Special Issue "The Forest Renewal Issue: New Problems and Findings in the Establishment of Tree Regeneration"

A special issue of Forests (ISSN 1999-4907). This special issue belongs to the section "Forest Ecology and Management".

Deadline for manuscript submissions: closed (31 December 2018).

Special Issue Editors

Prof. Dr. Emanuele Lingua
Website
Guest Editor
Department of Land, Environment, Agriculture and Forestry (TESAF), University of Padova Viale dell’Università 16, 35020, Legnaro(PD), Italy
Interests: Forest ecology and management; Disturbance ecology; Post-disturbance vegetation dynamics; Spatial analysis; LiDAR data and UAV applications in forestry
Special Issues and Collections in MDPI journals
Prof. Dr. Raffaella Marzano
Website
Guest Editor
Department of Agricultural, Forest and Food Sciences (DISAFA), University of Torino, L.go Paolo Braccini 2, 10095, Grugliasco (TO), Italy

Special Issue Information

Dear Colleagues,

Tree regeneration is key to sustainable forestry. Dealing with stand renewal has always been of crucial relevance in forest management since it is the first stage in all silvicultural systems, actually named after their respective regeneration methods. Not only in regular forest management, the regeneration issue is also very important in post-disturbance restoration dynamics and management and whenever forest ecosystem rehabilitation is involved.

Defining the most suitable species, type of material (i.e. bare root or container seedlings, seeds, cuttings), timing and planting arrangement in afforestation, or understanding the processes and mechanisms that influence natural tree seedlings establishment (e.g. seed dispersal, predation, microsite characteristics) and survivorships (e.g. herbivory, competition and facilitation) are among the most actively investigated topics in forestry.

New approaches and investigations are still needed to counteract old and new problems (e.g. ungulate pressure, climate change) related to this issue and the possible consequences of their interactions. Future forest generations rely on our ability to respond promptly to this challenge, finding effective solutions and practices to adapt to continuously changing environments.

We encourage studies from all fields, including experimental and multidisciplinary investigations, focusing on tree regeneration, both natural and artificial, to contribute to this Special Issue in order to promote knowledge on regeneration processes and dynamics, and to implement sustainable forest management, enhancing ecosystem resilience.

Prof. Dr. Emanuele Lingua
Prof. Dr. Raffaella Marzano
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Forests is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Regeneration structure
  • Forest restoration
  • Forest establishment
  • Early stand dynamics
  • Forest management
  • Resilience
  • Land use policies
  • Seed dispersal and predation
  • Herbivory

Published Papers (7 papers)

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Research

Open AccessArticle
Post-Fire Management Impact on Natural Forest Regeneration through Altered Microsite Conditions
Forests 2019, 10(11), 1014; https://doi.org/10.3390/f10111014 - 13 Nov 2019
Cited by 2
Abstract
High severity stand-replacing wildfires can deeply affect forest ecosystems whose composition includes plant species lacking fire-related traits and specific adaptations. Land managers and policymakers need to be aware of the importance of properly managing these ecosystems, adopting post-disturbance interventions designed to reach management [...] Read more.
High severity stand-replacing wildfires can deeply affect forest ecosystems whose composition includes plant species lacking fire-related traits and specific adaptations. Land managers and policymakers need to be aware of the importance of properly managing these ecosystems, adopting post-disturbance interventions designed to reach management goals, and restoring the required ecosystem services. Recent research frequently found that post-fire salvage logging negatively affects natural regeneration dynamics, thereby altering successional pathways due to a detrimental interaction with the preceding disturbance. In this study, we compared the effects of salvage logging and other post-disturbance interventions (adopting different deadwood management strategies) to test their impact on microclimatic conditions, which potentially affect tree regeneration establishment and survival. After one of the largest and most severe wildfires in the Western Alps that affected stand-replacing behavior (100% tree mortality), a mountain forest dominated by Pinus sylvestris L., three post-fire interventions were adopted (SL-Salvage Logging, logging of all snags; CR-Cut and Release, cutting snags and releasing all deadwood on the ground; NI-No Intervention, all snags left standing). The differences among interventions concerning microclimatic conditions (albedo, surface roughness, solar radiation, soil moisture, soil temperature) were analyzed at different spatial scales (site, microsite). The management interventions influenced the presence and density of safe sites for regeneration. Salvage logging contributed to the harsh post-fire microsite environment by increasing soil temperature and reducing soil moisture. The presence of deadwood, instead, played a facilitative role in ameliorating microclimatic conditions for seedlings. The CR intervention had the highest soil moisture and the lowest soil temperature, which could be crucial for seedling survival in the first post-fire years. Due to its negative impact on microclimatic conditions affecting the availability of preferential microsites for regeneration recruitment, salvage logging should not be considered as the only intervention to be applied in post-fire environments. In the absence of threats or hazards requiring specific management actions (e.g., public safety, physical hazards for facilities), in the investigated ecosystems, no intervention, leaving all deadwood on site, could result in better microclimatic conditions for seedling establishment. A preferred strategy to speed-up natural processes and further increase safe sites for regeneration could be felling standing dead trees whilst releasing deadwood (at least partially) on the ground. Full article
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Open AccessArticle
The Role of Woodlots in Forest Regeneration outside Protected Areas: Lessons from Tanzania
Forests 2019, 10(8), 621; https://doi.org/10.3390/f10080621 - 25 Jul 2019
Cited by 2
Abstract
Promoting forest regeneration outside protected forests is an urgent challenge in densely settled, biodiverse areas like the East African Rift. Regenerating forests entails managing complex processes of ecological recovery as well as understanding the needs and motivations of local land users. Here, we [...] Read more.
Promoting forest regeneration outside protected forests is an urgent challenge in densely settled, biodiverse areas like the East African Rift. Regenerating forests entails managing complex processes of ecological recovery as well as understanding the needs and motivations of local land users. Here, we evaluate pathways for attaining native tree regeneration across variable site conditions. We investigate two common strategies for attaining native tree regeneration—setting aside land for forest regeneration (‘Protect and Wait’) and native tree planting (‘Native Tree Planting’)—and a possible third, smallholder exotic tree-planting (‘Woodlots’). We measured native seedling regeneration patterns for each of the three strategies, all underway at a single site in Southern Tanzania. We also used historical aerial photograph analysis and interviews with smallholder farmers to understand past and present land use. Our results show that forest regeneration has been arrested for decades on land under ‘Protect and Wait’, and seedling survival appears to be limited under ‘Native Tree Planting’. In contrast, we found saplings of 28 native species growing spontaneously within pine, eucalyptus, and cypress woodlots planted <400 m from native forest boundaries. Interviews showed that the citizens most likely to plant woodlots near the protected forest were those who owned additional land parcels elsewhere. Some saw woodlots as a means to avoid losing crops to wildlife at the forest edge. Our findings suggest: (1) Simply setting aside land for regeneration does not guarantee forest regrowth, even if it is adjacent to natural forest, (2) native seedlings will be more likely to survive if planted near shade trees, and (3) smallholders’ woodlots could hasten native tree regeneration at forest park edges if farmers have incentives to protect the native tree seedlings in their woodlots and they can find land elsewhere to plant food crops. Full article
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Open AccessArticle
Within-Site Variation in Seedling Survival in Norway Spruce Plantations
Forests 2019, 10(2), 181; https://doi.org/10.3390/f10020181 - 19 Feb 2019
Cited by 2
Abstract
Seedling survival was evaluated from inventories of a large set of Norway spruce plantations in privately owned forests in southern Sweden. The inventories were conducted at the time of planting and a subset was re-inventoried three years later. This enabled comparison of regeneration [...] Read more.
Seedling survival was evaluated from inventories of a large set of Norway spruce plantations in privately owned forests in southern Sweden. The inventories were conducted at the time of planting and a subset was re-inventoried three years later. This enabled comparison of regeneration success after soil scarification and planting. The acquired data enabled evaluation of annual and climatic variation of seedling mortality since inventories were made on newly established clearcuts distributed spatially throughout three regions in southern Sweden and repeated in five consecutive years. Within-site variation was also captured via the use of a large number of sample plots on each clearcut. To do so, thirty sample plots were established within weeks of planting on 150 clearcuts. Small- and large-scale site and management variables were recorded as well as the numbers of suitable planting spots and planted seedlings. Three years later, 60 of the initially surveyed clearcuts were revisited and the numbers of both planted and naturally regenerated seedlings counted. On average, 2000 seedlings ha−1 were planted and 1500 seedlings ha−1 had survived after three years. However, there was high variation, and in 42% of the revisited sample plots no mortality was recorded. Important variables for seedling survival identified by linear regression analysis included the number of suitable planting spots, soil moisture conditions and annual variation in available soil water. Full article
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Open AccessArticle
Plant Attributes that Drive Dispersal and Establishment Limitation in Tropical Agricultural Landscapes
Forests 2018, 9(10), 620; https://doi.org/10.3390/f9100620 - 10 Oct 2018
Cited by 3
Abstract
Factors that influence tropical-forest regeneration have been of interest across the tropics. We tested the degree of dispersal and establishment limitation of pioneer and non-pioneer tree species with different dispersal modes and seed sizes, using data on both seed fall and seedling establishment [...] Read more.
Factors that influence tropical-forest regeneration have been of interest across the tropics. We tested the degree of dispersal and establishment limitation of pioneer and non-pioneer tree species with different dispersal modes and seed sizes, using data on both seed fall and seedling establishment in primary forest, secondary forest, and pasture excluded from livestock. The study took place in a lowland tropical rain forest in southeastern Mexico. To calculate dispersal and establishment limitation, we used a density-weighted index that considers: (1) whether a seed or seedling of a given species has arrived in the sample area; and (2) the fraction of seeds or seedlings contributed by a given species relative to the total number of seeds or seedlings arriving at a sampling station. Dispersal limitation of non-pioneer species and animal-dispersed species decreased with succession. The secondary forest had less dispersal limitation for wind-dispersed pioneers than pasture, resulting in a dense aggregation of species with seeds dispersed by wind. Overall, establishment limitation differed between animal-dispersed and wind-dispersed species in the primary forest, and was negatively correlated with seed size. The low capacity of most species to arrive, germinate, and establish as seedlings in pastures slows succession back to forest. To overcome barriers to natural succession in pastures, transplanting seedlings of non-pioneer species is suggested because most of them show high dispersal and establishment limitation. Full article
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Open AccessArticle
Integrating Density into Dispersal and Establishment Limitation Equations in Tropical Forests
Forests 2018, 9(9), 570; https://doi.org/10.3390/f9090570 - 15 Sep 2018
Cited by 2
Abstract
Plant recruitment in tropical forests reflects the chance that seeds arrive at a site resulting in seedling establishment. To inform tropical forest restoration, we ask how seed and seedling densities differentially affect dispersal and establishment limitation in successional habitats in a tropical agricultural [...] Read more.
Plant recruitment in tropical forests reflects the chance that seeds arrive at a site resulting in seedling establishment. To inform tropical forest restoration, we ask how seed and seedling densities differentially affect dispersal and establishment limitation in successional habitats in a tropical agricultural landscape. Methods: In Los Tuxtlas Biosphere Reserve, we calculated indices of dispersal and establishment limitation using data on seed rain and seedling establishment in old-growth forest, secondary forest, and fenced pasture. We present an index that considers variations in dispersal- and establishment-limitation including density-weighted calculations. Results: There were greater dispersal and establishment limitations in pasture than in forests. Substantial differences in both dispersal and establishment limitation occurred among the 33 species for which seed and seedling data were available. Only 5% of all species had mid to low limitation in both dispersal and establishment. In contrast, 60% of all species showed high dispersal and establishment limitation. Plant recruitment in pastures is impeded by low seed arrival, given that 77% of the recorded species showed extremely high dispersal limitation (>90%). Conclusions: The low capacity of most species to arrive, seeds to germinate and seedlings to establish in pastures slow down succession back to forest. Full article
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Open AccessArticle
Building Resistance and Resilience: Regeneration Should Not be Left to Chance
Forests 2018, 9(5), 270; https://doi.org/10.3390/f9050270 - 16 May 2018
Cited by 4
Abstract
Contemporary forest planning has tasked managers with developing goals associated with resistance and resilience. In practice, silviculturists use forest structure and tree species composition to characterize goals and desired future conditions, write prescriptions, and monitor outcomes associated with resistance and resilience. Although rarely [...] Read more.
Contemporary forest planning has tasked managers with developing goals associated with resistance and resilience. In practice, silviculturists use forest structure and tree species composition to characterize goals and desired future conditions, write prescriptions, and monitor outcomes associated with resistance and resilience. Although rarely discussed in the exploding literature relating to forest resistance and resilience, silvicultural regeneration methods are important and underutilized tools to meet these goals. We propose alternative silvicultural systems for building resistance and resilience to two common large-scale bark beetle disturbance agents in the Intermountain West, United States: mountain pine beetle (Dendroctonus ponderosae Hopkins) and spruce beetle (Dendroctonus rufipennis Kirby). Shelterwood, and shelterwood-with-reserves, silvicultural systems provide the desirable facilitative characteristics of a mature overstory on maintaining advance reproduction and the establishment of new cohorts of desirable tree species. These also allow the timely regeneration of large treatment areas necessary to rapidly promote desired future conditions in the face of inevitable disturbance. When implemented proactively, regeneration treatments allow silviculturists to take advantage of currently existing vegetation for the creation of age class and tree species diversity. In general, these examples illustrate the need for proactive planning for regeneration in response to any disturbance where desired future conditions include particular species. Furthermore, we argue that timely silvicultural interventions that focus on regenerating trees may be a key factor in achieving goals relating to resilience to specific disturbance types. Waiting until after the disturbance has occurred could result in the lost opportunity to establish desired species composition or stand structure—and may well result in a considerable restoration challenge. Full article
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Open AccessArticle
Ecological Factors Influencing Norway Spruce Regeneration on Nurse Logs in a Subalpine Virgin Forest
Forests 2018, 9(3), 120; https://doi.org/10.3390/f9030120 - 05 Mar 2018
Cited by 3
Abstract
Regeneration of Picea abies in high-elevation mountain forests often depends on the presence of coarse woody debris (CWD), as logs provide sites with more favorable conditions for spruce regeneration compared to the forest floor. However, there is little quantitative knowledge on the factors [...] Read more.
Regeneration of Picea abies in high-elevation mountain forests often depends on the presence of coarse woody debris (CWD), as logs provide sites with more favorable conditions for spruce regeneration compared to the forest floor. However, there is little quantitative knowledge on the factors that are conducive to or hindering spruce establishment on CWD. We examined spruce regeneration on CWD by sampling 303 plots (50 cm × 50 cm each) on 56 downed logs in a virgin forest in the Swiss Alps. Variables describing microsite conditions were measured, and fungi were isolated from wood samples. To investigate the relationship between the ecological factors and establishment success, two models were fitted with seedling and sapling density as response variables, respectively. Besides log diameter, the models identified different ecological factors as significant for seedling and sapling establishment, i.e., regeneration depends on different factors in different development stages. Seedling density depended on the type of rot, log inclination, and decay stage. Sapling density depended mainly on light availability, cover by bark and moss, the time of tree fall, and the distance between the log surface and the forest floor. A total of 22 polypore fungi were isolated from the wood samples, four of them being threatened species. White- and brown-rot fungi were found in all decay stages. The visual assessment of the type of rot in the field corresponded in only 15% of cases to the type of rot caused by the isolated fungi; hence caution is needed when making field assessments of rot types. Full article
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