Effects of persistent water-table level drawdown on fine-root biomass and production in different site types of a boreal forested peatland

Abstract

Purpose In peatlands, fine-root biomass (FRB) and production (FRP) and their depth distribution and plant functional type (PFT) composition are poorly known. We studied the effects of persistent water-table level drawdown on these characteristics in four forested boreal peatland site types that varied in soil nutrient and WTL regimes, ground vegetation and tree stand characteristics. Methods FRB was estimated by separating and visually identifying roots from soil cores extending down to 50-cm depth. FRP was estimated using ingrowth cores covering the same depth and the separated roots were identified using infrared spectroscopy. Results In both FRB and FRP, the differences between undrained and drained sites were small. In FRB, the clearest differences were seen in the originally wettest site, oligotrophic tall-sedge pine fen, and in the most-nutrient-rich site, herb-rich spruce swamp: in the pine fen FRB was smaller, and in the spruce swamp greater in the drained than in the undrained site. FRP was generally higher in nutrient-poor, pine-dominated sites. The depth distribution of FRB was more superficial than that of FRP, except for the most nutrient-rich spruce swamp. Tree and shrub roots dominated both FRB and FRP, except for the undrained pine fen, where graminoids and forbs dominated. Even there, these PFTs were replaced by trees and shrubs at the drained site. Conclusion Fine-root biomass and production vary widely both within and among different types of boreal forested peatlands. Lowering of WTL large enough to support greater-volume tree stands affects FRB and FRP relatively little.

Fine root morphological traits and production in coniferous- and deciduous-tree forests with drained and naturally wet nutrient-rich organic soils in hemiboreal Latvia

“…Finér et al (2011) estimated that average production of fine roots for all plants (trees + understorey) in boreal and temperate forest ecosystems was 3.11 ± 2.59 t ha -1 yr -1 and 4.28 ± 3.75 t ha -1 yr -1 , respectively; however, mineral and organic (peatland) soils were not analysed separately. Lampela et al (2022) found that average fine root production in boreal forested peatland varied from 0.31 t ha -1 yr -1 to 1.20 t ha -1 yr -1 ; furthermore, there were no significant differences in total fine root production between the undrained and drained sites. Our estimates in forests with nutrient-rich organic soils showed that average fine root production ranged from 0.46 ± 0.15 t ha -1 yr -1 in deciduous-trees-dominated stands with drained organic soils to 0.69 ± 0.08 t ha -1 yr -1 in Norway spruce dominated stands with drained organic soils.…”

“…In general, fine root production varies widely both within and among different types of boreal forests with organic soils (Lampela et al 2022). Yuan & Chen (2010) estimated that the average production of fine roots (< 2 mm in diameter) in boreal forest ecosystems was 2.83 t ha -1 yr -1 (both mineral and organic soils were included).…”

“…Several studies have demonstrated that fine root production is inversely related to soil nutrient status (Borja et al 2008, Ding 2021 and N deposition (Wang et al 2019, Zhu et al 2021. Studies along boreal and temperate forest ecosystems showed that fine root biomass per tree stand basal area decreases significantly from nutrient-poor to nutrient-rich sites (Nadelhoffer 2000, Ding et al 2021, Lampela et al 2022).…”

“…Fine root net primary production constitutes an important but often insufficiently measured part of the C budget of forest ecosystems because below-ground litter C input is more laborious to quantify (Helmisaari et al 2007, Leppälammi-Kujansuu et al 2014. A better understanding of the factors affecting fine root production, especially in forests with nutrient-rich organic soils, which are considered to be a significant source of GHG emissions, is important for improving national-, regional-, and global-level C cycling models for forest ecosystems, and one of the approaches for gaining information is the collection of new empirical data (Finér et al 2011, Lampela et al 2022.…”