Soil [N] modulates soil C cycling in CO₂‐fumigated tree stands: a meta‐analysis

Abstract

Under elevated atmospheric CO(2) concentrations, soil carbon (C) inputs are typically enhanced, suggesting larger soil C sequestration potential. However, soil C losses also increase and progressive nitrogen (N) limitation to plant growth may reduce the CO(2) effect on soil C inputs with time. We compiled a data set from 131 manipulation experiments, and used meta-analysis to test the hypotheses that: (1) elevated atmospheric CO(2) stimulates soil C inputs more than C losses, resulting in increasing soil C stocks; and (2) that these responses are modulated by N. Our results confirm that elevated CO(2) induces a C allocation shift towards below-ground biomass compartments. However, the increased soil C inputs were offset by increased heterotrophic respiration (Rh), such that soil C content was not affected by elevated CO(2). Soil N concentration strongly interacted with CO(2) fumigation: the effect of elevated CO(2) on fine root biomass and -production and on microbial activity increased with increasing soil N concentration, while the effect on soil C content decreased with increasing soil N concentration. These results suggest that both plant growth and microbial activity responses to elevated CO(2) are modulated by N availability, and that it is essential to account for soil N concentration in C cycling analyses.

Fluctuations in the properties of forest soils in the Central European highlands (Czech Republic)

“…The increase in N tot is a possible consequence of eutrophication. The increase in C org is a possible consequence of humus restoration (Dieleman et al 2010). The slight trend of increase in the content of C org indicated that it might refer to a reliable medium-term prediction but repeated occurrence of unusual values due to the uncertain quality of sampling probably influenced the reduction of the probable development prediction length to five years.…”

“…Fluctuations in soil carbon cycles mainly occur due to changes in the balance between above-ground and underground resources (Wang et al 2012). Nevertheless, to specifically estimate soil property changes requires the formulation of models that assume the influence and synergy of both acid deposition and climatic changes (Dieleman et al 2010).…”

Environmental change impacts on the C- and N-cycle of European forests: a model comparison study

“…Indeed Luyssaert et al (2010) suggested that forests continue to sequester carbon in spite of intensive harvesting of wood since growth has outpaced losses from harvesting and heterotrophic respiration. This increase in growth has been attributed to a large fraction of young productive trees (Nabuurs et al, 2003), changes in management and increase in forest area (Ciais et al, 2008), increased CO 2 (Friedlingstein et al, 1995) and temperature (Myneni et al, 1997).…”

Response of Fagus sylvatica and Picea abies to the interactive effect of neighbor identity and enhanced CO2 levels

“…However, the fertilization effect of CO 2 may be limited by the progressive scarcity of nutrient supplies, especially N (Reich et al 2006;Dieleman et al 2010) or by a lack of positive growth response despite the stimulation of the C assimilation rate induced by CO 2 (Körner 2006;Kirschbaum 2011). Additionally, in natural conditions, the response of an individual can depend on the identity of neighboring species (Lau et al 2010) because processes affecting growth, such as nutrient acquisition, can be contingent on the identity of neighboring species under enhanced levels of CO 2 (Friend et al 2000;Zak et al 2012).…”