Atmospheric Input and Nutrient Turnover in a Pinus taeda L. Plantation in Rio Grande do Sul (Brasil)

Mauro Schumacher1, Vicente Lopes1, Peter Trueby2
1 Universidade Federal de Santa Maria
2 Albert-Ludwigs-Universitaet Freiburg Br.

P 3.19 in Fluxes between the atmosphere and ecosystems

Poster Session 2 on Tuesday, 16:30-18:00

During the last decades around 300.000 ha of pasture were afforested with fast growing pine plantations.  The main species is Pinus taeda which totals up to 60 % of the whole area. Timber is used mainly for the production of celluloses and paper. The production process is economically optimized causing short rotation periods between 16 and 18 years. Accordingly, substantial amounts of nutrients will be extracted by harvesting timber in these short time periods. After the first or at least the second rotation fertilization is necessary for to avoid soil degradation. For the fertilization management the nutrient extraction by harvesting biomass can be calculated by an inventory. There is no doubt that nutrient extraction by harvesting is one of the main components of the nutrient ecosystem balance. However, in contrast to Eucalyptus plantations with shorter rotation periods atmospheric input and internal cycling of nutrients could play a major role in the budget. Accordingly, this component should be considered when planning fertilization measures in pine plantations.

The aim of the investigation was to determine the atmospheric nutrient input to a pine plantation and to assess the role regarding to the extraction by harvesting.

Open field bulk precipitation, througfall and stemflow were collected in a Pinus taeda L. plantation in Cambará RS during four years. Water fluxes and the concentrations of N, P, K, Mg, Ca, S, Cl and Na were determined in intervals of two weeks.

The atmospheric input was dominated by the Cl (29 kg ha-1 a-1) and Na (22 kg ha-1 a-1) originating from sea spray of the Atlantic Ocean which is only a few kilometers far from the experimental area. Potassium input totaled up to 16 kg ha-1 a-1. Probably this is caused by burning of large areas which is quite common in the region. High fluxes of potassium were determined in the throughfall indicating an intensive internal cycling and - due to burning - also an increased input by dry deposition. The input of Ca, Mg and P were on the level of sites in Middle Europe. The annual input of nitrogen was 8,4 kg ha-1 a-1. Compared with other ecosystems studies of the region the input was relatively low. Lower amounts of N in the throughfall (4,2 kg ha-1 a-1) indicate an interception by the canopy which is quite typical for non-saturated ecosystems.

Considering a nutrient inventory about the nutrient extraction by harvesting biomass in an 18 years old plantation of Pinus taeda L. there is a surprising result. With harvesting only timber without bark the extraction of nutrients was on the same level in some cases even slightly lower than the atmospheric input. If timber with bark was harvested small deficits occurred. Compared with plantations of Eucalyptus this is a quite different situation. At this time a fertilization measure is not necessary.    

Letzte Änderung 02.04.2014