Environmental changes in biodiversity hotspot ecosystems of
South Ecuador: RESPonse and feedback effECTs (FOR2730)

Abstract:

Questions: How does the structure of liana communities (diameter, density and biomass) in tropical montane forests vary along elevation and topographic gradients? How do patterns of tree infestation vary with elevation? Is tree diameter growth reduced by lianas in tropicalmontane forest? Location: Tropical Andean forests (1000–3000 m a.s.l.) in the San Francisco Reserve and in the Podocarpus National Park, southern Ecuador. Methods: All lianas (DBH ? 1 cm) were censused in 54 permanent plots (20 9 20 m) equally distributed between three study sites (1000, 2000 and 3000 m a.s.l.) and three topographic positions (lower, mid and upper slope) per site (six replicate plots at each site by position combination). The DBH and number of lianas hosted was recorded for all trees (DBH ? 10 cm). Liana biomass was estimated using allometric equations. ANOVAs were used to test for effects of elevation and slope positions on liana parameters and proportion of trees infested. The relationships between liana biomass and tree parameters and environmental parameters were analysed with partial least squares regression. We used the available literature data to perform a regression analysis of liana biomass in response to elevation in humid tropical old-growth forests between sea level and 3000 ma.s.l. Results: Liana diameter, density and biomass all decrease with elevation. The decreasing liana biomass agrees with results from previous studies of liana biomass in other humid tropical forests, indicating a decrease of 0.18 Mg/ha liana biomass per 100 m of elevation gain. Topographic variation leads to thinner but more abundant stems upslope; there was no effect of topographic position on liana biomass. Liana biomass and liana infestation are both positively correlated with host tree DBH at every elevation. Tree diameter growth is reduced by liana infestation; the proportion of infested trees is lower in Andean montane forests than in tropical lowland forests. Conclusions: Liana biomass distribution and tree infestation vary significantly with elevation. Biomass of lianas and relative contribution of lianas to total above-ground biomass both decrease with elevation. Topographic effects likely result fromhigher soil fertility at lower slope positions.

Abstract:

Questions: To assess the relationship between modern pollen rain and Andean montane forest vegetation for diversity, and provide a basis for interpretations of palaeoecological data in the northern Andes, we asked: (1) can the reduction of plant and pollen data to family level preserve information about diversity in both data sets; (2) how precisely do tree pollen and spore types represent richness patterns along an altitudinal gradient on tropical mountains; and (3) how similar are tree pollen and spore family richness in relationship to tree family richness? Location: Tropicalmontane rain forests, Podocarpus National Park in the Andes of South Ecuador (3°S, 79°W, 1000–3000 ma.s.l.). Methods:We analysed tree diversity and species composition in three different rain forest types: Premontane (PMF), lowermontane (LMF) and uppermontane (UMF).We investigated modern pollen rain using pollen traps. After testing the reliability of a taxonomic surrogacy on the plant data, we compared abundance and representation, as well as diversity of the two data sets at family level. This was done using rarefaction and Sørensen indices. Results: The correlation between tree species and families was high (r = 0.81, P < 0.001). Sample rarefaction on tree pollen and plant family data revealed highest pollen diversity on sites of the UMF, but highest tree diversity on LMF and PMF sites. The Sørensen indices indicate down-drift of pollen from higher altitudes in PMF and LMF and up-drift in UMF. Between 1% and 50% of pollen taxa of each sample originate fromoutside the plot. Conclusions: Taxonomic surrogacy at family level is a good tool for comparing presence–absence patterns of plant and pollen data in tropical regions with high tree diversity. On a family basis, pollen presence–absence data represent the corresponding tree vegetation data, but uncertainties increase with decreasing altitude. The higher diversity in pollen data of the UMF, but slightly lower diversity in the LMF and PMF, can at least partly be explained by wind patterns, local abundance of shrubs and herbs and differences in evenness.