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Comparison of estimators of variance for forest inventories with systematic sampling-results from artificial populations

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Forest Ecosystems 2020年第2期7卷 215-233页

作者： Steen Magnussen Ronald EMcRoberts Johannes Breidenbach Thomas Nord-Larsen Göran Ståhl lutz fehrmann Sebastian Schnell 506 West Burnside Road VictoriaBC V8Z 1M5Canada Raspberry Ridge Analytics 15111 Elmcrest Avenue NorthHugoMN 55038USA Norwegian Institute of Bioeconomy Research Høgskolevegen 81431ÅsNorway Department of Geosciences and Natural Resource Management University of CopenhagenRolighedsvej 23DK-1958 Frederiksberg CDenmark Department of Forest Resource Management Swedish University of Agricultural SciencesUmeåSweden Forest Inventory and Remote Sensing Faculty of Forest SciencesUniversity of GöttingenBüsgenweg 5D37077GöttingenGermany Alfred-Möller-Straße 1 Haus 41-4216225 EberswaldeGermany.

Background:Large area forest inventories often use regular grids(with a single random start)of sample locations to ensure a uniform sampling intensity across the space of the surveyed populations.A design-unbiased estimator of variance does not exist for this ***,a quasi-default estimator applicable to simple random sampling(SRS)is used,even if it carries with it the likely risk of overestimating the variance by a practically important *** better exploit the precision of systematic sampling we assess the performance of five estimators of variance,including the quasi *** this study,simulated systematic sampling was applied to artificial populations with contrasting covariance structures and with or without linear *** compared the results obtained with the SRS,Matern’s,successive difference replication,Ripley’s,and D’Orazio’s variance ***:The variances obtained with the four alternatives to the SRS estimator of variance were strongly correlated,and in all study settings consistently closer to the target design variance than the estimator for *** latter always produced the greatest *** populations with a near zero spatial autocorrelation,all estimators,performed equally,and delivered estimates close to the actual design ***:Without a linear trend,the SDR and DOR estimators were best with variance estimates more narrowly distributed around the benchmark;yet in terms of the least average absolute deviation,Matern’s estimator held a narrow *** a strong or moderate linear trend,Matern’s estimator is *** large populations,and a low sampling intensity,the performance of the investigated estimators becomes more similar.

关键词： Spatial autocorrelation Linear trend Model based Design biased Matern variance Successive difference replication variance Geary contiguity coefficient Random site effects

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Improving precision of field inventory estimation of aboveground biomass through an alternative view on plot biomass

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Forest Ecosystems 2020年第4期7卷 760-769页

作者： Christoph Kleinn Steen Magnussen Nils Nölke Paul Magdon Juan GabrielÁlvarez-González lutz fehrmann César Pérez-Cruzado Forest Inventory and Remote Sensing Georg-August-Universität Göttingen37077 GöttingenGermany. Canadian Forest Service Natural Resources CanadaVictoriaBC V8Z 1M5Canada. Department of Agroforestry Engineering University of Santiago de CompostelaE-27002 LugoSpain

We contrast a new continuous approach(CA)for estimating plot-level above-ground biomass(AGB)in forest inventories with the current approach of estimating AGB exclusively from the tree-level AGB predicted for each tree in a plot,henceforth called DA(discrete approach).With the CA,the AGB in a forest is modelled as a continuous surface and the AGB estimate for a fixed-area plot is computed as the integral of the AGB surface taken over the plot *** with the CA,the portion of the biomass of in-plot trees that extends across the plot perimeter is ignored while the biomass from trees outside of the plot reaching inside the plot is *** use a sampling simulation with data from a fully mapped two hectare area to illustrate that important differences in plot-level AGB estimates can *** CA-based estimates of mean AGB should be less variable than those derived from the *** realized,this difference translates to a higher precision from field sampling,or a lower required sample *** our case study with a target precision of 5%(*** standard error of the estimated mean AGB),the CA required a 27.1%lower sample size for small plots of 100 m2 and a 10.4%lower sample size for larger plots of 1700 *** examined sampling induced errors only and did not yet consider model *** discuss practical issues in implementing the CA in field inventories and the potential in applications that model biomass with remote sensing *** CA is a variation on a plot design for above-ground forest biomass;as such it can be applied in combination with any forest inventory sampling design.

关键词： Branch biomass Foliage biomass Stem biomass Biomass surface plots Sampling surfaces Standard error of estimation

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Effect of Processing and Cultivar on Thermo-Chemical Properties of Australian-Grown Hemp Hurd(Cannabis sativa L.)

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Journal of Renewable Materials 2024年第8期12卷 1475-1493页

作者： Johannes fehrmann Benoit Belleville Barbara Ozarska Maya Ismayati Wahyu Dwianto School of Agriculture Food and Ecosystem Sciences(SAFES)Faculty of ScienceThe University of MelbourneMelbourne3121Australia Research Center for Biomass and Bioproducts National Research and Innovation Agency(BRIN)Jakarta16911Indonesia

This study explored the thermo-chemical properties of industrial hemp hurd with different provenances,maturity stages,and retting *** findings were then compared to hemp hurd used in the fabrication of citric acid-bonded ultra-low-density hemp hurd ***-gas chromatography-mass spectrometry(Py-GC/MS),Fourier-transform infrared spectroscopy(FTIR),and thermogravimetric analysis(TGA)were employed to document the variability of the hurd and comprehend the potential impact on biobased composite *** choice of cultivar,maturity stage,and processing modality significantly influenced the chemical composition,presence of functional groups,and thermal stability of the ***-GC/MS revealed substantial variations in the lignin-to-carbohydrate(L/C)ratio,along with the absence of fatty acids in certain *** FTIR signals confirmed consistent functional groups,differences in peak intensities were indicative of carbohydrate variations associated with maturity and retting duration,impacting the availability of hydroxyl groups for,i.e.,interparticle bonding in citric acid-based ***,it was observed that shorter retting durations initially enhanced the thermal resistance,but prolonged retting led to accelerated degradation,significantly reducing the hurd’s residual *** findings indicated notable differences among the samples,emphasizing the importance of investigating variables such as provenance/cultivar,maturity,and processing *** assessment is essential to ensure effective agronomic practices that align the raw material characteristics with the specific requirements of intended applications,such as the fabrication of biobased hemp hurd composites.

关键词： Hemp hurd material characterization chemical analysis thermal analysis

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CO_2 Capture technologies: Current status and new directions using supported ionic liquid phase (SILP) absorbers

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Science China Chemistry 2012年第8期55卷 1648-1656页

作者： KOLDING Helene fehrmann Rasmus RIISAGER Anders Centre for Catalysis and Sustainable Chemistry Department of Chemistry Building 207 Technical University of Denmark2800 Kgs. Lyngby Denmark

Current state-of-the-art techniques for COz capture are presented and discussed, Post-combustion capture of CO2 by absorption is the technology most easily retrofitted to existing installations, but at present this is not economically viable to install and run. Using ionic liquids instead of aqueous amine solutions overcomes the major thermodynamic issues. By applying SILP tech- nology further advances, in terms of ease of handling and sorption dynamics, are obtained. Initial experimental studies showed that ionic liquids such as tetrahexylammonium prolinate, [N6666][Pro], provide a good candidate for CO2 absorption using SILP technology. Thus a solid SILP absorber comprised of 40 wt% [N6666][Pro] loaded on precalcined silica quantitatively takes up about 1.2 mole CO2 per mole of ionic liquid in consecutive absorption-desorption cycles in a flow-experiment per- formed with 0.09 bar of CO2 （9% CO2 in He）.

关键词： CO2 capture absorption ionic liquids SILP absorber

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