FORMONCO II

Development of a platform for long-term integrated forest ecosystem monitoring in DR Congo, funded by VLIR-UOS

Photo: Marijn Bauters

This project aims to better understand resilience of natural forests in DR Congo to a changing environment. Therefore, the specific academic outcome is to develop state of the art biogeochemical and eco-hydrological research in representative forest biomes, hand in hand with inclusive education and outreach activities (= developmental objective). To achieve this we work in five forest sites in three different biomes. We study two forest types in tropical lowland rainforest (mixed and mono-dominant Gilbertiodendron forest in Yoko reserve, (0°17'39"N 25°17'20"E), two forest types in the tropical mountain forest (mixed and bamboo forest in Kahuzi-Biéga national park, (2°18'53"S 28°45'30"E), and Miombo semi-arid woodland at the southern border of the Congo Basin (Lubumbashi). In all sites, a fixed setup is operational for biogeochemical monitoring (e.g. through fall collectors, nutrient leaching and litter fall).
In this study, we test two recent nutrient and eco-hydrological paradigms using our permanent monitoring setup on several locations. First, the “leaky nitrostat” paradigm (Hedin et al., 2009) hypothesizes that in tropical forests N2 fixation relieves N limitations thereby securing carbon sequestration as an ecosystem function. However, an apparent up-regulation of N2 fixation, N release from weathering or enhanced N deposition from deforestation on savannah fires (Chen et al. 2010) (FORMONCO data: 30 kg N ha-1 yr-1 (50:50 DIN:DON) might generate an N-rich system, whereby P is limiting, leading to gaseous (N2O, NO and N2) and leaching (NO3-) losses.
Second the “two water worlds” paradigm (Evaristo et al., 2016) hypothesizes that an eco-hydrological separation of subsurface water between 1) water used by trees (bound water) and 2) stream water (mobile water) exists; thereby challenging the assumption that water pools in soil are completely mixed. Hence, poor and incomplete mixing of subsurface water drives forest water fluxes: one reservoir sustaining plant transpiration, and another contributing to groundwater recharge and stream flow. The fact that trees and streams do not return the same pool of water to the hydrosphere has implications for conceptual and numerical models that assume translatory flow.

Photo: Marijn Bauters

Photo: Marijn Bauters

Congolese forests are (compared to other tropical forest regions worldwide) closer to the limits of the climatological envelope where tropical rainforest can grow (see above). Understanding if the forest relies on bound water (i.e. older, stored water) or mobile water (i.e. recent water) might be a crucial factor for the resilience of the forests to changing eco-hydrological cycles. If the forests really rely on bound water, they might be less sensitive to short term changes in the hydrological cycle. It would be very interesting to understand if there is a difference between different forest biomes in this respect. In addition, understanding nitrogen availability allows assessing nutrient (N vs. P) limitation shifts among biomes.
We will contribute here with research on biogeochemical-hydrological interactions in central African forests via four intermediate results: 1) interpretation of existing biogeochemical input/output data and continue data collection; 2) to investigate N and P biogeochemistry; and 3) to investigate water resource partitioning. Across all the scientific activities we develop concerted and inclusive capacity for research, education and outreach to better understand functions of forest ecosystems of DR Congo.