Ecohydrologic Engineering Contributes to the Success of a Pantropical Woody Invader
Abstract
Globally, non-native invasive species are increasingly widespread, but their impacts on ecosystem services are often species- and context- dependent. Of the many species identified as invasive, those considered "ecosystem engineers" or "ecosystem transformers" can yield insights into how a highly successful species can alter ecosystem properties and hydrologic processes. One such species is the pantropical woody invader strawberry guava, Psidium cattleyanum, a widespread and important tree that forms monotypes across many oceanic islands. While Psidium is known to alter canopy partitioning of rainfall and facilitate high transpiration, the net effects of this species on stand carbon and water dynamics are poorly understood. In this study of mesic forest on Oʻahu, Hawaiʻi, we compared a Psidium-dominated stand and an adjacent, native-dominated remnant forest stand in terms of tree diversity, stand structure, substrate, microclimate, tree sapflow and leaf gas exchange, focusing on ecohydrologic "hot spots and hot moments." Psidium had high sap velocities, photosynthetic capacity, and maximum stomatal conductance relative to native trees in the adjacent stand. High Psidium leaf area, steep leaf and branching angle, and smooth bark aided stemflow which generat ed strong soil moisture pulses at Psidium tree bases and for surface layers between trees, even for small rain events. During heavy rain events, stemflow fluxes contributed to pressure-induced bypass flow at the tree base, wetting deeper soils and potentially supporting dry season transpiration and photosynthesis. Psidium's maintenance of high sap flow may be explained by its documented capacity to maintain turgor via osmotic adjustment coupled with the high cavitation resistance of its xylem. Under high soil moisture/low VPD nighttime conditions, Psidium sap velocities tracked vapor pressure deficit, indicating nocturnal stomatal conductance, consistent with emerging views that this can confer a competitive advantage in water-limited systems.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMB122...04K
- Keywords:
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- 3305 Climate change and variability;
- ATMOSPHERIC PROCESSES;
- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 1631 Land/atmosphere interactions;
- GLOBAL CHANGE;
- 1813 Eco-hydrology;
- HYDROLOGY