基于遥感技术植物叶脉性状的计算及其生态学意义

Leaf vein functional traits calculation method based on remote sensing and its ecological significance analysis

叶脉网络性状能够反映出植物适应特定生境的基本方式及其光合生理功能,体现了植物水分和能量权衡的生态策略。叶脉功能性状的高效提取,为植物生理功能和资源配置的响应机理研究提供参考。以北京市常见绿化树种洋白蜡(Fraxinus pennsylvanica)、臭椿(Ailanthus altissima)和国槐(Sophora japonica)的叶脉显微图像为训练样本,采用遥感图像处理软件,对叶脉显微图像进行多尺度分割和分类识别,根据目标对象的亮度(brightness)、光谱(spectrum)和几何(shape)特征规则实现大批量叶脉的快速解译。结果表明,3个树种叶脉分割的最优参数及自动提取规则为:尺度参数(scale parameter)为200,形状参数(shape parameter)为0.8,紧凑度参数(compactnes sparameter)为0.2,亮度值为190-230,绿光波段大于210,形状–密度指数为1.5。该方法提取叶脉密度(leaf vein density,LVD)和叶脉面积(leaf vein area,LVA)精度分别达到了95.7%和94.5%以上,对该3种植物叶脉性状的快速提取具有较高的普适性。在城市不同环境中,随着温度的升高、土壤水分含量的降低,叶脉密度总体上呈增大的趋势,而气孔数量则明显减少,叶脉密度与气孔密度间普遍存在显著的负相关关系(P<0.05)。这说明了植物在高温和干旱胁迫环境中,在叶片水平上表现出"此消彼长"的权衡规律,进一步提高其逆境耐受性。

Leaf vein network traits can reflect the basic behavior and photosynthetic physiological function of plants adapting to specific habitats, which represent the ecological strategies of plant water and energy transmission. How to extract the leaf vein functional traits efficiently will provide a reference for the study of the response mechanism of plant physiological functions and resource allocation. This study chose the leaf of Fraxinus pennsylvanica, Ailanthus altissima and Sophora japonica as objects, analyzing vein functional traits by multi–scale segmentation and classification recognition, classifying the leaf vein microscopic images via eCognition image processing software. The vein imagines were classified and identified based on the spectral characteristics, brightness characteristics and shape characteristics of the objects. The results showed that the best parameters of the vein division and automatic extraction were as follows: scale parameters was 200, shape parameter was 0.8, compactness parameter was 0.2, brightness value was 190-230, green light band was above 210, shape-density index was 1.5, the accuracy of vein density and vein area was above 95.7 % and 94.5 % by this method. The calculation accuracy of this method was higher than the traditional one, which was suitable for rapid extraction of vein information to the three plant leaves. In the urban thermal environment, as the temperature increased and the soil moisture content decreased, the leaf vein density generally increased, while the number of stomatal decreased obviously. There was a significantly negative correlation between leaf density and stomatal density(P<0.05), which showed the balance between stomatal density and vein density on leaf level under the environment of high temperature and drought stress. It promotes the improvement of its adversity tolerance.