Major and persistent shifts in below‐ground carbon dynamics and soil respiration following logging in tropical forests

Abstract

Soil respiration is the largest carbon efflux from the terrestrial ecosystem to the atmosphere, and selective logging influences soil respiration via changes in abiotic (temperature, moisture) and biotic (biomass, productivity, quantity and quality of necromass inputs) drivers. Logged forests are a predominant feature of the tropical forest landscape, their area exceeding that of intact forest. We quantified both total and component (root, mycorrhiza, litter, and soil organic matter, SOM) soil respiration in logged (n = 5) and old‐growth (n = 6) forest plots in Malaysian Borneo, a region which is a global hotspot for emission from forest degradation. We constructed a detailed below‐ground carbon budget including organic carbon inputs into the system via litterfall and root turnover. Total soil respiration was significantly higher in logged forests than in old‐growth forests (14.3 ± 0.23 and 12.7 ± 0.60 Mg C ha−1 year−1, respectively, p = 0.037). This was mainly due to the higher SOM respiration in logged forests (55 ± 3.1% of the total respiration in logged forests vs. 50 ± 3.0% in old‐growth forests). In old‐growth forests, annual SOM respiration was equal to the organic carbon inputs into the soil (difference between SOM respiration and inputs 0.18 Mg C ha−1 year−1, with 90% confidence intervals of −0.41 and 0.74 Mg C ha−1 year−1), indicating that the system is in equilibrium, while in logged forests SOM respiration exceeded the inputs by 4.2 Mg C ha−1 year−1 (90% CI of 3.6 and 4.9 Mg C ha−1 year−1), indicating that the soil is losing carbon. These results contribute towards understanding the impact of logging on below‐ground carbon dynamics, which is one of the key uncertainties in estimating emissions from forest degradation. This study demonstrates how significant perturbation of the below‐ground carbon balance, and consequent net soil carbon emissions, can persist for decades after a logging event in tropical forests.

Understory plant removal counteracts tree thinning effect on soil respiration in a temperate forest

“…Forest management practices (e.g. thinning and understory plant removal) can inevitably affect Rs and its components by altering environments in plantation forests (Dean et al, 2017;Johnson & Curtis, 2001;Riutta et al, 2018Riutta et al, , 2021. Thinning, which is defined as partial removal of trees, is a primary management practice for improving the growth of the remained trees.…”

Upscaling tropical restoration to deliver environmental benefits and socially equitable outcomes

“…In Indonesian Borneo, planting of nursery-raised dipterocarp seedlings along cleared strips within twice-logged forests returned old-growth timber volumes within 40 years 18 , while in Malaysian Borneo, intensive liana cutting and enrichment planting boosted recovery rates of aboveground carbon over 50% (2.9-4.4 MgC ha À1 yr À1 ) relative to naturally regenerating logged forests 19 (Figures 1C and 3A). Given persistent losses of soil carbon post-logging (reaching 4.9 MgC ha À1 yr À1 ) 20 , how different restoration options influence soil carbon is a major unknown.…”

Optimizing stand density for climate-smart forestry: A way forward towards resilient forests with enhanced carbon storage under extreme climate events

“…Partial tree harvesting generally limits soil carbon losses compared to clear-cut harvesting (James and Harrison, 2016;Lull et al, 2020;Nave et al, 2010;Riutta et al, 2021), and can even lead to an increase in the amount of soil organic carbon compared to a non-logging situation (Gong et al, 2021;Mayer et al, 2020;Zhang et al, 2018). Positive effects of partial tree harvesting on soil carbon storage are often mediated by reduced soil disturbances or a higher amount of tree residues left on site (Jandl et al, 2007).…”