Increased winter soil temperature variability enhances nitrogen cycling and soil biotic activity in temperate heathland and grassland mesocosms

[摘要] Winter air temperatures are projected to increase in the temperate zone,whereas snow cover is projected to decrease, leading to increased soiltemperature variability, and potentially to changes in nutrient cycling.Here, we experimentally evaluated the effects of increased winter soiltemperature variability on selected aspects of the N-cycle in mesocosmscontaining different plant community compositions. The experiment wasreplicated at two sites, a colder mountainous upland site with high snowaccumulation and a warmer and drier lowland site.

Increased soil temperature variability enhanced soil biotic activity for bothsites during winter, as indicated by 35% higher nitrogen (N)availability in the soil solution, 40% higher belowground decompositionand a 25% increase in the potential activity of the enzymecellobiohydrolase. The mobilization of N differed between sites, and the¹⁵N signal in leaves was reduced by 31% in response to winterwarming pulses, but only at the cold site, with significant reductionsoccurring for three of four tested plant species at this site. Furthermore,there was a trend of increased N leaching in response to the recurrent winterwarming pulses.

Overall, projected winter climate change in the temperate zone, with lesssnow and more variable soil temperatures, appears important for shifts inecosystem functioning (i.e. nutrient cycling). While the effects of warmingpulses on plant N mobilization did not differ among sites, reduced plant¹⁵N incorporation at the colder temperate site suggests that frostdamage may reduce plant N uptake in a warmer world, with importantimplications for nitrogen cycling and nitrogen losses from ecosystems.

[学科分类] 地球化学与岩石