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Phosphorus availability and microbial respiration across different tundra vegetation types
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, 901 83 Umeå, Sweden.
Department of Biology, NTNU, Høgskoleringen 5, 7491 Trondheim, Norway.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Phosphorus (P) is an important nutrient in tundra ecosystems that co-limits or in some cases limits primary production. The availability of P is largely driven by soil characteristics, e.g., pH, organic carbon, and abundance of P-sorbing elements such as aluminium (Al) or iron (Fe). We tested how vegetation and soil properties relate to P availability across different tundra vegetation types. The different soil P fractions in the organic top soil were measured and plant foliar nitrogen (N) to P ratio was used as an indicator of plant nutrient status. Microbial and plant bioassays were used to study microbial respiration kinetics and plant biomass response to carbon, N, and P amendments. The distribution of P fractions differed significantly across vegetation types; labile fractions of P were less abundant in meadow sites compared to heath sites. Calcium-phosphates seemed to be an important P-fraction in meadows, but were only found in lower concentrations in the heath. There were only small differences in sorbed P between the vegetation types and this corroborated with the distribution of Al+Fe. Plant N: P ratios and the plant bioassay indicated decreasing P availability from dry heath to mesic heath to mesic meadow. Our results showed that vegetation type was related to soil chemistry and P availability; however, in contrast to other studies, this effect was not related to redistribution of Fe and Al. We conclude that in this tundra ecosystem plants are generally co-limited by N and P, and P availability varies between different vegetation types, which is reflected in both above- and belowground ecosystem processes.

Keyword [en]
Phosphorus availability, subarctic tundra, Hedley fractionation, soil respiration
URN: urn:nbn:se:umu:diva-33736OAI: diva2:317687
Available from: 2010-05-04 Created: 2010-05-04 Last updated: 2010-05-06
In thesis
1. Phosphorus availability and microbial respiration across biomes:  from plantation forest to tundra
Open this publication in new window or tab >>Phosphorus availability and microbial respiration across biomes:  from plantation forest to tundra
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Phosphorus is the main limiting nutrient for plant growth in large areas of the world and the availability of phosphorus to plants and microbes can be strongly affected by soil properties. Even though the phosphorus cycle has been studied extensively, much remains unknown about the key processes governing phosphorus availability in different environments.

In this thesis the complex dynamics of soil phosphorus and its availability were studied by relating various phosphorus fractions and soil characteristics to microbial respiration kinetics. The soils used represent a range of aluminium, iron, carbon and total phosphorus content, and were located in four different biomes: subtropical forest, warm temperate forest, boreal forest and tundra.

The results showed that NaOH extractable phosphorus, a fraction previously considered to be available to plants only over long time scales, can be accessed by microbes in days or weeks. Microbial phosphorus availability was not related to aluminium or iron content in any of the studied systems, not even in highly weathered soils with high aluminium and iron content. This is in contrast with other studies of soils with high sorption capacity and shows the variability of factors that govern phosphorus availability in different environments.

In the boreal forest chronosequence, no difference could be seen with age in total phosphorus content or concentrations of occluded phosphorus forms. However, there were lower concentrations of labile phosphorus forms in older systems, which were correlated with a decrease in microbial respiration. This was most likely related to organic matter quality in the system, and not to geochemical factors.

Phosphorus availability was linked to differences in topography (water regime) and vegetation in the tundra ecosystems. The results suggest that the availability of phosphorus, both for microbes and plants, was lower on the meadow vegetation sites compared to the two types of heath vegetation.

Many factors are important for phosphorus availability in soils, but these results suggest that microbes can access less available phosphorus if not restricted by carbon, and this may be important in regard to forest management practices as well as effects of environmental change.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2010. 32 + 4 papers p.
phosphorus availability, microbial bioassay, soil respiration, microbial growth rate, Hedley fractionation, soil sorption, weathered soils, boreal forest, subarctic and tundra
urn:nbn:se:umu:diva-33732 (URN)978-91-7264-989-1 (ISBN)
Public defence
2010-05-27, Institutet för Rymdfysik, Aulan, Rymdcampus 1, Kiruna, 09:00 (English)
Available from: 2010-05-06 Created: 2010-05-04 Last updated: 2010-05-06Bibliographically approved

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