1,721,080 research outputs found
Seasonal changes in microbial nitrogen in an old broadleaf forest and in a neighbouring young plantation
No full textPit and mound influence on soil features in an Oriental Beech (Fagus orientalis Lipsky) forest
No full textWindthrow, i.e. the felling of trees by wind, occurs continually in forest ecosystems. The uprooting of old trees creates multiple microsites (e.g. pit and mound landscape) that are the main source of soil heterogeneity. To determine the impact of pit and mound landscapes on soil features, a beech forest of the Langa district (Mazandaran province, Northern Iran) was studied. An area of 25 ha was considered for this study wherein three microsites were distinguished, including pit bottom (pit), mount top (mound) and level areas (closed canopy). In this area, 22 uprooted trees were also found. Soil samples were collected at different depths (i.e. 0-15, 15-30 and 30-45 cm) from all microsites and analysed. Our study shows that windthrow events should be considered as an important factor in influencing forest ecosystem, as they affect physical (i.e. density, texture and water content), chemical (i.e. pH, organic C, total N, cation exchange capacity and available nutrients) and biological (i.e. soil microbial respiration and earthworm density/biomass) characteristics of soil, thus resulting in pit and mound microsites that may strongly differ with respect to the closed canopy
Testing the Height Variation Hypothesis with the R rasterdiv Package for Tree Species Diversity Estimation
Full text linkAbstract: Forest biodiversity is a key element to support ecosystem functions. Measuring biodiversity
is a necessary step to identify critical issues and to choose interventions to be applied in order to
protect it. Remote sensing provides consistent quality and standardized data, which can be used
to estimate different aspects of biodiversity. The Height Variation Hypothesis (HVH) represents an
indirect method for estimating species diversity in forest ecosystems from the LiDAR data, and it
assumes that the higher the variation in tree height (height heterogeneity, HH), calculated through
the ’Canopy Height Model’ (CHM) metric, the more complex the overall structure of the forest
and the higher the tree species diversity. To date, the HVH has been tested exclusively with CHM
data, assessing the HH only with a single heterogeneity index (the Rao’s Q index) without making
use of any moving windows (MW) approach. In this study, the HVH has been tested in an alpine
coniferous forest situated in the municipality of San Genesio/Jenesien (eastern Italian Alps) at 1100 m,
characterized by the presence of 11 different tree species (mainly Pinus sylvestris, Larix decidua, Picea
abies followed by Betula alba and Corylus avellana). The HH has been estimated through different
heterogeneity measures described in the new R rasterdiv package using, besides the CHM, also other
LiDAR metrics (as the percentile or the standard deviation of the height distribution) at various
spatial resolutions and MWs (ALS LiDAR data with mean point cloud density of 2.9 point/m2 ).
For each combination of parameters, and for all the considered plots, linear regressions between
the Shannon’s H0 (used as tree species diversity index based on field data) and the HH have been
derived. The results showed that the Rao’s Q index (singularly and through a multidimensional
approach) performed generally better than the other heterogeneity indices in the assessment of the
HH. The CHM and the LiDAR metrics related to the upper quantile point cloud distribution at fine
resolution (2.5 m, 5 m) have shown the most important results for the assessment of the HH. The size
of the used MW did not influence the general outcomes but instead, it increased when compared to
the results found in the literature, where the HVH was tested without MW approach. The outcomes
of this study underline that the HVH, calculated with certain heterogeneity indices and LiDAR data,
can be considered a useful tool for assessing tree species diversity in considered forest ecosystems.
The general results highlight the strength and importance of LiDAR data in assessing the height
heterogeneity and the related biodiversity in forest ecosystems
SPATIAL DYNAMICS OF LATE SUCCESIONAL SPECIES UNDER PINUS NIGRA STANDS IN THE NORTHERN APENNINES (ITALY)
No full textLitter quality changes during decomposition investigated by thermal analysis
No full textThe litter decomposition process depends on the litter chemical composition, especially the ratio between more labile compounds, cellulose, and the recalcitrant lignin and waxes. Their determination is crucial to predict the process, though lignin measurement presents some limitations due to drawbacks of the different methods. Thermal analysis has been successfully applied to several organic materials in order to obtain quali-quantitative information of the chemical structure of the sample. In this work TG-DTA was used in a short-term litter decomposition study of two broadleaf forest stands of contrasting ages, and the results were compared to those obtained with a chemical method (Klason’s method) commonly used to quantify cellulose and lignin. TG-DTA was applied to the litter and to the cell walls (CW) extracted from the litter, whose cellulose and lignin content was determined using the Klason’s method. When applied to litter, thermal analysis showed a weak correlation with the Klason’s method, though it allowed the detection of the dynamics of waxes, that increased during the decomposition and could influence the later stages of the process. Contrastingly, a good correlation between cellulose and lignin determined with the two methods was found when TG-DTA was applied to the CW. In this case TG-DTA, according to NMR data, also highlighted the changes in the CW chemical structure compared with that of the litters, in particular the loss of waxes and the decreased thermostability of aromatic components. Moreover, a new concept of quality of the decomposing litter, based on the balance between the energy stored in the litter and the energy needed to release it obtained by thermal analysis, was recently introduced. Samples of the old forest litter had an initial energetic balance more favorable than those collected in the young stand. At the end of the period, the decrease in litter quality was greater in the young than in the old forest samples, due to the combined effect of the higher degradation of thermolabile substances and the accumulation of more thermostable components. Thermal analysis seems to have a good potential in litter decomposition studies, as it can link structural and energetic changes during the process
Biochar mineralization and priming effect in a poplar short rotation coppice from a 3-year field experiment
No full textThe present study assesses the stability of biochar, its effect on original soil organic matter (SOM) decomposition, and the interactions with plant roots over a 3-year period in a short rotation coppice plantation in Northern Italy. Biochar produced from gasification of maize silage (δ13C of biochar ≈ - 13.8‰) was applied into the soil of the plantation (δ13C of SOM ≈ -23.5‰). Total and heterotrophic respirations were measured in control and biochar-treated plots, and the amount of biochar-derived carbon dioxide (CO2) was calculated using an isotopic mass balance method. Biochar mean residence time (MRT) was assessed using exponential decay models. The remaining amount of biochar at the end of the experiment was estimated by a soil isotopic mass balance. In the absence of plant roots, MRT of the more recalcitrant biochar fraction (96% of the total) was 24.3 years, significantly lower than expected from previous shorter-term studies or laboratory incubations. In the presence of plant roots, MRT decreased to 12.6 years, confirming the previously observed positive effect of roots on biochar decomposition. However, in the absence of roots, the biochar decreased the decomposition of original SOM by 16%, indicating long-lasting protective effect on SOM (negative priming effect). The soil isotopic mass balance suggested that part of the applied biochar could have been lost by downward migration. This study provides the first estimation of the biochar stability and priming effect on SOM in field conditions in the medium term0
WOOD-UP
Full text linkThe fundamental vision of the WOOD-UP project was to develop existing wood gasification plants in South Tyrol towards a polygenerative use in order to be able to produce not only energy but also high-quality charcoal (biochar) for the improvement of soil fertility and for climate protection. The project, funded by the European Regional Development Fund ERDF 2014–2020, was implemented by the Free University of Bolzano together with the Laimburg Research Centre. Based on the life cycle analysis (LCA) or scenario analysis of the entire production chain of wood gasification, strengths and weaknesses of the existing systems were identified with regard to their impact on the environment. Thanks to the results obtained, a number of suggestions for improvement could be formulated.; Il miglioramento verso un assetto poligenerativo degli attuali impianti altoatesini di gassificazione della biomassa legnosa, dove oltre all’energia si possa produrre biochar di qualità da impiegare in agricoltura come ammendante con effetti positivi sulla fertilità dei suoli e sulla mitigazione dei cambiamenti climatici è la visione che ha sostenuto il progetto WOOD-UP. Il progetto, finanziato con fondi FESR 2014-2020, ha visto la collaborazione tra la Libera Università di Bolzano e il Centro di Sperimentazione Laimburg. L’analisi del ciclo di vita e di scenario dell’intera filiera di gassificazione ha evidenziato elementi di forza e di debolezza dell’attuale filiera in termini di impatti ambientali e ha permesso di avanzare proposte di miglioramento sulla base dei risultati ottenuti dalla sperimentazione. ; Grundlegende Vision des Projektes WOOD-UP war die Entwicklung der bestehenden Holzvergasungsanlagen in Südtirol hin zu einer polygenerativen Nutzung, um neben Energie auch hochwertige Holzkohle (Biochar) zur Verbesserung der Bodenfruchtbarkeit und zum Klimaschutz erzeugen zu können. Das mit Mitteln aus dem Europäischen Fonds für regionale Entwicklung EFRE 2014–2020 finanzierte Projekt wurde von der Freien Universität Bozen gemeinsam mit dem Versuchszentrum Laimburg umgesetzt. Anhand der Lebenszyklusanalyse (LCA) bzw. der Szenarioanalyse der gesamten Produktionskette der Holzvergasung wurden Stärken und Schwächen der bestehenden Systeme hinsichtlich ihrer Auswirkungen auf die Umwelt aufgezeigt. Dank der erzielten Versuchsergebnisse konnte eine Reihe von Verbesserungsvorschlägen formuliert werden
The admixture of Quercus sp. in Pinus sylvestris stands influences wood anatomical trait responses to climatic variability and drought events
Full text linkIntroduction: Forests are threatened by increasingly severe and more frequent drought events worldwide. Mono-specific forests, developed as a consequence of widespread management practices established early last century, seem particularly susceptible to global warming and drought compared with mixed-species forests. Although, in several contexts, mixed-species forests display higher species diversity, higher productivity, and higher resilience, previous studies highlighted contrasting findings, with not only many positive but also neutral or negative effects on tree performance that could be related to tree species diversity. Processes underlying this relationship need to be investigated. Wood anatomical traits are informative proxies of tree functioning, and they can potentially provide novel long-term insights in this regard. However, wood anatomical traits are critically understudied in such a context. Here, we assess the role of tree admixture on Pinus sylvestris L. xylem traits such as mean hydraulic diameter, cell wall thickness, and anatomical wood density, and we test the variability of these traits in response to climatic parameters such as temperature, precipitation, and drought event frequency and intensity.Methods: Three monocultural plots of P. sylvestris and three mixed-stand plots of P. sylvestris and Quercus sp. were identified in Poland and Spain, representing Continental and Mediterranean climate types, respectively. In each plot, we analyzed xylem traits from three P. sylvestris trees, for a total of nine trees in monocultures and nine in mixed stands per study location.Results: The results highlighted that anatomical wood density was one of the most sensitive traits to detect tree responses to climatic conditions and drought under different climate and forest types. Inter-specific facilitation mechanisms were detected in the admixture between P. sylvestris and Quercus sp., especially during the early growing season and during stressful events such as spring droughts, although they had negligible effects in the late growing season.Discussion: Our findings suggest that the admixture between P. sylvestris and Quercus sp. increases the resilience of P. sylvestris to extreme droughts. In a global warming scenario, this admixture could represent a useful adaptive management option
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