Whitfeld T.J.S.,Brown University |
Lasky J.R.,Columbia University |
Damas K.,PNG Forest Research Institute |
Sosanika G.,The New Guinea Binatang Research Center |
And 3 more authors.
Biotropica | Year: 2014
Much of the world's tropical forests have been affected by anthropogenic disturbance. These forests are important biodiversity reservoirs whose diversity, structure and function must be characterized across the successional sequence. We examined changes in structure and diversity along a successional gradient in the lowlands of New Guinea. To do this, we measured and identified all stems ≥5 cm diameter in 19 0.25 ha plots ranging in age from 3 to >50 yr since disturbance. We also measured plant functional traits related to establishment, performance, and competitive ability. In addition, we examined change in forest structure, composition, species diversity, and functional diversity through succession. By using rarefaction to estimate functional diversity, we compared changes in functional diversity while controlling for associated differences in stem and species density. Basal area and species density increased with stand age while stem density was highest in intermediate secondary forests. Species composition differed strongly between mature and secondary forests. As forests increased in basal area, community-weighted mean wood density and foliar carbon increased, whereas specific leaf area and proportion of stems with exudate decreased. Foliar nitrogen peaked in medium-aged forests. Functional diversity was highest in mature forests, even after accounting for differences in stem and species diversity. Our study represents one of the first attempts to document successional changes in New Guinea's lowland forest. We found robust evidence that as succession proceeds, communities occupy a greater range of functional trait space even after controlling for stem and species density. High functional diversity is important for ecological resiliency in the face of global change. © 2014 The Association for Tropical Biology and Conservation.
Sam K.,Academy of Sciences of the Czech Republic |
Sam K.,University of South Bohemia |
Koane B.,The New Guinea Binatang Research Center |
Novotny V.,Academy of Sciences of the Czech Republic |
Novotny V.,University of South Bohemia
Ecography | Year: 2015
Signals given off by plants to alert predators to herbivore attack may provide exciting examples of coevolution among organisms from multiple trophic levels. We examined whether signals from mechanically damaged trees (simulating damage by herbivores) attract predators of insects along a complete elevational rainforest gradient in tropical region, where various predators are expected to occur at particular elevational belts. We studied predation of artificial caterpillars on trees with and without 'herbivorous' damage; as well as diversity and abundances of potential predators at eight study sites along the elevational gradient (200-3700 m a.s.l.). We focused on attacks by ants and birds, as the main predators of herbivorous insect. The predation rate decreased with elevation from 10% d-1 at 200 m a.s.l. to 1.8% d-1 at 3700 m a.s.l. Ants were relatively more important predators in the lowlands, while birds became dominant predators above 1700 m a.s.l. Caterpillars exposed on trees with herbivorous damage were attacked significantly more than caterpillars exposed on trees without damage. Results suggest that relative importance of predators varies along elevational gradient, and that observed predation rates correspond with abundances of predators. Results further show that herbivorous damage attracts both ants and birds, but its effect is stronger for ants. © 2014 The Authors.
Basset Y.,Smithsonian Tropical Research Institute |
Eastwood R.,Harvard University |
Sam L.,The New Guinea Binatang Research Center |
Lohman D.J.,Harvard University |
And 8 more authors.
Insect Conservation and Diversity | Year: 2013
1.Standardised transect counts of butterflies in old-growth rainforests in different biogeographical regions are lacking. Such data are needed to mitigate the influence of methodological and environmental factors within and between sites and, ultimately, to discriminate between long-term trends and short-term stochastic changes in abundance and community composition. 2.We compared butterfly assemblages using standardised Pollard Walks in the understory of closed-canopy lowland tropical rainforests across three biogeographical regions: Barro Colorado Island (BCI), Panama; Khao Chong (KHC), Thailand; and Wanang (WAN), Papua New Guinea. 3.The length and duration of transects, their spatial autocorrelation, and number of surveys per year represented important methodological factors that strongly influenced estimates of butterfly abundance. Of these, the effect of spatial autocorrelation was most difficult to mitigate across study sites. 4.Butterfly abundance and faunal composition were best explained by air temperature, elevation, rainfall, wind velocity, and human disturbance at BCI and KHC. In the absence of weather data at WAN, duration of transects and number of forest gaps accounted for most of the explained variance, which was rather low in all cases (<33%). 5.Adequate monitoring of the abundance of common butterflies was achieved at the 50ha BCI plot, with three observers walking each of 10 transects of 500m for 30min each, during each of four surveys per year. These data may be standardised further after removing outliers of temperature and rainfall. Practical procedures are suggested to implement global monitoring of rainforest butterflies with Pollard Walks. © 2012 The Royal Entomological Society.