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The cover of the herb layer (a), leaf area index (b), soil moisture content 5 h after watering (c), and soil moisture content 2 weeks after watering (d) in the three habitats (grassland, forest edge, and forest interior). C: control plots, W: watered plots
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Previous studies found that pedunculate oak, one of the most widespread and abundant species in European deciduous forests, regenerates in open habitats and forest edges, but not in closed forest interiors. However, these observations usually come from the core areas of the biome, and much less is known about such processes at its arid boundary, wh...
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... The Pannonian Basin is periodically exposed to droughts during the late summer and early autumn months [6], which in combination with local soil or topographic conditions limits the occurrence of deciduous trees, as their distribution is strictly determined by soil moisture availability [39,40]. As the amount of natural regeneration was strongly limited by aridity (Figure 2, Table 1) and on arid sites the transition to a higher category (>10 cm) (Figure 4) decreased, low soil moisture seems to be the most serious cause of poor seedling emergence and growth. ...
... In contrast, in the study site with the highest water availability (MED), a particularly negative effect of shrubs was observed, mainly in relation to more developed seedlings. As water supply is a crucial factor during oak germination and seedling development, shady conditions may be compensated by higher moisture, but the line between the positive and the negative influence of shading is narrow, and depends on microclimatic conditions, species mixture or developmental stage of regeneration [2,18,40]. ...
... In addition, the preference for south-facing slopes in winter significantly increases ungulate concentration and browsing probability [12]. Longterm exposure to browsing can lead to a strong reduction in canopy cover, which may allow grassland species to invade forest patches and eventually convert them to steppe [40,49]. ...
Forest–steppe ecosystems represent a heterogeneous small-patch landscape important as a biodiversity hotspot and habitat for many endangered species. In this work, we examine threatened forest–steppe communities using structural indices, browsing intensity and indices that consider herbivorous game preferences. The study aims to assess the abundance of natural regeneration and the browsing intensity in relation to different stand structures and to identify woody species threatened by selective browsing at three study sites on the Krupina Plateau in the southern part of central Slovakia. At each study site, three circular permanent research plots (PRPs), each 500 m2 in size, were established for stand structure analysis. Within each PRP, nine circular subplots with a radius of 2 m were established for detailed analysis of natural regeneration. The results of this study suggest that forest patches in the forest–steppe mosaic suffer from a long-term lack of natural regeneration, which is induced mainly by increasing aridity and ungulate pressure. Positive effects on the amount of natural regeneration were noted in association with the aggregated structure of forest patches and the presence of dead wood. Differentiated stand structure influenced the regeneration number in a negative way and at the same time significantly increased browsing intensity. In relation to a more advanced regeneration, shrubs had a protective effect against browsing. The feeding preferences of the animals can positively modulate the species composition and eliminate the imbalances in the regeneration in favor of the increasingly rare Quercus pubescens Willd.
... De altfel, evoluția compoziției arboretului în ultimele decenii arată o tendință similară: proporția frasinului s-a redus, pe când cea a carpenului și teiului a crescut (Tabelele 1 și 3 din Ghinescu et al. 2022). Rezultate similare privind rolul decisiv al uscăciunii (datorată căldurii excesive în contextul unor precipitații reduse și lipsei inundațiilor) au fost raportate pentru regenerarea stejarului pedunculat atât în Ungaria (Erdős et al. 2021) cât și în Slovenia (Čater și Batič 2006). ...
Lucrarea prezintă evoluția regenerării naturale instalate prin tăieri progresive într-un arboret de șleau de luncă. Cercetările au urmărit influența poziției în ochiurile de regenerare (marginea fertilă a ochiului; diferențe între zona centrală și cea de margine) precum și influența tipului de lucrare asupra creșterii regenerării naturale de stejar pedunculat din ochiuri. În acest sens, s-au aplicat lucrări de degajări în mod diferențiat: prin tăiere de jos a exemplarelor nedorite și prin frângerea exemplarelor nedorite la 1/3 și respectiv 1/2 din înălțimea stejarilor aleși a fi promovați. Pentru comparație, au fost lăsate și suprafețe neparcurse (martor). Rezultatele arată că marginea fertilă este în partea de sud-vest (dimensiunile puieților și biomasa lor au fost semnificativ mai mari în marginea aici față de marginea de nord-est) confirmând că factorul limitativ este uscăciunea estivală. Pentru toate variabilele măsurate (înălțime, diametru și biomasă totală supraterană), valorile au fost semnificativ mai mari în centrul ochiurilor față de margine. Așadar, în ciuda răririi arboretului între ochiuri, competiția cu arboretul matur pare să joace încă un rol important. Aplicarea diferențiată a lucrărilor, nu produce diferențe semnificative în zona centrală, deși apare o tendință ca tăierea de jos să conducă la arbori cu biomasă superioară față de celelalte două cazuri. La margine, unde domină competiția cu arboretul matern, situația este similară. Se observă însă efectul negativ asupra supraviețuirii stejarilor (numărul mediu fiind de doar 8,7 puieți pe suprafață de probă la margine, față de suprafețele intermediare și cele de centru, unde găsim 14,2, respectiv 13,1 puieți). Deci aplicarea lucrărilor la timp și cu consecvență rămâne un deziderat important. Întrucât puieții au atins deja (la doar șapte ani de la începerea tăierilor de regenerare) chiar și în marginea ochiurilor dimensiuni mult peste cele recomandate de normele tehnice silvice pentru aplicarea tăierilor de racordare, perioada de regenerare poate fi mai scurtă decât cea prevăzută în amenajament.
... The fact that climatic predictors differ among the main forest-steppe regions emphasizes that several factors should be considered when explaining why a certain area supports a forest-steppe mosaic. For example, in some areas of the Southeast Europe region, mean annual precipitation could be enough to support forest vegetation, but the drought period in summer may hinder the establishment of tree seedlings and thus can contribute to the existence of a forest-steppe mosaic [43][44][45] . Similarly, where annual precipitation is relatively high (Southeast Europe region and parts of the East Europe region, Fig. S1.1), natural (i.e., pre-human) wildfires and herbivores may have played a decisive role in limiting forest vegetation and maintaining the forest-steppe mosaic. ...
Eurasian forest-steppes form a 9000-km-long transitional zone between temperate forests and steppes, featuring a complex mosaic of herbaceous and woody habitats. Due to its heterogeneity regarding climate, topography and vegetation, the forest-steppe zone has been divided into several regions. However, a continental-scale empirical delineation of the zone and its regions was missing until recently. Finally, a map has been proposed by Erdős et al. based on floristic composition, physiognomy, relief, and climate. By conducting predictive distribution modeling and hierarchical clustering, here we compared this expert delineation with the solely macroclimate-based predictions and clusters. By assessing the discrepancies, we located the areas where refinement of the delineation or the inclusion of non-macroclimatic predictors should be considered. Also, we identified the most important variables for predicting the existence of the Eurasian forest-steppe zone and its regions. The predicted probability of forest-steppe occurrence showed a very high agreement with the expert delineation. The previous delineation of the West Siberia region was confirmed by our results, while that of the Inner Asia region was the one least confirmed by the macroclimate-based model predictions. The appropriate delineation of the Southeast Europe region from the East Europe region should be refined by further research, and splitting the Far East region into a southern and northern subregion should also be considered. The main macroclimatic predictors of the potential distribution of the zone and its regions were potential evapotranspiration (zone and regions), annual mean temperature (regions), precipitation of driest quarter (regions) and precipitation of warmest quarter (zone), but the importance of climatic variables for prediction showed great variability among the fitted predictive distribution models.
In the Eurasian forest-steppe, with increasing aridity, the balance between naturally co-existing forest and grassland patches is expected to shift towards grassland dominance in the long run, although feedback mechanisms and changes in land-use may alter this process. In this study, we compared old and recent aerial photographs of Hungarian forest-steppes to find out whether and how the forest proportion and the number of forest patches change at the decadal time scale. The percentage area covered by forest significantly increased in all study sites. The observed forest encroachment may be a legacy from earlier land-use: due to ceased or reduced grazing pressure, forests are invading grasslands until the potential forest cover allowed by climate and soil is reached. The number of forest patches significantly increased at one site (Fülöpháza), while it decreased at two sites (Bugac and Orgovány) and showed no significant change at the fourth site (Tázlár). This indicates that forest encroachment can happen at least in two different ways: through the emergence of new forest patches in the grassland, and through the extension and coalescence of already existing forest patches. Though the present work revealed increasing tree cover at a decadal time scale, the dynamic process should be monitored in the future to see how the vegetation reacts to further aridification. This could help devise a conservation strategy, as the woody/non-woody balance has a profound influence on basic ecosystem properties.
The regeneration, plant diversity, and change of soil properties are the determining
factors affecting the stability of natural forests. Road construction activities are considered
among the most important contributing factors. This study was conducted to
see if road construction has positive or negative effects on plant diversity, soil physicochemical
properties, and tree regeneration in arid woodlands and fulfill the lack of
information about road construction in arid woodlands. For this purpose, two roads
were selected in the arid woodlands of Bushehr Province, Iran. Twenty-four sampling
plots with an area of 200 square meters were selected on the RE and in the forest
interior around the studied roads. Plant species diversity, soil physiochemical properties,
and tree regeneration were determined in the studied plots. Our result indicated
49 plant species belonging to 20 families in the studied sites. RE plots represented
37 species while plots in the forest interior represented 40 species. Ficus johannis,
Ziziphus spina-christ, Eryngium billardieri, Astragalus fasciculifolius, Medicago rigidula,
Vicia peregrine, and Peganum harmala appeared only in the plots located at the
RE. But Dicyclophora persica, Convolvulus acanthocladus, Capparis parviflora, Pulicaria
aucheri, Senecio sp., Phlomis olivieri, Teucrium polium, Ziziphora tenuior, Salvia sp., Haplophyllum
canaliculatum, Fumaria parviflora, and Scabiosa olivieri appeared only in the
forest interior plots. Although no significant differences were observed for richness
between the RE and forest interior plots, Shannon–Wiener diversity indices revealed
significant differences between the studied groups. Therefore, the composition of
the plant species was not the same in the RE and forest interior plots. M. rigidula and
V. peregrine as nitrogen-fixating and palatable plant species appeared in the RE plots
but not in the interior plots. Moreover, medicinal plants like D. persica and
C. acanthocladus, P. aucheri, H. canaliculatum, and P. olivieri were recorded in the interior
plots. Besides, the tree regeneration and soil nutrients were significantly higher
in the RE plots compared to the interior plots. Overall, road construction in arid
woodlands results in plant and soil community changes. Nitrogen-fixing species
appeared by providing unfavorable environmental conditions for livestock grazing at
the RE. Therefore, soil nitrogen and organic matter increased, and consequently, tree
regeneration increased in the RE plots. In contrast, medicinal plants appeared in the
interior plots, where grazing pressure was higher than in the RE plots. Medicinal
plants probably produce some chemical components unfavorable for livestock
grazing.
Recent advances in ecology and biogeography demonstrate the importance of fire and large herbivores – and challenge the primacy of climate – to our understanding of the distribution, stability, and antiquity of forests and grasslands. Among grassland ecologists, particularly those working in savannas of the seasonally dry tropics, an emerging fire–herbivore paradigm is generally accepted to explain grass dominance in climates and on soils that would otherwise permit development of closed‐canopy forests. By contrast, adherents of the climate–soil paradigm, particularly foresters working in the humid tropics or temperate latitudes, tend to view fire and herbivores as disturbances, often human‐caused, which damage forests and reset succession. Towards integration of these two paradigms, we developed a series of conceptual models to explain the existence of an extensive temperate forest–grassland mosaic that occurs within a 4.7 million km2 belt spanning from central Europe through eastern Asia. The Eurasian forest‐steppe is reminiscent of many regions globally where forests and grasslands occur side‐by‐side with stark boundaries. Our conceptual models illustrate that if mean climate was the only factor, forests should dominate in humid continental regions and grasslands should prevail in semi‐arid regions, but that extensive mosaics would not occur. By contrast, conceptual models that also integrate climate variability, soils, topography, herbivores, and fire depict how these factors collectively expand suitable conditions for forests and grasslands, such that grasslands may occur in more humid regions and forests in more arid regions than predicted by mean climate alone. Furthermore, boundaries between forests and grasslands are reinforced by vegetation–fire, vegetation–herbivore, and vegetation–microclimate feedbacks, which limit tree establishment in grasslands and promote tree survival in forests. Such feedbacks suggest that forests and grasslands of the Eurasian forest‐steppe are governed by ecological dynamics that are similar to those hypothesised to maintain boundaries between tropical forests and savannas. Unfortunately, the grasslands of the Eurasian forest‐steppe are sometimes misinterpreted as deforested or otherwise degraded vegetation. In fact, the grasslands of this region provide valuable ecosystem services, support a high diversity of plants and animals, and offer critical habitat for endangered large herbivores. We suggest that a better understanding of the fundamental ecological controls that permit forest–grassland coexistence could help us prioritise conservation and restoration of the Eurasian forest‐steppe for biodiversity, climate adaptation, and pastoral livelihoods. Currently, these goals are being undermined by tree‐planting campaigns that view the open grasslands as opportunities for afforestation. Improved understanding of the interactive roles of climate variability, soils, topography, fire, and herbivores will help scientists and policymakers recognise the antiquity of the grasslands of the Eurasian forest‐steppe.
Overcoming establishment limitation is an integral task during forest restoration on degraded lands for tree species whose prominence is declining, such as those in the Quercus genus. Fallow agricultural lands are suitable for forest restoration efforts by planting seedlings; however, tree seedling success may be limited due to soil conditions that are distinct from relict forests. Here, we assessed soil nutrient content, physicochemical parameters, and microorganism function via soil enzyme activity from five restorations that were implemented 0, 7, 10, 50 or 100‐years ago. We planted Q. macrocarpa (bur oak) seedlings in soils collected from each site for 5 months before collecting dry biomass, used as a proxy for size. We found that Q. macrocarpa seedlings had the largest total biomass when they were planted in soils from older restorations. There was a significant positive correlation of the amount of soil carbon, nitrogen, organic matter and soil moisture with tree size, and these soil parameters increased with forest age. We assessed seedling roots for mutualistic ectomycorrhizal fungi, but we did not find associations between their presence and tree size. Forest restoration is a complex process which can take many decades, but we suggest that reforestation may be accelerated by implementing active soil restoration to increase soil carbon, nitrogen, and water holding capacity prior to planting tree seedlings in target sites. Active soil restoration may aide in overcoming a significant portion of establishment limitation of ecologically important tree species that typically do not fare well in early‐stage restorations. This article is protected by copyright. All rights reserved.
