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PubMed2006

Climate warming and the risk of frost damage to boreal forest trees: identification of critical ecophysiological traits.

According to a hypothesis presented in the mid-1980s, climate warming will, paradoxically, increase the risk of frost damage to trees in the boreal and temperate zones. Dehardening and even growth onset may occur in trees during mild spells in winter and early spring, resulting in damage during subsequent periods of frost. In the present study, ecophysiological traits critical to the occurrence of frost damage in trees in the boreal zone were identified. Diagnostic computer simulations were performed to examine why one simulation model of frost hardiness in an earlier study predicted heavy frost damage as a consequence of climate warming, whereas another closely related model did not. The modeling comparison revealed that the response of ontogenetic development to air temperature during quiescence is a critical factor determining the risk of frost damage. As the response can be readily determined in growth-chamber experiments, the findings of the present study can be used to guide experimental work on the environmental regulation of the annual cycle of frost hardiness in trees.

Computer Simulation↗
PubMed1989

Technetium-99 cycling in maple trees: characterization of changes in chemical form.

Prior field studies near an old radioactive waste disposal site at Oak Ridge, TN, indicated that following root uptake, metabolism by deciduous trees rendered 99Tc less biogeochemically mobile than expected, based on chemistry of the pertechnetate (TcO-4) anion. Subsequently, the form of technetium (Tc) in maple tree (Acer sp.) sap, leaves, wood and forest leaf litter was characterized using one or more of the following methods: dialysis, physical fractionation, chemical extraction, gel permeation chromatography, enzymatic extraction, or thin layer chromatography (TLC) on silica gel. Chromatography (Sephadex G-25) of TcO-4 incubated in vitro with tree sap showed it to behave similar to TcO-4 anion. When labeled wood and leaf tissues were processed using a tissue homogenizer, 15% and 40%, respectively, of the Tc was solubilized into phosphate buffer. Most (65% to 80%) of the solubilized Tc passing a 0.45-micron filter also passed through an ultrafiltration membrane with a nominal molecular weight cutoff of 10,000 atomic mass units (amu). A majority (72% to 80%) of the Tc in wood could be chemically removed by successive extractions with ethanol, water and weak mineral acid. These same extractants removed only 23% to 31% of the Tc from maple leaves or forest floor leaf litter. Most of the Tc in leaves and leaf litter was removed only by strongly alkaline reagents typically used to release structural polysaccharides (hemicelluloses) from plant tissues. Chromatography (Sephadex G-25) of the ethanol-water extract from wood and the alkaline extract from leaves demonstrated that Tc in these extracts was not principally TcO-4 but was complexed with molecules greater than 1000 amu. Incubations of leaf and wood homogenates with protease approximately doubled the amount of Tc released from contaminated tissues. Ultrafiltration of protease-solubilized Tc from leaves and wood showed that 40% and 93%, respectively, of the Tc was less than 10,000 amu. TLC of the less than 10,000 amu fraction indicated the presence of TcO-4 in wood but not in leaves. In the leaf, TcO-4 is converted to less soluble forms apparently associated with structural components of leaf cell walls. This conversion explains why 99Tc is not easily leached by rainfall from tree foliage and why 99Tc appears to accumulate in forest floor leaf litter layers at the Oak Ridge study site.

Chromatography, Gel↗
PubMed2002

Elevated exposure rates under inclined birch trees indicate the occurrence of rainfall during radioactive fallout from Chernobyl.

Knowledge of the mode of deposition (wet or dry) during the main fallout period following the Chernobyl accident in late April 1986 is one of the most important parameters in environmental reconstruction of the radiation dose to the thyroid from 113I following the accident. Meteorological data are available only for a small number of locations, but routine field measurements in 1997 of exposure rates in areas still contaminated by 137Cs revealed that there is a natural indicator of wet deposition. Follow-up measurements confirmed that there is a significant difference in exposure rates measured on different sides at the bases of inclined birch trees in areas of wet deposition. In such areas, the exposure rates measured on the "sheltered" sides of the trees were on average 2.3+/-0.2 times those measured on the unsheltered side. In areas of dry deposition the comparable ratio was 1.01+/-0.02 for similarly inclined trees. Because birch trees are a common feature in the contaminated territories, this effect has a wide potential for use in determining whether the fallout in many areas was due to wet or dry deposition.

Environmental Exposure↗
PubMed1996

Pesticide poisonings in the lawn care and tree service industries. A review of cases in the New York State Pesticide Poisoning Registry.

Although pesticides are used extensively by lawn care and tree service workers, the incidence of pesticide poisonings among this population has never been systematically assessed. This article is a review of suspected and confirmed pesticide poisonings of lawn care and tree service applicators that were reported to the New York State Pesticide Poisoning Registry from 1990 to 1993. Thirty-nine cases were identified, of which 28 satisfied the criteria for a suspected or confirmed poisoning. At the time of the poisoning, the majority of applicators reported the use of more than one class of pesticide. The most common classes of pesticide applied were organophosphates (71%) and herbicides (43%). Twenty-four cases were identified through laboratory reporting. All 24 laboratory tests had been ordered for worker surveillance. Twenty of the reported workers were symptomatic. Personal protective equipment was used routinely by 22 of the 27 applicators for whom information was available. These data suggest that pesticide exposures are occurring among a subset of the lawn care and tree service applicators, despite the reported routine use of safety measures. More rigorous evaluation of the control measures utilized in the lawn care and tree and shrub industry is warranted.

Adult↗
PubMed1995

Evaluation of a decision tree for management of chronic wounds.

Nurses routinely make complex clinical decisions under conditions of uncertainty. They collect large, unwieldy data sets in the process of making these clinical decisions. To assist nurses in collecting and organizing data and in making complex clinical decisions, some nursing scholars recommend decision support systems. One such support system, a decision tree leads the nurse from general to specific assessments and ultimately to a decision choice or outcome. In this study, a decision tree was examined for its utility in promoting accuracy in decision making for management of chronic wounds among home care nurses. Home care nurses who used the decision tree made better decisions about staging and product choices for chronic wounds. More research is necessary to discover whether decision trees for the management of chronic wounds translate into improved client outcomes.

Chronic Disease↗
PubMed2006

Improved prediction of awakening or nonawakening from severe anoxic coma using tree-based classification analysis.

OBJECTIVE: To evaluate the utility of sensory and event-related evoked potentials for the prediction of awakening/nonawakening in severe anoxic coma and to design a decision tree helping decision for any patient in this condition. DESIGN: Prospective cohort study. SETTING: Clinical neurophysiology unit and intensive care unit of a French university hospital. PATIENTS: Sixty-two consecutive severe comatose patients after out-of-hospital cardiac arrest. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: We gathered clinical variables and recorded the somatosensory, auditory, and cognitive evoked potentials within an average period of 8 days after cardiac arrest. The patients were followed for 12 months and classified as awake or nonawake (permanent vegetative state or death). The statistical study included measurements of specificity, sensitivity, and positive and negative predictive value for each clinical and electrophysiologic variable recorded at the early stage of coma. Furthermore, a tree-based classification analysis was performed.All patients in whom somatosensory evoked potentials or middle-latency auditory evoked potentials were abolished did not awaken (100% specificity). All patients in whom mismatch negativity (MMN) was present awakened (100% specificity). MMN was superior to somatosensory evoked potentials for the prediction of awakening and had the best specificity and positive predictive value for awakening. On the decision tree, the awakening/nonawakening explicative variables were, by order of importance, MMN, pupillary reactivity, and somatosensory evoked potentials. CONCLUSIONS: There is a need to predict early and accurately awakening or nonawakening in postanoxic comas. Using sensory and cognitive evoked potentials to assess the functional condition of the brain, a prognostic tree for the prediction of awakening/nonawakening in severe anoxic coma has been designed. It is applicable to any patient in this condition and offers the possibility to predict with very high probability awakening when MMN, the earliest component of event-related potentials, is present and nonawakening when MMN and pupillary light reflex are absent or cortical components of somatosensory evoked potentials are abolished.

Adolescent↗
PubMed1993

On trees as equivalent cables.

By means of a suitable transformation, any passive dendritic tree may be reduced to an equivalent, possibly non-uniform cable. Under certain conditions the equivalent cable has disjoint sections of which only one communicates with the soma. Inputs that map on to the disconnected sections cannot be seen by the soma. Ralls's equivalent cylinder and its generalizations emerge naturally as the simplest cases of this behaviour. Even where, as is more usual, decomposition does not occur exactly the equivalent cable together with the input mapping from the tree to the cable provides a readily visualisable and intuitively appealing description of quite subtle relationships on the tree. The structure of the equivalent cable is dominated by approximate geometric symmetries of the tree. These symmetries cause well-defined subspaces of the total space of synaptic inputs to arrive at the soma at different times, thus allowing them, in principle, to be reflected, for example in the temporal statistics of the neurons' spike output.

Animals↗
PubMed1996

Chloroplast DNA phylogeography of the argan tree of Morocco.

Polymorphisms in the chloroplast genome of the argan tree (Sapotaceae), an endemic species of south-western Morocco, have been detected by restriction site studies of PCR-amplified fragments. A total of 12 chloroplast DNA (cpDNA) and two mitochondrial DNA (mtDNA) fragments were amplified and digested with a single restriction enzyme (HinfI). Polymorphisms were identified in six of the cpDNA fragments, whereas no mtDNA polymorphisms were detected in a survey of 95 individuals from 19 populations encompassing most of the natural range of the species. The cpDNA polymorphisms allowed the identification of 11 haplotypes. Two lineages, one in the south-east and the other in the north-west, divide the range of the argan tree into two distinct areas. The level of genetic differentiation measured at the haplotype level (GSTc = 0.60) (i.e. with unordered haplotypes) was smaller than when phylogenetic relationships were taken into account (NSTc = 0.71-0.74) (ordered haplotypes), indicating that population history must be considered in the study of the geographical distribution of cpDNA lineages in this species. If contrasted with the level of nuclear genetic differentiation measured in a previous study with isozymes (GSTn = 0.25), the results indicate a relatively high level of gene flow by seeds, or conversely a relatively low level of gene flow by pollen, as compared with other tree species. Goats and camels could have played an important role in disseminating the fruits of this tree.

DNA, Chloroplast↗
PubMed2006

Biomass partitioning and leaf N,P - stoichiometry: comparisons between tree and herbaceous current-year shoots.

We compare the biomass partitioning patterns and the nitrogen/phosphorus (N,P) stoichiometry of the current-year shoots of tree and herbaceous species and ask whether they scale in the same ways. Our analyses indicate that few statistically significant differences exist between the shoot biomass partitioning patterns of the two functional species-groups. In contrast, statistically significant N,P - stoichiometric differences exist between the two functional groups. Across all species, dry leaf mass scales nearly as the square of basal stem diameter and isometrically with respect to dry stem mass. However, total leaf N scales as the 1.37-power and as the 1.09-power of total leaf P across herbaceous and tree shoots, respectively. Therefore, tree shoots can be viewed as populations of herbs elevated by their older, woody herbaceous cohorts. However, tree leaf stoichiometry cannot be modelled in terms of herbaceous N,P - leaf stoichiometry.

Biomass↗
PubMed1978

Allergy to pollen from different deciduous trees in Sweden. An investigation with skin tests, provocation tests and the radioallergosorbent test (RAST) in springtime hay fever patients.

92 adult patients with springtime allergy were investigated with skin tests, provocation tests and the RAST. Allergen extracts from 12 different deciduous trees were used. Positive reactions, often of high intensity, were most often found with birch, alder, bog-myrtle, beech and hazel allergens whereas oak, aspen, linden, elm, sallow, maple and poplar allergens more often gave negative or only weak positive test results. Cross sensitizations were found between botanically related as well as between less related species of the trees. Almost all patients with a clinically relevant tree pollen allergy had positive provocation tests with birch pollen. No patient had positive reactions to all the 12 allergens included in the study. 68% had positive provocation tests with the combination birch, alder and hazel. It is concluded that for diagnostic screening purposes it is sufficient to use birch pollen allergen. If the majority of relevant tree pollens are to be included in a diagnostic or therapeutic programme in Western Sweden it should contain birch, alder, hazel, beech and bog-myrtle allergens.

Adolescent↗
PubMed2006

Clinical efficacy and safety of sublingual immunotherapy with tree pollen extract in children.

BACKGROUND: Subcutaneous immunotherapy has been the principal approach of immunotherapy in the treatment of allergic diseases. Several clinical studies with birch, alder or hazel pollen extract conducted as subcutaneous immunotherapy have been published suggesting a well-tolerated and clinically effective treatment. Only a few clinical studies of sublingual immunotherapy (SLIT) with these allergens have been published. This study investigated the clinical efficacy, safety and dose-response relationship of SLIT in children suffering from rhinoconjunctivitis with/without asthma. METHODS: Eighty-eight children (5-15 years) with a history of tree pollen-induced allergic rhinoconjunctivitis with/without seasonal asthma for >or=2 years were included. Allergy to tree pollen was confirmed by positive skin-prick test, positive specific IgE and positive conjunctival provocation test. The extract used was a glycerinated mixture of Betula verrucosa, Corylus avellana and Alnus glutinosa 100,000 SQ-U/ml. Children were randomized into three groups receiving SLIT 5 days a week for up to 18 months; dose group 1: accumulated weekly dose of 24,000 SQ-U; dose group 2: accumulated weekly dose of 200,000 SQ-U; and placebo. RESULTS: In the birch pollen season, dose group 2 showed a significant reduction of symptom (P = 0.01) and medication scores (P = 0.04) compared with placebo. Dose group 1 showed a significant reduction of symptom scores (P = 0.03). There were no statistical differences between dose groups 1 and 2. All children tolerated the treatment well. CONCLUSION: SLIT with tree pollen extract provided dose-dependent benefits in tree pollen-allergic children in terms of significantly reduced symptoms and medication use. The treatment was well tolerated.

Administration, Sublingual↗
PubMed2006

Testing metabolic ecology theory for allometric scaling of tree size, growth and mortality in tropical forests.

The theory of metabolic ecology predicts specific relationships among tree stem diameter, biomass, height, growth and mortality. As demographic rates are important to estimates of carbon fluxes in forests, this theory might offer important insights into the global carbon budget, and deserves careful assessment. We assembled data from 10 old-growth tropical forests encompassing censuses of 367 ha and > 1.7 million trees to test the theory's predictions. We also developed a set of alternative predictions that retained some assumptions of metabolic ecology while also considering how availability of a key limiting resource, light, changes with tree size. Our results show that there are no universal scaling relationships of growth or mortality with size among trees in tropical forests. Observed patterns were consistent with our alternative model in the one site where we had the data necessary to evaluate it, and were inconsistent with the predictions of metabolic ecology in all forests.

Biometry↗
PubMed2005

Links between tree species, symbiotic fungal diversity and ecosystem functioning in simplified tropical ecosystems.

We studied the relationships among plant and arbuscular mycorrhizal (AM) fungal diversity, and their effects on ecosystem function, in a series of replicate tropical forestry plots in the La Selva Biological Station, Costa Rica. Forestry plots were 12 yr old and were either monocultures of three tree species, or polycultures of the tree species with two additional understory species. Relationships among the AM fungal spore community, host species, plant community diversity and ecosystem phosphorus-use efficiency (PUE) and net primary productivity (NPP) were assessed. Analysis of the relative abundance of AM fungal spores found that host tree species had a significant effect on the AM fungal community, as did host plant community diversity (monocultures vs polycultures). The Shannon diversity index of the AM fungal spore community differed significantly among the three host tree species, but was not significantly different between monoculture and polyculture plots. Over all the plots, significant positive relationships were found between AM fungal diversity and ecosystem NPP, and between AM fungal community evenness and PUE. Relative abundance of two of the dominant AM fungal species also showed significant correlations with NPP and PUE. We conclude that the AM fungal community composition in tropical forests is sensitive to host species, and provide evidence supporting the hypothesis that the diversity of AM fungi in tropical forests and ecosystem NPP covaries.

Biodiversity↗
PubMed2005

Measuring tree root respiration using (13)C natural abundance: rooting medium matters.

Tree root respiration utilizes a major portion of the primary production in forests and is an important process in the global carbon cycle. Because of the lack of ecologically relevant methods, tree root respiration in situ is much less studied compared with above-ground processes such as photosynthesis and leaf respiration. This study introduces a new (13)C natural tracer method for measuring tree root respiration in situ. The method partitions tree root respiration from soil respiration in buried root chambers. Rooting media substantially influenced root respiration rates. Measured in three media, the fine root respiration rates of longleaf pine were 0.78, 0.27 and 0.18 mg CO(2) carbon mg(-1) root nitrogen d(-1) at 25 degrees C in the native soil, tallgrass prairie soil, and sand-vermiculite mixture, respectively. Compared with the root excision method, the root respiration rate of longleaf pine measured by the field chamber method was 18% higher when using the native soil as rooting medium, was similar in the prairie soil, but was 42% lower if in the sand-vermiculite medium. This natural tracer method allows the use of an appropriate rooting medium and is capable of measuring root respiration nondestructively in natural forest conditions.

Carbon Isotopes↗
PubMed1995

Antimicrobial effects of tea-tree oil and its major components on Staphylococcus aureus, Staph. epidermidis and Propionibacterium acnes.

Major components of two tea-tree oil samples were identified using thin layer and gas-liquid chromatography (TLC and GLC). Using a TLC-bioautographic technique, the tea-tree oils, terpinen-4-ol, alpha-terpineol and alpha-pinene were found to be active against Staphylococcus aureus, Staph. epidermidis and Propionibacterium acnes whereas cineole was inactive against these organisms. The MIC values of the three active compounds increased in the order alpha-terpineol < terpinen-4-ol < alpha-pinene for all three micro-organisms. MIC values of the tea-tree oils and terpinen-4-ol were lower for P. acnes than for the two staphylococci. This study supports the use of tea-tree oil in the treatment of acne, and demonstrates that terpinen-4-ol is not the sole active constituent of the oil.

Anti-Infective Agents, Local↗
PubMed2005

Carbon flux and growth in mature deciduous forest trees exposed to elevated CO2.

Whether rising atmospheric carbon dioxide (CO2) concentrations will cause forests to grow faster and store more carbon is an open question. Using free air CO2 release in combination with a canopy crane, we found an immediate and sustained enhancement of carbon flux through 35-meter-tall temperate forest trees when exposed to elevated CO2. However, there was no overall stimulation in stem growth and leaf litter production after 4 years. Photosynthetic capacity was not reduced, leaf chemistry changes were minor, and tree species differed in their responses. Although growing vigorously, these trees did not accrete more biomass carbon in stems in response to elevated CO2, thus challenging projections of growth responses derived from tests with smaller trees.

Atmosphere↗
PubMed2006

Bacterial diversity in tree canopies of the Atlantic forest.

We found an extraordinary level of bacterial biodiversity in the tree leaf canopy of a tropical Atlantic forest by using culture-independent molecular methods. Our survey suggests that each tree species selects for a distinct microbial community. Analysis of the bacterial 16S ribosomal RNA gene sequences revealed that about 97% of the bacteria were unknown species and that the phyllosphere of any one tree species carries at least 95 to 671 bacterial species. The tree canopies of tropical forests likely represent a large reservoir of unexplored microbial diversity.

Bacteria↗
PubMed1967

The ginkgo, the most ancient living tree. The resistance of Ginkgo biloba L. to pests accounts in part for the longevity of this species.

Fossil records clearly demonstrate that the group of trees known as Ginkgoales, of which today Ginkgo biloba is the sole living member, date back over 200 million years. Ginkgo bilboa itself is one of the oldest of living plants (4). It appears that the longevity of this tree and its long reproductive period are at least partially responsible for the persistence of the species. The resistance of these trees to pests such as insects, bacteria, viruses, and fungi has been studied. It is believed that their unusual resistance to pests accounts in part for the longevity of the trees and also, in turn, for the longevity of the species.

Air Pollution↗