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Biomass harvesting removes unmarketable vegetative material from timber harvests for use as cellulosic bioenergy, leaving only leaf litter. To test whether biomass harvests negatively affect red-backed salamander (Plethodon cinereus) populations, we set up coverboard arrays at 10 sites (mean 3.29 ha, range 2.35-4.61 ha) with varying degrees of biomass harvesting at the Southeast Purdue Agricultural Center (SEPAC) in Jennings County, Indiana. We monitored salamander artificial cover object (AGO) arrays within each site from spring 2012 to fall 2015 and marked all salamanders with visible implant elastomers, generating capture histories for all individuals. Using Program MARK and Pollock s robust design we developed 10 a priori candidate models to test salamander population parameters, with variations on capture probability, recapture probability, survival, emigration, and immigration, as well as a set of models comparing preharvest and postharvest data. To incorporate precipitation events, we classified sessions as wet or dry based on total rainfall prior to sampling. The best performing models were those that incorporated the year, season, and amount of precipitation when estimating capture probabilities. Linear regression results showed percentage of canopv cover and Downed Coarse Woody Derbies (DCWD) were significant predictors of salamander abundance. We also found no significant relationships between survival, DCWD, and canopy cover. Our results suggest DCWD has some impact on variations in population sizes of red-backed salamanders, although other factors are likely contributing as well., Introduction In response to increasing gas prices and the depletion of fossil fuels, the use of renewable biofuels as an alternative energy source is becoming a realistic option (Janowiak and [...]

Current biomass models for Chinese pine (Pinus tabulaeformis Carr.) fail to accurately estimate biomass in large geographic regions because they were usually based on limited sample trees on local sites, incompatible with stem volume, and not additive among components and total biomass. This study was based on mensuration data of individual-tree biomass from large samples of Chinese pine. The purpose was to construct compatible and additive biomass models using the nonlinear error-in-variable simultaneous equations and dummy variable modeling approach. This approach could ensure compatibility of an aboveground biomass model with a biomass conversion factor (BCF) and a stem volume model and compatibility of a belowground biomass model with a root-to-shoot ratio (RSR) model. Also, stem, branch, and foliage biomass models were additive to the aboveground biomass model. Results showed that mean prediction errors (MPEs) of the developed one- and two-variable aboveground biomass models were less than 4% and MPEs of the three-component (stem, branch, and foliage) and belowground biomass models were less than 10%. Furthermore, the effects of main climate variables on above- and below-ground biomass were analyzed. Aboveground biomass was related to mean annual temperature (MAT), while belowground biomass had no significant relationship with either MAT or mean annual precipitation (MAP). The developed models provide a good basis for estimating biomass of Chinese pine forests. Key words: aboveground biomass, belowground biomass, biomass conversion factor, root-to-shoot ratio, Pinus tabulaeformis. Les modeles actuels de biomasse du pin rouge de Chine (Pinus tabulaeformis Carriere) ne parviennent pas a estimer avec precision la biomasse pour de grandes regions geographiques parce qu'ils sont generalement etalonnes a partir d'un nombre limite d'arbres-echantillons dans des stations locales, qu'ils sont incompatibles avec les modeles de volume des arbres, et que la somme des composantes de la biomasse n'egale pas la biomasse totale. Cette etude est fondee sur les mesures de biomasse d'arbres individuels provenant d'un grand echantillon de pin rouge de Chine. L'objectif etait de construire des modeles de biomasse compatibles et additifs a l'aide d'une approche de modelisation utilisant des variables fictives et des equations non lineaires a resolution simultanee tenant compte des erreurs de mesure. Cette approche pourrait rendre le modele de biomasse aerienne compatible avec le facteur de conversion de la biomasse (FCB) et le modele de volume du tronc, et rendre le modele de biomasse racinaire compatible avec le modele du rapport entre les biomasses racinaire et aerienne (BRA). De plus, la somme des resultats des modeles de biomasse du tronc, des branches et des feuilles doit correspondre au resultat du modele de biomasse aerienne. Les resultats indiquent que les erreurs moyennes de prevision (EMP) des modeles de biomasse aerienne mis au point avec une et deux variables etaient inferieures a 4 %, alors que les EMP des modeles de biomasse des trois composantes aeriennes (tronc, branches et feuilles) et de la biomasse racinaire etaient inferieures a 10 %. En outre, nous avons analyse l'effet des principales variables climatiques sur les biomasses aerienne et racinaire. La biomasse aerienne etait reliee a la temperature annuelle moyenne (TAM) alors que la biomasse racinaire n'etait significativement reliee ni a la TAM, ni aux precipitations annuelles moyennes. Les modeles ainsi mis au point constituent un bon point de depart pour estimer la biomasse des forets de pin rouge de Chine. [Traduit par la Redaction] Mots-cles: biomasse aerienne, biomasse racinaire, facteur de conversion de la biomasse, rapport entre les biomasses racinaire et aerienne, Pinus tabulaeformis., 1. Introduction Forest biomass represents approximately 80% of all aboveground terrestrial carbon and 40% of belowground carbon (Dixon et al. 1994). Climate change has increased the need for information on [...]

Variation in terrestrial net primary production (NPP) with climate is thought to originate from a direct influence of temperature and precipitation on plant metabolism. However, variation in NPP may also result from an indirect influence of climate by means of plant age, stand biomass, growing season length and local adaptation. To identify the relative importance of direct and indirect climate effects, we extend metabolic scaling theory to link hypothesized climate influences with NPP, and assess hypothesized relationships using a global compilation of ecosystem woody plant biomass and production data. Notably, age and biomass explained most of the variation in production whereas temperature and precipitation explained almost none, suggesting that climate indirectly (not directly) influences production. Furthermore, our theory shows that variation in NPP is characterized by a common scaling relationship, suggesting that global change models can incorporate the mechanisms governing this relationship to improve predictions of future ecosystem function., Annual net primary production (NPP; [gm.sup.-2] [yr.sup.-4]) of woody plants is a major component of the terrestrial carbon cycle (1). Although it has long been known that NPP correlates with [...]

Adequate quantification of canopy fuel load and canopy bulk density is required for assessment of the susceptibility of forest stands to crown fire and evaluation of silvicultural treatments aimed at reducing the risk of crowning. The use of tree biomass equations and vertical profile distributions of crown fuels provide the most accurate estimates of the canopy fuel characteristics. In this study, 100 pole-size maritime pine (Pinus pinaster Aiton) trees were destructively sampled in five different sites, covering a wide range of its geographical distribution in the Iberian Peninsula. To estimate crown fuel mass, allometric equations were fitted separately for needles, twigs, and fuel available for crown fire. Models were also fitted to characterize the vertical fuel distributions as a function of tree height. All models were fitted simultaneously to guarantee additivity among tree biomass components, and corrections were also made for heterocedasticity and autocorrelation. Diameter at breast height was the best explanatory variable for all the allometric models. The vertical distribution of crown biomass fractions along tree height depended on the crown size and tree dominance. The system of equations provides a good balance between accurate predictions and low data requirements, allowing quantification of canopy fuel characteristics at stand level. Resume: La quantification adequate de la charge de combustibles et de la densite apparente dans le couvert forestier est necessaire pour evaluer la susceptibilite des peuplements forestiers a un feu de cime et les traitements sylvicoles visant a reduire le risque d'embrasement des cimes. L'utilisation des equations de biomasse des arbres et des profils de repartition verticale des combustibles de cimes procure les estimations les plus precises des caracteristiques des combustibles dans le couvert forestier. Dans cette etude, 100 tiges de pin maritime (Pinus pinaster Aiton) au stade du perchis ont ete echantillonnees de facon destructive dans cinq stations differentes representatives d'une vaste partie de l'aire de repartition de l'espece dans la peninsule iberique. Pour estimer la masse des combustibles de cimes, des equations allometriques ont ete ajustees separement pour les aiguilles, les rameaux et les combustibles disponibles pour un feu de cime. Des modeles ont egalement ete ajustes pour caracteriser la repartition verticale des combustibles en fonction de la hauteur des arbres. Tous les modeles ont ete ajustes simultanement pour s'assurer de l'additivite parmi les composantes de la biomasse des arbres et des corrections ont ete apportees pour l'heterocedasticite et l'autocorrelation. Le diametre a hauteur de poitrine etait la meilleure variable independante pour tous les modeles allometriques. La repartition verticale des fractions de biomasse de la cime sur la hauteur d'un arbre dependait de la dimension de la cime et de la dominance de l'arbre. Le systeme d'equations constitue un bon equilibre entre la precision des predictions et la quantite de donnees necessaires et permet de quantifier les caracteristiques des combustibles dans le couvert forestier a l'echelle du peuplement. [Traduit par la Redaction], Introduction Many pine-dominated forests across the Mediterranean area are managed with the aim of maximizing biomass production, which makes them susceptible to high-severity wildfires. Better knowledge of the distribution of [...]

The drive to develop and expand alternatives to fossil fuel engages scientists and entrepreneurs around the world at levels never before witnessed. Increasingly, consumers are being urged to imagine a [...]

Forests store a large portion of global carbon in tree and soil biomass. However, our understanding of the factors that may reduce rates of forest carbon accumulation is incomplete. This study examines the impact of an exotic insect and fungal pathogen disease on aboveground tree biomass in forests of eastern North America. We determine how beech bark disease (BBD)--a pervasive but nonextirpating disease--influences the growth and survival of its host tree, Fagus grandifolia Ehrh., and the effects of changes in the demography of this late-successional dominant tree species on total stand-level aboveground tree biomass. Our analyses use US Forest Service Forest Inventory and Analysis data from eastern states located along a gradient in the time since introduction of BBD. In Maine, where BBD has been present for >50 years, we observed reduced growth and survival of the host tree and reduced overall stand-level aboveground tree biomass compared with states where BBD arrived more recently. Additionally, there is a negative relationship between host tree abundance and overall stand-level aboveground tree biomass. Where beech is most abundant, BBD results in substantial declines in aboveground tree biomass (e.g., 11% in Maine); where beech is less abundant, we expect more modest declines (1%-4%). Resume: Les forets emmagasinent une grande portion du carbone global dans la biomasse des arbres et du sol. Cependant, notre comprehension des facteurs qui peuvent reduire le taux d'accumulation du carbone forestier est incomple`te. Cette etude examine l'impact d'un insecte exotique et d'une maladie causee par un champignon pathoge`ne sur la biomasse aerienne dans les forets de l'est de l'Amerique du Nord. Nous avons determine de quelle facon la maladie corticale du hetre (MCH), une maladie omnipresente mais impossible a eradiquer, influence la croissance et la survie de son hote, Fagus grandifolia Ehrh., ainsi que les effets des changements demographiques chez cette espece dominante de fin de succession sur la biomasse aerienne totale des arbres a l'echelle du peuplement. Nos analyses utilisent les donnees du Programme d'analyse et d'inventaire forestier du Service forestier des E tats-Unis provenant des etats de l'est situes le long d'un gradient temporel d'apparition de la MCH. Dans le Maine, ou la MCH est presente depuis plus de 50 ans, nous avons observe une reduction de la croissance et de la survie de l'hote et une reduction globale a l'echelle du peuplement de la biomasse aerienne des arbres, comparativement aux etats ou la MCH est arrivee plus recemment. De plus, il y a une relation negative entre l'abondance de l'hote et la biomasse aerienne globale a l'echelle du peuplement. Dans les endroits ou le hetre est le plus abondant, la MCH reduit de facon importante la biomasse aerienne des arbres (p. ex. 11 % dans le Maine); dans les endroits ou le hetre est moins abondant, on s'attend a des reductions plus modestes (1-4 %). [Traduit par la Redaction], Introduction Forests play an important role in mitigating the negative impacts of contemporary climate change by absorbing and storing roughly 10% of global carbon emissions (Food and Agriculture Organization of [...]

Simulating the effects of possible environmental changes on the forest carbon budget requires the use of calibrated and tested models of ecosystem processes. A recently proposed simulation approach based on the use of the BIOME-BGC model was applied to yield estimates of present carbon fluxes and pools in Tuscany forests (central Italy). After the validation of these estimates against existing ground data, the simulation approach was used to assess the impact of plausible climate changes (+2 °C and increased [CO.sub.2] concentration) on forest carbon dynamics (gross primary production (GPP), net primary production (NPP), and relevant allocations). The results indicate that the temperature change tends to inhibit all production and allocation processes, which are instead enhanced by the [CO.sub.2] concentration rise. The combination of the two factors leads to a general increase in both GPP and NPP that is higher for deciduous oaks and chestnut (+30% and 24% for GPP and +42% and 31% for NPP, respectively). Additionally, vegetation carbon is slightly increased, while total soil carbon remains almost unchanged with respect to the present conditions. These findings are analyzed with reference to the Tuscany forest situation and previous studies on the subject. Resume: Pour simuler les effets de changements environnementaux potentiels sur le bilan du carbone des forets, il faut utiliser des modeles de processus des ecosystemes qui ont ete calibres et testes. Une approche de simulation proposee recemment et basee sur l'utilisation du modele BIOME-BCG a ete appliquee pour produire des estimations des flux actuels et des reservoirs de carbone dans les forets de la Toscane, dans le centre de l'Italie. Apres avoir valide ces estimations avec les donnees terrain existantes, la simulation a ete utilisee pour evaluer l'impact de changements climatiques plausibles (+2 °C et augmentation de la concentration de [CO.sub.2]) sur la dynamique du carbone de la foret (production primaire brute (PPB), production primaire nette (PPN) et les locations pertinentes). Les resultats indiquent que le changement de temperature a tendance a inhiber tous les processus de production et d'allocation qui sont par contre stimules par l'augmentation de la concentration de [CO.sub.2]. La combinaison des deux facteurs se traduit par une augmentation generale de la PPB et de la PPN qui est plus elevee chez les chenes caducifolies et le chataignier (respectivement +30% et 24% pour la PPB et +42% et 31% pour la PPN). De plus, la quantite de carbone dans la vegetation est legerement plus elevee tandis que la quantite totale de carbone dans le sol demeure pratiquement inchangee par rapport aux conditions actuelles. Ces resultats sont analyses a la lumiere de la situation de la foret toscane et des etudes precedentes sur le sujet. [Traduit par la Redaction], Introduction The increasing level of atmospheric [CO.sub.2] and consequent global climate change are enhancing the need for assessing the amount of carbon stored by terrestrial ecosystems as well as for [...]

Abundant plant biomass has the potential to become a sustainable source of fuels and chemicals. Realizing this potential requires the economical conversion of recalcitrant lignocellulose into useful intermediates, such as sugars. We report a high-yielding chemical process for the hydrolysis of biomass into monosaccharides. Adding water gradually to a chloride ionic liquid-containing catalytic acid leads to a nearly 90% yield of glucose from cellulose and 70-80% yield of sugars from untreated corn stover. Ion-exclusion chromatography allows recovery of the ionic liquid and delivers sugar feedstocks that support the vigorous growth of ethanologenic microbes. This simple chemical process, which requires neither an edible plant nor a cellulase, could enable crude biomass to be the sole source of carbon for a scalable biorefinery. biofuel | carbohydrate | ethanol fermentation | ionic liquid | lignocellulose www.pnas.org/cgi/doi/10.1073/pnas.0912073107

Species richness has been shown to increase biomass production of plant communities. Such overyielding occurs when a community performs better than its component monocultures due to the complementarity or dominance effect and is mostly detected in substrate-bound plant communities (terrestrial plants or submerged macrophytes) where resource use complementarity can be enhanced due to differences in rooting architecture and depth. Here, we investigated whether these findings are generalizeable for free-floating phytoplankton with little potential for spatial differences in resource use. We performed aquatic microcosm experiments with eight phytoplankton species belonging to four functional groups to determine the manner in which species and community biovolume varies in relation to the number of functional groups and hypothesized that an increasing number of functional groups within a community promotes overyielding. Unexpectedly, we did not detect overyielding in any algal community. Instead, total community biovolume tended to decrease with an increasing number of functional groups. This underyielding was mainly caused by the negative dominance effect that originated from a trade-off between growth rate and final biovolume. In monoculture, slow-growing species built up higher biovolumes than fast-growing ones, whereas in mixture a fast-growing but low-productive species monopolized most of the nutrients and prevented competing species from developing high biovolumes expected from monocultures. Our results indicated that the magnitude of the community biovolume was largely determined by the identity of one species. Functional diversity and resource use complementarity were of minor importance among free-floating phytoplankton, possibly reflecting the lack of spatially heterogeneous resource distribution. As a consequence, biodiversity-ecosystem functioning relationships may not be easily generalizeable from substrate-bound plant to phytoplankton communities and vice versa. Key words: biomass production; functional diversity; negative dominance effect; overyielding; phytoplankton primary producer; resource use complementarity; species richness, underyielding.

Under optimal partitioning theory (OPT), plants preferentially allocate biomass to acquire the resource that most limits growth. Within this framework, higher root mass under low nutrients is often assumed to reflect an allocation response to build more absorptive surface. However, higher root mass also could result from increased storage of total nonstructural carbohydrates (TNC) without an increase in non-storage mass or root surface area. To test the relative contributions of TNC and non-storage mass as components of root mass responses to resources, we grew seedlings of seven northern hardwood tree species (black, red, and white oak, sugar and red maple, American beech, and black cherry) in a factorial light x nitrogen (N) greenhouse experiment. Because root mass is a coarse metric of absorptive surface, we also examined treatment effects on fine-root surface area (FRSA). Consistent with OPT, total root mass as a proportion of whole-plant mass generally was greater in low vs. high N. However, changes in root mass were influenced by TNC mass in all seven species and were especially strong in the three oak species. In contrast, non-storage mass contributed to increased total root mass under low N in three of the seven species. Root morphology also responded, with higher fine-root surface area (normalized to root mass) under low vs. high N in four species. Although biomass partitioning responses to resources were consistent with OPT, our results challenge the implicit assumption that increases in root mass under low nutrient levels primarily reflect allocation shifts to build more root surface area. Rather, root responses to low N included increases in: TNC, non-storage mass and fine-root surface area, with increases in TNC being the largest and most consistent of these responses. The greatest TNC accumulation occurred when C was abundant relative to N. Total nonstructural carbohydrates storage could provide seedlings a carbon buffer when respiratory or growth demands are not synchronized with photosynthesis, flexibility in responding to uncertain and fluctuating abiotic and biotic conditions, and increased access to soil resources by providing an energy source for mycorrhizae, decomposers in the rhizosphere, or root uptake of nutrients. Key words: biomass allocation; biomass partitioning; fine roots; .fine root surface area; optimal partitioning theory; soil resources; storage; total nonstructural carbohydrates.

While benthic algal biomass is one of the most commonly measured variables within littoral communities, it is also one of the most poorly characterized. The use of chlorophyll a as an estimate of biomass, while easy and inexpensive, can be affected by changes in environmental conditions and algal community composition. Biovolume-based measurements often have high variability and are affected by changes in cell volume due to preservation. Using 12 years of data from the Experimental Lakes Area (northwestern Ontario, Canada) as well as short-term surveys and experimental studies from the Experimental Lakes Area and the Canadian Rocky Mountains, we demonstrate that biovolume and chlorophyll a are often decoupled in the littoral zone of temperate oligotrophic lakes. We recommend that researchers revisit the limitations of both metrics and specifically caution against the use of chlorophyll a as a biomass indicator when light, temperature, or species composition vary significantly. Resume: Bien que la biomasse des algues benthiques soit l'une des variables les plus frequemment mesurees dans les communautes littorales, c'est aussi l'une des moins bien caracterisees. L'utilisation de la chlorophylle a pour l'estimation de la biomasse, bien que facile et peu couteuse, peut etre affectee par des changements des conditions du milieu et par la composition de la communaute algale. Les mesures basees sur le biovolume ont souvent une forte variabilite et sont affectees par les changements des volumes cellulaires causes par les methodes de conservation. Nous utilisons des donnees etalees sur 12 ans provenant de la Region des lacs experimentaux (Ontario, Canada) ainsi que des inventaires a court terme et des etudes experimentales a la Region des lacs experimentaux et dans les Rocheuses canadiennes pour demontrer que le biovolume et la chlorophylle a sont souvent decouples dans la zone littorale des lacs oligotrophes temperes. Nous recommandons aux chercheurs de tenir compte des limitations des deux metriques et nous les mettons en garde specifiquement contre l'utilisation de la chlorophylle a comme indicateur de la biomasse lorsque la lumiere, la temperature ou la composition specifique varient de facon significative. [Traduit par la Redaction], Introduction A cursory review of most aquatic journals will reveal that algal biomass is a variable of interest but one that is frequently measured indirectly. Chlorophyll a is routinely used [...]

Crop and livestock production are rarely integrated together in modern farming systems. Reintegrating crops with livestock production has been shown to produce many agronomic and environmental benefits. The objective of this study was to evaluate how an integrated crop-livestock system would influence weed biomass and weed species composition compared with a conventional, continuous corn (Zea mays L.) cropping system. The experimental farming system used in this study was established on a 90-ha site near Pana, IL, in 2002. The integrated system included two phases: (i) a corn and oat (Avena sativa L) cash crop rotation, grown in summer, and (ii) post-harvest grazing of corn stover with annual cover crops. Over a 4-yr period (2004-2007), weed biomass was approximately 4.5 times higher in the conventional system (8.4 g [m.sup.-2]) compared with the integrated system (1.8 g [m.sup.-2]). Weed species composition was affected by the integrated system and showed a temporal disjunction between the time of year and weed life history. Surprisingly, cattle grazing on cropland had little effect on weed biomass or species composition. The primary drivers that suppress weed biomass and change species composition appear to be use of crop rotation and annual cover crops within the integrated system. Wider adoption of integrated crop-livestock systems, such as the one used in this study, should reduce reliance on herbicides compared with more conventional cropping systems.

The [C.sub.4] perennial grasses have many potential virtues as bioenergy crops--high productivity and water use efficiency, multiyear crop cycle that minimizes replanting costs, and wide environmental adaptation. In the productive San Joaquin Valley (SJV) of California, these species also confront high levels of ozone ([O.sub.3]) air pollution. It is often assumed that [C.sub.4] species will exhibit tolerance to [O.sub.3], relative to [C.sub.3] species, based on limited crop yield-loss data and on responses to a contrasting gaseous air pollutant, sulfur dioxide (S[O.sub.2]). Tolerance to [O.sub.3] of high-biomass [C.sub.4] crops such as sugarcane (Saccharum spp.) has not been demonstrated. Here we tested the hypothesis that a clone of sugarcane currently grown on a small commercial scale in the [O.sub.3]-impacted SJV will exhibit tolerance to [O.sub.3]. The hypothesis was disproven. Biomass production declined by over one-third and allocation to roots declined by over two-thirds, over a range of [O.sub.3] exposures (4, 58, and 114 ppb, 12-h means). These responses are comparable to responses previously reported for [O.sub.3]-sensitive [C.sub.3] crop species. Greater [O.sub.3] tolerance may be required to maximize the potential viability of bioethanol production using tall tropical grasses such as sugarcane (for sucrose) or energy canes (for cellulose) in [O.sub.3]-impacted western valleys. In the case of the locally successful sugarcane clone examined here, the [C.sub.4] photosynthetic pathway did not confer resistance to [O.sub.3] exposure.

Improving the biomass yield of switchgrass (Panicum virgatum L.) will improve its utility as a dedicated energy crop by increasing both its net and total energy yield per hectare. In a previous space-transplanted study, midparent heterosis for biomass yield was reported for population and specific [F.sub.1] hybrids of the Lowland-tetraploid cultivar Kanlow and the upland-tetraploid cultivar Summer. These two cultivars were proposed to be two different heterotic groups. The objective of this study was to determine the extent of heterosis for biomass yield in reciprocal Kanlow (K) and Summer (S) [F.sub.1] population hybrids grown in simulated swards and to determine the effect of advance in generation on biomass yield. Parent populations and their [F.sub.1], [F.sub.2], and [F.sub.3] population hybrids were grown in transplanted sward plots located near Mead, NE, for a three-year period. Plant density in the simulated swards was equivalent to acceptable stands in seeded plots. Plots were not harvested the establishment year to enable them to become fully established. Biomass yields were determined for the following two years. There was significant high-parent heterosis of 30 to 38% (P [less than or equal to] 0.01) for biomass yield for both the K x S [F.sub.1] and S x K [F.sub.1] hybrid populations. Heterosis for biomass yield declined with advance in generation. Heterosis for biomass yield in switchgrass may need the competitive conditions of swards to be fully expressed. Additional trials of specific hybrids established from seed are needed to further verify these conclusions. These results do provide ample justification for additional research to develop switchgrass population and specific hybrids.

We examined a series of eight pea genotypes differing in three naturally occurring allelic mutations, i.e., af (afila), st (stipules reduced), and tl (tendril-less) and three species, five cultivars, and one interspecific hybrid of tomato differing in SP (SELFPRUNING) allele composition to determine whether different phenotypes ontogenetically express different biomass partitioning patterns compared to the isometric poatitioning pattern and an interspecilic 3/4 scaling 'rule'' governing annual growth with respect to body mass. The slopes and 'elevations' (i.e., a and log [beta], respectively) of log-log linear regression curves of bivariate plots of leaf. stem, and root dry mass and of annual growth vs. total body mass were used to assess pattern homogeneity. The annual growth of all pea and tomato phenotypes complied with the 3/4 growth rule. The biomass partitioning patterns of all tomato phenotypes were statistically indistinguishable from the isometric pattern as were those of the pea wild type and three singlemutant genotypes. However, significant departures from the isometric (and pea wild type) biomass allocation pattern were observed for three genotypes, all of which were homozygous for the af allele. These results open the door to explore the heritability and genetics underlying the allometry of biomass partitioning patterns and growth. Key words: af (afila); allometry; Fabaceae; Lycopersicon esculentum; Lycopersicon pennellii; Lycopersicon pbnpinellifolium; leaf morphology; Piston sativum; scaling relationships; Solanaceae.

Politica and environmental concerns have resulted in a growing interest in renewable energy, especially transportation fuels. In the United States the majority of fuel etnanol s currently produced from corn (Zea mays L.) starcn but grain supplies will be insufficient to meet anticipated demands. Enzymatic hydrolysis of lignocellulosic biomass such as corn and sorghum [Sorghum bicolor [L.) Moench] stover can provide an abundant alternative source of fermentable sugars. While production of cellulosic ethanol from stover is feasible from an energy-balance perspective, its production is currently not economically competitive Along with improvements n bioprocessing, enhancing the yield and composition of the biomass has the potential to make ethanol production considerably more cost effective. This requires (i) a petter understanding of now cell wall composition and structure affect the efficiency of enzymatic hydrolysis. (ii) the development of traits that enhance biomass conversion efficiency and increase biomass yield, and (iii) the development of rapid screening protocols to evaluate biomass conversion efficiency. Several genetic resources are available to improve maize and soronum as sources of lignocellulosic biomass. This includes the use of existing mutants, forward and reverse genetics to obtain novel mutants, and transgenic approaches in which the expression of genes of interest is modified. Plant breeding can be implemented to improve biomass yield, biomass quality, and biomass conversion efficiency, either through selection among progeny obtained by crossing parents with desirable traits, or as a way to enhance the agronomic performance of promising mutants and transgenics. Examples from current research will be used to illustrate progress in these different areas.

Understanding the dependency of ecosystem processes on spatial and temporal scales is crucial in current efforts to model ecosystem responses to global change. Here we present a case of nonlinear interactions between temporal and spatial scales in a high spatial- and temporal-resolution study of fine-root biomass responses to edaphic and climatic variation in a lowland tropical rain forest (La Selva, Costa Rica). The spatiotemporal variation in fine roots in this forest was considerably greater than that for aboveground live biomass and litterfall. Standing stocks of both live and dead fine roots varied strongly during a seven-year period (up to 10-fold) and across two edaphic gradients with different soil nutrient and water variation (up to four-fold). Fine-root biomass decreased with soil fertility and volumetric soil water content, but responses across a landscape gradient (decreasing with total soil P and K and increasing with N:P ratio between two Oxisols with different weathering) differed from those across a topographic gradient in older Oxisols (increasing with total Fe and A1 and decreasing with Ca, Mg, and C:N ratio down the slopes). The spatial contrasts across the landscape gradient (but not in the topographic gradient) changed substantially through time, and they, in fact, disappeared entirely by the middle of the study interval. Shortterm monitoring of belowground standing biomass could thus lead to important biases when quantifying root responses. The positive time x gradient interaction in fine-root biomass across soil types (but not downslope) also indicates nonlinear changes in spatial patterns across temporal scales, so studies on temporal responses also need to be spatially explicit at narrow scales. This interaction also appears to be more complex than previously recognized: semester-averaged fine-root biomass was negatively correlated with soil water content in the preceding semester, but the relationship was restricted to residual Oxisols. To increase the accuracy of global carbon cycle models in the future, a critical complement to observations of ecosystem processes at regional and global scales will be quantifying these processes through multiple years and across the substantial edaphic gradients that typically exist within landscapes. Key words: aboveground biomass; Costa Rica, La Selva Biological Station; ecological scale; ecological stoichiometry; nitrogen; nutrient ratios; phosphorus; soil fertility gradients; soil moisture; soil nutrients.

ABSTRACT. Wetlands are restored and created in many areas of the world to mitigate problems of flooding, pollution and loss of wildlife habitat resulting from urbanization and agriculture. Consequently it [...]

The decline of available fossil fuel reserves has triggered worldwide efforts to develop alternative energy sources based on plant biomass. Detailed knowledge of the relations of metabolism and biomass accumulation can be expected to yield powerful novel tools to accelerate and enhance energy plant breeding programs. We used metabolic profiling in the model Arabidopsis to study the relation between biomass and metabolic composition using a recombinant inbred line (RIL) population. A highly significant canonical correlation (0.73) was observed, revealing a close link between biomass and a specific combination of metabolites. Dividing the entire data set into training and test sets resulted in a median correlation between predicted and true biomass of 0.58. The demonstrated high predictive power of metabolic composition for biomass features this composite measure as an excellent biomarker and opens new opportunities to enhance plant breeding specifically in the context of renewable resources. biomass | canonical correlation | metabolic profiling | recombinant inbred line population | biomarker

Patterns of resource availability and heterogeneity shape the composition, productivity, and dynamics of plant assemblages in a wide variety of terrestrial ecosystems. Despite this, the responses of plant assemblages to simultaneous changes in the availability and heterogeneity of more than a single resource are virtually unknown. To fill this gap, microcosms consisting of assemblages formed by Lolium perenne, Plantago lanceolata, Anthoxantum odoratum, Holcus lanatus, and Trifolium repens were grown in a factorial experiment with the following treatments: nutrient availability (NA), water availability (WA), spatial nutrient heterogeneity (NH), and temporal water heterogeneity (WH). Assemblages exhibited precise root foraging patterns in response to nutrient heterogeneity, which were modified by NA and WA. A series of two- and three-way interactions involving the four factors evaluated determined biomass production, the belowground:aboveground biomass ratio, the patterns of root biomass allocation with depth, and the relative contribution to aboveground biomass of Lolium and Anthoxanthum. In all cases, these interactions explained significant amounts of the variation found in the data. Our study demonstrates that considering the interactions between resource availability and heterogeneity allows for a refinement of predictions that can detectably reduce the error associated with extrapolating from single factor analyses. Key words: Anthoxantum odoratum; competition, global change; Holcus lanatus; Lolium perenne; microcosm; plant assemblages; Plantago lanceolata; resource availability; resource heterogeneity; Trifolium repens.

Most natural local systems exchange organisms with a regional pool of species through migration and dispersal. Such metacommunity processes of interconnected multispecies assemblages are likely to affect local dynamics of both species and processes. We present results from an artificial marine outdoor rock pool system in which we investigated the factors of (1) local grazer richness and composition, and (2) connectivity of local patches to a regional species pool, and their effects on algal biomass. Local species richness of six grazers was manipulated in both open and closed pools, which were embedded in a regional species pool containing all six grazers. Grazer richness showed significant net biodiversity effects on grazing in the closed, but not in the open, system. Grazer composition, on the other hand, showed significant effects on grazing in both open and closed systems, depending on which species were initially present. The two most efficient grazers were able to compensate for less efficient grazers in species mixtures, hence ensuring the function of grazing. The efficiency of top-down control of algal biomass in open systems thus depends on which particular species are lost. Further, differences in grazing between the open and closed system changed over time due to temporal dynamics in grazer composition. The results emphasize the importance of including system connectivity in experimental designs to allow an extrapolation of biodiversity ecosystem-functioning relationships to natural systems. Key words: compensation effect; composition; diversity; ecosystem function; grazing; marine; metacommunity; open system; rock pools; species identity.

Abstract: Wild rice (Zizania palustris L.) litter accumulation may inhibit plant growth and production both by physically suppressing seedling emergence and by nitrogen immobilization in fresh litter. This latter mechanism [...]

Abstract: Carbon (C) modeling and carbon dioxide (C[O.sub.2]) flux measurements in peatlands are dependent on the distribution and productivity of vegetation in a system with a high degree of spatial [...]

The invasive grass Microstegium vimineum grows in low light beneath the canopy of eastern forests in North America by reiteration of modules (phytomers) along a tiller. Basal phytomers are vegetative; terminal phytomers produce a raceme of chasmogamous (CH) spikelets plus an axillary raceme of cleistogamous (CL) spikelets. Additional subterminal phytomers with CL racemes mature basipetally. Allocation to culms, leaves, and CH and CL within phytomers was examined in relation to light conditions for a population in New Jersey, USA. Plants were reared in a greenhouse from seed families of parents in deep shade (2-8% full sun) or sunny, edge habitats. Primary tillers were subdivided into phytomers, dried, and weighed. Tillers from field habitats were similarly treated. For vegetative and subterminal phytomers, allocation to leaves and CH was greatest for the shady habitat. CL allocation decreased from terminal to reproductively immature subterminal phytomers. CH and CL mass was positively correlated with leaf mass, suggesting that reproduction is determined by available photosynthate. CH mass showed a genetic correlation with leaf mass. Developmental plasticity in modular allocation allows Microstegium to maximize fitness when conditions are favorable (e.g., high light along forest edges) by continual maturation of CL caryopses on axillary racemes. Key words: annual grass; chasmogamy; cleistogamy; invasive species; Microstegium vimineum; phytomers; Poaceae.

Canopy-forming plants and algae commonly contribute to spatial variation in habitat complexity for associated organisms and thereby create a biotic patchiness of communities. In this study, we tested for interaction effects between biotic habitat complexity and resource availability on net biomass production and species diversity of understory macroalgae by factorial field manipulations of light, nutrients, and algal canopy cover in a subtidal rocky-shore community. Presence of algal canopy cover and/or artificial shadings limited net biomass production and facilitated species diversity. Artificial shadings reduced light to levels similar to those under canopy cover, and net biomass production was significantly and positively correlated to light availability. Considering the comparable and dependent experimental effects from shadings and canopy cover, the results strongly suggest that canopy cover controlled net biomass production and species diversity by limiting light and thereby limiting resource availability for community production. Canopy cover also controlled experimental nutrient effects by preventing a significant increase in net biomass production from nutrient enrichment recorded in ambient light (no shading). Changes in species diversity were mediated by changes in species dominance patterns and species evenness, where canopy cover and shadings facilitated slow-growing crust-forming species and suppressed spatial dominance by Fucus vesiculosus, which was the main contributor to net production of algal biomass. The demonstrated impacts of biotic habitat complexity on biomass production and local diversity contribute significantly to understanding the importance of functionally important species and biodiversity for ecosystem processes. In particular, this study demonstrates how loss of a dominant species and decreased habitat complexity change the response of the remaining assembly to resource loading. This is of potential significance for marine conservation since resource loading often promotes low habitat complexity and canopy species are among the first groups lost in degraded aquatic systems. Key words: Baltic Sea; biodiversity; canopy cover; coastal ecosystems; ecosystem function; eutrophication; Fucus vesiculosus; macroalgae; marine diversity; subtidal ecology.

Evergreen broad-leaved tropical forests can have high rates of productivity and large accumulations of carbon in plant biomass and soils. They can therefore play an important role in the global carbon cycle, influencing atmospheric C[O.sub.2] concentrations if climate warms. We applied meta-analyses to published data to evaluate the apparent effects of temperature on carbon fluxes and storages in mature, moist tropical evergreen forest ecosystems. Among forests, litter production, tree growth, and belowground carbon allocation all increased significantly with site mean annual temperature (MAT); total net primary productivity (NPP) increased by an estimated 0.2-0.7 Mg C*[ha.sup.-1] *[yr.sup.-1]*[degrees][C.sup.-1]. Temperature had no discernible effect on the turnover rate of aboveground forest biomass, which averaged 0.014 [yr.sup.-1] among sites. Consistent with these findings, forest biomass increased with site MAT at a rate of 5-13 Mg C*[ha.sup].[degrees][C.sup.-1]. Despite greater productivity in warmer forests, soil organic matter accumulations decreased with site MAT, with a slope of -8 Mg C*[ha.sup.-1]*[degrees][C.sup.-1] indicating that decomposition rates of soil organic matter increased with MAT faster than did rates of NPP. Turnover rates of surface litter also increased with temperature among forests. We found no detectable effect of temperature on total carbon storage among moist tropical evergreen forests, but rather a shift in ecosystem structure, from low-biomass forests with relatively large accumulations of detritus in cooler sites, to large-biomass forests with relatively smaller detrital stocks in warmer locations. These results imply that, in a warmer climate, conservation of forest biomass will be critical to the maintenance of carbon stocks in moist tropical forests. Key words: belowground carbon allocation; carbon cycle; carbon turnover; decomposition; forest biomass; forest productivity; global warming; mean annual temperature; meta-analysis; net primary productivity; soil organic matter; tropical evergreen forests.

The effect of zooplankton species diversity on trophic structure and temporal stability of total zooplankton biomass is examined. Results reveal that increased zooplankton diversity significantly altered the size structure of algae, increasing the relative abundance of large, grazer-resistant algae.

The effects on the temporal dynamics of each of the endoparasitic nematodes Meloidogyne maritima, Heterodera arenaria and Pratylenchus penetrans by the presence of the other two species are investigated. Results reveal that Meloidogyne maritima is suppressed, both in abundance and in time of first appearance in the new root layer, by the addition of the endoparasitic nematodes Heterodera arenaria and Pratylenchus penetrans, while the other two are not affected.

Abstract -- Methods for rhenium extraction from plant materials were studied using model systems and the [.sup.186.Re] isotope. Conditions are described for the quantitative extraction of rhenium with acid and [...]

In this study we explored the effect of the physical environment and the availability of prey (biomass and taxonomic composition) on the patterns of prey capture and reproduction on five populations of Pinguicula moranensis (Lentibulariaceae) in areas ranging from pine-oak forests to desert scrublands. Environmental variation was summarized using principal factor analysis. Prey availability and prey capture increased toward the shadiest, most humid, and fertile population. The probability of reproduction and average bud production per population did not follow the same tendency because both fitness components peaked at the middle of the environmental gradient. These results suggest that the benefits derived from carnivory are maximized at sites fulfilling a trade-off between light, moisture, and prey availability. We also found that the taxonomic composition of both the available prey and that of the prey captured by plants varied among populations. The results also indicated that the prey captured by plants are not a random sample of prey available within populations. Overall, the results from this study revealed a marked amount of heterogeneity in the physical and biotic environment among the populations of P. moranensis, which has the potential to affect the outcome of the interaction between this carnivorous species and its prey. Key words: carnivorous habit; environmental heterogeneity; insectivorous plants; Lentibulariaceae; Pinguicula.

Abundance of invasive plants is often attributed to their ability ot outcompete native species. We compared resource acquisition and allocation of the invasive annual grass Bromus madritensis subsp. rubens with that of two native Mojave Desert annuals, Vulpia octoflora and Descurainia pinnata, in a glasshouse experiment. Each species was grown in monoculture at two densities and two levels of N availability to compare how these annuals capture resources and to understand their relative sensitivities to environmental change. During >4 mo of growth, Bromus used water more rapidly and had greater biomass and N content than the natives, partly because of its greater root-surface area and its exploitation of deep soils. Bromus also had greater N uptake, net assimilation and transpiration rates, and canopy area than Vulpia. Resource use by Bromus was less sensitive to changes in N availability or density than were the natives. The two native species in this study produced numerous small seeds that tended to remain dormant, thus ensuring escape of offspring from unfavorable germination conditions; Bromus produced fewer but larger seeds that readily germinated. Collectively, these traits give Bromus the potential to rapidly establish in diverse habitats of the Mojave Desert, thereby gaining an advantage over coexisting native species. Key words: Bromus madritensis subsp. rubens; desert ephemerals; introduced annual grasses; Mojave Desert; nitrogen uptake; plant biomass; Poaceae; root system; seed production; Vulpia octoflora; water uptake.

Ammophila breviligulata, American beachgrass, and Spartina patens, salt meadow hay, have been grazed by feral horses on the dunes of Assateague Island for hundreds of years; however, because of a significant increase in the horse population since the 1960s, overgrazing and dune erosion have become problems. Grazing was assessed on foredunes of four different morphologies along a 21-km stretch of the Maryland portion of the island using 17 exclosure plot pairs. In addition to decreased cover and biomass of the two species, plant structure was significantly affected by grazing. Leaf length and width, stem diameter, and stem density of A. breviligulata and stem diameter of S. patens were reduced in the grazed plots. Especially sensitive to grazing were reproductive characteristics. Percentage of plants in flower, height of flowering stems, and inflorescence length were all significantly reduced by grazing (nongrazed individuals measured). Species composition was not affected by horse accessibility. Key words: American beachgrass; Ammophila breviligulata; Assateague Island; dune morphology; feral horses; grazing; Poaceae; sand dune; Spartina patens.

We examined the allometry and mechanical properties of the peduncles of Hieracium pilosella and other species in the Asteraceae (H. aurantiacum, Taraxicum officinale, Tragopogon pratensi) to evaluate the hypothesis that tapered, tubular, and non-septate peduncles optimize the trade-offs among stem biomass allocation, elevating flowers and thus their wind-dispersed fruits, and the requirement for a factor of safety against mechanical failure. This hypothesis was evaluated by comparing peduncle morphometry (e.g., biomass M, floral biomass [M.sub.s] and length L) and mechanical properties (e.g., bending rigidity EI) for populations growing in windy and windsheltered sites as well as transplants between sites. Regardless of ambient wind speeds, [M.sub.s] [alpha] [L.sup.4/3] and EI [alpha] [L.sup.11/4) [alpha] [M.sub.s.sup.(5/3)], whereas [M.sub.f]/[M.sub.s] [alpha] [L.sup.-1.15], i.e., peduncles disproportionately increase in their biomass as they increase in length, but mechanically support a disproportionately smaller floral biomass relative to their biomass. Calculations show that the tall peduncles from wind-sheltered sites have a larger fruit dispersal range and a lower factor of safety than the shorter peduncles produced in open sites. These and other observations are interpreted to indicate that tubular peduncles enhance relative fitness in terms of propagule dispersal (but not propagule number per stein) while maintaining a sufficient factor of safety against mechanical failure. Key words: allometry; Asteraceae; Brazier buckling; flexural stiffness; fruit dispcrsal; Hieracium pilosella; plant biomechanics; winding loading.

Two autonomous robotic profiling floats deployed in the subarctic North Pacific on 10 April 2001 provided direct records of carbon biomass variability from surface to 1000 meters below surface at daily and diurnal time scales. Eight months of real-time data documented the marine biological response to natural events, including hydrographic changes, multiple storms, and the April 2001 dust event. High-frequency observations of upper ocean particulate organic carbon variability show a near doubling of biomass in the mixed layer over a 2-week period after the passage of a cloud of Gobi desert dust. The temporal evolution of particulate organic carbon enhancement and an increase in chlorophyll use efficiency after the dust storm suggest a biotic response to a natural iron fertilization by the dust., Marine phytoplankton biomass is replaced, on average, once every 1 to 2 weeks (1-3). Carbon products of photosynthesis (4), i.e., particulate organic carbon (POC), particulate inorganic carbon (PIC), and dissolved [...]

Current technologies for measuring plant water status are limited, while recently remote sensing techniques for estimating N status have increased with limited research on the interaction between the two stresses. Because plant water status methods are time-consuming and require numerous observations to characterize a field, managers could benefit from remote sensing techniques to assist in irrigation and N management decisions. A 2-yr experiment was initiated to determine specific wavelengths and/or combinations of wavelengths indicative of water stress and N deficiencies, and to evaluate these wavelengths for estimating in-season biomass and corn (Zea mays L.) grain yield. The experiment was a split-plot design with three replications. The treatment structure had five N rates (0, 45, 90, 134, and 269 kg N [ha.sup.-1]) and three water treatments [dryland, 0.5 evapotranspiration (ET), and full ET]. Canopy spectral radiance measurements (350-2500 nm) were taken at various growth stages (V6-V7, V13-V16, and V14-R1). Specific wavelengths for estimating crop biomass, N concentration, grain yield, and chlorophyll meter readings changed with growth stage and sampling date. Changes in total N and biomass in the presence of a water stress were estimated using near-infrared (NIR) reflectance and the water absorption bands. Reflectance in the green and NIR regions were used to estimate total N and biomass without water stress. Reflectance at 510, 705, and 1135 nm were found for estimating chlorophyll meter readings regardless of year or sampling date., AVAILABLE WATER is one of the most limiting factors in crop production; while in non-leguminous crops, low available soil N can be an additional yield reduction factor. Denmead and Shaw [...]

Allometric equations are commonly utilized to estimate plant biomass from measured species attributes such as height, canopy width, and root collar diameters. These same attributes are also commonly measured as [...]

1 Submergence of coastal wetlands in Louisiana is currently rapid and widespread. A number of factors contribute to this loss of habitat, including the activities of herbivores. The objective of this study was to examine the effects of large mammals, predominantly nutria and wild boar, on processes controlling soil elevation in coastal marshes. 2 Effects of herbivores on soil and vegetation were assessed by the use of paired fenced and unfenced plots over two successive growing seasons. Above-ground biomass, litter production, changes in soil elevation, vertical soil accretion, shallow subsidence, below-ground production of roots and rhizomes, the thickness of the root zone, soil bulk density, and soil organic matter were measured. 3 Above-ground biomass, below-ground production, soil elevation and the expansion of the root zone decreased due to herbivore activity. Litter production, the rate of soil surface accretion and shallow soil subsidence were all higher in grazed compared to ungrazed plots, while soil organic matter and bulk density did not differ significantly between treatments. 4 The results indicate that herbivores can have a negative effect on soil building processes, primarily by reducing below-ground production and expansion of the root zone. Where natural rates of mineral sediment deposition are high, coastal marshes are expected to persist, despite herbivore activities. However, where sediment inputs are substantially less, herbivores may lead to destruction of habitat. Keywords: coastal wetlands, habitat destruction, herbivory, soil development, wetland loss

A study was conducted to characterize a couple of cellulase components from a marine hyperthermophile, Thermotoga neopolitana. The molecular masses of the enzymes were obtained using sodium dodecyl sulfate while polysaccharase activity was determined through the release of reducing sugars by the Somogyi-Nelson technique. Results indicated that the cellulase components may be determined as a polycistronic mRNA. Findings also suggested cellobiose correlated with cellulase production in Trichoderma reesei and in Thermomonospora fusca.

1 A dwarf shrub heath in subarctic Sweden was subjected to factorial manipulation of air temperature, water and nutrient supply for 5 years. The responses of the vegetation to the perturbations were then assessed by point intercept (quadrat) analysis followed by determination of above-ground biomass. 2 Nineteen vascular and 23 non-vascular species (or species groups) were recorded and the most dramatic response was that of the grass Calamagrostis lapponica to nutrient addition, with abundance being stimulated by a factor of more than 18 compared with plots not subjected to nutrient addition. Calamagrostis lapponica did not show any significant responses to temperature or water alone but there was a synergistic interaction between all three variables. 3 The abundance of the dominant dwarf shrubs (Empetrum hermaphroditum, Vaccinium vitis-idaea, V. myrtillus and V. uliginosum) was unaffected by the perturbations but elevated temperature stimulated the biomass of V. uliginosum by 125% and total shrub biomass by 16%. The low ratio of current year's growth to standing biomass may have concealed other responses of the dwarf shrub group to the perturbations. 4 The response of the non-vascular flora to the perturbations was either neutral or negative, with lichens showing the most dramatic responses. Lichen biomass on temperature- and nutrient-amended plots was 56% and 18%, respectively, of that on unperturbed plots. Nutrients also exerted a negative effect on the biomass of bryophytes, and the combined biomass of lichens and bryophytes on nutrient-treated plots was almost a third of that on plots which did not receive additional nutrients. 5 Total above-ground biomass was not affected by the perturbations but the total number of interceptions determined by point quadrat analysis was greater on the elevated temperature and nutrient-treated plots. Point quadrat analysis also revealed an accumulation of litter and standing dead material in response to the nutrient and temperature perturbations, both singly and in combination, suggesting a faster turnover of plant material. 6 Both temperature and nutrients increased canopy height and also interacted synergistically such that together they resulted in a mean canopy height of 14.9cm compared with 8.0 cm in plots subjected to neither perturbation. 7 Nutrient addition lowered species richness by 17.7%, mainly through its impact on the mosses and lichens. 8 In general, nutrient addition elicited the greatest response, followed by temperature, with water exerting little measurable influence. There were a number of important interactions that were often synergistic, and some involved water. 9 Species' responses were highly individualistic and changes in the community were mediated through the response of a small number of key species already present in the community, with no invasion of new species. In the short term at least, floristic diversity may decline as understorey species become less abundant and immigration by new species is inhibited by the dominance of clonal angiosperms. Keywords: biomass, nutrients, species abundance, temperature, water

1 Canopy-level C[O.sub.2] exchange and biomass were measured monthly for 9 consecutive months during 1990 on grazed and non-grazed portions of a Danish salt marsh dominated by Spartina anglica. The empirical measurements were used to calibrate a model of canopy photosynthesis and soil respiration that was subsequently integrated to provide estimates of annual net ecosystem production (NEP). 2 Standing total and green biomass on the non-grazed site reached maxima during September of 1.9 [+ or -] 0.2 and 1.1 [+ or -] 0.2 kgm-2 ([+ or -] 1 SD, n = 3), respectively. Corresponding maxima (0.8 [+ or -] 0.1 and 0.5 [+ or -] 0.05 kg [m.sup.-2]), were achieved during July at the grazed site. 3 Sediment organic matter as a percentage of dry weight was 31.6% and 5% at the non-grazed and grazed sites, respectively. Accounting for the higher sediment bulk density at the grazed site meant that concentrations of organic carbon were 0.027 and 0.021 g [cm.sup.-3] at non-grazed and grazed sites, respectively. Thus, the fraction of NEP removed by grazing animals significantly reduced the accumulation of sediment organic matter. 4 Estimate of NEP varied between 17 and 38 mol [m.sup.-2] [year.sup.-1] of carbon at the grazed site and between 5 and 38 mol [m.sup.-2] [year.sup.-1] at the non-grazed site, depending on assumptions about canopy geometry. Soil respiration, 36 mol [m.sup.-2] [year.sup.-1], did not differ between sites. Canopy respiration was less (21 mol [m.sup.-2] [year.sup.-1]) at the grazed site than at the non-grazed site (28 mol [m.sup.-2] [year.sup.-1]), and accounted for 22-29% and 2841% of gross photosynthesis at grazed and non-grazed sites, respectively. The decrease in canopy respiration compensated the grazed canopy for losses to herbivores. 5 A canopy photosynthesis model was used to calculate a theoretical envelope of canopy biomass, termed the production window, inside of which NEP is positive and outside of which NEP is negative. The production window is bisected by the optimum canopy biomass, which is the theoretical biomass at which NEP is maximized. The seasonality of NEP is determined by the trajectory of actual canopy biomass through the production window. It was shown that canopy biomass on the grazed site was close to the theoretical optimum biomass late in the season, while the non-grazed canopy biomass was supraoptimal. Keywords: grazing, model, net ecosystem production, photosynthesis, respiration

1 Acer mono is one of the earliest germinating species in hardwood forests of northern Japan. To evaluate the advantage of early germination for the seedling establishment, differences in the temporal pattern of leaf development between the seedlings and overstorey trees were investigated, together with the timing of dry mass gain and allocation, survival and mortality agents of seedlings. These traits were contrasted at four sites with different types of foliage phenology in the overstorey trees (FU-1 and FU-2, forest understorey in which overstorey trees unfolded and shed the leaves as a flush and succeedingly, respectively; SG, small gaps; and FE, forest edge). 2 Seasonal growth patterns of the seedlings were greatly affected by the differences in the coupling of leaf development between the seedlings and the overstorey trees. For early germinating cohorts of Acer mono, 79, 61, 50 and 53% of annual dry mass gain occurred within 2 months of germination, in FU-1, FU-2, SG and FE, respectively. After this point (canopy closure) mass increment decreased abruptly in both FU sites, but continued to increase in both SG and FE. Seedling mass, however, increased after September again in FU-2 but not in FU-1, mainly due to earlier leaf shedding of the canopy trees in FU-2. 3 After canopy closure, leaf mass ratio was greatest in FU-1 where light was most limited, but lowest in FE. In contrast, root mass ratio was greatest in FE but lowest in FU-1 where soil moisture was most abundant. These traits might lead to the optimization of growth by making all resources equally limiting even after canopy closure in forest understorey. 4 Higher seedling survival resulting from early germination was observed in all four sites, since predators and pathogens selectively attacked late germinating individuals. The advantage of early germination was greater in both FU-1 and FU-2 than in FE, mainly due to large differences in available light for early vs. late germinating individuals in both FU sites compared with the FE site. 5 These observations suggest that phenological traits of A. mono such as rapid germination in early spring and earlier deployment of leaves compared with overstorey trees has been selected to maximize annual mass gain and survival in understorey habitats of deciduous broad-leaved forests. Keywords: causes of mortality, biomass allocation, RGR, light, shade avoidance

Gynodioecy is a breeding system in which hermaphrodites coexist with male steriles. Theoretical models predict that without any compensation in female fitness male steriles will disappear from a population due to their reproductive disadvantage. In the present study I investigated whether male-sterile (MS), partially male-sterile (IN), and hermaphroditic (H) plants of Plantago lanceolata differed in reproductive growth and allocation. Offspring of three interpopulation crosses segregating all three sex morphs were grown under nitrogen-limited conditions in a growth chamber. Independent of the genetic background MS plants attained a higher vegetative and reproductive dry mass and a higher reproductive output than H plants, whereas IN plants had intermediate values. When corrected for the mass of the pollen, the dry mass differences between the sex morphs were much reduced but still present. However, when whole-plant allocation was expressed on the basis of nitrogen, the differences between the sex morphs disappeared. Thus the sex morphs took up similar amounts of nitrogen but distributed them differently. The MS and IN plants used the nitrogen saved by not producing pollen for additional vegetative as well as reproductive growth. The data presented in this study suggest that resource compensation is one of the main mechanisms responsible for the maintenance of MS and IN plants in gynodioecious P. lanceolata. Key words: biomass allocation; compensation; gynodioecy; male sterility; Plantaginaceae; Plantago lanceolata; reproductive growth.