Soil carbon and nutrient stocks under Scots pine plantations in comparison to European beech forests: a paired-plot study across forests with different management history and precipitation regimes

Marco Diers,Robert Weigel,Christoph Leuschner,Heike Culmsee

doi:10.1186/s40663-021-00330-y

Abstract

BackgroundOrganic carbon stored in forest soils (SOC) represents an important element of the global C cycle. It is thought that the C storage capacity of the stable pool can be enhanced by increasing forest productivity, but empirical evidence in support of this assumption from forests differing in tree species and productivity, while stocking on similar substrate, is scarce.MethodsWe determined the stocks of SOC and macro-nutrients (nitrogen, phosphorus, calcium, potassium and magnesium) in nine paired European beech/Scots pine stands on similar Pleistocene sandy substrates across a precipitation gradient (560–820 mm∙yr− 1) in northern Germany and explored the influence of tree species, forest history, climate, and soil pH on SOC and nutrient pools.ResultsWhile the organic layer stored on average about 80% more C under pine than beech, the pools of SOC and total N in the total profile (organic layer plus mineral soil measured to 60 cm and extrapolated to 100 cm) were greater under pine by about 40% and 20%, respectively. This contrasts with a higher annual production of foliar litter and a much higher fine root biomass in beech stands, indicating that soil C sequestration is unrelated to the production of leaf litter and fine roots in these stands on Pleistocene sandy soils. The pools of available P and basic cations tended to be higher under beech. Neither precipitation nor temperature influenced the SOC pool, whereas tree species was a key driver. An extended data set (which included additional pine stands established more recently on former agricultural soil) revealed that, besides tree species identity, forest continuity is an important factor determining the SOC and nutrient pools of these stands.ConclusionWe conclude that tree species identity can exert a considerable influence on the stocks of SOC and macronutrients, which may be unrelated to productivity but closely linked to species-specific forest management histories, thus masking weaker climate and soil chemistry effects on pool sizes.

Highlights

Organic carbon stored in forest soils (SOC) represents an important element of the global C cycle
We present the results of a country-wide study on the soil C and nutrient stocks in paired beech and pine stands along a climate gradient in the Pleistocene lowlands of northern Germany, spanning from the North Sea coast to the Polish border
As recent pine stands, established on sites with former agricultural or heathland use, are more widespread in the study region than ancient pine stands with longer forest continuity, we extended our stand sample by including data from 7 recent pine forests on similar soil in western Brandenburg, and tested for the combined effect of stand type and forest continuity in a similar testing procedure

Summary

Introduction

Organic carbon stored in forest soils (SOC) represents an important element of the global C cycle. Soil organic C (SOC) storage depends on climate (Lorenz & Lal 2010) and mineral properties, notably the potential of soils to stabilize organic C on reactive mineral surfaces (Vogel et al 2015), but it may be influenced by tree species identity and forest management (Binkley & Giardina 1998; Jandl et al 2007; Grüneberg et al 2019). Tree species differences in litter properties should be large between angiosperm and gymnosperm trees, as the latter produce needles that are generally poorer in N and Ca than leaves of broad-leaved trees (Berg & McClaugherty 2003; Hobbie et al 2006), and conifers are often more shallow-rooted than many angiosperm trees (Polomski & Kuhn 1998), with possible consequences for root-borne C input. In the debate about how temperate production forests of the future should look like, this understanding is needed for comparing the impact of conifers, which are widely planted in monocultures and valued in forestry for their timber productivity and economic value, and native hardwood trees, which may have advantages in terms of biodiversity conservation, lower soil acidification potential and lower susceptibility to insect attack (Ammer et al 2008; Gessler et al 2006)

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