Verschoren Veerle, Schoelynck Jonas, Buis Kerst, Visser Fleur, Meire Patrick, Temmerman Stijn
Department of Biology, Ecosystem Management Research Group, University of Antwerp, Universiteitsplein 1C, 2610, Wilrijk, Belgium.
Institute of Science and the Environment, University of Worcester, Henwick Grove, Worcester, WR2 6AJ, UK.
Environ Monit Assess. 2017 Jun;189(6):294. doi: 10.1007/s10661-017-6004-5. Epub 2017 May 26.
The presence of vegetation in stream ecosystems is highly dynamic in both space and time. A digital photography technique is developed to map aquatic vegetation cover at species level, which has a very high spatial and a flexible temporal resolution. A digital single-lens reflex (DSLR) camera mounted on a handheld telescopic pole is used. The low-altitude (5 m) orthogonal aerial images have a low spectral resolution (red-green-blue), high spatial resolution (∼1.9 pixels cm, ∼1.3 cm length) and flexible temporal resolution (monthly). The method is successfully applied in two lowland rivers to quantify four key properties of vegetated rivers: vegetation cover, patch size distribution, biomass and hydraulic resistance. The main advantages are that the method is (i) suitable for continuous and discontinuous vegetation covers, (ii) of very high spatial and flexible temporal resolution, (iii) relatively fast compared to conventional ground survey methods, (iv) non-destructive and (v) relatively cheap and easy to use, and (vi) the software is widely available and similar open source alternatives exist. The study area should be less than 10 m wide, and the prevailing light conditions and water turbidity levels should be sufficient to look into the water. Further improvements of the image processing are expected in the automatic delineation and classification of the vegetation patches.
溪流生态系统中水生植物的分布在空间和时间上都具有高度的动态性。本文开发了一种数字摄影技术，用于绘制物种水平的水生植物覆盖图，该技术具有很高的空间分辨率和灵活的时间分辨率。使用安装在手持伸缩杆上的数码单反（DSLR）相机。低空（5米）正交航空影像具有低光谱分辨率（红-绿-蓝）、高空间分辨率（约1.9像素/厘米，约1.3厘米长）和灵活的时间分辨率（每月）。该方法已成功应用于两条低地河流，以量化植被河流的四个关键属性：植被覆盖度、斑块大小分布、生物量和水力阻力。该方法的主要优点包括：（i）适用于连续和不连续的植被覆盖；（ii）具有非常高的空间分辨率和灵活的时间分辨率；（iii）与传统地面调查方法相比相对较快；（iv）非破坏性；（v）相对便宜且易于使用；（vi）软件广泛可用，并且存在类似的开源替代方案。研究区域宽度应小于10米，并且主要光照条件和水体浑浊度应足以观察水中情况。预计在植被斑块的自动勾勒和分类方面，图像处理将得到进一步改进。
