Natural Regeneration Rate Research Articles

Carbon balance of forest management and wood production in the boreal forest of Quebec (Canada)

Management of boreal forests can increase terrestrial carbon sinks and reduce greenhouse gas (GHG) emissions to the atmosphere. A case study was conducted in the boreal balsam fir forests of Quebec (Canada), a commercially important region for forestry, to identify optimal management and wood production solutions that contribute to reducing GHG emissions to the atmosphere. Scenarios were based on a steady level of harvest and silvicultural activities over time and a stable flow of wood products to markets. Scenarios included: increases and decreases in the volume of harvested timber; the transition of harvesting activities from clearcuts (the most common practice in the region) to partial cuts; and changes in the rate of natural regeneration (the usual mode of regeneration) vs. plantations. All scenarios provided a carbon sink regardless of the time frame. Compared with other scenarios, reducing harvest levels increased the forest carbon sink in the short (10 to 20 years) and medium (20 to 50 years) terms. Also, for a similar harvest level, the increased use of partial cutting and planting increased the forest carbon sink. In the long term (over 50 years), strategies with low harvesting levels resulted in lower ecosystem carbon sequestration, even though they still had the lowest cumulative emissions. Nevertheless, higher harvesting levels could not be justified because the long-term increase in the forest ecosystem carbon sink could not offset higher emissions from wood products, particularly from short-lived paper products. Sensitivity analyses showed that improving sawmill efficiency and thus increasing the proportion of long-lived products was an important factor that can greatly reduce emissions. On the other hand, transportation distances between forest stands and sawmills had a relatively marginal impact on the overall carbon balance of forest management and wood production scenarios.

Introducing desirable patches to initiate ecosystem transitions and accelerate ecosystem restoration.

Meeting restoration targets may require active strategies to accelerate natural regeneration rates or overcome the resilience associated with degraded ecosystem states. Introducing desired ecosystem patches in degraded landscapes constitutes a promising active restoration strategy, with various mechanisms potentially causing these patches to become foci from which desired species can re-establish throughout the landscape. This study considers three mechanisms previously identified as potential drivers of introduced patch dynamics: autocatalytic nucleation, directed dispersal, and resource concentration. These mechanisms reflect qualitatively different positive feedbacks. We developed an ecological model framework that compared how the occurrence of each mechanism was reflected in spatio-temporal patch dynamics. We then analyzed the implications of these relationships for optimal restoration design. We found that patch expansion accelerated over time when driven by the autocatalytic nucleation mechanism, while patch expansion driven by the directed dispersal or resource concentration mechanisms decelerated over time. Additionally, when driven by autocatalytic nucleation, patch expansion was independent of patch position in the landscape. However, the proximity of other patches affected patch expansion either positively or negatively when driven by directed dispersal or resource concentration. For autocatalytic nucleation, introducing many small patches was a favorable strategy, provided that each individual patch exceeded a critical patch size. Introducing a single patch or a few large patches was the most effective restoration strategy to initiate the directed dispersal mechanism. Introducing many small patches was the most effective strategy for reaching restored ecosystem states driven by a resource concentration mechanism. Our model results suggest that introducing desirable patches can substantially accelerate ecosystem restoration, or even induce a critical transition from an otherwise stable degraded state toward a desired ecosystem state. However, the potential of this type of restoration strategy for a particular ecosystem may strongly depend on the mechanism driving patch dynamics. In turn, which mechanism drives patch dynamics may affect the optimal spatial design of an active restoration strategy. Each of the three mechanisms considered reflects distinct spatio-temporal patch dynamics, providing novel opportunities for empirically identifying key mechanisms, and restoration designs that introduce desired patches in degraded landscapes according to these patch dynamics.

Genetic variation and phylogenetic position of Taxus sumatrana (Miq.) de Laub. (Taxaceae) in Sumatra, Indonesia based on trnL-trnF region

Abstract. Kamal I, Arrofaha N, Susila, Yulita KS, Rachmat HH, Susilowati A. 2023. Genetic variation and phylogenetic position of Taxus sumatrana (Miq.) de Laub. (Taxaceae) in Sumatra, Indonesia based on trnL-trnF region. Biodiversitas 24: 5155-5166. Taxus sumatrana (Miq.) de Laub. is a synonym of T. wallichiana Zucc. by some authors based on morphological characters and its distribution. This species is a medicinal plant and contains taxol as an anti-cancer with slow natural regeneration rate and increasing threats to their existence. This study aimed to determine the genetic diversity and the phylogenetic analysis using trnL-trnF for T. sumatrana growing in Sumatra, Indonesia. The total of 37 individuals from three natural populations of T. sumatrana were studied, consisting of the current new collection from Toba - North Sumatra and previously studied population of Dempo - South Sumatra and Sungai Penuh, Kerinci Seblat National Park - Jambi. The Toba population did not show variation at individual level within the population as similar results were obtained from the previous study. However, one indel (- and A) was found at 217 bp from all three T. sumatrana populations from Sumatra, Indonesia. When the sequences were aligned with the reference sequence from GenBank, single base substitutions were found at 344, 478,722, and 757 bp consisting of one indel and three single nucleotide polymorphisms (SNPs). Phylogeny tree showed that T. sumatrana from Sumatra population clustered together with T. mairei and T. wallichiana var. mairei and later combined with other T. sumatrana available in NCBI.

Influence of “El Niño Southern Oscillation” periods on plant density of Hoffmannseggia aphylla (Fabaceae) an endangered species

Backgrounds and aims: Studies on the natural regeneration of plant species under hyperaridity conditions have been scarce, mainly because of the low germination percentage of the species under these conditions. Presumably, sporadic phenomena such as the El Niño Southern Oscillation (ENSO) could have a positive effect on the natural germination of these species, although this effect has not yet been satisfactorily explored. M&M: To test the crucial assumption of our statement, a hyperarid region (average rainfall below 5 mm/year) was used as a model to determine the effect of ENSO years on the natural regeneration rate of adult individuals of the endemic legume Hoffmannseggia aphylla (retama) in the Atacama Desert, northern Chile. Thus, the vegetation density of an endemic leguminous species in a sector of the Pampa del Tamarugal, Tarapacá Region, northern Chile, was analyzed for six years. Results: The density of this species increased during ENSO years, mainly due to water flows from the highest sectors of the Tamarugal pampas, such as the town of Pica, in addition to the increase in humidity and summer rainfall. Conclusion: Our results highlight the transcendence of the ENSO in the regeneration of leguminous plants.

Transcriptome Analysis of Embryogenic and Non-Embryogenic Callus of Picea Mongolica.

Picea mongolica is a rare tree species in China, which is of great significance in combating desertification and improving the harsh ecological environment. Due to the low rate of natural regeneration, high mortality, and susceptibility to pests and cold springs, Picea mongolica has gradually become extinct. At present, somatic embryogenesis (SE) is the most effective method of micro-proliferation in conifers, but the induction rate of embryogenic callus (EC) is low, and EC is difficult to differentiate from non-embryonic callus (NEC). Therefore, the EC and NEC of Picea mongolica were compared from the morphology, histological, physiological, and transcriptional levels, respectively. Morphological observation showed that the EC was white and transparent filamentous, while the NEC was compact and brownish-brown lumpy. Histological analyses showed that the NEC cells were large and loosely arranged; the nuclei attached to the edge of the cells were small; the cytoplasm was low; and the cell gap was large and irregular. In the EC, small cells, closely arranged cells, and a large nucleus and nucleolus were observed. Physiological studies showed significant differences in ROS-scavenging enzymes between the EC and NEC. Transcriptome profiling revealed that 13,267 differentially expressed genes (DEGs) were identified, 3682 were up-regulated, and 9585 were down-regulated. In total, 63 GO terms had significant enrichment, 32 DEGs in plant hormone signal transduction pathway were identified, and 502 different transcription factors (TFs) were characterized into 38 TF families. Meanwhile, we identified significant gene expression trends associated with somatic embryo development in plant hormones (AUX/IAA, YUCCA, LEA, etc.), stress (GST, HSP, GLP, etc.), phenylpropanoid metabolism (4CL, HCT, PAL, etc.), and transcription factors (AP2/ERF, MYB, WOX, etc.). In addition, nine genes were chosen for RT-qPCR, and the results were consistent with RNA-Seq data. This study revealed the changes in morphology, histology, physiology, and gene expression in the differentiation of NEC into EC and laid the foundation for finding the key genes to promote EC formation.

Evolutionary Divergence between Toona ciliata and Toona sinensis Assayed with Their Whole Genome Sequences.

Toona ciliata and Toona sinensis belong to the Toona genus of the Meliaceae family and are important timber species in China. T. ciliata is an endangered species at level II due to overcutting and a low rate of natural regeneration. T. sinensis was cultivated as an economic and nutritious tree for more than 2000 years. The two species differ in flower and leaf morphological traits, reproductive systems, and range size of natural distribution. To reveal the potential molecular basis of these divergences, we examined the similarities and differences in their whole genome sequences. Results indicate that T. ciliata had a higher number of expanded gene families than T. sinensis. The whole genome duplication (WGD) occurred before their speciation. The long-terminal repeats (LTRs) insertion was earlier in the T. ciliata genome (3.2985 ± 2.5007 Mya) than in the T. sinensis genome (3.1516 ± 2.2097 Mya). Twenty-five gene families in the T. ciliata genome were detected to be under positive selection compared with background branches of ten different land species. The T. ciliata genome was highly collinear with the T. sinensis genome, but had low collinearity with the genomes of more distant species. These genomic and evolutionary divergences are potentially associated with the differences between T. ciliata and T. sinensis in terms of their reproductive systems and ecological adaptation.

How Sustainable is Mangrove Harvesting in Lamu? An Analysis of Forest Structure

ABSTRACT Sustainable management of mangrove resources requires monitoring of status and conditions of the forest over time. This study assessed structure and regeneration of mangroves across five mangrove management blocks in Lamu, Kenya. Using stratified random sampling strategy, mangroves were sampled in 152 square plots of 400 m2 along belt transects established perpendicular to the shoreline. Linear regeneration sampling (LRS) was employed to assess composition and patterns of natural regeneration. Six mangrove species were encountered during this study. Based on importance value index, the dominant mangrove species in Lamu are Rhizophora mucronata and Ceriops tagal. At least 42% of the forest is stocked with low-quality poles, an indicator of prolonged human pressure. However, natural regeneration rate of 7,342 ± 450 juveniles ha−1 observed in the forest is considered adequate to support forest recovery after disturbance. The findings of the study have direct applications in the development of harvest plans for mangroves in Lamu.

A Chromosome-Level Genome Assembly of Toona ciliata (Meliaceae).

Toona ciliata Roem is an important timber species in the Toona genus of the Meliaceae family and an endangered species due to over-cutting and a low rate of natural regeneration in China. Although molecular markers have been applied to studying population genetic diversity, the absence of a reliable reference genome limits in-depth genetic conservation and evolutionary studies of this species. Here, we reported a high-quality assembly of the whole genome sequence of T. ciliata. The total assembled genome has 520.64 Mb in length anchored on 28 chromosomes (contig N50 = 4.48 Mb). A total of 42,159 genes were predicted after the ab initio, homology-based, and transcriptome analyses. A total of 41,284 protein-encoding genes (97.92%) were functionally annotated and 1,246 non-coding RNAs were identified in the T. ciliata genome. Phylogenomic analysis showed that T. ciliata was divergent at 15.06 (6–25) Ma from T. sinensis of the same genus Toona. This whole genome sequence provides a valuable resource to study the genetic conservation and molecular evolution of T. ciliata in the future.

Mesquite management in the Mezquital Valley: A sustainability assessment based on the view point of the Hñähñú indigenous community

Abstract The indigenous community of El Alberto (Ixmiquilpan, Mexico), in the Mezquital Valley, has applied numerous uses of the mesquite (Prosopis laevigata) resources in their daily life for decades. Our objective was to understand the relationship between the rural community and this leguminous tree, to determine how sustainable their management is. For this purpose, we applied the Framework for the Evaluation of Management Systems using Indicators (MESMIS, Spanish acronym). Twenty-one indicators were identified, and a qualitative index was established to assign a sustainability value. The results identified fuelwood, fertility, forage and shade as the principal uses of mesquite nowadays. The local indigenous community does not promote the propagation of this leguminous tree but rather rely on its natural regeneration. However, the rate at which they cut down and exploit mesquite is higher than the natural regeneration rate, reflecting a low level of sustainable management. Strong equity was registered. First, there is a passive process associated with the construction of irrigation channels for agriculture, which resulted in the deforestation of the mesquite. Second, there is evidence of an active process where members of the community decide to migrate abandoning their indigenous worldview, which, consequently, has impacted negatively on the mesquite resource. Change processes caused a shift in the community’s worldview and led to cultural erosion. In conclusion, changes must be made to the community’s current social ecological system to achieve sustainable management, such as building a strong feeling of community identity, evolution of the community’s uses, customs, quality and lifestyle, and their collaboration with the scientific community.

Natural regeneration in a mixed ombrophilous forest remnant in southern Brazil

The study of forest regeneration allows the diagnosis of conservation status of fragments and estimating population parameters that are essential for management projects. This study evaluated the structure, diversity and dynamics of the tree regenerating component of a remnant of mixed ombrophilous forest, aiming to support management actions for this forest type. The study was developed at the Parque Estadual das Araucárias (PEAR), located in the western region of the state of Santa Catarina, southern Brazil. A total of 100 plots of 25 m2 (0.25 ha) were allocated, all individuals with height ≥ 1.0 m and DBH < 5 cm were sampled. Shannon’s diversity index (H’), Pielou’s equability index (J) and total natural regeneration rate (TNR) were estimated. We sampled 1,425 individuals from 99 species and 39 families, with an estimated total density of 5,700 individuals by hectare. The richest families were Fabaceae (13), Myrtaceae (10) and Lauraceae (7). The H’ was 3.76 and the J was 0.80. The TNR rate ranged from 0.05 to 8.12%, highlighting Trichilia elegans, with the highest rate and Araucaria angustifolia with low potential for natural regeneration. The analysis of the results indicated a high diversity in the regenerating component of the PEAR compared to other studies, probably because the area presents itself as a successional mosaic due to past disturbances.

Structure and Diversity of Agroforestry Parklands in the Sudano-Sahelian Zone of Cameroon

The general objective of the study is to characterize the woody vegetation of 05 agroforestry parkland in the Sudano-Sahelian zone of Cameroon. A total of 40 floristic surveys of 200  20 m were carried out. A total of 33 species in 20 families and 31 genera were recorded. The dendrometric survey method enabled us to characterize the vegetation of the agroforestry parks. The dendrometric parameters and indices calculated according to the agroforestry parks vary from one park to another. Thus, density varies from 108±2.98-223±8.01 individuals/ha, recovery from 6.11±0.21-10.12±0.31%, basal area from 6.54±1.12 to 10.05±1.87 m²/ha, biovolume from 20.09±2.22-38.54±3.76 m3/ha, total height from 2.11±0.01-5.06±0.04 m, natural regeneration rate from 2.11±0.52-7.40±1.09%. The Shannon index varies from 1.36±0.20-2±0.29 bits, Pielou index from 0.14±0.07-0.35±0.18 and Simpson index from 0.82±0.02-0.97±0.03. The species with the highest SIV and SIR are Combretum glutinosum, Combretum adenogonium, Sclerocarya birrea, Prosopis africana, Entada africana, Anacardium occidentale, Burkea africana, Maytenus senegalensis, Ficus glumosa. The Mimosaceae, Caesalpiniaceae, Combretaceae show a high representativeness in relation to their family importance value. The diameter structure showed a predominance of young individuals and the height structure showed a predominance of individuals of class [4-6 m]. These results can be used as a reference in monitoring the vegetation dynamics of agroforestry parks subject to recurrent droughts and anthropogenic pressures. This study provides a better understanding of the vegetation in agroforestry parks in order to better manage these plant resources.

Nutritional Characteristics and Seed Germination Improvement of the Forage Shrub Retama sphaerocarpa (L.) Boiss

Summary Retama sphaerocarpa shrubs form populations that can be an important forage resource during the dry season when pasture shortages are common in certain arid and semi-arid Mediterranean basin regions. The leaves of R. sphaerocarpa were analyzed for dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF) and acid detergent lignin (ADL) contents. Leaves were also analyzed for the concentration of macro- (P, K, Ca and Mg) and microelements (Mn, Zn, Fe, and Na). According to the contents of CP, NDF, ADF and ADL in the leaves examined, this species could strike an appropriate balance between available feed ingredients for daily nutritional needs of animals. The contents of Ca, K, Na, P, Fe, Mg, and Zn in Retama sphaerocarpa shrubs were found to be high, compared to a number of other forage shrub species. Conversely, the rate of natural regeneration of this shrub in situ was estimated at 2-5%. R. sphaerocarpa seeds are affected by seed coat dormancy that prevents seed germination under natural conditions. The seed germination was assessed at a laboratory after the chemical scarification of seeds by concentrated sulphuric acid in the duration range of 0 min and 240 min. The principal component analysis of data related to the germination ability and seedling emergence showed that the best pretreatment was 120 min immersion in sulphuric acid at 25°C (± 2°C), resulting in 86% of the final germination percentage (FGP) and 14.6 cm of the seedling length (SL). According to the results obtained, this species could be considered a ruminant feed of great nutritive value when drought decreases grazing herbaceous biomass yields. These results should encourage farmers and foresters to integrate R. sphaerocarpa into their planting programs.

Natural Regeneration of Marker Species of the Tropical Dense Humid Ecosystems in the Loukaya Peri-Urban Forest, Brazzaville-Congo

The study aimed at evaluating the natural regeneration of some characteristic species in the Loukaya peri-urban forest was carried out in Brazzaville, over three surveys of one hectare each. The botanical inventory of the 23 species monitored covers the subjects of 2 ≤ d0.20 1.30 ≥ 10 cm. The study shows 1255 individuals of which 68.27% are 2 ≤ d0.20 < 10 cm. While being tropophilic and mesophilic, this ecosystem is pauciflorous and paucispecific. The phytoecological data show that this formation, which is a link in the African dense humid forest, presents values far below those known elsewhere; while being faithful to the forests of the Cataractes Plateau. As for the rate of natural regeneration, this index is greater than or equal to 100 for 69.56% of the taxa. Sarcochores and heliophytes are the taxa that best support this natural regeneration. This high rate of regeneration would be correlated with the high level of anthropization, whose large canopy gaps are accompanied by a flow of light conducive to the installation of seedlings.

海南岛不同林龄短枝木麻黄凋落物内外真菌多样性分析

以海南海口桂林洋滨海立地上幼龄林、中龄林和成熟林短枝木麻黄为研究对象，采集凋落物和林地土壤样品，利用IlluminaMiseq PE300测序平台对凋落物内外真菌ITS rDNA进行高通量测序，分析了凋落物内外真菌群落多样性及其与凋落物和林地土壤理化性质的关系。结果表明：（1）所有样品获得669476条有效序列，隶属6门23纲59目119科212属314种。3林龄木麻黄凋落物外生真菌多样性和丰富度高于内生真菌。（2）内外真菌群落结构有较大共性，子囊菌门和担子菌门为优势门，煤炱目、炭角菌目和木耳目为内外真菌共同优势目。Coniochaetales、Magnaporthales等4个目仅在凋落物内部分布，而蛙粪霉目、丝孢酵母目为外生真菌特有菌群。（3）木麻黄凋落物pH值和有机碳显著影响着凋落物内生真菌群落结构，而土壤容重和铵态氮显著影响着外生真菌群落结构。研究结果为探讨微生物在木麻黄凋落物降解过程中作用的研究奠定基础。;Casuarina equisetifolia forests are widely spread in tropical to subtropical coast, serving as windbreak forests. However, C. equisetifolia forests have poor natural regeneration rate, which were considered involving the allelopathy of the litter. The aim of the study was to investigate the characteristics of endophytic and epiphytic fungal communities of the litter in C. equisetifolia forests (young-aged forest, middle-aged forest and mature-aged forest) at Guilinyang coast of Haikou, Hainan province, China. The ITS rDNA was sequenced by Illumina high-throughput sequencing technology, which was used to analyze the diversity of the microbial communities of the litter from different aged forests. The litter and soil physicochemical properties were measured to determine the correlations between them. A total of 669,476 valid sequences were obtained for all samples and contained 6 phyla, 23 classes, 59 orders, 119 families, 212 genus, and 314 species. The diversity and abundance of the epiphytic fungal communities of the C. equisetifolia litter was higher than those of the endophytic fungi. There were greater similarity among the endophytic and epiphytic fungal community compositions. It was found that Ascomycota and Basidiomycota were the main fungi of the litter. There were three dominant orders exist in both endophytic and epiphytic fungal communities, including Capnodiales, Xylariales and Auriculariales. Coniochaetales, Magnaporthales and another two orders were specially distributed in the litter, while Basidiobolales and Trichosporonales were endemic to epiphytic fungi. The pH and organic carbon of the litter were significantly correlated to endophytic fungal community structure, while the bulk density and ammonium nitrogen of the soil were significantly correlated to epiphytic fungal community structure. This work provided an important theoretical basis for studying the role of microorganisms in the decomposition of C. equisetifolia litter.

Crown and regeneration responses to silviculture systems in Pine and Sal forests: preliminary results from silviculture trials in Mid-hills Nepal

Silviculture trial plots were established in Kavre and Lamjung districts by the EnLiFT Project (Enhancing livelihoods and food security through improved agroforestry and community forestry in Nepal) to examine stand response to selected silviculture systems – uniform shelterwood, selection system, and negative thinning and as a showcase to forest users for these silviculture systems. This paper analyses the extent of canopy gaps on these trial plots after one-year of application of silviculture treatments and regeneration development. Using crown photographs, crown cover was estimated and compared between silviculture systems. The analysis showed that rigid silviculture systems like shelterwood and selection systems created canopy gap larger than negative thinning in Pine plantations and the rate of natural regeneration was directly related with the canopy gap. However, in Shorea robusta-Castanopsis- Schima (Sal-Katus-Chilaune) forest, negative thinning created canopy gap larger than selection system due to removal of 4-D trees, majority of trees were Schima wallichii (Chilaune), which typically have large spreading crown. Although, it may be too early to conclude the relationship between regeneration development and canopy gap from the trial plots, it became clear that silviculture operations have significant role in promoting higher regeneration. Selection and shelterwood systems are better than current silviculture regime represented by negative thinning in this study. Banko JanakariA Journal of Forestry Information for Nepal Special Issue No. 4, 2018, Page: 98-103

Indigenous knowledge and stand characteristics of a threatened tree species in a highly insecure area: Chilgoza pine in Afghanistan

Abstract Chilgoza pine (Pinus gerardiana) is an important source of income in forested eastern Afghanistan through the harvest of edible seeds. Since the late 1970s, the resource has been largely inaccessible to researchers and government personnel from outside the region, except for the years 2002–2015, roughly coinciding with Operation Enduring Freedom. We assessed physical and social attributes of chilgoza pine forests and the management capacity of indigenous communities. We employed interviews/questionnaires and field measurements performed by Afghan forest scientists from Kabul, trained local residents, and U.S. forest scientists associated with military operations to examine stakeholder perceptions of chilgoza pine forest resilience, assess forest health, stand structure and natural regeneration status. Intensive cone collection, tree damage caused by cone harvesting, grazing, fuelwood collection, and other biotic/abiotic factors (insects, diseases, and drought) were associated with chilgoza forest degradation. Most interviewees observed natural regeneration in the understory layer of chilgoza forest stands, but perceived the overall rate of natural regeneration to be insufficient. Respondents from villages prohibiting grazing and fuelwood collection reported the greatest regeneration while the converse was associated with the lowest levels of regeneration. Field measurements confirmed the scarcity of natural regeneration of chilgoza pine, portending the further decline of this species in Afghanistan. Field surveys indicated diverse stand conditions, age class structures and land use practices employed by local stakeholders, suggesting the need for situation-specific forest management recommendations. We discuss the opportunities and limitations for forest resources data collection in highly insecure environments.

Development Prospects of the Mangrove Relic of Foulpointe—East Madagascar

Located about fifty kilometers North of Toamasina (East Madagascar), the Commune of Mahavelona Foulpointe has a mangrove relic of about 2 hectares. Despite the ecological and socio-economic roles played by this ecosystem, it remains so far an orphan site, both in terms of official management and development. The purpose of this article is to take stock of the situation with a view to proposing methods for the sustainable development of this small mangrove via valuation of its natural dynamics. Systematic floristic inventory work was carried out, following a linear ABC transect of 50 - 100 m, from the sea (zone C) to the rear mangrove (zone A). Five mangrove species exist at Foulpointe: Avicennia marina, Sonneratia alba, Bruguiera gymnorrhiza, Rhizophora mucronata, Lumnitzera racemosa. With anthropogenic harvesting and tourism activities in the area, this ecosystem suffers an annual spatial loss of about 0.14 ha between 2009 and 2016. With a natural regeneration rate of about 966% the small man-grove has a strong capacity for regeneration. Taking into account the pace of current clearing, it would disappear in 10 - 15 years. The valorization of regenerated young plants, followed by intensive preservation and restoration actions, constitutes a sustainable development path.

Existence and Efficiency of Stationary States in a Renewable Resource Based OLG Model with Different Harvest Costs

Abstract In a renewable resource based overlapping generations (OLG) model without harvest costs, a complex combination of the time discount factor, the resource production share, and the natural regeneration rate ensure the existence of a stationary market equilibrium and its intergenerational efficiency when the own rate of return on natural capital is positive. This paper investigates to what extent previous findings carry over to an OLG economy with two types of unit harvest costs (constant, inverse stock dependent) arising from the competition for labor between resource harvesting and resource processing. In contrast to the model without harvest cost, we show why large unit harvest costs, surprisingly, do not require a complex combination of basic parameters for the existence of a stationary state, and that in the model with stock dependent costs intergenerational efficiency might occur even when the own rate of return on natural capital is negative.

Effects of forestry practices on the regeneration and biodiversity of woody plants in the northern forest ecosystems of Iran

Undoubtedly, the regeneration and sustainability of forests are the most important aspects of sustainable forest management. The present study was conducted in Patam district, located in Kheyroud forest, Iran, and the regular regeneration of various plant species was evaluated in the region. The study of the regeneration was randomly regularly carried out by using a grid of 150 × 200 m and the sample plot with the area of 1.0 R (radius 1.8 m), provided by centre for sample plot. The highest rate of regeneration (seedlings) was observed in Carpinus betulus (50%), Acer insigne (23%), Fagus orientalis (10%), afforestation (6.2%), Acer cappadocicum (6%), Parrotia persica (2.8%), and Diospyros lotus (2%), respectively. In addition, 74 and 26% of the seedlings had height less than and more than 50 cm, respectively. Therefore, the studied region has proper conditions for regeneration in terms of the soil and mother trees. However, the number of the seedlings with height more than 50 cm is not above the normal range. In the studied region, regeneration coverage level, herbaceous species coverage level, and coverage level without sample plots were calculated to be 52, 41, and 7%, respectively. Considering the low rate of natural regeneration compared to similar forests and the habitat of the studied forest, the main causes in this regard could be the lack of mother trees, animal grazing, and the density of the forest floor vegetation. Therefore, the elimination of animal grazing and plantation operations are necessary for the improvement of regeneration.

Potencial regenerativo de espécies arbóreas em fragmento de Mata Atlântica, Pernambuco, Brasil

Objetivou-se caracterizar o estrato regenerante de um fragmento de Floresta Ombrófila Densa das Terras Baixas, mediante avaliações da riqueza, estrutura e diversidade. Para estimar os índices de regeneração natural por espécie para cada classe de tamanho de planta (RNC), visando à obtenção do índice de regeneração natural total (RNT), foram alocadas, 40 parcelas de 25 m² (5 m x 5 m). A análise foi realizada com indivíduos que apresentaram CAP &amp;lt; 15,0 cm e altura igual ou superior a 1,0 m. As classes de alturas foram pré-determinadas, em que: C1 = 1,0 m-2,0 m; C2 = 2,1 m-3,0 m; C3 = &amp;gt; 3,0 m. Foram amostrados 1.197 indivíduos distribuídos em 81 espécies, 31 famílias e 51 gêneros. A família Fabaceae obteve maior riqueza, seguida por Melastomataceae e Myrtaceae. A espécie Protium heptaphyllum destacou-se com o maior Valor de Importância (VI), apresentando 14,64% do total de VI. As espécies que apresentaram os maiores RNTs foram: Protium heptaphyllum (Aubl.) Marchand, Thyrsodium spruceanum Benth., Eschweilera ovata (Cambess.) Miers e Brosimum guianense (Aubl.) Huber. Em relação à classificação sucessional, houve predominância das espécies de início de sucessão, comprovando a condição jovem da floresta. Os resultados mostram que o fragmento estudado apresenta boa capacidade de regeneração possibilitando maior riqueza e diversidade de espécies do estrato arbóreo adulto à longo prazo.