Needle Surface Area Research Articles

Shoot structure and photosynthetic efficiency along the light gradient in a Scots pine canopy.

We examined the effects of structural and physiological acclimation on the photosynthetic efficiency of Scots pine (Pinus sylvestris L.) shoots. We estimated daily light interception (DLI) and photosynthesis (DPHOT) of a number of sample shoots situated at different positions in the canopy. Photosynthetic efficiency (epsilon) was defined as the ratio of DPHOT to the potential daily light interception (DLI(ref)) defined as the photosynthetically active radiation (PAR) intercepted per unit area of a sphere at the shoot location. To calculate DLI(ref), DLI and DPHOT, the radiation field surrounding a shoot in the canopy was first modeled using simulated directional distributions of incoming PAR on a clear and an overcast day, and estimates of canopy gap fraction in different directions provided by hemispherical photographs. A model of shoot geometry and measured data on shoot structure and photosynthetic parameters were used to simulate the distribution of PAR irradiance on the needle surface area of the shoot. Photosynthetic efficiency (epsilon) was separated into light-interception efficiency (epsilon(I) = DLI/DLI(ref)) and conversion efficiency (epsilon(PHOT) = DPHOT/DLI). This allowed us to quantify separately the effect of structural acclimation on the efficiency of photosynthetic light capture (epsilon(l)), and the effect of physiological acclimation on conversion efficiency (epsilon(PHOT)). The value of epsilon increased from the top to the bottom of the canopy. The increase was largely explained by structural acclimation (higher epsilon(I)) of the shade shoots. The value of epsilon(PHOT) of shade foliage was similar to that of sun foliage. Given these efficiencies, the clear-day value of DPHOT for a sun shoot transferred to shade was only half that of a shade shoot at its original position. The method presented here provides a tool for quantitatively estimating the role of acclimation in total canopy photosynthesis.

Comparative study of two spruce species in a polluted mountainous region

Summary Tolerance to pollution and climatic conditions are compared in Colorado blue spruce ( Picea pungens ) and Norway spruce ( Picea abies ) from two adjacent stands in the Krušné Hory Mountains, Czech Republic. The anatomy of needles was described quantitatively using image analysis, and the content of photosynthetic pigments, accumulation of lignin and phenolics, and reflective properties of needles of the two species were compared. Anatomical and morphological adaptations of Colorado blue spruce needles (i.e. lower needle surface area: volume ratio) suggested greater potential resistance to air pollution than Norway spruce. However, no difference in the degree of cell damage was recorded. Although concentrations of chlorophyll, carotenoids and their ratios were similar, lignification and phenolic accumulation was greater in Norway spruce. The red edge inflection point, as well as stress indices and reflectance ratios, suggested an age‐dependent increase in needle damage of both species. Needles of young Colorado blue spruce and Norway spruce exhibit the same degree of damage in response to air pollutants.

Nitrogen Increases Fresh Weight and Retail Value of Fraser Fir Christmas Trees

Abstract. Abies fraseri (Pursh) Poir. Christmas trees were fertilized for 5 years with four levels of N (0, 56, 113, or 170 kg·ha-1 per year) in spring, fall, or equally split between spring and fall. Nitrogen did not affect leader length, number of leaders, or bud frequency on the upper (distal) portion of the leader. Nitrogen increased bud frequency on the lower (proximal) 20 cm of the leader in only 1 of 3 years of measurement. All application schedules increased the number of apical buds on branches, whereas the number of lateral buds was increased only by spring applications. Nitrogen increased tree fresh weight and retail value as well as weight, length, and surface area of needles. Foliar N concentrations in the fall varied with fertilization schedule, and were higher in November than in October.

Photosynthetic utilization efficiency of absorbed photosynthetically active radiation by Scots pine and birch forest stands in the southern Taiga.

Absorption and utilization of photosynthetically active radiation (PAR) were investigated in Scots pine (Pinus sylvestris L.) and birch (Betula pendula Roth.) stands that were 41 years old at the end of the experimental period. Canopy depth of the Scots pine stand was about half that of the birch stand (6.5 versus 11.0 m), but absorption of PAR was similar in the two stands. The Scots pine forest canopy, with a leaf area index of 8.9, absorbed 90% of the incoming PAR (APAR), whereas the birch forest canopy, with a leaf area index of 5.9, absorbed 92% of APAR. During maximum foliage development, the upper Scots pine canopy absorbed more PAR than the upper birch canopy (75 versus 66%). The upper, middle and lower layers of the Scots pine canopy contained 37, 48 and 15% of the total needle surface area, respectively. The corresponding distribution of foliage surface area in the three layers of the birch canopy was 50, 30 and 20%, respectively. Measurements of photosynthetic rate were combined with estimates of leaf area index and stand phytomass to determine rates of primary production on a sunny day, a cloudy day, and on an annual basis. The energy equivalents of short- and long-term carbon gain were used with determinations of APAR to calculate photosynthetic utilization efficiency. Throughout the growing season, photosynthetic utilization efficiency of APAR in the upper canopy layer of the Scots pine forest was almost twice that in the lower canopy layer. In the birch forest, photosynthetic utilization efficiency was greater in the lower canopy layer than in the upper canopy layer. In all cases, utilization efficiency was higher in the birch stand than in the Scots pine stand (52 versus 29 J kJ(-1)). Taking account of respiration of the non-photosynthetic parts of each stand (night respiration of needles or leaves; respiration of branches, trunk and roots), estimated utilization efficiency of APAR for net primary production was 11 J kJ(-1) for Scots pine and 19 J kJ(-1) for birch. Solar conversion ratios, expressed as whole-plant net primary productivity per unit of APAR for the growing season, were 0.81 g MJ(-1) for Scots pine and 0.93 g MJ(-1) for birch.

Nitrogen Increases Fresh Weight and Retail Value of Fraser Fir Christmas Trees

Abies fraseri (Pursh) Poir. Christmas trees were fertilized for 5 years with four levels of N (0, 56, 113, or 170 kg·ha–1 per year) in spring, fall, or equally split between spring and fall. Nitrogen did not affect leader length, number of leaders, or bud frequency on the upper (distal) portion of the leader. Nitrogen increased bud frequency on the lower (proximal) 20 cm of the leader in only 1 of 3 years of measurement. All application schedules increased the number of apical buds on branches, whereas the number of lateral buds was increased only by spring applications. Nitrogen increased tree fresh weight and retail value as well as weight, length, and surface area of needles. Foliar N concentrations in the fall varied with fertilization schedule, and were higher in November than in October.

THE PERCENT OF CORES POSITIVE FOR CANCER IN PROSTATE NEEDLE BIOPSY SPECIMENS IS STRONGLY PREDICTIVE OF TUMOR STAGE AND VOLUME AT RADICAL PROSTATECTOMY

Pretreatment clinical staging of prostatic adenocarcinoma is important due to the increasing use of nonsurgical treatment options. Using multivariate analysis we assessed the predictive value of biopsy cores positive for cancer as a percent of all cores obtained as well as the percent surface area of needle cores involved with tumor for determining tumor volume and pathological stage at radical prostatectomy. Candidate variables for the multivariate model included patient age, clinical disease stage, serum prostate specific antigen (PSA) and Gleason score of cancer in the needle biopsy. We reviewed prostate needle biopsy findings in 207 consecutive patients who subsequently underwent radical retropubic prostatectomy. Each biopsy specimen was assessed for tumor involvement by calculating the percent of cores positive for cancer, percent surface area involved in all cores and Gleason score. Initial serum PSA and preoperative clinical disease stage were incorporated with biopsy results into a multivariate model to determine the parameters most predictive of pathological stage and tumor volume at radical retropubic prostatectomy. Of the 207 patients 152 (73.4%) had organ confined cancer and 55 (26.6%) had extraprostatic extension (pathological stages T2 and T3 or greater, respectively). Preoperative clinical staging information was available in 195 cases, in which disease was clinically confined and not confined in 184 (94.4%) and 11 (5.6%), respectively. Needle biopsy revealed a surface area of cancer ranging from less than 5% in 69 patients (33.3%) to 90% (mean 16, median 10). Univariate analysis demonstrated that the risk of extraprostatic extension was predicted by preoperative serum PSA (p = 0.027), the percent of cores and percent of surface area positive for cancer (p <0.0001), and Gleason score (p = 0.0009). Clinical stage approached significance (p = 0.071). Multivariate analysis showed that the percent of positive cores (p = 0.0003), initial serum PSA (p = 0.005) and Gleason score of cancer in the needle biopsy (p = 0.03) were the only parameters that jointly predicted pathological stage (T2 versus T3). Percent of tumor surface area involvement in the needle biopsies did not add any more information after the percent of positive cores was known. Univariate analysis revealed that the percent of cores positive for cancer (Spearman r = 0.52, p <0.0001), Gleason score (Spearman r = 0.34, p <0.0001) and initial serum PSA (Spearman r = 0.24, p = 0.003) were predictive of log tumor volume at radical prostatectomy, while clinical stage was not (rank sum test p = 0.14). On multivariate analysis the percent of positive cores (p <0.0001), Gleason score (p <0.0001) and initial serum PSA (0.0033) were the only variables that jointly were predictive of tumor volume. The percent of needle biopsy cores and surface area positive for cancer are the strongest predictors of pathological stage and tumor volume on multivariate analysis incorporating preoperative serum PSA and Gleason score.

SEM–EDS image analysis as a tool for scoring the epicuticular wax tube distribution on Pinus sylvestris needles—evaluation using a UV-B field experiment

The wax tube distribution (WTD) of Scots pine ( Pinus sylvestris) needles in an UV-B experiment was studied under a scanning electron microscope (SEM) with the help of the image-acquiring, processing and analysing program of an energy-dispersive (EDS) analyser. To increase the contrast between the areas covered by structural wax and amorphous wax deposits, processed (edge detection, smoothing and thresholding in a binary image) backscattered electron images (BEI) were used. WTD was scored as a percentage of the needle surface area from BEI images of 1300×magnification. The method was compared to an ocular epicuticular wax classification method, where the wax structure is scored in terms of distribution classes (I–V). The average wax tube distribution of developing current-year needles was 21–29% higher when the ocular method was used than that obtained with the image analysis method. For example, the mean WTD in needles collected on 30 June (0.5-month-old needles) was 90% (ambient and supplemental UV-B) by the ocular method, whereas image analysis yielded values around 64% (ambient and supplemental UV-B). On previous year needles, the difference in the WTD values between these two methods was 5–9%. No statistically significant differences in WTD emerged between the trees exposed to ambient and supplemental UV-B. The image analysis method is more precise and more objective than the ocular methods commonly employed. The image analysis method can be used to investigate the wax structure of other conifer species and the response of epicuticular waxes to different environmental factors.

Functional ecology of advance regeneration in relation to light in boreal forests

This paper reviews aspects of the functional ecology of naturally established tree seedlings in the boreal forests of North America with an emphasis on the relationship between light availability and the growth and survival of shade tolerant conifers up to pole size. Shade tolerant conifer species such as firs and spruces tend to have a lower specific leaf mass, photosynthetic rate at saturation, live crown ratio, STAR (shoot silhouette area to total needle surface area ratio), and root to shoot ratio than the shade intolerant pines. The inability of intolerant species such as the pines and aspen to survive in shade appears to be mainly the result of characteristics at the shoot, crown, and whole-tree levels and not at the leaf level. Although firs and spruces frequently coexist in shaded understories, they do not have identical growth patterns and crown architectures. We propose a simple framework based on the maximum height that different tree species can sustain in shade, which may help managers determine the timing of partial or complete harvests. Consideration of these functional aspects of regeneration is important to the understanding of boreal forest dynamics and can be useful to forest managers seeking to develop or assess novel silvicultural systems.

UV Screening in Lodgepole Pine (Pinus contortassp.latifolia) Cotyledons and Needles

Conifer needles of high‐elevation species have been reported to screen UV radiation effectively from penetrating the leaf interior. Experiments were designed to investigate the epidermal transmittance (ET) of lodgepole pine (Pinus contorta ssp. latifolia) to ambient UV‐A and UV‐B radiation in the Rocky Mountains of southeastern Wyoming. Two exclusion treatments used plastic filters to regulate the amount of incident UV radiation in natural sunlight. One experiment utilized potted seedlings grown in the field at 2488‐m elevation, while the other used natural field saplings >0.5 m in height at another field site (3567‐m elevation). Both experiments consisted of a control and three exclosures covered with different plastic filters: (1) polyethylene plastic (control) that transmitted a high percentage of UV‐A and UV‐B, (2) clear polyester that excluded UV‐B wavelengths only, (3) Plexiglas that excluded most of the UV‐A and UV‐B wavelengths, and (4) a control treatment with no filtering (natural sunlight). The polyethylene plastic transmitted ca. 83% of total ambient levels of UV‐A and UV‐B, the polyester ca. 50% of total UV, but <2% of the UV‐B, while the Plexiglas filters transmitted 0% of total UV. The ET of UV radiation through leaf epidermal peels was measured with a fiber‐optic microprobe. In all treatments, ET was lowest for UV‐B wavelengths (300–320 nm) and increased exponentially as wavelength increased into the UV‐A region (320–360 nm). Results showed that (1) the epidermis of mature primary needles transmitted <2.5% of the incident UV radiation; (2) cotyledons of seed‐grown seedlings placed in the field had substantially less UV screening than primary leaves, especially for UV‐A; (3) needles of both cotyledons and primary needles grown without UV exposure (Plexiglas screening) had substantial declines in both UV‐A and UV‐B transmittance; and (4) needle length, surface area, biomass, or other growth variables were not influenced by any of the exclosure treatments. Also, ET was greatest (30% at 360 nm) for cotyledons grown without exposure to UV (Plexiglas), compared with ca. 14% when UV‐B was excluded and a 12% ET when all wavelengths were allowed to pass (polyethylene). These results indicate that the normal development of UV screening in lodgepole pine needles is dependent on exposure to UV during early ontogeny, especially UV‐B wavelengths.

Leaf area index of boreal forests: Theory, techniques, and measurements

Leaf area index (LAI) is a key structural characteristic of forest ecosystems because of the role of green leaves in controlling many biological and physical processes in plant canopies. Accurate LAI estimates are required in studies of ecophysiology, atmosphere‐ecosystem interactions, and global change. The objective of this paper is to evaluate LAI values obtained by several research teams using different methods for a broad spectrum of boreal forest types in support of the international Boreal Ecosystem‐Atmosphere Study (BOREAS). These methods include destructive sampling and optical instruments: the tracing radiation and architecture of canopies (TRAC), the LAI‐2000 plant canopy analyzer, hemispherical photography, and the Sunfleck Ceptometer. The latter three calculate LAI from measured radiation transmittance (gap fraction) using inversion models that assume a random spatial distribution of leaves. It is shown that these instruments underestimate LAI of boreal forest stands where the foliage is clumped. The TRAC quantifies the clumping effect by measuring the canopy gap size distribution. For deciduous stands the clumping index measured from TRAC includes the clumping effect at all scales, but for conifer stands it only resolves the clumping effect at scales larger than the shoot (the basic collection of needles). To determine foliage clumping within conifer shoots, a video camera and rotational light table system was used. The major difficulties in determining the surface area of small conifer needles have been largely overcome by the use of an accurate volume displacement method. Hemispherical photography has the advantage that it also provides a permanent image record of the canopies. Typically, LAI falls in the range from 1 to 4 for jack pine and aspen forests and from 1 to 6 for black spruce. Our comparative studies provide the most comprehensive set of LAI estimates available for boreal forests and demonstrate that optical techniques, combined with limited direct foliage sampling, can be used to obtain quick and accurate LAI measurements.

Evolution of soil acidity during the past 36 years (1960-1996) under coniferous forest in a region of high livestock production in Flanders

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Hydraulic Architecture and Structure of Abies lasiocarpa Seedlings in Three Subalpine Meadows of Different Moisture Status in the Eastern Olympic Mountains, Washington, U.S.A.

Hydraulic function and structural characterististics were measured during summer drought in 30 subalpine fir seedlings growing in three meadows of different moisture status close to the tree line in the eastern Olympic Mountains, Washington, U.S.A. No significant between-site differences were detected in the specific stem conductivities (hydraulic conductivity per transverse sapwood area) of the seedlings. The portion of needle mass to total aboveground mass decreased with decreasing moisture status. Leaf-specific conductivities (LSCs-hydraulic conductivity per dry weight of supplied needles) and Huber values (transverse sapwood area per dry weight of supplied needles) increased with decreasing site moisture status. These patterns indicate that the needle surface area supplied by a unit of stem transverse sectional sapwood area declined with site moisture status. Because the stem hydraulic conductivity was unaffected by site moisture status, it was inferred that embolism had probably not occurred in the drier site. We suggest that the absence of subalpine fir on very dry sites may be mainly due to an inadequate carbon balance; less foliage area would support a relatively large stem cross-sectional area.

Simulations of the effects of shoot structure and orientation on vertical gradients in intercepted light by conifer canopies.

Coniferous tree canopies typically carry more leaf area than is necessary to intercept most of the incoming light. I postulated that an excessively large leaf area will reduce net productivity at tree level, unless the net photosynthetic production of the most shaded shoots in the canopy remains positive. The hypothesis tested was that a coniferous tree canopy maintains a large productive leaf area by increasing the efficiency of light capture as the available light decreases. The light interception efficiency of a shoot was quantified by the ratio of shoot silhouette area to total needle surface area (STAR). The STAR depends on shoot geometry and varies with shoot orientation relative to the direction of light. Shade shoots have a larger STAR and, in particular, higher values of STAR(max) than sun shoots. In addition, shade shoots tend to be horizontally inclined, which may increase the advantage of a large STAR(max) in the lower canopy, where radiation is incident from angles closer to the zenith. Adaptation to shade (changes in STAR and shoot orientation) was described on the basis of empirical data for several coniferous species, and the vertical gradient of seasonal light interception by shoots was simulated assuming different adaptive strategies. Simulations were performed at two latitudes, to account for differences in the amount and directional distribution of light during the growing season. Results support the hypothesis that increases in STAR, shoot zenith angle and shoot asymmetry (flatness) with shading increase the efficiency of light interception by deeply shaded shoots. However, because competition for light among shoots increases progressively as soon as shade acclimation occurs, there cannot exist a deep layer of shade shoots, such that the net productivity of each shoot remains positive (i.e., irradiance is above the compensation point). Therefore, if maximization of productive leaf area is the goal, the optimal strategy is to maintain an inefficient deep canopy and to increase light interception efficiency only when shading becomes severe.

Acid-rain-induced changes in cuticles and Ca distribution in Scots pine and Norway spruce seedlings

Seedlings of Scots pine (Pinussylvestris L.) and Norway spruce (Piceaabies (L.) Karst.) were subjected to acid rain irrigation at pH 7, pH 4, and pH 3 three times a week during the growing seasons of 1986–1989 in a field experiment. Scanning and transmission electron microscopy, energy dispersive spectrometry, contact angle measurements, and chloroform extraction of waxes were used to detect physicochemical changes in the needle cuticles. The first detectable symptoms of acid rain were observed after 5 weeks of acid rain treatment at pH 3 and pH 4, which resulted in few CaSO4 crystallites on visibly undamaged pine and spruce needle surfaces. After 7 weeks of acid rain treatment there were CaSO4 crystallites scattered over the whole needle surface area and erosion of the epicuticular waxes could be observed occasionally. CaSO4 crystal formation later decreased, especially on the needles of seedlings treated at pH 3. Ca concentrations in the needles and roots of the seedlings and in the soil in the boxes were higher in the pH 3 treatments than elsewhere. The more abundant deposition of Ca oxalate crystallites on the inner walls of the epidermal and hypodermal cells of the spruce needles than on their outer walls was probably also connected with Ca leaching, caused by acid rain. Acid rain also delayed wax synthesis, as 2-month-old pine needles exposed to pH 3 and pH 4 had about 50% less wax than the water controls in early August. The needle surfaces of the southern provenances of spruce and pine seedlings were slightly less wettable after pH 4 treatment than after the control water treatment, because they probably benefited from N and S compounds in the irrigation water. The needle surfaces were more wettable in the pH 3 and water control seedlings than in the other treatments.

Effects of light availability and tree size on the architecture of assimilative surface in the canopy of Picea abies: variation in needle morphology.

Needle dimensions, needle surface area, needle dry weight per area (LWA) and needle density (ND, needle weight per volume) were measured in terminal current-year shoots in a natural canopy of variably sized Picea abies (L.) Karst. trees growing along a light gradient. Needle shape was described as a rhomboid. Needle width (D(2)) increased with increasing diffuse site factor, a(d) (relative amount of penetrating diffuse solar radiation), whereas needle thickness (D(1)) remained nearly constant, resulting in an inverse relationship between D(1)/D(2) and a(d) and an increase in the ratio of total (TLA) to projected needle surface area (PLA) with increasing a(d). Because of the variations in needle morphology with respect to light availability, the shoot parameters used in present canopy models are also expected to be light-sensitive, and studies involving shoot morphology should also consider the variability in needle geometry. Needle dimensions and total tree height were not correlated. However, LWA increase with both increasing a(d) and total tree height. When LWA was expressed as the product of ND and needle height (NH, height of the rhomboidal transverse section of a needle), LWA appeared to increase with irradiance, because of changing NH, and with total tree height, because of changing needle density.

Stand Characteristics of Ozone-Stressed Populations of Pinus jeffreyi (Pinaceae): Extent, Development, and Physiological Consequences of Visible Injury

The development and physiological consequences of ozone-induced visible injury was investigated in native populations of Jeffrey pine (Pinus jeffreyi) that were exposed to chronic levels of anthropogenic ozone. Stand structure analyses demonstrated that the expression of visible ozone injury symptoms within self-regenerating populations of Jeffrey pine was highly variable. Of the 975 trees surveyed, 90% exhibited some degree of visible injury and 10% were classified as resistant to ozone. Needles of the most sensitive trees developed a chlorotic mottle characteristic of ozone injury 1 year after their initiation and prematurely abscised in their third year (normal needle retention is 5–6 years). Average needle retention was not different between diameter size categories but was the most variable within the smallest size category and the least variable in the largest size category. Gas exchange measurements indicated a negative correlation between photosynthetic rate and needle surface area covered by chlorotic mottle. Chlorophyll fluorescence kinetics of the current-year needles did not differ between symptomatic and asymptomatic trees but did differ between the oldest needles, suggesting an uncontrolled physiological decline in needles about to abscise in sensitive trees. The high degree of variability of ozone-induced visible injury coupled with the reduction of physiological capacity associated with visible injury suggest that mixed conifer forests growing in polluted regions could potentially undergo shifts in community structure if sensitive Jeffrey pine individuals were to experience differential mortality as a result of ozone exposure. Intraspecific variation in ozone sensitivity may potentially lead to increased population tolerance to oxidative air pollutants, but long-term population analyses will be required to address genetic changes in response to ozone stress.

Stand characteristics of ozone‐stressed populations ofPinus jeffreyi (Pinaceae): extent, development, and physiological consequences of visible injury

The development and physiological consequences of ozone‐induced visible injury was investigated in native populations of Jeffrey pine (Pinus jeffreyi) that were exposed to chronic levels of anthropogenic ozone. Stand structure analyses demonstrated that the expression of visible ozone injury symptoms within self‐regenerating populations of Jeffrey pine was highly variable. Of the 975 trees surveyed, 90% exhibited some degree of visible injury and 10% were classified as resistant to ozone. Needles of the most sensitive trees developed a chlorotic mottle characteristic of ozone injury 1 year after their initiation and prematurely abscised in their third year (normal needle retention is 5–6 years). Average needle retention was not different between diameter size categories but was the most variable within the smallest size category and the least variable in the largest size category. Gas exchange measurements indicated a negative correlation between photosynthetic rate and needle surface area covered by chlorotic mottle. Chlorophyll fluorescence kinetics of the current‐year needles did not differ between symptomatic and asymptomatic trees but did differ between the oldest needles, suggesting an uncontrolled physiological decline in needles about to abscise in sensitive trees. The high degree of variability of ozone‐induced visible injury coupled with the reduction of physiological capacity associated with visible injury suggest that mixed conifer forests growing in polluted regions could potentially undergo shifts in community structure if sensitive Jeffrey pine individuals were to experience differential mortality as a result of ozone exposure. Intraspecific variation in ozone sensitivity may potentially lead to increased population tolerance to oxidative air pollutants, but long‐term population analyses will be required to address genetic changes in response to ozone stress.

The growth and gas exchange response of soil-planted Norway spruce [Picea abies (L.) Karst.] and red oak (Quercus rubra L.) exposed to elevated CO2 and to naturally occurring drought.

Norway spruce and red oak trees were planted directly into the soil and exposed to 700 μmol mol-1 CO2 in open-top chambers. There were large inter-specific differences in response to naturally occurring drought during the second year of exposure to elevated CO2 . Both species had decreased assimilation rates. CO2 -treated red oak had no loss of photosynthetic enhancement when undroughted, whereas CO2 -treated Norway spruce showed a relative increase in assimilation rates only when draughted. The effect of CO2 on radial growth of both species was less marked in the second growing season, but this may have been a result of different biomass partitioning as Norway spruce shoot extension had a different pattern of growth in elevated CO2 . Stomatal density and chlorophyll content were largely unaffected by the CO2 treatment. A precise method for measuring Norway spruce needle surface area was also developed.

Predicting potential transpiration of singleleaf pinyon: an adaptation of the potometer method

Estimates of singleleaf pinyon ( Pinus monophylla Tort. and Frem.) potential water use were conducted on the Virginia Range, Nevada, based on crown dimensions and needle biomass. A modified potometer method was developed to measure whole-tree transpiration over an 8 h period. Water uptake from the potometer was positively related to both the foliar mass plus the average number of resin canals in the needles of each tree. Water uptake was also positively related to the total crown needle surface area (cm 2) plus the average resin canal number. Best predictive equations based on standard error of the estimate analyses were obtained with nonlinear regression analysis of untransformed data. Pinyon populations with higher resin canal numbers are generally found in locations with higher temperatures and drier summer conditions.

Three dimensional distribution of needle and stem surface area in a Douglas-fir.

The distribution of needles and branches in the crown of a 14-m tall Douglas-fir was investigated for the purpose of developing a three-dimensional structure for use with radiation transfer models. We found a linear relationship between the basal area of main branches originating at the bole and the total one-sided planimetric surface area of the foliage attached to each branch. A similar linear relationship was found between the branch basal area and the mass of stem material on the branch. Total silhouette area (needles plus branch material) did not vary significantly horizontally along the branch length, but stem surface area declined linearly from near the bole to the branch tip. Needle surface silhouette area and leaf area index increased along the main branch from near the bole to the branch tip. Silhouette leaf area (STAR) did not vary along the main branch. The needle area density (NAD) (m(2) m(-3)) was calculated for each of the lower 11 whorls; the vertical distribution of NAD increased from the base of the bole to the top of the crown.