About the science

Objective

As scientists, we wanted to work to support those managing the forest to provide information about how plants are functioning in their natural environment and how they are affected by changing environmental conditions. Many rare plants such as Cyanea calycina have not been studied in detail, and therefore managers face the difficulty of deciding where and how to outplant native species in the forest that were raised in a nursery. We are currently making high quality measurements of plant growth and the environmental conditions in an area that supports rare or endangered plants. By monitoring plant growth at very high resolution simultaneously with environmental data, we can provide critical feedback that can help determine site or location suitability. In addition, we can learn basic information about the growth and life cycle of rare plants that have never been studied in such detail. Our study uses a camera with an infrared motion sensor to visualize phenological changes and to detect for bird visitations, alongside a fully automated weather station to understand how a particular plant is responding to changing environmental conditions.

Methods

Measurements of plant growth are made by precision dendrometers that measure plant diameter continuously. It is common to see swelling at night as the plants absorb water, and shrinking during the day as that water evaporates. Over longer timescales, we can see growth of the plants, and how growth is related to seasonal processes and environmental variation. The climate station is separated into two parts with the intention of monitoring environmental conditions as related to plant growth on the ridge and in a gully. Observations of rainfall, solar radiation, soil temperature, and soil moisture are being conducted on the ridge, with growth measurements of an individual ʻōhiʻa (Metrosideros polymorpha) and a hōʻawa (Pittosporum argentifolium) close by. Observations below the canopy include below canopy radiation (PAR), air temperature, relative humidity, soil moisture, and soil temperature sensors placed near the plants of interest (Cyanea calycina and Cyanea membranacea).

plantCam is a collaboration between USGS, PICCC, University of Hawaiʻi, US FWS, Hawaiʻi DLNR