Natural Regeneration Of Tree Species Research Articles

Restoring native forests from Pinus radiata plantations: natural regeneration of native tree species in response to different harvesting treatments in central Chile

The natural forests of south‐central Chile are known as world biodiversity hotspot. Due to increasing societal demands and certification commitments, a vast extension of these forests that was replaced by commercial exotic tree plantations is now to be restored. Given the magnitude of the area involved, large‐scale approaches based on natural regeneration require consideration. However, experimental evidence for this approach to restoration is lacking in different regions. We conducted a large‐scale replicated experiment to evaluate the response of natural regeneration of native tree species to different harvesting treatments (clearcut, strip‐cutting, and unharvested control) in 20‐year‐old Pinus radiata plantations. For 2 years, we monitored variations in (1) regeneration basal area (dRBA), (2) maximum sapling height (dMH), (3) frequency of free‐growing regeneration (dFGR), and (4) diversity of regenerating tree species. The harvesting treatment had significant effects on dRBA, dMH, and dFGR. The clearcuts showed the highest values of dRBA and dFGR of native species, but also, the highest dRBA of P. radiata regeneration. The strip‐cuttings showed the highest dMH of native species and the highest values of richness, Shannon, and Simpson diversity. Our results suggest that both clearcuts and strip‐cuttings facilitate natural regeneration. Although clearcuts may allow higher rates of natural regeneration establishment than strip‐cuttings, they require periodic control of P. radiata regeneration to prevent suppression of established native regeneration. Strip‐cuttings may require fewer management interventions and allow for higher initial species diversity, although with a potentially longer establishment period and higher risk of damage from residual P. radiata trees experiencing wind throw.

Structure of Ground Vegetation and Natural Regeneration of Tree Species in 12- to 15-Year-Old Bilberry Pine Forest-Clear-cut Complex of Middle Taiga Subzone.

Logging in mature stands where part of the forest is harvested in one or several cuts and part is retained (clearcutting and alternate strip cutting) results in the formation of an ecotone complex (EC), which includes a forest (F) zone, a forest edge (FE) as a transition from the forest to the clear-cut under the canopy, a clear-cut edge (CE) as a transition from the forest to the clear-cut outside of the canopy, and the clear-cut proper (C). The composition and structure of ground vegetation and natural regeneration of woody species (Pinus sylvestris L., Picea abies (L.) H. Karst., Betula sp., Populus tremula L., Sorbus aucuparia L., and Juniperus communis L.) were studied in a bilberry pine forest-clear-cut ecotone complex 12-15 years after stand removal. Specific structural features of ground vegetation and undergrowth (including tree regeneration) were observed in each of the four zones of the ecotone complex formed after logging of the mature forest. Atypical forest habitat (zone F) showed a minimum number of young regeneration of Pinus sylvestris, Picea abies, Betula sp., Populus tremula, and Sorbus aucuparia and the highest abundance of the lingonberry V. vitis-idaea L. and bilberry Vaccinium myrtillus L. with a maximum height and a maximum yield of bilberry plants. The amount of tree regeneration in the FE zone was much the same as in the F zone. The projective cover, maximum shoot height, and yield of bilberry and the maximum shoot height of lingonberry in the FE zone were significantly lower than in the F zone. The transitional zone on the clear-cut side (CE) and the clear-cut proper (C) strikingly differed from the forest (F and FE) zones of the ecotone complex by a greater number of deciduous and pine regeneration and a low abundance of dwarf shrubs. The clear-cut proper (C) differed from the CE zone by a higher abundance of grasses and forbs and an established tree regeneration layer composed of pine, birch, and aspen.

CARBON STOCK AND DYNAMICS IN NATURAL REGENERATION IN MANAGED FOREST IN THE CENTRAL AMAZON

Around 2% of the living biomass above ground is found in the natural regeneration of tree species. Despite being a relatively low value, diagnosing the lower stratum of the forest is important in the current context of climate change. The aim of this study was to evaluate the effects of forest management on the carbon stock and dynamics of natural regeneration 20 years after logging in a forest in the Central Amazon. Data collection was carried out in three Annual Production Units (APU) that received exploration in the years 1996, 1997 and 1998. Data from continuous forest inventories carried out in 41 sampling units were used, with four measurement periods: a pre-exploratory and three other post-forest exploration. The carbon stock was estimated in trees with a diameter at breast height between 5 and 15 cm and the Annual Periodic Increment in carbon (APIc) and the carbon entry and mortality rates were calculated. The carbon stock ranged from 10.80 ± 1.27 Mg ha-1 to 14.86 ± 0.81 Mg ha-1. The APIc ranged from 0.18 ± 0.03 Mg ha-1 year-1 to 0.59 ± 0.25 Mg ha-1 year-1, with an entry rate of 0.00% to 3.26% and mortality between 3.35% and 13.84%. The carbon stock and APIc were not significantly influenced by the forestry management applied to the forest, with only time as a determining factor in its dynamics. Considering natural regeneration, it is concluded that the managed forest is capable of recovering the carbon stock lost during the forest management process.

Features of natural renewal in pine-linden and larch-linden forest stands in Moscow

Problems of natural renewal of tree species (pine-linden and larch-linden stands) were studied in the territory of Forest experimental station, Moscow Timiryazev Agricultural Academy. Natural regeneration of tree species is one of the most urgent problems of forestry and forest park management in urban areas. Reforestation refers to complex natural processes that affect all components of biogeocenoses. The purpose of the research was to study natural regeneration in mixed stands in Moscow. Methods and results of field surveys of forest stands in permanent trial plots were described. The forest stands of permanent trial plots are mature and overmature, therefore at present there is a loss of large-sized pine and larch trees. Due to greater durability, larch falls off more slowly compared to pine. Further growth of pine-linden and larch-linden plantations depends on quantity and quality of undergrowth, its viability and growing conditions. In Forest experimental station, natural renewal prevails, represented mainly by the following species: maple and linden. Saplings of pine, larch, oak, and birch appear on some permanent test plots, but soon die due to unfavorable conditions. Oak undergrowth is also unreliable due to powdery mildew infection. The greatest loss of growth occurs in unfavorable growing conditions due to increased recreational loads.

The natural regeneration characteristics in oak forests following different methods of clearcutting

An important task for Ukrainian foresters is to adapt forests to climate change and ensure sustainable forest management. One key measure for achieving this goal is the natural regeneration of tree species, which contributes to the biological resilience of forest stands. The purpose of this study is to assess the impact of different methods of main use fellings on the natural regeneration process of tree species in oak forests. The study was conducted within the territory of the Stradch Forestry Educational and Production Complex of the Ukrainian National Forestry University. Data on the quantity and height of oak seedlings and saplings, and other tree species, were collected through observation after various methods of main use fellings were applied in oak forests. An analytical method was applied to detect patterns and differences in quantitative and qualitative indicators of young trees of different species in sample plots. Statistical data analysis was employed to establish relationships and draw conclusions based on numerical data. Different success rates of natural regeneration of tree species were identified on plots subjected to various methods of main use fellings. Positive dynamics in the quantity of seedlings and saplings were observed due to first intervention of the uniform shelterwood felling, ranging from unsatisfactory to good levels. It is recognised that the distribution of seedlings and saplings of all tree species was uneven across the area. Hornbeam has the highest frequency of occurrence – 75.6%. Tree species like Scots pine, European birch, and goat willow exhibited occurrence frequencies ranging from 30.8% to 39.7%. In general, in all the studied areas, the undergrowth of tree species was dominated by a small fraction up to 20 cm of height. To ensure the prevalence of pedunculate oak in naturally formed young stands, silvicultural care for its saplings is necessary on all plots. The obtained results provide a basis for developing scientifically grounded forest management measures aimed at increasing the quantity and quality of valuable tree species’ saplings, particularly pedunculate oak

Structure of the Ground Vegetation and Natural Regeneration of Tree Species in a 12–15-Year-Old Bilberry Pine Forest–Clear-Cut Ecotone Complex in the Middle Taiga Subzone

Abstract—Logging in mature stands, where part of the forest is harvested in one or several cuts and part is retained (clear-cutting and alternate strip cutting) results in the formation of an ecotone complex: forest (F), transition from forest to clear-cut under the canopy (forest edge – FE), transition from forest to clear-cut outside of the canopy (clear-cut edge – CE), and the clear-cut itself (C). Strips 8 m wide on each side of the mature forest/clear-cut site border form the transitional zone. We studied the ground vegetation composition and structure, and the natural regeneration of woody species (Pinus sylvestris L., Picea abies (L.) H. Karst., Betula sp., Populus tremula L., Sorbus aucuparia L., Juniperus communis L.) in the bilberry pine forest – clear-cut ecotone complex 12–15 years after the stand removal. The studies demonstrate that each of the four zones of the ecotone complex formed after logging of the mature forest has its own structural features of ground vegetation and undergrowth (including tree regeneration). The typical forest (F) habitat is characterized by the minimum number of young regeneration of Pinus sylvestris, Picea abies, Betula sp., Populus tremula, and Sorbus aucuparia and, on the contrary, by the highest abundance of lingonberry V. vitis-idaea L. and bilberry Vaccinium myrtillus L., and the maximum height of bilberry plants and their yield. The amount of tree regeneration in the FE is almost the same as in the F zone. The projective cover, maximum shoot height and yield of bilberry, and maximum shoot height of lingonberry in the FE zone are reliably lower than in the F zone. The transitional zone on the clear-cut side (CE) and the clear-cut itself (C) are distinguished from the forest sections of the ecotone complex (F and FE zones) by a greater number of deciduous and pine regeneration and the low abundance of dwarf shrubs. The clear-cut itself (C) differs from the CE by the higher abundance of grasses and forbs and an established tree regeneration layer composed of pine, birch, and aspen.

Stable isotope composition in tree rings of Fagus sylvatica L. saplings reflects environmental variation induced by silviculture and microsite factors

Natural regeneration of tree species is sensitive to silvicultural interventions. This study aimed to investigate the effects of different cutting intensities and local topographic and soil conditions on the composition of stable carbon (δ13C) and oxygen (δ18O) isotopes in wood of young beech (Fagus sylvatica L.) trees. Beech saplings in the regeneration layer were sampled in summer 2018 at three study sites in Dinaric fir-beech forests in the karst area of Slovenia. Three different cutting intensities were performed in 2012: i) no cutting (control), ii) 50% cutting of the stand’s growing stock creating thinned stands, and iii) 100% cutting of the stand’s growing stock creating 0.4 ha canopy gaps. We show that δ13C increased along the gradient of cutting intensity. On average, δ13C values in the tree rings were ∼ 2‰ increased in trees from canopy gaps than from closed control stands. Furthermore, δ13C was higher on south-facing slopes characterized by higher air temperatures and lower relative humidity compared to north-facing slopes of karst sinkholes. Additionally, the results suggest a dependence of δ18O on interannual and cross-site climatic variations, particularly in the case of summer precipitation amount. δ18O also responded to soil depth, with beech individuals exhibiting lower values on deeper soils, presumably characterized by higher soil water availability compared to shallow soils. The results are discussed in the context of future climate change, as many beech-dominated forests on karst terrain in the Dinaric Mountains are particularly affected by climate warming and drying due to prolonged and reoccurring summer droughts, intensified large-scale disturbances, and often shallow soils with low water storage capacity.

SURVIVAL AND NATURAL REGENERATION OF FOREST ESSENCES CULTIVATED IN ALTERED AREAS THIRTY-FIVE YEARS AFTER PLANTING

The evaluation of the survival and natural regeneration of tree species in a 35-year-old plantation was carried out to identify the species established in the area, aiming at their recommendation in forest restoration plantations in the State of Acre. In the 1980s, 138 forest species were planted in two experimental units (EU), of 1.38 ha each, in the Zoobotanical Park (ZP) of the Federal University of Acre, Rio Branco campus. The main activities carried out in the area, prior to planting, were agriculture and cattle raising. Survival status was measured through a census of all individuals planted at the time, who were still alive. In addition, all regenerating individuals from planted species were surveyed in the effective planting area of the experimental units. At the time of evaluation, living individuals of 41 and 46 species were found in experimental units 1 (EU-1) and 2 (EU-2), respectively. The species Syagrus sancona, Talisia esculenta, Acacia polyphylla, Couepia bracteosa, Mangifera indica, Syzygium cumini and Copaifera multijuga showed survival rates above 90% in at least one of the experimental units. Only Syagrus sancona and Handroanthus serratifolius presented high survival rates in both experimental. Regenerating individuals of the species Aspidosperma vargasii, Couepia bracteosa, Euterpe precatoria, Handroanthus serratifolius, Oenocarpus mapora, Onychopetalum periquino and Stryphnodendron pulcherrimum were found in the two EU.

Естественное возобновление в смешанных разновозрастных древостоях на урбанизированных территориях Москвы

The effectiveness of forests therapeutic impact is based on its species’ and age structure, silvicultural features, biological productivity, regenerative ability, forest management intensity and its methods. The processes of natural regeneration of a forest stand and its growth are the main factors of the forest’s ecosystem proper functioning and a disruption in these processes can lead to a transformation of the whole biocenosis, a change of a typological community. Technogenic pollution is a huge stress factor for trees, and its impact is especially evident in regions with a high concentration of industrial facilities, namely, in Moscow city. One of the most serious consequences of technogenic pollution is the deterioration of long-established forests, which subsequently may reduce its ability to adapt to ever-changing environmental conditions and its protective functions. The article discusses issues regarding the natural regeneration of forests on urbanized territories of Moscow on the example of the Forest experimental station of the Russian State Agrarian University - Moscow Timiryazev Agricultural Academy. The natural regeneration of tree species is one of the most relevant issues of forest and park management. The aim of this project is to estimate natural regeneration in mixed forest stands of urbanized areas, to provide recommendations on the organization of forest regeneration measures in urban environments. The article provides methods and results of field research and recommendations on reforestation measures under these conditions. The research of the cenobiotic connections and the undergrowth of different species with key elements of grass cover in its habitat, will allow a more positive dynamics in the use of natural resources, which will contribute to preservation and restoration of forests.

Formation of phytocenoses on lands disturbed by oil extraction in the Udmurt Republic

The Udmurt Republic is a region in which the oil extraction industry occupies a leading place in the economy along with metallurgy and mechanical engineering. Oil exploration work has been carried out here since the 40s of the XX century. Today, there are over 120 oil fields in the territory of Udmurtia. Every year, geological exploration of the subsoil contributes to the identification of new territories in which work on hydrocarbon raw materials’ extraction is planned in the future. A significant part of these territories is located on the lands of the forest fund. To characterize the dynamics of environmental conditions and predict measures for the rational formation of post-technogenic territories, it is important to study the overgrowing processes of disturbed lands. The study of technogenic landscapes makes it possible to assess the disturbance degree of the vegetation, living ground cover. The article shows the features of phytocenoses formation, their species diversity in the conditions of oil production on the territory of the Udmurt Republic. The growth and development of living ground cover, natural regeneration of tree species depending on the age and degree of pollution have been investigated. It was found that with an increase in the technogenesis age, an increase in the proportion of forest species in phytocenoses takes place. Therefore, when forecasting for a longer period, one can expect the formation of plant communities mainly from forest tree and shrub species.

Tree species composition and height structure of undergrowth in fresh hornbeam-oak-pine forest on relatively rich soils of the Ukrainian Roztochia

The fresh hornbeam-oak-pine forest on relatively rich soils of the Ukrainian Roztochia is characterized by a good natural regeneration of tree species, both under the forest canopy after the first irregular shelterwood cutting, and on two clear cut areas. After the first irregular shelterwood cutting, the total amount of self-seeding and undergrowth changes from unsatisfactory (10.480 pieces/ha) at the beginning of the 2020 vegetation season to good (41.528 pieces/ha) at the end of the 2020 growing season. A year later, its number has not changed and 42.693 individuals/ha were counted. However, the share of pedunculate oak in the total number of undergrowth here is only 1.7%. Natural regeneration of all tree species under the forest canopy is characterized by an uneven distribution in the area. Hornbeam has the highest incidence rate - 75.6%. Species such as Scots pine, hanging birch and goat willow have a frequency of 30.8 to 39.7%. Other tree species are much less common, including pedunculate oak (abundance from 1.3% to 12.8%). On clear cut areas the total amount of self-seeding and undergrowth varies from 175.6-275.3 units/ha at the beginning of the vegetation period of 2020 to 299.4 thousand pieces/ha at the end of that vegetation period, and a year later, in autumn 2021 it reached 461.2 thousand pieces/ha. Hornbeam also had the highest abundance rate - 97.3-98.1%, followed by pedunculate oak (43.5-77.3%), birch (42.6-52.7%) and pine (29.6-34.0%). Other tree species, such as lime, willow, sycamore, beech, elm, aspen, and others, had a frequency of 0.7 to 20%. In general, in all the studied areas, the composition of self-seeding and undergrowth was dominated by a small fraction up to 20 cm in height. To ensure the advantage of pedunculate oak in the naturally formed young stands in all areas it is necessary to carry out silvicultural treatments such as cleaning or precommercial thinning.

Natural Advance Regeneration of Native Tree Species in Pinus radiata Plantations of South-Central Chile Suggests Potential for a Passive Restoration Approach

Restoration of natural forests previously replaced by plantations is a widespread challenge for forestry in Chile and elsewhere. However, there is little documented evidence for successful restoration, either through active or passive approaches. In this study, we aimed at (1) determining the potential for passive restoration in first-rotation Pinus radiata plantations through natural regeneration of native tree species and (2) identifying drivers of this advance regeneration. Across different regions in south-central Chile, we established nearly 260 plots to assess regeneration and environmental conditions along 26 transects running from plantations into adjacent natural forests. The regeneration was exclusively composed by native species, except for 7 individuals of P. radiata. Mean density and diversity of seedlings were significantly higher in natural forests than in plantations, but this was not the case for sapling density, and no differences in sapling diversity were supported. Additionally, significant differences in regeneration composition between plantations and natural forests were found only at two of the eight study sites. Compared to climatic and soil chemical variables, which varied mostly at regional scales, local environmental conditions showed little influence on regeneration, possibly due to the structural homogeneity of plantations. Yet, the significantly higher basal area, litter thickness and gap fraction of plantations compared to natural forests suggest that these factors may explain differences at the seedling stage. Our study indicates that the use of appropriate harvesting methods that maintain advance regeneration may facilitate the transition from plantations to native forests through passive restoration. The use this approach should be further investigated through analyzing regeneration’s response to different forms of plantation harvesting.

Effects of Wildfire and the Presence of the Invasive Paulownia tomentosa on the Regeneration of Native Tree Species in North-Central Appalachia

A wildfire occurred in Shawnee State Forest located in southern Ohio that consumed 1215 hectares. Based on earlier forest inventories it was known that paulownia (Paulownia tomentosa), a non-native invasive tree species, occurred in the forest. The objective of this study was to determine if paulownia heavily colonized areas two years after the fire where the burn occurred, and if its presence had a negative impact on the regeneration (<137 cm height) of native species—red and white oaks (Quercus sp.), red maple (Acer rubrum), and yellow-poplar (Liriodendron tulipifera). Two years after the fire, paulownia had invaded the burned areas but not at significantly higher densities than occurred in the unburned areas. Fire significantly reduced the number of regenerating stems of white oak and red maple two years after the fire, whereas the number of regenerating stems of red oak increased slightly and that of yellow-poplar increased significantly. In areas where paulownia occurred that experienced wildfire, all species studied displayed a reduction in the number of regenerating stems compared to paulownia’s absence in the burn areas. Where paulownia occurred in areas not affected by the wildfire, all the native species studied displayed a reduction in the number of regenerating stems. The average heights of red oak, white oak, and red maple were significantly taller when growing in areas affected by the wildfire due to a more open canopy. However, there was no significant change in the average heights of yellow-poplar. The presence of paulownia in both the burned and unburned areas reduced the number of regenerating stems of the native species studied.

Woody Species Composition, Vegetation Structure, and Regeneration Status of Majang Forest Biosphere Reserves in Southwestern Ethiopia

The aim of this study was to analyse the species composition, structures, and regeneration of woody plant species and the impacts of site factors on the natural regeneration of tree species in four study sites of MFBR. The vegetation data were collected systematically in 140 plots with the size of 400 m2 for trees; 25 m2 for seedlings, saplings, shrubs, and lianas; and 1 m2 for herbs. Individual tree and shrub DBH ≥ 5 cm were measured and counted. The diameter at breast height (DBH), frequency, basal area, importance value index (IVI), and density were used for vegetation structure description and regeneration. A total of 158 plant species belonging to 115 genera, 56 families, and 80 species (51%) trees, 26 (16%) shrubs, 19 (12%) herbs, and 33 (21%) lianas were identified and recorded. The most dominant families were Euphorbiaceae, Rubiaceae, and Moraceae, each represented by 13 species (7.4%), 12 species (6.8%), and 10 species (5.7%), respectively. The tree densities varied from 1232 to 1478 stem ha−1, sapling density 176.8 to 708.7 stem ha−1, and seedling density 534.7 to 1657.5 stem ha−1, with an average basal area of 63.6 m2 in the study sites. Dracaena afromontana was the most frequent woody species in the MFBR occurring in 90% followed by Celtis zenkeri (65%) and Pouteria altissima (62.5%). The regeneration status of all the woody plant species was categorised as “not regenerate” (9.6%), “poor” (30.7%), “fair” (59.5%), and “good” (10.8%) in all sites. The correlation result between natural regeneration and site factors revealed both positive and negative relationships. However, the main threat to the biosphere reserve is illegal logging for different purposes. Therefore, awareness creation on sustainable forest management, utilisation, conservation of priority species, and livelihood diversification to the local community and encouraging community and private woodlot plantation in the transitional zone of biosphere reserves are recommended.

Effects of prescribed grazing by goats on non‐native invasive shrubs and native plant species in a mixed‐hardwood forest

Invasion of non‐native shrubs comprises a serious economic and ecological problem in North American forests. Prescribed grazing by goats may offer an effective alternative to traditional methods of control, but has received little study in forest settings. In a 5‐year field experiment, we varied the stocking of goats and number of grazing periods to determine effects of prescribed grazing on both invasive shrubs and native plant species. Specifically, we examined how varied stocking levels and grazing periods affect: (1) the cover and height of invasive shrub and native woody species (2) the cover and diversity of herbaceous species, and (3) the density of native tree seedlings. Data were analyzed with linear mixed‐effects models. We found that prescribed grazing by goats significantly reduced the cover and height of invasive shrubs, regardless of goat stocking or duration. Generally, the greatest reductions in invasive shrub cover occurred in treatments with two grazing periods, regardless of goat stocking. While we observed mostly neutral or positive effects on the herbaceous layer, all grazing treatments reduced the cover and height of native understory woody species. While changes were not significant, we observed a general decline in the aggregate height of native tree species regeneration. Our results suggest that prescribed grazing by goats provides an effective and environmentally friendly treatment for heavy invasions of non‐native shrubs such as Rosa multiflora, but grazing needs to be followed by focused mechanical or chemical treatments to maintain control while allowing the regeneration of native tree species.

The composition and diversity of natural regeneration of tree species in gaps under different intensities of forest disturbance

The positive ecological interaction between gap formation and natural regeneration has been examined but little research has been carried out on the effects of gaps on natural regeneration in forests under different intensities of disturbance. This study evaluates the composition, diversity, regeneration density and abundance of natural regeneration of tree species in gaps in undisturbed, intermittently disturbed, and disturbed forest sites. Bia Tano Forest Reserve in Ghana was the study area and three gaps each were selected in the three forest site categories. Ten circular subsampling areas of 1 m2 were delineated at 2 m spacing along north, south, east, and west transects within individual gaps. Data on natural regeneration < 350 cm height were gathered. The results show that the intensity of disturbance was disproportional to gap size. Species diversity differed significantly between undisturbed and disturbed sites and, also between intermittently disturbed and disturbed sites for Simpson’s (1-D), Equitability (J), and Berger–Parker (B–P) indices. However, there was no significant difference among forest sites for Shannon diversity (H) and Margalef richness (MI) indices. Tree species composition on the sites differed. Regeneration density on the disturbed site was significantly higher than on the two other sites. Greater abundance and density of shade-dependent species on all sites identified them as opportunistic replacements of gap-dependent pioneers. Pioneer species giving way to shade tolerant species is a natural process, thus make them worst variant in gap regeneration.

Effects of Man-powered Scarification and a Rhizome Cutting Treatment on Natural Regeneration of Tree Species in Dwarf-bamboo Grassland

Effects of Man-powered Scarification and a Rhizome Cutting Treatment on Natural Regeneration of Tree Species in Dwarf-bamboo Grassland

Restoring native forests from Pinus radiata plantations: Effects of different harvesting treatments on the performance of planted seedlings of temperate tree species in central Chile

Extensive areas of native vegetation have been cleared to establish commercial exotic tree plantations in south-central Chile, a region known as a world biodiversity hotspot. Despite increasing societal demands to restore native forests in parts of the landscape, documented experiences for this form of restoration are lacking. We conducted a landscape-replicated experiment to test the influence of different harvesting treatments (clearcut, strip-cutting and unharvested control) on the early establishment of native tree species in 20-year-old Pinus radiata plantations. Group plantings of shade-intolerant (Nothofagus dombeyi; Nothofagus obliqua), semi-tolerant (Nothofagus alpina; Laurelia sempervirens) and shade–tolerant species (Aextoxicon punctatum; Cryptocarya alba) were established across the treatments, and seedling performance and water status were monitored during the first two growing seasons. Mean survival was significantly higher in the strip-cuttings (77%) and control (70%) than in the clearcuts (38%), while mean height and root collar diameter growth were significantly higher in the strip-cuttings (16 cm year−1; 0.2 cm year−1) and clearcuts (16 cm year−1; 0.2 cm year−1) than in the control (5 cm year−1; 0.1 cm year−1). Shade-intolerant and semi-tolerant species showed the highest growth responses to openings. Leaf water potential was significantly higher in seedlings in the strip-cuttings than those in the control and clearcuts, and stomatal conductance was significantly higher in the strip-cuttings and clearcuts than in the control. Higher seedling performances and lower water stress in the strip-cutting treatment suggest that partial canopy removal is a suitable method for artificial regeneration of native tree species with different shade tolerances for native forest restoration from P. radiata plantations.

More widespread alien tree species do not have larger impacts on regeneration of native tree species in a tropical forest reserve.

There is insufficient information regarding the factors affecting the environmental impacts of alien species. In particular, little is known about whether there is any relationship between the invasiveness (establishment and spread) of an introduced species and its per capita impact. We experimentally assessed the relationship between the extent of spread of up to 29 alien plant species and their impact on recruitment of native tree species in Amani Botanical Garden, Tanzania. We also studied the effects of allelochemicals of selected alien on native plant species to assess potential mechanisms of impact. We found no relationship between the extent of spread of an alien tree species and their impact on seed germination, seedling survival, and seedling communities of native trees in their understory, and no indication that allelochemicals consistently explain their effects on recruitment of the studied species. These results suggest that extent of spread cannot be used as a proxy for impact. Hence, managers should continue assessing both the spread and the impact of alien species when prioritizing alien species for management.

Prospect of natural regeneration of tree species in Hazarikhil Wildlife Sanctuary of Chattogram, Bangladesh

Natural regeneration of tree species is the major means of understanding the restoration potentiality of a secondary forest. Natural regeneration of a forest is a tool for measuring the health of the forest ecosystem. Natural regeneration status of tree species in Hazarikhil Wildlife Sanctuary (HWS) in Chittagong North Forest Division, Bangladesh was assessed laying 75 systematic quadrats of 4m×4m in size. A total of 90 regenerating tree species belonging to 34 families was identified from the HWS. Euphorbiaceae family possessed maximum regenerating tree species (14 species) followed by Mimosaceae (7), Lauraceae and Meliaceae (6 species each), and Moraceae (5 species). The overall seedling density was 7,083 per ha where Ficus hispida showed the highest number of seedlings (792 per ha) followed by Quercus sp. (475), Ficus religiosa (408), Lithocarpus elegans (375) and Lepisanthes rubiginosa (367). The number of Ficus hispida seedlings per ha was higher due to high coppicing ability. Lepisanthes rubiginosa attained maximum IVI (27.59) followed by Ficus hispida (21.18) and Quercus oxyodon (13.32). The seedlings of Aegle marmelos, Lithocarpus sp., Flacourtia jangomas, Albizia odoratissima, Acronychia padunculata, Chaetocarpus castanicarpus, Maesa paniculata, Crypteronia paniculata, Streblus asper and Mussaenda roxburghii were also found common in the study area. The findings will create baseline information of regenerating tree species, composition, diversity and population structure which can be used for monitoring future changes as well as taking policy decisions for the management of this Wildlife Sanctuary.&#x0D; J. Biodivers. Conserv. Bioresour. Manag. 2019, 5(2): 1-12