Dynamic process connectivity explains ecohydrologic responses to rainfall pulses and drought

Authors: GOODWELL, ALLISON - Illinois State University; KUMAN, PRAVEEN - Illinois State University; Fellows, Aaron; Flerchinger, Gerald

Submitted to: Proceedings of the National Academy of Sciences (PNAS)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/26/2018
Publication Date: 8/27/2018
Citation: Goodwell, A.E., Kuman, P., Fellows, A.W., Flerchinger, G.N. 2018. Dynamic process connectivity explains ecohydrologic responses to rainfall pulses and drought. Proceedings of the National Academy of Sciences. 115(37):E8604-E8613. https://doi.org/10.1073/pnas.1800236115.
DOI: https://doi.org/10.1073/pnas.1800236115

Interpretive Summary: In the face of changing climate, weather variability, and land cover, it is important to understand how components of an ecosystem jointly interact to determine how the system responds as a whole. The linking of process con-nectivity to ecosystem responses in this study provides a foun-dation for future studies of ecosystem resilience under chang-ing climate, weather patterns, and land cover. The varied relationships between information 'ow and ecohydrologic be-haviors at neighboring sites indicate the signi'cant in'uence of local conditions, such as soil properties and antecedent con-ditions, on responses to perturbations. The pervasiveness of synergistic relationships, in which multiple drivers in'uence 'uxes jointly, indicates that ecohydrologic 'uxes are often responding to diverse drivers. The di'erences in ecosystem sensitivities between neighboring sites along an elevation gra-dient to similar perturbations in moisture availability reveals the importance of these joint in'uences.

Technical Abstract: Ecohydrologic 'uxes within atmosphere, vegetation and soil systems exhibit complex and joint variability that arises from forcing and feedback interactions. These interactions exist on many timescales and can cause 'uctuations in one variable to propagate to others. On an ecosystem scale, the connectivity arising from these joint interactions dictates responses to perturbations involving changing climate, land cover, or weather variability. To understand ecosystem resilience or sensitivity to these perturbations, we must characterize the time-dependent connectivity in ecohydrologic systems in rela-tion to observed indicators of ecosystem function. In this paper, we quantify connectivity between water and energy states and 'uxes in systems that experience altered dry season moisture availability. We use a Temporal Information Partitioning Network approach, based on information theory measures, to identify time-dependencies be-tween variables measured at 'ux towers along elevation and climate gradients. In Southern Sierra, California, we 'nd that network con-nectivity to latent and sensible heat 'uxes decreases as a drought progresses over several years, but that sites along an elevation gradi-ent are variably sensitive to the altered connectivity due to external in'uences. At Reynolds Creek, Idaho, we detect network behavioral shifts due to a dry season rainfall pulse, where the level of in'uence varies between sites with di'erent antecedent moisture and vege-tation conditions. Through a novel approach to gage the respon-siveness of ecosystem 'uxes to shifts in connectivity under di'erent perturbations, this study furthers our understanding of resilience and sensitivity in ecohydrologic systems.