Limnological effects of peatland drainage and fertilization as reflected in the varved sediment of a deep lake
Limnological effects of peatland drainage and fertilization as reflected in the varved sediment of a deep lake
复制标题
深湖沉积物中泥炭地排水和施肥的湖泊学效应
作者：
H. Simola
研究了Polvijärvi湖35 m深度表层沉积物中硅藻的地层学和化学特征。沉积物中每年存在的层压或阀门使剖面的精确年代得以确定。硅藻以0.5 cm序列分析；从0到16.0 cm连续，然后每隔4个0.5 cm间歇，下降到44.0 cm。沉积物化学（着火损失、C、N、Fe、Mn、Mg、P、叶绿素和类胡萝卜素）分析了从沉积物表面到10.5 cm的33个亚样本，每个亚样本包含1-3个阀，时间跨度为1921-1980年。在4.5 cm深度以上，浮游生物硅藻浓度显著增加，浮游生物硅藻从Tabellaria focullosa→Asterionella formosa→Melosira ambigua→Fragilaria crotonensis的演替反映了湖泊明显的富营养化。这种藻类演替与沉积物积累速率的增加和沉积物化学的变化同步发生，这表明湖泊外来输入增加，藻类产量增加。湖泊生态系统的变化与近20年来对其流域进行的大规模泥炭地排水和施肥是同步的。来自位于流域内的一些湖泊的现有化学数据证明，目前处理过的泥炭地是Polvijärvi湖营养物负荷的主要来源。湖泊生产力略有增加的前一个时期，通过阀门计数可以追溯到公元1690-1910年（35-12厘米）。这一时期（以福尔摩沙Asterionella formosa为特征）可能与该地区刀耕火种的种植时期相吻合。
Stratigraphy of diatoms and chemistry in the surface sediment deposited at 35 m depth in Lake Polvijärvi was studied. The existence of annual laminations or varves in the sediment allowed a precise dating of the profile. Diatoms were analysed in 0.5 cm sequences; from 0 to 16.0 cm continuously and then intermittently every fourth 0.5 cm down to 44.0 cm. Sediment chemistry (loss-on-ignition, C, N, Fe, Mn, Mg, P, chlorophyll and carotenoids) was analysed from sediment surface down to 10.5 cm of altogether 33 subsamples, each containing 1–3 varves, and spanning the period 1921–1980.From 4.5 cm depth upwards the diatom concentration strongly increases, and the plankton diatom succession from Tabellaria flocculosa through Asterionella formosa to Melosira ambigua and Fragilaria crotonensis reflects a marked eutrophication of the lake. This algal succession occurs in pace with an increase in sediment accumulation rate and changes in sediment chemistry, which indicate increased allochthonous inputs and enhanced algal production in the lake. The change of the lake ecosystem is contemporaneous with extensive peatland draining and fertilizing that was carried out on its watershed during the past two decades. Existing chemical data from a number of lakes situated within the drainage area prove that at present the treated peatlands are the main source of nutrient loading of Lake Polvijärvi.A former period with indications of slightly increased productivity of the lake was dated by varve counting to AD 1690–1910 (35–12 cm). This period (characterised by Asterionella formosa) may coincide with that of the slash-and-burn cultivation in the area.