Permafrost Regime Affects the Nutritional Status and Productivity of Larches in Central Siberia

Abstract

Permafrost exerts strong controls on forest development through nutrient availability. The key question of this study was to assess the effect of site conditions on macroelement concentration and stable isotope (δ 13 C and δ 15 N) dynamics during the growing season, and nutrient stoichiometry and resorption efficiency in the foliage of two common larch species in Siberia. Foliar nutrient (N, P and K) concentrations of larches grown on permafrost soils were exceptionally high in juvenile needles compared to those from a permafrost-free region (+50% and 130% for P and K), but were two-fold lower at needle maturation. Within permafrost terrain trees, sites with a warmer and deeper soil active layer had 15-60% greater nutrient concentrations and higher δ 15 N in their needles compared to shallower, colder soils. Larch of permafrost-free sites demonstrated an enrichment of foliage in 15 N (+1.4% to +2.4 ) in comparison to permafrost terrain (−2.0% to −6.9 ). At all sites, foliar δ 13 C decreased from June to August, which very likely results from an increasing contribution of current photoassimilates to build foliar biomass. With senescence, nutrient concentrations in larch needles decreased significantly by 60-90%. This strong ability of larch to retain nutrients through resorption is the essential mechanism that maintains tree growth early in the growing season when soil remains frozen. The high resorptive efficiency found for K and P for larches established on permafrost suggests nutrient limitation of tree growth within the Central Siberian Plateau not only by N, as previously reported, but also by P and K. The increasing nutrient concentrations and a 15 N enrichment of foliage towards warmer sites was paralleled by an up to 50-fold increase in biomass production, strongly suggesting that accelerated nutrient cycling with permafrost degradation contributes to an increased productivity of Siberian larch forests.

Wildfires lead to decreased carbon and increased nitrogen concentrations in upland arctic streams

“…In contrast to DOC and DON, concentrations of NO 3 − demonstrate a shorter recovery time, returning to their pre-disturbance concentrations approximately at 10 years. In larch forests post-fire, growth of the moss layer and OM storage is very slow 32 but there is a greater demand for inorganic N from growing shrubs and larch seedlings, which require fire to propagate 32,33 . This relatively short recovery of NO 3…”

Water and energy transfer modeling in a permafrost‐dominated, forested catchment of Central Siberia: The key role of rooting depth

“…This high morphological variability of the tree stands between slopes stems from the fact that better insolation in SAS leads to fewer but higher, larger and healthier trees than in NAS (seeFigure 1). Additional details on the vegetation cover of this region are provided by Prokushkin et al65…”

Tree ring-based reconstruction of the long-term influence of wildfires on permafrost active layer dynamics in Central Siberia

“…1a). Details on stand and soil characteristics are given in a recent study by Prokushkin et al (2018). Located within the continuous permafrost zone, the region is characterized by a severe continental climate.…”

“…Comprising up to 24% of the Northern Hemisphere landmass (Zhang et al, 1999;, the permafrost zone is a particularly important component of the circumpolar boreal forest. Both, soil-forming activities (Ershov 1994(Ershov , 1995Gubin and Lupachev, 2008), as well as water and nutrient supply for plants (Sugimoto et al, 2002;Saurer et al, 2016;Prokushkin et al, 2018), predominantly depend on the freeze-thaw processes of the upper permafrost stratum, the socalled active layer (Permafrost Subcommittee, 1988). Operating at large spatial and temporal scales, a multitude of effects, related to the current global climate change, have been reported as responsible for changes in the behavior of different components of the permafrost-sphere (Grosse et al, 2016); and these influences are expected to increase under predicted future warming (IPCC, 2013).…”