Carbon, nitrogen, and phosphorus stoichiometry of organic matter in Swedish forest soils and its relationship with climate, tree species, and soil texture

[摘要] While the carbon (C) content of temperate and boreal forest soilsis relatively well studied, much less is known about the ratios of C,nitrogen (N), and phosphorus (P) of the soil organic matter, as well as the abioticand biotic factors that shape them. Therefore, the aim of this study was toexplore carbon, nitrogen, and organic phosphorus (OP) contents and elementratios in temperate and boreal forest soils and their relationships withclimate, dominant tree species, and soil texture. For this purpose, westudied 309 forest soils located all over Sweden between 56 and68 ∘  N. The soils are a representative subsample of Swedish forestsoils with a stand age >60  years that were sampled for theSwedish Forest Soil Inventory. We found that the N stock of the organiclayer increased by a factor of 7.5 from − 2.0 to 7.5  ∘ C mean annual temperature (MAT), which is almost twice as much as theincrease in the organic layer stock along the MAT gradient. The increase inthe N stock went along with an increase in the N:P ratio of the organiclayer by a factor of 2.1 from − 2.0 to 7.5  ∘ C MAT( R 2 =0.36 , p <0.001 ). Forests dominated by pine had higher C:N ratios in the organic layer and mineral soil down to a depth of 65 cm thanforests dominated by spruce. Further, also the C:P ratio was increased inthe pine-dominated forests compared to forests dominated by other treespecies in the organic layer, while the C:OP ratio in the mineral soil was notelevated in pine forests. C, N, and OP contents in the mineral soil werehigher in fine-textured soils than in coarse-textured soils by a factor of2.3, 3.5, and 4.6, respectively. Thus, the effect of texture was stronger onOP than on N and C likely because OP adsorbs very rigidly to mineralsurfaces. Further, we found that the P and K concentrations of the organiclayer were inversely related to the organic layer stock, while the N:P ratio was positively related to the organic layer stock. Taken together, theresults show that the N:P ratio of the organic layer was most stronglyrelated to MAT. Further, the C:N ratio was most strongly related to dominanttree species even in the mineral subsoil. In contrast, the C:P ratio wasonly affected by dominant tree species in the organic layer, but the C:OP ratio in the mineral soil was hardly affected by tree species due to thestrong effect of soil texture on the OP concentration.

[学科分类] 大气科学