The influence of litter quality was introduced into a model, using data from 11 sites at which litter of different quality had been incubated. A possible consequence of this observation could be a higher rate of organic matter accumulation at sites that initially promote a high initial mass-loss rate for litter than at sites with conditions that give lower initial rates, at least for a given species of litter. Changes in Substrate Composition During Decomposition -- Ch. Net fine root production was estimated from changes in standing crop. In spite of this complexity, several major processes are involved and general trends can be outlined. Thus early-stage decomposition is primarily controlled by concentrations of limiting nutrients, especially N and P, whereas lignin decomposition exerts the dominant control in the latter stages. Litter mass-loss rates decreased during decomposition as lignin concentrations increased.
The concepts white-rot, brown-rot, and soft-rot and what they stand for functionally in terms of degradation processes will be presented. As the decay of litter progresses through time, the constituents that regulate the rate of mass loss can change. Models of this type contribute to our understanding of scale integration and may facilitate the estimation of decomposition rates among landscape units. Earlier findings are re-evaluated in light of recent research and with relevance to current areas of investigation. The book is well arranged, relatively easy to read, contains fantastic graphics! In the first case study, Kriging was used to interpolate humus-layer thickness over 41 years, giving an increase all over the region which was positively related to temperature sum. Enzyme activity patterns differed among litter types when expressed on the basis of decomposition time or cumulative mass loss. The delivery of heat and moisture to the litter will exert a control over the rate at which the decay phases postulated by Berg and Staaf 1980a can proceed.
The dominant primary decomposers in boreal and temperate forest soil systems are the microorganisms, encompassing both fungi and bacteria. All litter types had similar carbon fraction chemistries at t. It is clear that either unknown errors and biases, or, unknown variables are causing these regional differences in response to climatic variables. Not only can these site-specific factors influence microbial metabolism, they can also alter the composition of the microbial community, as was discussed in Chapter 3. We have discussed the possible formation of stable humus from other litter components, and we cannot exclude that, e.
Nitrification was not correlated with aboveground production. Nitrogen first accumulated in all litters, but by the end of 2-yr incubation, N release had begun in all foliage litters. The quality and quantity of litter fall influences nature of the microbial community, including its size, composition, function and physiological properties. The concepts white-rot, brown-rot, and softrot, and what they stand for functionally in terms of degradation processes will be presented. In contrast, as potassium K is leached its concentration decreases heavily. Combining sites in the boreal and Atlantic climates gave an R-adj 2 of 0. Further, it introduces a conceptual model for litter transformations from litter fall until the decomposing litter accumulates as humus.
Most studies of litter decomposition in forests have focused on foliar litters because of their large amounts, and relatively high nutrient contents. We distinguished an initial phase of fast changes in K concentration and a later one in which the litter was close to humus and all K appeared to be immobile. Soils are dynamic, complex systems of inorganic, organic and biotic components that have the capacity to support plant life. With a close connection between the chemical composition of newly shed litter and the relative amount of recalcitrant residual litter Chap. The dominant primary decomposers in boreal and temperate forest soil systems are the microorganisms, encompassing both fungi and bacteria. The authors can be congratulated for their impressive efforts in publishing this highly professional volume. Because plant litter decomposition is directly mediated by extracellular enzymes ectoenzymes , analyses of the dynamics of their activity may clarify the mechanisms that link decomposition rates to substrate quality and nutrient availability.
The significance of this finding is discussed. Concurrent estimates of total nitrogen requirement for this production ranged from 73 to 184? The effects of substrate quality, climate, and their interactions on decomposition are presented as well as examples of litter types that break the basic pattern. Thus, the initial chemical composition is important and for spruce litter manganese Mn , concentration has been positively related to first-year mass loss. Regressions were calculated mainly for needle litter fall and to some extent for total litter fall. Manganese has received little attention in decomposition studies to date.
In addition, there are several polymeric compounds including suberins, tannins, and cutins. Estimating Carbon Sequestration Rates on a Regional Scale -- Appendix I. Due to the immense diversity of possible factors and interactions, decomposition in a natural setting can be described in general terms only. In the late phase a slight increase in concentrations was observed. Litter types that have been found to deviate from the general pattern will also be discussed.
The book is well arranged, relatively easy to read, contains fantastic graphics. Huttl, Journal of Plant Physiology, Vol. The authors can be congratulated for their impressive efforts in publishing this highly professional volume. In initially chemically identical Scots pine needle litter incubated under different climatic conditions, the lignin concentration increased faster as a function of accumulated mass loss when the climatic conditions promoted a higher initial mass-loss rate. In spite of this complexity, several major processes are commonly involved, and general trends can be outlined. Further, it introduces a conceptual model for litter transformations from litter fall until the decomposing litter accumulates as humus. A system is suggested for humus accumulation rates among forest systems, a system that may be a starting point for estimates of carbon sequestration in forest systems.