Instrumental method for reducing error in compression-derived measurements of rainfall interception for individual trees

Stan, John T. Van; Jarvis, Matthew T.; Levia, Delphis F.; Friesen, Jan

doi:10.1080/02626667.2011.590811

Cited by 6 publications

(11 citation statements)

References 33 publications

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“…Then, two orthogonal axes, which pass through the centroid of the trunk cross section, were derived using the operations described in equations (1)-(4) of Van Stan et al [2011a]. These equations rely on the assumption that the elastic modulus (E) of live heartwood and sapwood are statistically indistinct from each other (as reported by Gillette [1914], FPL [1999], Berthier et al [2001], and Passialis and Adamopoulus [2002]).…”

Section: Mechanical Displacement Sensor Installationmentioning

confidence: 99%

“…[8] Interceptometer sensors were precisely installed as in-line pairs, positioned directly over the axes [Van Stan et al, 2011a]. Two pairs of sensors positioned on either side of two orthogonal axes which intersect at the computed centroid are necessary to evaluate how the ''true'' mechanical center compares to the centroid computed via the Van Stan et al…”

Section: Mechanical Displacement Sensor Installationmentioning

confidence: 99%

“…[10] Bending tests were performed to assess how identifiable bending behavior was within the raw signal, evaluate the installation accuracy about the Van Stan et al [2011a] computed centroid, and assess the proximity of this computed centroid to the trees' true mechanical center. Rope was secured to the trunk above the interceptometers (at about 6 m high), where a sideways load was applied to induce bending (Figure 2).…”

Section: Bending Testsmentioning

confidence: 99%

“…Interceptometers monitor trunk compression and relaxation during storm events, largely attributing the mechanical displacement of the trunk to the loading or unloading of water stored on, or evaporated from, the tree canopy [Friesen et al, 2008]. However, without precise sensor positioning, these interceptionrelated strain phenomena can be obscured by significant wind throw and off-center loading signals [Friesen et al, 2008;Van Stan et al, 2011a]. Using the LaserBark TM automated tree measurement system [Van Stan et al, 2010], Van Stan et al [2011a] developed a theoretical installation procedure to enhance interceptometer sensor placement and, thereby, remove off-center loading and wind-related distortions.…”

Section: Introductionmentioning

confidence: 99%

“…However, without precise sensor positioning, these interceptionrelated strain phenomena can be obscured by significant wind throw and off-center loading signals [Friesen et al, 2008;Van Stan et al, 2011a]. Using the LaserBark TM automated tree measurement system [Van Stan et al, 2010], Van Stan et al [2011a] developed a theoretical installation procedure to enhance interceptometer sensor placement and, thereby, remove off-center loading and wind-related distortions. This technical note builds upon our previous theoretical advance by evaluating and validating how well the Van Stan et al…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of an instrumental method to reduce error in canopy water storage estimates via mechanical displacement

Stan

Martin

Friesen

et al. 2013

Water Resources Research

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[1] To improve the water budgeting of forested catchments and inform relevant hydrologic theory regarding water cycling within forests, the scientific community has been seeking simple, inexpensive, direct methods for determining rain water storage on in situ tree canopies. This paper evaluates an installation arrangement and routine for one such method: mechanical displacement sensors placed on a tree's trunk to directly monitor compression under canopy water loading from rainfall. The evaluated installation routine aligns mechanical displacement sensors along orthogonal axes passing through the mechanical center of the trunk to reduce wind-induced noise. The experimental attainment of neutral bending axes for a subject hardwood and softwood tree suggests the routine is precise and approximates the trunk's mechanical center well regardless of differences in cellular axial stiffness between heart and sapwood. When installed in this precise sensor arrangement, bending tests of different loading directions produced a consistent signal ratio between sensor pairs of approximately À1 (1 unit compression/1 unit elongation), allowing the identification and removal of bending strains from the raw strain signals to isolate the compression component attributable to canopy water storage loads. The same experiments performed on sensors just 5 cm off the trunk's computed mechanical center were unable to produce neutral bending axes or consistent signal ratios during bending from variable loading directions. Results from the method evaluation were translated into a data processing technique that is then applied to strain data collected through two sample rain events (one each for the hardwood and softwood trees). The processed strain data showed a clear synchronicity between rainfall and canopy loading, as well as periods of maximized canopy water loading (canopy storage capacity). Our results indicate that the evaluated arrangement and installation procedure for mechanical displacement sensors may be able to provide scientists with simple, direct canopy water storage estimates at high temporal resolution and sensitivity.

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Section: Mechanical Displacement Sensor Installationmentioning

confidence: 99%

Section: Mechanical Displacement Sensor Installationmentioning

confidence: 99%

Section: Bending Testsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Evaluation of an instrumental method to reduce error in canopy water storage estimates via mechanical displacement

Stan

Martin

Friesen

et al. 2013

Water Resources Research

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Evolution of forest precipitation water storage measurement methods

Friesen

Lundquist

Stan

2014

Hydrological Processes

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Abstract:Precipitation intercepted by forests plays a major role in more than one-fourth of the global land area's hydrologic cycle. Direct in situ measurement of intercepted precipitation is challenging, and thus, it is typically indirectly estimated through comparing precipitation under forest cover and in the open. We discuss/compare measurement methods for forest precipitation interception beyond classical budgeting and then recommend future directions for improving water storage estimation. Comparison of techniques shows that methods submerging tree components produce the largest water storage capacity values. Whole-tree lysimeters have been used with great success at quantifying water storage for the integrated system yet are unable to separate trunk versus canopy storage. Remote sensing, particularly signal attenuation, may permit this separation. Mechanical displacement methods show great promise and variety of techniques: pulley/spring system, branch strain sensors, trunk compression sensors and photography. Relating wind sway to water storage also shows great promise with negligible environmental disruption yet is currently at the proof-of-concept stage. Suggested future directions focus on development of common features regarding all discussed methods: (i) measurement uncertainties or processes beyond interception influencing the observed signal, (ii) scaling approaches to move from single tree components to the single-tree and forest scales and (iii) temporal scaling to estimate the relevance of single-interception components over longer timescales. Through addressing these research needs, we hope the scientific community can develop an 'integrated' monitoring plan incorporating multiple measurement techniques to characterize forest-scale water storage dynamics while simultaneously investigating underlying (smaller-scale) components driving those dynamics across the spectrum of precipitation and forest conditions.

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Development and testing of a snow interceptometer to quantify canopy water storage and interception processes in the rain/snow transition zone of the North Cascades, Washington, USA

et al. 2013

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[1] Tree canopy snow interception is a significant hydrological process, capable of removing up to 60% of snow from the ground snowpack. Our understanding of canopy interception has been limited by our ability to measure whole canopy water storage in an undisturbed forest setting. This study presents a relatively inexpensive technique for directly measuring snow canopy water storage using an interceptometer, adapted from Friesen et al. (2008). The interceptometer is composed of four linear motion position sensors distributed evenly around the tree trunk. We incorporate a trunk laser-mapping installation method for precise sensor placement to reduce signal error due to sensor misalignment. Through calibration techniques, the amount of canopy snow required to produce the measured displacements can be calculated. We demonstrate instrument performance on a western hemlock (Tsuga heterophylla) for a snow interception event in November 2011. We find a snow capture efficiency of 83 6 15% of accumulated ground snowfall with a maximum storage capacity of 50 6 8 mm snow water equivalent (SWE). The observed interception event is compared to simulated interception, represented by the variable infiltration capacity (VIC) hydrologic model. The model generally underreported interception magnitude by 33% using a leaf area index (LAI) of 5 and 16% using an LAI of 10. The interceptometer captured intrastorm accumulation and melt rates up to 3 and 0.75 mm SWE h À1 , respectively, which the model failed to represent. While further implementation and validation is necessary, our preliminary results indicate that forest interception magnitude may be underestimated in maritime areas.

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Instrumental method for reducing error in compression-derived measurements of rainfall interception for individual trees

Cited by 6 publications

References 33 publications

Evaluation of an instrumental method to reduce error in canopy water storage estimates via mechanical displacement

Evaluation of an instrumental method to reduce error in canopy water storage estimates via mechanical displacement

Evolution of forest precipitation water storage measurement methods

Development and testing of a snow interceptometer to quantify canopy water storage and interception processes in the rain/snow transition zone of the North Cascades, Washington, USA

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