Background/Question/Methods   We used airborne imaging spectroscopy and LiDAR to quantify the structure and condition of tropical dry forest in Hawaii dominated by the endemic tree species Myoporum sandwicense and Sophora chyrsophylla (MSDF). The study site provides critical habitat to the endangered Hawaiian honeycreeper Loxoides bailleui, but little information is available on the extent or condition of MSDF at regional scales. By quantifying functional plant traits using remotely sensed data, and modeling potential evaporative demands using three-dimensional measurements from LiDAR, we show that the lateral distribution of photosynthetic and nonphotosynthetic vegetation varies strongly across this dry forest landscape.

Results/Conclusions   Most differences were expressions of elevation and volcanic substrate age. Predicted solar insolation produced distinct patterns that were associated with the composition of understory vegetation, suggesting that C4 grasses preferentially occupy areas of reduced evaporative demand. In situ meteorological measurements confirm increased soil moisture content facilitated by dry forest trees. These findings contribute to ongoing management of MSDF in Hawaii, and generate opportunities for adaptive management and restoration in threatened dryland ecosystems in Hawaii.