Slow soil enzyme recovery following invasive tree removal through gradual changes in bacterial and fungal communities

1. Biological invasions of plants have profound effects on ecosystem functioning by directly and indirectly altering soil microbiota, especially when invasive plants co-invade with their associated microbiomes. Ecosystem functions may recover slowly following invader removal, with implications for restoration. 2. We investigated the recovery of soil ecosystem function (measured as soil enzymes) following the removal, at different densities and times, of invasive Pinus spp. in New Zealand, and how different enzymatic activities responded to pine legacies. 3. Enzymatic activities were driven by pine legacies via both abiotic (soil nutrients) and biotic (fungi and bacteria) soil properties, with different enzymes showing distinct patterns. The activity of the enzymes cellobiohydrolase (cellulose degrading), beta-glucosidase (cellulose degrading), N-acetyl-glucosaminidase (chitin degrading), laccase (lignin oxidising) and acid phosphatase (organic phosphate hydrolysing) were influenced by time since pine removal and by pine density at removal via effects on biotic communities. In comparison, Mn-peroxidase (lignin oxidising) was positively correlated with density of pines at removal and was negatively correlated with time since removal and was only influenced by fungal communities. 4. Synthesis. The recovery of soil enzymatic function following invasive species removal is slow and dependent on pine legacies through the gradual changes in fun- gal and bacterial communities. The cascading effects of these changes suggest potential implications for the success of future plant establishment and restoration of co-invaded ecosystems.

Automated summary

Biological invasions of plants have significant effects on ecosystem functioning by altering soil microbiota. This study investigated the recovery of soil enzymatic function following the removal of invasive Pinus spp. in New Zealand. The results showed that soil enzymatic activities were influenced by pine legacies through changes in soil properties and biotic communities. The slow recovery of enzymatic function may have implications for plant establishment and ecosystem restoration.