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Stackhouse LA, Coops NC, Kuiper SD, Hinch SG, White JC, Tompalski P, Nonis A, Gergel SE. Modeling instream temperature from solar insolation under varying timber harvesting intensities using RPAS laser scanning. Sci Total Environ 2024; 912:169459. [PMID: 38123099 DOI: 10.1016/j.scitotenv.2023.169459] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Revised: 12/03/2023] [Accepted: 12/15/2023] [Indexed: 12/23/2023]
Abstract
Stream temperatures are influenced by the amount of solar insolation they receive. Increasing stream temperatures associated with climate warming pose detrimental health risks to freshwater ecosystems. In British Columbia (BC), Canada, timber harvesting along forested streams is managed using riparian buffer zones of varying widths and designations. Within buffer zones, depending on distance from the stream, selective thinning may be permitted or harvest may be forbidden. In this study, we used airborne laser scanning (ALS) point cloud data acquired via a remotely piloted aircraft system (RPAS) to derive forest canopy characteristics that were then used to estimate daily incoming summer and fall solar insolation for five stream reaches in coastal conifer-dominated temperate forests in Vancouver Island, BC, Canada. We then examined empirical relationships between estimated insolation and actual instream temperature measurements. Based on these empirical relationships, the potential effects of timber harvest on instream temperatures were simulated by comparing scenarios of different riparian forest harvest intensities. Our results indicated that modeled solar insolation explained 43-90 % of the variation in observed stream reach temperatures, and furthermore, when a single cold-water stream reach was excluded explained an overall 81 % of variation. Simulated harvesting scenarios generally projected increases in maximum stream reach temperatures 1-2 °C in summer and early fall months. However, in a full clearcut scenario (i.e. where all trees were removed), maximum stream reach temperatures increased as much as 5.8 °C. Our results emphasize the importance of retaining riparian vegetation for the maintenance of habitable temperatures for freshwater-reliant fish with thermal restrictions. In addition, we demonstrate the feasibility of RPAS-based monitoring of stream reach shading and canopy cover, enabling detailed assessment of environmental stressors faced by fish populations under climate warming.
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Affiliation(s)
- Leanna A Stackhouse
- Department of Forest Resources Management, Faculty of Forestry, University of British Columbia, Vancouver, BC, Canada.
| | - Nicholas C Coops
- Department of Forest Resources Management, Faculty of Forestry, University of British Columbia, Vancouver, BC, Canada
| | - Spencer Dakin Kuiper
- Department of Forest Resources Management, Faculty of Forestry, University of British Columbia, Vancouver, BC, Canada
| | - Scott G Hinch
- Pacific Salmon Ecology and Conservation Laboratory, Department of Forest Conservation Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Joanne C White
- Canadian Forest Service (Pacific Forestry Centre), Natural Resources Canada, Victoria, British Columbia, Canada
| | - Piotr Tompalski
- Canadian Forest Service (Pacific Forestry Centre), Natural Resources Canada, Victoria, British Columbia, Canada
| | - Alyssa Nonis
- Pacific Salmon Ecology and Conservation Laboratory, Department of Forest Conservation Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Sarah E Gergel
- Department of Forest and Conservation Sciences, Faculty of Forestry, University of British Columbia, Vancouver, BC, Canada
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Abstract
The uptake of technologies such as airborne laser scanning (ALS) and more recently digital aerial photogrammetry (DAP) enable the characterization of 3-dimensional (3D) forest structure. These forest structural attributes are widely applied in the development of modern enhanced forest inventories. As an alternative to extensive ALS or DAP based forest inventories, regional forest attribute maps can be built from relationships between ALS or DAP and wall-to-wall satellite data products. To date, a number of different approaches exist, with varying code implementations using different programming environments and tailored to specific needs. With the motivation for open, simple and modern software, we present FOSTER (Forest Structure Extrapolation in R), a versatile and computationally efficient framework for modeling and imputation of 3D forest attributes. FOSTER derives spectral trends in remote sensing time series, implements a structurally guided sampling approach to sample these often spatially auto correlated datasets, to then allow a modelling approach (currently k-NN imputation) to extrapolate these 3D forest structure measures. The k-NN imputation approach that FOSTER implements has a number of benefits over conventional regression based approaches including lower bias and reduced over fitting. This paper provides an overview of the general framework followed by a demonstration of the performance and outputs of FOSTER. Two ALS-derived variables, the 95th percentile of first returns height (elev_p95) and canopy cover above mean height (cover), were imputed over a research forest in British Columbia, Canada with relative RMSE of 18.5% and 11.4% and relative bias of -0.6% and 1.4% respectively. The processing sequence developed within FOSTER represents an innovative and versatile framework that should be useful to researchers and managers alike looking to make forest management decisions over entire forest estates.
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Affiliation(s)
- Martin Queinnec
- Faculty of Forestry, University of British Columbia, Vancouver, British Columbia, Canada
- * E-mail:
| | - Piotr Tompalski
- Faculty of Forestry, University of British Columbia, Vancouver, British Columbia, Canada
| | - Douglas K. Bolton
- Department of Earth & Environment, Boston University, Boston, Massachusetts, United States of America
| | - Nicholas C. Coops
- Faculty of Forestry, University of British Columbia, Vancouver, British Columbia, Canada
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