Effects of Temperature and Substrate Quality on Element Mineralization in Six Arctic Soils

Abstract

We compared the effects of temperature on rates of microbial respiration, N mineralization, nitrification, and P mineralization in soils from six arctic ecosystems located along a toposequence on Alaska's North Slope. Soils from these ecosystems were incubated aerobically in the laboratory for 13 wk and at temperatures representative of field values during a typical growing season. Rates of C and N mineralization were insensitive to temperature between 3° and 9°C but increased by factors of 2 or more between 9° and 15°. For both C and N, differences in mineralization rates among soils were greater than differences due to incubation temperature within single soils. This suggests that the quality of soil organic matter varies widely among these ecosystems and is more important than soil temperature differences in controlling rates of these processes in the field. Nitrification occurred in all soils, even at 3°, but there were large differences among soils in nitrification potentials. Overall differences in P mineralization between soils were small. Rates of P mineralization, however, decreased with increasing temperature in soils from some sites and increased with temperature in others. Carbon respired during the 13—wk incubations ranged between 1.5 and 8% of total soil organic C across soil types incubation temperatures. In contrast to the relatively high C mineralization rates in these soils, net N and P mineralization rates were very low and were likely due to high microbial demand for these nutrients. High microbial demand for mineral nutrients can severely limit plant N and P availability in arctic soils.

Responses of peat carbon at different depths to simulated warming and oxidizing

“…Both CO 2 and DOC export rates were higher in 0-20 cm than in deeper layers. This result was consistent with other studies (Biasi et al, 2014;Wang et al, 2013) and in agreement with the idea that older soil found in deeper layers contains higher proportions of "recalcitrant" carbon than younger soil at surface (Bosatta and Agren, 1999;Hogg et al, 1992;Knorr et al, 2005;Nadelhoffer et al, 1991). Under the condition of restricted temperature and O 2 (8°C-AN), Rs did not differ much among soils of different depths; under other three conditions where temperature and O 2 were not so restricted, however, CO 2 and DOC export rates were all substantially higher than those of the same depth in 8°C-AN condition.…”

Dwarf shrubs are stronger competitors than graminoid species at high nutrient supply in peat bogs

“…The results of our experiment suggest that the availability of high N and P as expected under global warming scenarios (Nadelhoffer et al 1991) will alter the competition between vascular plant species in peat bog ecosystems. The interactions between nutrient and competition treatments found for specific leaf area in C. vulgaris and biomass in V. oxycoccus show that competitive vigor increased at higher nutrient availability, which is in contrast with our hypothesis.…”

“…Temperature rise as expected under the global change scenarios is likely to increase mineralization rates (Nadelhoffer et al 1991). Consequently, a higher amount of soil nitrogen (N) and phosphorus (P) will become available for the vegetation.…”

The effects of grazing and burning on soil and plant nutrient concentrations in Colombian p�ramo grasslands

“…The net result of less vegetation cover and higher soil density are higher maximum temperatures in the top soil as a result of less isolation by vegetation and more decomposition of organic material as a result of these higher temperatures and less acidic conditions. Probably, soil moisture content also will be lower (less C, compression, evaporation, Dormaar et al, 1989;Johnston et al, 1971;Moorhead and Reynolds, 1993;Nadelhoffer et al, 1991;Swift et al, 1979;Seastedt et al, 1991).…”

“…Especially the strong P-fixation capacity in these volcanic soils seems to be an important factor but also immobilization by micro-organisms is high in cold climate ecosystems with high C/N and C/P ratios of organic matter (Enriquez et al, 1993;Moorhead and Reynolds, 1993). In general, micro-organisms have a high nutrient demand (Swift et al, 1979), and the decomposer subsystem is mentioned to be able to buffer the nutrient concentrations in some grassland ecosystems (Chapin et al, 1978;Nadelhoffer et al, 1991;Seeling and Zasoski, 1993).…”