Introduction

Transpiration Characteristics of Native and Non-Native Plants at a Leeward Ko‘olau Forest Site, O‘ahu, Hawai‘i

Controlling or eradicating non-native plants in Hawai‘i is difficult and expensive. Knowledge of the impacts of non-native plants on water resources is important for water managers and conservation organizations to help them plan for the best use of their resources to restore and maintain the hydrological function of Hawai‘i’s watersheds.

Transpiration Characteristics of Native and Non-Native Plants at a Leeward Ko‘olau Forest Site, O‘ahu, Hawai‘i

Maximum wet season sap velocities (a–c) and whole-tree sap flux (d–f) for multiple individuals of each species, plotted against diameter at breast height, for the Nov 2018-March 2019 study period (left column), five sunny days with higher soil moisture (center column), and c) five sunny days with lower soil moisture (right column). Mean diurnal sap velocities for each species for all days (g), sunny with high soil moisture (h), and sunny with lower soil moisture (i).
Maximum wet season sap velocities (a–c) and whole-tree sap flux (d–f) for multiple individuals of each species, plotted against diameter at breast height, for the Nov 2018–March 2019 study period (left column), five sunny days with higher soil moisture (center column), and c) five sunny days with lower soil moisture (right column). Mean diurnal sap velocities for each species for all days (g), sunny with high soil moisture (h), and sunny with lower soil moisture (i).

SPONSOR:
Honolulu Board of Water Supply

PROJECT PERIOD:
06/06/18 – 06/04/21

ABSTRACT:
The goal of this project is to improve understanding of the transpiration characteristics of native and non-native plants at a site representative of wet forests in the leeward Ko‘olau mountains. This study complements our recently completed field study at a site in Mākaha Valley. While the Mākaha study compared transpiration for native and non-native trees in a mesic environment, this project observes transpiration differences in a wetter climate. The specific objectives are to (1) determine the rates of transpiration in selected native and non-native species occurring in a leeward Ko‘olau forest; (2) determine the gas exchange characteristics of those native and non-native plants; (3) quantify the effects of varying environmental conditions, such as light level, humidity, soil moisture, and canopy wetness, on gas exchange in those plants; and (4) provide an assessment of the general effects of non-native plants on water resources in wet forest environments on O‘ahu.

Project Publication:
Kagawa-Viviani, A., Miyazawa, Y., Nullet, M., and Giambelluca, T. In preparation. Ecohydrologic engineering contributes to the success of a pantropical woody invader.

PRINCIPAL INVESTIGATOR