Effects of temperature on soil net nitrogen mineralisation in two contrasting forests on the eastern Tibetan Plateau, China

Abstract

Abstract. Intact soil cores from two adjacent forest ecosystems (natural coniferous forest and dragon spruce plantation) were incubated in the laboratory to examine effects of temperature, reforestation and their interactions on rates of nitrogen (N) mineralisation, nitrification and ammonification in the subalpine forest of the eastern Tibetan Plateau. Two contrasting soils were incubated at five temperatures (-5, 0, 5, 15 and 258C) for 4 weeks. Rates of N mineralisation and nitrification were insensitive to temperature at lower temperatures (08C and 58C) but increased over higher temperatures (158C and 258C). Large amounts of ammonium were released for each incubation time in both soils when the incubation temperature was À58C. Therefore, the rates of mineralisation and ammonification at À58C were significantly higher than at the other temperatures. Both the accumulations of inorganic N and rates of N transformation were significantly higher in the natural forest than in the plantation. Moreover, temperature sensitivity of net nitrification and N mineralisation were greater in the natural forest than the spruce plantation. Effects of temperature on accumulations of inorganic N and rates of N transformation were dependent on incubation time and forest ecosystem. Our results suggested that À58C might be a key low temperature for N mineralisation in subalpine forest on the eastern Tibetan Plateau; the effect of projected warming on soil N transformation rate may be less significant in plantation forests than natural forests in this specific region.

Nitrogen mineralization simulation dynamic in tobacco soil

“…Xu et al (2014) suggested that rates of N mineralization and nitrification were insensitive to temperature at lower temperatures (0 °C and 5 °C) but increased at higher temperatures (15 °C and 25 °C). Sometimes, at extremely low temperatures, i.e., close to 0 °C, in non-growing seasons, higher N mineralization rates might occur due to lower N immobilisation of microbes .…”

Increasing temperature reduces the coupling between available nitrogen and phosphorus in soils of Chinese grasslands

“…A positive correlation between soil available N and MAT on the Tibetan Plateau could largely be a result of the increased soil microbial activity and microbial biomass under warmer conditions. In incubation experiments, N mineralization in the alpine soils has been found to accelerate with the rise of temperature 32 33 34 . On the contrary, soil N availability in Inner Mongolian grasslands was not significantly related to MAT, consistent with the results of a recent study 15 .…”

Effects of snow absence on available N pools and enzyme activities within soil aggregates in a spruce forest on the eastern Tibetan Plateau

“…Nitrate (NO 3 -) and ammonium (NH 4 + ) were extracted with 2 M KCl (1:5 soil:solution), and then determined using indophenolblue and phenol-disulphonic acid colorimetry, respectively (Xu et al, 2010). Soil net N mineralization rate was quantified following the method of Xu et al (2014): 10 g fresh soil was incubated for one week at 20°C and 50% moisture. Net N mineralization rate on a dry-mass basis was calculated as the difference in inorganic N between the initial and incubated samples.…”