Bibliografie tematiche / Canopy structure

Letteratura scientifica selezionata sul tema "Canopy structure"

Autore: Grafiati
Pubblicato: 4 giugno 2021
Ultima modifica: 10 marzo 2023

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Articoli di riviste sul tema "Canopy structure"

1

Vanderbilt, V. C. "Measuring plant canopy structure". Remote Sensing of Environment 18, n. 3 (dicembre 1985): 281–94. http://dx.doi.org/10.1016/0034-4257(85)90063-x.

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Daughtry, Craig S. T. "Direct measurements of canopy structure". Remote Sensing Reviews 5, n. 1 (gennaio 1990): 45–60. http://dx.doi.org/10.1080/02757259009532121.

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Chen, Zhe, Xu Dong Li, Shao Guang Shi, Hong Zhi Jiang e Hui Jie Zhao. "Structured-Light Based Rapid 3D Measurement of Plant Canopy Structure". Applied Mechanics and Materials 701-702 (dicembre 2014): 549–53. http://dx.doi.org/10.4028/www.scientific.net/amm.701-702.549.

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Density three dimensional plant canopy structure data has numerous applications in agriculture, but many existing 3D data collection approaches are time-consuming. In this paper, we present a measurement system based on structured-light for plant canopy structure data collection. The structured-light projector projects laser beam reflected by dual-oscillating mirror, arrives to the plant canopy, which is captured by a camera. We propose a new scanning mode, that is, during one exposure time of CCD camera, one mirror keeps moving in high frequency and small angle, while the other one maintains the same position, so that we can get a laser stripe rather than a spot in each image, from which about 100 sub-pixel centers of laser stripe can be extracted. Experiments show that the measurement system can rapid collect three dimensional information of the plant.
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Song, Bo, Jiquan Chen, Paul V. Desander, David D. Reed, Gay A. Bradshaw e Jerry F. Franklin. "Modeling canopy structure and heterogeneity across scales: From crowns to canopy". Forest Ecology and Management 96, n. 3 (settembre 1997): 217–29. http://dx.doi.org/10.1016/s0378-1127(97)00021-2.

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Barradas, Victor L., Hamlyn G. Jones e Jerry A. Clark. "Sunfleck dynamics and canopy structure in a Phaseolus vulgaris L. canopy". International Journal of Biometeorology 42, n. 1 (9 settembre 1998): 34–43. http://dx.doi.org/10.1007/s004840050081.

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Kane, Van R., Rolf F. Gersonde, James A. Lutz, Robert J. McGaughey, Jonathan D. Bakker e Jerry F. Franklin. "Patch dynamics and the development of structural and spatial heterogeneity in Pacific Northwest forests". Canadian Journal of Forest Research 41, n. 12 (dicembre 2011): 2276–91. http://dx.doi.org/10.1139/x11-128.

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Over time, chronic small-scale disturbances within forests should create distinct stand structures and spatial patterns. We tested this hypothesis by measuring the structure and spatial arrangement of gaps and canopy patches. We used airborne LiDAR data from 100 sites (cumulative 11.2 km2) in the Pacific Northwest, USA, across a 643 year chronosequence to measure canopy structure, patch and gap diversity, and scales of variance. We used airborne LiDAR’s ability to identify strata in canopy surface height to distinguish patch spatial structures as homogeneous canopy structure, matrix–patch structures, or patch mosaics. We identified six distinct stand structure classes that were associated with the canopy closure, competitive exclusion, maturation, and three patch mosaics stages of late seral forest development. Structural variance peaked in all classes at the tree-to-tree and tree-to-gap scales (10–15 m), but many sites maintained high variance at scales >30 m and up to 200 m, emphasizing the high patch-to-patch heterogeneity. The time required to develop complex patch and gap structures was highly variable and was likely linked to individual site circumstances. The high variance at larger scales appears to be an emergent property that is not a simple propagation of processes observed at smaller spatial scales.
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Lim, Kevin, Paul Treitz, Michael Wulder, Benoît St-Onge e Martin Flood. "LiDAR remote sensing of forest structure". Progress in Physical Geography: Earth and Environment 27, n. 1 (marzo 2003): 88–106. http://dx.doi.org/10.1191/0309133303pp360ra.

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Light detection and ranging (LiDAR) technology provides horizontal and vertical information at high spatial resolutions and vertical accuracies. Forest attributes such as canopy height can be directly retrieved from LiDAR data. Direct retrieval of canopy height provides opportunities to model above-ground biomass and canopy volume. Access to the vertical nature of forest ecosystems also offers new opportunities for enhanced forest monitoring, management and planning.
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Valverde, Teresa, e Jonathan Silvertown. "CANOPY CLOSURE RATE AND FOREST STRUCTURE". Ecology 78, n. 5 (luglio 1997): 1555–62. http://dx.doi.org/10.1890/0012-9658(1997)078[1555:ccrafs]2.0.co;2.

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Lang, A. Richard G. "An instrument for measuring canopy structure". Remote Sensing Reviews 5, n. 1 (gennaio 1990): 61–71. http://dx.doi.org/10.1080/02757259009532122.

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FINNIGAN, JOHN J., ROGER H. SHAW e EDWARD G. PATTON. "Turbulence structure above a vegetation canopy". Journal of Fluid Mechanics 637 (7 ottobre 2009): 387–424. http://dx.doi.org/10.1017/s0022112009990589.

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We compare the turbulence statistics of the canopy/roughness sublayer (RSL) and the inertial sublayer (ISL) above. In the RSL the turbulence is more coherent and more efficient at transporting momentum and scalars and in most ways resembles a turbulent mixing layer rather than a boundary layer. To understand these differences we analyse a large-eddy simulation of the flow above and within a vegetation canopy. The three-dimensional velocity and scalar structure of a characteristic eddy is educed by compositing, using local maxima of static pressure at the canopy top as a trigger. The characteristic eddy consists of an upstream head-down sweep-generating hairpin vortex superimposed on a downstream head-up ejection-generating hairpin. The conjunction of the sweep and ejection produces the pressure maximum between the hairpins, and this is also the location of a coherent scalar microfront. This eddy structure matches that observed in simulations of homogeneous-shear flows and channel flows by several workers and also fits with earlier field and wind-tunnel measurements in canopy flows. It is significantly different from the eddy structure educed over smooth walls by conditional sampling based only on ejections as a trigger. The characteristic eddy was also reconstructed by empirical orthogonal function (EOF) analysis, when only the dominant, sweep-generating head-down hairpin was recovered, prompting a re-evaluation of earlier results based on EOF analysis of wind-tunnel data. A phenomenological model is proposed to explain both the structure of the characteristic eddy and the key differences between turbulence in the canopy/RSL and the ISL above. This model suggests a new scaling length that can be used to collapse turbulence moments over vegetation canopies.
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Tesi sul tema "Canopy structure"

1

Burlison, Alison Jean. "Sward canopy structure and ingestive behaviour in grazing animals". Thesis, University of Edinburgh, 1987. http://hdl.handle.net/1842/27546.

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McWilliam, Simon Charles. "Plant establishment, canopy structure and yield formation in oilseed rape". Thesis, University of Nottingham, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243684.

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Mohd, Yusah Kalsum binti. "Ant community structure in the high canopy of lowland dipterocarp forest". Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609653.

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Newell, Felicity L. "A Bird’s Eye View of the Forest: How Does Canopy Openness Affect Canopy Songbirds?" The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1276875484.

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Joys, Andrew Colin. "Determinants of songbird community structure in a woodland environment : coppice in lowland Europe". Thesis, University of East Anglia, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251560.

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Lee, Alex C., e alexanderlee@aapt net au. "Utilising airborne scanning laser (LiDAR) to improve the assessment of Australian native forest structure". The Australian National University. Fenner School of Environment and Society, 2008. http://thesis.anu.edu.au./public/adt-ANU20090127.222600.

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Abstract (sommario):
Enhanced understanding of forest stocks and dynamics can be gained through improved forest measurement, which is required to assist with sustainable forest management decisions, meet Australian and international reporting needs, and improve research efforts to better respond to a changing climate. Integrated sampling schemes that utilise a multi-scale approach, with a range of data sourced from both field and remote sensing, have been identified as a way to generate the required forest information. Given the multi-scale approach proposed by these schemes, it is important to understand how scale potentially affects the interpretation and reporting of forest from a range of data. ¶ To provide improved forest assessment at a range of scales, this research has developed a strategy for facilitating tree and stand level retrieval of structural attributes within an integrated multi-scale analysis framework. The research investigated the use of fine-scale (~1m) airborne Light Detection and Ranging (LiDAR) data (1,125 ha in central Queensland, and 60,000 ha in NE Victoria) to calibrate other remotely sensed data at the two study sites. The strategy refines forest structure mapping through three-dimensional (3D) modelling combined with empirical relationships, allowing improved estimation of maximum and predominant height, as well as foliage and crown cover at multiple scales. Tree stems (including those in the sub-canopy) were located using a height scaled crown openness index (HSCOI), which integrated the 3D density of canopy elements within the vertical profile into a two-dimensional spatial layer. The HSCOI modelling also facilitated the reconstruction of the 3D distribution of foliage and branches (of varying size and orientation) within the forest volume. ¶ Comparisons between forests at the Queensland and NE Victorian study sites indicated that accurate and consistent retrieval of cover and height metrics could be achieved at multiple scales, with the algorithms applicable for semi-automated use in other forests with similar structure. This information has facilitated interpretation and evaluation of Landsat imagery and ICESat satellite laser data for forest height and canopy cover retrieval. The development of a forest cover translation matrix allows a range of data and metrics to be compared at the plot scale, and has initiated the development of continuous transfer functions between the metrics and datasets. These data have been used subsequently to support interpretation of SAR data, by providing valuable input to 2D and 3D radar simulation models. Scale effects have been identified as being significant enough to influence national forest class reporting in more heterogeneous forests, thus allowing the most appropriate use and integration of remote sensed data at a range of scales. An empirically based forest minimum mapping area of 1 ha for reporting is suggested. The research has concluded that LiDAR can provide calibration information just as detailed and possibly more accurately than field measurements for many required forest attributes. Therefore the use of LiDAR data offers a unique opportunity to bridge the gap between accurate field plot structural information and stand to landscape scale sampling, to provide enhanced forest assessment in Australia.
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Seed, Evan D. "Retrieval of forest canopy structure from high-resolution airborne digital camera imagery". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0005/MQ36848.pdf.

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Goff, Bruce Franklin. "Dynamics of canopy structure and soil surface cover in a semiarid grassland". Thesis, The University of Arizona, 1985. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_e9791_1985_503_sip1_w.pdf&type=application/pdf.

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Van, Leeuwen Martin. "Using forest structure to model vertical variations of canopy radiation and productivity". Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/45732.

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The productivity of autotrophic organisms affects all life on Earth; hence, gaining insight in the variability of autotrophic productivity has received significant research interest. At cell to organism level, much knowledge has been gained under controlled conditions through laboratory analysis. At the stand level and beyond, control over the driving variables is limited, and hence experiments have relied on extensive time series, and geospatial analysis to observe changes in productivity across a wide range of environmental conditions. Significant technologies at these scales are eddy covariance that provides point sample estimates of productivity by measuring CO₂ fluxes between land and atmosphere, and remote sensing that provides for extrapolating eddy-covariance measurements across the landscape using canopy-reflectance data. Challenges in fusing eddy covariance with remote sensing relate to the limited capacity of airborne and spaceborne instruments to observe changes in the biophysical state of deep canopy strata; hence, eddy-covariance estimates that capture the productivity of an arbitrarily dense canopy volume are extrapolated based on top-of-canopy reflectance data. Proximal-sensing technology extends the acquisition of reflectance data to arbitrary locations within the canopy; however, these data are affected by the immediate canopy structure surrounding the sensor that introduces a sensor-location bias, and the direct use of these data in stand-level models is therefore challenging. This thesis explores the simulation of photosynthetic down-regulation using geometrically explicit forest models and meteorological records. The geometrically explicit models are constructed by combining laser-scanning data with tree-regeneration models, and are used to simulate a time series of leaf-level incident radiation. The parameters of a leaf-level photosynthesis model are then optimized against eddy-covariance productivity estimates. Finally, the potential of geometrically explicit models for the fusion of remote sensing and proximal sensing data is discussed.
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Houldcroft, Caroline. "Measuring and modelling the surface temperature and structure of a maize canopy". Thesis, University of Reading, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.408336.

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Libri sul tema "Canopy structure"

1

Crookston, Nicholas L. Percent canopy cover and stand structure statistics from the forest vegetation simulator. Ogden, UT (324 25th St., Ogden 84401): U.S. Dept. of Agriculture, Forest Service, Rocky Mountain Research Station, 1999.

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Crookston, Nicholas L. Percent canopy cover and stand structure statistics from the forest vegetation simulator. Ogden, UT (324 25th St., Ogden 84401): U.S. Dept. of Agriculture, Forest Service, Rocky Mountain Research Station, 1999.

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N, Gray Andrew, Garman, Steven L. (Steven Lee), 1955- e Pacific Northwest Research Station (Portland, Or.), a cura di. Canopy structure on forest lands in western Oregon: Differences among forest types and stand ages. Portland, OR: U.S. Dept. of Agriculture, Forest Service, Pacific Northwest Research Station, 2009.

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Draaijers, Geert. The variability of atmospheric deposition to forests: The effects of canopy structure and forest edges. Utrecht: Koninklijk Nederlands Aardrijkskundig Genootschap, 1993.

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Draaijers, Geert. The variability of atmospheric deposition to forests: The effects of canopy structure and forest edges. Utrecht: Koninklijk Nederlands Aardrijkskundig Genootschap, 1993.

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6

J, Harding D., e Goddard Space Flight Center, a cura di. SLICER airborne laser altimeter characterization of canopy structure and sub-canopy topography for the BOREAS northern and southern study regions: Instrument and data product description. Greenbelt, Md: National Aeronautics and Space Administration, Goddard Space Flight Center, 2000.

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J, Harding D., e Goddard Space Flight Center, a cura di. SLICER airborne laser altimeter characterization of canopy structure and sub-canopy topography for the BOREAS northern and southern study regions: Instrument and data product description. Greenbelt, Md: National Aeronautics and Space Administration, Goddard Space Flight Center, 2000.

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Bergeron, Marie-Josée. Age structure of white pine (Pinus strobus L.): Regeneration under a jack pine (Pinus banksiana Lamb.) canopy. Sudbury, Ont: Laurentian University, Department of Biology, 1994.

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Takao, Fujimori, Whitehead David, International Union of Forestry Research Organizations. Working Group S1.06-02. e No rin Suisansho Ringyo Shikenjo (Japan), a cura di. Crown and canopy structure in relation to productivity: Proceedings of an international workshop held in Japan, 14-20 October 1985. Tsukuba Norin Kenkyu Danchi-Nai, Ibaraki, Japan: Forestry and Forest Products Research Institute, 1986.

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D, Child R., Pinfield N. J, AFRC Institute of Arable Crops Research. e British Plant Growth Regulator Group., a cura di. Manipulation of canopy structure in arable crops: Proceedings of a meeting held at the AFRC Institute of Arable Crops Research ... Harpenden ... 19 September, 1990. Bristol: British Plant Growth Regulator Group, 1991.

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Capitoli di libri sul tema "Canopy structure"

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Norman, John M., e Gaylon S. Campbell. "Canopy structure". In Plant Physiological Ecology, 301–25. Dordrecht: Springer Netherlands, 2000. http://dx.doi.org/10.1007/978-94-010-9013-1_14.

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Norman, John M., e Gaylon S. Campbell. "Canopy structure". In Plant Physiological Ecology, 301–25. Dordrecht: Springer Netherlands, 1989. http://dx.doi.org/10.1007/978-94-009-2221-1_14.

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Nobel, P. S., I. N. Forseth e S. P. Long. "Canopy structure and light interception". In Photosynthesis and Production in a Changing Environment, 79–90. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-010-9626-3_6.

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Nobel, P. S., I. N. Forseth e S. P. Long. "Canopy structure and light interception". In Photosynthesis and Production in a Changing Environment, 79–90. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-1566-7_6.

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Wirth, Rainer, Hubert Herz, Ronald J. Ryel, Wolfram Beyschlag e Bert Hölldobler. "Canopy Structure of the Forest". In Herbivory of Leaf-Cutting Ants, 71–82. Berlin, Heidelberg: Springer Berlin Heidelberg, 2003. http://dx.doi.org/10.1007/978-3-662-05259-4_6.

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van der Woerd, Jan Dirk, Rostislav Chudoba e Josef Hegger. "Canopy – Doubly Curved Folded Plate Structure". In High Tech Concrete: Where Technology and Engineering Meet, 2512–20. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-59471-2_286.

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Moffett, Mark W. "Comparative Canopy Biology and the Structure of Ecosystems". In Treetops at Risk, 13–54. New York, NY: Springer New York, 2013. http://dx.doi.org/10.1007/978-1-4614-7161-5_3.

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Yanoviak, Stephen P. "Effects of lianas on canopy arthropod community structure". In Ecology of Lianas, 343–61. Chichester, UK: John Wiley & Sons, Ltd, 2014. http://dx.doi.org/10.1002/9781118392409.ch24.

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Sychterz, A. C. "Adaptive aluminum tensegrity structure as a bike parking canopy". In Structures and Architecture A Viable Urban Perspective?, 476–84. London: CRC Press, 2022. http://dx.doi.org/10.1201/9781003023555-57.

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Ibaraki, Yasuomi. "Evaluation of Spatial Light Environment and Plant Canopy Structure". In LED Lighting for Urban Agriculture, 137–49. Singapore: Springer Singapore, 2016. http://dx.doi.org/10.1007/978-981-10-1848-0_10.

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Atti di convegni sul tema "Canopy structure"

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Li, Yunmei, Jay Gao e Yong Zha. "Impact of rice canopy structure on canopy reflectance spectra". In Remote Sensing and Space Technology for Multidisciplinary Research and Applications, a cura di Qingxi Tong, Xiuwan Chen, Allen Huang e Wei Gao. SPIE, 2006. http://dx.doi.org/10.1117/12.673663.

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Knyazikhin, Yu, M. Schull, Liang Hu, R. Myneni e P. L. Carmona. "Canopy spectral invariants for remote sensing of canopy structure". In 2009 First Workshop on Hyperspectral Image and Signal Processing: Evolution in Remote Sensing (WHISPERS). IEEE, 2009. http://dx.doi.org/10.1109/whispers.2009.5289105.

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Pantano-Rubino, Carlos, Kostas Karagiozis, Ramji Kamakoti e Fehmi Cirak. "Computational Fluid-Structure Interaction of DGB Parachutes in Compressible Fluid Flow". In ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting collocated with 8th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2010. http://dx.doi.org/10.1115/fedsm-icnmm2010-30898.

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This paper describes large-scale simulations of compressible flows over a supersonic disk-gap-band parachute system. An adaptive mesh refinement method is used to resolve the coupled fluid-structure model. The fluid model employs large-eddy simulation to describe the turbulent wakes appearing upstream and downstream of the parachute canopy and the structural model employed a thin-shell finite element solver that allows large canopy deformations by using subdivision finite elements. The fluid-structure interaction is described by a variant of the Ghost-Fluid method. The simulation was carried out at Mach number 1.96 where strong nonlinear coupling between the system of bow shocks, turbulent wake and canopy is observed. It was found that the canopy oscillations were characterized by a breathing type motion due to the strong interaction of the turbulent wake and bow shock upstream of the flexible canopy.
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Liu, Chuanping, e Jian Jia. "Study on Mechanical Property of Reticulated Shell Structure Canopy Considering Elevated-effect of Viaduct in High-speed Rail Station". In IABSE Congress, Nanjing 2022: Bridges and Structures: Connection, Integration and Harmonisation. Zurich, Switzerland: International Association for Bridge and Structural Engineering (IABSE), 2022. http://dx.doi.org/10.2749/nanjing.2022.0232.

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<p>Some high-speed rail stations use reinforced concrete reticulated shell as its canopy structure in China. This structure has advantages of beautiful shape, large span and convenient maintenance. This paper mainly studies the influence of the viaduct structure on mechanical property of reticulated shell structure upper, and establishes the overall finite element model of station including the viaduct and canopy structure. The study results show that due to the relatively large structural stiffness of the viaduct, it can select a separate model of the canopy from the whole station structure to analysis, and can meet the safety requirements of the canopy structure.</p>
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Govindaraj, Karthik, Kakade Ritesh, Ramadas Narayanan, A. Rajkumar e Venkatesan D. "Polypropylene Copolymer Automotive Canopy Plastic Structure Application". In WCX World Congress Experience. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 2018. http://dx.doi.org/10.4271/2018-01-0157.

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Jun Zhang, Yi-Ming Wang, Qiao-Xue Dong e Jia-Lin Hou. "Effect of Different Planting Density on Cotton Canopy Structure, Canopy Photosynthesis and Yield Formation". In 2006 Portland, Oregon, July 9-12, 2006. St. Joseph, MI: American Society of Agricultural and Biological Engineers, 2006. http://dx.doi.org/10.13031/2013.20608.

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Wang, Zhuosen, Crystal B. Schaaf, Lewis Philip, Yuri Knyazikhin, Mitchell A. Schull, Alan H. Strahler, Ranga B. Myneni e Mark Chopping. "Canopy vertical structure using MODIS Bidirectional Reflectance data". In 2010 2nd Workshop on Hyperspectral Image and Signal Processing: Evolution in Remote Sensing (WHISPERS). IEEE, 2010. http://dx.doi.org/10.1109/whispers.2010.5594952.

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Brigot, Guillaume, Marc Simard, Elise Koeniguer e Cedric Taillandier. "Prediction of forest canopy structure from PolInSAR dataset". In 2017 IEEE International Geoscience and Remote Sensing Symposium (IGARSS). IEEE, 2017. http://dx.doi.org/10.1109/igarss.2017.8127954.

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Ling, Zhu, e Zou Jie. "Obtaining three-dimensional forest canopy structure using TLS". In Optical Engineering + Applications, a cura di Wei Gao e Hao Wang. SPIE, 2008. http://dx.doi.org/10.1117/12.793280.

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Yang, Yi, Xuefen Wan, Jian Cui, Tao Zheng, Xueqin Jiang e Jingwen Zhang. "Smartphone based hemispherical photography for canopy structure measurement". In International Conference on Optical Instruments and Technology 2017: Optoelectronic Measurement Technology and System, a cura di Jigui Zhu, Kexin Xu, Liquan Dong, Hwa-Yaw Tam e Hai Xiao. SPIE, 2018. http://dx.doi.org/10.1117/12.2285911.

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Rapporti di organizzazioni sul tema "Canopy structure"

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Crookston, Nicholas L., e Albert R. Stage. Percent canopy cover and stand structure statistics from the Forest Vegetation Simulator. Ft. Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, 1999. http://dx.doi.org/10.2737/rmrs-gtr-24.

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McIntosh, Anne C. S., Andrew N. Gray e Steven L. Garman. Canopy structure on forest lands in western Oregon: differences among forest types and stand ages. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station, 2009. http://dx.doi.org/10.2737/pnw-gtr-794.

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Addessi, Andrew. Urban Impacts to Forest Productivity, Soil Quality, and Canopy Structure in Forest Park, Portland, Oregon. Portland State University Library, gennaio 2000. http://dx.doi.org/10.15760/etd.5769.

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4

Tanny, Josef, Gabriel Katul, Shabtai Cohen e Meir Teitel. Micrometeorological methods for inferring whole canopy evapotranspiration in large agricultural structures: measurements and modeling. United States Department of Agriculture, ottobre 2015. http://dx.doi.org/10.32747/2015.7594402.bard.

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Abstract (sommario):
Original objectives and revisions The original objectives as stated in the approved proposal were: (1) To establish guidelines for the use of micrometeorological techniques as accurate, reliable and low-cost tools for continuous monitoring of whole canopy ET of common crops grown in large agricultural structures. (2) To adapt existing methods for protected cultivation environments. (3) To combine previously derived theoretical models of air flow and scalar fluxes in large agricultural structures (an outcome of our previous BARD project) with ET data derived from application of turbulent transport techniques for different crops and structure types. All the objectives have been successfully addressed. The study was focused on both screenhouses and naturally ventilated greenhouses, and all proposed methods were examined. Background to the topic Our previous BARD project established that the eddy covariance (EC) technique is suitable for whole canopy evapotranspiration measurements in large agricultural screenhouses. Nevertheless, the eddy covariance technique remains difficult to apply in the farm due to costs, operational complexity, and post-processing of data – thereby inviting alternative techniques to be developed. The subject of this project was: 1) the evaluation of four turbulent transport (TT) techniques, namely, Surface Renewal (SR), Flux-Variance (FV), Half-order Time Derivative (HTD) and Bowen Ratio (BR), whose instrumentation needs and operational demands are not as elaborate as the EC, to estimate evapotranspiration within large agricultural structures; and 2) the development of mathematical models able to predict water savings and account for the external environmental conditions, physiological properties of the plant, and structure properties as well as to evaluate the necessary micrometeorological conditions for utilizing the above turbulent transfer methods in such protected environments. Major conclusions and achievements The major conclusions are: (i) the SR and FV techniques were suitable for reliable estimates of ET in shading and insect-proof screenhouses; (ii) The BR technique was reliable in shading screenhouses; (iii) HTD provided reasonable results in the shading and insect proof screenhouses; (iv) Quality control analysis of the EC method showed that conditions in the shading and insect proof screenhouses were reasonable for flux measurements. However, in the plastic covered greenhouse energy balance closure was poor. Therefore, the alternative methods could not be analyzed in the greenhouse; (v) A multi-layered flux footprint model was developed for a ‘generic’ crop canopy situated within a protected environment such as a large screenhouse. The new model accounts for the vertically distributed sources and sinks within the canopy volume as well as for modifications introduced by the screen on the flow field and microenvironment. The effect of the screen on fetch as a function of its relative height above the canopy is then studied for the first time and compared to the case where the screen is absent. The model calculations agreed with field experiments based on EC measurements from two screenhouse experiments. Implications, both scientific and agricultural The study established for the first time, both experimentally and theoretically, the use of four simple TT techniques for ET estimates within large agricultural screenhouses. Such measurements, along with reliable theoretical models, will enable the future development of lowcost ET monitoring system which will be attainable for day-to-day use by growers in improving irrigation management.
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5

Short, Mary, e Sherry Leis. Vegetation monitoring in the Manley Woods unit at Wilson’s Creek National Battlefield: 1998–2020. A cura di Tani Hubbard. National Park Service, giugno 2022. http://dx.doi.org/10.36967/nrr-2293615.

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Abstract (sommario):
Natural resource management at Wilson’s Creek National Battlefield (NB) is guided by our understanding of the woodlands and prairies at the time of the Civil War battle in 1861. This report is focused on the Manley Woods unit of the park. This unit is an oak-hickory woodland in the Springfield Plain subsection of the Ozarks. Canopy closure for Missouri oak woodlands can be highly variable and ranges from 30–100% across the spectrum of savanna, open woodland, and closed woodland types. In 1861, the woodland was likely a savanna community. Changes in land use (e.g., fire exclusion) caused an increase in tree density in woodlands at Wilson’s Creek NB and across the Ozarks. Savannas and open woodlands transitioned to closed canopy woodlands over time. Park management plans include restoring the area to a savanna/open woodland structure. Prescribed fire was reintroduced to Wilson’s Creek NB in 1988 and continues as the primary mechanism for reducing the tree canopy. The Manley Woods unit of Wilson’s Creek NB has been subject to intense natural and anthropogenic disturbance events such as a tornado in 2003, timber removal in 2005, prescribed fires in 2006, 2009, and 2019, an ice storm in 2007, and periodic drought. The Heartland Inventory and Monitoring Network (hereafter, Heartland Network) installed four permanent monitoring sites within the Manley Woods area of the park in 1997. Initially, we assessed ground flora and regeneration within the sites (1998–1999). We added fuel sampling after the 2003 tornado. Although overstory sampling occurred prior to the tornado, the protocol was not yet stabilized and pre-2003 overstory data were not included in these analyses. In this report, we focus on the overstory, tree regeneration, and ground cover metrics; ground flora data will be assessed in future analyses. Heartland Network monitoring data reveal that Manley Woods has undergone substantial change in canopy cover and midstory trees since 1998. While basal area and density metrics classify Manley Woods as an open woodland, the closed canopy of the midstory and overstory reveal a plant community that is moving toward closed woodland or forest structure. The most recent fire in 2019 was patchy and mild, resulting in continued increases in fuels. Ground cover metrics indicate infrequent disturbance since leaf litter continued to increase. Management objectives to restore savanna or woodland composition and structure to the Manley Woods overstory, regeneration layer, and ground cover will require implementation of prescribed fire in the future. Repeated fires can thin midstory trees and limit less fire tolerant early seral species. Additionally, mechanical or chemical treatments to reduce undesirable tree species should be considered for woodland restoration. Decreasing canopy closure is an important and essential step toward the restoration of a functioning savanna/open woodland plant community in Manley Woods. Treatments that thin the midstory and reduce fuel loading will also benefit these plant communities. With the anticipated changing climate, maintaining an open woodland community type may also provide resilience through management for native species tolerant of increasingly warmer temperatures.
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Weissinger, Rebecca, e Dana Witwicki. Riparian monitoring of wadeable streams at Courthouse Wash, Arches National Park: Summary report, 2010–2019. A cura di Alice Wondrak Biel. National Park Service, novembre 2021. http://dx.doi.org/10.36967/nrr-2287907.

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The goal of Northern Colorado Plateau Network (NCPN) riparian monitoring is to determine long-term trends in hydrologic, geomorphic, and vegetative properties of wadeable streams in the context of changes in other ecological drivers, stressors, and processes. This information is intended to provide early warning of resource degradation and determine natural variability of wadeable streams. This report summarizes NCPN monitoring of Courthouse Wash in Arches National Park (NP) from 2010 to 2019. The focus of this report is to (1) present geomorphology and vegetation data from five reaches monitored in Courthouse Wash from 2010 to 2015, and (2) examine patterns in water availability at one monitoring reach from November 2010 to December 2019. Vegetation sampling and geomorphology surveys were suspended in 2016 due to budget cuts; this report presents baseline data for future comparisons. The NCPN has five monitoring reaches located between the inflow of Sevenmile Canyon, a major tributary, and the terminus of Courthouse Wash, at the Colorado River. Two reaches (2, 5) are located in Upper Courthouse Wash, and three (1, 4, 7) in Lower Courthouse Wash. Hydrologic monitoring wells are installed only at Reach 1. During our monitoring period, which included drought years in 2012 and 2018 and a wetter-than-average period from fall 2013 to 2014, groundwater levels showed steep declines corresponding to the start of the growing season each year. Hot, dry summers and falls in 2012, 2018, and 2019 showed the deepest troughs in groundwater levels. Active monsoon years helped elevate summer and fall groundwater levels in 2013 and 2014. Continued monitoring will help us better understand the relationship of climate and water availability at this reach. A geomorphic survey was completed once for reaches 2, 4, and 7, and twice for reaches 5 and 1. Powerful floods during our monitoring period resulted in aggradation of the channel in reaches 5 and 1, which were first surveyed in March 2013. Flooding in September 2013 resulted in an average of 0.24 meters of deposition found in the channel thalweg at Reach 1 in March 2014. Storm events in May 2014 caused additional aggradation. In March 2015, an average of 0.41 meters of deposition was recorded in the channel thalweg at Reach 5, with 0.32 meters of deposition between the vegetation transect headpins compared to the 2013 data. The riparian vegetation recorded at our monitoring reaches is consistent with an open-canopy Fremont cottonwood woodland with a diverse understory. Canopy closure ranged from 29% to 52%. Measurements were sensitive enough to detect a 10% reduction in canopy closure at Reach 5 during a pest infestation in June 2013. Canopy closure subsequently rebounded at the reach by 2015. Total obligate and facultative wetland cover ranged from 7% to 26%. Fremont cottonwood seedlings, saplings, and overstory trees were present at all reaches, indicating good potential for future regeneration of the canopy structure. These data can serve as a baseline for comparison with future monitoring efforts. One area of management concern is that exotic-plant frequency and cover were relatively high in all monitoring reaches. Exotic cover ranged from 2% to 30%. High exotic cover was related to years with high cover of annual brome grasses. High cover of exotic grasses is associated with increased wildfire risk in southwestern riparian systems, which are not well-adapted to fire. Managers should be prepared for this increased risk following wet winters that promote annual brome grass cover. Beaver activity was noted throughout bedrock-constrained reaches in Courthouse Wash. Beaver activity can reduce adjacent woody riparian vegetation cover, but it also contributes to maintaining a higher water table and persistent surface water. Climate change is likely to be an increasingly significant stressor in Courthouse Wash, as hotter, drier conditions decrease water levels and increase drought stress...
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7

Leis, Sherry. Vegetation community monitoring at Lincoln Boyhood National Memorial: 2011–2019. National Park Service, aprile 2021. http://dx.doi.org/10.36967/nrr-2284711.

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Lincoln Boyhood National Memorial celebrates the lives of the Lincoln family including the final resting place of Abraham’s mother, Nancy Hanks Lincoln. Lincoln’s childhood in Indiana was a formative time in the life our 16th president. When the Lincoln family arrived in Indiana, the property was covered in the oak-hickory forest type. They cleared land to create their homestead and farm. Later, designers of the memorial felt that it was important to restore woodlands to the site. The woodlands would help visitors visualize the challenges the Lincoln family faced in establishing and maintaining their homestead. Some stands of woodland may have remained, but significant restoration efforts included extensive tree planting. The Heartland Inventory and Monitoring Network began monitoring the woodland in 2011 with repeat visits every four years. These monitoring efforts provide a window into the composition and structure of the wood-lands. We measure both overstory trees and the ground flora within four permanently located plots. At these permanent plots, we record each species, foliar cover estimates of ground flora, diameter at breast height of midstory and overstory trees, and tree regeneration frequency (tree seedlings and saplings). The forest species composition was relatively consistent over the three monitoring events. Climatic conditions measured by the Palmer Drought Severity Index indicated mild to wet conditions over the monitoring record. Canopy closure continued to indicate a forest structure with a closed canopy. Large trees (>45 cm DBH) comprised the greatest amount of tree basal area. Sugar maple was observed to have the greatest basal area and density of the 23 tree species observed. The oaks characteristic of the early woodlands were present, but less dominant. Although one hickory species was present, it was in very low abundance. Of the 17 tree species recorded in the regeneration layer, three species were most abundant through time: sugar maple (Acer saccharum), red bud (Cercis canadensis), and ash (Fraxinus sp.). Ash recruitment seemed to increase over prior years and maple saplings transitioned to larger size classes. Ground flora diversity was similar through time, but alpha and gamma diversity were slightly greater in 2019. Percent cover by plant guild varied through time with native woody plants and forbs having the greatest abundance. Nonnative plants were also an important part of the ground flora composition. Common periwinkle (Vinca minor) and Japanese honeysuckle (Lonicera japonica) continued to be the most abundant nonnative species, but these two species were less abundant in 2019 than 2011. Unvegetated ground cover was high (mean = 95%) and increased by 17% since 2011. Bare ground increased from less than 1% in 2011 to 9% in 2019, but other ground cover elements were similar to prior years. In 2019, we quantified observer error by double sampling two plots within three of the monitoring sites. We found total pseudoturnover to be about 29% (i.e., 29% of the species records differed between observers due to observer error). This 29% pseudoturnover rate was almost 50% greater than our goal of 20% pseudoturnover. The majority of the error was attributed to observers overlooking species. Plot frame relocation error likely contributed as well but we were unable to separate it from overlooking error with our design.
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8

Tanny, Josef, Gabriel Katul, Shabtai Cohen e Meir Teitel. Application of Turbulent Transport Techniques for Quantifying Whole Canopy Evapotranspiration in Large Agricultural Structures: Measurement and Theory. United States Department of Agriculture, gennaio 2011. http://dx.doi.org/10.32747/2011.7592121.bard.

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Abstract (sommario):
Original objectives and revisions The original objectives of this research, as stated in the approved proposal were: 1. To establish guidelines for the use of turbulent transport techniques as accurate and reliable tool for continuous measurements of whole canopy ET and other scalar fluxes (e.g. heat and CO2) in large agricultural structures. 2. To conduct a detailed experimental study of flow patterns and turbulence characteristics in agricultural structures. 3. To derive theoretical models of air flow and scalar fluxes in agricultural structures that can guide the interpretation of TT measurements for a wide range of conditions. All the objectives have been successfully addressed within the project. The only modification was that the study focused on screenhouses only, while it was originally planned to study large greenhouses as well. This was decided due to the large amount of field and theoretical work required to meet the objectives within screenhouses. Background In agricultural structures such as screenhouses and greenhouses, evapotranspiration (ET) is currently measured using lysimeters or sap flow gauges. These measurements provide ET estimates at the single-plant scale that must then be extrapolated, often statistically or empirically, to the whole canopy for irrigation scheduling purposes. On the other hand, turbulent transport techniques, like the eddy covariance, have become the standard for measuring whole canopy evapotranspiration in the open, but their applicability to agricultural structures has not yet been established. The subject of this project is the application of turbulent transport techniques to estimate ET for irrigation scheduling within large agricultural structures. Major conclusions and achievements The major conclusions of this project are: (i) the eddy covariance technique is suitable for reliable measurements of scalar fluxes (e.g., evapotranspiration, sensible heat, CO2) in most types of large screenhouses under all climatic conditions tested. All studies resulted with fair energy balance closures; (ii) comparison between measurements and theory show that the model is capable in reliably predicting the turbulent flow characteristics and surface fluxes within screenhouses; (iii) flow characteristics within the screenhouse, like flux-variance similarity and turbulence intensity were valid for the application of the eddy covariance technique in screenhouses of relatively dilute screens used for moderate shading and wind breaking. In more dense screens, usually used for insect exclusions, development of turbulent conditions was marginal; (iv) installation of the sensors requires that the system’s footprint will be within the limits of the screenhouse under study, as is the case in the open. A footprint model available in the literature was found to be reliable in assessing the footprint under screenhouse conditions. Implications, both scientific and agricultural The study established for the first time, both experimentally and theoretically, the use of the eddy covariance technique for flux measurements within agricultural screenhouses. Such measurements, along with reliable theoretical models, will enable more accurate assessments of crop water use which may lead to improved crop water management and increased water use efficiency of screenhouse crops.
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9

Blundell, S. Tutorial : the DEM Breakline and Differencing Analysis Tool—step-by-step workflows and procedures for effective gridded DEM analysis. Engineer Research and Development Center (U.S.), novembre 2022. http://dx.doi.org/10.21079/11681/46085.

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The DEM Breakline and Differencing Analysis Tool is the result of a multi-year research effort in the analysis of digital elevation models (DEMs) and the extraction of features associated with breaklines identified on the DEM by numerical analysis. Developed in the ENVI/IDL image processing application, the tool is designed to serve as an aid to research in the investigation of DEMs by taking advantage of local variation in the height. A set of specific workflow exercises is described as applied to a diverse set of four sample DEMs. These workflows instruct the user in applying the tool to extract and analyze features associated with terrain, vegetative canopy, and built structures. Optimal processing parameter choices, subject to user modification, are provided along with sufficient explanation to train the user in elevation model analysis through the creation of customized output overlays.
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10

Leis, Sherry. Vegetation community monitoring trends in restored tallgrass prairie at Wilson’s Creek National Battlefield: 2008–2020. National Park Service, aprile 2022. http://dx.doi.org/10.36967/nrr-2293117.

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Plant community monitoring at Wilson’s Creek National Battlefield (NB) focused on the restored tallgrass prairie community. Six monitoring sites were visited four times and observations of plant species and ground cover were made. In addition to those observations, we included two environmental factors in this report—precipitation and recent fire history—to help understand the vegetation data status and trends. Precipitation data (standardized vegetation index) indicated drought conditions in 2012 and some dry periods in 2016. Although prairies are adapted to drought, we found that species richness at the site and community scales (alpha and gamma diversity) were reduced in dry years. Fire management also plays an important role in shaping the plant communities. Prescribed fire occurrence became less frequent through the monitoring period. Also, additional treatments, including herbicide and mowing, likely shaped the prairie community. Tree regeneration and nonnative plants in particular may have been affected by these techniques. The prairie plant community continues to be moderately diverse despite recent increases in tree seedlings and small saplings. Species richness varied over time and was correlated with precipitation; diversity indices (H′ and J′) were similar across monitored years. Species guilds (also known as functional groups) demonstrated differing patterns. Woody plants, long a concern at the park, were abundant and statistically similar across years. Many guilds were quite variable across the sites, but nonnative forbs declined, and nonnative grasses increased. Overstory trees and canopy cover, measured for the first time in 2020, have likely influenced the composition of one site. The composition of this site points to a shrubland-savanna community. Four of the sites tended towards shrubland rather than tallgrass prairie. The vegetation monitoring protocol experienced some changes between 2008 and 2020. A key difference was a shift from sampling twice during the field season to sampling only once in a monitoring year. An anticipated decline in species richness was observed in 2012 and 2016, but we were unable to isolate sample design as the cause. Additionally, we remedied inconsistencies in how tree regeneration was recorded by tallying seedlings and saplings in the field. Our quality assurance procedures indicated that our observer error from pseudoturnover was 20.2%, meeting our expectations. Cover class estimates agreed 73% of the time, with all disagreements within one cover class. Coordinating management actions to achieve plant community goals like structure and composition of tallgrass prairie will be critical to the survival of the prairie species at the park. Fire and nonnative plant treatments along with the reduction of woody cover including trees are needed to arrest the transition to savanna and woodland community types. Frequent prescribed fire is an integral process for this community and there is no equivalent substitute. Continued focus on management for the desired tallgrass prairie community will also provide needed habitat for imperiled pollinators such as the monarch butterfly. Best management practices for pollinators on federal lands specify that treatments (prescribed fire, mowing or haying) should not occur during the blooming season or when pollinator breeding, egg, larval or pupal stages are present.
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