TY - JOUR

T1 - Effect of ash application on the decomposer food web and N mineralization in a Norway spruce plantation

AU - Mortensen, Louise Hindborg

AU - Cruz-Paredes, Carla

AU - Qin, Jiayi

AU - Rønn, Regin

AU - Vestergård, Mette

PY - 2020

Y1 - 2020

N2 - In the face of global climate change there is an increasing demand for biofuel, which exerts pressure on production and thus management of biofuel plantations. The intensification of whole-tree harvest from biofuel plantations increases export of nutrients. Returning ash from biofuel combustion to the forest plantations can amend the soil nutrient status and thus facilitate sustainable forest management. However, ash affects the forest floor decomposer food web, potentially changing organic matter turnover, carbon sequestration and nitrogen availability. Our aim was to examine the response of decomposer organisms, food web structure and nitrogen mineralization function after ash application. In a coniferous forest plantation amended with 0, 3, 4.5 or 6 t ash ha− 1, we sampled in several depths of the forest floor for key organisms of the decomposer food web (fungal biomass, 0–12 cm; bacteria, protozoa, nematodes and enchytraeids, 0–3 cm and 3–6 cm; microarthropods and earthworms, 0–5 cm), 2, 14 and 26 months after ash application. We used structural equation modelling (SEM) to detangle the direct and indirect effects of ash application on organisms in the decomposer food web and on nitrogen availability. We found that ash increased the abundance of bacteria and protozoa, as well as the inorganic nitrogen pool at 0–3 cm depth, whereas the effect of ash was negligible at 3–6 cm depth. Earthworm abundance increased, whereas enchytraeid abundance decreased 2 years after ash application. The structural equation modelling showed that ash application stimulated the bacterial feeding pathway and increased nitrogen mineralization. Contrary, ash had a negative effect on fungal biomass at the first sampling, however, this effect subdued over time. Our results suggest that as the soil decomposer food web is resilient to ash application, this is a viable option for sustainable management of biofuel plantations.

AB - In the face of global climate change there is an increasing demand for biofuel, which exerts pressure on production and thus management of biofuel plantations. The intensification of whole-tree harvest from biofuel plantations increases export of nutrients. Returning ash from biofuel combustion to the forest plantations can amend the soil nutrient status and thus facilitate sustainable forest management. However, ash affects the forest floor decomposer food web, potentially changing organic matter turnover, carbon sequestration and nitrogen availability. Our aim was to examine the response of decomposer organisms, food web structure and nitrogen mineralization function after ash application. In a coniferous forest plantation amended with 0, 3, 4.5 or 6 t ash ha− 1, we sampled in several depths of the forest floor for key organisms of the decomposer food web (fungal biomass, 0–12 cm; bacteria, protozoa, nematodes and enchytraeids, 0–3 cm and 3–6 cm; microarthropods and earthworms, 0–5 cm), 2, 14 and 26 months after ash application. We used structural equation modelling (SEM) to detangle the direct and indirect effects of ash application on organisms in the decomposer food web and on nitrogen availability. We found that ash increased the abundance of bacteria and protozoa, as well as the inorganic nitrogen pool at 0–3 cm depth, whereas the effect of ash was negligible at 3–6 cm depth. Earthworm abundance increased, whereas enchytraeid abundance decreased 2 years after ash application. The structural equation modelling showed that ash application stimulated the bacterial feeding pathway and increased nitrogen mineralization. Contrary, ash had a negative effect on fungal biomass at the first sampling, however, this effect subdued over time. Our results suggest that as the soil decomposer food web is resilient to ash application, this is a viable option for sustainable management of biofuel plantations.

KW - Decomposer food web

KW - Nitrogen mineralization

KW - Soil organisms

KW - Structural equation modelling

KW - Sustainable forest management

KW - Wood ash

U2 - 10.1016/j.scitotenv.2020.136793

DO - 10.1016/j.scitotenv.2020.136793

M3 - Journal article

C2 - 32007873

AN - SCOPUS:85078523317

VL - 715

JO - Science of the Total Environment

JF - Science of the Total Environment

SN - 0048-9697

M1 - 136793

ER -