This study was conducted in a farm belonging to Military Brigade in the Itaara
county, RS. The main objective was to quantify the nutrient stocks in the soil and the
above ground biomass. The second aim was to evaluate the litterfall from different
tree species, and to quantify the internal nutrient cycling and the nutrient flux to the
soil, respectively. The total contents of N, P, K, Ca, Mg, S, Fe and Mn were
determined for all plant and soil material. For sample collection 8 trenches were
opened. Soil samples were taken in each 10 cm depth for determining soil density
and the chemical analysis of total and available nutrient contents. To litter collection
six plots (25 m x 17 m) were marked with five round collectors in each plot. Litter
collections were done monthly, during a period of 24 months. The litter material was
separated in the laboratory in leaves, fine branches (< 1 cm) and miscellaneous
(flowers, fruits, seeds and debris of unidentified plants). After this preseparation a
further separation followed selecting the leaves of 7 tree species. To quantify the
biomass, the trees were separated in the fractions stemwood, stembark, branches
and leaves. The biomass estimation based on the equation log y = b0 + b1 . log DAP,
which was derived from the biometric data. The results indicate that the soil of the
studied area has a medium fertility. In the 24 months of litter collection the main
deposition occurred in the beginning of winter and spring. The leaves contributed
with 72% in litter composition, the fine branches with 16%, and the miscellaneous
with 12%. There wasn’t a significant correlation between the climatic variables
(average temperature and monthly rainfall) and the litterfall. Great amounts of
nutrients are allocated in the litter being an important way of internal nutrient cycling
within the forest. Parapipdania rigida was the species with the greates cycling rate
along the 24 months. In total the following increasing order exists: Parapipdania
rigida > Ocotea pulchella > Matayba elaeagnoides > Ocotea puberula > Nectandra
megapotamica > Schinus mole > Cupania vernalis. The highest contents of N, P, and
Ca were found in Parapipdania rigida, the highest contents of K, Mg and S were
found in Matayba elaeagnoides. The above ground biomass totaled to 210 Mg ha-1.
Branches had the greatest amount followed by stemwood > stembark > leaves.
However, the highetst contents of N, P, K, Mg and S were found in the leaves, the
highest Ca contents in the stembark. Compared with the other tree compartments
branches had the highest stock of nutrients. More than 55% of total N, P, K, Ca, Mg
and S of the above ground biomass was stored in this compartment. Regarding to
the total forest ecosystem the highest stocks of N, P, K, Ca, Mg and S are in the soil.
In view of a potential usage a complete removal of stemwood and wood branches
would cause an essential export of N, P, K, Ca, Mg and S. However, if harvesting is
restricted to stemwood, only 19% N, 21% P, 25% K, 17% Ca, 28% Mg and 29% S
would be removed outside the environment. More than 70% of the nutrients will
remain in the ecosystem.
