Saulnier-Talbot Émilie, Antoniades Dermot, Pienitz Reinhard
Laboratoire de paléoécologie aquatique (LPA), Département de géographie and Centre d'études nordiques (CEN: Centre for Northern Studies), Université Laval, Québec, QC, Canada.
Glob Chang Biol. 2020 Apr;26(4):2270-2279. doi: 10.1111/gcb.15016. Epub 2020 Feb 26.
Ecotones mark zones of rapid change in ecological structure at various spatial scales. They are believed to be particularly susceptible to shifts caused by environmental transformation, making them key regions for studying the effects of global change. Here, we explored the variation in assemblage structure of aquatic primary producer and consumer communities across latitudinal transects in northeastern North America (Québec-Labrador) to identify spatial patterns in biodiversity that indicated the location of transition zones across the landscape. We analyzed species richness and the cumulative rate of compositional change (expressed as beta-diversity) of diatoms and chironomids to detect any abrupt shifts in the rate of spatial taxonomic turnover. We used principal coordinates analysis to estimate community turnover with latitude, then applied piecewise linear regression to assess the position of ecotones. Statistically significant changes in assemblage composition occurred at 52 and 55°N, corresponding to the transition between closed- and open-crown forest, and to the southern onset of the forest tundra (i.e., the forest limit), respectively. The spatial distribution of ecotones was most strongly related to air temperature for chironomids and to vegetation- and soil-related chemical attributes of lake water for diatoms, including dissolved organic carbon content and water color. Lakes at mid- to high-latitudes currently face pressures from rapidly rising temperatures, accompanied by large increases in organic carbon inputs from their catchments, often leading to browning and its associated effects. The biota at the base of food webs in lakes located in transition zones are disproportionately affected by the cascading effects of these multi-factorial changes, concurrent with pronounced terrestrial greening observed in these regions. Similar patterns of biotic shifts have been observed along alpine aquatic transects, indicating the potential for widespread restructuring of cold, high-altitude and high-latitude freshwater communities due to global change.
生态交错带标志着在各种空间尺度上生态结构快速变化的区域。它们被认为特别容易受到环境变化引起的转变影响，使其成为研究全球变化影响的关键区域。在这里，我们探索了北美东北部（魁北克 - 拉布拉多）沿纬度断面的水生初级生产者和消费者群落组合结构的变化，以确定生物多样性的空间模式，这些模式表明了整个景观中过渡带的位置。我们分析了硅藻和摇蚊的物种丰富度以及组成变化的累积速率（以β多样性表示），以检测空间分类周转率的任何突然变化。我们使用主坐标分析来估计群落随纬度的周转率，然后应用分段线性回归来评估生态交错带的位置。组合组成的统计学显著变化分别发生在北纬52度和55度，分别对应于封闭树冠森林和开放树冠森林之间的过渡，以及森林苔原的南部起始点（即森林界限）。生态交错带的空间分布与摇蚊的气温以及硅藻的湖水植被和土壤相关化学属性（包括溶解有机碳含量和水色）最为密切相关。中高纬度的湖泊目前面临着气温迅速上升的压力，同时其集水区的有机碳输入大幅增加，常常导致水体褐变及其相关影响。位于过渡带湖泊食物网底部的生物群受到这些多因素变化级联效应的影响尤为严重，同时这些地区还出现了明显的陆地绿化。在高山水生断面也观察到了类似的生物变化模式，这表明由于全球变化，寒冷的高海拔和高纬度淡水群落可能会广泛重组。
