THE EFFECT OF POLLEN RECRUITMENT PROCESSES ON POLLEN DISTRIBUTION OVER THE SEDIMENT SURFACE OF A SMALL LAKE IN CUMBRIA
THE EFFECT OF POLLEN RECRUITMENT PROCESSES ON POLLEN DISTRIBUTION OVER THE SEDIMENT SURFACE OF A SMALL LAKE IN CUMBRIA
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DOI：
10.2307/2259143
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发表时间：
1978-07
影响因子：
5.5
通讯作者：
A. Bonny
中科院分区：
文献类型：
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作者：
A. Bonny
摘要(1)在一个小的坎布里亚湖(面积102公顷)进行了花粉补充研究，在其中引入了两个实验管，每个实验管分别隔离一个直径45m×12m深的水柱。(2)每隔4-6周测量一次单位时间单位面积的花粉沉积量，包括漂浮在管缘内的圈闭，以及埋藏在管内外和湖中泥面上的其他圈闭。对流入溪流的水和悬浮沉积物样本以及来自该湖36个地点的表层沉积物样本进行了额外的花粉计数。(3)漂浮捕捉器明显低估了空气中花粉在水面上的实际沉积通量，低估了x~2倍。(4)埋藏在管道内的捕捉器的捕获量随着新鲜气传花粉的相对补充和管道内泥面去层化过程中被湍流重新悬浮的花粉而发生季节性变化。(5)埋藏在开阔湖泊中的圈闭捕获了气传和再悬浮花粉的季节性成分，也捕获了流传花粉成分。这种径流成分的组成随季节变化，其大小随径流的变化而变化。(6)管内埋入诱捕器的年花粉捕获量仅相当于管外捕获量的15%，说明向湖中供应的花粉中有很大比例必须是流传的。(7)管道内的年度水下花粉捕获物主要是明显散布在空气中的花粉类群，而露天湖泊捕获物中含有较高比例的流传花粉和大量不确定(降解)的花粉，可能是从集水土壤中采集的。(8)与管内捕获物相比，埋入开阔湖中的圈闭捕获物的花粉组成与湖面集水区植被组成之间的对应关系更为密切。(9)采用主成分分析和最小方差聚类分析两种不同的多元分析方法，对36个表层沉积物样品的孢粉数百分比进行了分析。这两种分析都表明，8米水深等高线内的花粉光谱非常相似，但来自较浅水域的光谱在不同地方有很大差异(显然是边缘植被输入的高度和局部花粉的结果)，尽管沿海再悬浮的影响可能会消除这种空间差异。(10)每厘米沉积物中的花粉(根据水分含量进行调整)在穿过湖泊的样带上的0-1厘米深度和0-8厘米深度的样本中被发现大致均匀。
SUMMARY (1) Pollen recruitment was studied at a small Cumbrian lake (area 10 2 ha) into which two experimental tubes, each isolating a water column 45 m diameter x 12 m deep, had been introduced. (2) Pollen deposition per unit area per unit time was measured at 4-6-weekly intervals in traps floating inside the tube rims, and in other traps submerged inside and outside the tubes and at two points on the mid-lake mud surface. Additional pollen counts were made on water and suspended sediment samples from inflow streams, and on surface sediment samples from thirty-six locations in the lake. (3) Floating traps apparently underestimated, by a factor of x 2, the actual flux of airborne pollen deposition on the water surface. (4) Catches in the traps submerged inside the tubes varied seasonally with the relative recruitment of fresh airborne pollen and of pollen resuspended by turbulence during destratification from the mud surface within the tubes. (5) The traps submerged in the open lake caught seasonal components of airborne and resuspended pollen, and also a streamborne pollen component. This streamborne component changed seasonally in composition and its magnitude varied with runoff. (6) Annual pollen catches in traps submerged inside the tubes were equivalent to only 15% of the catches outside, indicating that a high proportion of all pollen supplied to mid-lake must be streamborne. (7) Annual underwater pollen catches inside the tubes were dominated by pollen taxa which are apparently dispersed efficiently in air, whereas the open lake catches included high proportions of streamborne pollen and also a large component of indeterminable (degraded) pollen, which was probably recruited from catchment soils. (8) A closer correspondence between the pollen composition of material trapped in mid-lake and the composition of vegetation on the catchment area of the lake was found for the catches in the traps submerged in the open lake (where a substantial streamborne pollen component was present) than for catches inside the tubes. (9) Two different multivariate methods (principal components analysis and minimumvariance cluster analysis) were used to analyse percentage pollen counts from thirty-six surface sediment samples. Both analyses showed that pollen spectra from within the 8-m water-depth contour were closely similar, but that spectra from shallower water differed considerably from place to place (apparently as a result of high and localized pollen input from marginal vegetation), despite the effects of littoral resuspension, which might be expected to obliterate such spatial differences. (10) Pollen per cm3 sediment (adjusted for water content) was found to be approximately uniform in samples from 0-1 cm depth along a transect through the lake, and also in a 0-8 cm