Feb 17, 1994 - Thirty-eight soils from forest sites in central. Germany dominated by beech trees (Fagus sylvatica L.) were sampled to a depth of about 10 cm ...
Biol Fertil Soils (1995) 19:215-219
9 Springer-Verlag 1995
Rainer G. Joergensen 9 Helga Kt~bler 9 Brunk Meyer Volkmar Wolters
Microbial biomass phosphorus in soils of beech (Fagus sylvatica L.) forests
Received: 17 February 1994
Thirty-eight soils from forest sites in central Germany dominated by beech trees (Fagus sylvatica L.) were sampled to a depth of about 10 cm after careful removal of the overlying organic layers. Microbial biomass P was estimated by the fumigation-extraction method, measuring the increase in NaHCO3-extractable phosphate. The size of the microbial P pool varied b e t w e e n 17.7 and 174.3 ~ g p g - 1 soil and was on average more than seven times larger than NaHCO3-extractable phosphate. Microbial P was positively correlated with soil organic C and total P, reflecting the importance of soil organic matter as a P source. The mean microbial P concentration was 13.1~ of total P, varying in most soils between 6 and 18. Microbial P and microbial C were significantly correlated with each other and had a mean ratio of 14.3. A wide (5.1-26.3) microbial C : P ratio indicates that there is no simple relationship between these two parameters. The microbial C : P ratio showed strong and positive correlations with soil p H and cation exchange capacity. Abstract
Microbial biomass 9 A c i d i f i c a t i o n 9 Beech forest 9 Soil organic C 9 Total P 9 Fagus sylvatica
Key words
Introduction In many natural and agricultural ecosystems productivity is significantly affected by available inorganic P levels during the growing season (L6pez-Hermindez and Niflo
R.G. Joergensen (~) 9 H. K~ibler 9 B. Meyer Institut for Bodenwissenschaften, von-Siebold-Strasse 4, D-37075 G6ttingen, Germany V. Wolters Institut ft~r aUgemeine und spezielle Zoologie, Stephanstrasse 24, D-35390 Giessen, Germany
1993). In contrast to C and N, P demands by plants must be almost completely supplied by the soil (Ulrich et al. 1986). Hence, soil biological processes involved in P cycling deserve much attention (Ausmus et al. 1976). It has been shown that the rates of P uptake by decomposers may be four to five times higher than those by plants in grassland soils (Cole et al. 1977). The soil microbial biomass as a relatively labile fraction of organic matter is a key site for mineralization of organic P in soils and, thus, is a central feature in the P cycle (Brookes et al. 1984). Components containing P in bacteria and fungi include nucleic acids (RNA and DNA), phosphorylated coenzymes (e.g. ATP), polyphosphates, and phospholipids (Paul and Clark 1989). Many microorganisms, grown in vitro, are able to accumulate more P than necessary for growth in the form of polyphosphates (Harold 1966) or teichoic acids (Grant 1979). However, the significance of this behavior is not proven for organisms grown in soil. In this paper we present the results of a study on the relationship between soil conditions and the size of the microbial P pool in temperate beech forest soils. The strong influence of P nutrition on the growth of forest trees is well established (Likens et al. 1977). However, little is known about the effect of environmental conditions on one of the most important P compartments in forest soils, the microbial biomass. The quantities and forms of P in soil depend on soil-forming factors and may modify C and N accumulation during pedogenesis (Cole and Heft 1981). L6pez-Hern~ndez and Nifio (1993) have recently demonstrated that the soil parent material has a strong effect on microbial P mineralization. Two similar methods have been developed for studying the effect of soil conditions on P incorporation by microorganisms (Brookes et al. 1982; Hedley and Stewart 1982). Both methods are based on the observation that the extra P made extractable by N a H C O 3 after CHC13 fumigation comes from the microbial biomass. By using the method devised by Brookes et al. (1982), we measured microbial biomass P in 38 German beech forest soils.
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Materials and methods Soils The 38 forest soils were collected from forest sites dominated by beech trees (Fagus sylvatica L.) from areas around Braunschweig, G6ttingen, and Zierenberg located in central Germany. Two soils were located in special hydrological situations; soil no. 21 was taken from an edge site with surface water accumulation, and soil no. 28 from a stem foot area. All samples were taken from the A horizon to a depth of about 10 cm after the removal of overlying organic layers, passed through a sieve (
