The Sardinilla biodiversity experiment has been established in Panama in 2001 and is thus one of the older experimental sites of the TreeDivNetwork. The goal is to study complex links between biodiversity, landuse and tropical ecosystem functioning, with a focus on biogeochemistry and plant health. The Sardinilla project consists of different plantations and experiments, apart from the "old" main biodiversity experiment (2001) there are some additional plots for a "new" high biodiversity experiment (2003), a new agroforestry plantation (2006) and a pot experiment (2006).
The "old" main plantation consists of 24 plots, planted with 6 native tree species of 3 functional groups in 3 diversity levels. 12 plots were planted with monocultures, 6 triplets (different composition, 1 species per funtional group) and 6 full 6-species mixtures.
Every plot has a size of 45 m x 45 m with a density of 1111 trees ha-1, which means a 3 meter spacing between trees.
The experimental design of the main plantation leaves two questions unanswered:
(1) Is the high diversity treatment relevant to the level of forest diversity?
(2) What is the importance of community composition at high diversity?
To answer these questions, Potvin and collaborators have established eight additional reforestation plots of 15 m x 45 m in July 2003. The experiment follows a split-plot design with 3 diversity levels per plot: 6, 9 and 18 species.
This high species number was chosen after estimating the diversity of plots of 45 m by 45 m in Barro Colorado Island (an area nearby) and is comparable to background diversity in intact forest (19 species). The high diversity experiment further compares four different mixtures of 6 and 9 species with a total of 36 species used.
The regular design within these plots allows for an explicit test of neighborhood effects.
|Area||Ca 5 ha.|
|No of plots||24 + 8|
|No of trees||5 400 + 864|
|Former land use||Original forest, logged in 1950. Two years of agriculture took place, since then pasture.|
|Soil type||A clay Alfisol on a bedrock of limestone and other sediments.|
|Planting date||July 2001 (main plantation) and July 2003 (additional plots)|
|Species pool||Luehea seemannii and Cordia alliodora (Pioneer group); Anacardium excelsum and Hura crepitans (Intermediate group); Cedrela odorata and Tabebuia rosea (Shade tolerant group).|
|Contact person||Dr. Catherine Potvin|
The first measurements of tree height and basal area have been done and the results show a difference between diversity
levels from the third year of growth with a higher basal area and tree height for mixtures in comparison with monocultures.
Results for litter and biomass production and nitrogen and phosphorus stock are less clear as a stronger relation with tree species and environmental variation was found than with diversity level. No diversity effect can be found for litter decomposition, but species decompose differently in different mixtures.
A lot of research was aslo done on the impact of neighbour trees, tree-to-tree interactions are highly important to understand diversity effects. First results of these neighbourhood analyses show that small trees grow slower, show larger variability and die more often than large trees. This size-asymetric competition seems to be stronger in monocultures than in mixtures. Trees in monoculture invested less biomass to branches than to trunks.
Environmental heterogeneity turns out to be a very important factor to explain the differences between plots: there is a large effects of geographical position of plots. In general, the 3-species mixtures are more often located on ridges. Importance for productivity of environment is bigger than species identity which is also bigger than species richness.
Environmental heterogeneity turns out to be a very important
factor to explain the differences between plots, there is a
large effect of geographical position of plots (see image at the
right side of page).
In general, the 3-species mixtures are more often located on
ridges. Importance for productivity of environment proofs to be
bigger than species identity which is also bigger than species
Variation in elevation of the sardinilla site (Healy et al. 2008, J. Ecol.)
A lot of research is currently going on on the Sardinilla site:
Biomass accumulation and carbon cycling (C. Potvin, T. Moore and C. Messier)
Nitrogen and phosphorus dynamics, including mycorrhizal fungi (M. Scherer-Lorenzen and J. Jansa)
Plant productivity and carbon sequestration potential (N. Buchmann and W. Eugster)
Element cycles of individual trees (Y. Oelmann and W. Wilcke)
Tree water use of individual trees (L. Schwendenmann and D. HÖlscher)
Plant health and herbivory (K. Mody and S. Dorn)
For more information on the Sardinilla site, please visit the project website or e-mail the contact person:
|Project website||Sardinilla website|
|Contact person||Prof. Dr. Catherine Potvin|