Frequency and intensity effects
A total of 20 AS was introduced to each stream, arranged in four rows,
and five columns. The lines were allocated transversally to the stream,
and the distance between each line was at least 200 meters. We randomly
distributed the frequency of disturbance to each line (Fig. 1). The
frequency of the disturbance (applied in each line separately) was
composed of the control, disturbance at every six days (F1), disturbance
at 3 days (F2) and random disturbance (F3; i.e., 1 control and 3
treatments per stream).
To test the different intensities of disturbance, we conducted the
experiment twice. The first time with an increased water flow intensity
of 30m3.hour-1 10 minutes on all AS
except the control level. The second time the intensity was
60m3.ha-1 for 10 minutes. The first
battery of the experiment occurred in July and the second in August. The
distance among the ASs remained the same.