Biomass estimates direct methods

Microscopic counting is still the most direct method of estimating the amount of microbial biomass in soil but is technically difficult and completely unsuitable for routine use. Thin films are prepared from an agar-soil suspension, are mounted on microscope slides, and then are treated with an appropriate stain. Phenolic aniline blue is often used as it stains protein and is thus considered to give an estimate of the entire population. The numbers... 

Indirect methods, based on allometric inference, from measurements of the diameter at breast height (DBH) and the height of the trees to obtain wood volumes, is the main method adopted to estimate biomass in the Amazon. Forest biomass estimates are made through regression analysis, where several fitting curves are tested to obtain an ideal model that can be applied to the trees. These models are calibrated by direct weighing of the biomass from a subsample of trees (see for example, Jordan and Uhl 1978, Higuchi et al. 1994, Brown et al. 1995), and could also include other compartments besides trees, such as vines or understory. Indirect methods are broadly adopted in the forestry industry to evaluate the volume of commercial wood. 

Estimation of the nutrient content of the biomass by the fumigation technique is a more direct method, but still assumes that the flushes of nutrients from the killed biomass behave in a similar way to those from the organisms used to estimate the k-factors. At the time of writing there have been comparatively few estimates using the fumigation technique and the majority of these have been on biomass-N. 

Measurement of soil activity there are a number of laboratory methods which are suitable for measuring the biological activity of the soil. In principle, a distinction is made between direct and indirect methods for the determination of soil activity. The biomass in the soil, for example, can be estimated by counting the individual organisms in the soil, or the measurement of respiration after the addition of a nutrient in excess can provide an indication of active biomass. Moreover, in determinations of activity, a distinction is made between actual and potential activity. Actual activity values are values measured at the time that the sample was taken. Determinations of potential activity, on the other hand, show the level of performance that microorganisms are capable of under optimum experimental conditions, after the addition of a nutrient substrate and prolonged incubation. 

Estimation methods for Amazonian forest biomass direct versus indirect methods... 

Forest biomass in the Amazon has been estimated through direct and indirect methods. Independent of the method used, one should take into consideration that all components of forest biomass must be quantified. Besides the trees that are the main component of the forest, other components to be included are vines Gianas), understory plants, litter, roots, palms, etc. 

Direct/indirect methods refers to the estimate of biomass by destructive harvest, supplemented for branches and trunks < 10 cm in diameter by indirect methods of line-intersect sampling. Used to estimate the biomass in areas of felled forest. 

Direct estimates of biomass have been attempted by analyzing for molecules or elements that must be of microbiological origin, such as total organic carbon, organic nitrogen, protein, DNA, or ATP. Standard methods are available for all these determinations but their application to autotrophs is complicated by the low cell counts and by interference from biooxidized material. Recently, immunological methods have received attention 4). 

A direct estimation of the biomass present maybe made by determining the dry weight of a sample. In breweries, however, less direct but more rapid methods are used. Examples of such techniques are the measurement of the packed cell volume of a sample after centrifugation under precisely controlled conditions, determination of wet weight after filtration, and the measurement of the optical opacity of a sample by turbidimetry or spectrophotometry. Alternatively, where pressed yeast or yeast slurry of consistent quality are available, the weight or volume of such samples may be measured. The accuracy of all of these procedures is impaired where non-yeast matter such as trub or haze is present. 

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