Harold Mooney

The maximum water content, the relative water content and the water depletion of wood were studied in 41 species of a tropical deciduous forest during the dry season. Ther is a significant correlation between the maximum water content and the specific wood weight. Also, water de pletion per wood weight is significantly correlated with the specific wood weight. On a wood volume basis, deciduous trees unse more stem water than water-storing trees. These data are discussed with respect to the dominance of life forms in this forest type

Abs t rac t Global atmospheric CO 2 is increasing at a rate of 1.5-2 ppm per year and is predicted to double by the end of the next century. Understanding how terrestrial ecosystems will respond in this changing environment is an important goal of current research. Here we present results from a field study of elevated CO 2 in a California annual grassland. Elevated CO 2 led to lower leaf-level stomatal conductance and transpiration (approximately 50%) and higher mid-day leaf water potentials (30-35%) in the most abundant species of the grassland, Avena barbata Brot. Higher CO 2 concentrations also resulted in greater midday photosynthetic rates (70% on average). The effects of CO 2 on stomatal conductance and leaf water potential decreased towards the end of the growing season, when Avena began to show signs of senescence. Water-use efficiency was approximately doubled in elevated CO 2, as estimated by instantaneous gas-exchange measurements and seasonal carbon isotope discriminati...

A global data set of root biomass, rooting profiles, and nutrient concentrations in roots was compiled from the primary literature and used to study distributions of root properties. This data set consists of ninety estimates of live and total fine root biomass associated with Table 1 published in Jackson et al. (1977) (Jackson, R. B., H. A. Mooney, and E.-D. Schulze. 1997. A global budget for fine root biomass, surface area, and nutrient contents. Proceedings of the National Academy of Sciences, U.S.A. 94:7362-7366). Expanded data on rooting profiles and nutrients are available in other data sets; however, these data represent a unique tabulation of fine root measurements. Understanding and predicting ecosystem functioning (e.g., carbon and water fluxes) and the role of soils in carbon storage requires an accurate assessment of plant rooting distributions. Here, in a comprehensive literature synthesis, we analyze rooting patterns for terrestrial biomes and compare distributions for various plant functional groups. The initial data set (Jackson et al. 1996) was expanded to examine distributions of root budgets (Jackson et al. 1997). Measurements were selected from over 300 field studies. Results from the analysis showed that calculated root surface area is almost always greater than leaf area, more than an order of magnitude so in grasslands. The average C:N:P ratio in living fine roots is 450:11:1, and global fine root carbon is more than 5 percent of the magnitude of all carbon contained in the atmosphere. Assuming conservatively that fine roots turn over once per year, they represent 33 percent of global annual net primary productivity. A PDF copy of the Jackson et al (1996) paper is available at http://www.biology.duke.edu/jackson/oecol96c.pdf, and a PDF copy of the Jackson et al. (1997) paper is available on-line at http://www.biology.duke.edu/jackson/PNAS97.htm. This data set has been expanded and updated over the years to estimate root turnover rates (data for approximately 341 site-vegetation combinations for 188 site from 152 papers in Gill and Jackson 2000); studies of root nutrient concentrations (data for approximately 372 site-pit-depths from 57 papers in Gordon and Jackson 2000); and rooting depth (data for approximately 298 sites with 565 profiles in Schenk and Jackson 2002). The three recent papers include most of the data contained in the initial root data set; however, some observations may have been excluded because of more stringent selection criteria. Many of the source papers provided data for the three recent rooting papers and users are encouraged to review the three recent data sets. The file described at http://www-eosdis.ornl.gov/VEGETATION/guides/fine_roots_biomass.html that provides estimates of both live and total fine root biomass for approximately 100 sites is unique to the collection of four data sets of root characteristics developed by Jackson and his collaborators. The Oak Ridge National Laboratory Distributed Active Archive Center (ORNL DAAC) for Biogeochemistry Dynamics organized and formatted these data for long-term archive. Spreadsheet files are stored as ASCII tab-delimited files. Missing values are represented by -999

ABSTRACT The El Nifio-Southern Oscillation event of 1982-83 was associated with severe winter weather in California, including increased snow accumulations in the Sierra Nevada relative to 1984. We examined the ratio of 1983 needle length to 1984 needle length in two ...

Transpiration rates were measured in situ on native plants growing at elevations from 5,000 to over 12,000 ft in the White Mountains of California. These elevations include vegetation zones from the desert scrub to the alpine tundra. Rates were also measured on plants originating from these elevations but growing in a common environment. The highest water loss rates were found in the summer deciduous shrubs which included desert species-the lowest rates in evergreen conifers.

Carbon dioxide profiles were measured in four high- elevation habitats in the White Mountains of California. The CO2 content was found to change little between day and night and at differ- ent levels above the ground within an alpine fell field and carex dry meadow (3,870 m elevation). By contrast, relatively large concentra- tion changes were found with time and height above the ground at the edge of a subalpine forest and a subalpine carex meadow (3,094 m). The possibility of short-term recycling of the abundant carbon dioxide of soil origin by the low growing meadow vegetation is proposed. tration near ground level in a forest may be more than twice the normal atmospheric content. He concluded that this increased supply of CO2 is an important consideration for the survival of the shade flora. Fuller (1948) measured carbon dioxide concentration gra- dients in forests and grasslands and found concentrations of 730 to 1,810 ppm CO2 immediately above the ground surface. He also concluded that the high levels of CO2 were significant to the produc- tivity of forest plants. Sparling and Alt (1966) found stratification of carbon dioxide concentrations above a forest floor but only when wind flow was relatively low. Even slight breezes disrupted the con- centration gradients and they concluded that it is doubtful if forest floor plants are exposed to CO2 concentrations significantly greater than the normal atmospheric concentrations. Root biomass is proportionately high in alpine ecosystems. During the long, approximately nine-month dormant season, low temperatures reduce respiratory activity to low levels. During the summer growing season root respiration at night, when quite low temperatures prevail,

In mahogany, many of the problems confronting tropical rain forests worldwide are seen in microcosm, yet in some important ways the genus is unique. It is unusual among well-known tropical timbers in having poorly known ecological requirements. Most tropical timbers have low unit value and are interchangeable. Mahogany has thrice their value and is a high-quality cabinet wood with unique properties. It is unusual among cabinet woods in being a strong light demander and fast grower that does well in plantations. Thus, mahogany holds great promise for the future. Attempts to control its trade suffer familiar problems of misinformation and missing information. The natural range is vast, and, although the species is not on the verge of extinction, genetic erosion has been alleged. Sustainable exploitation is hampered by inadequate knowledge of its regeneration ecology and the all too common practical problems of rule enforcement. 1. Mahogany: Tree of the Future

In house dust acarofauna, the following mites are typically to be found: More than 80% are house dust mites, represented by the species Dermatophagoides pteronyssinus, Dermatophagoides farinae, Dermatophagoides microceras, and Euroglyphus maynei. Ten percent are glistening mites of the genus Tarsonemus, and 5-8 % belong to the genus complex of storage mites that are mainly spread in grain, straw, and hay (Acarus, Glycyphagus/Lepidoglyphus, Tyrophagus, Cheyletus, Tydeus, and another Tarsonemus species). The combination of species can be subject to great variations, e.g. Glycyphagus can be dominating in homes with a very humid indoor climate.

Les feuilles de 3 arbustes de chapanal sont analysees afin de comparer leurs couts de maintenance et de croissance respectifs determines par l'analyse des voies metaboliques d'Heteromeles arbutifolia (feuillage persistant) et Diplacus aurantiacus, Lepechinia calycina (feuillage caduque). Les valeurs obtenues sont comparees a celles publiees anterieurement et obtenues par la methode des echanges gazeux

... The distribution and evolution of climbing plants. by AH Gentry. ... In pluvial forests hemiepiphytic climbers of Melastomataceae, Guttiferae and Araceae take over from Bignoniaceae and Leguminosae. In montane forests, Asteraceae become the predominant climbers. ...