. We developed two sets of species-specific snag persistence rates: a simplified model based only on time since death, and a full model that included tree characteristics. The primary factors affecting persistence rates in all models were snag age (years since death) and species. Secondary factors included diameter at breast height, time between fire and tree death, and crown injury. Snag persistence rates decreased with snag age. Yellow pine snags (a combined group of ponderosa pine and Jeffrey pine) fell significantly faster than any other species. Larger-diameter snags persisted longer than smaller-diameter snags for all species. Incense-cedar trees that survived longer post fire persisted longer as snags.ConclusionsThis study provides land managers with guidance on snag longevity, which can aid in planning for long-term wildlife habitat, fuel loading estimates, and forest structural diversity.

Asparagus decline and replant problem: A look back and a look forward at strategies for mitigating losses

Asparagus decline and the replant problem were both defined in the 1950s, but had been noted in asparagus fields long before. Although both conditions share many of the same features, there are distinct differences in the host symptoms and in the age of the field during the onset of symptoms. A number of factors contribute to both disorders. Abiotic factors, such as allelopathic residues, acidic soils, soil compaction, winter crown injury, and excessive harvest pressure, along with biotic agents like insects, weeds, and diseases contribute to decline and the replant problem. Toxic asparagus residues remain the major stressor in the replant problem. Although cultivar improvements along with close attention to reducing stress and disease outbreaks have lessened the damage from asparagus decline and the replant problem, these disorders still make serious inroads into field longevity and yield potential. The presentation will synthesize the results of numerous studies designed to enhance soil health and reduce asparagus decline and the replant problem. An assessment of the direction for future research projects will be presented.

Predicting Post-Fire Tree Mortality for 12 Western US Conifers Using the First Order Fire Effects Model (FOFEM)

Accurate prediction of fire-caused tree mortality is critical for making sound land management decisions such as developing burning prescriptions and post-fire management guidelines. To improve efforts to predict post-fire tree mortality, we developed 3-year post-fire mortality models for 12 Western conifer species—white fir (Abies concolor [Gord. & Glend.] Lindl. ex Hildebr.), red fir (Abies magnifica A. Murray bis), subalpine fir (Abies lasiocarpa [Hook.] Nutt.), incense cedar (Calocedrus decurrens [Torr.] Florin), western larch (Larix occidentalis Nutt.), lodgepole pine (Pinus contorta Douglas ex Loudon var. latifolia Engelm. ex S. Watson), whitebark pine (Pinus albicaulis Engelm.), ponderosa pines (Pinus ponderosa Lawson & C. Lawson var. scopulorum Engelm and var. ponderosa C. Lawson), Jeffrey pine (Pinus jeffreyi Balf.), sugar pine (Pinus lambertiana Douglas), Engelmann spruce (Picea engelmannii Parry ex Engelm.), and Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco var. glauca [Beissn.] Franco)—by pooling data collected from multiple fire-injury studies. Two sets of models were created: one for use in pre-fire planning in which only crown injury and tree diameter (DBH) were potential variables, and a second, optimal model for use in post-fire planning that used all significant variables. Predictive accuracy of all models was compared to the accuracy of the general, non-species specific mortality model used in the First Order Fire Effects Model (FOFEM) prior to version 5.7. The new species-specific models improved prediction of fire-caused tree mortality by 0 % to 48 %. Model accuracy increased the most for red fir, incense cedar, western larch, and whitebark pine, and increased the least for Engelmann spruce. The models in the post-fire option provided higher accuracy compared to the pre-fire models, but also required additional inputs. These new models were added to FOFEM beginning with version 5.7, and the options in the FOFEM Mortality Module were expanded. We describe the new options in FOFEM and how to use the software to predict tree mortality for pre-fire and post-fire planning, as well as modeling limitations and assumptions. The additions to FOFEM offer improved accuracy in predicting post-fire tree mortality for 12 Western conifer species and allow direct inputs of fire injury to increase software applicability to prescribed fire and post-fire forest management.

Nastajanje ksilemske in floemske branike pri bukvah, poškodovanih v žledolomu

After the severe ice storm in 2014, numerous damaged trees were not removed from forests. Due to the lack of general knowledge about the processes occurring in damaged trees, a study involving 14 European beeches was conducted in the Arboretum Volčji Potok. Trees were categorized by crown injury; injury class K % undamaged, A % damaged less than 50 %, B % damaged between 50 and 75 %, and C % damaged more than 75 %. During the 2014 growing season, micro-cores were collected every fortnight using a Trephor tool. Changes in crowns were also observed and noted. Transverse sections of micro-cores were prepared and observed using light microscopy and an image analysis system. Xylem growth rings were 20 to 95 % narrower in damaged beech trees compared to the undamaged trees. Damaged trees also produced narrower phloem rings. The biggest differences in cambial activity in beech appeared between Class A and Class B.

Fire-injured ponderosa pine provide a pulsed resource for bark beetles

Bark beetles can cause substantial mortality of trees that would otherwise survive fire injuries. Resin response of fire-injured northern Rocky Mountain ponderosa pine ( Pinus ponderosa Douglas ex P. Lawson & C. Lawson) and specific injuries that contribute to increased bark beetle attack susceptibility and brood production are unknown. We monitored ponderosa pine mortality and resin flow and bark beetle colonization and reproduction following a prescribed fire in Idaho and a wildfire in Montana. The level of fire-caused tree injury differed between the two sites, and the level of tree injury most susceptible to bark beetle attack and colonization also differed. Strip-attacked trees alive 3 years post-fire had lower levels of bole and crown injury than trees mass attacked and killed by bark beetles, suggesting that fire-injured trees were less well defended. Brood production of western pine beetle ( Dendroctonus brevicomis LeConte) did not differ between fire-injured and uninjured trees, although mountain pine beetle ( Dendroctonus ponderosae Hopkins) brood production was low in both tree types, potentially due to competition with faster developing bark beetle species that also colonized trees. Despite a large number of live trees remaining at both sites, bark beetle response to fire-injured trees pulsed and receded within 2 years post-fire, potentially due to a limited number of trees that could be easily colonized.

Predicting Douglas‐fir Sapling Mortality Following Prescribed Fire in an Encroached Grassland

Tree encroachment in fire‐maintained woodlands and grasslands is a major management concern, yet little information exists regarding the mechanisms of small tree mortality following prescribed burns. We sought to clarify the relative importance of tree size and fire‐induced injury in the post‐fire mortality of encroaching Douglas‐fir trees and to compare results with an existing mortality model for larger Douglas‐fir trees. Crown injury to small Douglas‐fir trees was a significant explanatory variable in post‐fire mortality models, with results suggesting a 20% threshold in crown scorch. Crown injury was strongly related to bole injury, and delayed mortality was important as we documented new mortality 20 months post‐burn. Mortality models for large Douglas‐fir tend to over‐predict small tree mortality, underscoring the need to better understand the mechanisms of fire‐caused mortality for small, encroaching trees.

Low tolerance of New Caledonian secondary forest species to savanna fires

AbstractQuestionsHow do early secondary successional forest species that grow in savannas differ in their tolerance to surface fires? What are the consequences of these fire tolerances for savanna–forest dynamics and landscape management?LocationAnthropogenic savannas in the New Caledonian biodiversity hotspot (SW Pacific).MethodsWe estimated the range of fire intensity in New Caledonian savannas using field survey of fuels and the BehavePlus fire behaviour model. Within the predicted range of fire line intensity, we assessed theoretical fire injury to the cambium and crown for 11 species: the dominant tree of New Caledonian savannas (Melaleuca quinquenervia) and early secondary successional forest species. Using empirical models, for each species we estimated cambium damage from depth of necrosis (as a function of fire line intensity and fire residence time) and bark thickness, and crown damage from scorch height (as a function of fire line intensity) and tree height. We compared bark thickness and tree height increment patterns among species as well as species potential fire tolerance.ResultsThe 11 species had very contrasting capacity to avoid fire injury to the bole cambium due to differences in bark investment patterns, but were all very exposed to scorching and crown injury. Overall, most of sampled individuals are likely top‐killed by low intensity fires (<1000 kW·m−1), which are frequent according to our simulations.ConclusionsThe early secondary successional forest species growing in New Caledonian savannas are poorly adapted to fire, in comparison with literature on worldwide trees in savannas. As a result, their juveniles are unlikely to reach adult size in fire‐prone areas. Restoration using the most fire‐tolerant species and fire prevention may be complementary strategies to manage such tropical landscapes in order to conserve biodiversity and ecosystem services.

Survival to prescribed fire of plantation-grown Corsican black pine in northern Portugal

The current fire regime threatens black pine (Pinus nigra Arn.) persistence in the Mediterranean Basin, which recommends larger-scale fuel treatments. Prescribed burning is an option for stand protection but its use in young stands (which are particularly at risk) is hindered by the scarce knowledge on post-fire tree survival. The objectives were to characterize bark thickness as a fire-resistance trait in P. nigra and to describe how post-fire tree survival responds to tree size and fire effects in a 16-year-old plantation. Bark thickness was related to diameter at breast height and height in the stem. Metrics describing tree size and stem and crown damage were measured 1 year after prescribed burning in 259 trees. Tree survival was modeled with logistic regression and Classification and Regression Tree analysis. Bark thickness increased linearly with diameter at breast height (dbh) and decreased with height in the stem. Tree survival was primarily a function of crown injury. Stem damage was an influent factor in small trees. Due to thinner bark and lower tolerance to crown damage, young P. nigra trees are less fire-resistant than other Mediterranean pines, e.g., Pinus pinaster. Prescribed fire should not be attempted if dbh <10 cm. Mechanical clearing is the treatment of choice in young stands with a significant shrub layer.

Predicting mortality for five California conifers following wildfire

Fire injury was characterized and survival monitored for 5677 trees >25 cm DBH from five wildfires in California that occurred between 2000 and 2004. Logistic regression models for predicting the probability of mortality 5-years after fire were developed for incense cedar ( Calocedrus decurrens (Torr.) Florin), white fir ( Abies concolor (Gord. & Glend.) Lindl. ex Hildebr.), sugar pine ( Pinus lambertiana Douglas), Jeffrey pine ( P. jeffreyi Balf.), and ponderosa pine ( P. ponderosa C. Lawson). Differences in crown injury variables were also compared for Jeffrey and ponderosa pine. Most mortality (70–88% depending on species) occurred within 2 years post-wildfire and had stabilized by year 3. Crown length and crown volume injury variables predicted tree mortality equally well; however, the variables were not interchangeable. Crown injury and cambium kill rating was significant in predicting mortality in all models. DBH was only a significant predictor of mortality for white fir and the combined ponderosa and Jeffrey pine models developed from the McNally Fire; these models all predicted increasing mortality with increasing tree size. Red turpentine beetle ( Dendroctonus valens) was a significant predictor variable for sugar pine, ponderosa pine, and Jeffrey pine; ambrosia beetle ( Trypodendron and Gnathotrichus spp.) was a significant predictor variable for white fir. The mortality models and post-fire tree survival characteristics provide improved prediction of 5-year post-wildfire tree mortality for several California conifers. The models confirm the overall importance of crown injury in predicting post-fire mortality compared to other injury variables for all species. Additional variables such as cambium kill, bark beetles, and tree size improved model accuracies, but likely not enough to justify the added expense of data collection.

Injuries induced in different strawberry genotypes by winter freeze and their effect on subsequent yield

AbstractSevere frosts without snow cover are disastrous for the garden strawberry, Fragaria × ananassa Duch. The objectives of this study were to determine injuries, caused by freeze to crowns and roots of 13 and five different cultivars/lines in 2002 and 2003, respectively; to observe subsequent plant behaviour; to measure yield and to find out its dependence upon the injuries. Based on percentages of injured branch crowns and roots, estimates of plant growth and yields, the relationships between the indices have been established. Root injury has had a stronger effect on plant growth compared with crown injury. Yield has been found to be correlated only with plant growth, root damage and root‐to‐crown ratio of per cent survival when root damage was heavy. Two different strategies of the cultivars/lines, associated with their morphological characteristics and physiological peculiarities influencing plant survival, growth and yield, have been revealed. To discern the characters and cultivar types that can be valuable in such extreme conditions, differences in the genotypes responses to freeze are examined and thoroughly analysed in the paper.

Radial growth of hardwoods following the 1998 ice storm in New Hampshire and Maine

Ice storms and resulting injury to tree crowns occur frequently in North America. Reaction of land managers to injury caused by the regional ice storm of January 1998 had the potential to accelerate the harvesting of northern hardwoods due to concern about the future loss of wood production by injured trees. To assess the effect of this storm on radial stem growth, increment cores were collected from northern hardwood trees categorized by crown injury classes. For a total of 347 surviving canopy dominant and subdominant trees, a radial growth index was calculated (mean annual increment for 1998–2000 divided by the mean annual increment for 1995–1997). Sugar maple (Acer saccharum Marsh.), yellow birch (Betula alleghaniensis Britt.), white ash (Fraxinus americana L.), and red maple (Acer rubrum L.) categorized in injury class A (crown loss of less than one-half) had mean growth index values of approximately 1.0, indicating no loss of mean radial growth after 3 years. For injury class B (crown loss of one-half to three-quarters) and class C (crown loss greater than three-quarters), growth index values significantly decreased for sugar maple, yellow birch, and red maple. For white ash, growth index values of classes B and C were not significantly different from those of class A trees. Growth index values of A. saccharum and A. rubrum in injury class C were the lowest of those measured. These results indicated that the severity of growth loss due to crown injury depends on tree species and crown replacement as well as the extent of crown loss.

Effect ofGalerucellaspp. on survival of purple loosestrife (Lythrum salicaria) roots and crowns

Starch levels, used as a measure of plant stress, were not consistently reduced in root or crown tissue of purple loosestrife plants after 2 yr of severeGalerucella calmariensisorGalerucella pusilla(Coleoptera: Chrysomelidae) defoliation. Early in the season, defoliation fromGalerucellaspp. approached 100%, but the majority ofLythrum salicariaplants regrew by the end of August, resulting in an average reduction of 81% of the aboveground biomass compared to the control. The stress imposed byGalerucellaspp. defoliation was less than that achieved from more severe stress imposed by mechanical shoot clipping at 2- or 4-wk intervals from June to October. Both shoot-clipping treatments killed the majority of plants after one growing season.Galerucellaspp. feeding reduced plant stature, which may reduce competitiveness. However, considering the extensive carbohydrate reserves present in the large woody crowns ofLythrum salicaria, it will require in excess of 2 yr of consistent, severe leaf defoliation to cause plant mortality. A combination of stresses, such as winter crown injury, or other biological control agents in addition toGalerucellaleaf defoliation may be required for plant mortality.

Relationships of ozone exposure to pine injury in the Sierra Nevada and San Bernardino Mountains of California, USA

Hourly ambient ozone exposure data and crown injury measurements were gathered in the Sierra Nevada and San Bernardino Mountains of California to develop relationships between the Ozone Injury Index (OII), the Forest Pest Management Index (FPM), chlorotic mottle, fascicle retention (OII index components) and cumulative ambient ozone indices for Pinus ponderosa Dougl. ex Laws and Pinus jeffreyi Grev. and Balf. Eleven sites located in the mixed conifer forest near ambient ozone monitoring sites were evaluated annually for 4 years. Four other sites in the San Bernardino Mountains were evaluated for 1 year. Analyses showed OII to be functionally equivalent ( r 2 = 0.96) to the FPM, and to depend only on fascicle retention and chlorotic mottle ( R 2 = 0.95) of the fourth whorl (or if four whorls are not present at the site, then the last whorl present for the majority of trees). Significant associations were found between OII and 4-year 24-h. summer SUM0, SUM06, W126 and HRS80 ozone indices. Three sites had higher levels of cumulative chlorotic mottle for individual whorls and larger numbers of trees with visible crown injury than other sites with similar cumulative ambient ozone levels. Including an indicator variable to discriminate between these two groups of sites increased R 2 and decreased root mean square (RMSE) for all indices, especially SUM0 ( R 2 = 0.93, RMSE reduced by 46%).

Factors Affecting a Laboratory Evaluation of Alfalfa Cold Tolerance

Currently, only test winter data are used to evaluate the winter hardiness of alfalfa (Medicago sativa L.) cultivars. A test winter is defined as field conditions severe enough to kill nonhardy cultivars and to cause varying degrees of winter injury to cultivars of intermediate hardiness. Due to the unpredictability of test winter occurrence, alternative methods are needed for predicting alfalfa winter survival. This research tested the effects of temperature stress, storage time, and plant size, measured as the width of the root at the crown‐root juncture, on a laboratory cold tolerance evaluation of field grown and hardened alfalfa plants. Plants were dug from the field in mid‐November and stored at −2°C until subjected to cold stresses from 0 to −24°C. Differences among entries were greatest at the −12 and −16°C cold treatments. Crown injury score was positively correlated with field fall growth (r = 0.91) and winter injury scores (r = 0.95; P ≤ 0.01). Root injury score was correlated positively with field fall growth (r = 0.87) and winter injury scores (r = 0.95; P &lt; 0.01). Large plants (&gt;10‐mm root diameter) had lower cold injury scores than small plants (1‐ to S‐mm root diameter). Correlations between plant size and winter injury were greatest (r &gt; −0.55, P ≤ 0.05) at low freezing temperatures. We propose a laboratory test in which field‐hardened seeding‐year alfalfa entries of a similar size are packed in dry vermiculite, exposed to temperatures of −12 to −16°C for 1 to 2 h, thawed, and scored after 3 wk of regrowth.

Changes in Soluble Carbohydrate Composition of Barley, Wheat, and Rye during Winter

AbstractSignificant increases in the production of winter cereals could be realized with improved hardiness. The objective of this research was to determine if overwintering cereals modify water soluble carbohydrate composition in response to naturally occurring winter freeze stress. Fields of wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), and rye (Secale cereals L.) were monitored throughout the winter between 1986 to 1990 for snow‐pattern development, temperature, and snowfall. Plant crowns were analyzed for freeze injury (form and intensity) and water soluble carbohydrate composition (fructan, sucrose, glucose, and fructose). Growth chamber plants were frozen and analyzed to confirm the interpretation of field plant data. In 1986, there was less fructan and more soluble sugars in the exposed than in the snow‐covered wheat plants (but no complete depletion of fructan), and no crown injury from equilibrium freezing. In 1987–1988, little injury or fructan hydrolysis occurred in barley, wheat, or rye; the plants were snow covered during cold periods. In 1989–1990, fructan hydrolysis to sugar in exposed barley, wheat, and rye plants paralleled that in the exposed wheat plants of 1986–1987. The fructan content of exposed barley plants was nearly depleted during the coldest weather. Exposed plants had typical equilibrium freeze injury. Growth chamber plants responded similarly to the exposed field plants. Plants exposed to freeze stress converted fructan to sugars which probably alleviated adhesive freeze stress. The energy of hydrolysis may be useful for placing sugar into sites within the tissue where its cryoprotective activity is most effective.

ForestHealth, an expert advisory system for assessing foliar and crown health of selected northern hardwoods

Assessment of tree health requires accurate estimates of crown condition and identification of specific biotic and abiotic agents that may affect crowns, stems, or roots. ForestHealth, an expert advisory system written in C language for the Macintosh™ platform, provides a diagnostic module and two training modules. The diagnostic module provides guidance in identifying foliar symptoms and the common insects, diseases, and abiotic disorders found on leaves of: sugar maple (Acersaccharum Marsh.), red maple (Acerrubrum L.), black cherry (Prunusserotina Ehrh.), northern red oak (Quercusrubra L.), and white oak (Quercusalba L.). Graphical user interfaces are central to both training modules. The Foliar Severity routine trains users to categorize injury (percent leaf area) on single leaves using a modified Horsfall–Barratt scale. The Crown Dieback routine displays different types and degrees of crown injury that users must identify and classify. Each crown is unique, generated in "real time" using tree–branch parameters selected by the user. Since the crowns are created on a three-dimensional basis, multiple views are possible. Written output from training sessions or periodic checks provide quantitative information for quality assurance and quality control. ForestHealth provides diagnostic assistance, training, quality assurance and quality control data, and standardization for research or survey projects involving forest health.