Abstract The net ecosystem exchange (NEE) of successional stages of the Abies-dominated dark taig... more Abstract The net ecosystem exchange (NEE) of successional stages of the Abies-dominated dark taiga was measured in central Siberia (61°N 90°E) during the growing season of the year 2000 using the eddy covariance technique. Measurements started before snow melt and canopy activity in spring on day of year (DOY) 99 and lasted until a permanent snow cover had developed and respiration had ceased in autumn DOY 299. Three stands growing in close vicinity were investigated: 50 yr-old Betula pubescens (“Betula stand”, an early successional stage after fire), 250 yr-old mixed boreal forest, representing the transition from Betula-dominated to Abies-dominated canopies, and 200-yr-old Abies sibirica (“Abies stand”, representing a late successional stage following the mixed boreal forest). The mixed boreal forest had a multi-layered canopy with dense understory and trees of variable height and age below the main canopy, which was dominated by Abies sibirica, Picea obovata and few old Betula pubescens and Populus tremula trees. The Abies stand had a uniform canopy dominated by Abies sibirica. This stand appears to have established not after fire but after wind break or insect damage in a later successional stage. The stands differed with respect to the number of days with net CO2 uptake (Betula stand 89 days, mixed boreal forest 109 days, and Abies stand 135 days), maximum measured LAI (Betula 2.6 m2 m−2, mixed boreal forest 3.5 m2 m−2 and Abies stand 4.1 m2 m−2) and basal area (Betula stand 30.2 m2 ha−1, mixed boreal forest 35.7 m2 ha−1, and Abies stand 46.5 m2 ha−1). In the mixed boreal forest, many days with net daytime CO2 release were observed in summer. Both other sites were almost permanent sinks in summer. Mean daytime CO2 exchange rates in July were −8.45 μmol m−2 s−1 in the Betula stand, −4.65 μmol m−2 s−1 in the mixed boreal forest and −6.31 μmol m−2 s−1 in the Abies stand. Measured uptake for the growing season was −247.2 g C m−2 in the Betula stand, −99.7 g C m−2 in the mixed boreal forest and −269.9 g C m−2 in the Abies stand. The total annual carbon uptake might be slightly lower (i.e. less negative) due to some soil respiration under snow in winter. The study for the first time demonstrates that old forests in the “Dark Taiga” are carbon sinks and that sink activity is very similar in late and early successional stages. Canopy and crown structure with associated self-shading and available radiation are suggested as possible causes for the observed differences.
L’uomo nel tentativo di comprendere la realta che lo circonda tende ad organizzarla in relazioni ... more L’uomo nel tentativo di comprendere la realta che lo circonda tende ad organizzarla in relazioni di causa-effetto in cui diversi elementi si trovano ad interagire, astrae cioe, dalla realta, dei sistemi. La gestione dei sistemi e rappresentata come una serie di azioni, collocate nello spazio e nel tempo, determinate alla massimizzazione dei risultati attesi (nel lungo termine) ed alla minimizzazione degli impatti, preservando cosi la funzionalita (sostenibilita dell’azione) dei sistemi stessi; ne sono, inoltre, analizzate le regole fondamentali. I rimboschimenti attraverso l’integrazione di nuovi elementi modificano le relazioni del sistema al fine di ottenere un nuovo equilibrio, piu idoneo all’insediamento ed allo sviluppo della vegetazione forestale. L’artificiosita dei rimboschimenti di pino nero dei rilievi dell’Italia peninsulare fa si che le variabili strutturali del popolamento non siano in equilibrio con le variabili ambientali della stazione rendendo, percio, necessaria l’azione selvicolturale. Delle foreste, e percio anche dei rimboschimenti, a causa della dinamicita del sistema e della imperfezione delle conoscenze umane, non e possibile conoscere tutti gli elementi e tutte le relazioni. La loro gestione pertanto deve trarre indicazioni dagli strumenti d’analisi disponibili, ma non puo prescindere dalle capacita di conoscenza e dal giudizio discrezionale del tecnico forestale il quale, ad oggi, e l’unico in grado di comprendere le realta forestali e, dopo aver compiuto un lavoro d’analisi, di sintetizzare un’ipotesi gestionale. Egli deve valutare criticamente le conoscenze acquisite e percio improntare della propria esperienza gli ordinamenti gestionali: la sensibilita, l’intuito, il buon senso del tecnico forestale vanno considerati strumenti di gestione fondamentali.
Tropical deforestation is an important issue in the debate over the global carbon cycle and clima... more Tropical deforestation is an important issue in the debate over the global carbon cycle and climate change. The release of CO2 due to tropical deforestation can be estimated from three main parameters: the level of tropical deforestation and degradation, the spatial distribution of forest types, and the amount of biomass and soil carbon for different forest types. Our knowledge of the rates of change of tropical forests and the distribution of forest types has greatly improved in the last few years through the use of earth observation technology. At the same time, more information has become available about carbon stocks for different forest types. Using recent figures on rates of net change for the world¿s tropical forest areas and refereed data on biomass, the source of atmospheric carbon from tropical deforestation is estimated to have been between 1.1 ± 0.3 gigatonnes of carbon per year (GtCyr-1) and 1.6 ± 0.6 GtCyr-1 for the 1990s. This estimate includes emissions from conversion of forests and loss of soil carbon after deforestation and emissions from forest degradation. It can be compared with CO2 emissions due to fossil fuel burning, which are estimated to have averaged 6.4 ± 0.4 GtCyr-1 in the 1990s. Reducing emissions from deforestation is therefore crucial in any effort to combat climate change. Reducing deforestation has many other positive aspects, such as preserving biodiversity, maintaining indigenous rights, and potentially bringing resources to local populations. The issue is even more important in the light of predicted future increases in deforestation rates. Between 1990 and 2000, the total area under agricultural or forest use decreased at a rate of 6.9 million hectares a year, dropping from 41.9 percent to 41.3 percent because of conversion to settlements or abandonment of agricultural or forest use (from soil degradation or desertification). This global pattern is the sum of two opposite trends: land area under agricultural use is increasing, and land area under forest use is decreasing. Furthermore, these trends are linked to development, with developed countries decreasing their agricultural land and increasing their forest area, and developing countries doing the opposite. Here we propose an accounting mechanism that includes options for determining global and national baselines of forest conversions. The accounting mechanism builds on recent scientific achievements related to the satellite-observation-based estimation of tropical deforestation rates and their consequences for carbon emissions and the assessment of intact forests. We analyze these scientific and technical achievements in the context of one item in the UN Framework Convention on Climate Change (UNFCCC), ¿reducing emissions from deforestation in developing countries.JRC.H.3-Global environement monitorin
Abstract The net ecosystem exchange (NEE) of successional stages of the Abies-dominated dark taig... more Abstract The net ecosystem exchange (NEE) of successional stages of the Abies-dominated dark taiga was measured in central Siberia (61°N 90°E) during the growing season of the year 2000 using the eddy covariance technique. Measurements started before snow melt and canopy activity in spring on day of year (DOY) 99 and lasted until a permanent snow cover had developed and respiration had ceased in autumn DOY 299. Three stands growing in close vicinity were investigated: 50 yr-old Betula pubescens (“Betula stand”, an early successional stage after fire), 250 yr-old mixed boreal forest, representing the transition from Betula-dominated to Abies-dominated canopies, and 200-yr-old Abies sibirica (“Abies stand”, representing a late successional stage following the mixed boreal forest). The mixed boreal forest had a multi-layered canopy with dense understory and trees of variable height and age below the main canopy, which was dominated by Abies sibirica, Picea obovata and few old Betula pubescens and Populus tremula trees. The Abies stand had a uniform canopy dominated by Abies sibirica. This stand appears to have established not after fire but after wind break or insect damage in a later successional stage. The stands differed with respect to the number of days with net CO2 uptake (Betula stand 89 days, mixed boreal forest 109 days, and Abies stand 135 days), maximum measured LAI (Betula 2.6 m2 m−2, mixed boreal forest 3.5 m2 m−2 and Abies stand 4.1 m2 m−2) and basal area (Betula stand 30.2 m2 ha−1, mixed boreal forest 35.7 m2 ha−1, and Abies stand 46.5 m2 ha−1). In the mixed boreal forest, many days with net daytime CO2 release were observed in summer. Both other sites were almost permanent sinks in summer. Mean daytime CO2 exchange rates in July were −8.45 μmol m−2 s−1 in the Betula stand, −4.65 μmol m−2 s−1 in the mixed boreal forest and −6.31 μmol m−2 s−1 in the Abies stand. Measured uptake for the growing season was −247.2 g C m−2 in the Betula stand, −99.7 g C m−2 in the mixed boreal forest and −269.9 g C m−2 in the Abies stand. The total annual carbon uptake might be slightly lower (i.e. less negative) due to some soil respiration under snow in winter. The study for the first time demonstrates that old forests in the “Dark Taiga” are carbon sinks and that sink activity is very similar in late and early successional stages. Canopy and crown structure with associated self-shading and available radiation are suggested as possible causes for the observed differences.
L’uomo nel tentativo di comprendere la realta che lo circonda tende ad organizzarla in relazioni ... more L’uomo nel tentativo di comprendere la realta che lo circonda tende ad organizzarla in relazioni di causa-effetto in cui diversi elementi si trovano ad interagire, astrae cioe, dalla realta, dei sistemi. La gestione dei sistemi e rappresentata come una serie di azioni, collocate nello spazio e nel tempo, determinate alla massimizzazione dei risultati attesi (nel lungo termine) ed alla minimizzazione degli impatti, preservando cosi la funzionalita (sostenibilita dell’azione) dei sistemi stessi; ne sono, inoltre, analizzate le regole fondamentali. I rimboschimenti attraverso l’integrazione di nuovi elementi modificano le relazioni del sistema al fine di ottenere un nuovo equilibrio, piu idoneo all’insediamento ed allo sviluppo della vegetazione forestale. L’artificiosita dei rimboschimenti di pino nero dei rilievi dell’Italia peninsulare fa si che le variabili strutturali del popolamento non siano in equilibrio con le variabili ambientali della stazione rendendo, percio, necessaria l’azione selvicolturale. Delle foreste, e percio anche dei rimboschimenti, a causa della dinamicita del sistema e della imperfezione delle conoscenze umane, non e possibile conoscere tutti gli elementi e tutte le relazioni. La loro gestione pertanto deve trarre indicazioni dagli strumenti d’analisi disponibili, ma non puo prescindere dalle capacita di conoscenza e dal giudizio discrezionale del tecnico forestale il quale, ad oggi, e l’unico in grado di comprendere le realta forestali e, dopo aver compiuto un lavoro d’analisi, di sintetizzare un’ipotesi gestionale. Egli deve valutare criticamente le conoscenze acquisite e percio improntare della propria esperienza gli ordinamenti gestionali: la sensibilita, l’intuito, il buon senso del tecnico forestale vanno considerati strumenti di gestione fondamentali.
Tropical deforestation is an important issue in the debate over the global carbon cycle and clima... more Tropical deforestation is an important issue in the debate over the global carbon cycle and climate change. The release of CO2 due to tropical deforestation can be estimated from three main parameters: the level of tropical deforestation and degradation, the spatial distribution of forest types, and the amount of biomass and soil carbon for different forest types. Our knowledge of the rates of change of tropical forests and the distribution of forest types has greatly improved in the last few years through the use of earth observation technology. At the same time, more information has become available about carbon stocks for different forest types. Using recent figures on rates of net change for the world¿s tropical forest areas and refereed data on biomass, the source of atmospheric carbon from tropical deforestation is estimated to have been between 1.1 ± 0.3 gigatonnes of carbon per year (GtCyr-1) and 1.6 ± 0.6 GtCyr-1 for the 1990s. This estimate includes emissions from conversion of forests and loss of soil carbon after deforestation and emissions from forest degradation. It can be compared with CO2 emissions due to fossil fuel burning, which are estimated to have averaged 6.4 ± 0.4 GtCyr-1 in the 1990s. Reducing emissions from deforestation is therefore crucial in any effort to combat climate change. Reducing deforestation has many other positive aspects, such as preserving biodiversity, maintaining indigenous rights, and potentially bringing resources to local populations. The issue is even more important in the light of predicted future increases in deforestation rates. Between 1990 and 2000, the total area under agricultural or forest use decreased at a rate of 6.9 million hectares a year, dropping from 41.9 percent to 41.3 percent because of conversion to settlements or abandonment of agricultural or forest use (from soil degradation or desertification). This global pattern is the sum of two opposite trends: land area under agricultural use is increasing, and land area under forest use is decreasing. Furthermore, these trends are linked to development, with developed countries decreasing their agricultural land and increasing their forest area, and developing countries doing the opposite. Here we propose an accounting mechanism that includes options for determining global and national baselines of forest conversions. The accounting mechanism builds on recent scientific achievements related to the satellite-observation-based estimation of tropical deforestation rates and their consequences for carbon emissions and the assessment of intact forests. We analyze these scientific and technical achievements in the context of one item in the UN Framework Convention on Climate Change (UNFCCC), ¿reducing emissions from deforestation in developing countries.JRC.H.3-Global environement monitorin
Uploads
Papers