Biotic and Abiotic Determinants of Soil Organic Matter Stock and Fine Root Biomass in Mountain Area Temperate Forests—Examples from Cambisols under European Beech, Norway Spruce, and Silver Fir (Carpathians, Central Europe)

Abstract

Forest ecosystems significantly contribute to the global organic carbon (OC) pool, exhibiting high spatial heterogeneity in this respect. Some of the components of the OC pool in a forest (woody aboveground biomass (wAGB), coarse root biomass (CRB)) can be relatively easily estimated using readily available data from land observation and forest inventories, while some of the components of the OC pool are very difficult to determine (fine root biomass (FRB) and soil organic matter (SOM) stock). The main objectives of our study were to: (1) estimate the SOM stock; (2) estimate FRB; and (3) assess the relationship between both biotic (wAGB, forest age, foliage, stand density) and abiotic factors (climatic conditions, relief, soil properties) and SOM stocks and FRB in temperate forests in the Western Carpathians consisting of European beech, Norway spruce, and silver fir (32 forest inventory plots in total). We uncovered the highest wAGB in beech forests and highest SOM stocks under beech forest. FRB was the highest under fir forest. We noted a considerable impact of stand density on SOM stocks, particularly in beech and spruce forests. FRB content was mostly impacted by stand density only in beech forests without any discernible effects on other forest characteristics. We discovered significant impacts of relief-dependent factors and SOM stocks at all the studied sites. Our biomass and carbon models informed by more detailed environmental data led to reduce the uncertainty in over- and underestimation in Cambisols under beech, spruce, and fir forests for mountain temperate forest carbon pools.

The distribution of carbon stocks between tree woody biomass and soil differs between Scots pine and broadleaved species (beech, oak) in European forests

“…While stands with low total BA always resulted in low stand-level C stocks in tree woody biomass, SOC stocks were independent of total stand BA. The negligible effects of BA on soil C relative to tree woody C across triplet types agree with our hypothesis (H1) and previous studies (Cécillon et al 2017 ; Laganiere et al 2010 ; Ruiz-Peinado et al 2013 ) but contradict others (González et al 2012 ; De Marco et al 2016 ; Zielonka et al 2021 ). Inconsistent results for BA effects on soil C could be because the balance between litter input and decomposition processes governs soil C storage (Liu et al 2018 ; Vesterdal et al 2013 ).…”

“…Stand density is another key factor that influence C accumulation in both aboveground woody biomass and coarse root biomass (Torres and Lovett 2013 ), and in the soil (Laganiere et al 2010 ; Zielonka et al 2021 ). Among silvicultural treatments, Ruiz-Peinado et al ( 2013 ) considers activities that alter stand density (such as regeneration felling and thinning) as those with the greatest impact on stand biomass and consequently the amount of C in the forest.…”

Which Are the Best Site and Stand Conditions for Silver Fir (Abies alba Mill.) Located in the Carpathian Mountains?

“…This is the case of calcic eutric cambisol, which has a higher presence in one of the causes of spreading valuable stands in this region [72]. On the other hand, lithic soils are not favourable for silver fir due to its taproot system [34,73,74]. In this contest, silver fir stands from the Southern Carpathians have lower productivities.…”

The early impact of mixed canopies with Norway spruce, European beech and silver fir on a new forest floor

“…When mixed, spruce root biomass did not differ from the pure spruce stand, whereas the presence of beech in mixtures showed a significantly higher specific root length and specific surface area of fine roots compared to pure beech stands (Bolte and Villanueva 2006). In the Western Carpathians, Zielonka et al (2021) found the highest levels of fine-root biomass below silver fir compared to Norway spruce and European beech. Despite the fact that beech stores less carbon in soil compared to maple and Communicated by Agustin Merino.…”

“…Spruce is a main Central European commercial species, whereas the most important conifer of the past-fir is very limited. These three trees accompany each other in different mixtures along a gradient from foothills to Alpine sites in Europe (Hilmers et al 2020;Filipiak et al 2021;Zielonka et al 2021). As European foresters are facing a decline of monocultures, the issue of mixed-species forest restoration has been raised.…”