The long-term impact of low-intensity surface fires on litter decomposition and enzyme activities in boreal coniferous forests

Abstract

In boreal forest ecosystems fire, fungi and bacteria, and their interactions, have a pronounced effect on soil carbon dynamics. In this study we measured enzymatic activities, litter decomposition rates, carbon stocks and fungal and microbial biomasses in a boreal subarctic coniferous forest on a four age classes of non-stand replacing fire chronosequence (2, 42, 60 and 152 years after the fire). The results show that microbial activity recovered slowly after fire and the decomposition of new litter was affected by the disturbance. The percent mass loss of Scots pine litter increased with time from the last fire. Slow litter decomposition during the first post-fire years accelerates soil organic matter accumulation that is essential for the recovery of soil biological activities. Fire reduced the enzymatic activity across all the enzyme types measured. Carbon-degrading, chitin-degrading and phosphorus-dissolving enzymes showed different responses with the time elapsed since the fire disturbance. Microbial and enzymatic activity took decades before recovering to the levels observed in old forest stands. Our study demonstrates that slower post-fire litter decomposition has a pronounced impact on the recovery of soil organic matter following forest fires in northern boreal coniferous forests.

How Time since Forest Fire Affects Stand Structure, Soil Physical-Chemical Properties and Soil CO2 Efflux in Hemiboreal Scots Pine Forest Fire Chronosequence?

“…In previous studies it has been found that the soil CO 2 efflux is lower in recently burned areas and higher in the areas where more time has elapsed since the last fire [13,[33][34][35]. Similarly, this study revealed that soil respiration was lowest in the area where the last fire occurred most recently in 2008.…”

The influence of repeated prescribed fire on decomposition and nutrient release in uneven-aged loblolly–shortleaf pine stands

“…Although several studies in a variety of forest ecosystems have found altered litter decomposition rates up to several years following low intensity fires (Raison et al 1986;Schoch and Binkley 1986;Monleon and Cromack 1996;Köster et al 2015), foliar litter deployed in the burn and control treatments in our study had similar mass loss and overall decay constants. Decomposition rates are strongly dependent on environmental conditions (Swift et al 1979;Berg and McClaugherty 2014) and fires that remove vegetation can increase insolation, which can increase temperatures and reduce litter moisture (Raison et al 1986;Hernández and Hobbie 2008).…”

“…Decomposition rates are strongly dependent on environmental conditions (Swift et al 1979;Berg and McClaugherty 2014) and fires that remove vegetation can increase insolation, which can increase temperatures and reduce litter moisture (Raison et al 1986;Hernández and Hobbie 2008). Decomposition rates can be reduced as a result of the reduction in litter moisture that occurs with the removal of vegetation or forest floor by fire (Raison et al 1986;Köster et al 2015) as well as other cultural treatments (Gurlevik et al 2003).…”

Proximity to charred logs in burned forests likely affects decomposition processes in the soil

“…For instance, Finér et al (2016) showed that a higher soil temperature sum enhanced decomposition in clear-cut boreal forests and that it was hindered by reduced moisture rates. Soil microbial activity is lowered for a considerable time after burning (Köster et al 2015), and Suominen et al (2018) found that burned stumps harbour different fungal species than unburned stumps, which could also affect decomposition rates. Such mechanisms could potentially be affected by small-scale differences in burning severity and its impacts on the soil microsites with respect to CWD pieces.…”