Relationships between topography, vegetation, soil and microclimate
Our study sites covered a range of abiotic and biotic environmental conditions (Figure 2c), indicating that the stratified random sampling approach overall captured environmental gradients in the area. Yet, relationships between topographic, vegetation and soil variables and microclimate only partly reflected our expectations (Figure 5). As expected, soil temperature decreased with higher elevation and underneath higher vegetation cover, corroborating trends previously found in Fennoscandian tundra (Kemppinen et al. 2021). In contrast, solar radiation predicted trends opposite to expected relationships, particularly lower rather than higher soil temperature but higher rather than lower soil moisture, possibly due to its close association with slope values. Local topography as quantified by TPI did not explain variation in any vegetation or soil parameter, perhaps because variation in TPI was more constrained than in other variables (Figure 2c), thus not well representing differences in snow accumulation or wind exposure across the landscape. Also, neither TWI nor soil texture explained variation in growing-season soil moisture among plots. Here, our gradient most likely did not cover the entire spectrum of conditions present in the area, as very wet locations were not covered (Figure 2c), probably as a result of the dry summer in 2019 and of standing water areas being masked out during the stratification process. The example highlights the difficult issue of obtaining reliable soil moisture predictions in tundra ecosystems (Kemppinen et al. 2018). In addition, implicit uncertainty in gridded topographic variables might have added further noise to our dataset.