祁连山金强河河谷区域高寒灌丛群落海拔梯度影响特征与光谱变化

Characteristics and spectral variation of alpine shrubcommunities with different altitudes in JinqiangRiver valley in eastern Qilian Mountains

摘要:

高寒灌丛是青藏高原生态系统的重要部分,研究高寒灌丛对青藏高原生态系统的研究具有重要意义。光谱遥感技术作为近年来发展迅速的遥感探测技术,可以实现高空间分辨率和高光谱分辨率的地物大面积无损探测。研究高寒灌丛的光谱变换特性有助于光谱遥感技术在青藏高原生态系统研究中的应用。选取青藏高原祁连山东段的甘肃省天祝县金强河河谷区域,根据海拔高度的变化,从2 900 m到3 600 m的阴坡,每100 m设置一个样地,采集每块样地的光谱数据。对采集的光谱数据进行平滑降噪处理后,通过反射率(REF)、吸收率(ABS)及反射率和吸收率的一阶导数(GREF和GABS)变换,分析了灌丛群落和光谱特征随海拔梯度的变化规律。主要结论如下:1)群落多样性的空间格局中,物种多样性随海拔梯度的变化极显著,光谱REF与α多样性随海拔升高均呈现倒“V”字形变化。α多样性最高的海拔梯度与群落光谱REF最大的值均集中在中间海拔区域(3300~3400 m);2)灌丛含水率随海拔梯度的变化呈“N”字形,即灌丛含水率与群落光谱REF随海拔梯度的增加先升高后下降再升高;3)群落高度,生物量和茎叶比对灌丛群落光谱特征的影响较明显。阴坡灌丛群落光谱REF与生物量、茎叶比随海拔梯度的增加呈反“N”形变化;4)千里香杜鹃和头花杜鹃灌丛在整个灌丛群落中占有关键地位,其群落特征的变化对灌丛光谱特征的影响明显。

Abstract:

As a component of Qinghai-Tibetan Plateau ecosystem,alpine shrubs play an important role.As a fast developing remote sensing technology in recent years,hyperspectral remote technology can be used to investigate large area with high spatial resolution and spectral resolution.In order to explore the spectral characteristics of alpine shrubs at different elevation gradients,8 sampling zones distributed on the shady slope from 2 900 to 3 600 m with 100 m interval were selected in Jinjiang River valley in the eastern part of Qilian Mountains on the Qinghai-Tibet Plateau,Tianzhu County of Gansu Province,to collect the field spectral data and indoor spectral data of dominant shrub communities by using FieldSpec4 spectrometer.After the smooth noise reduction of the spectral data,the data were analyzed through reflectivity (REF),absorptivity (ABS) and first derivative transformation of reflectivity and absorptivity (GREF and GABS).The result indicated that 1) the species diversity changed significantly at altitude gradient,and spectral REF and α diversity index showed an inverted ‘V’ shape.The altitude gradient with highest α diversity index and the maximum REF value of the community spectrum were concentrated in the middle altitude area (3 300~3 400 m);2) the shrub water content showed a ‘N’ shape with the increase of altitude,i.e.,with the increase of altitude,the shrub water content and the community spectral REF first increased,then decreased and then increased;3) the spectral characteristics of shrub communities were significantly affected by the community height,biomass and stem/leaf ratio.With the increase of altitude,they showed an inverse ‘N’ shape.4) Rhododendron thymifolium and Rh.capitatum dominated the shrub community,and significantly affected the spectral characteristics.