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DCA axis 1

Figure 2.1. Modern pollen rain and elevation. Regression of first axis DCA scores against elevation for log-transformed modern pollen data. All data from a line transect from Amazonia into the Andes in eastern Peru (Weng et al., 2004). Circles represent samples of known elevation. The six triangles represent a blind study in which the analyst did not know sample elevation.

increments were collected along a transect in the Kosmpata Valley, Peru. The eleva-tional range of the samples was from 300 m to 3,400 m. Despite high pollen diversity (more than 400 types identified) in these samples, >90% of pollen was identified to family level and 30-50% to genus level (Weng et al., 2004). Log-transformed pollen data were analyzed with detrended correspondence analysis (Hill, 1979; McCune and Mefford, 1999) and the resulting Axis 1 scores regressed against elevation (Figure 2.1). In 2001 we collected six further samples and conducted a blind study. The six un-labelled samples were given to the analyst (Weng) to determine the accuracy with which they could be placed into the data set (Figure 2.1). From these results we determined that our accuracy in assigning an elevation to an unknown sample is about ±260 m. Local moist air adiabatic lapse rates are almost exactly 5.5°C per 1,000m of ascent (Weng et al., 2004). From this we infer that our error in assessing temperature based on palynology is c. ±1.5°C. The Kosnipata transect was mature second-growth forest, disturbed by road construction. As disturbance-tolerant species tend to produce a lot of pollen and are often generalist species, ongoing study of less disturbed transects may provide even narrower error ranges in temperature estimates.

It will be noted that the samples in Figure 2.1 from 3,350 and 3,400 m do not fall close to the regression line. Both of these samples were collected from sheltered gullies that contained shrubs of Weinmannia, woody Asteraceae and Polylepis, giving these samples a "low" signature in the analysis.

Figure 2.1. Modern pollen rain and elevation. Regression of first axis DCA scores against elevation for log-transformed modern pollen data. All data from a line transect from Amazonia into the Andes in eastern Peru (Weng et al., 2004). Circles represent samples of known elevation. The six triangles represent a blind study in which the analyst did not know sample elevation.

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