Knowledge of the quantity of twig dry mass (available fodder) of saplings is crucial for understanding tree recruitment under wild ungulate browsing pressure in forest ecosystems. Therefore, this ...study aimed to develop allometric equations for estimating twig dry mass using sapling structural data and to model the twig dry mass of saplings of various species in various size classes while quantitatively describing the variations among tree species. Sapling biomass samples were taken for six widely spread tree species in two national parks in Poland. After drying the biomass samples in the oven for 72 h at 65 °C, the data were analyzed, and models were generated using the ordinary least squares and generalized additive methods. The results confirmed our hypothesis that different tree species differ in their allometric properties. The twig dry masses of Acer pseudoplatanus and Carpinus betulus were best estimated by basal diameter, whereas those of Picea abies, Abies alba, and Fagus sylvatica were best estimated by sapling height. In contrast, the model quality for Fagus sylvatica and Sorbus aucuparia was enhanced by combining the sapling height with the mean largest crown length (MLCL). For all species, the twig dry mass distribution was linear along sapling height classes and exponentially increased with shoot diameter classes, with coniferous species exhibiting the highest correlation. On the other hand, the proportion of twig dry mass to total sapling dry mass followed the order S. aucuparia > A. alba > P. abies > F. sylvatica > C. betulus > A. pseudoplatanus. The developed allometric equations contribute significantly to the already available collection of published biomass equations. Moreover, they extremely useful in estimating the browsing potential of tree saplings falling within size ranges conducive to herbivore browsing.
The application of water-borne pressure-sensitive adhesives (PSA) based on acrylics is increasing in a variety of industrial areas. The have been used for manufacturing of double sided and carrier ...free mounting tapes, splicing tapes, marking and sign films, self-adhesive labels, packaging tapes, protective films and diverse high quality medical materials. Nano-sized inorganic fillers can modify diverse adhesive and self-adhesive coating properties such as tack, peel adhesion, shear strength at 20°C and 70°C, and removability Amorphous synthetic silica nanoparticles in form of water dispersions: Ludox PX-30 (30 wt.% silica stabilizing with counter ion sodium), Ludox PT-40 (40 wt.% silica stabilizing with counter ion sodium), Ludox PT-40AS (40 wt.% silica stabilizing with counter ion ammonium), and Ludox PW-50 (50 wt.% silica stabilizing with counter ion sodium) (from Grace) in concentrations between 1 and 5wt.% were used for modifying of water-born pressure-sensitive adhesive acrylics: Acronal 052, Acronal CR 516 (both BASF) and Plextol D273 (Synthomer) properties. It has been found in this study that the nano-technologically reinforced system containing of Acronal 052 and amorphous silica Ludox PX-30 showed a great enhancement in tack, peel adhesion and shear strength. In this paper we evaluate the performance of Acronal 052 modified with amorphous silica Ludox PX-30.
► We approached the problem of the competition among trees of high shade tolerances. ► European beech was a superior competitor compared to silver fir and hornbeam. ► Despite its ample regeneration, ...recruitment of hornbeam to canopy layer was limited. ► Disturbances were necessary to maintain high share of hornbeam in stands with beech. ► Success of silver fir depended on its height advantage over its neighbors.
The objective of this study was to compare the relationship between the competition intensity and performance of three shade-tolerant species: European beech, silver fir and European hornbeam. The competition intensity was calculated using two different competition indices, and the tree performance was represented by diameter growth, height growth and mortality. Our research was based on data collected in the years 1993 and 2003 in four permanent sample plots of 0.5ha each located in old-growth stands of the Roztocze National Park. The competition index, which included the height of a target tree relative to its neighbors, yielded higher correlations with the diameter and basal area increments than Hegyi’s competition index for both hornbeam and fir, but the correlation was lower for beech. The importance of the height difference between the target silver fir and its competitors was also confirmed by a strong relationship between the competition intensity and the relative crown length, indicating that the increase was strongly related to the height advantage over neighbors. In contrast, beech appears to be a successful competitor even when shorter than its neighbors. Hornbeam, which was very abundant in a stage of advanced regeneration, was notably less numerous among the shorter trees, suggesting a limited recruitment to the tree layer. The growth rate of hornbeam was much lower than beech and silver fir and was relatively weakly related to the competition intensity: even the hornbeams relatively free of competition did not respond with vigorous growth. No relationship between the indices and height increases was found for the analyzed tree species. In the case of silver fir and hornbeam, the trees that died during the study had higher values of competition indices compared to the trees that survived; the opposite tendency was found for beech, yet the number of dead beeches was very low. The results suggest that, in mixed stands, hornbeam is a weaker competitor than beech, and the most likely explanation for its high abundance in these analyzed stands is the occurrence of natural disturbances, particularly strong winds.
Key message
The disturbance of a research plot by a windstorm allowed us to study the role of the seedling bank in the regeneration processes. The released advance regeneration dominated among the ...saplings; taller individuals retained their position until the end of the study. Pioneer species occurred sporadically. Seven years after the disturbance, the windthrow was covered by a dense thicket of young trees.
Context
The dominant role played by advance regeneration in natural regeneration processes after intense wind disturbances is still a matter of dispute.
Aims
We took advantage of a windstorm in one of our research plots to study the role of the seedling bank released by the disturbance in the regeneration processes.
Methods
We collected data in 70 plots, recording the survivorship of seedlings, annual height growth, and signs of browsing. The height ranking was analyzed with Kendall’s concordance coefficient, and the height growth rates were compared using Dunn’s test.
Results
The density of seedlings increased from 6.7/m
2
in 2008 to 8.1/m
2
in 2010 and then decreased to 1.2/m
2
in 2015. The density of saplings increased continuously from 0.14 to 1.9/m
2
. The highest size differentiation occurred in sycamore maple; the individuals which were taller before the windstorm retained their position until the year 2015. The only species that was recruited mainly from germinants was European hornbeam.
Conclusion
The advance regeneration released by the windstorm played a major role in the regeneration process, while pioneer species occurred only sporadically. Seven years after the disturbance, the windthrow was already covered by a dense thicket of young trees.
Aim
Old‐growth, mesic temperate forests are often assumed to be structured by gap‐phase processes, resulting in quasi‐equilibrial long‐term dynamics. This assumption influences management focused on ...simulation of natural disturbance dynamics and is embedded in most models of forest successional dynamics. We use multi‐decade monitoring of permanent plots in old‐growth forests to assess demographic assumptions directly with respect to tree mortality rates.
Location
Sixteen sites in mesic, temperate old‐growth forests in eastern North America and Europe with multi‐decade monitoring.
Time period
Variable across sites, spanning c. 20–78 years from 1936 to 2014.
Major taxa studied
Tree species of late‐successional, cool‐temperate forests of Europe and eastern North America.
Methods
We calculated and compared the annualized mortality rates (m), with confidence intervals, by species, size class and measurement interval, for tree species of sufficient abundance.
Results
Retrospective analysis shows dynamic and diverse demographic properties across populations and sites. Stand‐scale mortality rates of 0.7–2.5%/year average higher than previous estimates for old‐growth temperate forests. Variations among species, over time and among size classes, suggest that gap‐phase models are inadequate to explain stand dynamics, implying instead that rare disturbance events of moderate severity have long‐lasting effects in old‐growth forests and that indirect anthropogenic influences affect old‐growth, unlogged forests.
Main conclusions
Multi‐decade baseline data, essential for understanding community assembly and long‐term dynamics in these “slow systems,” are rare and poorly integrated. Our analysis demonstrates the value of the few long‐term, “legacy” data sets. Results suggest that differences in life history interact with complex disturbance histories, resulting in non‐equilibrial dynamics in old‐growth temperate tree communities, and that changes in disturbance patterns through anthropogenic climate change might, therefore, be an important driver of ecosystem change.
Recent observations of tree regeneration failures following large and severe disturbances, particularly under warm and dry conditions, have raised concerns about the resilience of forest ecosystems ...and their recovery dynamics in the face of climate change. We investigated the recovery of temperate forests in Europe after large and severe disturbance events (i.e., resulting in more than 70% canopy loss in patches larger than 1 ha), with a range of one to five decades since the disturbance occurred. The study included 143 sites of different forest types and management practices that had experienced 28 disturbance events, including windthrow (132 sites), fire (six sites), and bark beetle outbreaks (five sites). We focused on assessing post‐disturbance tree density, structure, and composition as key indicators of forest resilience. We compared post‐disturbance height‐weighted densities with site‐specific pre‐disturbance densities to qualitatively assess the potential for structural and compositional recovery, overall and for dominant tree species, respectively. Additionally, we analyzed the ecological drivers of post‐windthrow tree density, such as forest management, topography, and post‐disturbance aridity, using a series of generalized additive models. The descriptive results show that European temperate forests have been resilient to past large and severe disturbances and concurrent climate conditions, albeit with lower resilience to high‐severity fire compared with other disturbance agents. Across sites and disturbance agents, the potential for structural recovery was greater than that of compositional recovery, with a large proportion of plots becoming dominated by early‐successional species after disturbance. The models showed that increasing elevation and salvage logging negatively affect post‐windthrow regeneration, particularly for late‐successional species, while pioneer species are negatively affected by increasing summer aridity. These findings provide a key baseline for assessing future recovery and resilience following the recent occurrence of widespread disturbance in the region and in anticipation of future conditions characterized by increasing heat and drought stress.
As a result of global change, forest disturbances are becoming larger and more severe, which may put forest recovery at risk, especially under a warm and dry climate. Our study shows that European temperate forests have been able to recover after large and severe disturbances and concurrent climate conditions, although with more difficulty after fires compared with other disturbance agents. The main factors negatively influencing tree regeneration after wind disturbances were increasing elevation and the removal of damaged trees from the disturbed forests.
Directions and the scope of changes in the species composition of individual layers in secondary pine communities belonging to the class Querco-Fagetea Br.-Bl. & Vlieg. 1937 (tree stand, shrubs and ...vascular plants of the herb layer) observed at two study plots over almost 40 years (from 1971 until 2009) are discussed. Both tree stands were planted and they are in the phase of spontaneous regeneration towards a potential natural community - the Carpathian beech forest Dentario glandulosae-Fagetum Oberd. 1953. Species with greater light requirements (pine Pinus sylvestris L., aspen Populus tremula L., oak Quercus robur L., ecologically alien to the potential plant community, retreat from the tree and shrub layers. The share of tree species typical of the potential community (beech Fagus sylvatica L., hornbeam Carpinus betulus L., sycamore Acer pseudoplatanus L.) - in the tree stands increases. The rate of changes is particularly high for beech, while regression symptoms are noticed for fir Abies alba Mill.: a decrease in the abundance and share of fir in both tree-stands was recorded. A decrease in the abundance and frequency of the majority of species, including species characteristic of deciduous forests (class Querco-Fagetea) and beech forests (order Fagetalia sylvaticae Pawl. 1928), and an increase in species typical of alder-ash riparian forests (alliance Alno-Ulmion Br.-Bl. & Tx. 1943) and nitrophilous communities were observed in the herb layer. Conversion treatment may reinforce the artificial character of the community because the species composition, as well as the spatial and age structure of the tree stands, can be arbitrary and therefore artificially formed during conversion (arbitrary applied size and order of regeneration clumps and areas). When anthropogenic communities are left undisturbed, processes affecting all phytocoenotic layers are activated and spontaneous forest regeneration usually begins. Therefore, tree-stand conversion used as a tool to restore natural community is not effective.
The purpose of this study was to determine the trends and rates of spontaneous changes in the structure and species composition of natural forests which are composed mostly of tree species growing at ...the limits of their natural range of distribution. We analyzed the demographic processes in populations of woody species in the years 1968-2005. The investigations were conducted in strictly protected areas in the Roztoczaiiski National Park (The Roztocze Highlands, Eastern Poland) on four 0.5-ha sample plots, established in the 1960s. These plots represented three forest communities: upland fir mixed forest Abietetum polonicum (Ap), Carpathian beech forest Dentario glandulosae-Fagetum (DgF), and pine-oaks mixed forest Querco roboris-Pinetum (QrP)). Measurements were conducted in 1968, 1978 (two sample plots only) and in two study periods (1993-1995 and 2003-2005). Measurements in the last two periods included canopy trees (DBH and height) forest regeneration (saplings, seedlings and germinants) as well as dead wood (snags and coarse woody debris). The results revealed significant and dynamic changes in the studied forests. The directions and rates of changes were different among forest communities. Silver fir (Abies alba Mill.) showed continuous decrease in all the forest associations. The highest rates of change were found in the DgF forest association. Data from the last measurement showed, that the rate of fir decline has slowed down, and in some cases even a slight increase of its share was recorded. However, the continuous decrease in abundance of the fir regeneration in all study plots suggests, that fir in the near future can be partly replaced by the broadleaved species. Among them, European beech (Fagus sylvatica L.) revealed the most dynamic species. It showed a systematic increase of it's share in stand composition, according to the number of trees and basal area in all investigated plots. The largest increase of this species was recorded in the QrP forest association. Untill 1993 hornbeam (Carpinus betulus L.) developed well in the DgF association, and it also increased in abundance in the Ap association. The last measurements confirmed large increase the number of hornbeams in the DgF association, whereas it's share in stand basal area revealed a weak downward tendency in both associations. After 1993 Norway spruce (Picea abies (L.) H. Karst.) grow only in the Ap forest communities, where its development is rather weak. The share of Norway spruce in forest composition has diminished systematically since 1968. The measurements from 2003 revealed a slight increase of the basal area of spruce and substantial decrease of its regeneration. Other tree species: Scots pine (Pinus sylvestris L.) and pedunculate oak (Quercus robur L.) in the successive measurements showed a systematic decrease of their number, basal area and share in the stand composition. There was also no natural regeneration of these species. Observed changes could be mainly attributed to natural processes of forests development (including natural disturbances) in general and to specific mechanisms of competition in forests composed of tree species growing close to the limits of their natural distribution ranges. In some cases the dynamics of researched species (hornbeam, pine and oak) can be explained as the regeneration processes of eco-systems affected previously by human activities.
Results of the research at 0.5 ha permanent study plots in two patches of Leucobryo-Pinetum community in the Roztocze National Park over a period of almost 40 years are discussed. The changes in the ...canopy species composition and their effect on the composition and arrangement of the moss layer were analysed. The share of pine in the number of trees decreased markedly over the study period. Instead, numerous species of trees, casting deep shade on the forest floor vegetation (fir, spruce, beech and oaks), encroached the tree-stands. A similar tendency of changes took place in the shrub layer: a decrease in the percentage contribution of light demanding and moderately light demanding tree species and an increase in the shade-tolerant ones. In contrast, the changes in the moss layer were mainly quantitative, but they were essentially related to the transformation in the tree stand. The considerable increase in the proportion of broadleaved species in the tree stand and understorey and, in consequence, a high cover of broadleaved litter greatly inhibited the development of terricolous bryophytes characteristic of coniferous forests.
W pracy przedyskutowano rezultaty prawie czterdziestoletnich obserwacji prowadzonych na dwóch stałych, półhektarowych powierzchniach badawczych. Zlokalizowane są one na terenie Roztoczańskiego Parku Narodowego w płatach zespołu Leucobryo-Pinetum. Analizie poddano zmiany składu gatunkowego drzewostanu oraz ich wpływ na skład i rozmieszczenie naziemnej warstwy mszystej. Udział sosny w liczbie drzew spadł bardzo wyraźnie w okresie prowadzenia obserwacji. Na jej miejsce licznie wkroczyły gatunki drzewiaste silnie ocieniające glebę, jak jodła, świerk, buk i dęby. Podobne tendencje zmian miały miejsce w warstwie krzewów: spadł udział procentowy drzewiastych gatunków światłożądnych i umiarkowanie światłożądnych, przy wzroście udziału gatunków cienioznośnych. Natomiast zmiany zaobserwowane w warstwie mszystej miały głównie charakter ilościowy, ale istotnie związany z przekształceniami w warstwie drzew. Znaczący udział gatunków liściastych w drzewostanie i podroście, a w konsekwencji wzrost ilości ściółki liściastej zalegającej na dnie lasu, bardzo wyraźnie zahamował rozwój naziemnych mchów charakterystycznych dla fitocenoz borowych.
This article is a continuation of the author’s own studies on time in the Russian neorealistic autobiographical novel. It contains an attempt at systematization of retrospections occurring in the ...works which in the fullest way represent like the indicated novel such as Arsieniev's life by I. Bunin and Gleb's Journey by B. Zaitsev. This attempt has been made at the simultaneous viewing of retrospective interpretations in the earlier Russian personal novel writing.
PDF
