Program in Ecology, Evolution and Conservation Biology, University of Illinois, Urbana, Illinois, United States of America.
PLoS One. 2013;8(1):e53485. doi: 10.1371/journal.pone.0053485. Epub 2013 Jan 8.
Tropical paleoecologists use a combination of mud-water interface and modern pollen rain samples (local samples of airborne pollen) to interpret compositional changes within fossil pollen records. Taxonomic similarities between the composition of modern assemblages and fossil samples are the basis of reconstructing paleoclimates and paleoenvironments. Surface sediment samples reflect a time-averaged accumulation of pollen spanning several years or more. Due to experimental constraints, modern pollen rain samples are generally collected over shorter timeframes (1-3 years) and are therefore less likely to capture the full range of natural variability in pollen rain composition and abundance. This potentially biases paleoenvironmental interpretations based on modern pollen rain transfer functions. To determine the degree to which short-term environmental change affects the composition of the aerial pollen flux of Neotropical forests, we sampled ten years of the seasonal pollen rain from Barro Colorado Island, Panama and compared it to climatic and environmental data over the same ten-year span. We establish that the pollen rain effectively captured the strong seasonality and stratification of pollen flow within the forest canopy and that individual taxa had variable sensitivity to seasonal and annual changes in environmental conditions, manifested as changes in pollen productivity. We conclude that modern pollen rain samples capture the reproductive response of moist tropical plants to short-term environmental change, but that consequently, pollen rain-based calibrations need to include longer sampling periods (≥7 years) to reflect the full range of natural variability in the pollen output of a forest and simulate the time-averaging present in sediment samples. Our results also demonstrate that over the long-term, pollen traps placed in the forest understory are representative samples of the pollen output of both canopy and understory vegetation. Aerial pollen traps, therefore, also represent an underutilized means of monitoring the pollen productivity and reproductive behavior of moist tropical forests.
热带古生态学家结合泥-水界面和现代花粉雨样本（空气传播花粉的当地样本）来解释化石花粉记录中的成分变化。现代组合成分与化石样本之间的分类相似性是重建古气候和古环境的基础。表层沉积物样本反映了跨越数年或更长时间的花粉的时间平均积累。由于实验限制，现代花粉雨样本通常在较短的时间内收集（1-3 年），因此不太可能捕捉到花粉雨成分和丰度的自然变化的全部范围。这可能会使基于现代花粉雨传递函数的古环境解释产生偏差。为了确定短期环境变化对新热带森林空中花粉通量组成的影响程度，我们从巴拿马的巴罗科罗拉多岛采集了十年的季节性花粉雨，并将其与同期的气候和环境数据进行了比较。我们确定花粉雨有效地捕捉到了森林冠层内花粉流的强烈季节性和分层性，并且个别分类群对环境条件的季节性和年度变化具有不同的敏感性，表现为花粉生产力的变化。我们得出结论，现代花粉雨样本捕捉到了潮湿热带植物对短期环境变化的生殖反应，但因此，花粉雨的校准需要包括更长的采样期（≥7 年），以反映森林花粉输出的自然变化的全部范围，并模拟沉积物样本中的时间平均化。我们的研究结果还表明，从长期来看，放置在森林下层植被中的花粉陷阱是冠层和下层植被花粉输出的代表性样本。因此，空中花粉陷阱也是监测潮湿热带森林花粉生产力和生殖行为的未充分利用手段。
