Accumulation of organic matter along a pollution gradient: Application of odum's theory of ecosystem energetics

Abstract

Forest soil biology in Scots pine forests of the Empetrum-Vaccinium type was studied around the industrialized city of Oulu, northern Finland since 1987. The forest sites lie along a sulphur and nitrogen concentration gradient in the mor humus ranging from 1.6 to 3.9 mg S g(-1) organic matter (OM) and from 14 to 23 mg N g(-1) OM. A number of biological parameters have earlier been found to vary along this gradient, thus indicating that the ecosystems are subjected to a pollution stress. Total microbial biomass and various activity parameters were studied in 1991. The different methods are discussed and the results interpreted within the light of Odum's theory of the energetic stabilization of ecosystems. Microbial biomass C determined by the fumigation-extraction (FE) technique varied from 5 to 10 mg g(-)OM, N from 0.5 to 1.0 mg g(-1)OM, and basal respiration rate from 0.040 to 0.097 mg CO2 h(-1) g(-1)OM. All decreased along the pollution gradient. Substrate induced respiration values (SIR) varied from 0.025 to 0.085 mg CO2-C h(-1) g(-1)dw. SIR correlated well with the biomass values determined by the FE technique. The lag time of the microbial community after glucose addition (varying from 13 to 22 h) was shortened and the specific respiration increment of the microbial community in response to glucose addition increased along the gradient. The metabolic quotient (respiration/biomass) of the microflora strongly depended on the technique and equation used in calculating the microbial biomass. The results show a reduced biomass, but a more intensive regeneration and intensified activity per biomass unit of microorganisms in polluted forest soil. This in turn denotes an alteration in the microbial community in favor of a higher proportion of r-strategists under the disturbed conditions. In contrast, K-strategists may be more dominant under less polluted conditions. This interpretation is presented with some reservations concerning methodology. There is a need for the calibration of each method for determining microbial biomass in different types of soil.

Plasticity and constraint in growth and protein mineralization of ectomycorrhizal fungi under simulated nitrogen deposition

“…Nitrogen enrichment generally stimulated enzyme activity, indicating that mineral N is more commonly limiting to protease synthesis than to growth. This is consistent with field and laboratory studies showing a stimulation of fungal metabolism by N additions, e.g., mineralization rates (Hatch et al 2000, Jonasson andMichelson 1996) and respiration rates (Ohtonen 1994, Ek 1997, Hatch et al 2000, but only small increases (Carreiro et al 1996), no change (Hatch et al 2000) or net decreases (Ohtonen 1994, Bardgett andMcAlister 1999) in microbial biomass. Our study of ten species included only one case (Leccinum scabrum) when mineral N inhibited protease activity (but see Zhu et al 1994).…”

Ecosystem properties and microbial community changes in primary succession on a glacier forefront

“…The increase in biomass was seen most clearly using direct estimates, which also supports the results for FungPLFA in barren soil samples. A problem with microbial biomass analyses is that most methods measure only subset components of the total microbial biomass or do not treat the active and dormant components equivalently (Wardle and Parkinson 1991;Ohtonen 1994). Thus the results using dierent methods are not necessarily comparable, as was seen here.…”

“…Microbial activity parameters were somewhat lower but Lag longer than is usual for boreal forest soils (Palmborg and Nordgren 1993;Ohtonen 1994;VaÈ re et al 1996;MerilaÈ and Ohtonen 1997;Palmborg et al 1998). The general range for Bas in forest soils has been found to be 0.01±0.05 mg CO 2 -C g A1 OM h A1 and that for Lag about 10±20 h This may indicate harsh conditions in early succession and slow metabolism of microorganisms.…”

Efeito do monocultivo de Pinus e da queima do campo nativo em atributos biológicos do solo no Planalto Sul Catarinense

“…Apesar de alguns pesquisadores questionarem o uso de qCO 2 como bioindicador de distúrbios e estresse no meio, por não distinguir esses efeitos (Yan et al, 2003), a maioria dos estudos tem aplicado extensamente o qCO 2 na avaliação de regime de cultivo (Anderson & Domsch, 1990), gradiente de poluição (Ohtonen, 1994), efeito da temperatura (Anderson & Gray, 1991) e ecossistemas de floresta (Anderson & Domsch, 1993).…”