Plant litter

Plant litter consists mainly of sugars, cellulose, hemicellulose, lignin, waxes, and polyphe-... 

R. L. Sinsabaugh, R. K. Antibus, and A. E. Linkins, An enzymatic approach to the analysis of microbial activity during plant litter decomposition. Agricult. Ecosyst. Environ.. 14 43 (1991). 

A. P. Whitmore, E. Handayanto, Simulating the mineralization of N from crop residues in relation to residue quality. Driven by Nature—Plant Litter Quality and Decomposition (G. Cadish and K. E. Giller, eds.), CAB International, Wallingford, 1997, p. 337. 

Donor Residue Incorporated Into Growth Medium of Receiver. Because plant litter, In addition to root exudates, Is a potential source of allelochemicals (17), several studies have Investigated the Influence of residues of plants on mineral absorption by receivers. Two extensive studies have been done by Bhowmik and Doll (18, 19). 

Although these studies utilizing Incorporated debris are valuable because they show the potential for allelochemlcals to be released from plant litter, they suffer from a disadvantage. The amount of debris added and Its carbon to nitrogen ratio might lead to alterations In nutrient contents In the soil as the result of proliferation or shifts In populations of micro-organisms. Thus, a control In which a material of similar C/N ratio but lacking allelochemlcals needs to be Included for such studies to be conclusive. The above studies did not Include such controls and thus are not definitive. 

Particulate organic matter LF — 2-18% of organic C, 1-16% of total N SSF - 20 45% of organic C and 13-40% of total N Partially decomposed plant litter isolated by density fractionation (LF) or sieving (SSF). Substrate and centre for soil microbial activity, short-term reservoir of nutrients, food source for earthworms and other soil fauna and focci for formation of water stable aggregates. 

Pentachlorophenol in terrestrial ecosystems clears rapidly (Haque et al. 1988). In one case, a terrestrial ecosystem was given a single surface application of radiolabeled PCP equivalent to 5 kg sodium pentachlorophenate/ha. PCP residues on foliage decreased rapidly, with 50% metabolized within 15 days. After 131 days (autumn), most of the remaining PCP was in the topsoil and plant litter. After 222 days (winter), 39% of the radiocarbon remained. There was little bioconcentration in the resident fauna, due to rapid metabolism and excretion (Haque et al. 1988). 

Bardgett RD, Shine A (1999) Linkages between plant litter diversity, soil microbial biomass and ecosystem function in temperate grasslands. Soil Biol Biochem 31 317-321... 

Jensen, V. Decomposition of angiosperm tree leaf litter, pp. 69-104. In C. H. Dickinson, and G. J. F. Pugh, Eds. Biology of Plant Litter Decomposition. Vol. 1. New York Academic Press, 1974. 

Plant litter collection, maintenance, pruning, mowing, and/or harvesting... 

As mentioned earlier, the abundance of carbohydrates in ocean DOM relative to river DOM does not reflect the biochemical compositions of terrestrial plants and marine phytoplankton. It appears that carbohydrates in plant litter are largely degraded in soils, resulting in relatively low concentrations in river DOM. Carbohydrates are the major components of exudates from phytoplankton (Biddanda and Benner, 1997 Biersmith and Benner, 1998), and herbivorous grazing also releases carbohydrates to the DOM reservoir (Strom et al., 1997). The in situ production of dissolved carbohydrates in the surface ocean appears to result in a greater relative abundance of carbohydrates in the ocean relative to rivers. 

Several recent studies investigated the bioavailability of DOM and total hydrolyzable neutral sugars and amino acids in lake (Weiss and Simon, 1999), creek (Volk et al., 1997 Gremm and Kaplan, 1998), and marine (Amon et al., 2001) waters. The DOM in the lake and marine environments was predominantly derived from plankton, whereas the DOM in the creek was predominantly derived from soils and decaying plant litter. Although limited in number, these systems represent a diverse array of aquatic environments. Each of these studies determined the percentages of DOC that were... 

Hammel, K. E. (1997). Fungal degradation of lignin. In Driven by nature—Plant Litter Quality and Decomposition, Cadisch, G., and Giller, K. E., eds., CAB International, Wallingford, UK, pp. 33—45. 

Melillo, J. M., Aber, J. D., Linkins, A. E., Ricca, A.,Fry, B., and Nadelhoffer, K. J. (1989). Carbon and nitrogen dynamics along the decay continuum plant litter to soil organic matter. Plant Soil 115,189-198. 

Figure 6.7. Simplifed soil carbon cycling scheme. Major inputs (plant litter) to and outputs (respiration and erosion) from the soil carbon reservoir. The observed flux of C out of the soil can be modeled by assuming three pools of carbon an active pool with a turnover time on the order of years, an intermediate pool with a turnover time on the order of decades to centuries, and a passive pool with a turnover time on the order of millennia. The decomposition constant is k = 1/t. Subscripts a, i, and p refer to the active, intermediate, and passive C pools, respectively. Adapted with permission from Amundson, R. (2001). The carbon budget in soils. Annu. Rev. Earth Planet. Sci. 29, 535-562.

I. Litter Decomposition Experiments. The rate of mass loss of fresh plant litter may be used to estimate litter decomposition rates, assuming first-order kinetics ... 

Isotopic Tools Tracers. Carbon has three stable or long-lived isotopes 98.9% of earth s C is 12C, -1.1% is 13C (a stable isotope), and about one in a trillion (1 in 1012) carbon atoms is 14C. By enriching or depleting the ratios of the rare isotopes in plants, plant litter, or other organic material put in soil, it is possible to follow the pulse of altered isotopic ratios (and the carbon compounds they were associated with) as they move through the system. 

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