Wood decomposition by microbes and macroinvertebrates, and soil CO2 efflux vary in response to throughfall reduction and fertilization in a loblolly pine (Pinus taeda L.) plantation

•Wood decomposition near planted trees was greater than any other location.•Fertilization increased macro-invertebrate tunnels and overall wood mass loss.•Fertilization inhibited soil CO2 efflux and wood mass loss caused only by microbes.•Wood mass loss was slower inside soil CO2 efflux collars.•Throughfall reduction reduced wood mass loss and occasionally soil CO2 efflux. Climate and nutrient availability modify the rate of carbon loss from soil and detrital pools in forest ecosystems. In a managed loblolly pine (Pinus taeda L.) plantation, we examined how reduced throughfall and fertilization affected wood decomposition and soil CO2 efflux. For ∼1.5years, soil CO2 efflux and the mass loss of Pinus wood sticks were examined in relation to soil temperature and moisture and the accumulation of soil NH4+ and NO3− for a factorial combination of two treatments: a 30% throughfall reduction (TR) treatment, fertilization with nutrient additions typical for this plantation type (224kg/ha N, 64kg/ha P and 67kg/ha K), and a combined treatment. Wood mass loss was estimated separately for substrates affected by only microbes and those with visual signs (e.g. tunnels) of macroinvertebrate consumption. For the 426days of the experiment, wood sticks decomposed only by microbes lost 3–6% of their mass while those also tunneled by macroinvertebrates lost 35–45% of their mass. By the end of the study macroinvertebrates had tunneled into 54% of all sticks across treatments. Because of macroinvertebrates, fertilization increased wood decomposition overall, despite significantly lower decomposition occurring in fertilized plots for sticks only decomposed by microbes. The TR treatment decreased wood decomposition but there was an interaction with location, where inhibition occurred near trees and under throughfall excluders but not at the midpoint between two planted rows. Wood sticks placed inside a collar used to measure soil CO2 efflux also decomposed significantly slower than all other locations. Soil CO2 efflux was inhibited by fertilization, primarily in August when temperatures were at the annual maximum. The depressed soil CO2 efflux from fertilization may have been the result of increased N availability, as fertilization stimulated NO3− production. The main effect of TR on soil CO2 efflux or N availability was not significant, but the TR effect on soil CO2 efflux interacted with time, reflecting generally lower efflux on different dates relative to non-TR treatments. T