Kriska György, Malik Péter, Csabai Zoltán, Horváth Gábor
Group for Methodology of Biology Teaching, Eötvös University, H-1117 Budapest, Pázmány sétány 1, Hungary.
Vision Res. 2006 Dec;46(26):4382-6. doi: 10.1016/j.visres.2006.08.020. Epub 2006 Oct 11.
Horizontal black surfaces are usually very attractive to polarotactic aquatic insects, since they generally reflect highly and horizontally polarized light, and thus imitate water surfaces. We monitored highly polarizing black burnt-up stubble-fields, but surprisingly never found aquatic insects or their carcasses in the ash, although flying polarotactic insects were abundant in the area, which we showed by attracting them to horizontal black plastic sheets. To explain this observation, we measured the reflection-polarization characteristics of burnt-up stubble-fields in the red (650 nm), green (550 nm) and blue (450 nm) parts of the spectrum at three directions of view relative to the solar meridian. We established that (i) the degree of linear polarization p of light reflected from the black ash is high; (ii) p is the higher, the darker the ash; (iii) the direction of polarization of reflected light is nearly horizontal only towards the solar and antisolar meridians, and it is tilted in other directions of view; (iv) the standard deviation of both the degree and the direction of polarization of reflected light is large. The latter two characteristics explain why burnt-up stubble-fields are unattractive to aquatic insects. These results may be important in the study of the wider environmental effects of post-harvest burning.
水平黑色表面通常对趋偏振水生昆虫具有很强的吸引力，因为它们一般会高度反射水平偏振光，从而模仿水面。我们监测了高度偏振的黑色烧过的茬地，但令人惊讶的是，尽管该区域有大量飞行的趋偏振昆虫（我们通过将它们吸引到水平黑色塑料片上证明了这一点），但我们在灰烬中从未发现水生昆虫或它们的尸体。为了解释这一观察结果，我们在相对于太阳子午线的三个观察方向上，测量了烧过的茬地在光谱的红色（650纳米）、绿色（550纳米）和蓝色（450纳米）部分的反射偏振特性。我们确定：（i）从黑色灰烬反射的光的线性偏振度p很高；（ii）灰烬越黑，p越高；（iii）反射光的偏振方向仅在朝向太阳和反太阳子午线时几乎是水平的，而在其他观察方向上是倾斜的；（iv）反射光的偏振度和偏振方向的标准偏差都很大。后两个特性解释了为什么烧过的茬地对水生昆虫没有吸引力。这些结果可能对研究收获后焚烧对更广泛环境的影响具有重要意义。
