Models of individual tree mortality for trembling aspen, lodgepole pine, hybrid spruce and subalpine fir in northwestern British Columbia
Density dependent mortality is an important process in forest succession. The overall predictive abilities of forest simulation models are closely related to their ability to predict mortality. Finding appropriate methods for modelling mortality have often proved to be a difficult challenge. The obj...
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| Formato: | Otro |
| Lenguaje: | sueco Inglés |
| Publicado: |
2007
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| Acceso en línea: | https://stud.epsilon.slu.se/11963/ |
| _version_ | 1855571974016729088 |
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| author | Möller Pedersen, Sören |
| author_browse | Möller Pedersen, Sören |
| author_facet | Möller Pedersen, Sören |
| author_sort | Möller Pedersen, Sören |
| collection | Epsilon Archive for Student Projects |
| description | Density dependent mortality is an important process in forest succession. The overall predictive abilities of forest simulation models are closely related to their ability to predict mortality. Finding appropriate methods for modelling mortality have often proved to be a difficult challenge. The objective of this study was to test a method on adult trees, which was previously used for modelling density dependent mortality for saplings with good results. In the basic model mortality is predicted as a function of recent diameter growth. It was also tested if incorporating tree size into the mortality model improved it.
Models were developed for four species: trembling aspen (Populus tremuloides Michx.), lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia), hybrid spruce (a complex of white spruce (Picea glauca (Moench) Voss) and Engelmann spruce (Picea engelmanii Parry ex Engelm.)) and subalpine fir (Abies lasiocarpa (Hook.) Nutt.). The models were parameterized from field data using a maximum-likelihood method. Field data was gathered from 16 stands in the Sub-Boreal Spruce Zone in northwestern British Columbia and comprised of 337 live and 345 recently dead trees in total. The mortality models were tested by incorporating them into the individual tree, spatially explicit forest simulation model SORTIE-ND. SORTIE-ND simulations of single species even-aged stands were compared to simulations of a commonly used stand level simulation model. Furthermore, SORTIE-ND simulations of permanent sample plots in mixed species uneven-aged stands were compared to remeasurements of the plots.
It was determined that incorporating tree size into the mortality models gave better fits to the field data. Tolerance to low growth decreases to a minimum at intermediate trees size for all species except for subalpine fir, where it decreases and remains low as trees growth larger. This is probably an effect of the ontogenetic characteristics of the individual species.
Testing the mortality models in SORTIE-ND showed that they contribute to realistic thinning patterns in simulations of both pure even-aged stands and complex stands. However, it was evident that the performance of the mortality models is highly dependent on the underlying growth models as well as mortality models accounting for random mortality. Discrepancies in modelling results were linked to over- and underestimation of growth or inappropriate random mortality rates.
Overall the tested method provides a straight forwards approach to parameterizing growth based mortality models from field data which is relatively easy to obtain. |
| format | Otro |
| id | RepoSLU11963 |
| institution | Swedish University of Agricultural Sciences |
| language | Swedish Inglés |
| publishDate | 2007 |
| publishDateSort | 2007 |
| record_format | eprints |
| spelling | RepoSLU119632017-11-15T10:09:52Z https://stud.epsilon.slu.se/11963/ Models of individual tree mortality for trembling aspen, lodgepole pine, hybrid spruce and subalpine fir in northwestern British Columbia Möller Pedersen, Sören Forestry - General aspects Density dependent mortality is an important process in forest succession. The overall predictive abilities of forest simulation models are closely related to their ability to predict mortality. Finding appropriate methods for modelling mortality have often proved to be a difficult challenge. The objective of this study was to test a method on adult trees, which was previously used for modelling density dependent mortality for saplings with good results. In the basic model mortality is predicted as a function of recent diameter growth. It was also tested if incorporating tree size into the mortality model improved it. Models were developed for four species: trembling aspen (Populus tremuloides Michx.), lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia), hybrid spruce (a complex of white spruce (Picea glauca (Moench) Voss) and Engelmann spruce (Picea engelmanii Parry ex Engelm.)) and subalpine fir (Abies lasiocarpa (Hook.) Nutt.). The models were parameterized from field data using a maximum-likelihood method. Field data was gathered from 16 stands in the Sub-Boreal Spruce Zone in northwestern British Columbia and comprised of 337 live and 345 recently dead trees in total. The mortality models were tested by incorporating them into the individual tree, spatially explicit forest simulation model SORTIE-ND. SORTIE-ND simulations of single species even-aged stands were compared to simulations of a commonly used stand level simulation model. Furthermore, SORTIE-ND simulations of permanent sample plots in mixed species uneven-aged stands were compared to remeasurements of the plots. It was determined that incorporating tree size into the mortality models gave better fits to the field data. Tolerance to low growth decreases to a minimum at intermediate trees size for all species except for subalpine fir, where it decreases and remains low as trees growth larger. This is probably an effect of the ontogenetic characteristics of the individual species. Testing the mortality models in SORTIE-ND showed that they contribute to realistic thinning patterns in simulations of both pure even-aged stands and complex stands. However, it was evident that the performance of the mortality models is highly dependent on the underlying growth models as well as mortality models accounting for random mortality. Discrepancies in modelling results were linked to over- and underestimation of growth or inappropriate random mortality rates. Overall the tested method provides a straight forwards approach to parameterizing growth based mortality models from field data which is relatively easy to obtain. Naturlig avgång på grund av trängsel är en viktig process för den skogliga successionen. Generellt är förmågan hos modeller för skogssimulering att göra exakta prognoser nära relaterad till hur väl de hanterar självgallring. Att hitta en lämplig metod för att modellera självgallring har ofta visat sig vara en svår utmaning. Syftet med detta examensarbete var att testa en metod på vuxna träd (DBH > 5cm) som tidigare har använts för att modellera självgallring hos plantor med gott resultat. Basmodellen skattar sannolikheten för att ett enskilt träd ska dö på grund av självgallring som en funktion av de senaste årens diametertillväxt. Dessutom testades om självgallringsmodellerna potentiellt förbättrades genom att inkludera trädstorleken som oberoende variabel. Det utvecklades självgallringsmodeller för fyra olika trädslag: asp (Populus tremuloides Michx.), contortatall (Pinus contorta Dougl. ex Loud. var. latifolia), hybridgran (hybrider mellan vitgran (Picea glauca (Moench) Voss) och Engelmann-gran (Picea engelmanii Parry ex Engelm.)) och klippgran (Abies lasiocarpa (Hook.) Nutt.). Modellernas parametrar skattades med en maximum-likelihood metod från fältdata. Data insamlades i 16 bestånd i den sub-boreala gran zon i nordvästra British Columbia och består av totalt 337 levande och 345 nyligen döda träd. Självgallringsmodellerna testades i SORTIE-ND, en trädvis och avståndsberoende skogsproduktionsmodell. SORTIE-ND simuleringar av rena likåldriga bestånd jämfördes med simuleringar gjorda med en ofta använd beståndsbaserad skogsproduktionsmodell. Dessutom jämfördes SORTIE-ND simuleringar för permanenta provytor i olikåldriga blandbestånd med uppmätt utveckling på dessa provytor. Genom att inkludera individuell trädstorlek i basmodellen uppnåddes bättre anpassning till fältdata. Avgångsrisken vid låg tillväxt var minst för medelstora träd för alla trädslag förutom klippgran. För detta trädslag minskar avgångsrisken vid låg tillväxt kontinuerligt med ökad trädstorlek. Detta är en konsekvens av de enskilda trädslagens karakteristika. Självgallringsmodellerna bidrog till realistisk avgång i båda likåldriga och komplexa bestånd. Det är dock uppenbart att självgallringsmodellerna är väldigt beroende av de underliggande tillväxtmodellerna och modeller som uppskattar den stokastiska avgången i ett bestånd. Modellernas avvikelser är relaterade till över- eller underskattning av tillväxten och orealistiska nivåer på den stokastiska avgången. Den testade metoden är ett relativt enkelt sätt att härleda och estimera parametra till en tillväxtbaserad självgallringsmodell från fältdata. Dessutom är data relativt enkla att erhålla. 2007-02-28 Other NonPeerReviewed application/pdf sv https://stud.epsilon.slu.se/11963/1/pedersen_s_171115.pdf Möller Pedersen, Sören, 2007. Models of individual tree mortality for trembling aspen, lodgepole pine, hybrid spruce and subalpine fir in northwestern British Columbia. UNSPECIFIED, Umeå. Umeå: (S) > Dept. of Forest Ecology and Management <https://stud.epsilon.slu.se/view/divisions/OID-241.html> urn:nbn:se:slu:epsilon-s-8815 eng |
| spellingShingle | Forestry - General aspects Möller Pedersen, Sören Models of individual tree mortality for trembling aspen, lodgepole pine, hybrid spruce and subalpine fir in northwestern British Columbia |
| title | Models of individual tree mortality for trembling aspen, lodgepole pine, hybrid spruce and subalpine fir in northwestern British Columbia |
| title_full | Models of individual tree mortality for trembling aspen, lodgepole pine, hybrid spruce and subalpine fir in northwestern British Columbia |
| title_fullStr | Models of individual tree mortality for trembling aspen, lodgepole pine, hybrid spruce and subalpine fir in northwestern British Columbia |
| title_full_unstemmed | Models of individual tree mortality for trembling aspen, lodgepole pine, hybrid spruce and subalpine fir in northwestern British Columbia |
| title_short | Models of individual tree mortality for trembling aspen, lodgepole pine, hybrid spruce and subalpine fir in northwestern British Columbia |
| title_sort | models of individual tree mortality for trembling aspen, lodgepole pine, hybrid spruce and subalpine fir in northwestern british columbia |
| topic | Forestry - General aspects |
| url | https://stud.epsilon.slu.se/11963/ https://stud.epsilon.slu.se/11963/ |