Carbon Stores (carbon + store)

Distribution by Scientific Domains
Life Sciences100%

Selected Abstracts

Comparing tropical forest tree size distributions with the predictions of metabolic ecology and equilibrium models

ECOLOGY LETTERS, Issue 5 2006
Helene C. Muller-Landau
Abstract Tropical forests vary substantially in the densities of trees of different sizes and thus in above-ground biomass and carbon stores. However, these tree size distributions show fundamental similarities suggestive of underlying general principles. The theory of metabolic ecology predicts that tree abundances will scale as the ,2 power of diameter. Demographic equilibrium theory explains tree abundances in terms of the scaling of growth and mortality. We use demographic equilibrium theory to derive analytic predictions for tree size distributions corresponding to different growth and mortality functions. We test both sets of predictions using data from 14 large-scale tropical forest plots encompassing censuses of 473 ha and > 2 million trees. The data are uniformly inconsistent with the predictions of metabolic ecology. In most forests, size distributions are much closer to the predictions of demographic equilibrium, and thus, intersite variation in size distributions is explained partly by intersite variation in growth and mortality. [source]

Cell wall hemicelluloses as mobile carbon stores in non-reproductive plant tissues

FUNCTIONAL ECOLOGY, Issue 5 2007
G. HOCH
Summary 1As essential compounds of plant cell walls, hemicelluloses account for about a quarter of all plant biomass worldwide. 2In seed cotyledons and endosperm of species from several plant families, hemicelluloses are used as mobile carbon reserves. Whether cell wall hemicelluloses of non-reproductive plant tissue are multifunctional molecules, which can also serve as carbon sources during periods of enhanced carbon demand, is still equivocal. 3This review summarizes the current understanding of a possible reserve function of hemicelluloses. Although several descriptive and experimental studies suggested at least partial mobility of cell wall polysaccharides in mature, non-reproductive plant tissues, there is still a need for a broad-scale, ecophysiological exploration of the actual nature of hemicelluloses beyond their structural function. 4The chemical heterogeneity of hemicelluloses may be the major problem for precise quantitative analyses on a large, comparative scale. 5Because of the abundant distribution of hemicelluloses in plants, the existence of a significant mobile carbohydrate pool in cell walls of non-reproductive organs would shed rather new light on plant carbon relations in a source-sink context. 6Consequently, a reserve function of hemicelluloses questions the conventional division of cell compounds into structural (i.e. immobile) and non-structural (i.e. mobile) compounds. [source]

Model,data synthesis in terrestrial carbon observation: methods, data requirements and data uncertainty specifications

GLOBAL CHANGE BIOLOGY, Issue 3 2005
M. R. Raupach
Systematic, operational, long-term observations of the terrestrial carbon cycle (including its interactions with water, energy and nutrient cycles and ecosystem dynamics) are important for the prediction and management of climate, water resources, food resources, biodiversity and desertification. To contribute to these goals, a terrestrial carbon observing system requires the synthesis of several kinds of observation into terrestrial biosphere models encompassing the coupled cycles of carbon, water, energy and nutrients. Relevant observations include atmospheric composition (concentrations of CO2 and other gases); remote sensing; flux and process measurements from intensive study sites; in situ vegetation and soil monitoring; weather, climate and hydrological data; and contemporary and historical data on land use, land use change and disturbance (grazing, harvest, clearing, fire). A review of model,data synthesis tools for terrestrial carbon observation identifies ,nonsequential' and ,sequential' approaches as major categories, differing according to whether data are treated all at once or sequentially. The structure underlying both approaches is reviewed, highlighting several basic commonalities in formalism and data requirements. An essential commonality is that for all model,data synthesis problems, both nonsequential and sequential, data uncertainties are as important as data values themselves and have a comparable role in determining the outcome. Given the importance of data uncertainties, there is an urgent need for soundly based uncertainty characterizations for the main kinds of data used in terrestrial carbon observation. The first requirement is a specification of the main properties of the error covariance matrix. As a step towards this goal, semi-quantitative estimates are made of the main properties of the error covariance matrix for four kinds of data essential for terrestrial carbon observation: remote sensing of land surface properties, atmospheric composition measurements, direct flux measurements, and measurements of carbon stores. [source]

Height-related growth declines in ponderosa pine are not due to carbon limitation

PLANT CELL & ENVIRONMENT, Issue 1 2009
ANNA SALA
ABSTRACT Decreased gas exchange as trees grow tall has been proposed to explain age-related growth declines in trees. We examined changes of mobile carbon stores (starch, sugars and lipids) with tree height in ponderosa pine (Pinus ponderosa) at two sites differing in water availability, and tested the following hypotheses: (1) carbon supply does not become increasingly limited as trees grow tall; rather, the concentration of mobile carbon compounds increases with tree height reflecting greater reductions of carbon sink activities relative to carbon assimilation; and (2) increases of stored mobile carbon compounds with tree height are greater in drier sites. Height-related growth reductions were associated with significant increases of non-structural carbohydrates (NSC) and lipid concentrations in all tissues in the upper canopy and of NSC in the bole. Lipid concentrations in the bole decreased with tree height, but such decrease is not necessarily inconsistent with non-limiting carbon supply in tall trees. Furthermore, we found stronger increases of mobile carbon stores with tree height at the dry site relative to the moist site. Our results provide first direct evidence that carbon supply does not limit growth in tall trees and that decreases of water availability might negatively impact growth processes more than net-photosynthesis. [source]

Interspecific and Inter-site Variation in Wood Specific Gravity of Tropical Trees

BIOTROPICA, Issue 1 2004
Article first published online: 15 MAR 200, Helene C. Muller-Landau
ABSTRACT Variation in climate and soils results in inter-site differences in the assemblages of tree life history strategies within a community, which has important implications for ecosystem structure and dynamics. I investigated interspecific and inter-site variation in wood specific gravity,an easily measured indicator of tree life history strategy,in four Neotropical forests and analyzed its correlates. Mean wood specific gravity (oven-dry weight divided by fresh volume, sometimes also referred to as wood density in the literature) differed significantly among sites, varying inversely with soil fertility and independently of rainfall, seasonality, and temperature. Mean wood specific gravity values were much higher at Kilometer 41, Manaus, Brazil, where soils are extremely poor, than at Cocha Cashu, Peru, Barro Colorado Island, Panama, or La Selva, Costa Rica, where soils are better and mortality rates of trees are higher. Within sites, wood specific gravity varied widely among species. On Barro Colorado Island, among-species variation was significantly, albeit weakly, negatively correlated with sapling and tree mortality and relative growth rates. Altogether, the results suggest that the distribution of tree life history strategies in a community varies substantially among sites, with important consequences for community and ecosystem properties such as aboveground carbon stores. RESUMEN La variación climática y edáfica da lugar a diferencias entre sitios con respecto a los ensambles de las estrategias de historia de vida de los árboles de una comunidad, lo cual tiene consecuencias importantes para la estructura y la dinámica del ecosistema. Investigué la variación interespecífica y espacial en la gravedad específica de la Madera,un indicador de fácil medición de la estrategia de historia de vida de los árboles,en cuatro bosques neotropicales y analizé sus factores asociados. La gravedad especifica media de la madera (el peso seco dividido por el volumen fresco, frecuentemente llamado "densidad de la madera" en la literatura ecológica) fue significativamente diferente entre sitios, variando inversamente con la fertilidad del suelo, e independientemence de la precipitación, la estacionalidad, y la temperatura. La gravedad especifica media de la madera fue mucho más alta en Kilómetro 41, Manaus, Brasil, donde los suelos son extremadamente pobres, en comparación con Cocha Cashu, Perú, Barro Colorado, Panamá, o La Selva, Costa Rica, donde los suelos son mejores y las tasas de mortalidad de los árboles son más altas. Dentro de los sitios, la gravedad especifica de la madera varió extensamente entre especies. En Barro Colorado, la variación entre especies estuvo correlacionada negativamente, aunque sólo débilmente, con las tasas de mortalidad y de crecimiento relativo de los árboles juveniles y adultos. En conjunto, los resultados sugieren que la distribución de las estrategias de historia de vida de los árboles en una comunidad varía sustancialmente entre sitios, con consecuencias importantes para características comunitarias y del ecosistema tales como las reservas de carbono. [source]