Environmental changes in biodiversity hotspot ecosystems of
South Ecuador: RESPonse and feedback effECTs (FOR2730)

Abstract:

Deforestation and land use change have led to a strong reduction of tropical forest cover during the last decades. Climate change will amplify the pressure to the remaining refuges in the next years. In addition, tropical regions are facing increasing atmospheric inputs of nutrients, which will have unknown consequences for the structure and functioning of these systems, no matter if they are within protected areas or not. Even remote areas are expected to receive rising amounts of nutrients. The effects of higher rates of atmospheric nutrient deposition on the biological diversity and ecosystem functioning of tropical ecosystems are poorly understood and our knowledge of nutrient fluxes and nutrient limitation in tropical forest ecosystems is still limited. Yet, it will be of paramount importance to know the effects of increased nutrient availability to conserve these ecosystems with their biological and functional diversity. During the last years, research efforts have more and more focused on the understanding of the role of nutrients in tropical ecosystems and several coordinated projects have been established that study the effects of experimental nutrient addition. This Research Topic combines results from experiments and from observational studies with the aim to review and conclude on our current knowledge on the role of additional nutrients in ecosystems.

Abstract:

Tank bromeliads are common epiphytic plants throughout neotropical forests that store signi?cant amounts of water in phytotelmata (tanks) formed by highly modi?ed leafs. Methanogenic archaea in these tanks have recently been identi?ed as a signi?cant source of atmospheric methane. We address the effects of environmental drivers (temperature, tank water content, sodium phosphate [P], and urea [N] addition) on methane production in anaerobically incubated bromeliad slurry and emissions from intact bromeliad tanks in montane Ecuador. N addition ? 1 mg g
1 had a signi?cantly positive effect on headspace methane concentrations in incubation jars while P addition did not affect methane production at any dosage (? 1 mg g
1 ). Tank bromeliads (Tillandsia complanata) cultivated in situ showed signi?cantly increased ef?uxes of methane in response to the addition of 26 mg N addition per tank but not to lower dosage of N or any dosage of P (? 5.2 mg plant
1 ). There was no signi?cant interaction between N and P addition. The brevity of the stimulatory effect of N addition on plant methane ef?uxes (1–2 days) points at N competition by other microorganisms or bromeliads. Methane ef?ux from plants closely followed within-day temperature ?uctuations over 24 h cycles, yet the dependency of temperature was not exponential as typical for terrestrial wetlands but instead linear. In simulated drought, methane emission from bromeliad tanks was maintained with minimum amounts of water and regained after a short lag phase of approximately 24 h. Our results suggest that methanogens in bromeliads are primarily limited by N and that direct effects of global change (increasing temperature and seasonality, remote fertilization) on bromeliad methane emissions are of moderate scale.