Carbon sequestration in forest soils: effects of soil type, atmospheric CO₂ enrichment, and N deposition

Abstract

Summary Soil contains the major part of carbon in terrestrial ecosystems, but the response of this carbon to enriching the atmosphere in CO2 and to increased N deposition is not completely understood. We studied the effects of CO2 concentrations at 370 and 570 μmol CO2 mol−1 air and increased N deposition (7 against 0.7 g N m−2 year−1) on the dynamics of soil organic C in two types of forest soil in model ecosystems with spruce and beech established in large open‐top chambers containing an acidic loam and a calcareous sand. The added CO2 was depleted in 13C and thus the net input of new C into soil organic carbon and the mineralization of native C could be quantified. Soil type was the greatest determining factor in carbon dynamics. After 4 years, the net input of new C in the acidic loam (670 ± 30 g C m−2) exceeded that in the calcareous sand (340 ± 40 g C m−2) although the soil produced less biomass. The mineralization of native organic C accounted for 700 ± 90 g C m−2 in the acidic loam and for 2800 ± 170 g C m−2 in the calcareous sand. Unfavourable conditions for mineralization and a greater physico‐chemical protection of C by clay and oxides in the acidic loam are probably the main reasons for these differences. The organic C content of the acidic loam was 230 g C m−2 more under the large than under the small N treatment. As suggested by a negligible impact of N inputs on the fraction of new C in the acidic loam, this increase resulted mainly from a suppressed mineralization of native C. In the calcareous sand, N deposition did not influence C concentrations. The impacts of CO2 enrichment on C concentrations were small. In the uppermost 10 cm of the acidic loam, larger CO2 concentrations increased C contents by 50–170 g C m−2. Below 10 cm depth in the acidic loam and at all soil depths in the calcareous sand, CO2 concentrations had no significant impact on soil C concentrations. Up to 40% of the ‘new’ carbon of the acidic loam was found in the coarse sand fraction, which accounted for only 7% of the total soil volume. This suggests that a large part of the CO2‐derived ‘new’ C was incorporated into the labile and easily mineralizable pool in the soil.

Soil Properties of a Tropical Savannah in the Eastern Ghats of India

“…The nutrients are largely interlinked and influenced by other physico-chemical characters of the soil, depending on seasonal changes [40]. Yankelevich et al [34] predicted that if each tree species generates a particular soil environment under its canopy, then under a diverse tree community, soil chemical properties will be spatially very heterogeneous.…”

Is Biomass Accumulation in Forests an Option to Prevent Climate Change Induced Increases in Nitrate Concentrations in the North German Lowland?

“…On the other hand, an increase in standing volume under the biodiversity scenario keeps NO 3 − concentrations low in three of the four model regions. In DH, the high N deposition and N release from soils with high organic matter stocks may not be compensated by the N uptake of the forest stands Several studies showed that the C sequestration rate of forest soils is increased under elevated N deposition [99][100][101], however, the efficiency of this effect differs considerably [102,103]. It may to some extent be accounted for in the VSD+ simulations where the foliar N content is dependent on N deposition.…”

Evaluating the Effects of Environmental Changes on the Gross Primary Production of Italian Forests

“…where K m is the affinity constant for CO 2 The original C-Fix does not include a specific index which accounts for the possible short-term effect of water stress on photosynthesis, as is done by other Monteith type models [e.g., 5,23]. The need to apply C-Fix also in Mediterranean environments, that are characterized by a long summer dry season during which vegetation growth is limited by water availability [24], induced Maselli et al [25] to include such an additional water stress index.…”

“…Among them, forest ecosystems cover about 40% of the Earth's ice-free land surface and represent a great part of the global carbon stock [1,2], which must be quantified also in view of the carbon emission trading by countries [3]. Worldwide forests account for about 75% of the carbon stored in terrestrial ecosystems (organic carbon, OC) and approximately 40% of the carbon exchange between the atmosphere and the terrestrial biosphere each year [4].…”