Green leaf phenological characteristics of boreal peatland vegetation impacted by linear disturbances

Vast areas of boreal peatlands are impacted by linear disturbances known as seismic lines. Tree removal and ground disturbance alter vegetation communities and are expected to change ecosystem functioning. As boreal landscapes continue to be disturbed by linear disturbances, understanding the magnitude and mechanisms of vegetation and phenology changes is the first step toward predicting carbon cycling changes across broad spatial scales. We investigate seismic line disturbances on peatland plant community composition and phenological patterns using readily available digital photography at a bog and a fen in Alberta, Canada. Our objectives were to: 1) compare the understory peatland vegetation on seismic lines with those in adjacent undisturbed areas using two phenological metrics (green and red chromatic coordinates); 2) evaluate if vegetation greenness is directly related to vegetation community composition, and 3) determine whether plot-scale greenness predicts plant productivity. We found that areas of peatlands intersected by seismic lines have an earlier seasonal peak (maximum greenness) compared to undisturbed areas, and vegetation communities had a stronger relationship to greenness and gross primary production (GPP) at disturbed areas relative to undisturbed areas. This change in understory vegetation results in greater CO2 uptake in disturbed areas. We demonstrate an easy-to-use application of digital photography that successfully quantifies phenological changes in boreal peatland vegetation. This non-destructive method for understanding vegetation phenology eliminated the need for fixed infrastructure and allowed us to expand our sampling capacity and study sites while allowing for repeated measures in the future.寒温带泥炭地（boreal peatlands）的大片区域正受到被称为地震勘探线（seismic lines）的线性干扰的影响。树木移除与地面扰动会改变植被群落，并预计将改变生态系统功能。随着寒温带景观持续遭受线性干扰，明晰植被与物候变化的幅度与作用机制，是预测大空间尺度碳循环变化的首要步骤。本研究借助加拿大阿尔伯塔省一处高位泥炭沼泽（bog）与一处低位泥炭沼泽（fen）的易获取数码摄影数据，探究地震勘探线干扰对泥炭地植物群落组成及物候模式的影响。本研究的研究目标如下：1） 借助绿色与红色色度坐标两种物候指标，对比地震勘探线上的林下泥炭地植被与邻近未干扰区域的植被；2） 评估植被绿度是否与植被群落组成直接相关；3） 明确样方尺度的绿度能否预测植物生产力。研究结果显示，相较于未干扰区域，被地震勘探线穿过的泥炭地区域的季节性绿度峰值出现更早；且相较于未干扰区域，干扰区域的植被群落与绿度及总初级生产力（GPP, gross primary production）的相关性更强。林下植被的此类变化使得干扰区域的二氧化碳吸收量更高。本研究展示了一种易于实施的数码摄影应用方案，可精准量化寒温带泥炭地植被的物候变化。这种非破坏性的植被物候研究方法无需搭建固定基础设施，既提升了我们的采样能力与研究样地覆盖范围，也为未来的重复采样提供了可行条件。