Diploma Thesis: Phosphorus in a Tropical Tree Plantation

Abstract:

My diploma thesis is taking place in the frame of Fabienne Zeugin’s PhD project (ETH Zurich), which has as overall objective establishing a link between species diversity and phosphorus (P) and nitrogen (N) cycling in a tropical forest plantation. The main hypothesis is that higher tree diversity results in higher overall nutrient uptake by plants from the soil as well as in better use of the nutrients by the plant communities. This would indicate complementarity of nutrient acquisition strategies among different species.

The tropical forest plantation is located in Panama and is part of the ‘Sardinilla Project: Biodiversity and Ecosystem’. It’s an international and inter-institutional research facility administered by the ‘Smithsonian Tropical Research Institute’. The biodiversity plantation is managed by Catherine Potvin from McGill University, Canada.

I focus on P which is an essential element for all organisms (e.g. as irreplaceable component of DNA, RNA, phospholipids, ATP etc.). In the soil P is found in different forms (pools): In inorganic phosphates, more or less stable organic forms, but also in organisms and available for the plants in the soil solution. The P in microbes is a labile pool because of its short turnover time and therefore a potentially plant available pool.

The aim is to find out how much plant available and microbial P is in the soil of the plantation and if these amounts are influenced by the growing culture (mono- vs. mixed cultures). Therefore the top 10cm of the plantation are sampled. The influence of the topographic position is investigated at seven profiles of 50cm depth. Further more is tested if the trees species affect the distribution of plant available and microbial P in the top 25cm and if the P concentrations in the plant material are positively related with the amounts of available and/or microbial P in the topsoil.

For determining the amounts of plant available and microbial P the FE method with anion-exchange resin membranes after Kouno et al. is used.

The investigations done so far do not allow establishing a link between species diversity and P cycling. The amounts of available and microbial P in the top 10cm are mainly influenced by the soil development and the water level which are two very variable factors within the plantation.  The distribution of plant available and microbial P in the top 25cm around single trees of three species does hardly vary between the monocultures and higher concentrations in the leaf material do not result in higher concentrations of available P in the topsoil.

 

Thomas Seitlinger                                                                
MSc student,                                                                       
Dpt. Geography, University of Zurich                                                 
Aubodenstrasse 59, CH-8472 Ohringen                                    
Email: s0271569@access.unizh.ch                                           
Tel.: +41-52-335-12-79                                                         

Dr. Benjamin Turner
Smithsonian Tropical Research Institute
Apartado 0843-03092, Balboa, Ancon,
Panama, Republica de Panama
Email: turnerbl@si.edu
Tel.: +507-212-8171

Figure 1: Experimental tree plantation in Sardinilla, 2007

 

Figure 2: Accommodation close to the tree plantation in Sardinilla