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Plant–soil feedback (PSF) results from the influence of plants on the composition and abundance of various taxa and functional groups of soil micro‐organisms, and their reciprocal effects on the plants. However, little is understood about the importance of fine root traits and root economic strategies in moderating microbial‐driven PSF.We examined the relationships between PSF and 11 chemical and morphological root traits from 18 sub‐arctic meadow plant species, as well as the soil microbial community composition which we characterized using phospholipid fatty acids (PLFAs) and high‐throughput sequencing. We also investigated the importance of the root economics spectrum in influencing PSF, because it indicates plant below‐ground economic strategies via trade‐offs between resource acquisition and conservation.When we considered the entire root economics spectrum, we found that PSFs were more negative when root trait values were more acquisitive across the 18 species. In addition, PSF was more negative when values of root nitrogen content and root forks per root length were higher, and more positive when root dry matter content was higher. We additionally identified two fungal orders that were negatively related to PSF. However, we found no evidence that root traits influenced PSF through its relationship with these fungal orders.Synthesis. Our results provide evidence that for some fine root traits, the root economics spectrum and some fungal orders have an important role in influencing PSF. By investigating the roles of soil micro‐organisms and fine root traits in driving PSF, this study enables us to better understand root trait–microbial linkages across species and therefore offers new insights about the mechanisms that underpin PSFs and ultimately plant community assembly. [ABSTRACT FROM AUTHOR]

In the prolonged absence of catastrophic disturbance, ecosystem retrogression occurs, which is characterized by declining soil nitrogen (N) and phosphorus (P) availability, increasing plant and soil N to P ratios, and reduced plant biomass and productivity. It is, however, largely unknown as to how the effects of plant communities on soil nutrients change during retrogression or might contribute to declining nutrient availability as retrogression proceeds.We studied a well‐characterized system of 30 lake islands in northern Sweden that collectively represent a 5,000‐year post‐fire retrogressive chronosequence. For each island, we established an experiment that involved full factorial removal of three plant functional groups (tree roots, dwarf shrubs and mosses), and of three species of dwarf shrub (Vaccinium myrtillus, V. vitis‐idaea and Empetrum hermaphroditum). After 19 years, we took various measures of soil N and P availability, and measured foliar N and P for each dwarf shrub species, for each plot in the experiment.Although plant removal effects (and particularly removal of tree roots, shrubs and Vaccinium species) on below‐ground N and P measures sometimes changed during retrogression, this seldom happened in a way that explains the decline in nutrient availability and increase in N to P ratios that characterize ecosystem retrogression. The only exceptions were that the positive effects of tree roots on soil mineral N and P, and of V. myrtillus on soil mineral P, declined during retrogression.Plant removal effects on community‐level measures of shrub N and P varied greatly across the chronosequence, but these effects again did not align with the changes in soil nutrient availability or N to P ratios that characterize ecosystem retrogression.Synthesis. Our results suggest that retrogression, and associated changes in nutrient availability and soil N to P ratios, is driven mainly by longer‐term pedogenic processes as opposed to shorter‐term effects of plant communities on soil N and P availability. More generally, they illustrate the value of long‐term and large‐scale experimental manipulations of plant communities for showing how effects of biodiversity loss on ecosystem properties vary across contrasting ecosystems. [ABSTRACT FROM AUTHOR]