Using Plant Physiologic Responses to Environmental Conditions to Improve Species and Habitat Management in Hawaii

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Recent studies show that past and ongoing environmental changes have been substantial and have likely already affected conservation efforts in Hawai‘i. Much of the state has experienced substantial drying, including decreases in mean annual precipitation since the 1920s, longer rainless periods, and decreasing stream flow. Temperatures have been increasing in Hawai‘i for the last 40 years, especially at higher elevations where most native habitats and species currently persist. To understand plant physiologic responses to shifting environmental conditions to improve species and habitat management in Hawaii, we will use high frequency measurements of plant growth taken under different environmental conditions to understand factors that promote and limit plant growth.

Overview:

Close-up photograph of stem, leaves and flower buds of haha plant

Meet "Caly" the Cyanea calycina, or haha, growing in the Wai‘anae Mountains on the island of O‘ahu, Hawai‘i.

You can keep track of Caly's growth in real-time in a web portal developed with our research and management partners.

(Credit: Lucas Fortini, USGS-PIERC. Public domain.)

Recent studies show that past and ongoing environmental changes have been substantial and have likely already affected conservation efforts in Hawai‘i. Much of the state has experienced substantial drying, including decreases in mean annual precipitation since the 1920s, longer rainless periods, and decreasing stream flow. Temperatures have been increasing in the state for the last 40 years, especially at higher elevations where most native habitats and species currently persist.

There are few long-term monitoring efforts that allow us to understand  responses of plant species to these past, ongoing and future shifts in environmental conditions. Consequently, we know little about how environmental shifts may be limiting the success of current conservation and management efforts. Model-based approaches yield limited information on optimal management locations for species whose present habitat associations and occupancy may not represent a species’ full niche breadth, owing to historical range contractions (Guisan & Thuiller 2005; Phillips et al. 2009). If these species are rare, low numbers of individuals also make it challenging to explore their responses to changing environmental conditions. Consequently, we know little about some factors limiting the success of current management efforts.

Measuring instrument attached to plant stem

A dendrometer to measure fine-scale growth is attached to the stem of an ‘a‘ali‘i plant in the Nakula Natural Area Reserve on Maui, Hawai‘.

(Credit: Lucas Fortini, USGS-PIERC. Public domain.)

These rare species are also typically identified as being the most vulnerable to environmental shifts (Ohlemuller et al. 2008; Fortini et al. 2013). Standard inventory plot methods to study demographic links to environmental conditions are impractical given the limited number of individuals, few remote populations, and the length of continuous monitoring required.

To help define optimal management locations for these species, we have deployed a recently developed autonomous dendrometer sensor array to monitor growth of individual plants (0.5-100 cm diameter) and local environmental conditions at sub-daily intervals. Similar methods have been used elsewhere in precision tree plantations and agricultural settings to link optimal/detrimental conditions to individual plant performance (Drew & Downes 2009; Pajares 2011). Recent tests in Hawaiian forests indicate we can use these techniques to monitor growth of native plants as an integrated measure of plant fitness and relate it to variable environmental conditions such as precipitation, temperature, light, and soil moisture.

Objectives:

Despite many research efforts describing current and potential future impacts of climate and other environmental changes on species and habitat conservation efforts in Hawai‘i and elsewhere, there have been very limited research efforts to translate these impacts into site-specific management recommendations. Nevertheless, the need to adapt current management to past, ongoing and future environmental shifts is clear given the large number of potential species highly vulnerable to climate change (Fortini et al. 2013). Our expected results are aimed directly at providing spatially explicit, site-specific, climate-informed options to help decision support for current and long-term management of species and their associated habitats in Hawaii.

Study Area:

Islands of: Hawai‘i, Maui, and O‘ahu