Allometric Ratios Research Articles

Substrates based on swine wastewater in the production of seedlings of Guazuma ulmifolia (Malvaceae)

Abstract Swine wastewater (sw) can boost seedling growth and development in several species as this residue is rich in nutrients required by plants. This study tested the hypothesis that seedlings of Guazuma ulmifolia grown in a substrate based on swine wastewater showed better physiological and morphological performance. The seedlings were cultivated in seven substrates: T1 - rice husk and vermiculite; T2 - 20% sw; T3 - 40% sw; T4 - 60% sw; T5 - 80% sw; T6 - 100% sw; and T7 - 100% Bioplant®. Were evaluated the height (H), diameter (D), number of leaves (NF), as well as the H to D ratio, chlorophyll indices, gas exchange, biomass, allometric ratios, Dickson Quality Index (DQI), and mortality percentage of the seedlings. The data were analyzed by analysis of variance, and the means were compared by Tukey’s test. The substrates with the highest percentage of swine sludge promoted the highest H, D, NF, chlorophyll indices, gas exchange, stem biomass and IQD. The highest mortality was obtained in commercial substrate (85%) and carbonized rice husk and vermiculite (37.5%). Can be concluded that the substrates with high swine wastewater content were better for seedling G. ulmifolia.

Ureia como fonte de nitrogênio na fisiologia e crescimento inicial de <i>Guazuma ulmifolia</i> Lam. (Malvaceae)

O objetivo deste estudo foi determinar de que forma as mudas de Guazuma ulmifolia respondem a doses nitrogenadas, tendo como fonte de nitrogênio (N) a ureia. O cultivo das mudas ocorreu em delineamento inteiramente ao acaso, as quais foram submetidas a cinco doses (0, 50, 100, 150 e 200 mg dm-³) de N. Aos 120 dias de cultivo foram realizadas avaliações biométricas, fisiológicas, acúmulo de biomassa, razões alométricas, índice de qualidade de Dickson (IQD), teor, acúmulo e eficiência do uso de N (EUN) na parte aérea das mudas. Os dados foram submetidos a análise de variância e regressão. Além disso, o coeficiente de correlação de Pearson também foi analisado. As doses de N promoveram significativamente (p≤0,05) o aumento do teor de N na parte aérea das mudas. Por outro lado, registrou-se a redução significativa do acúmulo de N, de variáveis fisiológicas, crescimento, biomassa, IQD e EUN, que culminou em correlação negativa com o fornecimento crescente de N. Doses de N muito elevadas, tendo como fonte a ureia, foram prejudiciais para as mudas de Guazuma ulmifolia. As doses entre 20 e 38,8 mg dm-³ de N, de modo geral, foram as que promoveram os melhores resultados.

Comparative morphological analysis of diploid and triploid oysters, Crassostrea gigas, farmed in the Black Sea

Triploid organisms, in particular oysters, are widely used in marine aquaculture. However, the advantage of triploid oysters compared to diploids has not been proven in all cases. Comparative morphological analysis of Pacific oysters Crassostrea gigas of different ploidy levels allows evaluating the benefits of raising triploids in the Black Sea. First, the morphological characteristics of diploid and triploid Pacific oysters C. gigas farmed in the Black Sea were studied. Allometric ratios of weight (W, g) and shell height (H, mm) of oysters were obtained, which are described by the equations W$_{2n}$ = 4 × 10$^{-4}$ × H$_{2n}$ $^{2.56}$, R2 = 0.86 and W$_{3n}$ = 9 × 10$^{-5}$ × H$_{3n}$ $^{2.90}$, R$^{2}$ = 0.91. Triploids showed positive allometry and had more biomass at smaller shell height than diploid oysters. A clear linear relationship of the height and length of oyster shells was established. Significant differences in linear parameters between 2n and 3n C. gigas farmed in Donuzlav Liman are not seen. Based on these results, it is assumed that the advantage of the growth of 3n mollusks is less evident in farms located at high latitudes. The environmental factors and farm technology have probably affected the growth of oysters to a greater degree than their ploidy.

Dynamic coupling of allometric ratios to a process-based forest growth model for estimating the impacts of stand density changes

Abstract Process-based models are increasingly applied for simulating long-term forest developments in order to capture climate change impacts and to investigate suitable management responses. Regarding dimensional development, however, allometric relations such as the height/diameter ratio, branch and coarse root fractions or the dependency of crown dimension on stem diameter often do not account for environmental influences. While this may be appropriate for even-aged, monospecific forests, serious biases can be expected if stand density or forest structure changes rapidly. Such events occur in particular when forests experience disturbances such as intensive thinning or during early development stages of planted or naturally regenerated trees. We therefore suggest a calculation of allometric relationships that depends primarily on neighbourhood competition. Respective equations have been implemented into a physiology-based ecosystem model that considers asymmetric competition by explicit simulation of resource acquisition and depletion per canopy layer. The new implementation has been tested at two sites in Germany where beech (Fagus sylvatica) saplings have either been planted below a shelterwood of old spruces (Picea abies) or grown under clear-cut conditions. We show that the modified model is able to realistically describe tree development in response to stand density changes and is able to represent regeneration growth beneath a gradually decreasing overstorey of mature trees. In particular, the model could represent the faster crown size development in saplings until full ground coverage is established and a faster height growth afterwards. The effect enhances leaf area and thus assimilation per tree and increases carbon availability for stem growth at early development stages. Finally, the necessity to consider dynamic allometric relations with respect to climate change impacts is discussed, and further improvements are suggested.

Root biomass in cereals, catch crops and weeds can be reliably estimated without considering aboveground biomass

Reliable information on belowground plant biomass is essential to estimate belowground carbon inputs to soils. Estimations of belowground plant biomass are often based on a fixed allometric relationship of plant biomass between aboveground and belowground parts. However, environmental and management factors may affect this allometric relationship making such estimates uncertain and biased. Therefore, we aimed to explore how root biomass for typical cereal crops, catch crops and weeds could most reliably be estimated. Published and unpublished data on aboveground and root biomass (corrected to 0–25cm depth) of cereal crops (wheat and barley), catch crops and weeds were collected from studies in Denmark. Leave one out cross validation was used to determine the model that could best estimate root biomass.Root biomass varied with year, farming system (organic versus conventional) and cereal species. Shoot and root biomass of catch crops were higher than for weeds (sampled in late autumn), and farming system significantly affected root biomass of catch crops and weeds. The use of fixed root biomass based on the most influential factors (farming system and species) provided the lowest error of prediction for estimation of root biomass, compared with the use of fixed allometric relations, such as root/shoot ratio. For cereal crops, the average root dry matter in organic farming systems was 218gm−2 (243 and 193gm−2 for wheat and barley, respectively), but in conventional systems only 139gm−2 (142 and 129gm−2 for wheat and barley, respectively). For catch crops and weeds, the root dry matter in organic farming systems were around 127 and 35gm−2, and in conventional farming systems 75 and 28gm−2, respectively.In conclusion, the present analysis indicates that root biomass in cereals, catch crops and weeds can be reliably estimated without considering aboveground biomass, and it may be better estimated using fixed values based on species and farming systems than using fixed allometric ratios.

Determination of organic materials quality based on nutrient recovery, mineral fertilizer equivalency and maize (Zea mays L.) allometry

ABSTRACTCrop production in Sub-Saharan Africa is primarily limited by soil fertility decline. In view of this, the fertilizer value of locally available organic materials (OMs) was assessed for their nutrient release to crop growth. Crop residues and farmyard manure (FYM) were evaluated along with mineral fertilizers to grow a test crop maize variety – Gibe 2. The maize allometric parameters, nutrient ratios (NRs), nutrient recovery (NRy) and mineral fertilizer equivalency (MFE) were used to assess the mineral fertilizer value (MFV) of OMs. MFE of OMs was estimated as the available mineral N and P out of the fraction of total nitrogen and phosphorus applied relative to mineral fertilizers supply. The results revealed that maize allometry, NRy and MFE were significantly influenced by fertilizer sources. OM amendment resulted in poor maize allometry and low NRy. Interestingly, MFE of OM amended ranged from −201% with chickpea (CHP) residue to 63% with FYM. The results demonstrate that CHP has the poorest quality, while FYM is a good-quality OM as a fertilizer source.

Allometry of early growth in selected and wild sources of white spruce, Picea glauca (Moench) Voss

White spruce (Picea glauca) is commonly planted in timberlands of the upper Great Lakes region. Genetically improved seed, sourced from selected genotypes and propagated in seed orchards, is a primary seed source for artificial regeneration. Volume improvements gained by planting selected genotypes of Picea glauca sources range from 9 to 30 %; however, tradeoffs associated with selection for volume are relatively unexplored for allometry and needle traits. Biomass allocation is of particular interest, especially if increased wood production comes at the expense of root allocation. Open-pollinated seedlings from wild and selected genotypes were planted. Sixty seedlings per source were destructively sampled per year after 1, 2, 3, 4, and 5 growing seasons. Roots, stems, and needles were separated, dried and weighed. Tree height and caliper at root collar were measured, along with specific leaf area. Selected genotypes were allometrically similar to wild sources. Tree heights and biomass allocation were similar between sources during years 2–4. By year 5, selected genotypes averaged 30 % more volume and root mass than wild sources but maintained similar allometric ratios. SLA declined with each year and did not differ between sources. Our results suggest that superior volume growth in selected stock is not the result of alterations in biomass allocation or needle morphology: increases in stem mass were associated with tandem increases in root mass.

An individual-based process model to simulate landscape-scale forest ecosystem dynamics

Forest ecosystem dynamics emerges from nonlinear interactions between adaptive biotic agents (i.e., individual trees) and their relationship with a spatially and temporally heterogeneous abiotic environment. Understanding and predicting the dynamics resulting from these complex interactions is crucial for the sustainable stewardship of ecosystems, particularly in the context of rapidly changing environmental conditions. Here we present iLand (the individual-based forest landscape and disturbance model), a novel approach to simulating forest dynamics as an emergent property of environmental drivers, ecosystem processes and dynamic interactions across scales. Our specific objectives were (i) to describe the model, in particular its novel approach to simulate spatially explicit individual-tree competition for resources over large scales within a process-based framework of physiological resource use, and (ii) to present a suite of evaluation experiments assessing iLands ability to simulate tree growth and mortality for a wide range of forest ecosystems. Adopting an approach rooted in ecological field theory, iLand calculates a continuous field of light availability over the landscape, with every tree represented by a mechanistically derived, size- and species-dependent pattern of light interference. Within a hierarchical multi-scale framework productivity is derived at stand-level by means of a light-use efficiency approach, and downscaled to individuals via local light availability. Allocation (based on allometric ratios) and mortality (resulting from carbon starvation) are modeled at the individual-tree level, accounting for adaptive behavior of trees in response to their environment. To evaluate the model we conducted simulations over the extended environmental gradient of a longitudinal transect in Oregon, USA, and successfully compared results against independently observed productivity estimates (63.4% of variation explained) and mortality patterns in even-aged stands. This transect experiment was furthermore replicated for a different set of species and ecosystems in the Austrian Alps, documenting the robustness and generality of our approach. Model performance was also successfully evaluated for structurally and compositionally complex old-growth forests in the western Cascades of Oregon. Finally, the ability of our approach to address forest ecosystem dynamics at landscape scales was demonstrated by a computational scaling experiment. In simulating the emergence of ecosystem patterns and dynamics as a result of complex process interactions across scales our approach has the potential to contribute crucial capacities to understanding and fostering forest ecosystem resilience under changing climatic conditions.

Modelling growth and primary production of the marine mangrove ( Rhizophora apiculata BL): A dynamic approach

A mathematical model was developed to simulate the growth dynamics of monospecific stands of the marine mangroves ( Rhizophora apiculata), based on physiological and morphological processes. Six variables to describe the tree organs and three morphological variables to illustrate the growth pattern were selected and incorporated in the model. The growth pattern was described by using a series of mathematical relationships. Net tree growth was derived from the combined effect of photosynthesis, respiration, and mortality. Net primary production was allocated to the tree organs based on their allometric ratios. Coefficients reported in literature were used to simulate the life history and demographics of R. apiculata. Initial diameter at breast height ( DBH), daily global radiation and mean air temperature are some of the inputs that were used to calculate the biomass and demographic parameters, using daily time steps. The model was capable of simulating the growth dynamics of R. apiculata stands at lower latitudes, with reasonable accuracy ( R 2 ≥ 0.80). However, the predictions at higher latitudes exhibited unsatisfactory model fits. This discrepancy in observations at higher latitudes is probably due to other factors like rainfall distribution, soil structure, which were not incorporated in the model structure.

Biomass partitioning in a miniature-scale loblolly pine spacing trial

Stand conditions influence the partitioning of biomass to stem, needle, branch, and root components. Using data from 4- to 6-year-old loblolly pine ( Pinus taeda L.) trees grown in a miniature-scale spacing trial, this study determined the effect of initial spacing on the biomass partitioning of loblolly pine. Multivariate analysis of variance procedures concluded that row and column spacing did not have a significant effect on the relative amount of biomass among tree components. Root/shoot and height/diameter ratios, however, differed across densities, indicating that allometric-based partitioning tradeoffs occurred. Results from the miniature-scale trees showed trends similar to those observed with mature-sized trees at operational spatial scales. Stem and woody roots were 70% and 14% of total mass, respectively. Since these trees were physiologically young at the time of harvest, the allocation of mass to needle continued to be a priority, accounting for 10% of the total mass. Initial planting spacing did not directly affect partitioning patterns; however, allometric ratios offered some evidence that partitioning may have changed between above- and below-ground tree components. This analysis offers insight into using principles from similarity analysis to analytically relate biomass partitioning from miniature to operational spatial scales.

Quercus ilexShows Significant Among‐Population Variability in Functional and Growth Traits but Maintains Invariant Scaling Relations in Biomass Allocation

Analysis of the intraspecific patterns of variation in ecologically relevant traits is important for knowing the genetic potential of a species to adjust to the expected increase in the severity of drought in the Mediterranean region. In this study, we aim to know to what extent phenotypic variation in functional and structural attributes of three provenances of Quercus ilex L. subsp. ballota (Desf.) Samp. saplings is genetically based. In an experiment conducted in growth chambers, we assessed the effects of two levels of water (well watered and water stressed) and light (20 and 130 μmol m−2 s−1) on gas exchange, chlorophyll fluorescence, and leaf reflectance at different times throughout the experiment. At the end of the experiment, we measured leaf area, stem length and diameter, stomatal density, dry mass, and biomass allocation. Saplings from one of the populations (Sayago) performed better than those from the other two, showing higher photochemical efficiency and chlorophyll content and greater leaf, stem, and root dry mass. Saplings from Sayago also showed higher transpiration rates, stomatal density, and conductance and were less susceptible to photoinhibition than other two. The significant population‐associated variations in functional and structural attributes provided indirect evidence indicating that the holm oak exhibits an important degree of heterogeneity in the genetic constitution of its populations. However, the slopes of the biomass allometric relationships and allocation ratios showed that, irrespective of population, plants followed the same patterns of development in terms of biomass allocation, suggesting that evolutionary pressures may be acting to maintain allometric ratios at specific values.

Acclimation of Russian forests to recent changes in climate.

Assessments made over the past few decades have suggested that boreal forests may act as a sink for atmospheric carbon dioxide. However, the fate of the newly accumulated carbon in the living forest biomass is not well understood, and the estimates of carbon sinks vary greatly from one assessment to another. Analysis of remote sensing data has indicated that the carbon sinks in the Russian forests are larger than what has been estimated from forest inventories. In this study, we show that over the past four decades, the allometric relationships among various plant parts have changed in the Russian forests. To this end, we employ two approaches: (1) analysis of the database, which contains 3196 sample plots; and (2) application of developed models to forest inventory data. Within the forests as a whole, when assessed at the continental scale, we detect a pronounced increase in the share of green parts (leaves and needles). However, there is a large geographical variation. The shift has been largest within the European Russia, where summer temperatures and precipitation have increased. In the Northern Taiga of Siberia, where the climate has become warmer but drier, the fraction of the green parts has decreased while the fractions of aboveground wood and roots have increased. These changes are consistent with experiments and mathematical models that predict a shift of carbon allocation to transpiring foliage with increasing temperature and lower allocation with increasing soil drought. In light of this, our results are a possible demonstration of the acclimation of trees to ongoing warming and changes in the surface water balance. Independent of the nature of the observed changes in allometric ratios, the increase in the share of green parts may have caused a misinterpretation of the satellite data and a systematic overestimation by remote sensing methods of the carbon sink for living biomass of the Russian forest.

Verification of 3-PG growth and water-use predictions in twelve Eucalyptus plantation stands in Zululand, South Africa

Process-based forestry models are seen by the South African forestry industry as potentially useful tools for improving predictions of growth and water use in forest plantations. The 3-PG process-based forest model was evaluated in South Africa using limited Eucalyptus and Pinus trial data, with encouraging results. Some uncertainty exists, however, over whether 3-PG will prove to be a practical forest management tool on forestry estates that typically comprise scores of compartments (planted even-aged stands) covering a wide range of site conditions, species/clone and tree age. Two important questions require answers: (i) is 3-PG capable of modelling growth over a wide range of site growth potential to useful accuracy and (ii) are there practical methods for estimating or measuring all of the required parameter values for the model? To answer these questions, 12 stands of Eucalyptus grandis×camaldulensis hybrid clones, representing early, mid and late rotation age, and covering a wide range of site growth potential in the Zululand region (KwaZulu-Natal Province), were intensively studied over a period of 12 months. Measurements of initial and final biomass, leaf area index, biomass allometric ratios, litterfall, specific leaf area, sap-flow rates, pre-dawn xylem pressure potential and weather conditions were made throughout the year. Two influential site parameter values (maximum available soil-water capacity and a soil fertility rating) required indirect estimation, since relevant information was lacking and difficult to obtain from the field. A pragmatic approach to estimating these parameters is described. Annual tree growth predicted by the model, and daily ranges of sap flow, were compared to field measurements. Predictions of annual growth increment (dry mass of stems and branches) were acceptable for 11 of the 12 stands ( Y=0.85 X+1.7, r 2=0.84). The twelfth stand, which had an extremely high annual growth increment, high leaf area and year-long access by the trees to shallow groundwater, was substantially underpredicted. This is attributed to likely physiological adaptions to the long-term absence of water stress at this site. We conclude that 3-PG can realistically simulate growth and water use over a wide range of rotation age and growth conditions. Preliminary sets of model parameter values for a range of diverse stands may be estimated over a relatively short period using simple field equipment and techniques. Further testing of these parameter values at physiologically significant times over the remainder of the rotation is recommended to test model output and permit fine-tuning of parameters.

Hydraulic architecture and the evolution of shoot allometry in contrasting climates

We used pairs of congeneric shrub species from contrasting habitats to test for repeated evolutionary divergence in leaf-stem allometry and shoot hydraulic architecture in response to water availability. Allometric relationships and mean ratios between leaf size (individual and total area and mass per shoot) and stem cross-sectional area were compared between habitats using six species pairs representing three genera (Arctostaphylos, Baccharis, Ceanothus). We measured correlations among evolutionary changes in allometric, morphological, and physiological traits using phylogenetic independent contrasts. Allometric analysis revealed habitat differences: slopes were homogeneous among species (=1.46), but the more mesic-adapted species generally supported more leaf area at a common stem cross-sectional area. Reducing bivariate allometry to a ratio obscured this pattern because ratios varied with stem size, which was unrelated to habitat. Mean individual leaf size also was not correlated with either water availability or leaf-stem allometry. Stem hydraulic conductivity was generally lower in the xeric-adapted species of each pair, and its evolution mirrored changes in shoot allometry. This study provides evidence for repeated evolutionary divergence in shoot allometry and hydraulic architecture associated with water availability and demonstrates the importance of shoot allometry to water relations, independent of leaf size.

Effects of phenology, water availability and seed source on loblolly pine biomass partitioning and transpiration.

One-year-old loblolly pine (Pinus taeda L.) seedlings from four seed sources (Arkansas, Georgia, Texas and Virginia) grown in 1-m-deep sand-filled pits in two water regimes (well-watered and drought) were studied, to gain insight into the process of seedling establishment. Whole-plant transpiration was measured biweekly from July to December. Whole-plant harvests were conducted at 6-week intervals from April to December. Whole-plant transpiration and transpiration per unit leaf and root area were affected by treatment, seedlot and phenology. Seedlings of the Arkansas seedlot maintained significantly higher transpiration rates per unit leaf and root area during drought than seedlings of the Virginia, Georgia or Texas seedlots, but did not accumulate greater biomass. The high transpiration rates of the Arkansas seedlings were attributed to their deep root systems. Allometric relationships indicated that, relative to the whole plant, biomass allocation to needles of drought-treated seedlings was enhanced during the summer (allometric ratio 1.09), whereas allocation to roots was enhanced in the spring and fall (allometric ratios of 1.13 and 1.09, respectively). Relative to the whole plant, biomass allocation to needles of well-watered seedlings was enhanced throughout the experiment (allometric ratio of 1.16 declining to 1.05), whereas the allometric ratio of root to total biomass was 0.89 or less throughout. Allometric relationships also indicated variation in biomass partitioning to roots in three soil layers (0-30, 30-60 and 60-100 cm), which differed among harvests in each soil layer. Root growth in both well-watered and drought-treated seedlings was concentrated in the top soil layer in the spring, shifted to the middle and bottom soil layers in the summer, and then increased in the top soil layer in the fall. Compared with well-watered seedlings, drought-treated seedlings had higher rates of root growth in the bottom soil layer in the fall, a characteristic that would confer tolerance to future periods of limited soil water availability.

Growth and crown architecture of two aspen genotypes exposed to interacting ozone and carbon dioxide

To study the impact of ozone (O 3) and O 3 plus CO 2 on aspen growth, we planted two trembling aspen clones, differing in sensitivity to O 3, in the ground in open-top chambers and exposed them to different concentrations of O 3 and O 3 plus CO 2 for 98 days. Ozone exposure (58 to 97 μl1 −1-h, total exposure) decreased growth and modified crown architecture of both aspen clones. Ozone exposure decreased leaf, stem, branch, and root dry weight particularly in the O 3 sensitive clone (clone 259). The addition of CO 2 (150 μl1 −1 over ambient) to the O 3 exposure counteracted the negative impact of O 3 only in the O 3 tolerant clone (clone 216). Ozone had relatively little effect on allometric ratios such as, shoot/ root ratio, leaf weight ratio, or root weight ratio. In both clones, however, O 3 decreased the shoot dry weight/shoot length ratio and shoot diameter. This decrease in wood strength caused both current terminals and long shoots to droop and increased the branch angle of termination. These results show that aspen growth is highly sensitive to O 3 and that O 3 can also significantly affect crown architecture. Aspen plants with drooping terminals and lateral branches would be at a competitive disadvantage in dense stands with limited light.

Allometric relationships in young seedlings of faba bean (Vicia faba L.) following removal of certain root types

Sink-source relationships and allometric ratios were studied in young seedlings of faba bean (Vicia faba L.) following pruning of some root types. The plants were grown in an aeroponic system allowing an easy access to each part of the root system, throughout the experiment, without disturbing the others. Root, leaf and stem growth as well as their mineral content were determined in one group of undisturbed plants (CTRL) and in four groups of plants treated as follows: TAP – the distal-free portion of the taproot was removed; HALF – half the laterals were removed; ALL – all lateral roots were removed, and TAP+HALF – both the distal part of the taproot and half of the laterals were removed. Removal of all the lateral roots (ALL) induced the development of a longer taproot but severely arrested shoot growth. Phosphorus, potassium and calcium contents were lower in the plants of the ALL treatment. However, the content of Mg was practically unaffected. The effect of the HALF treatment was hardly noticeable but the effects of TAP+HALF treatment were cumulative. The allometric relationships between the surface area of the roots and that of the leaves were restored within the experimental period, apparently due to reduction in shoot growth. Removal of the distal parts of the taproot did not cause an increase in shoot growth. This indicates that the strength of the sinks (mostly of lateral roots) rather than that of the source determines these relationships.

Allometry of fasting urinary nitrogen loss and basal metabolic rate in homeotherms

This paper presents a review of the use of allometric techniques and describes the possible theoretical basis for the allometry of BMR (Basal Metabolic Rate) and FUNL (Fasting Urinary Nitrogen Loss). Using the technique of allometry, it presents strong evidence of a relationship between metabolic body size W 0.75 with BMR, ONL (Obligatory Nitrogen Loss) and FUNL. It also shows convincingly a casual link between these three parameters. The mean interspecific equations calculated were: FUNL(mg/day) = 418W 0.75; ONL(mg/day) = 272W 0.75; BMR(kcal/day) = 71W 0.75. The mean allometric ratios were: FUNL BMR = 5.9 mgN kcal ; FUNL ONL = 1.54 ; ONL BMR = 3.8 mgN/kcal ; ONL FUNL = 0.65 . The allometric relationship between FUNL:BMR (of 6mgN/kcal) indicates that roughly 15% of protein energy is lost during fasting in animals ranging from a mouse to a steer. Moreover, the allometric relationship between FUNL:ONL suggests that FUNL may be used to estimate ONL and hence protein requirements across a wide range of animals.

Proximate Mechanisms of Sexual Selection in the Firefly Photinus pyralis (Coleoptera: Lampyridae)

Male competition in courtships of the firefly Photinus pyralis is intense. Morphometric analysis revealed that male size is variable, possibly exhibiting alternative body plans. We examined the outcomes of courtships to determine the proximate mechanisms of selection that may have led to male allometry. Two distinct selective events exist within mate competition: (1) searching and (2) scramble competition. Although many courtships failed, those without rivals were shorter and successful males spent less time in the “mate-guarding” position than when several males were in competition. Winners outflashed rivals, but flash dialogs occurred at similar frequencies across rival densities, indicating that females require some quantum of information before mating. Female flash preference was examined in choice tests to evaluate female discrimination ability. Females preferred flashes of greater intensity and precedence. This suggests that flash “synchronization” is a competitive display rather than a cooperative behavior to maintain female responsiveness. Selection for male size was density dependent: females preferred large males in searching, while small males were favored in scrambles. Simulated scrambles showed that small males have superior locomotor abilities, allowing them to reach the female rapidly. Comparison with a species lacking scrambles, P. macdermotti, revealed that selection in P. pyralis is disruptive, targeting traits alternately, and may have led to the evolution of higher allometric ratios in a species with direct male competition. Both male competition and female choice are important determinants of the outcome of P. pyralis courtships.

A generalised model of forest productivity using simplified concepts of radiation-use efficiency, carbon balance and partitioning

This paper describes a stand growth model, based on physiological processes, which incorporates a number of steps and procedures that have allowed considerable simplification relative to extant process-based models. The model, called 3-PG (use of Physiological Principles in Predicting Growth), calculates total carbon fixed (gross primary production; P G) from utilizable, absorbed photosynthetically active radiation (φ p.a.u.), obtained by correcting the photosynthetically active radiation absorbed by the forest canopy (φ p.a.) for the effects of soil drought, atmospheric vapour pressure deficits and stand age. P G is obtained from φ p.a.u. and the canopy quantum efficiency, values of which are becoming available. The ratio of net ( P N) to gross primary production is emerging as relatively constant for trees. This eliminates the need to calculate respiration and is used to estimate P N—the net amount of carbon converted to biomass. 3-PG uses a simple relationship to estimate the amount of carbon allocated below ground and a procedure based on allometric ratios—widely available for many species and situations—to determine the allocation of carbon to foliage and stems and constrain tree growth patterns. The effects of nutrition are incorporated through the carbon allocation procedure; the amount of carbon allocated below ground will increase with decreasing soil fertility. Recently acquired knowledge about the physiological factors causing decline in forest growth rates with age is used to model that decline. Changes in stem populations (self-thinning) are derived from a procedure based on the −32 power law, combined with stem growth rates. The model requires weather data as input, works on monthly time steps and has been run for periods up to 120 years, producing realistic patterns of stem growth and stem diameter increments. The time course of leaf area index is realistic for a range of soil conditions and atmospheric constraints. 3-PG can be run from remotely-sensed estimates of leaf area index coupled to weather data and basic, readily available information about soils and stand characteristics. It is being tested as a practical tool against forestry data from New South Wales, Tasmania, Victoria and New Zealand. Test results show excellent correspondence between stand growth measurements and simulated stem growth over 30 years.