Vanessa MINDEN

Nutrient enrichment, as a consequence of fertilization, atmospheric deposition and modification of landscape has changed the relative importance of nutrient elements in limiting productivity, with many formerly phosphorus (P) limited aquatic systems being today nitrogen (N) limited and many terrestrial systems showing patterns of P limitation. Ecological consequences of higher nutrient input rates are shifts in ratios of nutrients and higher productivity rates, loss of species and increase in number of endangered species. It has been shown that different species are adapted to different types of nutrient limitation. As a response to nutrient limitation, plants show distinct traits, e.g. N limitation is associated with a higher root length, whereas P limitation induces higher root phosphatase activity. An important field of research in this context is ecological stoichiometry (ES) theory, which describes the balance of elements and energy in biological functions and processes. ES studies have mainly focused on N and P, but another macronutrient of similar importance, potassium (K), has received less attention. K is the second most abundant nutrient in leaves after nitrogen, and by that more abundant than phosphorus. Even though the total soil K pools are generally higher than those of N and P, soil-plant available K concentrations are often lower, also, organic matter in soils contains almost no K. Current studies indicate that reduction in soil K availability is related to N deposition, which makes K more sensitive to changes in land use and fertilization than either N or P. There are only few studies on the response of plants to different supply rates of N, P and K, although evidence supports that K is already a limiting nutrient in terrestrial ecosystems.

A lot of research has been done on the effects of N and P on plant growth and competition. However, studies on the role of K in direct comparison to N and P are still missing. With this fellowship I aim at conducting research on the role of elemental nutrients on the growth patterns of plant species. I will conduct a greenhouse experiment with the focus on competitive interactions between species adapted to different types of nutrient limitation along gradients of N, P and K availability.

Secondly, I will work on existing data sets collected by the Landscape Ecology Group of the Univ. of Oldenburg, with data on 110 species (from salt marsh ecosystems, reeds, grasslands, semi-dry grassland, heathlands and ruderal habitats), element concentrations (N, P, K) of all tissue types (leaves, stems, roots), as well as biomass allocation traits, Specific Leaf Area, canopy height and ecosystem properties (e.g. productivity, decomposition). Plant available N, P and K concentrations of the soil are available, which allows the direct relation of elemental tissue concentration with elemental resource concentration within the various ecosystems and along gradients from wet habitats to dry habitats.

Keywords: ecological stoichiometry, nutrient limitation, competition, H value, plant traits, nitrogen, phosphorus, potassium

Minden V, Scherber C, Cebrián Piqueras MA, Trinogga J, Trenkamp A, Mantilla-Contreras J, Kleyer M (2016) Consistent drivers of plant biodiversity across managed ecosystems. Philosophical Transactions of the Royal Society B 371: 20150284; DOI 10.1098/rstb.2015.0284 

Lewandowska A et al. (incl. Minden V) (2016) The importance of stoichiometry for biodiversity-functioning relationship – a synthesis across ecosystems. Philosophical Transactions of the Royal Society B 371: 20150283; DOI: 10.1098/rstb.2015.0283

Minden V, Gorschlüter J (2016) Comparison of native and non-native Impatiens species across experimental light and nutrient gradients. Plant Ecology and Evolution 149: 59-72; DOI: 10.5091/plecevo.2016.1118

Minden V, Kleyer M (2015) Ecosystem multifunctionality of coastal salt marshes is determined by key plant traits. Journal of Vegetation Science 26: 651-662; DOI: 10.1111/jvs.12276

Kleyer M, Minden V (2015) Why functional ecology should consider all plant organs: an allocation-based perspective. Basic and Applied Ecology 16:1-9; DOI 10.1016/j.baae.2014.11.002

Kleyer M, Balke T, Minden V, Peppler-Lisbach C, Schoenmakers S, Spalke J,  Timmermann H (2014) Mellum: A highly dynamic landscape, though not for plants. In: Hellwig, U., Stock, M. (Eds.) Dynamic Islands in the Wadden Sea. Wadden Sea Ecosystem 33, pp. 29-44 Minden V, Kleyer M (2014) Internal and external regulation of plant organ stoichiometry. Plant Biology 16:897-907; DOI 10.1111/plb.12155

Minden V, Andratschke S, Spalke J, Timmermann H, Kleyer M (2012) Plant-trait environment relationships in salt marshes: deviations from predictions by ecological concepts. Perspectives in Plant Ecology, Evolution and Systematics 14:183-192; DOI 10.1016/j.ppes.2012.01.002 

Minden V, Kleyer M (2011) Testing the effect-response framework: key response and effect traits determining aboveground biomass of salt marshes. Journal of Vegetation Science 22:387-401; DOI 10.1111/j.1654-1103.2011.01272.x