Factors influencing limit values for pine needle litter decomposition: a synthesis for boreal and temperate pine forest systems

Abstract

We synthesized available data for decomposition of pine (Pinus) needle litter in pine forests to determine the litter chemical characteristics and climate factors that explained variation in the limit value, i.e. the level of accumulated mass loss at which the decomposition process either continues at a very low rate or possibly stops. Our data base included 56 separate studies on decomposition of pine needle litter, spanning Scots pine, lodgepole pine, Aleppo pine, stone pine and white pine, mainly incubated at the site of collection. Studies had 5 to 19 samplings, on average 10, and the decomposition was followed to a mass loss ranging from 47 to 83%, on average 67%. The periods from 3.0 to 5.4 years, on average 3.9 years, were of sufficient duration to allow estimates of limit values of decomposition. We used a linear mixed model with regression effects to relate limit values to potential explanatory variables, namely the sites' long-term mean annual temperature (MAT) and mean annual precipitation (MAP) and to substrate-chemistry factors. Regarding the latter, we explored two models; one that included initial concentrations of water solubles, lignin, N, P, K, Ca, Mg, and Mn and one that included only lignin, N, Ca, and Mn to focus on those nutrients known to influence lignin degradation. Using backward elimination significant explanatory variables were determined. For litter decomposed in its site of origin we found the limit value to depend mainly on the initial concentration of Mn, with higher Mn concentrations resulting in higher accumulated mass loss. Thus, litter with higher Mn reached a higher limit value and left a smaller stable fraction. This is likely due to the fact that Mn is an essential component of ligninolytic enzymes important for degrading litter in the later stages of decomposition. Manganese has received little attention in decomposition studies to date. Given its significance in this synthesis, the role of Mn in influencing variation in the late stages of decomposition among ecosystems and among litters of other genera besides Pinus deserves further attention

Humusica 1, article 2: Essential bases—Functional considerations

“…We may comment on that this layer would be made up of stable litter residues and judging from data (cf. Figure 13 and results from a limit-value study : Berg et al, 2010) its decomposition would not be sensitive to temperature.…”

“…Ten factors including climate (MAT, MAP; P= Precipitation) and substrate quality (N, P, K, Ca, Mg, Mn, AUR, and water solubles; AUR = Acid Unhydrolyzable Residue) were related (linear relationships) to limit values and the only significant relationship was that to Mn concentration. Decomposition data from a climate gradient were used but there was no effect of MAT on limit values (Berg et al, 2010). The genus Pinus is so far the only genus/species that has been investigated for regulating factors for limit values.…”

Phosphorus status of soils from contrasting forested ecosystems in southwestern Siberia: effects of microbiological and physicochemical properties

“…However, decomposition processes generally depend on microbiological activity as well as organic matter quality (Ushio et al, 2010;Voriskova et al, 2011). Organic matter quality has been linked to the lignin and nutrient concentrations in the forest floor and the lignin/N, C/N and C/P ratios (Hättenschwiler and Gasser, 2005;Berg et al, 2010;Blanco et al, 2011). P availability is further controlled by physicochemical processes (e.g.…”

Long-term litter decomposition controlled by manganese redox cycling

“…Numerous studies (9)(10)(11)(12)(13)(14) have measured a strong positive relationship between Mn content of litter and litter decomposition (expressed as % mass loss) in boreal, temperate, and semiarid forest ecosystems. Among all other parameters tested (water soluble C, lignin, N, P, K, Ca, and Mg contents), Mn content best predicted litter mass loss, leading Berg et al (10) to conclude that "Mn concentration is the single main factor" governing litter decomposition in these forest biomes. However, efforts to experimentally validate the effect of Mn availability on decomposition rates have produced ambiguous results (15) and have been hampered by the lack of explicit consideration of Mn redox cycling in the soil system.…”