Nonforest Herbs

ALPINE

Figure 4.3. Representation of major pollen taxa in relation to vegetation along an altitudinal surface sample transect in Papua-New Guinea (modified from Flenley, 1973).

Transect Tation

Figure 4.4. Relative abundance of major pollen groups, taxa, and charcoal derived from core-top samples in the northwestern Australian-southern Indonesian region based on a pollen sum of total dryland pollen excluding pteridophytes. Data from van der Kaars and De Deckker (2003) and van der Kaars (2001).

Figure 4.4. Relative abundance of major pollen groups, taxa, and charcoal derived from core-top samples in the northwestern Australian-southern Indonesian region based on a pollen sum of total dryland pollen excluding pteridophytes. Data from van der Kaars and De Deckker (2003) and van der Kaars (2001).

In contrast to pollen—that generally reflects the regional representation of vegetation—charcoal, derived from the same samples, shows a less certain pattern, at least in percentage terms. It is very unlikely that fire activity is highest in the open ocean where charcoal values are highest. This clearly indicates that charcoal particles, on average, are transported farther than pollen. However, it is clear from a general decline northwards that charcoal is, as expected, derived mainly from Australia. The reduction in charcoal percentages in the very northwest of Australia may be realistic as, within this very dry area, a lack of fuel would allow only the occasional burn.

The South China Sea shows largely an inversion of the southern hemisphere pattern (Figure 4.5). Here, tropical rainforest angiosperm pollen is derived largely from the equatorial humid region centred on Borneo and decreases northwards relative to Pinus which may be regarded as the equivalent of Australian sclerophyllous trees, in its dominance of drier and more seasonal open forests that cover large areas of Peninsular Southeast Asia and more subtropical forests of southern China. The much higher values of Pinus are considered to result from the influence of the strong northerly winter monsoons that blow while Pinus trees are still in cone, in addition to the high production and dispersal rates of its pollen (Sun et al., 1999). The rainforest gymnosperms—represented in Figure 4.5 by their most conspicuous genus,

Modelling Monsoon Wind South China Sea

Tropical complex , /'t Abundance

Pinus % Abundance

Pleridophyte spores Abundance

Podocarpus % Abundance

Figure 4.5. Relative abundance of major pollen groups and taxa derived from core-top samples in the South China Sea based on a pollen sum of total dryland pollen excluding pteridophyes. Adapted from Sun et al. (1999).

Podocarpus—clearly show much broader pollen dispersal than the angiosperms and sources in both the equatorial tropics and mountains in southern China. Pteridophyte values, when consideration is given to the different basis for calculation of the pollen sum, are similar to those in southern waters, but are demonstrably well dispersed with highest percentages towards the center of the basin. Although not illustrated, mangroves in both data sets show highest values close to coastal locations with a substantial fall away from the coast.

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