Small Automatic Sensor for Plant Phenology
Heather E. Lintz1 (hlintz@coas.oregonstate.edu), Anton Kruger2 (anton-kruger@uiowa.edu), Devin A. Wagner3, Ian J. Tenney3
1Oregon Climate Change Research Institute, 346 Strand Agricultural Hall, Oregon State University, Corvallis, Oregon, 97330; Email: hlintz@coas.oregonstate.edu
2IIHR-Hydroscience & Engineering, 100 C. Maxwell Stanley Hydraulics Laboratory, The University of Iowa, Iowa City, Iowa 52242; Email: anton-kruger@uiowa.edu
3Department Electrical & Computer Engineering, The University of Iowa, 4016 Seamans Center for the Engineering Arts and Sciences, Iowa City, Iowa 52242
Introduction
Prototype Electronics
Field Testing
We also tested the system outside for several weeks. During this time, the sensor
was exposed to high wind and several rain events.
Plant phenology or the timing of plant biological events such as
budburst and flowering can have a major impact on plant
productivity, the carbon cycle, the water cycle, species
resilience, mating systems, agricultural sustainability, climate,
and human health. As such, the sensing of plant phenology
targets a wide spectrum of research. For example, phenology
data serve as an independent record of climate change; they
provide means to phenotype plants to better understand
molecular, genomic, and ecological mechanisms of phenology
and related processes; and they validate satellite
measurements and components of land surface models to
understand and predict biogeophysical interactions.
2 mm Plastic
Optical Fibers
Electronics’
Housing
Attaching fibers to a plant
However, to date, the timing of plant biological events is sensed
by satellite, carbon flux tower, digital camera, or human
observation. While these methods of measurement support a
growing literature on plant phenology, only digital cameras and
human observations resolve data to species. Digital cameras
are not cost-effective or practical at a landscape level for many
researchers, and human observations are subject to bias and
can be costly and labor intensive.
Goals
Our goal is to further develop and validate our device for
phenological research to advance our understanding and ability
to predict the timing of biological events such as budburst and
flowering.
Principles
Electronics’
Housing
Mum plant just opening
A microcontroller drives an LED at 320 Hz. An optical fiber caries the light to
the bud. Scattered light travels down a second fiber to a photodetector and
amplifier. The signal is inverted and the microcontroller switches between the
signals at 320 Hz. The output is integrated and the microcontroller digitizes
the analog signal and saves data on flash storage every 15 min. The lock-in
detection technique makes the sensor insensitive to ambient light.
Mum plant opened
Plant fully
open
Laboratory Testing
Plant closed
Rain drops on optical fiber
Left: Photographs of the laboratory
setup for testing the sensor
prototype. The sensor's optical
fibers were attached to Douglas Fir
clippings
Time-series of sensor’s output. The sensor was deployed outside and subject to
direct sunlight, several rain events and on very windy day. The spikes
correspond to raindrops that collected on the optical fiber sensors.
Future Work
We believe the sensor will enable a caliber of research not yet achievable
owing to the difficulty of phenological data collection. We aim to make the
sensor cost-effective and ultimately deployable in a wireless network. We
envision its application in various disciplines and sectors including forestry,
agriculture, climate change research, and genomics. Power consumption is
very low and sensors have an extrapolated, continuous operating time
more than 9 months, suggesting their deployment in the fall, and retrieval in
the following spring.
Throughout this coming spring, we will continue to develop and make the
electronics robust to field conditions. We will also further refine packaging
and power consumption.
An optical fiber illuminates a target bud with modulated light, a
second fiber detects, and guides reflect light to a photodetector
and signal processing electronics. Changes in the reflected
light indicate the bud burst.
Time-series of the sensor’s output and a sequence of photographs of the
Douglas fir bud. The sensor output changed as the Douglas fir bud opened.
After that, the output fluctuated when the needles unfurled. The electronics
were essentially insensitive to ambient light and normal light fluctuations.
Acknowledgement
We wish to thank Dr. James Niemeier and Mr. Dan Ceynar at The
University of Iowa for their assistance.
AGU Fall Meeting 2011