Changes in heated and autoclaved forest soils of S.E. Australia. II. Phosphorus and phosphatase activity

Abstract

Abstract. The effect of soil heat and autoclaving on labile inorganic P (Bray I), microbial P (P-flush) and on phosphatase activity was studied by heating five forest soils in the laboratory, which simulated the effects of heat during bushfires. Top soil was heated to 60 'C, 120 'C and 250 "C or autoclaved for 30 minutes. Soils were analysed immediately after heating and during seven months of incubation to assess immediate and longer-term effects of heating.Labile inorganic P increased immediately after heating and autoclaving soils, with the highest amount recorded for the 250 'C treatment. Phosphorus associated with microbial biomass decreased with heat, and none or small amounts were detected in soils heated to 250 "C and autoclaved, because high temperatures killed the microbial population. Most of the P released from microbes acted as a source of labile inorganic P in soils low in inorganic P, and some of the released P was fixed by the soil. In one soil high in inorganic labile P and with undetectable amounts of microbial-P, the increase in Bray P on heating could only be assigned to solubilisation of other sources of total P. Because high temperatures denature enzymatic proteins, phosphatase activity diminished with the increase in temperature, and no activity was detected in 250 'C and autoclaved soils.Phosphorus released by heating decreased during incubation in three of the five soils studied, approaching values observed in unheated soils. Simultaneously, an increase in microbial P was observed in these heated soils, indicating that the partial recovery of microbial biomass acted as a sink for the decrease in Bray-P measured. Phosphatase activity recovered only partially during incubation of heated soils.

Development of ergosterol, microbial biomass C, N, and P after steaming as a result of sucrose addition, and Sinapis alba cultivation

“…Such heat treatment of soil mobilizes organic C by killing soil microorganisms and by hydrolyzing nonbiomass organic C (Jenkinson 1966;Powlson and Jenkinson 1976). A similar mobilizing effect on P was not observed in the present experiment, probably due to the immediate absorption of heat-mobilized P during extraction (Serrasolsas and Khanna 1995;Endlweber and Scheu 2006).…”

Sampling Natural Viral Communities from Soil for Culture-Independent Analyses

“…Direct counts of introduced model phages were not attempted due to a general inability to distinguish them from naturally occurring phages, which would be coeluted from nonsterile soils. Such an approach would have required prior sterilization of soils (i.e., autoclaving), consequently altering the physical and chemical properties of the soils and thus confounding the environmental relevance of our results (34,39,40). For example, in a study of population dynamics of a host and phage inoculated into sterile potting soil, autoclaving the soil reduced the pH from 6.0 to 4.5 (35).…”

Soil phosphorus availability after slash-and-burn fires of different intensities in rubber agroforests in Sumatra, Indonesia

“…These changes in soil mineralogy may be related to changes in P dynamics observed by Romanya et al (1994), Kwari and Batey (1991) and Serrasolsas and Khanna (1995). However, it is not well understood how heat-induced changes in texture and mineralogical composition affect the total surface area of mineral soil particles (as an indicator of P sorption capacity), the maximum amount of P that can be held by the soil (P sorption capacity, X m ) and the strength with which this P is retained to the soil particles (affinity constant, K).…”