Giorgio Vacchiano
I'm currently a post-doc researcher at the Department of Agiculture, Silviculture and Land Managment, University of Turin (Italy). My research stems from forest ecology issues, and focuses on modeling forest dynamics as a tool to better understand the functioning of forest ecosystem. Models of forest and landscape dynamics can help untangling the driving factors of change in natural systems (i.e., endogenous, exogenous or anthropogenic) and represent a basis for the design of sustainable management alternatives.
During the last four years (2004-2008) I focused on Alpine forest communities. The abandonment of rural areas that has been taking place since World War II determined an increase of open areas available to forest encroachment In the meantime, climate-induced succession is likely to shift the equilibrium of dry, low-elevation communities towards a greater contribution of sub-mediterranean species, while pushing further up in elevation the optimality area for mountain and subalpine forest species. Such changes effect stand, community and landscape processes, raising concerns for the stability and continuity of the services provided by the forest.
Thanks to a long-term forest monitoring task I had the chance to test research methodologies aimed at analyzing the dynamics of a forest system in transition, with a special focus on competitive interactions. I earned some experience in quantitative data analysis, inferential statistics (a Lab I’ve been teaching in since 2005 at University of Turin) and growth modeling, acquiring a hands-on approach while at Utah State University as a visiting student in 2005-06.
My current research activity involves the follow-up to my past interest in competition and dieback-related processes, at the individual scale (climate-growth relationships), at the stand scale (mortality as influenced by exogenous factors) and at the landscape level (successional trajectories and drivers), and using both biological and documental archives (dendrochronology, forest inventory, remote sensing).
I am moved in my research by the hope of giving my contribution towards a greater understanding of the meaning of “sustainability” in the relationship between man and forest resources, in the framework of the current scenarios of change. I believe that the quantitative analysis and modeling of the dynamic factors influencing forest composition and structure could help understanding the functioning of ecosystem and suggest timely adaptations for management strategies.
Supervisors: Renzo Motta
Phone: +39 011 670 5536
Address: Largo Braccini 2, Grugliasco (TO) 10095 Italy
During the last four years (2004-2008) I focused on Alpine forest communities. The abandonment of rural areas that has been taking place since World War II determined an increase of open areas available to forest encroachment In the meantime, climate-induced succession is likely to shift the equilibrium of dry, low-elevation communities towards a greater contribution of sub-mediterranean species, while pushing further up in elevation the optimality area for mountain and subalpine forest species. Such changes effect stand, community and landscape processes, raising concerns for the stability and continuity of the services provided by the forest.
Thanks to a long-term forest monitoring task I had the chance to test research methodologies aimed at analyzing the dynamics of a forest system in transition, with a special focus on competitive interactions. I earned some experience in quantitative data analysis, inferential statistics (a Lab I’ve been teaching in since 2005 at University of Turin) and growth modeling, acquiring a hands-on approach while at Utah State University as a visiting student in 2005-06.
My current research activity involves the follow-up to my past interest in competition and dieback-related processes, at the individual scale (climate-growth relationships), at the stand scale (mortality as influenced by exogenous factors) and at the landscape level (successional trajectories and drivers), and using both biological and documental archives (dendrochronology, forest inventory, remote sensing).
I am moved in my research by the hope of giving my contribution towards a greater understanding of the meaning of “sustainability” in the relationship between man and forest resources, in the framework of the current scenarios of change. I believe that the quantitative analysis and modeling of the dynamic factors influencing forest composition and structure could help understanding the functioning of ecosystem and suggest timely adaptations for management strategies.
Supervisors: Renzo Motta
Phone: +39 011 670 5536
Address: Largo Braccini 2, Grugliasco (TO) 10095 Italy
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A general conceptual model for complex, stress-induced forest decline was applied. The multiple stress factors were characterized according to their occurrence and impact as predisposing, inciting and contributing factors. Most of theses investigated factors are directly linked with increasing temperatures and subsequent drought, as reported for the past decades and forecasted for the near future. Based on this system analysis, management options were defined to guarantee the current forest goods and services for the future.
Current stand structure in the Alpine regions has been shaped by anthropogenic influence for the last centuries, This is especially true for pine forests, that show greater sensitivity to land use and environmental changes due to their vast distribution and their early-seral character. Besides the ongoing and ubiquitous land abandonment pattern, a novel phenomenon has appeared in the last decades, namely a dieback wave which is undermining the continuity of the services supplied by the pine forests.
For this reasons, sustainable forest management of pine stands must be the subject of scrupulous consideration. The peculiar climatic and site conditions in the Alps and the close interaction between forest dynamics and human activities suggest the need for a more thorough understanding of ongoing processes. A deeper knowledge may represent the basis for designing prediction models of stand structure and dynamics to support silvicultural management.
We identified competition as the main process driving tree and stand development. The present research focuses on the analysis of competitive and mortality dynamics on different spatial and temporal extents (from tree to stand and district). The aims of the present work are: (a) to describe current distribution of Scots pine in the Southwestern Alps, with a special focus on region-wide changes in land use and climate regimes and their potential effect; (b) to design a silvicultural decision support tool, capable of predicting stand development on a regional scale and comparing management alternatives for the pursuit of the desired silvicultural goals; (c) to analyze the mode of intra- and interspecific competition in Scots pine stands and to assess its effects on both individual growth and on tree survival as an emergent property, also including interactions with land use history; (d) to test the applicability of an individual-based growth and yield model to local species and growing conditions, foreseeing its implementation for the analyzed stands.
The methods of this research are aimed at the reconstruction of past stand history, at the understanding of present dynamics and at modeling future stand structure and composition. For this reason we integrated available forest inventory data with dendroecological measurements from a new permanent network of sample plots, located in the main pine cover types of the study area. The development of the research is based on a gradual refinement of the scale of investigation, ranging from historical landscape analysis to region-wide fitted biometric relationships, to local competition analysis by means of numerical indices and geostatistical techniques, to the modelling of individual tree growth and mortality.
Our results show that Scots pine is characterized by a rapid response to environmental and land use change. The species has a great potential for colonization, and can originate a massive and homogeneous establishment where climate is not limiting and land abandonment was more pronounced. Most of the younger stands show quick and well-defined dynamics, driven by competition for light in the earlier self-thinning stage and by structural differentiation in the reinitiation phase or leading to succession of late-seral species in mature stands. On the other hand, where site fertility is limiting and disturbances play a negative impact on pine growth and survival, dynamics are slower. Here, competition may be locally intense but is not the main population regulatory factor. In all cases, land use history has been shown as having a strong influence on ongoing competitive dynamics and their consequences at the stand level, i.e., the survival-mortality equilibrium.
In the last chapter a calibration and sensitivity test of US Forest Service’s individual-base growth model, the Forest Vegetation Simulator, is shown. FVS was validated on local inventory data for the Fort Bragg NC forest area, characterized by a vast extension of Longleaf pine (Pinus palustris Mill) constituting the main habitat for the endangered red-cockaded woodpecker (Picoides borealis). Available growth projections are hampered by a general overprediction of density and yield, as compared to both field-based evidence and the biological constraints of the species. Successful calibration of the many growth submodels of FVS, carried out based on more than 140,000 tree measurements (11,000 sample plots, years 2002-2003 inventory), enabled managers to rely on more accurate growth predictions. Flexibility to user’s input is among the desired features of a species-wide prediction model for Scots pine dynamics. De-construction, calibration and testing of an existing forest growth and yield model over localized inventory data provided the basis to propose data and research needs for implementing such framework in Alpine forests.
Last, the design and implementation of a Density Management Diagram proved useful to project, visualize and compare silvicultural goals and management strategies aimed at their pursuit. The diagram is based upon the self-thinning law. It was designed using region-wide forest inventory data, and field-based data from permanent plots as a control and validation dataset. By characterizing silvicultural goals in terms of quantitative stand parameters, we devised different scenarios according to the functions whose supply is demanded to the pine forest, and effectively compared the trajectories of stand development associated to alternative management strategies. We also tested implementation on the diagram of natural disturbance regimes, which we reconstructed from historical and field evidence, in order to forecast the most likely stand response.
The combined analysis of different spatio-temporal scales, i.e., region-wide forest inventories and intensive plot measurements, allowed us to model inferred dynamics across a wide range of organization levels in the community, from trees to whole landscapes. The establishment of a permanent monitoring network will prove its utility with upcoming repeated measurements. The natural prosecution of this study will be the design of a inventory network suitable for constructing a local variant of the described model, and the statistical implementation of such tool in mountain forests of the Alps over a wider range of key species.
Lo Stand density index di Reineke (1933) esprime la relazione negativa tra il numero di piante per unità di superficie e il diametro medio in popolamenti coetanei non disturbati, definendo una base scientifica per valutare la competizione e lo stress nei popolamenti forestali. Il contributo delle singole componenti del popolamento allo Stand density index totale è additivo, cosicché questo indice è applicabile a strutture sia coetanee che disetanee e irregolari. Vengono presentati i diversi contributi che la ricerca ha apportato alla definizione di questa misura di densità; nella realtà italiana si propone di dare un particolare risalto alle applicazioni ecologiche dello Stand density index, che può essere utilizzato per valutare gli habitat di diverse specie animali o la stabilità biologica e strutturale dei popolamenti.
L’obiettivo della ricerca è introdurre i concetti propri dello Stand density index nella selvicoltura italiana, applicando i metodi per la sua valutazione a popolamenti di abete bianco (Abies alba Mill.) in provincia di Cuneo. Si sono utilizzati allo scopo i dati rilevati in occasione della redazione dei Piani forestali territoriali della Regione Piemonte, che hanno così potuto trovare un’adeguata valorizzazione; i dati provengono da 186 aree di saggio, dislocate nella fascia montana e subalpina della provincia.
Un modello di autodiradamento lineare, caratterizzato da semplicità di elaborazione e da un buon adattamento ai dati del campione, è stato ritenuto adeguato ad una ricerca di carattere esplorativo. Si è valutato lo Stand density index massimo che i popolamenti di abete bianco possono assumere, sia con il metodo tradizionale che con quello additivo; quest’ultimo, più consono alla particolare struttura dei boschi in esame, ha prodotto valori di Stand density index minori. Per elaborare la relazione completa tra diametro medio e densità per i popolamenti osservati sono state scelte solo le aree in cui l’abete bianco rappresentava almeno l’80% dell’area basimetrica. Applicando al nuovo campione, composto di 77 aree di saggio, un modello di regressione lineare, la pendenza della linea limitante dimensione-densità per l’abete bianco è risultata essere -1,491, un valore minore ma non significativamente differente da quello originariamente indicata da Reineke per diverse specie (-1,605). Si propone di calcolare lo Stand density index dei singoli popolamenti assumendo come esponente il valore individuato, e di utilizzare la formulazione additiva che è la più generalmente applicabile. Seguendo tali indicazioni, si è individuato quale Stand density index massimo per l’abete bianco il valore di 1359 in unità di misura metriche decimali. Tale valore è stato messo a confronto con quelli indicati in letteratura per la stessa specie e per specie ecologicamente simili.
I popolamenti esaminati nel loro complesso mostrano Stand density index variabili dal 6% al 162% rispetto al massimo; tuttavia, il 50% dei popolamenti ha uno Stand density index compreso tra il 35% e il 60%, ed il 74% del campione mostra uno Stand density index variabile dal 25% al 60% del valore massimo. In base ai risultati è possibile affermare che la maggior parte delle abetine esaminate si trovano ad uno stadio di sviluppo inferiore al massimo teorico di sfruttamento delle risorse e di competizione per questa specie.
Lo Stand density index fornisce un valido modello delle dinamiche strutturali nei popolamenti di abete bianco; costituisce pertanto un efficace parametro descrittivo di carattere selvicolturale ed ecologico dei popolamenti forestali, e rappresenta un’utile base per elaborare previsioni di sviluppo dei popolamenti e confrontarle con gli obiettivi gestionali desiderati. La possibilità di seguire nel tempo lo sviluppo dei popolamenti potrebbe rivelarsi uno strumento prezioso per l’applicazione di modelli di sviluppo più dettagliati ed affidabili; ulteriori ricerche, effettuate su un campione rappresentativo di una realtà territoriale più estesa, potranno confermare le tendenze individuate.
rarely been discussed. We analyzed the abundance of Scots pine regeneration in a 257 ha wildfire in an inneralpine forest. Our aims were (1) to model fire intensity at the soil surface and topsoil heating along a gradient of increasing fire severities; (2) to assess the differences in soil properties along the fire severity gradient; (3) to model the effect of disturbance and soil legacies on the density of pine seedlings.We reconstructed fire behavior
and soil heating with the First Order Fire Effects Model (FOFEM), tested the effect of fire severity on soils by nonparametric distributional tests, and modeled seedling density as a function of site, disturbance and soil legacies by fitting a GLM following a variable selection procedure. Topsoil heating differed markedly between the moderate and high severity fires, reaching temperatures high enough to strongly and permanently alter soil
properties only in the latter. High fire severity resulted in decreased soil consistency and wet aggregate stability.
Burned soils had lower organic matter and cations than those unburned. Pine seedlings favored low-fertility, eroded, and chemically poor sites. Establishment was facilitated by the presence of coarse woody debris, but hampered by increasing distance from the seed source. These results suggest that in dry, inner-alpine valleys, fire residuals and soil legacies interact in determining the success of Scots pine re-establishment. High severity fire can promote favorable soil conditions, but distance from the seed source and high evaporation rates of bare soils must be mitigated in order to ensure a successful restoration.
A general conceptual model for complex, stress-induced forest decline was applied. The multiple stress factors were characterized according to their occurrence and impact as predisposing, inciting and contributing factors. Most of theses investigated factors are directly linked with increasing temperatures and subsequent drought, as reported for the past decades and forecasted for the near future. Based on this system analysis, management options were defined to guarantee the current forest goods and services for the future.
Current stand structure in the Alpine regions has been shaped by anthropogenic influence for the last centuries, This is especially true for pine forests, that show greater sensitivity to land use and environmental changes due to their vast distribution and their early-seral character. Besides the ongoing and ubiquitous land abandonment pattern, a novel phenomenon has appeared in the last decades, namely a dieback wave which is undermining the continuity of the services supplied by the pine forests.
For this reasons, sustainable forest management of pine stands must be the subject of scrupulous consideration. The peculiar climatic and site conditions in the Alps and the close interaction between forest dynamics and human activities suggest the need for a more thorough understanding of ongoing processes. A deeper knowledge may represent the basis for designing prediction models of stand structure and dynamics to support silvicultural management.
We identified competition as the main process driving tree and stand development. The present research focuses on the analysis of competitive and mortality dynamics on different spatial and temporal extents (from tree to stand and district). The aims of the present work are: (a) to describe current distribution of Scots pine in the Southwestern Alps, with a special focus on region-wide changes in land use and climate regimes and their potential effect; (b) to design a silvicultural decision support tool, capable of predicting stand development on a regional scale and comparing management alternatives for the pursuit of the desired silvicultural goals; (c) to analyze the mode of intra- and interspecific competition in Scots pine stands and to assess its effects on both individual growth and on tree survival as an emergent property, also including interactions with land use history; (d) to test the applicability of an individual-based growth and yield model to local species and growing conditions, foreseeing its implementation for the analyzed stands.
The methods of this research are aimed at the reconstruction of past stand history, at the understanding of present dynamics and at modeling future stand structure and composition. For this reason we integrated available forest inventory data with dendroecological measurements from a new permanent network of sample plots, located in the main pine cover types of the study area. The development of the research is based on a gradual refinement of the scale of investigation, ranging from historical landscape analysis to region-wide fitted biometric relationships, to local competition analysis by means of numerical indices and geostatistical techniques, to the modelling of individual tree growth and mortality.
Our results show that Scots pine is characterized by a rapid response to environmental and land use change. The species has a great potential for colonization, and can originate a massive and homogeneous establishment where climate is not limiting and land abandonment was more pronounced. Most of the younger stands show quick and well-defined dynamics, driven by competition for light in the earlier self-thinning stage and by structural differentiation in the reinitiation phase or leading to succession of late-seral species in mature stands. On the other hand, where site fertility is limiting and disturbances play a negative impact on pine growth and survival, dynamics are slower. Here, competition may be locally intense but is not the main population regulatory factor. In all cases, land use history has been shown as having a strong influence on ongoing competitive dynamics and their consequences at the stand level, i.e., the survival-mortality equilibrium.
In the last chapter a calibration and sensitivity test of US Forest Service’s individual-base growth model, the Forest Vegetation Simulator, is shown. FVS was validated on local inventory data for the Fort Bragg NC forest area, characterized by a vast extension of Longleaf pine (Pinus palustris Mill) constituting the main habitat for the endangered red-cockaded woodpecker (Picoides borealis). Available growth projections are hampered by a general overprediction of density and yield, as compared to both field-based evidence and the biological constraints of the species. Successful calibration of the many growth submodels of FVS, carried out based on more than 140,000 tree measurements (11,000 sample plots, years 2002-2003 inventory), enabled managers to rely on more accurate growth predictions. Flexibility to user’s input is among the desired features of a species-wide prediction model for Scots pine dynamics. De-construction, calibration and testing of an existing forest growth and yield model over localized inventory data provided the basis to propose data and research needs for implementing such framework in Alpine forests.
Last, the design and implementation of a Density Management Diagram proved useful to project, visualize and compare silvicultural goals and management strategies aimed at their pursuit. The diagram is based upon the self-thinning law. It was designed using region-wide forest inventory data, and field-based data from permanent plots as a control and validation dataset. By characterizing silvicultural goals in terms of quantitative stand parameters, we devised different scenarios according to the functions whose supply is demanded to the pine forest, and effectively compared the trajectories of stand development associated to alternative management strategies. We also tested implementation on the diagram of natural disturbance regimes, which we reconstructed from historical and field evidence, in order to forecast the most likely stand response.
The combined analysis of different spatio-temporal scales, i.e., region-wide forest inventories and intensive plot measurements, allowed us to model inferred dynamics across a wide range of organization levels in the community, from trees to whole landscapes. The establishment of a permanent monitoring network will prove its utility with upcoming repeated measurements. The natural prosecution of this study will be the design of a inventory network suitable for constructing a local variant of the described model, and the statistical implementation of such tool in mountain forests of the Alps over a wider range of key species.
Lo Stand density index di Reineke (1933) esprime la relazione negativa tra il numero di piante per unità di superficie e il diametro medio in popolamenti coetanei non disturbati, definendo una base scientifica per valutare la competizione e lo stress nei popolamenti forestali. Il contributo delle singole componenti del popolamento allo Stand density index totale è additivo, cosicché questo indice è applicabile a strutture sia coetanee che disetanee e irregolari. Vengono presentati i diversi contributi che la ricerca ha apportato alla definizione di questa misura di densità; nella realtà italiana si propone di dare un particolare risalto alle applicazioni ecologiche dello Stand density index, che può essere utilizzato per valutare gli habitat di diverse specie animali o la stabilità biologica e strutturale dei popolamenti.
L’obiettivo della ricerca è introdurre i concetti propri dello Stand density index nella selvicoltura italiana, applicando i metodi per la sua valutazione a popolamenti di abete bianco (Abies alba Mill.) in provincia di Cuneo. Si sono utilizzati allo scopo i dati rilevati in occasione della redazione dei Piani forestali territoriali della Regione Piemonte, che hanno così potuto trovare un’adeguata valorizzazione; i dati provengono da 186 aree di saggio, dislocate nella fascia montana e subalpina della provincia.
Un modello di autodiradamento lineare, caratterizzato da semplicità di elaborazione e da un buon adattamento ai dati del campione, è stato ritenuto adeguato ad una ricerca di carattere esplorativo. Si è valutato lo Stand density index massimo che i popolamenti di abete bianco possono assumere, sia con il metodo tradizionale che con quello additivo; quest’ultimo, più consono alla particolare struttura dei boschi in esame, ha prodotto valori di Stand density index minori. Per elaborare la relazione completa tra diametro medio e densità per i popolamenti osservati sono state scelte solo le aree in cui l’abete bianco rappresentava almeno l’80% dell’area basimetrica. Applicando al nuovo campione, composto di 77 aree di saggio, un modello di regressione lineare, la pendenza della linea limitante dimensione-densità per l’abete bianco è risultata essere -1,491, un valore minore ma non significativamente differente da quello originariamente indicata da Reineke per diverse specie (-1,605). Si propone di calcolare lo Stand density index dei singoli popolamenti assumendo come esponente il valore individuato, e di utilizzare la formulazione additiva che è la più generalmente applicabile. Seguendo tali indicazioni, si è individuato quale Stand density index massimo per l’abete bianco il valore di 1359 in unità di misura metriche decimali. Tale valore è stato messo a confronto con quelli indicati in letteratura per la stessa specie e per specie ecologicamente simili.
I popolamenti esaminati nel loro complesso mostrano Stand density index variabili dal 6% al 162% rispetto al massimo; tuttavia, il 50% dei popolamenti ha uno Stand density index compreso tra il 35% e il 60%, ed il 74% del campione mostra uno Stand density index variabile dal 25% al 60% del valore massimo. In base ai risultati è possibile affermare che la maggior parte delle abetine esaminate si trovano ad uno stadio di sviluppo inferiore al massimo teorico di sfruttamento delle risorse e di competizione per questa specie.
Lo Stand density index fornisce un valido modello delle dinamiche strutturali nei popolamenti di abete bianco; costituisce pertanto un efficace parametro descrittivo di carattere selvicolturale ed ecologico dei popolamenti forestali, e rappresenta un’utile base per elaborare previsioni di sviluppo dei popolamenti e confrontarle con gli obiettivi gestionali desiderati. La possibilità di seguire nel tempo lo sviluppo dei popolamenti potrebbe rivelarsi uno strumento prezioso per l’applicazione di modelli di sviluppo più dettagliati ed affidabili; ulteriori ricerche, effettuate su un campione rappresentativo di una realtà territoriale più estesa, potranno confermare le tendenze individuate.
rarely been discussed. We analyzed the abundance of Scots pine regeneration in a 257 ha wildfire in an inneralpine forest. Our aims were (1) to model fire intensity at the soil surface and topsoil heating along a gradient of increasing fire severities; (2) to assess the differences in soil properties along the fire severity gradient; (3) to model the effect of disturbance and soil legacies on the density of pine seedlings.We reconstructed fire behavior
and soil heating with the First Order Fire Effects Model (FOFEM), tested the effect of fire severity on soils by nonparametric distributional tests, and modeled seedling density as a function of site, disturbance and soil legacies by fitting a GLM following a variable selection procedure. Topsoil heating differed markedly between the moderate and high severity fires, reaching temperatures high enough to strongly and permanently alter soil
properties only in the latter. High fire severity resulted in decreased soil consistency and wet aggregate stability.
Burned soils had lower organic matter and cations than those unburned. Pine seedlings favored low-fertility, eroded, and chemically poor sites. Establishment was facilitated by the presence of coarse woody debris, but hampered by increasing distance from the seed source. These results suggest that in dry, inner-alpine valleys, fire residuals and soil legacies interact in determining the success of Scots pine re-establishment. High severity fire can promote favorable soil conditions, but distance from the seed source and high evaporation rates of bare soils must be mitigated in order to ensure a successful restoration.