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Precipitation signal in pollen rain from tropical forests, South India
Review of Palaeobotany and Palynology ( IF 1.9 ) Pub Date : 2001-04-01 , DOI: 10.1016/s0034-6667(01)00057-4
D Barboni 1 , R Bonnefille
Affiliation  

We have analyzed the pollen content of 51 surface soil samples collected in tropical evergreen and deciduous forests from the Western Ghats of South India sampled along a west to east gradient of decreasing rainfall (between 11 degrees 30-13 degrees 20'N and 75 degrees 30-76 degrees 30'E). Values of mean annual precipitation (Pann, mm/yr) have been calculated at each of the 51 sampling sites from a great number of meteorological stations in South India, using a method of data interpolation based on artificial neural network. Interpolated values at the pollen sites of Pann range from 1200 to 5555mm/yr, while mean temperature of the coldest month (MTCO) remains >15 degrees C and humidity factor (AET/PET, the actual evapotranspiration to potential evapotranspiration ratio) remains also included between 65 and 72%.Results are presented in the form of percentage pollen diagrams where samples are arranged according to increasing values of annual precipitation. They indicate that the climatic signal of rainfall is clearly evidenced by distinct pollen associations. Numerical analyses show that annual precipitation is an important parameter explaining the modern distribution of pollen taxa in this region. Pollen taxa markers of high rainfall (Pann >2500mm/yr) are Mallotus type, Elaeocarpus, Syzygium type, Olea dioica, Gnetum ula, and Hopea type, associated with Ixora type and Caryota. Pollen taxa markers of low rainfall (Pann <2500mm/yr) are Melastomataceae/Combretaceae, Maytenus type, Lagerstroemia and Grewia. The proportions of evergreen taxa and of arboreal taxa vary according to rainfall values. Indeed, when rainfall is <2500mm/yr, percentage of arboreal pollen (AP) is <50% and proportion of evergreen taxa is <20%. When rainfall exceeds 2500mm/yr, AP values average 70%, and proportion of evergreen taxa increases from 60 to 90%. Moreover, a good correlation between precipitation and proportion of evergreen taxa (0.85) presumes that precipitation can be estimated from pollen data.

中文翻译:

印度南部热带森林花粉雨的降水信号

我们分析了在南印度西高止山脉的热带常绿和落叶林中采集的 51 个表层土壤样品的花粉含量,这些样品沿西向东降雨量减少的梯度(北纬 11 度 30-13 度和北纬 75 度 30 度之间)采样。 -76 度 30'E)。使用基于人工神经网络的数据插值方法计算了印度南部大量气象站的51个采样点的年平均降水量(Pann,mm/yr)值。Pann 花粉位点的内插值范围为 1200 至 5555 毫米/年,而最冷月份的平均温度 (MTCO) 仍然大于 15 摄氏度,湿度因子 (AET/PET,实际蒸散量与潜在蒸散量之比) 仍然包括在内65% 到 72% 之间。结果以百分比花粉图的形式呈现,其中样本根据年降水量的增加值排列。他们表明降雨的气候信号清楚地由不同的花粉关联证明。数值分析表明,年降水量是解释该地区花粉类群现代分布的重要参数。高降雨量 (Pann >2500mm/yr) 的花粉类群标记是 Mallotus 型、Elaeocarpus、Syzygium 型、Olea dioica、Gnetum ula 和 Hopea 型,与 Ixora 型和 Caryota 相关。低降雨量 (Pann <2500mm/yr) 的花粉类群标记是 Melastomataceae/Combretaceae、Maytenus 型、Lagerstroemia 和 Grewia。常绿类群和树栖类群的比例因降雨值而异。事实上,当降雨量 <2500 毫米/年时,树栖花粉(AP)的百分比<50%,常绿类群的比例<20%。当降雨量超过 2500 毫米/年时,AP 值平均为 70%,常绿类群的比例从 60% 增加到 90%。此外,降水与常绿类群比例 (0.85) 之间的良好相关性假设可以从花粉数据估计降水。
更新日期:2001-04-01
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