Microbial activity and survival in soils dried at different rates

Abstract

The changes in microbial biomass C, soil respiration, microbial activity (respiration/microbial C) and the content of oxidizable organic C extracted by 0-5 M K2SO4, were measured in four soils of contrasting characteristics (a sand, two silt loam soils and a peat) which were air-dried at 22�C at three different rates in the laboratory. Respiration was also measured on samples of the drying soils rewetted with water. The rates of drying were: <10 h (fast), <33 h (medium) and <62 h (slow); drying was carried out for 6 h on consecutive days, with overnight storage. Measurements were also made on soils stored at field-moisture content over the 15 day duration of the experiment. Respiration and activity declined continuously and in a generally linear manner as the volumetric water content (W,) decreased. The decline in respiration in relation to water content W, was similar for all four soils and for the three rates of drying. Microbial biomass C also declined but generally only after a considerable initial period of drying (after the soils had reached Wv of 0-1-0.3). Extractable C values increased, but only after an initial drying period (Wv below 0.06-0.12). The increases in extractable C were approximately coincident with the decreases in microbial C, but only part of the increase in extractable C could be accounted for by the decrease in microbial C. Rewetting of dried soils caused a marked increase in respiration, particularly when the rewetted soils had reached Wv values where extractable C had begun to increase. The relationship between microbial activity and extractable C was similar for all four soils and was not affected by the rate of drying. The similarity of the microbial responses in these contrasting soils, and the absence of any detectable differences between rates of drying suggest that the microbial communities had similar survival strategies to resist desiccation, and occupied comparable physical niches in the soils, despite these soils having widely differing textures, organic matter content, and soil moisture characteristics.

Seasonal Changes and Treatment Effects on Soil Inorganic Nutrients Following a Decade of Fertilizer Addition in a Lowland Tropical Forest

“…It is likely that our monthly sampling regime missed short-term nutrient pulses, although the absence of a broad increase in nutrient availability at the onset of the wet season provides some support for the suggestion that nutrient pulses are more common in dry tropical forests with a 6-mo dry season (Singh et al, 1989;Campo et al, 1998) than in semi-deciduous forests with a 4-mo dry season (Yavitt et al, 1993). This might occur because the length of the dry season influences the degree of deciduousness (and therefore the amount of litter fall in the dry season), as well as the degree of microbial desiccation and associated nutrient release at the end of the dry season (West et al, 1992).…”

The effects of water potential on some active forms of phosphorus in a calcareous soil amended with sewage sludge

“…These finding may be related to microbial activity and populations. It was reported that soil drying reduces microbial activity and mineralization of organic C, N and P, decreases microbial mobility and restricts substrate and nutrient availability (West et al, 1992;Pulleman and Tietema, 1999). According to Magid et al (1999), microorganisms lose some of their ability to degrade complex substrates during desiccation.…”

Microbial communities in an ephemeral stream system and the implications of saline mine discharge

“…The main differences were higher abundances of both eukaryote and bacteria groups in habitats with surface water. This is supported in the literature where inundated stream sediments and soil have been shown to increase in bacterial biomass and activity (West et al 1992, Baldwin and Mitchell 2000, Austin and Strauss 2011, Wilson et al 2011 as well as increases in invertebrate assemblages (Larned et al 2007). In sediments with surface water, the higher abundances of eukaryotic groups were predominantly Gastrotricha, Ciliopora and Turbelaria as well as phototrophs such as the green alga Chlorophyta.…”

“…The two dates coincide with variation in stream flow with the dry and wet season. Differences between the dry and wet season were expected as desiccation can be a stressor on microbial communities, where drying of stream sediments has been reported to affect ecosystem processes and change microbial community structure (West et al 1992, Boulding et al 2008, Marxsen et al 2009). The differences in community composition and consequences of changing hydrology in these sediments are further discussed in Section 6.4.1.…”