关键词: 化学分级, 氮沉降, 凋落物, 森林土壤

Abstract: The color preference and phototactic behavior of wild subadult Schizothorax prenanti were investigated, aiming at finding out their preference for light color and light intensity. Fish behaviors were observed under five different lighting conditions (red, yellow, blue, green and dark) and three flow rates (0, 0.15 and 0.30 m·s^-1). In the light color selection experiment, the color preference in static water was observed under the different lighting conditions with the luminance intensity of 10 lx. The color preferable order of S. prenanti for the five kinds of light colors was green, blue, black, red and yellow. The distribution ratio and selection index in the green and blue light regions were greater than that in the red and yellow light regions (P<0.05). In the phototaxis experiment, the phototactic behaviors were observed under different flow rates (0, 0.15 and 0.30 m·s^-1) at the luminance intensity of 20 lx. The results indicated that S. prenanti showed a positive phototactic behavior to the blue and green light under the hydrostatic and hydrodynamic conditions. In contrast, fish showed a negative phototactic behavior to the red and yellow light. S. prenanti preferred low luminance intensities and the phototactic behavior did not increase with increasing water flow rate. The phototactic threshold was 1.40-2.65 lx. Our results indicated that green light with a luminance intensity of 20 lx is appropriate for attracting S. prenanti in the engineering projects.

Key words: chemical fractionation, litter., nitrogen deposition, forest soil