Enhanced soil fertility under Juniperus communis in arctic ecosystems

Abstract

Patches of common juniper (Juniperus communis L.) shrubs potentially facilitate the formation of fertile islands in heath tundra ecosystems thereby inXuencing the long-term resilience of these ecosystems. Although the role of juniper in the formation of such 'islands of fertility' has been studied in semiarid landscapes, there has been little attention paid to the importance of juniper in other ecosystems. In this study we contrast the soil fertility and rates of N Wxation under juniper shrubs with that in open heath tundra in northern Sweden. Plots were established at several individual sites in alpine heath tundra in Northern Sweden and mineral soils to a depth of 10 cm were characterized for available N and P and total C, N, P, Ca, Mg, K, Fe, Mn, Zn, and Cu. Nitrogen Wxation rates were measured by acetylene reduction in feather mosses under juniper canopies and contrasted with N Wxation in both feather mosses and surface soils in the open heath. Soils under juniper had concentrations of total P greatly in excess of P in open heath, furthermore, juniper islands had the highest concentrations of bioavailable P. Nitrogen Wxation rates in the feather moss Pleurozium schreberi (Bird.) Mitt were approximately 150 mol acetylene reduced m ¡2 d ¡1 under the juniper canopy compared to less than 10 mol acetylene reduced m ¡2 d ¡1 in the open heath. Feather mosses under the juniper canopy also Wxed N at a signiWcantly higher rate (on an aerial basis) than that of surface cores from the open heath that included lichen, mosses, and soil crusts. Juniper facilitates the formation of islands of soil fertility that may in turn facilitate the growth of other plants and positively inXuence the long term recovery of heath tundra ecosystems following disturbance.

Across-Habitat Comparison of Diazotroph Activity in the Subarctic

“…Note the different y-axes Nitrogenase activity in the feather moss was nearly identical in shoots growing under Juniperus and in shoots growing without close approximation to Juniperus. This stands in contrast to previous findings [26] in which N 2 fixation in the feather moss was higher when growing under Juniperus than when growing in open heath. However, the differences in N 2 fixation between the two growing patterns in the previous study were mostly driven by the low ground cover of the feather moss in the open heath and the actual N 2 fixation rates were similar.…”

“…The N 2 fixation assays were performed in six areas with dominance of different N 2 fixer associations: the cyano-lichen P. aphtosa (henceforth "lichen"), the symbiosis between rhizobia and the legume A. alpinus (henceforth "legume"), S. fuscum with associated cyanobacteria and methanotrophs (henceforth "Sphagnum"), free-living cyanobacterial N 2 fixers (organic crust) and the feather moss H. splendens (henceforth "feather moss") with associated cyanobacteria. We measured in both feather moss-only as well as in feather moss growing together with Juniperus communis since feather mosses grow frequently under Juniperus canopies, and N 2 fixation on area basis in feather mosses has been suggested to be higher under Juniperus than in feather mosses in open heath [26].…”

A multiproxy evaluation of Holocene environmental change from Lake Igaliku, South Greenland

“…Betula glandulosa is associated with humus-rich soil (Fredskild 1973(Fredskild , 1991De Groot et al 1997) and its spread was likely enabled by Juniperus communis, a pioneer plant that can grow on poor soil (Thomas et al 2007b). Common juniper in tundra ecosystems increases soil fertility by locally increasing N and P and may facilitate the growth of other plant communities (DeLuca and Zackrisson 2007). Accordingly, the Juniperus/Betula succession is probably influenced by climate as well as edaphic and ecological factors.…”

Investigation of the mechanisms underlying the high acetylene-reducing activity exhibited by the soil bacterial community from BC2 horizon in the permafrost zone of the East Siberian larch forest bed

“…; Zackrisson et al . , ; DeLuca and Zackrisson ). However, in East Siberia, the ammonium source remains unknown due to none of the moss growing over the forest bed soil.…”

“…This observed discrepancy has been recognized as the 'missing link' in the nitrogen cycle of the boreal forest ecosystem (Binkley et al 2000). In the Scandinavian forest ecosystem, the moss carpet has been characterized as a source of ammonium fixed from atmospheric dinitrogen gas (N 2 ) by moss-epiphytic cyanobacteria (DeLuca et al 2002;Zackrisson et al 2004Zackrisson et al , 2009DeLuca and Zackrisson 2007). However, in East Siberia, the ammonium source remains unknown due to none of the moss growing over the forest bed soil.…”