Erik Karltun

Advances in understanding the podzolization process resulting from a multidisciplinary study of three coniferous forest soils in the Nordic Countries

Advances in understanding the podzolisation process resulting from a multidisciplinary study at three coniferous forest soils in the Nordic countries

Surface reactivity of poorly-ordered minerals in podzol B horizons

The surface reactivity of mineral soil horizons from three podzolised forest soils in Scandinavia was examined. The amount of accumulated C was low, between 1.8 and 2.3% in the top of the B horizon ...

Mineralogy of poorly crystalline aluminium phases in the B horizon of Podzols in southern Sweden

Poorly crystalline Al components of the clay fraction are often neglected in soil mineralogical studies. In this study 7 B horizons from podzolised soils in Sweden were analysed using a combination of infrared (IR) spectroscopy, transmission electron microscopy (TEM), X-ray diAraction (XRD) and selective extractions. It was found that most Bhs and Bs horizons contained allophane, imogolite and more or less hydroxy-interlayered vermiculite. Some Bhs and Bs horizons also contained small amounts of kaolinite and/or gibbsite. In one acid Bh horizon organically complexed Al was the only reactive Al fraction of importance. The vertical patterns of vermiculite and allophane/imogolite suggested that both had formed during the podzolisation process, but due to diAerent mechanisms. The pattern of kaolinite and gibbsite occurrences indicated that these minerals were mostly inherited from the parent material. Oxalate and pyrophosphate extractions suggested that allophane and imogolite constituted the most important reactive inorganic Al fraction in the soils. This shows that allophane and imogolite seem to be the typical, rather than the occasional, reactive inorganic Al phases that form in the B horizon as a result of podzolisation. # 1999 Elsevier Science Ltd. All rights reserved.

Shift in fungal communities and associated enzyme activities along an age gradient of managed Pinus sylvestris stands

Forestry reshapes ecosystems with respect to tree age structure, soil properties and vegetation composition. These changes are likely to be paralleled by shifts in microbial community composition with potential feedbacks on ecosystem functioning. Here, we assessed fungal communities across a chronosequence of managed Pinus sylvestris stands and investigated correlations between taxonomic composition and extracellular enzyme activities. Not surprisingly, clear-cutting had a negative effect on ectomycorrhizal fungal abundance and diversity. In contrast, clear-cutting favoured proliferation of saprotrophic fungi correlated with enzymes involved in holocellulose decomposition. During stand development, the re-establishing ectomycorrhizal fungal community shifted in composition from dominance by Atheliaceae in younger stands to Cortinarius and Russula species in older stands. Late successional ectomycorrhizal taxa correlated with enzymes involved in mobilisation of nutrients from organic matter, indicating intensified nutrient limitation. Our results suggest that maintenance of functional diversity in the ectomycorrhizal fungal community may sustain long-term forest production by retaining a capacity for symbiosis-driven recycling of organic nutrient pools.

Partitioning of base cations and sulphate between solid and dissolved phases in three podzolised forest soils.

The cation and SO, adsorption properties of O and B horizons of three podzolised soils in Sweden and Finland were studied through analysing the soil solution at six different sampling occasions and ...

Below-ground organic matter accumulation along a boreal forest fertility gradient relates to guild interaction within fungal communities

Plant-soil interactions link ecosystem fertility and organic matter accumulation below ground. Soil microorganisms play a central role as mediators of these interactions, but mechanistic understanding is still largely lacking. Correlative data from a coniferous forest ecosystem support the hypothesis that interactions between fungal guilds play a central role in regulating organic matter accumulation in relation to fertility. With increasing ecosystem fertility, the proportion of saprotrophic basidiomycetes increased in deeper organic layers, at the expense of ectomycorrhizal fungal species. Saprotrophs correlated positively with the activity of oxidative enzymes, which in turn favoured organic matter turnover and nitrogen recycling to plants. Combined, our findings are consistent with a fungus-mediated feedback loop, which results in a negative correlation between ecosystem fertility and below-ground carbon storage. These findings call for a shift in focus from plant litter traits to fungal traits in explaining organic matter dynamics and ecosystem fertility in boreal forests.

The determination of adsorbed sulfate with isotopic dilution of sulfur (35S) compared with calcium dihydrogen phosphate extraction

Abstract A method using isotopic dilution of carrier‐free sulfur (35S) for determining adsorbed sulfate (SO4 2‐) in soil samples from B horizons of podsolized soils was compared with an extraction of SO4 2‐ by 10 mM calcium dihydrogen phosphate [Ca(H2PO4)2]. The two methods gave comparable results for flesh soil samples while the extraction method resulted in significantly higher amounts of adsorbed SO4 2‐ when using air‐dried samples. Since the 35S method assumes equilibrium between adsorbed SO4 2‐ and SO4 2‐ in solution, these results are evidence of complete exchangeability of adsorbed SO4 2‐ extracted with Ca(H2PO4)2 in fresh soil samples. It was thus concluded that the extraction method is a useful method when determining adsorbed SO4 2‐ in equilibrium with the soil solution in these soils. The 35S reached equilibrium with the soil solution within 2 h. The difference between the methods when using air‐dried samples indicates that part of the adsorbed SO4 2‐ is irreversibly bound to the soil during ai...

Nitrogen and carbon interactions between boreal soils and lakes

In this study, we used a large data set on nitrogen (N) and carbon (C) from Swedish boreal soils and lake waters to investigate N and C interactions between soils and lake waters. To link thousands ...

Crop Theft and Soil Fertility Management in the Highlands of Ethiopia

Theft of crops in rural areas is largely attributed to poverty and hunger. Crop theft has the consequence of soil fertility management being vastly impaired, a possible association examined by very few studies. The emphasis of most soil fertility studies has been on the effect of biophysical conditions and economics, which are the lack of capability of farmers as well as the failure of macro-economic policies to support good soil fertility management practices. The challenges that farmers face at the individual, household and community levels, as well as the barriers hampering farmers from practicing adequate soil fertility management, are still poorly understood. We need to extend our thinking beyond contextual issues of poverty, hunger, climate and seasonality to acquire a more nuanced understanding of food security in transforming rural agrarian societies. This study investigated the role of crop theft, particularly of legume bean crops, and its impact on soil fertility management. The results revealed that crop theft of legume bean crops deteriorated local intercropping and crop rotation soil fertility management practices. Crop theft had serious consequences on other socio-economic and cultural aspects of day-to-day life that deteriorated human relationships and eroded trust.