Aboveground Biomass Allocation Research Articles

Dwarf mistletoe affects whole-tree water relations of Douglas fir and western larch primarily through changes in leaf to sapwood ratios.

Dwarf mistletoes induce abnormal growth patterns and extreme changes in the biomass allocation of their hosts as well as directly parasitizing them for resources. Because biomass allocation can affect the resource use and efficiency of conifers, we studied the influences of dwarf mistletoe infection on above-ground biomass allocation of Douglas fir and western larch, and the consequences of such changes on whole-tree water use and water relations. Sap flow, tree water potentials, leaf:sapwood area ratios (A L:A S), leaf carbon isotope ratios, and nitrogen content were measured on Douglas fir and western larch trees with various degrees of mistletoe infection during the summer of 1996 in western Montana. Heavy dwarf mistletoe infection on Douglas fir and western larch was related to significant increases in A L:A S. Correspondingly, water transport dynamics were altered in infected trees, but responses were different for the two species. Higher A L:A S ratios in heavily infected Douglas firs were offset by increases in sapwood area-based sap flux densities (Q SW) such that leaf area-based sap flux densities (Q L) and predawn leaf water potentials at the end of the summer did not change significantly with mistletoe infection. Small (but statistically insignificant) decreases of Q L for heavily infected Douglas firs were enough to offset increases in leaf area such that whole-tree water use was similar for uninfected and heavily infected trees. Increased A L:A S ratios of heavily infected western larch were not offset by increases of Q SW. Consequently, Q L was reduced, which corresponded with significant decreases of water potential at the end of the summer. Furthermore, mistletoe-infection-related changes in A L:A S as a function of tree size resulted in greater whole-tree water use for large infected larches than for large uninfected trees. Such changes may result in further depletion of limited soil water resources in mature infected stands late in the growing season. Foliage from infected trees of both species had lower water use efficiencies than non-infected trees. Our results demonstrate substantial changes of whole-tree processes related to mistletoe infection, and stress the importance of integrating whole-tree physiological and structural processes to fully understand the mechanisms by which pathogens suppress forest productivity.

Effects of ontogeny and soil nutrient supply on production, allocation, and leaf area efficiency in loblolly and slash pine stands

The effects of ontogeny and soil nutrient supply on aboveground biomass accumulation, allocation, and stemwood growth efficiency of loblolly (Pinus taeda L.) and slash pine (Pinus elliottii Engelm. var. elliottii) were investigated in north-central Florida over 16 years using a 2 × 2 × 2 factorial experiment (species, fertilization, weed control). Aboveground biomass growth responses to the combined fertilizer and weed control treatments (FW) averaged ~2- and 2.8-fold for slash and loblolly pine, respectively. In the same treatment, annual needlefall (NF) production for slash pine approached a "steady state" of 6 Mg·ha-1 at ages 8-14 years, while loblolly pine NF production peaked at 7 Mg·ha-1 at age 10 years, and then declined 17% following curtailment of the fertilizer treatment. Periodic stemwood biomass increment (PAI) for the FW treatment for both species culminated at about 15 Mg·ha-1·year-1 at age 8 years and then declined rapidly (~275%) to <4 Mg·ha-1·year-1 at 15 years; reductions for the untreated control were considerably slower. The progressive decline in PAI following peak leaf area development was closely associated with a decrease in stemwood production per unit leaf area (growth efficiency). A unit increase in leaf area index in the 7- to 9-year-old stands produced about 3.0 and 3.1 times more stemwood biomass per year than in the 14- to 16-year-old stands for loblolly and slash pine, respectively.

Effects of light availability and sapling size on the growth, biomass allocation, and crown morphology of understory sugar maple, yellow birch, and beech

The patterns of above-ground growth, biomass allocation, crown morphology, and light attenuation were compared between small (50 to 250 cm tall) and tall (250 to 600 cm tall) yellow birch, sugar maple, and beech individuals in low (< 10% of above-canopy PPFD (Photosynthetic Photon Flux Density)) and high (10 to 40% PPFD) light environments in a mature sugar maple-birch-beech stand near Quebec city, Canada. Significant differences in above-ground growth, crown morphology, and allocation patterns were found among (i) the three co-dominating tree species, (ii) short and tall individuals, and (iii) low and high light environments. The direction of the differences in most traits investigated between low and high light environments were strikingly similar among the three species, but the magnitude of the differences often varied. Overall, yellow birch differed more in several traits in terms of its responses to light and size compared to beech and sugar maple. In general, differences found between light environments were smaller for the taller saplings, indicating that plasticity tends to decrease with increasing size in all three species. None of these crown structural differences found among species translated into differences in light attenuation within the sapling crowns. The maximum height observed in individual trees of all three species tended to decrease sharply below approximately 4% PPFD. We suggest that maximum tree height is restricted in such low light environments since the photosynthetic to non-photosynthetic tissue ratio, as measured by the leaf area ratio (LAR), declines rapidly with seedling size up to 150 cm. We suggest that these three species co-dominate in this forest due to a combination of small but effective differences in physiological, morphological, and allocational traits and responses to increases in the understory light environment.

Effects of ontogeny and soil nutrient supply on production, allocation, and leaf area efficiency in loblolly and slash pine stands

The effects of ontogeny and soil nutrient supply on aboveground biomass accumulation, allocation, and stemwood growth efficiency of loblolly (Pinus taeda L.) and slash pine (Pinus elliottii Engelm. var. elliottii) were investigated in north-central Florida over 16 years using a 2 × 2 × 2 factorial experiment (species, fertilization, weed control). Aboveground biomass growth responses to the combined fertilizer and weed control treatments (FW) averaged ~2- and 2.8-fold for slash and loblolly pine, respectively. In the same treatment, annual needlefall (NF) production for slash pine approached a steady state of 6 Mg·ha-1 at ages 8-14 years, while loblolly pine NF production peaked at 7 Mg·ha-1 at age 10 years, and then declined 17% following curtailment of the fertilizer treatment. Periodic stemwood biomass increment (PAI) for the FW treatment for both species culminated at about 15 Mg·ha-1·year-1 at age 8 years and then declined rapidly (~275%) to <4 Mg·ha-1·year-1 at 15 years; reductions for the untreat...

BIOMASS ALLOCATION AND PHOSPHORUS PRODUCTIVITY OF CAREX SPECIES IN RELATION TO SOIL PHOSPHORUS STATUS

Biomass allocation and P productivity were studied in threeCarexspecies (C. acutiformis, C. diandra, andC. lasiocarpa) that were grown in fen peat soils differing in P content. Biomass allocation to plant parts and P productivity involved significant interactions between soil P status and species.C. acutiformis, a species from highly productive areas, showed higher biomass production, P productivity, leaf area ratio, and specific leaf area under P-deficient conditions thanC. diandraandC. lasiocarpa, both species from less productive areas. Below-ground biomass allocation ofC. acutiformisand above-ground biomass allocation ofC. diandraand C.lasiocarpashowed plasticity in relation to soil P status.These results were remarkable since C.acutiformis, a species from eutrophic fen areas, was expected to perform worse under P-deficient conditions than those species naturally growing in those areas. Species demands on the chemical composition of the interstitial water, specific abilities to use nondirectly available P pools, faster seed germination, or seedling establishment may contribute to determine the field distribution of fenCarexspecies in relation to soil P status.

Aboveground biomass and nitrogen allocation of ten deciduous southern Appalachian tree species

Allometric equations were developed for mature trees of 10 deciduous species (Acer rubrum L., Betula lenta L., Carya spp., Cornus florida L., Liriodendron tulipifera L., Oxydendrum arboreum (L.) DC., Quercus alba L., Quercus coccinea Muenchh., Quercus prinus L., and Quercus rubra L.) at the Coweeta Hydrologic Laboratory in western North Carolina, U.S.A. These equations included the following dependent variables: stem wood mass, stem bark mass, branch mass, total wood mass, foliage mass, total biomass, foliage area, stem surface area, sapwood volume, and total tree volume. High correlation coefficients (R2) were observed for all variables versus stem diameter, with the highest being for total tree biomass, which ranged from 0.981 for Oxydendrum arboreum to 0.999 for Quercus coccinea. Foliage area had the lowest R2 values, ranging from 0.555 for Quercus alba to 0.962 for Betula lenta. When all species were combined, correlation coefficients ranged from 0.822 for foliage area to 0.986 for total wood mass, total tree biomass, and total tree volume. Species with ring versus diffuse/semiring porous wood anatomy exhibited higher leaf area with a given cross-sectional sapwood area as well as lower total sapwood volume. Liriodendron tulipifera contained one of the highest foliar nitrogen concentrations and had consistently low branch, bark, sapwood, and heartwood nitrogen contents. For a tree diameter of 50 cm, Carya spp. exhibited the highest total nitrogen content whereas Liriodendron tulipifera exhibited the lowest.

Biomass Allocation and Light Partitioning Among Dominant and Subordinate Individuals inXanthium canadenseStands

Patterns of above-ground biomass allocation and light capture by plants growing in dense stands or in isolation were studied in relation to their height. A canopy model was developed to calculate light absorption by individual plants. This model was combined with data on canopy structure and patterns of biomass allocation for solitary plants and for plants of different heights in dense mono-specific stands of the dicotyledonous annualXanthium canadenseMill. There were four stands, and stand height increased with age and nutrient availability. The allometric relationship between height and mass differed considerably between plants in stands and those growing in isolation and also between plants of different heights within stands. The proportion of shoot mass in leaf laminae (LMR) decreased with increasing plant height, but solitary plants had a higher LMR than competing plants of the same height. Thus, in contrast to previous assumptions, LMR of competing plants is not strictly determined by biomechanical constraints but results from a plastic shift in biomass allocation in response to competition. Average leaf area per unit leaf mass (SLA) decreased with increasing photosynthetic photon flux density (PPFD) independent of nutrient availability. Consequently, taller, more dominant plants in stands had a lower leaf area ratio (LAR: LAR=LMR×SLA) than shorter, more subordinate plants. Dominant plants absorbed more light both per unit leaf area (Φarea) and per unit mass (Φmass) than subordinate plants. Their greater Φareamore than compensated for a lower LAR (Φmass=Φarea×LAR). We conclude that the greater Φmassof dominant plants is quantitative evidence that success in competing for light is disproportionately related to the size of the shoot (i.e. asymmetric competition). We know of no other study which has demonstrated this with quantitative estimates of light acquisition in relation to plant size. This result is contrasted with previous studies on multi-specific stands in which Φmassof dominant and subordinate species is similar, and we discuss why light competition in mono-specific stands is asymmetric whereas it can be size-symmetric in multi-specific stands, with similar or greater LAI.

Biomass allocation and nodulation of Gliricidia sepium under two cut-and-carry forage production regimes

The effects of two pruning regimes on the above-ground biomass allocation and nodulation of Gliricidia sepium (Jacq.) Walp. (Leguminosae: Robinieae) were studied in a cut-and-carry forage production system under humid tropical conditions in Guadeloupe, French Antilles. The grass layer composed of a mixture dominated by Paspalum notatum Flugge (80%) and Digitaria decumbens Stent. The pruning regimes were partial pruning (ca. 50%) every two months and complete pruning every six months. The complete pruning caused an almost complete turnover of N2 fixing nodules. The nodule biomass decreased after the partial pruning, but the turnover was not complete. The nodule to foliage biomass ratio followed the same pattern under both treatments, and the values of the ratio converged towards the end of the experimental period. The maxima of standing nodule biomass were 7.2 and 13.0 kg ha−1 in the partially and completely pruned trees, respectively. The cumulative leaf fodder harvest was higher under partial pruning management, due to smaller litter loss. The branch biomass production was higher under complete pruning management. Grass production was not affected by the pruning pattern of G. sepium. It was concluded that the partial pruning management produces more fodder in the studied association, and the nodulation probably adjusts to the canopy N requirements. The potential N release to soil in the turnover of nodules of G. sepium (max. 0.82 kg ha−1) is negligible compared to the N export in tree and grass fodder harvest, 190 and 215 kg ha−1 in partially and completely pruned plots, respectively.

Aboveground biomass and nitrogen allocation of ten deciduous southern Appalachian tree species

Aboveground biomass and nitrogen allocation of ten deciduous southern Appalachian tree species

Hydraulic adjustment of maple saplings to canopy gap formation.

The leaf-specific hydraulic conductivity (K L) of plant stems can control leaf water supply. This property is influenced by variation in leaf/sapwood area ratio (A L/A S) and the specific hydraulic conductivity of xylem tissue (K S). In environments with high atmospheric vapor pressure deficit (VPD), K L may increase to support higher transpiration rates. We predicted that saplings of Acerrubrum and A.pensylvanicum grown in forest canopy gaps, under high light and VPD, would have higher K L and lower A L/A S than similar sized saplings in the understory. Leaf-specific hydraulic conductivity and K S increased with sapling size for both species. In A. rubrum, K S did not differ between the two environments but lower A L/A S (P=0.05, ANCOVA) led to higher K L for gap-grown saplings (P < 0.05, ANCOVA). In A. pensylvanicum, neither K S, A L/A S, nor KL differed between environments. In a second experiment, we examined the impact of sapling size on the water relations and carbon assimilation of A.pensylvanicum. Maximum stomatal conductance for A.pensylvanicum increased with K L (r 2=0.75, P < 0.05). A hypothetical large A. pensylvanicum sapling (2 m tall) had 2.4 times higher K L and 22 times greater daily carbon assimilation than a small (1 m tall) sapling. Size-related hydraulic limitations in A.pensylvanicum caused a 68% reduction in daily carbon assimilation in small saplings. Mid-day water potential increased with A.pensylvanicum sapling size (r 2=0.69, P < 0.05). Calculations indicated that small A.pensylvanicum saplings (low K L) could not transpire at the rate of large saplings (high K L) without reaching theoretical thresholds for xylem embolism induction. The coordination between K L and stomatal conductance in saplings may prevent xylem water potential from reaching levels that cause embolism but also limits transpiration. The K S of the xylem did not vary across environments, suggesting that altering biomass allocation is the primary mechanism of increasing K L. However, the ability to alter aboveground biomass allocation in response to canopy gaps is species-specific. As a result of the increase in K L and K S with sapling size for both species, hydraulic limitation of water flux may impose a greater restriction on daily carbon assimilation for small saplings in the gap environment.

Branch growth and biomass allocation in Abies amabilis saplings in contrasting light environments.

Aboveground biomass allocation, and height and branch growth were studied in saplings of the shade-tolerant conifer, Abies amabilis Dougl. ex Forbes growing in large openings and in the understory of an old-growth forest in western Oregon. The presence of annual overwintering budscale scars was used to infer extension growth histories; annual growth rings in branches and stems were used in combination with extension histories to compute partitioning of new biomass among leaves, branches and stems. Saplings growing in large gaps had conical crowns, whereas understory saplings had umbrella shaped crowns as a result of much greater rates of branch extension than stem extension. Understory saplings grew slowly in height because of low rates of biomass production and low allocation of biomass to stem extension. About 40% of new biomass was allocated to foliage in both groups, but understory saplings allocated more of the remaining growth increment to branches and less to stem than did saplings growing in large gaps. These results differ from the patterns observed in shade-tolerant saplings of tropical forests, where allocation to foliage increases with shading and branch allocation is much lower than observed here. This difference in allocation may reflect mechanical constraints imposed by snow loads on the evergreen A. amabilis crowns, particularly on flat-crowned understory saplings.

Understory competition effect on tree growth and biomass allocation on a coastal old-growth forest cutover site in British Columbia

We studied the effect of salal ( Gaultheria shallon Pursh.) competition on height, diameter and biomass growth and biomass partitioning in coniferous trees planted to a recent clearcut site of old growth western red cedar-western hemlock (CH) forest on northern Vancouver Island, British Columbia. Tree species used were western red cedar ( Thuja plicata Donn ex D. Don), western hemlock ( Tsuga heterophylla (Raf.) Sarg.), and Sitka spruce ( Picea sitchensis (Bong.) Carr). Salal removal treatment was initiated at the time of planting in spring 1987. Plots were fertilized with 200 kg N ha −1 in spring 1991 and destructively sampled in fall 1992. Height growth from planted to 1989, in 1992 and total height growth were significantly greater in treated plots (salal removed) than in the control plots (salal remaining). Salal removal had a rather uniform impact on height growth for the three species tested. Total root collar diameter was 38% ( P < 0.1), 88% ( P < 0.05), and 65% ( P < 0.05) greater in the treated plots than in the control plots, for red cedar, hemlock and spruce, respectively. Exclusion of understory vegetation had resulted in biomass increases of all the components (namely in the 1-year and 2-year foliage and branches and the older than 3-year components and various sized roots) we studied. Improved tree growth in the treated plots was attributed to the reduced uptake and immobilization of N and other nutrients by the competing understory. Below-ground understory was found to be quite persistent to surviving even after a prolonged period (6 years) of above-ground understory vegetation removal Biomass allocation among the components studied was virtually unchanged by the presence of the competing understory, except in two instances. This result was quite different from most of the other reports on biomass partitioning under competition. Our hypothesis that salal competition for nutrients increases biomass partitioning to current year foliage and branch and roots was rejected. Unchanged partitioning is prooably a way of response to nutrient deficiencies according to the resource depletion model of competition processes. Non-significantly higher biomass partitioning was observed in the 1-year foliar and branch and 0.25–1 cm root components. It was therefore possible that the 1991 fertilization alleviated the nutrient shortage problem which led to the rejection of the hypothesis.

Biomass Allocation of Montane and Desert Ponderosa Pine: An Analog for Response to Climate Change

We measured aboveground biomass allocation of Pinus ponderosa on hydrothermally altered andesite in montane and desert climates. Thus substrates was held constant while climate varied. Trees from montane climates had higher leaf mass per unit cross—sectional area of sapwood (functional conducting xylem) than trees from desert climates, suggesting that a functional response to differences in climate had occurred. Our results also indicate that sapwood mass; leaf mass ratios of P. ponderosa may increase 2°50% with a 5°C change in mean growing—season temperature, approximately the difference between our montane and desert sites. High proportional allocation of biomass to sapwood may improve water relations of P. ponderosa, but because sapwood contains living parenchyma, respiratory costs may be high. Site—specific regression equations were used to calculate aboveground biomass allocation for simulated montane and desert trees with the same diameter at breast height, dbh. Simulated montane trees were 46—52% taller than desert trees, and montane trees 10 cm in dbh had twice the total aboveground mass of desert counterparts. Simulated 50—cm montane and desert trees were almost identical in total mass, even though the montane tree was 46% taller. The predicted proportion of biomass allocated to bole sapwood increased with size for both montane and desert models; however, the 50—cm desert model contained 8% more total sapwood mass than the taller montane model. Total biomass of branches was similar for paired models of all size classes; however, biomass of primary and secondary branches differed considerably. The 50—cm desert model had twice as much biomass in primary branches in comparison to the montane model, whereas the montane model had 3 times more biomass in secondary branches than the desert model. For 10—cm trees of the desert and montane models 29 and 33% of the biomass were leaves, respectively. In larger trees, leaf allocation decreased to 5 and 7% for desert and montane models, respectively. The effects of climate on biomass allocation, such as reported here, and corresponding changes in whole—plant assimilation rates must be incorporated into growth—response models used to predict future fluctuations in forest productivity due to global climate change.

Offsetting changes in biomass allocation and photosynthesis in ponderosa pine (Pinus ponderosa) in response to climate change.

We examined the effect of climate on aboveground biomass allocation of ponderosa pine (Pinus ponderosa) by measuring trees in disjunct forest stands growing on the same substrate at high-elevation montane sites and low-elevation desert sites. Climatic differences between the sites were comparable to the difference between present and future climates of interior North America that is expected to result from a doubling of atmospheric CO(2) concentration. Relative to the montane populations, the desert populations allocated a greater proportion of biomass to sapwood (functional xylem) at the expense of foliage. The leaf/sapwood area ratio and percent of aboveground biomass in sapwood for trees of the same height were 0.201 m(2) cm(-2) and 58% for montane trees and 0.104 m(2) cm(-2) and 71% for desert trees. In a phytotron experiment, increases in net photosynthesis and net assimilation rate for seedlings grown under future conditions of high CO(2) and temperature were offset by a decrease in leaf area ratio. As was observed for large trees at different elevations, increased temperatures caused an increase in biomass allocation to stem in the phytotron seedlings. Thus, CO(2)- and temperature-driven shifts in biomass allocation negated the effect on growth of the CO(2)-driven increase in carbon assimilation rate. Our data from the controlled growth chamber and field experiments suggest that future climate conditions, including elevated atmospheric CO(2), may not stimulate growth and productivity of ponderosa pine.

Growth and nutrition of Schoenoplectus validus in agricultural wastewaters

The above- and below-ground growth of Schoenoplectus validus (Vahl) A. Löve & D. Löve was investigated in piggery and dairy farm wastewaters. Experiments were carried out in batch-fed gravel-bed wetland microcosms (190 1), fitted with root-observation panels. Growth in wastewater was compared with that in diluted and nutrient-amended wastewaters, a complete inorganic nutrient solution and tap water. S. validus was capable of growth over a wide range of nutrient and organic matter strengths. Above-ground growth was up to two times greater in the higher-strength wastewaters than in nutrient solution alone, despite similar or higher nutrient levels in the latter. Even dilute additions of wastewater (N<3 gm −3 and P<10 gm −3) to the nutrient solution (N>200 g m −3 and P>45 g m −3) resulted in significant growth enhancement. Mean above- and below-ground biomass of around 2.0 kg dry wieght (DW) m −2 and 1.25 kg DW m −2, respectively, were recorded in primary dairy wastewater alone, rising to 3.3 kg DW m −2 and 1.5 kg DW m −2, respectively, with nutrient amendment. Maximum crop growth rates of up to 29 g m −2 day −1, and demographic growth rates of up to 25 m (culm length) m −2 day −1, and 24 culms m −2 day −1 were recorded over the 116 day culture periods. Plant uptake of N and P decreased from 435 and 93%, respectively, at low nutrient concentrations to 6% and 7% as the nutrient content of the culture solutions was increased, and below-ground:above-ground biomass allocation decreased from around 3 to 0.45. Rhizomes commonly made up around 8% of the below-ground biomass. Rooting depths in the-strength organic wastewaters tested were reduced compared with those in nutrient solutions with similar or higher nutrient levels, and also with increasing wastewater addition to nutrient solution, suggesting that factors associated with organic compounds present in the wastewater (e.g. biological oxygen demand), rather than increasing nutrients, led to restricted root penetration. Root death was noted in plants growing in piggery wastewaters, where high ammonia concentrations (mean 222 g m −3) were at potentially phytotoxic levels.

Above-ground and below-ground biomass allocation in important fuelwood trees from arid north-western India

Above-ground and below-ground biomass and its allocation pattern in 6-year-old trees of nine species, Acacia catechu, A. nilotica subsp. indica, Albizia lebbeck, Azadirachta indica, Dalbergia sissoo, Melia azedarach, Morus alba, Prosopis cineraria and Ziziphus mauritiana from arid north-western India were studied. The above-ground biomass (kg/tree) varied from 11·6 in Z. mauritiana to 37·5 in Melia azedarach. Maximum biomass (39-65%) was allocated to the boles and a lesser amount to the branches (22-40%) and roots (9-29%). Root biomass (kg/tree) ranged from 2·2 in A. catechu to 8·7 in Albizia lebbeck. Net primary production was from 0·98 to 9·33 kg/tree/year across the species.

Effects of thinning and nitrogen fertilization on growth of Scots pine trees: total annual biomass increment, needle efficiency, and aboveground allocation of biomass increment

The effects of thinning and nitrogen fertilization, singly and in combination, on growth of 45-year-old Scots pine (Pinussylvestris L.) trees in northern Sweden were examined for 5 years after treatment. Annual examination of trees determined height growth, diameter growth, crown development, annual biomass increment, aboveground biomass allocation, and needle efficiency in relation to treatments. Nitrogen fertilization increased total dry matter production. The combination of thinning and nitrogen fertilization increased total dry matter production per tree more than the additive effects of thinning and nitrogen fertilization singly. Dry matter production per hectare was increased by nitrogen fertilization. Needle efficiency, i.e., total annual aboveground biomass production per unit of needle mass, was also increased by nitrogen fertilization. The increased aboveground production after nitrogen fertilization resulted from both an increase in biomass of needles and from the increased needle efficiency. The allocation pattern indicated that an increased production of stemwood was a result of a larger biomass of needles. An increase in cone production of the control trees was associated with a decrease in needle efficiency.

The Effect of Competition and Slope Inclination on Aboveground Biomass Allocation of Understorey Ferns in Subtropical Forest

The effects of competition for light and slope inclination on aboveground biomass allocation were studied for 6 fern species from herbaceous understoreys from subtropical evergreen broadleaved forest in the People's Republic of China. Plants from dense herbaceous understoreys had taller petioles and allocated significantly more biomass to supporting tissue relative to photosynthetically active leaf tissue than plants from open stands. The relative amount of biomass allocated to veins was not significantly affected by stand-density. In dense stands the inclination of the slope had no significant additional effect on the pattern of aboveground biomass allocation nor on the petiole length of the ferns

Patterns in aboveground carbon allocation and tree architecture that favor stem growth in young Scots pine from high latitudes.

The production and allocation of aboveground biomass and the characteristics of tree architecture were examined in eight-year-old Scots pine (Pinus sylvestris L.). Considerable among-tree variation existed in tree architecture, total aboveground dry mass production, and dry mass partitioning among tree parts. A linear relationship existed between needle and branch mass. Stem mass was directly proportional to tree height, which in turn was directly proportional to the allocation ratio between stem mass and total needle + branch mass production. The architectural characteristics that were related to a high proportional allocation to stem and high stemwood production were a large mean shoot volume, large mean number of branches per whorl, long needle retention and a high crown length/crown width ratio. Individual trees were found that combined high stemwood production with both high harvest index and high stemwood specific gravity.

Correlations Between Biomass Allocation, Relative Growth Rate and Light Environment in Tropical Forest Saplings

The growth rates and patterns of aboveground biomass allocation were determined for saplings of nine species of a wet tropical forest in Costa Rica. Relative growth rate and allocation were calculated by remeasuring the dimensions of forest-grown saplings and using biomass-dimension relationships derived from harvested saplings to convert linear dimensions to biomass estimates. The light environment of each sapling was characterized in terms of direct and indirect site factors calculated from hemispherical 'fisheye' photographs of the canopy. Relative growth rate (RGR) was significantly correlated with both direct and indirect site factors. A significant negative correlation was found between ln(% leaf allocation) and RGR for six species, but no such correlation occurred for the three species most highly associated with canopy gaps. Thus, shade-tolerant saplings shift most of their above-ground growth to leaf replacement when heavily shaded, while gap-associated species allocate about 2/3 of aboveground growth to the stem and branches under all measured conditions. This differential plasticity in leaf vs wood allocation may be an important factor in determining the shade tolerance and successional status of woody species. Key-words: Allocation, growth, light, sapling, tropical