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Abstract: The monitoring of seasonal radial growth of woody plants addresses the ultimate question of when, how and why trees grow. Assessing the growth dynamics is important to quantify the effect of environmental drivers and understand how woody species will deal with the ongoing climatic changes. One of the crucial steps in the analyses of seasonal radial growth is to model the dynamics of xylem and phloem formation based on increment measurements on samples taken at relatively short intervals during the growing season. The most common approach is the use of the Gompertz equation, while other approaches, such as general additive models (GAMs) and generalised linear models (GLMs), have also been tested in recent years. For the first time, we explored artificial neural networks with Bayesian regularisation algorithm (BRNNs) and show that this method is easy to use, resistant to overfitting, tends to yield s-shaped curves and is therefore suitable for deriving temporal dynamics of secondary tree growth. We propose two data processing algorithms that allow more flexible fits. The main result of our work is the XPSgrowth() function implemented in the radial Tree Growth (rTG) R package, that can be used to evaluate and compare three modelling approaches: BRNN, GAM and the Gompertz function. The newly developed function, tested on intra-seasonal xylem and phloem formation data, has potential applications in many ecological and environmental disciplines where growth is expressed as a function of time. Different approaches were evaluated in terms of prediction error, while fitted curves were visually compared to derive their main characteristics. Our results suggest that there is no single best fitting method, therefore we recommend testing different fitting methods and selection of the optimal one.
Keywords: artificial neural networks, cambium, generalized additive model, Gompertz function, growing season, intra-annual time series
Published in DiRROS: 21.07.2022; Views: 512; Downloads: 337
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Abstract: Tree heights are one of the most important aspects of forest mensuration, but data are often unavailable due to costly and time-consuming field measurements. Therefore, various types of models have been developed for the imputation of tree heights for unmeasured trees, with mixed-effects models being one of the most commonly applied approaches. The disadvantage here is the need of sufficient sample size per tree species for each plot, which is often not met, especially in mixed forests. To avoid this limitation, we used principal component analysis (PCA) for the grouping of similar plots based on the most relevant site descriptors. Next, we compared mixed-effects models with height-diameter models based on artificial neural networks (ANN). In terms of root mean square error (RMSE), mixed-effects models provided the most accurate tree height predictions at the plot level, especially for tree species with a smaller number of tree height measurements. When plots were grouped using the PCA and the number of observations per category increased, ANN predictions improved and became more accurate than those provided by mixed-effects models. The performance of ANN also increased when the competition index was included as an additional explanatory variable. Our results show that in the pursuit of the most accurate modelling approach for tree height predictions, ANN should be seriously considered, especially when the number of tree measurements and their distribution is sufficient.
Keywords: height-diameter models, national forest inventory, permanent sample plot, mixed forests, model comparison, principal component analysis
Published in DiRROS: 08.06.2022; Views: 542; Downloads: 227
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Keywords: rak debelega črevesa, rak danke, bolniki, zdravljenje
Published in DiRROS: 18.03.2022; Views: 831; Downloads: 451
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Abstract: Ozemlje med vasmi Reka v dolini Idrijce, Bukovo pod Kojco in Zakriž pri Cerknem pripada v geografskem in geotektonskem pogledu Dinaridom. Gradijo ga kamnine dveh obsežnih narivnih enot Trnovskega pokrova, ki so bile za več deset kilometrov narinjene od severovzhoda proti jugozahodu v današnjo lego. Preko njih so narinjene kamnine Tolminskega pokrova, ki je na obravnavanem ozemlju najnižja narivna enota Južnih Alp. Pokrov sestavljajo dve notranji narivni grudi in vmesna narivna luska. Narivne enote so bile narinjene od severa proti jugu. V zahodnem delu obravnavanega območja stik med Južnimi Alpami in Dinaridi poteka ob Sovodenjskem prelomu.Kljub temu, da so kamnine v obravnavanih narivnih enotah približno enake starosti, lahko prepoznamo dva različna stratigrafska razvoja. Posebej izstopa problematika razvoja ladinijsko-spodnjekarnijskih psevdoziljskih plasti, to je zaporedja klastičnih in karbonatnih kamnin, ki se je odložilo v globljemorskem okolju Slovenskega bazena. Tako v Trnovskem kot tudi v Tolminskem pokrovu najdemo psevdoziljske plasti razvite v podobnem, litološko značilnem zaporedju, a so v Tolminskem pokrovu razvite v precej večji debelini kot v Trnovskem pokrovu in navzgor zvezno prehajajo v amfiklinske plasti, medtem ko je debelina psevdoziljskih plasti v Trnovskem pokrovu precej manjša, v normalnem zaporedju pa na njih leži platformni cordevolski dolomit.
Keywords: narivna zgradba, Trnovski pokrov, Tolminski pokrov, Južne Alpe, Dinaridi, Slovenski bazen, trias, psevdoziljske plasti
Published in DiRROS: 09.03.2022; Views: 940; Downloads: 369
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Keywords: adenokarcinom želodca, priporočila, prebavni trakt, multidisciplinarno zdravljenje
Published in DiRROS: 16.12.2021; Views: 1163; Downloads: 516
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