旅游干扰下山地草甸光谱特征及其与冠层特征的关系

Spectral Characteristics of Mountain Meadow under Tourist Disturbance and its Relationship with Canopy Characteristics

本研究利用SVC-HR768光谱仪观测不同旅游干扰程度下山地草甸的冠层高光谱反射率,结合山地草甸的冠层叶绿素含量和冠层组分、结构和生产力的测定,分析旅游干扰下群落数量特征、植物多样性和叶绿素含量(SPAD值)等的变化与冠层反射率和相关光谱参数的相关性,以期利用高光谱技术快速、无损和精确的监测景区旅游干扰对草地生态系统的影响。结果表明:(1)在旅游干扰下,耐践踏的物种重要值增加,而践踏敏感物种重要值减少,物种丰富度、多样性显著下降,群落结构向少数耐践踏的物种集中,群落生产力下降;(2)随着旅游干扰强度的增加,冠层叶绿素含量下降,冠层对可见光的吸收减弱,反射增强,"红边"位置产生了"蓝移"现象,"绿峰"幅值增加,"红谷"和"红边"幅值均呈下降趋势;(3)可利用红边位置、敏感波段优化的多元散射光谱拟合模型对叶绿素含量、群落数量特征和植物多样性进行估算,且相对精度较高,误差较小。因此,利用高光谱技术监测旅游干扰对草地生态系统的影响是可行的。

In this study, the spectral reflectance of canopy in the mountain meadow was measured by hyper-spectral radiometer to indicate the impact of tourist disturbance on the grassland ecosystem. The chlorophyll content, composition, structure and productivity of canopy were measured to analyze changes of community quantitative features, plant diversity index and the relative content of chlorophyll(SPAD values) duo to tourist disturbance. The results showed that:(1) Under the tourist disturbance conditions, the important value of trampling resistant species were increased, while the important value of trampling sensitive species, the richness and diversity of species were all significantly decreased. The main component of community in mountain meadow became trampling resistant species, which resulted in the reduction of community productivity;(2) With the increasing tourist disturbance intensity, the relative content of chlorophyll was decreased, which triggered the weakness of visible spectrum and the increased spectral reflectance of canopy. The ‘red edge’ position occurred the phenomenon of ‘blue shift’. The amplitude of ‘green peak’ was increased, while the amplitudes of "red valley" and "red edge" were both declined;(3) The relative content of chlorophyll, community quantitative features and plant diversity index were estimated by fitting models of multiplicative scatter correction at red edge position and sensitive bands, in which fitting models were more accurate and had less errors than other models. Therefore, it was feasible that the hyper-spectral techniques could monitor impacts of tourist disturbance on grassland ecosystem.