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PubMed2004

Transport of airborne pollen into the city of Thessaloniki: the effects of wind direction, speed and persistence.

We examined the effect of the wind vector analyzed into its three components (direction, speed and persistence), on the circulation of pollen from different plant taxa prominent in the Thessaloniki area for a 4-year period (1996-1999). These plant taxa were Ambrosia spp., Artemisia spp., Chenopodiaceae, Corylus spp., Cupressaceae, Olea europaea, Pinaceae, Platanus spp., Poaceae, Populus spp., Quercus spp., and Urticaceae. Airborne pollen of Cupressaceae, Urticaceae, Quercus spp. and O. europaea make up approximately 70% of the total average annual pollen counts. The set of data that we worked with represented days without precipitation and time intervals during which winds blew from the same direction for at least 4 consecutive hours. We did this in order to study the effect of the different wind components independently of precipitation, and to avoid secondary effects produced by pollen resuspension phenomena. Factorial regression analysis among the summed bi-hourly pollen counts for each taxon and the values of wind speed and persistence per wind direction gave significant results in 22 cases (combinations of plant taxa and wind directions). The pollen concentrations of all taxa correlated significantly with at least one of the three wind components. In seven out of the 22 taxon-wind direction combinations, the pollen counts correlated positively with wind persistence, whereas this was the case for only two of the taxon-wind speed combinations. In seven cases, pollen counts correlated with the interaction effect of wind speed and persistence. This shows the importance of wind persistence in pollen transport, particularly when weak winds prevail for a considerable part of the year, as is the case for Thessaloniki. Medium/long-distance pollen transport was evidenced for Olea (NW, SW directions), Corylus (NW, SW), Poaceae (SW) and Populus (NW).

Environmental Monitoring↗
PubMed2006

Role of species diversity and secondary compound complementarity on diet selection of Mediterranean shrubs by goats.

Goats foraging on Mediterranean shrubs containing secondary compounds (toxins) may consume a variety of shrubs that contain different phytotoxins, thereby increasing shrub intake and avoiding toxicosis. We conducted eight experiments to examine whether goats offered different mixtures of shrubs containing different phytotoxins (tannins and saponins) would consume more shrub biomass than goats offered one shrub a single phytotoxin (tannin or saponin). In the first three experiments, goats fed a mixture of three tannin-rich shrubs (Quercus ilex, Arbutus unedo, and Pistacia lentiscus) ate more foliage than goats offered only one shrub (23.2 vs. 10.7 g/kg BW; 25.2 vs. 13.4 g/kg BW, and 27.9 vs. 7.9 g/kg BW), regardless of tannin concentration in individual shrub species. Goats also consumed more foliage when offered the same three tannin-rich shrubs than when offered the saponin-rich shrub Hedera helix (25.4 vs. 8.0 g/kg BW). However, goats offered a mixture of the same three tannin-rich shrubs consumed less foliage than goats offered a mixture of two shrubs containing tannins and saponins: Quercus and Hedera (21.6 vs. 27.1 g/kg BW), Arbutus and Hedera (21.8 vs. 27.1 g/kg BW), and Pistacia and Hedera (19.7 vs. 22.0 g/kg BW). Comparison of intake of shrubs containing only tannins or saponins to intake of shrubs containing both tannins and saponins indicated that goats consumed more total biomass when fed with shrubs with both classes of compounds than with either tannins or saponins alone. Our results suggest that goats can increase intake of Mediterranean shrubs high in secondary compounds by selecting those with different classes of phytotoxins. Simultaneous ingestion of shrubs containing tannins and saponins may promote chemical interactions that inhibit toxic effects of these phytotoxins in the intestinal tract. In addition to complementary interactions between tannins and saponins, biological diversity within Mediterranean maquis vegetation also plays a positive role in increasing shrub intake by goats.

Animals↗
PubMed2004

Analysis of serpentinophytes from north-east of Portugal for trace metal accumulation--relevance to the management of mine environment.

In north-east of Portugal, the serpentinized area is about 8000 ha with a characteristic geology and flora. The serpentine plant community and respective soils were analyzed to examine the trace metal budget in different tissues of the plants exhibiting resistance to trace metals. One hundred and thirty five plant species belonging to 39 families and respective soils have been analyzed for total Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn. Substantial amounts of Ni, Cr, Co and Mn were detected in plant tissues which are listed below: NI: Alyssum serpyllifolium (38105); Bromus hordeaceus (1467); Linaria spartea (492); Plantago radicata (140); Lavandula stoechas (118) and Cistus salvifolius (114); CR: L. spartea (706.7); Ulmus procera (173.4); A. serpyllifolium (129.3); Cistus ladanifer (40.8); L. stoechas (29.5); P. radicata (27.81); Setariopsis verticillata (25.7); Plantago lanceolata (24); Digitalis purpurea (23.4); Logfia minima (23.1); Arenaria querioides (23); Hieracium peleteranum (22.7); Arenaria montana (14.5); CO: A. serpyllifolium (145.1); L. spartea (63.2); P. radicata (10.4); H. peleteranum (7.3); Lepidium heterophyllum (6.9); A. querioides (6.6); C. salvifolius (6.5); C. ladanifer (6.3); L. stoechas (6.1); Anthyllis lotoides (6.1); L. minima (6.1); Euphorbia falcata (5.7) and B. hordeaceus (5.6); MN: A. serpyllifolium (830); L. spartea (339); L. stoechas (187.1); L. minima (182.7); Castanea sativa (125); Spergula pentandra (124); P. radicata (119); Cytisus striatus (115.4); Quercus pyrenaica (110); Teucrium scorodonia (109.4); Fraxinus vulgaris (109); Anthyllis sampaiana (108); Quercus ilex (108). The significance of serpentine flora, need for conservation of these fragile and environmentally invaluable plant resources for possible use for in situ remediation of metalliferous substrates are presented in this paper.

Environment↗
PubMed2005

Inhibition of Naja kaouthia venom activities by plant polyphenols.

Plant polyphenols from the aqueous extracts of Pentace burmanica, Pithecellobium dulce, Areca catechu and Quercus infectoria were tested for their inhibitory activities against Naja kaouthia (NK) venom by in vitro neutralization method. The first three extracts could completely inhibit the lethality of the venom at 4 LD50 concentration and the venom necrotizing activity at the minimum necrotizing dose while also inhibited up to 90% of the acetylcholinesterase activity of NK venom at much lower tannin concentrations than that of Quercus infectoria. The ED50 of plant tannins in inhibiting NK venom activities varied according to condensed tannins and their content in the extracts. Molecular docking of the complexes between alpha-cobratoxin and either hydrolysable or condensed tannins at their lowest energetic conformations were proposed. The anti-venom activities of these plant polyphenols by selectively blocking the nicotinic acetylcholine receptor and non-selectively by precipitation of the venom proteins were suggested.

Animals↗
PubMed2006

The biogenic volatile organic compounds emission inventory in France: application to plant ecosystems in the Berre-Marseilles area (France).

An inventory describing the fluxes of volatile organic compounds (VOCs), isoprene and monoterpenes, and other VOCs (OVOCs) from the biosphere to the atmosphere, has been constructed within the framework of the ESCOMPTE project (fiEld experimentS to COnstrain Models of atmospheric Pollution and Transport of Emissions). The area concerned, located around Berre-Marseilles, is a Mediterranean region frequently subject to high ozone concentrations. The inventory has been developed using a fine scale land use database for the year 1999, forest composition statistics, emission potentials from individual plant species, biomass distribution, temperature and light intensity. The seasonal variations in emission potentials and biomass were also taken into account. Hourly meteorological data for 1999 were calculated from ALADIN data and these were used to predict the hourly isoprene, monoterpene and OVOC fluxes for the area on a 1 kmx1 km spatial grid. Estimates of annual biogenic isoprene, monoterpene and OVOC fluxes for the reference year 1999 were 20.6, 38.9 and 13.3 kt, respectively, Quercus pubescens, Quercus ilex, Pinus halepensis and garrigue vegetation are the dominant emitting species of the area. VOC emissions from vegetation in this region contribute approximately 94% to the NMVOC (non-methane volatile organic compounds) of natural origin and are of the same order of magnitude as NMVOC emissions from anthropogenic sources. These results complete the global ESCOMPTE database needed to make an efficient strategy for tropospheric ozone reduction policy.

Ecosystem↗
PubMed2000

Analysis of oak tannins by liquid chromatography-electrospray ionisation mass spectrometry.

Extractable tannins were analysed by liquid chromatography-electrospray ionisation mass spectrometry in two oak species, North American white oak (Quercus alba) and European red oak (Quercus robur). They mainly included various glucose gallic and ellagic acid esters. The structures were partially determined, and they included grandinin/roburin E, castalagin/vescalagin, gallic acid, valoneic acid bilactone, monogalloyl glucose, digalloyl glucose, trigalloyl glucose, ellagic acid rhamnose, quercitrin and ellagic acid.

Chromatography, Liquid↗
PubMed1986

A study of oak-pollen production and phenology in northern California: prediction of annual variation in pollen counts based on geographic and meterologic factors.

To assess the characteristics of oak-pollen production and dispersal, 9 years of weekly volumetric air sampling, with modified swing-shield rotoslide pollen samplers, were obtained in San Francisco and San Jose, Calif. The Mediterranean climate of coastal California supports 9 million acres of oaks of nine different species. The major pollen contributors in the two sampling areas are coast live oak (Quercus agrifolia Neé) and valley oak (Quercus lobata neé). Sampling data indicate that grains may be wind transported at least 16 km (10 miles). A strong correlation exists between pollen capture and total rainfall a full year before pollen release. The correlation is statistically significant, based on a Spearman rank test. A positive regression line slope demonstrates that the greater the precipitation, the stronger the stimulus for pollen production. The median count can be predicted within a factor of two with high probability a full year before release. During most seasons, the peak pollen collection from coast live oak and valley oak occurs in early April. A second peak production period, in mid-May, represents the conglomerate of other oak-pollen types. However, there are major yearly differences in the relative amounts of pollen released during these two periods. Consequently, individual oak pollinosis may depend as much on variable production by the major species as on the total quantity of airborne oak pollen. These data will help clinicians predict and prepare for the intensity of the oak-pollen season and explain seasonal variations in clinical symptoms from year to year. The question of cross-reacting and specific allergens among oak species can be answered by RAST-inhibition studies.(ABSTRACT TRUNCATED AT 250 WORDS)

Allergens↗
PubMed1995

Allergenic pollen pollinosis in Madrid.

OBJECTIVE: A 15-year pollen count was performed in the atmosphere of Madrid, Spain, to determine the months in which the highest concentrations of allergenic pollens occur. METHODS: Pollen counts were done with a Burkard spore trap (Burkard Manufacturing, Rickmansworth, Herst., U.K.). The results were subsequently compared with results of skin tests in patients with pollinosis born and living in and around Madrid. RESULTS: The highest airborne presence (percent of total yearly pollen counts, mean of counts from 1979 to 1993) was for Quercus spp. (17%); followed by Platanus spp. (15%), Poaceae (15%), Cupressaceae (11%), Olea spp. (9%), Pinus spp. (7%), Populus spp. (4%), and Plantago spp. (4%). The most predominant pollens from January to April are tree pollens (Cupressaceae, Alnus, Fraxinus, Ulmus, Populus, Platanus, and Morus), although these are also abudant in May and June (Quercus, Olea, and Pinus spp.). The grass pollination period shows a double curve: the first peak occurs from February to April (8% of yearly grasses), and the second peak occurs from May to July (90% of yearly grasses). Among allergenically significant weeds, the most notable is Plantago; in contrast, Rumex, Urticaceae, Cheno-Amaranthaceae, and Artemisia spp. have very low concentrations (< or = 2% yearly total pollens). The most significant allergenic pollen is that of grasses, with a prevalence of positive prick test results of 94%, followed by Olea europaea (61%), Plantago lagopus (53%), Platanus hybrida (52%), and Cupressus arizonica (20%). CONCLUSION: The population of Madrid is exposed to high concentrations of allergenic pollen from February to July, although the most intense period is from May to June. Grass pollens are the most important cause of pollinosis in this area.

Adolescent↗
PubMed2001

Immunocytochemical studies on the origin and deposition sites of hydrolyzable tannins.

Two specific antibodies, directed toward hydrolyzable tannins, i.e. polygalloylated or oxidized derivatives of 1,2,3,4,6-penta-O-galloylglucose, and toward an acyltransferase from oak leaves that catalyzes the biosynthesis of this principal precursor, were used in immunocytochemical studies to determine the intracellular sites of origin and deposition of these polyphenolic plant constituents. Immunostaining of semi-thin sections from leaves and roots of young pedunculate oak (Quercus robur, syn. Quercus pedunculata) plants with marker enzymes and immunogold labeling of ultra-thin sections revealed immunoreactive sites for both enzyme and hydrolyzable tannins in chloroplasts, cell walls and intercellular spaces. The latter non-cytoplasmic (apoplast) compartments displayed characteristic aggregations of these two epitopes, thus indicating an intimate association of the biocatalyst and its products. Identical distribution patterns for hydrolyzable tannins were observed in leaves of Rhus typhina (sumac) and Tellima grandiflora (fringe cups) which, however, displayed no affinity toward the galloyltransferase antibody that had been raised against enzyme from oak. Controls with spinach leaves, known to be devoid of tannins, were inactive in all cases. The conclusion that, besides chloroplasts, cell walls and intercellular space serve as sites for the biosynthesis and deposition of hydrolyzable tannins was confirmed by analyzing extracts from these non-cytoplasmic compartments.

Journal Article↗
PubMed2003

Epiphytic lichens as sentinels for heavy metal pollution at forest ecosystems (central Italy).

The results of a study using epiphytic lichens (Parmelia caperata) as sentinels for heavy metal deposition at six selected forest ecosystems of central Italy are reported. The woods investigated are characterized by holm oak (Quercus ilex), turkey oak (Quercus cerris) and beech (Fagus sylvatica) and represent the typical forest ecosystems of central Italy at low, medium and high elevations, respectively. The results showed that levels of heavy metals in lichens were relatively low and consequently no risk of heavy metal air pollution is expected for the six forest ecosystems investigated. However, for two of them there are indications of a potential risk: the beech forest of Vallombrosa showed signs of contamination by Pb as a consequence of vehicle traffic due to the rather high touristic pressure in the area, and the holm oak forest of Cala Violina showed transboundary pollution by Mn, Cr and Ni originating from the steel industry in Piombino. Epiphytic lichens proved to be very effective as an early warning system to detect signs of a changing environment at forest ecosystems.

Chromium↗
PubMed2001

A comparative, volumetric survey of airborne pollen in Philadelphia, Pennsylvania (1991-1997) and Cherry Hill, New Jersey (1995-1997).

BACKGROUND: Aeroallergen sampling provides information regarding the onset, duration, and severity of the pollen season that clinicians use to guide allergen selection for skin testing and treatment. OBJECTIVE: This atmospheric survey reports: 1) airborne pollen contributors in Philadelphia, Pennsylvania (1991 to 1997) and suburban Cherry Hill, New Jersey (1995 to 1997); 2) pollen onset, duration, and peak level; and 3) the relationship between airborne pollen and selected meteorologic variables. METHODS: At both locations, separated by 11 km. sampling was performed with a volumetric Rotorod Sampler (Sampling Technologies, Minnetonka, MN). RESULTS: In Philadelphia and Cherry Hill, respectively, 3-year average measurements included 75.0 and 74.2% tree pollen, 10.2 and 8.3% grass pollen, and 14.8 and 17.5% weed pollen. Prominent airborne pollen taxa were Acer, Quercus, Betula, Pinus, Cupressaceae, Poaceae, Ambrosia, and Rumex. The tree, grass, and weed pollen seasons extended from mid-March to mid-June, late April to mid-June, and mid-August to late September, respectively. A secondary Poaceae pollen peak occurred in September. There was a statistically significant correlation between simultaneous weekly average pollen levels in Philadelphia and in Cherry Hill (Acer, r(p) = 0.987, Quercus, r(p) = 0.645, Betula, r(p) = 0.896, Pinus, r(p) = 0.732, Cupressaceae, r(p) = 0.695, Poaceae, r(p) = 0.950, Ambrosia, r(p) = 0.903, and Rumex, r(p) = 0.572, P <0.001). Daily Poaceae pollen levels were positively influenced by same-day high temperature (r(s) = 0.333 in Philadelphia and r(s) = 0.426 in Cherry Hill, P < 0.05). Daily Ambrosia pollen levels were inversely influenced by same-day total precipitation (r(s) = -0.174 in Philadelphia and r(s) = -0.257 in Cherry Hill, P < 0.05). CONCLUSIONS: This is the first volumetric survey performed in either Philadelphia or Cherry Hill. Copious amounts of airborne pollen were seen from late April to early May and in early September. Pollen onset, duration, and year-to-year variability were similar at both sites. An awareness of local aeroallergen patterns is critical in the effective testing and treatment of atopic individuals.

Air Pollution↗
PubMedDate not supplied

Ice storm damage and early recovery in an old-growth forest.

We quantified the damage caused by a major ice storm to individual trees in two 1-ha permanent plots located at Mont St. Hilaire in southwestern Québec, Canada. The storm, which occurred in January 1998, is the worst on record in eastern North America; glaze ice on the order of 80-100 mm accumulated at our study site. All but 3% of the trees (DBH > or = 10 cm) lost at least some crown branches, and 35% lost more than half their crown. Damage to trees increased in the order: Tsuga canadensis, Betula alleghaniensis, Ostrya virginiana, Acer saccharum, Fagus grandifolia, Quercus rubra, Betula papyrifera, Acer rubrum, Tilia americana, and Fraxinus americana. Only 22% of the saplings and small trees (4 cm < DBH < 10 cm) escaped being broken or pinned to the ground by falling material. Levels of damage generally were greater in an exposed ridge top forest than in a cove protected from wind. By August 1999 only 53% of the trees had new shoots developing from the trunk or broken branches; among the more dominant canopy trees, Fagus grandifolia had the least sprouting and Acer saccharum and Quercus rubra the most. We anticipate and will monitor both significant turnover in the tree community and some shift in composition of the canopy dominants.

Disasters↗
PubMed2001

Description of the male and first-stage juvenile of Longidorus intermedius Kozlowska & Seinhorst, 1979 (Nematoda: Dorylaimida), and notes on its morphology and distribution.

Longidorus intermedius Kozlowska & Seinhorst, 1979 is redescribed from specimens recovered from oak (Quercus L.) forests in Bulgaria. The male and the first-stage juvenile were recorded for the first time, as were populations from Macedonia and Turkey. L. intermedius is identified here as the first species in the genus with only three juvenile stages and a pan-European distribution. The species was recovered from 36 of 46 oak forests in Bulgaria, found associated with each of nine oak species sampled and reached population densities of up to 289 specimens per 200 cm(3) of soil. The distribution of L. intermedius in Bulgaria, and in other countries, suggests that this species, like Xenocriconemella macrodora (Taylor, 1936) and probably L. aetnaeus Lamberti, Agostinelli & Vinciguerra, 1986, can be used as an ecological indicator for habitats where Quercus associations represent a primary vegetation type.

Animals↗
PubMedDate not supplied

Effects of tannins on digestion and detoxification activity in gray squirrels (Sciurus carolinensis).

Acorn tannins may affect food preferences and foraging strategies of squirrels through effects on acorn palatability and digestibility and squirrel physiology. Captive eastern gray squirrels (Sciurus carolinensis) were fed 100% red oak (Quercus rubra) or white oak (Quercus alba) acorn diets to determine effects on intake, digestion, and detoxification activity. Red oak acorns had higher phenol and tannin levels, which may explain the lower dry matter intakes and apparent protein digestibilities and the higher glucuronidation activities observed in squirrels. Although the white oak acorn diet had lower apparent protein digestibilities than the reference diet, it did not suppress dry matter intake for a prolonged period or stimulate glucuronidation. Negative physiological effects of a 100% red oak acorn diet suggest gray squirrels may require other foods to dilute tannin intake and provide additional nutrients. To distinguish the roles of different tannin types in the observed effects of acorn diets on squirrels, squirrels were fed rat chow containing no tannins, 4% or 8% tannic acid (hydrolyzable tannin), or 3% or 6% quebracho (condensed tannin). Apparent protein digestibilities were reduced by tannic acid and quebracho diets. Only the 8% tannic acid diet tended to increase glucuronidation. Specific effects of tannins may largely depend on tannin type, composition, and source and on other nutritional and physiological factors.

Animals↗
PubMed2003

Ecophysiological relevance of cuticular transpiration of deciduous and evergreen plants in relation to stomatal closure and leaf water potential.

The water permeability of the leaves of three deciduous plants (Acer campestre, Fagus sylvatica, Quercus petraea) and two evergreen plants (Hedera helix, Ilex aquifolium) was analysed in order to assess its role as a mechanism of drought resistance. Cuticular permeances were determined by measurement of the water loss through adaxial, astomatous leaf surfaces. Minimum conductances after complete stomatal closure were obtained by leaf drying curves. The comparison of the water permeabilities determined with these two experimental systems revealed good agreement in the case of Acer, Fagus, Quercus, and Ilex. For Hedera the minimum conductance was 3-fold higher than the cuticular permeance indicating a significant contribution of residual stomatal transpiration. The leaf water potential was measured as a function of water content and analysed by pressure-volume curves. The influence of water potential as a component of the driving force for transpirational water loss was assessed in order to identify modifications of the cuticular barrier by the leaf water content. The ecophysiological meaning of the water relations parameters describing transpiration under drought conditions (cuticular transpiration, minimum transpiration, residual stomatal transpiration, effect of leaf water content on transpiration) and the water relations parameters derived from pressure-volume curves (osmotic potential at full saturation, turgor loss point, bulk modulus of elasticity) are discussed with regard to adaptations for drought resistance.

Disasters↗
PubMed1992

The impact of water and nutrient deficiencies on the growth, gas exchange and water relations of red oak and chestnut oak.

Red oak (Quercus rubra), a mesic species, and chestnut oak (Quercus prinus), a xeric species, were grown in a greenhouse with and without fertilizer (F+ and F-, respectively) and subjected to a 10-week drydown (W-) or kept well watered (W+). In both species, fertilized seedlings exhibited greater reductions in mean net photosynthesis (A), leaf conductance (g(wv)), leaf water potential (Psi(leaf)) and water use efficiency (WUE) during the drydown than unfertilized seedlings. In the W- treatments, red oak showed greater reductions in A, g(wv) and Psi(leaf) than chestnut oak. Differential fertilization of the seedlings of both species had a greater effect on tissue water relations than differential watering. During the latter weeks of the drydown, there was no osmotic adjustment in red oak, but chestnut oak in the F+/W- treatment had significantly lower osmotic potentials at full and zero turgor than seedlings in any of the other treatments. The results indicate that high nutrient availability does not improve the drought tolerance of these two oak species.

Journal Article↗
PubMed1993

Canopy dynamics and aboveground production of five tree species with different leaf longevities.

Canopy dynamics and aboveground net primary production (ANPP) were studied in replicated monospecific and dual-species plantations comprised of species with different leaf longevities. In the monospecific plantations, leaf longevity averaged 5, 6, 36, 46 and 66 months for Quercus rubra L., Larix decidua Miller, Pinus strobus L., Pinus resinosa Ait. and Picea abies (L.) Karst., respectively. Specific leaf area, maximum net photosynthesis per unit mass (A/mass), leaf N per unit mass (N(leaf)/mass) and maximum net photosynthesis on a leaf N basis (A/N(leaf)) were inversely correlated to leaf longevity (r(2) = 0.92-0.97, 0.91, 0.88 and 0.80, respectively). Maximum net photosynthesis per unit area (A/area) was not correlated to leaf longevity, whereas leaf N per unit area (N(leaf)/area) was positively correlated to leaf longevity (r(2) = 0.95). For a similar-diameter conifer, species with long-lived foliage supported a greater foliage mass than species with short-lived foliage; however, Quercus rubra did not follow this pattern. At the stand level, total foliage mass ranged from 3.3 to 30.5 Mg ha(-1) and was positively correlated (r(2) = 0.97) to leaf longevity. Leaf area index (LAI) was also positively correlated (r(2) = 0.82) to leaf longevity. Production efficiency (ANPP/LAI) was inversely related to leaf longevity and positively related to A/mass. Aboveground biomass and net primary production differed significantly (P < 0.05) among the five species but were not correlated to leaf longevity, total foliage mass or leaf area. In monospecific plantations, stem NPP for Larix decidua was 17% greater than for Pinus strobus and 14% less than for Picea abies, but in mixed-species plantations stem NPP for Larix decidua was 62 and 85% greater than for Pinus strobus and Picea abies, respectively. Similar aboveground net primary production rates can be attained by tree species with different leaf longevities because of trade-offs resulting from different structural and physiological leaf and canopy characteristics that are correlated to each other and to leaf longevity.

Journal Article↗
PubMed1996

Stem respiration in a closed-canopy upland oak forest.

Stem respiration was measured throughout 1993 on 56 mature trees of three species (Quercus alba L., Quercus prinus L., and Acer rubrum L.) in Walker Branch Watershed, Oak Ridge, Tennessee. A subset of the trees was remeasured during 1994. Diameter increments, stem temperatures and soil water were also monitored. Respiration rates in the spring and summer of 1993 tracked growth rate increments, except during a drought when growth dropped to zero and respiration increased to its highest rate. During the dormant season, rates of total stem respiration (R(t)) tended to be greater in large trees with thick sapwood but no such trend was observed during the growing season. Before and after the growing season, respiration rates correlated well with stem temperatures. Estimated values of Q(10) were 2.4 for the two oak species and 1.7 for red maple. The Q(10) values were used along with baseline respiration measurements and stem temperatures to predict seasonal changes in maintenance respiration (R(m)). In red maple, annual total R(m) accounted for 56 and 60% of R(t) in 1993 and 1994, respectively. In chestnut oak, R(m) accounted for 65 and 58% of R(t) in 1993 and 1994, respectively. In white oak, R(m) accounted for 47 and 53% of R(t) in 1993 and 1994, respectively. Extrapolating these data to the stand level showed that woody tissue respiration accounted for 149 and 204 g C m(-2) soil surface year(-1) in 1993 and 1994, respectively.

Journal Article↗