Tree species composition affects productivity and carbon dynamics of different site types in boreal forests

Vladimir Shanin,Alexander Komarov,Raisa Mäkipää

doi:10.1007/s10342-013-0759-1

Abstract

AbstractThe objective was to analyse how differences in the initial proportions of tree species and site fertility affect carbon sequestration in living biomass and soil. We used the individual-based simulation model EFIMOD, which is able to simulate spatially explicit competition between trees for light and nutrients. Simulations were carried out for three site types with distinct initial stocks of soil nutrients. For each site, the 100-years undisturbed dynamics of monocultures and mixtures of three tree species (Betula pendulaRoth,Pinus sylvestrisL. andPicea abies(L.) H. Karst.) was predicted. Changes in the proportions of competing tree species were dependent on the fertility of the site: on poor sites, pine was the most competent species, while on rich sites, spruce increased its proportion during stand succession. Net primary production (NPP) and soil respiration were the highest in stands of two coniferous species and in stands with a high initial proportion of pine. Mixed stands were more productive than monocultures; the highest overyielding was observed with mixtures of two coniferous species. Simulated NPP and carbon stocks in all pools increased from poor to rich sites. The highest carbon stocks in standing biomass were observed for mixtures of conifer species and three-species mixtures; the greatest accumulation of forest floor occurred in stands with high proportions of pine.

Highlights

In natural ecosystems, plant species grow in mixtures of interacting species and net biomass production is affected by species composition (e.g. Pretzsch 2010; Pretzsch and Schutze 2009)
Changes in the proportions of competing tree species were dependent on the fertility of the site: on poor sites, pine was the most competent species, while on rich sites, spruce increased its proportion during stand succession
To assess the dynamics of forest ecosystems depending on initial species composition and site type, we analysed several key characteristics obtained from outputs of simulations, which were as follows: changes in species composition, amount of carbon in different pools, amount of nitrogen in forms available for nutrition and overall productivity of mixed forest stands

Summary

Introduction

Plant species grow in mixtures of interacting species and net biomass production is affected by species composition (e.g. Pretzsch 2010; Pretzsch and Schutze 2009). Pretzsch and Schutze 2009; Morin et al 2011; Forrester et al 2013), but less comprehensively in boreal forests where management has favoured monocultures. Paquette and Messier (2011) suggested that species richness has more significant influence on productivity in stressful and less diversified boreal forests than in temperate biome. Tree species richness in boreal forests tends to have positive influence on biomass production (Gamfeldt et al 2013). This seems to be the case in stands with spruce–birch mixtures (Mielikainen 1985; Jogiste 2000), but not necessarily with all other combinations and proportions of boreal tree species.

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