『Abstract
The Gallery forests of the Cerrado biome play a critical role
in controlling stream chemistry but little information about biogeochemical
processes in these ecosystems is available. This work describes
the fluxes of N and P in solutions along a topographic gradient
in a gallery forest. Three distinct floristic communities were
identified along the gradient: a wet community nearest the stream,
an upland dry community adjacent to the woodland savanna and an
intermediate community between the two. Transects were marked
in the three communities for sampling. Fluxes of N from bulk precipitation
to these forests resulted in deposition of 12.6 kg ha-1
y-1 of total N of which 8.8 kg ha-1 was
as inorganic N. The throughfall flux of total N was generally
<8.4 kg ha-1 year-1. Throughfall NO3-N fluxes were higher (7-32 %) while NH4-N and organic N fluxes were lower (54-69 % and
5-46 %) than those in bulk precipitation. The throughfall flux
was slightly lower for the wet forest community compared to other
communities. Litter leachate fluxes differed among floristic communities
with higher NH4-N in the wet community. The
total N flux was greater in the wet forest than in the dry forest
(13.5 vs. 9.4 kg ha-1 year-1, respectively).
The stream water had total N flux of 0.3 kg ha-1 year-1.
The flux of total P through bulk precipitation was 0.7 kg ha-1
year-1 while the main fluxes of total P in throughfall
(0.6 kg ha-1 year-1) and litter leachate
(0.5 kg ha-1 year-1) declined but did not
differ between communities. The low concentrations presented in
soil solution and low fluxes in stream water (0.3 and 0.1 kg ha-1
year-1 for N and P, respectively) relative to other
flowpaths emphasize the conservative nutrient cycling of these
forests and the importance of internal recycling processes for
the maintenance and conservation of riparian and stream ecosystems
in the Cerrado.
Keywords: Biogeochemical processes; Bulk precipitation; Throughfall;
Litter leachate; Soil solution; Riparian zones』
Introduction
Materials and methods
Study area
Soil sampling and analyses
Solution sampling
Bulk precipitation
Throughfall and litter leachate
Soil solution and stream water
Chemical analyses
Statistical analyses
Results
Soil nutrient concentrations and contents
Electrical conductivity and pH of solution samples
Nitrogen concentrations and fluxes
Phosphorus concentrations and fluxes
Discussion
Acknowledgments
References