Papers by Paolo De Angelis
Forests, 2020
The tree belowground compartment, especially fine roots, plays a relevant role in the forest ecos... more The tree belowground compartment, especially fine roots, plays a relevant role in the forest ecosystem carbon (C) cycle, contributing largely to soil CO2 efflux (SR) and to net primary production (NPP). Beyond the well-known role of environmental drivers on fine root production (FRP) and SR, other determinants such as forest structure are still poorly understood. We investigated spatial variability of FRP, SR, forest structural traits, and their reciprocal interactions in a mature beech forest in the Mediterranean mountains. In the year of study, FRP resulted in the main component of NPP and explained about 70% of spatial variability of SR. Moreover, FRP was strictly driven by leaf area index (LAI) and soil water content (SWC). These results suggest a framework of close interactions between structural and functional forest features at the local scale to optimize C source–sink relationships under climate variability in a Mediterranean mature beech forest.
Forest@ - Rivista di Selvicoltura ed Ecologia Forestale, 2009
Soil carbon accumulation in a Populus spp. plantation supplied with high atmospheric CO 2 and nit... more Soil carbon accumulation in a Populus spp. plantation supplied with high atmospheric CO 2 and nitrogen fertilization. This work was carried out in the experimental area POPFACE (Tuscania, Viterbo, Italy), where a poplar short rotation forest (SRF) was treated with 550 ppm of atmospheric CO 2 for six years. The experimental plots (Control and FACE) were divided in two halves, one of which was treated with nitrogen fertilization. The general aim of this research was to quantify the impact of the two rotation cycles, the CO 2 enrichment and the nitrogen fertilization on: i) soil organic matter fractions more relevant for microbial metabolism; ii) microbial C mineralization activity; and iii) the ecosystem capacity to store C in the soil. On soil samples collected from 2000 to 2004, the soil Organic C (TOC), the total extractable C (TEC) and several labile C fractions (MBC, WSC, ExC) were analysed. The microbial mineralization activity was also analysed. In comparison with the previous culture crop, the plantation increased the organic C storage in soil by about 23% in the second rotation cycle. Under elevated CO 2 , the increase of above-and belowground productivity supported a greater accumulation of labile C in soil, favouring a microbial C immobilization process. Fertilization treatment induced short-term changes in the soil C content, without overall modifications in the second rotation cycle.
A high-density plantation of three genotypes of Populus was exposed to an elevated concentration ... more A high-density plantation of three genotypes of Populus was exposed to an elevated concentration of carbon dioxide ([CO2]; 550 µmol mol¿1) from planting through canopy closure using a free-air CO2 enrichment (FACE) technique. The FACE treatment stimulated gross primary productivity by 22 and 11% in the second and third years, respectively. Partitioning of extra carbon (C) among C pools of
Forest@ - Rivista di Selvicoltura ed Ecologia Forestale, 2007
Mediterranean countries are expected to experience a notable increase in average air temperatures... more Mediterranean countries are expected to experience a notable increase in average air temperatures and an alteration of precipitation patterns, distribution, intensity and duration, as a result of global climate changes. In this region, wetlands and coastal areas are increasingly at risk, as they are particularly exposed to a range of hazards connected to climate change, such as drought, flooding, and soil salinity. Nevertheless, the species which inhabit these areas are likely to be well adapted to future conditions caused by global warming effects. Among them, Tamarix species have been reported to be highly tolerant to many abiotic stresses including salinity, drought, flooding, and extreme temperatures. Exploring their diversity could be fundamental, as genotypes can be selected for their natural tolerance to some particular stress, and may be conserved and used in restoration practices under the perspectives of global climate changes. Moreover, recent experimental evidence supported the employment of Tamarix spp. as bio-fuel crops. There are eleven Tamarix species in Italy, occupying coastal dunes and the riverbanks of Southern regions. The most widespread species are Tamarix gallica and Tamarix africana. Although they play a fundamental ecological role in dunes' fixation and in inhabiting salinized areas, which would otherwise be subjected to desertification, they are still not well known. In this study, we introduce Italian Tamarix spp. ecological, physiological, morphological and genetic diversity with the aim of creating awareness as regards their potential use for the recovery of degraded areas in the Mediterranean Basin.
Science of the Total Environment, 2006
Soil carbon (C) long term storage is influenced by the balance among ecosystem net primary produc... more Soil carbon (C) long term storage is influenced by the balance among ecosystem net primary productivity (NPP), the rate of delivery of new organic matter to soil pools and the decomposition of soil organic matter (SOM). The increase of NPP under elevated CO(2) can result in a greater production and higher turnover of fine roots or root exudation and, in turn, in an increase of labile C belowground. The aim of this work was to detect if changes in labile C substrates influenced the organic C storage in soils, verifying (i) whether treatments with elevated CO(2) and N fertilization induced changes in the amount and quality of labile C pools and in microbial C immobilization and (ii) whether these changes provoked modifications in the microbial C mineralization activity, and therefore changes in soil C losses. The effect of elevated CO(2) was a significant increase in both seasons (June and October 2004), of all labile C fractions: microbial biomass C (MBC), K(2)SO(4) extractable C (ExC), and water soluble C (WSC). The C/N ratio of the microbial biomass and of the K(2)SO(4) extractable SOM presented a seasonal fluctuation showing higher values in June, whereas the elevated CO(2) increased significantly the C/N ratio of these fractions independent of the season and the N addition, indicating a lower quality of labile SOM. Microbial respiration was more than doubled in October compared to June, confirming that changes in substrate quality and nutrient availability, occurring in the plantation at the beginning and at the end of the vegetative period, influenced the microbial activity in the bulk soil. Furthermore, the microbial respiration response to N fertilization was dependent on the season, with an opposite effect between June and October. The kinetic parameters calculated according to the first-order equation C(m)=C(0)(1-e(-kt)) were unaffected by elevated CO(2) treatment, except C(0)k and MR(basal), that showed a significant reduction, ascribable to (i) a lower quality of labile pools, and (ii) a more efficient microbial biomass in the use of available substrates. The C surplus found in elevated CO(2) soils was indeed immobilized and used for microbial growth, thus excluding a priming effect mechanism of elevated CO(2) on SOM decomposition.
iForest - Biogeosciences and Forestry, 2009
Forested areas are important in arid and semi-arid regions primarily to combat desertification, b... more Forested areas are important in arid and semi-arid regions primarily to combat desertification, but also to increase carbon sinks. To reverse the land degradation processes, restoration in the Mediterranean Basin had been frequently obtained by planting indigenous and exotic conifers, but it has been demonstrated that shrubs are nurse species for tree seedlings. Furthermore, planting indigenous shrubs is more efficient than allochthonous in restoring degraded soils. The aims of this work were: 1) to illustrate an experimental area in Sardinia used as a test-site to build up afforestation and reforestation activities in arid and semi-arid areas with autochthonous shrub species; 2) to show the results on plant survival and biomass one year after plantation trying to explain the role of different densities and specific compositions; 3) to hypothesize some trends of C accumulation of this "artificial" Mediterranean semi-arid shrubland by comparison with data found in the literature. The area is located in North West Sardinia, and is characterized by a Mediterranean climate. The revegetation was set up in February 2006, planting local species (Juniperus phoenicea, Pistacia lentiscus and Rosmarinus officinalis). Three densities and three specific compositions (monospecific plots with P. lentiscus, monospecific plots with J. phoenicea and mixed plots with the three cited species) were combined. One month after plantation, almost all plants were alive, but mortality increased after summer, independently of the treatments, likely due to summer drought. During the first year, no differences among the densities and the specific compositions were observed. Total above-ground biomass was in the range of 0.8-3.0 g m-2. Below-ground biomass was in the range of 0.9-1.7 g m-2. A significant lower biomass was measured in October, especially in the Pistacia plots. Higher densities and plant mixing seemed to better perform, allowing establishment of species with a strong pioneer behaviour and aridity resistant characteristics. Data collection on initial conditions and recurrent monitorings will be basic for evaluating in the long term the potential positive effects on C stock and on biodiversity of afforestation activities in arid and semi-arid areas.
Carbon Dioxide, Populations, and Communities, 1996
Forestry Sciences, 1998
Global change is becoming a decisive environmental issue of the present time; to elucidate causes... more Global change is becoming a decisive environmental issue of the present time; to elucidate causes and effects at the atmosphere and biosphere levels, a major effort is being devoted world-wide, by the scientific community. Forest ecosystems can contribute to mitigate these changes because of their key role played in the energy and mass exchanges between the atmosphere and the geosphere. Several, important scientific and methodological problems still need to be solved in order to fully understand mitigation potentials of temperate forests and to answer to questions about their optimal management strategies. In this paper, results of recent researches conducted on global change and temperate forests will be provided.
Tree Physiology, 2007
We estimated nitrogen (N) use by trees of three poplar species exposed for 3 years to free air CO... more We estimated nitrogen (N) use by trees of three poplar species exposed for 3 years to free air CO 2 enrichment (FACE) and determined whether the CO 2 treatment affected the future N availability of the plantation. Trees were harvested at the end of the first 3-year rotation and N concentration and content of woody tissues determined. Nitrogen uptake of fine roots and litter was measured throughout the first crop rotation. The results were related to previously published variations in soil N content during the same period. We estimated retranslocation from green leaves and processes determining N mobilization and immobilization, such as mineralization and nitrification, and N immobilization in litter and microbial biomass. In all species, elevated CO 2 concentration ([CO 2 ]) significantly increased nitrogen-use efficiency (NUE; net primary productivity per unit of annual N uptake), decreased N concentration in most plant tissues, but did not significantly change cumulative N uptake by trees over the rotation. Total soil N was depleted more in elevated [CO 2 ] than in ambient [CO 2 ], although not significantly for all soil layers. The effect of elevated [CO 2 ] was usually similar for all species, although differences among species were sometimes significant. During the first 3-year rotation, productivity of the plantation remained high in the elevated [CO 2 ] treatment. However, we observed a potential reduction in N availability in response to elevated [CO 2 ].
Tree Physiology, 2013
The temporal variability of ecosystem respiration (R ECO) has been reported to have important eff... more The temporal variability of ecosystem respiration (R ECO) has been reported to have important effects on the temporal variability of net ecosystem exchange, the net amount of carbon exchanged between an ecosystem and the atmosphere. However, our understanding of ecosystem respiration is rather limited compared with photosynthesis or gross primary productivity, particularly in Mediterranean montane ecosystems. In order to investigate how environmental variables and forest structure (tree classes) affect different respiration components and R ECO in a Mediterranean beech forest, we measured soil, stem and leaf CO 2 efflux rates with dynamic chambers and R ECO by the eddy-covariance technique over 1 year (2007-2008). Ecosystem respiration showed marked seasonal variation, with the highest rates in spring and autumn and the lowest in summer. We found that the soil respiration (SR) was mainly controlled by soil water content below a threshold value of 0.2 m 3 m −3 , above which the soil temperature explained temporal variation in SR. Stem CO 2 effluxes were influenced by air temperature and difference between tree classes with higher rates measured in dominant trees than in co-dominant ones. Leaf respiration (LR) varied significantly between the two canopy layers considered. Non-structural carbohydrates were a very good predictor of LR variability. We used these measurements to scale up respiration components to ecosystem respiration for the whole canopy and obtained cumulative amounts of carbon losses over the year. Based on the up-scaled chamber measurements, the relative contributions of soil, stem and leaves to the total annual CO 2 efflux were: 56, 8 and 36%, respectively. These results confirm that SR is the main contributor of ecosystem respiration and provided an insight on the driving factors of respiration in Mediterranean montane beech forests.
Plant, Cell and Environment, 1996
ABSTRACT
Plant and Soil, 2008
Abstract Important effects of elevated [CO 2] on SOM are expected as a consequence of increased l... more Abstract Important effects of elevated [CO 2] on SOM are expected as a consequence of increased labile organic substrates derived from plants. The present study tests the hypotheses that, under elevated [CO 2]: 1) soil heterotrophic respiration will increase due ...
Journal of Soils and Sediments, 2007
Forest Ecology and Management, 2008
Fertilization is required to maintain production of short rotation forestry plantations and an un... more Fertilization is required to maintain production of short rotation forestry plantations and an understanding of nutrient cycling processes is crucial in order to assess long-term sustainability of these systems. Fertilization can alter root biomass growth and turnover and the chemical and biochemical properties of the soil thus affecting soil carbon dynamics and soil quality. The present study was conducted in a short-rotation forest located in central Italy where three poplar clones were grown, during the second cycle, in presence and absence of nitrogen (N) fertilization. In the year 2002, the first year after coppice, 212 kg N ha À1 was supplied (Navarsol 20: 16 ammonium-N and 4 nitrate-N) while, in the years 2003 and 2004, 290 kg N ha À1 (ammonium nitrate 34: 17 ammonium-N and 17 nitrate-N) was supplied. On soil samples collected in spring and autumn, throughout the 3 years, several chemical and biochemical indicators were measured. Aim of the study was to determine: (1) the temporal variation of the soil quality indicators tested in the plantation, (2) the effects of a 3-years fertilization on soil microbial biomass and its activity, in terms of C mineralization and (3) the consequent changes in soil organic carbon, soil nitrogen and nutrient availability. A pronounced increase of soil organic matter content was evident due to the presence of the poplar plantation on a former arable soil. The results showed short-and medium-term effects of fertilization. Fertilization did not modify soil capacity to accumulate organic matter in the medium term, although a positive variation of SOC was observed at the beginning of the study, probably in relation to the type of the fertilizer supplied. At the end of the third year, the fertilization did not change soil nitrogen concentration although significant increases were observed in October 2002 and 2003. Nitrate-N was the principal mineral form of nitrogen that responded to the treatment (mean effect: +119%) while ammonium-N concentration was low and underwent to a microbial immobilization process though this was season-dependent. Microbial respiration was affected by N addition only in the short-term incubation while no effects were detected in the cumulative CO 2 production over 10 days; this suggested a microbial selection towards microrganisms with a fast metabolism and more depending on nitrogen.
Environmental Pollution, 2007
The experiment was carried out on a short rotation coppice culture of poplars (POP-EUROFACE, Cent... more The experiment was carried out on a short rotation coppice culture of poplars (POP-EUROFACE, Central Italy), growing in a free air carbon dioxide enriched atmosphere (FACE). The specific objective of this work was to study whether elevated CO 2 and fertilization (two CO 2 treatments, elevated CO 2 and control, two N fertilization treatments, fertilized and unfertilized), as well as the interaction between treatments caused an unbalanced nutritional status of leaves in three poplar species (P. x euramericana, P. nigra and P. alba). Finally, we discuss the ecological implications of a possible change in foliar nutrients concentration. CO 2 enrichment reduced foliar nitrogen and increased the concentration of magnesium; whereas nitrogen fertilization had opposite effects on leaf nitrogen and magnesium concentrations. Moreover, the interaction between elevated CO 2 and N fertilization amplified some element unbalances such as the K/N-ratio.
Ecological Indicators, 2005
An understanding of microbial biomass and microbial activity as part of belowground processes as ... more An understanding of microbial biomass and microbial activity as part of belowground processes as affected by elevated CO 2 is crucial in order to predict the long-term response of ecosystems to climatic changes. The ratio of biomass C to soil organic C (Cmic:Corg), the metabolic quotient (the specific soil respiration of the microbial biomass, qCO 2), the C mineralization quotient (the fraction of total organic C mineralized throughout the incubation, qM), the microbial biomass change rate quotient (qC) and soil inorganic nitrogen content were determined on soil samples taken during 3 years (Fall 2000-Fall 2003) in a poplar plantation exposed to increased atmospheric CO 2 by means of FACE (Free Air CO 2 Enrichment) technique and nitrogen fertilization. A competition for nitrogen between plants and microrganisms, stronger in FACE plots, induced a stress condition within microbial community. FACE treatment provided C for microbial growth (Cmic:Corg), but reducing nitrogen availability, led to a higher microbial loss over time (qC). Nitrogen fertilization decreased microbial mortality lowering energetic maintenance requirements (qCO 2) and induced a short-term shift in favour of microrganisms more rapid in the use of the resources. The C mineralization quotient (qM) was not affected by either FACE nor fertilization treatment meaning that the fraction of total organic carbon mineralized during the incubation period did not vary significantly.
Applied Soil Ecology, 2005
Microorganisms are the regulators of decomposition processes occurring in soil, they also constit... more Microorganisms are the regulators of decomposition processes occurring in soil, they also constitute a labile fraction of potentially available N. Microbial mineralization and nutrient cycling could be affected through altered plant inputs at elevated CO 2. An understanding of microbial biomass and microbial activity in response to belowground processes induced by elevated CO 2 is thus crucial in order to predict the long-term response of ecosystems to climatic changes. Microbial biomass, microbial respiration, inorganic N, extractable P and six enzymatic activities related to C, N, P and S cycling (b-glucosidase, cellulase, chitinase, protease, acid phosphatase and arylsulphatase) were investigated in soils of a poplar plantation exposed to elevated CO 2. Clones of Populus alba, Populus nigra and Populus x euramericana were grown in six 314 m 2 plots treated either with atmospheric (control) or enriched (550 mmol mol À1 CO 2) CO 2 concentration with FACE technology (free-air CO 2 enrichment). Chemical and biochemical parameters were monitored throughout a year in soil samples collected at five sampling dates starting from Autumn 2000 to Autumn 2001. The aim of the present work was: (1) to determine if CO 2 enrichment induces modifications to soil microbial pool size and metabolism, (2) to test how the seasonal fluctuations of soil biochemical properties and CO 2 level interact, (3) to evaluate if microbial nutrient acquisition activity is changed under elevated CO 2. CO 2 enrichment significantly affected soil nutrient content and three enzyme activities: acid phosphatase, chitinase and arylsulphatase, indicators of nutrient acquisition activity. Microbial biomass increased by a 16% under elevated CO 2. All soil biochemical properties were significantly affected by the temporal variability and the interaction between time and CO 2 level significantly influenced b-glucosidase activity and microbial respiration. Data on arylsulphatase and chitinase activity suggest a possible shift of microbial population in favour of fungi induced by the FACE treatment.
Annals of Forest Science, 2001
Stem diameter, total plant height and number of sylleptic branches of three poplar (Populus) geno... more Stem diameter, total plant height and number of sylleptic branches of three poplar (Populus) genotypes were followed during the first growing season of a high density intensively cultured plantation (in Central Italy) both under ambient CO 2 (Control) and under elevated atmospheric CO 2 (550 ppm) using the FACE technique. The three poplar genotypes belonged to different species of Populus alba L., Populus nigra L. and Populus x euramericana Dode (Guinier). All three genotypes responded by an enhanced growth performance but the extent of their response to the FACE treatment was different. A stem volume index was calculated considering the stem composed by a truncated cone in the lower part and by a cone in the upper part. At the end of the first growing season, stem volume index was increased in the FACE treatment by 54% to 79% as compared to Control treatment, depending on the genotype. This increased stem volume index was caused by an increase of basal stem diameter rather than by an enhancement of plant height. Number of sylleptic branches was stimulated by more than 35% in the P. nigra genotype. The results confirm the optimal performance of this new POPFACE experiment and show the positive response of this fast-growing tree species to elevated CO 2 conditions at an ecosystem scale even if considering the genotypic differences. elevated CO 2 / FACE / short-rotation intensive culture / Populus / growth Résumé-Performance de croissance de plants de Populus exposés à une atmosphère enrichie en dioxide de carbone durant la première saison de croissance dans l'expérimentation POPFACE. Le diamètre du tronc, la hauteur totale et le nombre des branches sylleptiques de trois génotypes de peuplier (Populus) ont été suivis durant la première saison de croissance d'une plantation de haute densité en culture intensive (en Italie Centrale), à la fois sous air ambiant (350 ppm, plantes témoins), et sous atmosphère enrichie en CO 2 (550 ppm) en utilisant la technique FACE. Les trois génotypes de peuplier utilisés font partie d'espèces différentes : Populus alba L., Populus nigra L. et Populus x euramericana Dode (Guinier). Les trois génotypes ont tous répondu au traitement FACE par une augmentation de la croissance, mais avec des intensité différentes. Un index de volume du tronc a été calculé en considérant le tronc comme étant composé d'un cône tronqué pour sa partie inférieure, et d'un cône pour la partie supérieure. À la fin de la saison de croissance, l'index de volume du tronc était supérieur de 54 % à 79 %, en fonction du génotype, pour le traitement FACE par rapport aux plants témoins. Cette augmentation de l'index de volume du tronc est principalement due à l'augmentation du diamètre basal des troncs, plus qu'à
Agricultural and Forest Meteorology, 1995
The linkage between water utilization and photosynthetic processes is investigated using stable i... more The linkage between water utilization and photosynthetic processes is investigated using stable isotopes and eddy covariance techniques, allowing integration of physiological processes both at time and space scales, respectively. Using the ratio of the stable isotopes of hydrogen (hydrogen vs. deuterium) and discrimination of 13C vs. ~2C, the relationship between water sources (rain water vs. ground water) utilization and intercellular carbon dioxide concentration is analysed for various species of two different ecosystems: an alpine forest and a Mediterranean macchia. As an example of space scale integration of water-carbon coupling, the relationship between canopy carbon dioxide assimilation and bulk stomatal conductance, measured with eddy covariance, is presented for a macchia community and a low-productivity grassland.
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Papers by Paolo De Angelis