Bacterial and fungal counts, mycelial growth, microbial evolution of Co2, and substrate moisture and temperature in bags with litter of either mulberry, redbud, white oak, loblolly pine, or beech were measured biweekly over the period November 1960—November 1961 in oak, pine, and maple stands at Oak Ridge, Tennessee. Serial dilution plate method and closed—box technique were effective for measuring microbial densities and microbial respiration respectively. Microbial densities, microbial respiration, and annual weight losses of species declined in the order mulberry, redbud, white oak, pine, beech, ad were significantly positively correlated. Stand effects were not significant possibly due to partial exclusion of stand effects in the bags. Microbial densities and moisture conditions of the various leaf species converged with time and their short—term fluctuations decreased indicating homogenation of substrate and stabilization of microbial populations. Microbial respiration was controlled in decreasing order by temperature (T), bacterial density (B), moisture (M/D), and the number of weeks (W) since leaf drop. An effective model for prediction of microbial respiration (C) is C = 46.5 + 3.2T + 26.9 M/D + 11.4 log B — 0.6W. Mean CO2 production was 0.17 liters/g substrate decomposed. Production was higher for rapidly decomposing leaf species dominated by relatively inefficient bacterial flora than for slowly decaying litter with predominantly more efficient fungi. Loss of weight and respiration were highly correlated with a microbial population estimate, combining bacterial and fungal counts.
Periodic measurement of CO2 evolution from various biotopes reveals a daily cycle in soil respiration with a predawn minimum and an afternoon maximum that parallels the daily temperature cycle. A second maximum occasionally occurs between midnight and dawn when soil temperatures exceed temperature of the surface air. This predawn flush may result from thermal convection of CO2—rich subsurface air to the surface. The time of measurement must be considered for comparisons of rates of CO2 evolution from different sites, and measurements should be made over a 24—hr period for estimates of daily CO2 evolution.
JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecology.Abstract. Evolution of CO2 from the forest floor measured by the inverted-box method was related to moisture, temperature, and age of the litter, and to CO2 evolution from oak leaves in litter bags measured by the closed-box method. Rates of CO2 evolution measured by the inverted-and closed-box methods did not differ significantly (P> 0.2). Respiration rates from bagged oak leaves were significantly correlated (P<0.01) with respiration rates from the floor in an oak stand, but not with rates in pine and maple stands. In the oak stand, rates of respiration from the forest floor and from litter bags were highly significantly correlated (P < 0.01) with temperature, litter age, and moisture in decreasing order of influence. The influence of litter age was much higher in litter bags than in the forest floor. The variability of temperature and moisture in the forest floor was lower than in litter bags. Rates of respiration from the floors of pine, oak, and maple stands were not significantly different (P > 0.05). REPORTS Ecology, Vol. 47, No. 3 Feh6r, D. 1933. Mikrobiologie des Waldbodens. Springer, Berlin. 272 p. LundegArdh, H. 1927. Carbon dioxide evolution of soil and crop growth. Soil Sci. 23: 417-450. Wallis, G. W., and S. A. Wilde. 1957. A rapid method for the determination of carbon dioxide evolved from forest soils. Ecology 38: 359-361. Witkamp, M. 1966. Decomposition of leaf litter in relation to environmental conditions, microflora, and microbial respiration. Ecology 47: 194-201. Witkamp, M., and J. S. Olson. 1963. Breakdown of confined and nonconfined oak litter. Oikos 14: 138-147. Witkamp, M., and J. van der Drift. 1961. Breakdown of forest litter in relation to environmental factors. Plant and Soil 15: 295-311. Abstract. Six main types of soil and terrain were recognized on the Las Bela coastal plain of West Pakistan. Usually one or two species of plants-indicator species-predominated on each of the terrain types. Other plants grew in close association with the indicator species but could not be classified as indicators because their locale was not restricted to a specific landform. The identification of indicator species on aerial photographs helped to determine boundaries for the landforms.
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