The practice of salvage logging dead and damaged timber following large high severity disturbances has raised much controversy, partly because of the negative ecological effects that such practices ...have on forest ecosystems. Many of the studies on salvage logging effects, however, have been done on sites damaged by large, severe disturbances. Less is known about the ecological consequences of salvage logging following intermediate severity disturbances that cause partial canopy damage at smaller scales. We examined the response of the herbaceous layer and tree regeneration to salvaged and non-salvaged treatments following small-scale intermediate severity disturbances in eight mixed beech (Fagus sylvatica L.) dominated forest stands in Slovenia. The cover and diversity of herbaceous vegetation, as well as the density and diversity of tree regeneration were similar between treatments across the study sites. The only notable differences between the treatments were that salvaged sites had a larger proportion of shade intolerant tree species in the regeneration layer, while non-salvaged sites tended to have a more well-developed regeneration layer in taller height classes. The results suggest that salvage logging following small-scale intermediate severity disturbances may not hinder forest recovery in mixed beech dominated forests.
Our study focused on the functional aspects of plant species and vegetation at the transition from larch (
Larix decidua
Mill.) forest to mountain pine (
Pinus mugo
Turra) stands on the alpine ...treeline ecotone. With increasing elevation, living conditions grow harsher, which is reflected in the plant species and functional trait composition of plant communities. At four different localities in the Slovenian Alps, relevés along an altitudinal gradient and according to vegetation type were made (European larch forests, larch trees-mountain pine shrubs, mountain pine shrubs), using standard Central European phytocoenological method. In the upper mountain pine belt, few differential species were found, since most species represented in mountain pine stands also occurred in the lower two vegetation belts, while there were many differential species in the lower forest belt. Species with considerable competitive ability and moderate stress tolerance dominated the upper treeline ecotone, whereas ruderality is poorly expressed. The importance of stress tolerance in plant strategies increased slightly in the mountain pine belt. Changes in the representation of some functional traits attributes were detected by vegetation belts, but complete species turnover did not occur. Changes in dominant life form involved greater cover of chamaephytes and nanophanerophytes in the upper mountain pine belt. Species with evergreen leaves dominated mountain pine stands and deciduous forest stands. The share of species with scleromorphic leaves increased in the direction of the mountain pine belt while the share of species with mesomorphic and hygromorphic leaves declined. Mountain pine stands create good conditions for the regeneration of tree species and colonisation by ecologically more demanding forest species while species of alpine grasslands withdraw on open areas. Since today’s treeline is lowered due to past human activity, an upward shift is expected. Also, considering the great importance of competition strategy, current conditions in mountain pine stands are favourable for future forest succession.
Obična jela (Abies alba Mill.) je kao klimatogena vrsta izrazito skiofilna i jako učinkovita što se tiče primanja hrane iz okoliša. U Sloveniji obično raste na dubokim, teškim, svježim, neutrofilnim ...do acidofilnim staništima, u submontanskom i montanskom pojasu (Galio rotundifolii-Abietetum M. Wraber 1959, Bazzanio-Abietetum M. Wraber 1958), mjestimično se pojavljuje u sastojinama i na kamnitim karbonatima ili silikatnima podlogama (Calamagrostio-Abietetum Horvat (1950) 1962, Paraleucobryo-Abietetum Belec et al. ex Belec 2009, Neckero-Abietetum Tregubov 1962). U članku smo predstavili istraživanje gotovo čiste sastojine obične jele (Abies alba Mill.) na za nju neuobičajnom staništu. Jelova sastojina u šumskom rezervatu Lipje u Poljanskoj dolini (Slovenija) uspijeva na prisojnom položaju, razmjerno niskoj nadmorskoj visini (370–380 m) i na karbonatnoj matičnoj podlozi. Sustavnih istraživanja u rezervatu do sada još nije bilo, ali se pretpostavlja da je sastojina nastala poslije sekundarne sukcesije na nekadašnjim pašnjacima. Svrha ovoga istraživanja je (1) analizirati povijest šumskog rezervata i jelove sastojine, (2) istražiti strukturne i razvojne karakteristike jelove sastojine, (3) usporediti florni sastav rezervata sa srodnim asocijacijama fitocenoza. Povijest sukcesije sastojine utvrdili smo uz pomoć stare vojničke karte. U sastojini smo na većoj pokusnoj plohi napravili totalnu klupažu, na dominantnim stablima izmjerili visine i uzeli izvrtke. Na manjim plohama analizirali smo pomlađivanje i brst divljači. Dodatno je napravljeno pet fitocenoloških snimaka po standardnoj srednjeeuropskoj metodi.Na vojničkoj karti iz godine 1763–1787. godine, područje današnjeg rezervata leži na prijelazu iz šume u pašnjake, koji su u tom razdoblju većih površina, što potvrđuje sumnje na sekundarnu sukcesiju. Dobna struktura sastojine ukazuje na početak sukcesije jele u godinama 1900–1910.godine. Prirastni uzorci dominantnog drveća jele i njihova umjerena starosna varijabilnost ukazuju da jela nije odjednom kolonizirala nešumsku površinu, nego se postepeno širila sjemenom u postojećoj pionirskoj sastojini. Vitalnost jele i njena dominacija u sastojini, kao i struktura i pomlađivanje, ukazuju da se vjerojatno radi o dugotrajnom stadiju pretežito čiste jelove sastojine (udio jele u drvnoj zalihi iznosi 76.5 %). Karakteristika sastojine je i visoka drvna zaliha (773.6 m3 ha–1) i malen udio mrtvog drveta (4.1 %). Analiza prizemne vegetacije ukazuje na povoljne stanišne prilike u šumskom rezervatu Lipje. To i potvrđuje veći udio vrsta razreda Carpino-Fagetea s. lat. U usporedbi s ostalim zajednicama šuma bukve i bijelog graba ima više umjereno acidofilnih vrsta razreda Vaccinio-Piceetea, što je povezano s djelomičnim zakiseljenjem staništa zbog jelovih iglica koja dominira u gornjem sloju. Veći udio fanerofita i geofita ukazuje na potencijalno stanište bukve ili bijelog graba. Indikacija stanišnih prilika s Ellenbergovima fitoindikacijskima vrijednostima svrstava šumu jele u rezervatu bliže staništima bijelog graba, što ukazuje da se tu vjerojatno radi o sekundarnoj šumi jele kao posljedici zarastanja te da će budući sukcesijski razvoj vjerojatno ići u smjeru bjelogorične šume. DCA analiza popisa iz Lipja i srodnih fitocenoza ukazuje na prijelazni karakter, između šuma jele (Galio rotundifolii-Abietetum M. Wraber 1959), šuma bukve i jele (Omphalodo-Fagetum (Tregubov 1957) Marinček & al. 1993), šuma bijelog graba (Abio albae-Carpinetum betuli Marinček 1994, Asperulo-Carpinetum M. Wraber 1969) i submontanskih šuma bukve (Hacquetio-Fagetum Košir 1962). S obzirom na prevladavajući udio jele u dominantnom sloju, koja inače djelomično mijenja kiselost i svjetlosne prilike u sastojini, rezultati ukazuju na potencijalno stanište bijelog graba ili bukve. U florističkom smislu stanište najviše sliči sekundarnoj asociaciji Asperulo-Carpinetum betuli i zajednici bijelog graba i jele (Abio albae-Carpinetum betuli).Istraživanje je pokazalo da jela može kolonizirati nova staništa u procesu sekundarne sukcesije, nasuprot stajalištu koje zagovara izostanak jele zbog antropozoogenih utjecaja. Poznato je više sličnih staništa, gdje izvor dominacije jele nije poznat. Za objašnjenje uzroka općenitog propadanja jele potrebno je izvršiti istraživanja koja će osvijetliti zapletene međusobne odnose između jele i kompetitorskih vrsta, okolišnih prilika i antropogenog utjecaja. Možemo zaključiti da proučavana sastojina jele koja uspijeva na samom rubu ekološke niše jelovih šuma, ulijeva optimizam za budućnost jele.
The COVID-19 epidemic has shown that efficient prediction models are required, and the well-known SI, SIR, and SEIR models are not always capable of capturing the real dynamics. Modified models with ...novel structures could help identify unknown mechanisms of COVID-19 spread.
Our objective is to provide additional insights into the COVID-19 spread mechanisms based on different models' parameterization which was performed using evolutionary algorithms and the first-wave data.
Data from the Our World in Data COVID-19 database was analysed, and several models-SI, SIR, SEIR, SEIUR, and Bass diffusion-and their variations were considered for the first wave of the COVID-19 pandemic. The models' parameters were tuned with differential evolution optimization method L-SHADE to find the best fit. The algorithm for the automatic identification of the first wave was developed, and the differential evolution was applied to model parameterization. The reproduction rates (R0) for the first wave were calculated for 61 countries based on the best fits.
The performed experiments showed that the Bass diffusion model-based modification could be superior compared to SI, SIR, SEIR and SEIUR due to the component responsible for spread from an external factor, which is not directly dependent on contact with infected individuals. The developed modified models containing this component were shown to perform better when fitting to the first-wave cumulative infections curve. In particular, the modified SEIR model was better fitted to the real-world data than the classical SEIR in 43 cases out of 61, based on Mann-Whitney U tests; the Bass diffusion model was better than SI for 57 countries. This showed the limitation of the classical models and indicated ways to improve them.
By using the modified models, the mechanism of infection spread, which is not directly dependent on contacts, was identified, which significantly influences the dynamics of the spread of COVID-19.
PurposeThis paper aims to analyse the main variables and causal relationships in the system structure of the diversification of non-agricultural activities on agricultural holdings using system ...dynamics (SD) modelling. The SD model aims to simulate depictions of the behaviour of the real system while testing the effects of alternative decisions over time.Design/methodology/approachAn SD methodology was chosen to model diversification in farm tourism.FindingsA system approach increases the authors’ understanding of the transition of agricultural holdings to farm tourism. The results indicate that the transition to farm tourism depends on the level of tourism development in a certain area. The system is influenced by subsidies allocated by authorities to expand primary agricultural activities. The model describes a situation in which the tourism and agricultural industries have been affected by the COVID-19 pandemic.Research limitations/implicationsThe research is limited by the small set of available data due to the limited number of farms in Slovenia. One major problem is the difference in statistical data on the same activity collected from different institutions in Slovenia.Practical implicationsThe paper includes implications for understanding the transition process to farm tourism, allowing policymakers to experiment with subsidies and promotion to explore the efficacy and efficiency of proposed policies.Originality/valueThis study provides a structured, systemic view of the diversification of non-agricultural activities on agricultural holdings, where the simulation results are a reliable reflection of the behaviour of the actual system being modelled.
PDF
