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Berg, Björn ; Meentemeyer, Vernon:
Litter quality in a north European transect versus carbon storage potential.
In: Plant and Soil.
Bd. 242
(2002)
.
- S. 83-92.
ISSN 1573-5036
DOI: https://doi.org/10.1023/A:1019637807021
Abstract
Newly shed foliar plant litter often has a decomposition rate of ca 0.1–0.2% day−1, which decreases greatly withtime and may reach 0.0001 to 0.00001% day−1 or lower in litter material in the last stages of decay. The decrease indecomposability (substrate quality) varies among species and is complex, involving both direct chemical changesin the substrate itself and the succession in microorganisms able to compete for substrate with a given chemicalcomposition. In late stages, the decomposition appears very little affected by climate, suggesting that climatechange will have little effect on late-stages decomposition rates. Here, we apply a model for the late stages of litterdecomposition to address the question of climate-change effects on soil-C storage. Decomposition of litter turninginto soil organic matter (SOM) is determined by the degradation rate of lignin. In the last phases of decay, raised Nconcentrations have a rate-retarding effect on lignin degradation and thus on the decomposition of far-decomposedlitter and litter in near-humus stages. The retardation of the decomposition rate in late stages may be so strongthat decomposition reaches a limit value at which total mass losses virtually stop. At such a stage the remaininglitter would be close to that of stabilized SOM. The estimated limit values for different species range from about45 to 100% decomposition indicating that between 0 and 55% should either be stabilized or decompose extremelyslowly. For no less than 106 long-term studies on litter decomposition, encompassing 21 litter types, limit valueswere significantly and negatively related to N concentration, meaning that the higher the N concentration in thenewly shed litter (the lower the C/N ratio) the more litter was left when it reached its limit value. Trees growingunder warmer and wetter climates (higher actual evapotranspiration, AET) tend to shed foliar litter more rich inN than those growing under colder and drier climates. A change in climate resulting in higher AET would thusmean that within species, e.g., Scots pine, a higher N level in the foliar litter may result. Further, within the borealsystem deciduous species appear to have foliar litter richer in N than have conifers and within the conifers group,Norway spruce has needle litter more rich in N than, e.g., Scots pine. Thus, a change of species (e.g., by planting)from pine to spruce or from spruce to a deciduous species such as birch may result in a higher N level in the litterfall at a given site. In both cases the result would be a lower limit value for decomposition. The paper presents anhypothesis, largely based on available data that a change in climate of 4◦ higher annual average temperature and40% higher precipitation in the Baltic basin would result in higher N levels in litter, lower decomposition and thusa considerable increase in humus accumulation.