Working in the tropics, the difficulties were major from the start. Inventories of a
beech forest in Germany can take an afternoon, and it is then clear which species
dominate and what their cover percentages are. In the tropics, even by restriction to
5 or 10 cm dbh (diameter at breast height), it takes weeks and months of intensive
identification work to get reliable species lists. And it is obvious that phytosociological methods and the definition of syn-taxonomic units are senseless, since the
main precondition of an existing “minimum area” is not fulfilled (Fig. 31). The very
artificial syn-taxonomic nomenclature is useless in the tropics at least, though many
syn-taxonomic papers are still published.
In Costa Rica, about 94 tree species per hectare (dbh !10 cm) were inventoried
(Wattenberg and Breckle 1995). If the area was doubled, the number of tree species
would be about 130, indicating the lack of an asymptotic minimum area (Fig. 31).
The number of tree species in southern Ecuador (dbh !5 cm) is extremely high and
almost a world record (Homeier 2004). At both study sites, the climate is typically a
diurnal climate all year round (Fig. 32). Sometimes very large amounts of rain can
fall within 1 day (Fig. 30a), regularly causing landslides on the steep slopes and thus
dynamic reproduction and establishment processes.
In Costa Rica’s 1 ha plot, more than one third of the tree species were present with
only one individual tree, and one fifth with only two individuals (Fig. 33). It is still
almost a miracle how, under these circumstances, successful pollination is possible.
One probable explanation is the process of bird pollination.
Only in species that occur relatively frequently is it possible to delimit an
altitudinal belt structure, as was shown for tree ferns. Figure 34 covers only an
altitudinal distance of 500 m, but the tree ferns apparently exhibit strong niches
(Bittner and Breckle 1995).
What is the growth dynamic of the trees? The growth of tree stems can be checked
by study of the annual rings from drilled bore cores, but this method is destructive;
furthermore, many tropical trees do not produce periodic annual rings. We used
dendrometer bands. Biweekly measurements of 948 trees over several years gave
good hints about the growth conditions, the variability within and between species,
and the influence of site conditions. This could be shown in Costa Rica (premontane
forest between 850 and 1,210 m asl [above sea level]), as well as in the montane
tropical forest (1,850–2,450 m) in Ecuador (Homeier 2004; Homeier and Breckle
2004; Bräuning et al. 2008). Diameter growth was highly variable between the
22 investigated species, with annual increments from 0.6 to 5.7 mm in Ecuador
and from 1.6 to 12.3 mm in Costa Rica. The maximum growth rates were in the
lower diameter classes. Seasonality in growth was seen in the only deciduous tree,
Tabebuia chrysantha.
The tropical forests in Costa Rica are rich in palm species. Figure 35 shows the
growth of three palm species in time, derived from long-term measurements
(J. Homeier, personal communication, 2017: Stattegger 2017). Also, the thickness
of the palm stems depends on size and thus on age (Fig. 36), despite the fact that
monocots are normally described in textbooks as not having a secondary growth of
the stem. The two palms reached dbh values of 21 cm (Euterpe) and 26 cm
(Iriartea). Both species start growing with a slender stem and show a limited
Vegetation, Climate and Soil: 50 Years of Global Ecology
33
beech forest in Germany can take an afternoon, and it is then clear which species
dominate and what their cover percentages are. In the tropics, even by restriction to
5 or 10 cm dbh (diameter at breast height), it takes weeks and months of intensive
identification work to get reliable species lists. And it is obvious that phytosociological methods and the definition of syn-taxonomic units are senseless, since the
main precondition of an existing “minimum area” is not fulfilled (Fig. 31). The very
artificial syn-taxonomic nomenclature is useless in the tropics at least, though many
syn-taxonomic papers are still published.
In Costa Rica, about 94 tree species per hectare (dbh !10 cm) were inventoried
(Wattenberg and Breckle 1995). If the area was doubled, the number of tree species
would be about 130, indicating the lack of an asymptotic minimum area (Fig. 31).
The number of tree species in southern Ecuador (dbh !5 cm) is extremely high and
almost a world record (Homeier 2004). At both study sites, the climate is typically a
diurnal climate all year round (Fig. 32). Sometimes very large amounts of rain can
fall within 1 day (Fig. 30a), regularly causing landslides on the steep slopes and thus
dynamic reproduction and establishment processes.
In Costa Rica’s 1 ha plot, more than one third of the tree species were present with
only one individual tree, and one fifth with only two individuals (Fig. 33). It is still
almost a miracle how, under these circumstances, successful pollination is possible.
One probable explanation is the process of bird pollination.
Only in species that occur relatively frequently is it possible to delimit an
altitudinal belt structure, as was shown for tree ferns. Figure 34 covers only an
altitudinal distance of 500 m, but the tree ferns apparently exhibit strong niches
(Bittner and Breckle 1995).
What is the growth dynamic of the trees? The growth of tree stems can be checked
by study of the annual rings from drilled bore cores, but this method is destructive;
furthermore, many tropical trees do not produce periodic annual rings. We used
dendrometer bands. Biweekly measurements of 948 trees over several years gave
good hints about the growth conditions, the variability within and between species,
and the influence of site conditions. This could be shown in Costa Rica (premontane
forest between 850 and 1,210 m asl [above sea level]), as well as in the montane
tropical forest (1,850–2,450 m) in Ecuador (Homeier 2004; Homeier and Breckle
2004; Bräuning et al. 2008). Diameter growth was highly variable between the
22 investigated species, with annual increments from 0.6 to 5.7 mm in Ecuador
and from 1.6 to 12.3 mm in Costa Rica. The maximum growth rates were in the
lower diameter classes. Seasonality in growth was seen in the only deciduous tree,
Tabebuia chrysantha.
The tropical forests in Costa Rica are rich in palm species. Figure 35 shows the
growth of three palm species in time, derived from long-term measurements
(J. Homeier, personal communication, 2017: Stattegger 2017). Also, the thickness
of the palm stems depends on size and thus on age (Fig. 36), despite the fact that
monocots are normally described in textbooks as not having a secondary growth of
the stem. The two palms reached dbh values of 21 cm (Euterpe) and 26 cm
(Iriartea). Both species start growing with a slender stem and show a limited
Vegetation, Climate and Soil: 50 Years of Global Ecology
33