Microbial and Microarthropod Detrital Processing in a Prairie Soil

Abstract

Spring burning and raking were used to increase detrital productivity relative to undisturbed plots in a Wisconsin prairie soil (Mollic Hapludalf). Relative changes in fungal hyphae and microarthropod density were determined 3, 7, and 28 wk after treatment; percent carbon, particulate organic matter, and bacterial density were determined after 28 wk. Significant effects 28 wk after burning were disappearance of 30% of fine particulate organic matter, microarthropod density increase due to vertical migration, and increased particulate organic matter ingestion by oribatid mites. Twenty—eight weeks after raking, significant effects included 7% soil carbon loss and disappearance of 57% of fine particulate organic matter, and 25% of the fungal hyphae. In raked plots, bacterial cell density was 21% greater than in other treatments; microarthropod density increased through reproduction and vertical migration. These result demonstrate that (1) increased plant productivity speeds processing of plant material by fungi and orbatid mites, (2) physical disturbance of the soil more strongly increases processing of plant material and dead hyphae by bacteria, as well as orbatid, prostigmatid, as astigmatid mites (3) root growth is least where processing rate is greatest. Significant increases in proportions of orbatids and Collembola with empty guts in November suggest that in grasslands, resources may limit detritivores in fall.

Comparative Analyses of Carbon Dynamics in Native and Cultivated Ecosystems

“…Presumably, enhanced oxidative effects from tillage disturbance and higher soil temperatures, especially in the postharvest period, are important in the wheat ecosystem. 1978, Lussenhop 1981. Another factor may be an increased surface-volume ratio for wheat litter resulting from the harvesting and incorporation processes.…”

“…Tillage and incorporation of litter in the surface soil en-hanced decomposition rates in grassland studies (Nyhan 1975, Rossetal. 1978, Lussenhop 1981. Breaking up the litter thatch with a roto-mower at the Missouri prairie site accelerated in situ disappearance compared to intact litter plots (Zimmerman and Kucera 1977).…”

Beyond microbes: Are fauna the next frontier in soil biogeochemical models?

“…For example, while most soil fauna clearly depend on microbes to meet their nutritional demands, the exact mode by which microbes are exploited (endosymbiosis, consumption of microbially-degraded plant tissue, or direct microbivory) can vary significantly among faunal taxa. This variation is likely to have important consequences for downstream SOM dynamics, yet our understanding of the exact modes by which fauna exploit microbes is far from complete (but see Lussenhop 1981;Bonkowski et al 2000;Maraun et al 2003;Smrz and Norton 2004;Berg et al 2004;Crowther et al 2011). Further yet, the importance of different modes of microbial exploitation under different climatic conditions and disturbance levels is virtually unknown.…”