7 research outputs found
Defoliation, Recovery and Increasing Mortality in Italian Forests: Levels, Patterns and Possible Consequences for Forest Multifunctionality
Forest health and multifunctionality are threatened by global challenges such as climate change. Forest health is currently assessed within the pan-European ICP Forests (International Co-operative Programme on Assessment and Monitoring of Air Pollution Effects on Forests) programme through the evaluation of tree crown conditions (defoliation). This paper analyses the results of a 24-year assessment carried out in Italy on 253 permanent plots distributed across the whole forested area. The results evidenced a substantial stability of crown conditions at the national level, according to the usual defoliation thresholds Defoliation > 25% and Defoliation > 60%, albeit with species-specific patterns. Within this apparent temporal stability, an increased fraction of extremely defoliated and dead trees was observed. Extreme defoliation mostly occurred in years with severe summer drought, whereas mortality was higher in the years after the drought. The results for singular species evidenced critical conditions for Castanea sativa Mill. and Pinus species, whereas Quercus species showed a progressive decrease in defoliation. Deciduous species, such as Fagus sylvatica L., Ostrya carpinifolia Scop. and Quercus pubescens Willd. suffer the loss of leaves in dry years as a strategy to limit water loss by transpiration but recover their crown in the following years. The recurrence of extreme heat waves and drought from the beginning of the XXI century may increase the vulnerability of forests, and increased tree mortality can be expected in the future
Ambient and substrate energy influence decomposer diversity differentially across trophic levels.
The species-energy hypothesis predicts increasing biodiversity with increasing energy in ecosystems. Proxies for energy availability are often grouped into ambient energy (i.e., solar radiation) and substrate energy (i.e., non-structural carbohydrates or nutritional content). The relative importance of substrate energy is thought to decrease with increasing trophic level from primary consumers to predators, with reciprocal effects of ambient energy. Yet, empirical tests are lacking. We compiled data on 332,557 deadwood-inhabiting beetles of 901 species reared from wood of 49 tree species across Europe. Using host-phylogeny-controlled models, we show that the relative importance of substrate energy versus ambient energy decreases with increasing trophic levels: the diversity of zoophagous and mycetophagous beetles was determined by ambient energy, while non-structural carbohydrate content in woody tissues determined that of xylophagous beetles. Our study thus overall supports the species-energy hypothesis and specifies that the relative importance of ambient temperature increases with increasing trophic level with opposite effects for substrate energy
Caso studio per l’integrazione di serie di dati faunistici in alcuni siti forestali LTER italiani
The Italian Long Term Ecological Research Network (LTER Italy) was founded, and included in the
International Network (ILTER), in 2006. The National Network includes today twenty sites in different
environments, five of them are in forest ecosystems. Most of monitoring and research activities at Italian
forest sites are carried on according to the protocols of the ICP Forests Programme, based on a permanent
monitoring plot of fixed shape and size (a square fenced area, 50x50 m wide) and focused on vegetation. The
present project was aimed at investigating the suitability of these monitoring plots to conduct ecological
research on a selected animal group, thus introducing a new research line on fauna at LTER Italy forest sites.
Saproxylic beetles were selected as target animal group. Saproxylic organisms are species living in or
depending on deadwood in one or more stages of their life cycle; for this reason, saproxylic beetles are very
significant for forest ecosystems. Two field tests were performed: the first field test was developed in 2010 at
four Italian forest plots in Lazio (Monte Rufeno, Acquapendente-VT; Monte Circeo, San Felice Circeo-LT)
and Abruzzo (Selva Piana, Collelongo-AQ; Rosello, Rosello-CH) Regions; the second field test was
conducted in 2011 in two forest plots in Oregon (U.S.A.), at the HJ Andrews Experimental Forest. All the
study areas are LTER sites. Emergence traps and flight interception traps were used to collect insects. One
thousand three hundred and seventy-two beetles were collected at the Italian study plots; three thousand six
hundred and ninety-four beetles were collected at U.S. plots. With the present research, significant
differences concerning assemblages of saproxylic beetles were detected among plots. Among Italian forest
sites, Rosello showed the highest species richness and diversity, while Monte Rufeno exhibited the highest
abundance. Results returned by the Andrews forest were consistent with the main findings, in spite of the
coarser taxonomic level of beetle data (family level): abundance was higher in the old-growth forest,
richness and diversity resulted slightly higher in the young stand. We found that, at the considered study
areas, saproxylic beetles are poliphagous species, they are not linked to species composition of tree
communities, but they exhibit preferences for structural traits of forests. We also found that, among habitat
factors, deadwood amount, decay class of deadwood, slope and stand age have the strongest effects on the
composition of assemblages of beetles.We can therefore say that the plot scale was able to reveal ecological
patterns. Saproxylic beetles represented a suitable target animal group to be investigated at small (plot) scale.
These outcomes are relevant with regards to LTER Italy forest sites, firstly because we demonstrate that
forest plots are useful to shift from vegetation monitoring to ecological investigations; secondly, because we
can suggest the integration of a research line regarding forest dwelling beetles inside existing long term data
sets. A few suggestions to improve the consistency of researches on saproxylic beetles at LTER forest plots
are the following: 1) field sampling based on random points: in fact, locations of ICP Forests plots were not
originally selected on a systematic grid, but subjectively chosen. Traps located randomly may overcome
statistical constraints deriving from non-random locations of study sites; 2) a higher number of space and
time replicates of plot sampling: multiple 50 x 50m sampling plots within the huge homogeneous area and
multiple sampling seasons may facilitate the ongoing process of plot upscaling. Ultimately, results of the
present project demonstrate that studies on lists of species or on indices derived from lists of species may
indeed be suitable to long term ecological research, unlike what other authors stated in the past
Caso studio per l’integrazione di serie di dati faunistici in alcuni siti forestali LTER italiani
The Italian Long Term Ecological Research Network (LTER Italy) was founded, and included in the
International Network (ILTER), in 2006. The National Network includes today twenty sites in different
environments, five of them are in forest ecosystems. Most of monitoring and research activities at Italian
forest sites are carried on according to the protocols of the ICP Forests Programme, based on a permanent
monitoring plot of fixed shape and size (a square fenced area, 50x50 m wide) and focused on vegetation. The
present project was aimed at investigating the suitability of these monitoring plots to conduct ecological
research on a selected animal group, thus introducing a new research line on fauna at LTER Italy forest sites.
Saproxylic beetles were selected as target animal group. Saproxylic organisms are species living in or
depending on deadwood in one or more stages of their life cycle; for this reason, saproxylic beetles are very
significant for forest ecosystems. Two field tests were performed: the first field test was developed in 2010 at
four Italian forest plots in Lazio (Monte Rufeno, Acquapendente-VT; Monte Circeo, San Felice Circeo-LT)
and Abruzzo (Selva Piana, Collelongo-AQ; Rosello, Rosello-CH) Regions; the second field test was
conducted in 2011 in two forest plots in Oregon (U.S.A.), at the HJ Andrews Experimental Forest. All the
study areas are LTER sites. Emergence traps and flight interception traps were used to collect insects. One
thousand three hundred and seventy-two beetles were collected at the Italian study plots; three thousand six
hundred and ninety-four beetles were collected at U.S. plots. With the present research, significant
differences concerning assemblages of saproxylic beetles were detected among plots. Among Italian forest
sites, Rosello showed the highest species richness and diversity, while Monte Rufeno exhibited the highest
abundance. Results returned by the Andrews forest were consistent with the main findings, in spite of the
coarser taxonomic level of beetle data (family level): abundance was higher in the old-growth forest,
richness and diversity resulted slightly higher in the young stand. We found that, at the considered study
areas, saproxylic beetles are poliphagous species, they are not linked to species composition of tree
communities, but they exhibit preferences for structural traits of forests. We also found that, among habitat
factors, deadwood amount, decay class of deadwood, slope and stand age have the strongest effects on the
composition of assemblages of beetles.We can therefore say that the plot scale was able to reveal ecological
patterns. Saproxylic beetles represented a suitable target animal group to be investigated at small (plot) scale.
These outcomes are relevant with regards to LTER Italy forest sites, firstly because we demonstrate that
forest plots are useful to shift from vegetation monitoring to ecological investigations; secondly, because we
can suggest the integration of a research line regarding forest dwelling beetles inside existing long term data
sets. A few suggestions to improve the consistency of researches on saproxylic beetles at LTER forest plots
are the following: 1) field sampling based on random points: in fact, locations of ICP Forests plots were not
originally selected on a systematic grid, but subjectively chosen. Traps located randomly may overcome
statistical constraints deriving from non-random locations of study sites; 2) a higher number of space and
time replicates of plot sampling: multiple 50 x 50m sampling plots within the huge homogeneous area and
multiple sampling seasons may facilitate the ongoing process of plot upscaling. Ultimately, results of the
present project demonstrate that studies on lists of species or on indices derived from lists of species may
indeed be suitable to long term ecological research, unlike what other authors stated in the past
Ambient and substrate energy influence decomposer diversity differentially across trophic levels
The species-energy hypothesis predicts increasing biodiversity with increasing energy in ecosystems. Proxies for energy availability are often grouped into ambient energy (i.e., solar radiation) and substrate energy (i.e., non-structural carbohydrates or nutritional content). The relative importance of substrate energy is thought to decrease with increasing trophic level from primary consumers to predators, with reciprocal effects of ambient energy. Yet, empirical tests are lacking. We compiled data on 332,557 deadwood-inhabiting beetles of 901 species reared from wood of 49 tree species across Europe. Using host-phylogeny-controlled models, we show that the relative importance of substrate energy versus ambient energy decreases with increasing trophic levels: the diversity of zoophagous and mycetophagous beetles was determined by ambient energy, while non-structural carbohydrate content in woody tissues determined that of xylophagous beetles. Our study thus overall supports the species-energy hypothesis and specifies that the relative importance of ambient temperature increases with increasing trophic level with opposite effects for substrate energy.ISSN:1461-023XISSN:1461-024