Impact of plant functional group and species removals on soil and plant nitrogen and phosphorus across a retrogressive chronosequence

• Published in: Journal of Ecology
• Main Authors: Wardle, David, Gundale, Michael, Kardol, Paul, Nilsson, Marie‐Charlotte, Fanin, Nicolas
• Other Authors: Nanyang Technological University Singapour, Swedish University of Agricultural Sciences (SLU), Interactions Sol Plante Atmosphère (UMR ISPA), Ecole Nationale Supérieure des Sciences Agronomiques de Bordeaux-Aquitaine (Bordeaux Sciences Agro)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2020
• Subjects: Retrogression; Succession végétale; Boreal forests; Chronosequences; Environmental gradients; Nitrogen N; Phosphorus P; Removal experiment; [SDV.EE]Life Sciences [q-bio]/Ecology; environment; Northern Sweden
• Online Access: https://hal.inrae.fr/hal-02527321; https://doi.org/10.1111/1365-2745.13283

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 ...