Antoine G. Jongmans

Do plants drive podzolization via rock-eating mycorrhizal fungi?

Weathering and supply of nutrients derived from minerals to plants is known to be stimulated by plant symbiotic mycorrhizal fungi. Nutrients are generally thought to pass the bulk soil solution bef ...

Calcium weathering in forested soils and the effect of different tree species

Soil weathering can be an important mechanism to neutralize acidity inforest soils. Tree species may differ in their effect on or response to soilweathering. We used soil mineral data and the natural strontium isotope ratio87Sr/86Sr as a tracer to identify the effect of treespecies on the Ca weathering rate. The tree species studied were sugar maple(Acer saccharum), hemlock (TsugaCanadensis), American beech (Fagusgrandifolia),red maple (Acer rubrum), white ash (FraxinusAmericana) and red oak (Quercus rubra) growingin a forest in northwestern Connecticut, USA. Three replicated sites dominatedby one of the six tree species were selected. At sugar maple and hemlock sitesthe dominant mineral concentrations were determined at three soil depths. Ateach site soil, soil water and stem wood of the dominant tree species weresampled and analyzed for the 87Sr/86Sr ratio, total SrandCa content. Atmospheric deposition was collected and analyzed for the sameconstituents. Optical analysis showed that biotite and plagioclaseconcentrations were lower in the soil beneath hemlock than beneath sugar mapleand suggested species effects on mineral weathering in the upper 10cm of the mineral soil. These results could not be confirmed withdata obtained by the Sr isotope study. Within the sensitivity of the Sr isotopemethod, we could not detect tree species effects on Ca weathering andcalculatedCa weathering rates were low at all sites (< 60mg m−2 yr−1). Wefound a positive correlation between Ca weathering and the total Caconcentration in the surface soil. These results indicate that the absolutedifferences in Ca weathering rate between tree species in these acidic surfacesoils are small and are more controlled by the soil parent material(plagioclasecontent) than by tree species.

Mineralogy of a soil chronosequence on andesitic lava in humid tropical Costa Rica

Abstract We studied a chronosequence of three soils developed on andesitic lavas in humid tropical Costa Rica, in order to investigate mineralogical development and to evaluate the importance of time versus other soil forming factors. Morphological, chemical, and mineralogical methods were used to unravel evolution of the soils. Primary minerals in the

Feldspar Tunneling by Fungi along Natural Productivity Gradients

AbstractRecently, it was hypothesized that ectomycorrhizas hyphae are involved in mineral tunneling. We evaluated the role of ectomycorrhizas in mineral weathering and the ecosystem influx of basic cations by correlating mineral tunnel density to ectomycorrhizas density in two forest productivity gradients. The gradients, two gentle slopes in northern Sweden, are the result of groundwater movement and are characterized by reduced productivity upslope due to lower nitrogen availability. As expected, ectomycorrhizas density in the O horizon was higher upslope, where nitrogen availability was lower and where the vegetation was dominated by ectomycorrhizas plant species. We consistently found that tunnel formation in mineral grains was more intense in nutrient-poor sites, indicating a higher contribution of fungi to ecosystem influx of potassium and calcium. ectomycorrhizas density was positively correlated with feldspar tunnel density in the upper 2 cm of the E horizon. This suggests that ectomycorrhizas are involved in mineral tunneling. We discuss the possible involvement of ericoid mycorrhizas and saprotrophic fungi in feldspar tunneling and the role of the weathering status of mineral grains as additional factors controlling mineral funneling.

Andisol formation in a Holocene beach ridge plain under the humid tropical climate of the Atlantic coast of Costa Rica

Abstract Soil formation has been studied in relation with time in a 5000-year old chronosequence on volcaniclastic beach ridges of the perhumid tropical Atlantic coast of Costa Rica. All soils are under tropical rainforest. Drainage conditions change by subsidence from excessively drained in the two youngest soils to imperfectly drained in the two oldest soils. Parent material is rather homogeneous andesitic sand with a volcanic glass component of less than 10%. It has been found that under these conditions Andisols form within 2000 years. Imperfect drainage caused mottling and accumulation of iron-coatings, as well as the formation of a thin O-horizon in the oldest profiles. Sand content of the soils decreases regularly with soil age, while the amount of fine material increases concurrently. The increase in fine material and the accumulation of organic matter cause an increase of CEC and andic properties, and a decrease in bulk density and pH with soil age. Depth of biological influence increases with soil age, but soil faunal activity is hampered in the oldest three profiles, probably by imperfect drainage. Due to the extreme leaching conditions, the sum of exchangeable cations is less than 2 cmol + kg−1 in the B-horizons of the older soils, notwithstanding the presence of a considerable amount of weatherable primary minerals.