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Biodiversity and ecosystem function [English]

 

The planted forest of Sardinilla: Biodiversity and Ecosystem Functioning

In the past 15 years, ecologists have spent much effort in understanding the relationship between species diversity and ecosystem function. Results from experimental temperate grasslands suggested a positive relationship, with enhanced functioning of ecosystems associated with increasing species number. However, variable results indicate that the systems under consideration and the traits measured largely determine the intensity of the relationship.

To understand how tree diversity affects ecosystem processes in tropical ecosystems, I established a tree diversity experiment, between 2001 and 2003, in Sardinilla, Panama, where 35 native tree species are grown in plots ranging 1 to 18 species in diversity. The planted forest covers some 6 ha and contains around 5000 individual trees. The species number of the high diversity plots is comparable to that seen in the natural forest of Barro Colorado Island ~ 20km away. A set of core measurements is carried on every year including measurement of individual tree height and diameter, dead woody debris and leaf litter production, herbaceous productivity, canopy closure and water table level. In addition intensive campaigns are often carried out to provide an understanding of specific ecosystem processes such as soil respiration or water flow.

The Sardinilla planted forest is an international collaborative research site examining multiple aspects of carbon, nutrients and water cycling. It is also one of the oldest sites within TreeDivNet, a unique global experimental platform for biodiversity and ecosystem research in forests. My own research group is responsible for the monitoring of pools and fluxes of carbon. Overall the results coming from the Sardinilla planted forest suggest that species identity plays a crucial role in determining carbon stocks and fluxes. Modelling accounting for tree mortality showed that multispecies plots were more productive than monoculture plots. This effect is however dwarfed by that of environmental heterogeneity. Future research directions for the Sardinilla planted forest include the analysis (1) of the stability of primary productivity and (2) the relationship between different ecosystem services in active collaborations with other TreeDIvNet sites. We are also interested in identifying native tree species that could be best used in reforestation aimed at enhancing ecosystem services such as biodiversity or carbon stocks.


Figure: Topographic map of the Sardinilla planted forests showing a grid positioning the diversity plots.
Photo credit: Sebastian Wolfe

The following are photos of the plantation from 2002 to 2006

 
   


 

 

Mixture 1 - Nine Species
The design allows for an explicit test of neighborhood effects.

 

C cycling model
We have adopted the following conceptual system model to study the cycling and accumulation of C.

 

According to our model, the driver of the system is photosynthetic C uptake, while C is lost either as plant or soil respiration and herbivory. C is stored in three main stocks (Ab, Bw, So) and moves between those stocks by two flows (L, FR). To meet the specific objectives of both experiments, we will quantify each term of our system's model in both the diversity plots or FACE rings (twice a year over a period of 5 years. We expect that both changes in land use and elevated CO2 will result in larger C stocks and alter C flows.

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Last update: June 11, 2014