SP 12: Phosphorus availability and cycling
Phosphorus availability and cycling
Principal investigator(s):
| Prof. Dr. Jürgen Bauhus (University of Freiburg) |
Co-Principal investigator(s):
| Prof. Dr. Michael Scherer-Lorenzen (University of Freiburg) |
Phd candidate(s):
| Björn Todt (University of Freiburg) |
Contact adress:
Institute of Silviculture, University of Freiburg, Tennenbacherstr. 4, D-79106 Freiburg, Germany
Faculty of Biology, Geobotany, Albert-Ludwigs-University Freiburg, Schänzlestr. 1, D-79104 Freiburg, Germany
Summary
The project is investigating to what extent availability and cycling of phosphorus may be influenced by tree species diversity in the subtropical forests of southeastern China. The maintenance of soil fertility through species diverse forests might be an important ecosystem service in tropical regions with their large areas of forest plantations. Given the large range of biologically available soil P compounds, and the variety of mechanisms by which plants can access P, we assume that co-existing plant species partition soil organic P to reduce competition. This research will examine in particular the relationships between tree species diversity and the proportion of soil P in available fractions and P nutrition. P fractions and pools of different plant availability are analyzed at Freiburg University with the sequential fractionation method according to Hedley. Preliminary investigations at the Comparative Study Plots (CSP) of BEF China have shown, that soil P concentrations are very low, a large proportion of available P is in organic from, and that many of the species show of leaf and litter P concentrations that are indicative P limitation. However, the high variation of P tissue concentrations points to a variety of species-specific mechanisms to adopt to limited P supply. In addition, we will explore whether the different soil P fractions can be distinguished on the basis of their spectral properties, which would greatly reduce analytical efforts.
Objectives
The subproject focuses on the following four main objectives, addressing tree diversity effects on plot and single tree level as well as under decreasing P sources:
- (1) The proportion of soil P in available fractions increases with increasing tree species diversity of the CSP.
- (2) The neighborhood tree species diversity affects soil P fractions and nutrition (also nutrient use efficiency) of individual trees.
- (3) Effects of tree species diversity on productivity decline (complementarity reduction) with decreasing diversity of soil P sources. Since sources of organic P are more diverse than mineral P sources (at a particular pH), diversity effects are more pronounced when P is available as organic P than when it is available in mineral form.
- (4) The different soil P fractions can be distinguished on the basis of their spectral properties using near-infrared spectroscopy.
