Many tropical forests will become drier with climate change. There is little evidence for how root dynamics will respond to long-term changes in moisture, despite fine root dynamics playing a fundamental role in the cycling of water, nutrients, and carbon in tropical forests. How drying will affect root morphology, biomass, and growth in tropical forests across gradients in rainfall and soil fertility? This project assessed responses of fine roots to in situ drying using throughfall reduction structures (-50%) in four tropical forest sites in Panama. Root standing stock and dynamics were assessed in replicated treatment plots and untreated controls using minirhizotron cameras, soil cores and ingrowth cores. We also analyzed root morphology of the roots from the ingrowth cores.
Results/Conclusions
Experimental drying didn’t affect root productivity, affected mortality at the deepest layer and decreased fine root stock for some sites/depths. Fine root productivity from ingrowth cores and minirhizotrons decreased with soil depth. Deep root standing stocks (to 1 meter) varied among sites. The dry season (February to March 2019) had lower root biomass productivity vs. the wet season (June to September 2018) in 2018 (prior to drying treatment) in ingrowth cores, but length productivity was not different between seasons in 2019 using minirhizotrons. Specific root length (SRL) was not affected by experimental drying, but was larger in the fertile vs. the infertile site. The preliminary data showed that root dynamics can be affected by water availability but root morphology seems to be more related to soil nutrient availability. These variables might interact when experimental drying become more intense over time.