CLIMIFORAD en Congreso ATBC-OTS

Para el congreso especial  de la Asociación para La Conservación y La Biología Tropical (ATBC por sus siglas en inglés) y la Organización para Estudios Tropicales (OTS) (http://atbc2013.org/), organizado con motivo de la celebración del 50 aniversario de ambas instituciones, han sido aceptadas tres presentaciones de trabajos de investigación ejecutados dentro del marco del Proyecto CLIMIFORAD.  El congreso se llevará a cabo durante los días 23 al 27 de junio en Costa Rica.

Los resúmenes de los estudios son los siguientes:

 

Climate, soil and spatial factors controlling forest characteristics over a 2500 m altitudinal gradient in Costa Rica

Darío Veintimilla, MSc. dveintimilla@catie.ac.cr
Bryan Finegan, PhD. Production and Conservation in Forests, CATIE (bfinegan@catie.ac.cr)
Diego Delgado. MSc. Production and Conservation in Forests, CATIE, (ddelgado@catie.ac.cr)
Sergio Vilchez, MSc, Biostatistics Unit, CATIE (svilchez@catie.ac.cr)
Pablo Imbach, PhD. Global Change Unit, CATIE (pimbach@catie.ac.cr)
Nelson Zamora, INBio (zamoravn@gmail.com)

 

Centro Agronómico de Investigación y Enseñanza CATIE
Escuela de posgrado, CATIE 7170. Cartago, Turrialba, 30501. Dirección física de la sede universitaria del Atlántico (UCR) 2 km, carretera a Siquirres. *dveintimilla@catie.ac.cr

 Abstract

Tropical mountain forests are vital ecosystems gravely threatened by global change, but factors underlying forest change on altitudinal gradients are still not well understood.  We determined forest diversity, structure, composition and species turnover in relation to climate, soils and space in Atlantic slope primary forests 300-2800 masl. In 32 0.25 ha plots we measured trees, ferns and palms ≥ 10 cm dbh and lianas ≥ 2 cm stem diameter. WorldClim climate data (1 km2 resolution) were used, and soil was sampled in each plot. Data were explored with multivariate techniques, spatial analysis and variance partitioning to determine relationships among vegetation, climate, soil and space.  Rainfall seasonality, highest at 2800 masl, joined temperature as the main altitudinal gradient in environmental conditions and there was a secondary horizontal gradient of mean annual rainfall at middle elevations.  Soil was less related to altitude, though results suggest increasing N limitation with altitude and decreasing P limitation.  Species richness and diversity of all plant functional types declined linearly with altitude; lianas entered the montane forest but not above 2400 masl.  57% of floristic variation was explained by climate, soil, altitude and space, in that order of importance.  “Pure” effects of environment were small and were not significant for altitude and space, but variation in species composition is spatially structured, and related to environmental variation that is also spatially structured, so part of the environmental effect could not be separated from a potential spatial effect.  Altitudinal change in tropical forest characteristics is usually interpreted in relation to environment (niche assembly) though our results suggest a primary effect of climate, a small effect of soil and a potential effect of dispersal limitation (space).  Further study of these mechanisms will strengthen understanding of global change impacts on these forests.

 Potential impacts of climate change on distributions of nectar and fruit-feeding bats on a forested altitudinal gradient of Costa Rica.

 José Luis Echeverría Tello, MSc, Production and Conservation in Forests Programme, CATIE (jecheverria@catie.ac.cr)
Bernal Rodriguez, PhD. Reserva Biológica La Tirimbina (bernalr@tirimbina.org)
Bryan Finegan, PhD. Production and Conservation in Forests, CATIE (bfinegan@catie.ac.cr)
Sergio Vilchez Mendoza, MSc, Biostatistics Unit, CATIE (svilchez@catie.ac.cr)

Tropical mountain forests are globally, regionally and locally vital ecosystems and are gravely threatened by global change.  Nectar and fruit-feeding bats are key elements of forest resilience to a changing climate, but understanding of climate effects on their current and future potential distributions is incomplete.  We determined the main mechanisms of assembly and the potential impacts of climate change on the altitudinal distribution of these mammals through the use of future climate scenarios. The study was conducted on a 360-3000 masl gradient on Costa Rica`s Atlantic slope. We sampled at 28 points over a seven-month period using mist nets. Through variance partitioning analysis, significant relationships were found between the composition of bat species and climatic variables when space was controlled (R2adj = 0,19, p = 0,005) however, relations between species composition and space were not significant when climate was controlled (R2adj = 0,01, p = 0,29). This evidence supports niche assembly as the main mechanism for species turnover of these bats on the altitudinal gradient, and justifies the construction of species distribution models based on environmental variables, elevation and bat count data from field sampling. Using Constrained Additive Ordination the current potential climate envelopes of ten species were modeled using mean annual temperature and maximum temperature of the warmest month. Climate envelopes were then mapped on projected future climates (A1B family, for 2020 and 2080). For 2080, seven species of middle and high elevations showed an 18-85% reduction of potential habitat area – a potentially serious threat to their populations – while three species of low elevations showed a 30-35% increase. This work highlights the importance of conservation actions aimed at ensuring connectivity along altitudinal gradients, facilitating altitudinal migrations and adaptation to rapid climate change.  The consequences of changing distributions of bats for their mutualistic plants require study.

Forest functional composition and diversity patterns across a 2600 m altitudinal gradient in Costa Rica

Catalina Ruiz Osorio, MSc, Production and Conservation in Forests Programme, CATIE (eruizo@catie.ac.cr)
Bryan Finegan, PhD, Production and Conservation in Forests Programme, CATIE (bfinegan@catie.ac.cr)
Sergio Vilchez Mendoza, MSc, Biostatistics Unit, CATIE
(svilchez@catie.ac.cr)

Tropical mountain forests are vital ecosystems that are threatened by climate change, but changes in forest characteristics and processes over altitudinal gradients are not well understood. We assessed functional composition and diversity in relation to climate, soils and space in Costa Rican primary rain forests from 400-3,000 masl. In 35 0.25 ha plots, eight traits (leaf area, specific leaf area SLA, leaf dry matter content LDMC, leaf tensile strength, wood density WD, leaf content of Nitrogen N, Phosphorus P, and K) were measured for 108 tree, tree fern and palm species (80% of the basal area per plot; ≥10 cm dbh). Forest composition was characterized by community weighted mean trait values (CWM) and diversity was characterized by multitrait indices (functional evenness; dispersion, Fdis; divergence, Fdiv; and richness). WorldClim climate data (1 km2 resolution) were used, and soil was sampled in each plot. Data were explored with multivariate techniques and variance partitioning to determine relationships among vegetation, climate, soil and space. Lowland forests had low CWM P and low soil Phosphorus, while highland forests had high CWM WD and LDMC, low CWM N and high soil C-N ratio. “Fast” forests with high CWM N and SLA were found at approximately 1,000 masl on the least acidic soils. Environment and space explained over 75% of the variation in functional composition, though the pure effects of individual variables were relatively little (i.e., temperature: 18%; soil:  12%; precipitation and space: <4%).  Functional diversity decreased with altitude, with stands clearly differentiated by Fdis, though differences among dominants (Fdiv) were highest in montane forests. Because of the strong influence of environmental variables on functional traits, community level processes can be inferred at a range of spatial and temporal scales. These findings highlight functional ecology’s potential to improve our understanding of how climate change impacts mountain ecosystems.