Diatom assemblages reveal regional-scale differences in lake responses to recent climate change at the boreal-tundra ecotone, Manitoba, Canada
Diatom assemblages reveal regional-scale differences in lake responses to recent climate change at the boreal-tundra ecotone, Manitoba, Canada
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硅藻组合揭示了加拿大马尼托巴省北方苔原生态交错带湖泊对近期气候变化的反应的区域尺度差异
DOI：
10.1007/s10933-016-9911-5
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发表时间：
2016
影响因子：
2.1
通讯作者：
Geiss, Christoph
中科院分区：
文献类型：
--
作者：
Shinneman, Avery L.;Umbanhowar, Charles E.;Edlund, Mark B.;Hobbs, William O.;Camill, Philip;Geiss, Christoph
泛北极生态系统对气候变暖的响应方向相对较好；然而，陆地、湿地和湖泊生态系统之间的景观级联系显著影响着每一个生态系统的动态，使得很难概括整个北极地区湖泊对气候变暖的反应，有时也很难解释湖泊沉积物的古气候记录。为了研究北部冻土带交错带湖泊对近期气候变化的响应差异，我们对加拿大马尼托巴省北部不同集水特征的湖泊中的硅藻组合进行了为期两年的调查。我们调查了集水区地貌和景观，包括坡度和植被覆盖，是否导致了特有的水化学特征，从而产生了硅藻组合特征，然后可以用于古湖泊研究，以推断集水区过去的变化。对44个湖泊进行了水化学采样，并利用陆地卫星图像对集水区植被进行了表征。湖泊集水区一般很小(中位数702公顷)，以泥炭(泥炭)为主，有或没有低地森林(云杉-落叶松)或开阔的苔原，有不同数量的裸露岩石/耕作、高地森林/林地和燃烧恢复区。湖泊总体上是营养贫乏的，冻土带为主的集水区营养物质和DOC浓度较低，森林覆盖率较大的集水区营养物质和DOC较高。建立了一个基于硅藻的pH传递函数(R2=0.72，=0.54)，并与8个湖泊岩心的硅藻组合周转和沉积物地球化学进行了比较，以重建近200年来的湖相条件。大多数岩芯显示出类似的生物成因二氧化硅和碳埋藏的增加，从公元1880年左右开始在冻土带湖泊中开始，在更多森林覆盖的集水区大约在1920年开始，可能是对区域变暖的反应。与其他北极地区的湖泊相比，近几十年来，我们的湖泊只出现了微小的pH值变化。然而，这种转变在森林覆盖率较低的高纬度湖泊中更为明显，这表明即使在短时间尺度上，小尺度分水岭也会影响湖泊对气候的反应。硅藻组合没有遵循之前发表的与气候相关的群落变化模式，这些模式出现在环北极和亚北极湖泊中。要将古湖相记录中检测到的局部变化转化为区域一级的变化，就需要了解不同的集水区性质如何影响湖泊及其硅藻组合对气候变化的反应。
The direction of pan-Arctic ecosystem shifts in response to climate warming is relatively well understood; however, landscape-level linkages among terrestrial, wetland, and lake ecosystems significantly influence the dynamics of each, making it difficult to generalize about lake responses to warming across the Arctic, and at times difficult to interpret paleoclimate records from lake sediments. To investigate differences in lake responses to recent climate change at the boreal-tundra ecotone, we conducted a 2-year survey of diatom assemblages from lakes with varying catchment characteristics in northern Manitoba, Canada. We investigated whether catchment geomorphology and landscape, including slope and vegetative cover, result in characteristic water chemistries and hence diatom assemblage signatures, which could then be used in paleolimnological studies to infer past changes in the catchment. Forty-four lakes were sampled for water chemistry and catchment vegetation was characterized using Landsat Imagery. Lake catchments were generally small (median 702 ha) and dominated by peat (Sphagnum) with or without lowland forest (Picea-Larix), or open tundra, with different amounts of exposed rock/till, upland forest/woodlands, and burn recovery area. Lakes were generally nutrient-poor, with lower nutrient and DOC concentrations in tundra-dominated catchments, and higher nutrients and DOC in catchments with greater forest cover. A diatom-based transfer function for pH (R2= 0.72,= 0.54) was developed and compared with diatom assemblage turnover and sediment geochemistry in cores from eight lakes to reconstruct limnologic conditions over the past ~200 years. Most cores showed similar increases in biogenic silica and carbon burial, beginning around AD 1880 in the tundra lakes and about 1920 in the more forested catchments, likely in response to regional warming. In contrast to lakes in other Arctic regions, our lakes showed only minor pH changes in recent decades. The shift, however, was more pronounced in higher-latitude lakes with less forest cover, suggesting small-scale watershed influence on lake response to climate, even on short time scales. Diatom assemblages did not follow previously published models of climate-linked community change seen in circum-Arctic and sub-Arctic lakes. Translating local changes detected in the paleolimnological record to the regional level requires an understanding of how different catchment properties mediate the response of lakes, and their diatom assemblages, to climate change.