Trees Of Different Sizes Research Articles

Frugivory in European Laurel: how extinct seed dispersers have been substituted

Capsule Extinction of ancient frugivores during the Quaternary has led to a depauperated seed disperser community for Laurus nobilis and a tight mutualism between the plant and the Blackbird Turdus merula. Aims To describe a present-day frugivore assemblage of natural Laurel populations in southern Spain. Methods Eight fruiting trees of different size were monitored with binoculars during 52 hours spread across one ripening season, and the identity and behaviour of foraging birds were recorded. Additional point counts were used to record the avifauna of the surroundings. Results Despite a diverse frugivore community being present, Laurel fruits are almost exclusively (99%) consumed by Blackbird and rarely (1%) by Blackcap Sylvia atricapilla. Blackbirds concentrate at fruiting trees and individuals may remain there for several days. Birds usually forage in small groups and return at intervals of 12–14 minutes. Conclusion The Blackbird population of the study area forages extensively on the energy-rich Laurel fruits, while the plants depend exclusively on this bird species for seed dispersal. Consequences of the depauperate frugivore community and the tight mutualism between Blackbirds and Laurels on plant recruitment and conservation are discussed.

A computer model of neural processes observed in the cat motor cortex during performance of an operant movement.

This report describes a computer model of a "column" in the cat motor cortex. The model includes two layers of two-segment pyramidal neurons with two groups of inhibitory interneurons in each layer, which selectively control the somatic and dendritic segments of the pyramidal cells. In this model, neurons include active sodium, calcium, and several types of potassium currents. Excitatory connections between neurons are of the AMPA and NMDA types, while collateral connections between neurons of the upper layer are mainly of the NMDA type; connections between neurons in the lower layer are of the AMPA type. All inhibitory connections are of the GABA(A) type. The model reproduces the main neuronal processes seen in the cat motor cortex during performance of an operant movement. Pyramidal neurons of the upper layer generate primary and secondary responses to external stimuli. As in real experiments, secondary NMDA-dependent responses appear when GABA(A) inhibition is weakened and disappear when stimulation is increased; these properties of secondary responses are only reproduced when NMDA receptors are located in the terminals of collateral connections. Using only rapid NMDA-independent connections, neurons in the lower layer generate a slow bell-shaped wave of excitation (a "motor command"), which is formed by sequential activation of neurons with dendritic trees of different sizes.

PRODUCTIVITY AND ABUNDANCE OF SCLEROCARYA BIRREA SUBSP. CAFFRA IN AND AROUND RURAL SETTLEMENTS AND PROTECTED AREAS OF THE BUSHBUCKRIDGE LOWVELD, SOUTH AFRICA

ABSTRACT Sclerocarya birrea (A. Rich.) Hochst, subsp. caffra (Sond.) Kokwaro is a common species throughout the semi-arid savannas of southern Africa, and is sought after by rural communities. It is frequently maintained in homesteads and fields in an agroforestry situation. It has also been identified by a number of international and national institutes as a key species for domestication and commercialisation. Yet, the sustainability of the resource and local user knowledge and practices have not been considered. This study reports on the abundance and productivity of S. birrea in four rural villages and neighbouring protected areas in the Bushbuckridge lowveld of the Limpopo Province, South Africa, where its common name is marula. The density of marula stems was measured in homestead plots, arable fields and the surrounding communal rangelands of each village. Fruit production was assessed by regular counting of fruit fall from marked trees of known size. Within the villages, fruit production was monitored via local community groups. Additional monitoring of fruiting was conducted on marked trees within local protected areas. The proportion of households planting or nurturing marula trees was determined through interviews with a stratified random sample of households. The density of marula trees was significantly higher in protected areas than the neighbouring communal lands, fields or homesteads. However, the majority of trees in protected areas were small, while those in homesteads were large and mature. Density of adult fruit-bearing female trees, was similar between the protected areas and homesteads, but less in fields and communal lands. S. birrea trees were maintained in 79 % of homesteads and 58 % of fields. Mean fruit yield per tree was significantly higher from village trees (> 17 000 fruits) than protected area trees (< 3 500 fruits), even after accounting for differences in tree size. The fresh mass of individual fruits was also greater on village trees than on trees in protected areas. Both these characteristics suggest some degree of historical selection of the trees in the homesteads and fields. There was a positive relationship between tree size and number of fruits produced.

Fire season affects size and architecture of Colophospermum mopane in southern African savannas

Wildfires may be started naturally by lightning or artificially by humans. In the savanna regions of southern Africa, lightning fires tend to occur at the start of the wet season, during October and November, while anthropogenic fires are usually started during the dry season, between July and August. A long-term field manipulation experiment initiated in the Kruger National Park in 1952 was used to explore whether this seasonal divergence affects tree abundance, spatial pattern, size and architecture. After 44 years of prescribed burning treatments that simulated the seasonal incidence of lightning and anthropogenic fires, mean densities of the locally-dominant shrub, Colophospermum mopane, were 638 and 500 trees ha−1 respectively. Trees in burnt plots had aggregated distributions while trees in unburnt plots had random distributions. Significant differences (p < 0.001) were recorded in a range of morphological parameters including tree height, canopy diameter, mean stem circumference and number of stems. The incidence of resprouting also differed significantly between treatments, with burnt trees containing a high proportion of coppiced stems. The differences in tree size and architecture between the mid-dry season and early-wet season burning plots suggest that anthropogenic fires applied during July and August cannot substitute for a natural lightning fire regime. Anthropogenic fire yields a landscape that is shorter, more scrubby and populated by numerous coppiced shrubs than the landscape generated by natural lightning fire conditions.

Ponderosa pine mortality following fire in northern Arizona

Sampling of 1367 trees was conducted in the Side wildfire (4 May 1996), Bridger-Knoll wildfire (20 June 1996) and Dauber prescribed fire (9 September 1995) in northern Arizona ponderosa pine forests (Pinus ponderosa). Tree mortality was assessed for 3 years after each fire. Three-year post-fire mortality was 32.4% in the Side wildfire, 18.0% in the Dauber prescribed fire, and 13.9% in the Bridger-Knoll wildfire. In the Dauber and Side fires, 95% and 94% of 3-year post-fire mortality occurred by year 2, versus 76% in the Bridger-Knoll wildfire. Compared with trees that lived for 3 years after fire, dead trees in all fires had more crown scorch, crown consumption, bole scorch, ground char, and bark beetle attacks. Logistic regression models were used to provide insight on factors associated with tree mortality after fire. A model using total crown damage by fire (scorch + consumption) and bole char severity as independent variables was the best two-variable model for predicting individual tree mortality for all fires. The amount of total crown damage associated with the onset of tree mortality decreased as bole char severity increased. Models using diameter at breast height (dbh) and crown volume damage suggested that tree mortality decreased as dbh increased in the Dauber prescribed fire where trees were smallest, and tree mortality increased as dbh increased in the Side and Bridger-Knoll wildfires where trees were largest. Moreover, a U-shaped dbh–mortality distribution for all fires suggested higher mortality for the smallest and largest trees compared with intermediate-size trees. We concluded that tree mortality is strongly influenced by interaction between crown damage and bole char severity, and differences in resistance to fire among different-sized trees can vary among sites.

Corrigendum to: Ponderosa pine mortality following fire in northern Arizona

Sampling of 1367 trees was conducted in the Side wildfire (4 May 1996), Bridger-Knoll wildfire (20 June 1996) and Dauber prescribed fire (9 September 1995) in northern Arizona ponderosa pine forests (Pinus ponderosa). Tree mortality was assessed for 3 years after each fire. Three-year post-fire mortality was 32.4% in the Side wildfire, 18.0% in the Dauber prescribed fire, and 13.9% in the Bridger-Knoll wildfire. In the Dauber and Side fires, 95% and 94% of 3-year post-fire mortality occurred by year 2, versus 76% in the Bridger-Knoll wildfire. Compared with trees that lived for 3 years after fire, dead trees in all fires had more crown scorch, crown consumption, bole scorch, ground char, and bark beetle attacks. Logistic regression models were used to provide insight on factors associated with tree mortality after fire. A model using total crown damage by fire (scorch + consumption) and bole char severity as independent variables was the best two-variable model for predicting individual tree mortality for all fires. The amount of total crown damage associated with the onset of tree mortality decreased as bole char severity increased. Models using diameter at breast height (dbh) and crown volume damage suggested that tree mortality decreased as dbh increased in the Dauber prescribed fire where trees were smallest, and tree mortality increased as dbh increased in the Side and Bridger-Knoll wildfires where trees were largest. Moreover, a U-shaped dbh–mortality distribution for all fires suggested higher mortality for the smallest and largest trees compared with intermediate-size trees. We concluded that tree mortality is strongly influenced by interaction between crown damage and bole char severity, and differences in resistance to fire among different-sized trees can vary among sites.

Allometric modeling of plant root growth and its application in rhizosphere remediation of soil contaminants.

Allometric curves relating tree trunk diameter to root biomass, depth, and breadth were compiled for mulberry (Morus sp.). The curves were based on statistical analyses of measurements made on 29 different-sized trees ranging in age from 2 to 15 yr that had grown from seed in a naturally revegetated former sludge basin containing polyaromatic hydrocarbons. Over a 15-yr period, the curves indicate that the fine root biomass (<1.5 mm diameter) increases 60-fold and, under the right circumstances, can be a part of a root system that reaches a 2-m depth. The fine roots of mulberry were shown to produce several flavonoid compounds at concentrations (ranging from 94 to 525 microg/cm3) known to support the growth of organisms capable of degrading xenobiotics. Recognizing the root system as the driver of rhizoremediation, allometry curves presented in this paper can be used to quantify the magnitude of the driver (root system) without damaging plants during the course of a multiyear field study.

When branch autonomy fails: Milton's Law of resource availability and allocation.

The branch autonomy principle states that the critical characteristics of a branch's carbohydrate economy (photosynthesis, respiration, growth, etc.) are largely independent of the tree to which the branch is attached, as long as light is the primary factor limiting photosynthesis and growth. However, this may not be generally true because in the spring, photosynthates are translocated from a tree stem into branches, and the amount of photosynthate available for translocation should be a function of the tree's canopy status. And the correlative inhibition principle states that a branch's priority for allocation of carbon and other resources is controlled not only by its own environment, but also by its position relative to other branches on the same tree. A study of the lower limit of branch growth and survival in trees of different sizes shows that the latter principle is more important: even though dominant trees have more resources to allocate, branches on suppressed trees are able to grow and produce new foliage at solar irradiances where branches on dominant trees die. Thus branches are sufficiently interdependent that a positive carbon budget by itself does not ensure branch survival; branch position relative to other branches on the same tree is also important. Other findings indicate that this result is quite general: regardless of the stress involved, a stressed branch on a tree where all other branches are also stressed does better than a similarly stressed branch on a tree where some branches are relatively unstressed. Although branch autonomy is an important and useful principle, it is not an absolute rule governing branch growth.

Derivation of stem taper from the pipe theory in a carbon balance framework.

A dynamic tree growth model is described. The model derives the development of stem taper and vertical distribution of branch basal area from the pipe model, assuming that reuse of active pipes is regulated by foliage dynamics in a vertically explicit crown with a foliage distribution of constant shape. Based on empirical findings, the pipe model was modified slightly to allow the foliage/sapwood ratio to vary as a function of distance from the treetop. Growth was derived from carbon balance in a stand of different size trees that may shade each other. The model was applied to old and middle-aged trees growing in dense and sparse stands of Scots pine for which stand-level measurements are available as a chronosequence, but individual trees have been measured only once. Measured trees were compared with corresponding simulated trees for stem taper and vertical distribution of branch basal area. The results indicated that the pipe model assumptions, combined with a model of tree growth, are capable of producing realistic predictions of the vertical distribution of stem and branch diameter in trees of different sizes in the stand. A comparison of the results with a simple form of the uniform stress theory showed good agreement between the two models. However, a significant difference was found between the measured relative contribution of heartwood to total stem diameter and the predicted share of disused pipes in the stem. A possible explanation for this discrepancy is that the transition from sapwood to heartwood is gradual rather than abrupt as assumed in the model. A modification of the pipe model to incorporate a gradual transition is outlined.

Evaluating different soil and plant hydraulic constraints on tree function using a model and sap flow data from ponderosa pine

AbstractRelationships between tree size and physiological processes such as transpiration may have important implications for plant and ecosystem function, but as yet are poorly understood. We used a process‐based model of the soil–plant–atmosphere continuum to investigate patterns of whole‐tree sap flow in ponderosa pine trees of different size and age (36 m and ∼250 years versus 13 m and 10–50 years) over a developing summer drought. We examined three different hypothetical controls on hydraulic resistance, and found that size‐related differences in sap flow could be best explained by absolute differences in plant resistance related to path length (hypothesis 1) rather than through different dynamic relationships between plant resistance and leaf water potential (hypothesis 2), or alterations in rates of cumulative inducement and repair of cavitation (hypothesis 3). Reductions in sap flow over time could be best explained by rising soil–root resistance (hypothesis 1), rather than by a combination of rising plant and soil–root resistance (hypothesis 2), or by rising plant resistance alone (hypothesis 3). Comparing hourly predictions with observed sap flow, we found that a direct relationship between plant resistance and leaf water potential (hypothesis 2) led to unrealistic bimodal patterns of sap flow within a day. Explaining seasonal reduction in sap flow purely through rising plant resistance (hypothesis 3) was effective but failed to explain the observed decline in pre‐dawn leaf water potential for small trees. Thus, hypothesis 1 was best corroborated. A sensitivity analysis revealed a significant difference in the response to drought‐relieving rains; precipitation induced a strong recovery in sap flow in the hypothetical case of limiting soil–root resistance (hypothesis 1), and an insignificant response in the case of limiting plant resistance (hypothesis 3). Longer term monitoring and manipulation experiments are thus likely to resolve the uncertainties in hydraulic constraints on plant function.

Water use by whitebark pine and subalpine fir: potential consequences of fire exclusion in the northern Rocky Mountains.

In subalpine forests of the northern Rocky Mountains, fire exclusion has contributed to large-scale shifts from early-successional whitebark pine (Pinus albicaulis Engelm.) to late-successional subalpine fir (Abies lasiocarpa (Hook.) Nutt.), a species assumed to be more shade tolerant than whitebark pine and with leaf to sapwood area ratios (A(L):A(S)) over twice as high. Potential consequences of high A(L):A(S) for subalpine fir include reduced light availability and, if hydraulic sufficiency is maintained, increased whole-tree water use. We measured instantaneous gas exchange, carbon isotope ratios and sap flow of whitebark pine and subalpine fir trees of different sizes in the Sapphire Mountains of western Montana to determine: (1) whether species-specific differences in gas exchange are related to their assumed relative shade tolerance and (2) how differences in A(L):A(S) affect leaf- and whole-tree water use. Whitebark pine exhibited higher photosynthetic rates (A = 10.9 micromol x m(-2) x s(-1) +/- 1.1 SE), transpiration rates (E = 3.8 mmol x m(-2) x s(-1) +/- 0.7 SE), stomatal conductance (g(s) = 166.4 mmol x m(-2) x s(-1) +/- 5.3 SE) and carbon isotope ratios (delta13C = -25.5 per thousand +/- 0.2 SE) than subalpine fir (A = 5.7 micromol x m(-2) x s(-1) +/- 0.9 SE; E = 1.4 mmol x m(-2) x s(-1) +/- 0.3 SE; g(s) = 63.4 mmol x m(-2) x s(-1) +/- 1.2 SE, delta13C = -26.2 per thousand +/- 0.2 SE; P < 0.01 in all cases). Because subalpine fir had lower leaf-area-based sap flow than whitebark pine (QL = 0.33 kgx m(-2) x day(-1) +/- 0.03 SE and 0.76 kg x m(-2) x day(-1) +/- 0.06 SE, respectively; P < 0.001), the higher A(L):A(S) in subalpine fir did not result in direct proportional increases in whole-tree water use, although large subalpine firs used more water than large whitebark pines. The linear relationships between tree size and daily water use (r2 = 0.94 and 0.97 for whitebark pine and subalpine fir, respectively) developed at the Sapphire Mountains site were applied to trees of known size classes measured in 12 natural subalpine stands in the Bob Marshall Wilderness Complex (western Montana) ranging from 67 to 458 years old. Results indicated that the potential for subalpine forests to lose water by transpiration increases as succession proceeds and subalpine fir recruits into whitebark pine stands.

How good is the fossil record of arthropods? An assessment using the stratigraphic congruence of cladograms

AbstractA total of 179 published cladograms of arthropods was tested for their congruence with the palaeontological record. Congruence for data sets including 510 tetrapod and 157 fish trees was also calculated for comparison. Results provide support for the hypothesis that the fossil record of arthropods is less complete (at levels of stratigraphic and taxonomic resolution pertinent to most macroevolutionary studies) than the records of several other taxa. Differences in tree size, shape, balance and the distribution of first stratigraphic appearances (potential sources of bias) were controlled for by various randomization procedures. Most measures of congruence for arthropods were statistically poorer than those for other groups, even when the sample was divided into broad temporal bins. Many of the most robust and widely reproduced sister groupings of arthropods are attended by ghost ranges of many tens or hundreds of millions of years. Fossils of a number of presently very diverse and abundant arthropod groups are conspicuously absent from the record, despite many spectacular examples of the detailed preservation of others. There is probably no single reason for the apparently poor record of arthropods. Low preservation potential, small size of individuals, small numbers of individuals, and restricted palaeobiogeography almost certainly play a role in particular cases. Copyright © 2001 John Wiley &amp; Sons, Ltd.

The relationships between tree size and spatial distribution of foliage-mass within crowns of Japanese cedars (Cryptomeria japonica) in young plantations

The spatial distribution of foliage-mass within the crowns of Japanese cedars ( Cryptomeria japonica D. Don) was measured for trees of different sizes. The horizontal changes of three indices (the crown depth of the foliage layer, Cd( r ) the relative depth of the maximum foliage along a vertical line, R ( r ) and the mean foliage-mass density from the crown surface to 1 m in depth, F ( r , 1)) were analyzed. The tree size related to the horizontal distribution of the foliage. The vertical size of the foliage space represented by Cd( r ), had a positive relation to the relative tree size in the stand, not to the absolute tree size. Hence, dominance is an important factor in vertical foliage distribution. In contrast, the absolute tree size was related to the pattern of the horizontal foliage distribution, which is represented by the horizontal change of F ( r , 1). Therefore, a spatial foliage distribution profile could be represented well using these indices. An empirical model was constructed for estimating the foliage mass density, using the relationships between the tree size and the three indices.

Effect of apple-orchard structure on interception of Rhagoletis pomonella (Diptera: Tephritidae) flies by odor-baited traps

AbstractWe released marked mature male flies of the apple maggot, Rhagoletis pomonella (Walsh), inside and outside of square blocks of apple trees, Malus domestica Borkh. (Rosaceae), to test the effect of orchard structure on the interception of flies by odor-baited red-sphere traps. The blocks were composed of large trees planted at low density, medium-sized trees planted at medium density, or small trees planted at high density. The experiment was carried out in six commercial apple orchards during summer in 1997 and 1998. Released flies moving into blocks were intercepted in large proportions by baited perimeter traps, thus preventing fly penetration into sphere-protected blocks. In 1997, proportions of intercepted flies were higher for traps in blocks of small and medium-sized trees than for traps in blocks of large trees. In 1998, a year with an unusually low fruit load, interception remained high, but there were no differences in proportions of flies intercepted by perimeter traps among blocks of trees of different sizes. Overall we conclude that the tendency of apple growers in Massachusetts to replace large trees planted at low density with small or medium-sized trees planted at high or medium density will not adversely affect behavioral control programs for apple maggot flies. In fact, this practice may enhance the effectiveness of these programs through increased interception of immigrant adults.

Species differences in transpiration on a saline discharge site

Growth, sap velocity, tree water use and transpiration rates per unit of leaf area were compared between Eucalyptus occidentalis Endl., Eucalyptus spathulata Hook., Eucalyptus leucoxylon F. Muell., and Eucalyptus cladocalyx F. Muell. on a moderately-saline discharge site near Wellington, NSW, Australia. These were four of the best performed species in a 7-year old trial of 36 species and provenances. Even though all trees were the same age and had grown under identical conditions, water use per tree was four–five times greater in E. spathulata than in the other three species. This difference was due to a large difference in tree size. E. spathulata had grown faster than the other species and had a mean tree leaf area four–five times greater than the other species. Species differences in water use per unit of leaf area were smaller, but sometimes statistically significant. During a period of cool dry weather in late winter, there were no significant differences between species in transpiration per unit of leaf area. In early summer, however, when the maximum vapour pressure deficit reached 6–7.5 kPa on some days, E. leucoxylon had a 22% lower rate of transpiration per unit of leaf area than the other three species. This difference was presumably due to a stronger stomatal response to high vapour pressure deficit in E. leucoxylon than the other species. During a period of warm humid weather in late summer, transpiration per unit of leaf area was 75% higher in E. cladocalyx compared with the other three species. The reason for this difference is not known, but it may indicate a species difference in root architecture, and hence a difference in access to ground water or soil water.

Scenario analysis of demand in a technology market using leading indicators

This paper proposes an approach to analyzing demand scenarios in technology-driven markets where product demands are volatile, but follow a few identifiable lifecycle patterns. After examining a large amount of semiconductor data, we found that not only can products be clustered by lifecycle patterns, but in each cluster there exists a leading indicator product that provides advanced indication of changes in demand trends. Motivated by this finding, we propose a scenario analysis structure in the context of stochastic programming. Specifically, the demand model that results from this approach provides a mechanism for building a scenario tree for semiconductor demand. Using the Bass growth model and a Bayesian update structure, the approach streamlines scenario analysis by focusing on parametric changes of the demand growth model over time. The Bayesian structure allows expert judgment to be incorporated into scenario generation while the Bass growth model allows an efficient representation of time varying demands. Further, by adjusting a likelihood threshold, the method generates scenario trees of different sizes and accuracy. This structure provides a practical scenario analysis method for manufacturing demand in a technology market. We demonstrate the applicability of this method using real semiconductor data.

Spray deposits and losses in different sized apple trees from an axial fan orchard sprayer: 1. Effects of spray liquid flow rate

Spray deposit and off-target contamination distribution measurements were made in apple trees of different sizes and row spacings for an axial fan sprayer with different spray liquid flow rates ( c 3.8, 11, 29 l min −1) but otherwise constant conditions (air flow=11.3 m 3 s −1; speed=5.8–5.9 km h −1, VMD=156–159 μm). Leaf deposits (normalised by the applied dose) were not affected by the spray liquid flow rate except on young dwarf trees at the high flow rate due to saturation. The volume retained on the crop increased with tree size. Deposits on individual leaves were approximately log normally distributed. Variability was usually marginally greater for the low flow treatment than for the medium or high flow treatments and usually greater in the larger than in the smaller trees. Mean deposits on the undersides of leaves were about double those on upper surfaces. The mean percentage of the surface area of water sensitive papers in the centre of the tree covered with spray varied in direct proportion to the spray liquid flow rate. Spray cover was least in the larger trees. Deposits on fruitlets were affected significantly by spray liquid flow rate. The high flow rate treatment gave the smallest deposits on fruitlets due to the deposit exceeding local saturation conditions. The deposits on fruitlets tended to be greater in the smaller than in the larger trees. Normalised spray drift deposits on vertical, 10 m tall polythene sampling lines positioned 5 m downwind of the sprayer were somewhat greater for the low flow rate than the medium and high flow rate treatments but differences were at least partly due to differences in wind direction. High values occurred where the wind direction was perpendicular to the tree rows, low values where the wind direction was parallel to the tree rows. Drift generally decreased with increasing tree size. There were no consistent differences in normalised ground deposits due to spray liquid flow rate, though ground deposits were greater in the smaller trees than in the larger trees. As a whole, these results showed that wide variation in spray liquid flow rate had only small effects on normalised spray deposits on the tree, on spray drift and on losses to the ground but greatly affected spray cover which varied in proportion to the spray liquid flow rate. This implies that the spray liquid flow rate for foliar application of an agrochemical should be determined by the degree of spray cover that is needed for adequate efficacy. Furthermore, the pesticide dose rate may be conveniently adjusted in direct proportion to the spray liquid flow rate at constant concentration for deposits lower than the target saturation level.

Trigonometric Variable-Form Taper Equations for Australian Eucalypts

Abstract This article introduces a new variable-form taper model that is stable in specification yet flexible in its ability to fit data for species and trees with different stem forms. The base function is constructed from trigonometric volume-ratio equations following the geometry of a tree stem. The specification for the exponent includes variables for depicting changes in stem form along a stem and variables for taking into account differences in stem form among trees of different sizes. This model is fitted to data from 25 species of Australian eucalypts and is compared with Kozak's taper model to demonstrate its characteristics: stability in specification, flexibility in fitting data for species and trees with varying stem forms and accurate predictions of taper and merchantable height. FOR. SCI. 46(3): 397–409.

Effects of tree size and temperature on relative growth rate and its components of Fagus sylvatica seedlings exposed to two partial pressures of atmospheric [CO2

Growth responses of two provenances of European beech (Fagus sylvatica) were studied. The seedlings were grown in closed‐top chambers at four temperature regimes (−2.9 °C below ambient, ambient, +2.3 °C and +4.8 °C above ambient) in combination with two CO2 partial pressures (40 Pa and 74 Pa). Growth was followed by making destructive harvests c. every 25 d from germination in early June to senescence in late September. Allocation patterns were significantly affected by the temperature regimes. However, changes in dry matter allocation and morphology associated with the different treatments at a given time were mostly a result of differences in tree size. Temperature regimes only had a significant effect on the relative growth rate, RGR, at the beginning of the experiment. In contrast to temperature, high [CO2] increased RGR throughout the experiment when compared with plants of equal size. As the trees increased in size net assimilation rate, NAR, decreased but the effect of [CO2] on both NAR and RGR had a tendency to increase. Increases in NAR caused by elevated [CO2] were partly counteracted by reductions in the leaf area ratio, LAR. Reductions in LAR were caused by concomitant reductions in specific leaf area, SLA, whereas the level of [CO2] did not significantly affect leaf weight ratio, LWR, nor other dry weight ratios. The interactions between temperature and [CO2] are highly dependent on whether they are expressed as instantaneous values for plants at a common age or instantaneous values at a common size (and thereby extracting the effects of ontogenetic drift). When comparing instantaneous values at common sizes, the positive effect of [CO2] on RGR increased with plant size in every temperature regime. This also occurred in every temperature regime when comparing plants of equal age but the response to [CO2] was less. The effect of [CO2] on RGR was dependent on growth temperature. The positive effects of elevated [CO2] on RGR were less than the positive effect on photosynthesis. The two provenances did not differ significantly in the response of RGR to [CO2] which is in agreement with measurements of photosynthesis.

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