Plant communities, species diversity, richness, and regeneration of a traditionally managed coastal forest, Kenya

The Kenyan coastal forests make up one of the World 25 Biodiversity Hotspots. They consist of over 140 fragments (the majority with areas less than 0.5 km²) of the once extensive Zanzibar-Inhambane lowland moist forest. The over 60 known Mijikenda sacred Kaya forests and groves scattered along the coastal hinterland form the greater part of this ecosystem. The forests are of biological and cultural significance, and this has been recognized nationally and internationally, with some now listed as World Heritage Sites. The forests are protected by councils of Kaya elders who regulate use of their resources. Increasing human population and subsequent rise in demand for forest products and land for settlement has put a strain on these relic forests. Farm encroachment and extraction of forest products in different Kaya forests have affected the vegetation ecology at varying levels. This study investigated the spatial species distribution, association and regeneration potential of commonly utilized plants in one of these traditionally managed ecosystems. A modified nested plot method was used to collect data in the field.Using TWINSPAN multivariate, and indicator species analysis, two plant communities (Asteranthe and Bridelia) and an undifferentiated vegetation type were identified. Species association in Asteranthe consisted largely of forest dependant species, with a significant presence of woody climbers. It was comprised of two sub-communities namely Manilkara and Scorodophloeos. In contrast the second plant community, Bridelia, was dominated by light demanding species. It comprised one sub-community (Catunaregam) and a seral stage (Keetia). The species diversity and richness was higher in the Asteranthe community compared to Bridelia. Some of the forest species commonly utilized by the local people were observed to regenerate both in open and closed forest habitats while others had seedling recruitment confined to closed forest.Despite some coastal forests showing physiognomic similarity, detailed study shows intra-variation linked to topography, exposition, type and intensity of human perturbation both currently and in the distant past. Clearly, vegetation patterns of coastal forests of eastern Africa change at fairly short intervals.Recruitment of forest specialists is likely to decline if closed forests are opened up by farm encroachment, however their less specialized counterparts can pioneer in re-colonization of disturbed sites if conservation is strengthened. There is need to invigorate traditional management systems of forests with cultural significance by recognizing and giving increased legal mandates to the local custodians.     

Effects of livestock exclusion on tree regeneration in church forests of Ethiopia

In Ethiopia, forests near churches, are the last remnant forest patches. These forests are currently under threat, probably due to diminishing areas of the forest itself and repeated grazing for extended periods by cattle. We assessed the effect of livestock exclusion on the regeneration of four indigenous tree species in two church forests. The four species have a high abundance and socioeconomic value, but limited regeneration in the two forests. We investigated the effect of grazing and trampling on seed germination, seedling survival, and seedling growth. Livestock grazing had a strong negative effect on germination, seedling growth and mortality. In fenced plots, more seeds germinated, seedling survival was higher and seedlings grew faster. Seed germination was higher inside the forest than in the adjacent open area for all species. Seedling survival was not different between forest interior and open fields, except for unfenced plots in the open fields where survival was lower because of the higher grazing pressure. In unfenced plots, no seedlings survived until the end of the year, indicating that grazers destroyed the seedling bank in and around the forest. The significant interaction between fencing and species on seed germination and seedling survival revealed that the magnitude of damage due to grazing can vary with species.     

采伐作业对长白山阔叶红松林林下植被影响的研究(英文)

森林采伐是森林经营中的一个关键环节。采伐对树木天然更新的影响直接关系到森林的结构、组成及森林的可持续经营。本文以长白山阔叶红松林为研究对象,对择伐5 年后不同作业迹地(集材道、楞场和采伐后林窗)的幼苗更新及灌木、草本的多样性进行研究,并以没有进行采伐干扰的林地作为对照。共设计样地23 块,在各个小样地内调查幼树的种类、树木、高度;灌木和草本植物的种类、树木、高度和盖度,应用SPSS 软件进行一元方差分析。结果表明,择伐作业影响幼苗的更新,灌木和草本的多样性在作业迹地增加,尤其在林隙处的多样性最高。适当采伐能促进幼苗的更新,特别是阔叶树种的更新。集材道对幼苗密度的影响比对幼苗高度的影响大,幼苗密度在集材道上密度最高;采伐作业对针叶树种有严重的影响,在三种作业迹地上针叶树种的密度都比对照低。为了维持森林的结构和组成,在森林收获和楞场的建立时,必须采取科学措施保护针叶树种。此外,采伐林窗和楞场的面积都应该减小。为了确保采伐迹地建群树种的更新,经营中应该在保护生物多样性的前提下,适当控制过于旺盛的灌木和草本层的生长。本研究结果将为采伐后作业迹地的恢复和森林的可持续经营提供科学的依据。图1 表4 参14。     

Coppice regrowth in a disturbed tropical dry limestone forest in Jamaica

The Hellshire Hills are an extensive area of tropical dry forest over limestone, located on the south coast of Jamaica. Despite being a protected area, they are subject to encroachment and clearance by charcoal burners, leaving a relatively pristine core within more disturbed areas of forest. Future management requires a consideration of the forest’s resilience to such disturbance, and this study reports on coppice regrowth following clearance. The number of coppice shoots and the length and diameter at breast height (DBH) of the leading shoots were measured on tree stumps 14 months after they were cut in an experiment. Coppice regrowth after cutting was measured on a total of 476 stumps, representing 51 species. Coppice production and growth was vigorous as there was an extremely high incidence of coppice regrowth among and within the species in this forest after it had been cut. Initial regrowth was high with the diameter recovered by the leading shoots after 14 months approximating to 29% per year. Of the 51 species sampled three did not coppice at all and the average percent of individuals found with shoots within each species was 81%. The height and diameter of the leading shoots was significantly different among the species and the average height recorded of the leading shoots was 114 cm while the average diameter recorded was 10 mm. Larger sized stems (>10 cm DBH) on average produced more coppice shoots and larger sized shoots than smaller sized stems (<10 cm DBH) while smaller sized stems recovered more biomass than larger sized stems irrespective of species. The average diameter of the leading shoots decreased significantly with increasing shoot densities. At the species level there was a significant relationship between stem diameter and the number of shoots produced in seven of the 27 species analysed and three species returned significant relationships between stem diameter and average height of leading shoots. Coppice regrowth clearly offers considerable resilience to disturbance in this dry forest where successful regeneration by seed is highly susceptible to rainfall seasonality. However, the different abilities of species to produce coppice shoots will likely affect long-term species diversity if the present rate of clearance continues.     

公路沿线森林景观评价及更新方法

文章以浙江省庆元县54省道黄田镇区段杉木林景观改造设计为例,尝试建立公路沿线森林景观敏感度评价标准体系,为森林景观更新方案的设计建立相对客观的判别依据,并基于三维虚拟现实技术模拟不同的方案效果以供对比和检验,提出了符合实际的公路沿线森林景观更新设计方法。       

Tree regeneration and future stand development after bark beetle infestation and harvesting in Colorado lodgepole pine stands

In the southern Rocky Mountains, current mountain pine beetle (Dendroctonus ponderosae Hopkins) outbreaks and associated harvesting have set millions of hectares of lodgepole pine (Pinus contorta var. latifolia Engelm. ex Wats.) forest onto new stand development trajectories. Information about immediate, post-disturbance tree regeneration will provide insight on dynamics of future stand composition and structure. We compared tree regeneration in eight paired harvested and untreated lodgepole pine stands in the Fraser Experimental Forest that experienced more than 70% overstory mortality due to beetles. New seedlings colonized both harvested and untreated stands in the first years after the beetle outbreak. In harvested areas the density of new seedlings, predominantly lodgepole pine and aspen, was four times higher than in untreated stands. Annual height growth of pine and fir advance regeneration (e.g., trees established prior to the onset of the outbreak) has doubled following overstory mortality in untreated stands. Growth simulations based on our regeneration data suggest that stand basal area and stem density will return to pre-beetle levels in untreated and harvested stands within 80-105 years. Furthermore, lodgepole pine will remain the dominant species in harvested stands over the next century, but subalpine fir will become the most abundant species in untreated areas. Owing to terrain, economic and administrative limitations, active management will treat a small fraction (<15%) of the forests killed by pine beetle. Our findings suggest that the long-term consequences of the outbreak will be most dramatic in untreated forests where the shift in tree species composition will influence timber and water production, wildfire behavior, wildlife habitat and other forest attributes.     

Influence of distance to forest edges on natural regeneration of abandoned pastures: a case study in the tropical mountain rain forest of Southern Ecuador

In spite of its high diversity the forests in Southern Ecuador are highly endangered by deforestation. One of the main reasons for the loss of forests is the conversion into pastures. Due to their fast degradation, the pastures are abandoned after several years and form an increasing area of unproductive land. The remoteness from existing forest edges is discussed as one reason for the very slow natural reforestation of these areas. In this study we analyzed the regeneration of a secondary forest after approx. 38 years of succession in relation to the distance from the surrounding forest. We revealed that regeneration was rather slow. Especially larger trees with dbh > 10 cm were very scarce. Only Dioicodendron dioicum, Graffenrieda emarginata and Clusia sp. achieved larger diameters. The basal area of the secondary forest is still far beyond the original level in the primary forest. The number of species on plot level and the Shannon index were significantly lower in the secondary forest compared to the primary forest. The total number of species decreased from 47 to 31 with increasing distance from the forest edge and the similarity of species composition to the upper story declined to a level of 56.4 (Sörensen). Alzatea verticillata, Macrocarpea revoluta and Palicourea andaluciana had significantly higher abundances in the succession stages than in the natural forest. The most abundant species in all regeneration plots, G. emarginata and Purdiea nutans, seem to be generalists as they did not show preference either to natural forest or successional stages.     

现行森林采伐更新规程的几点思考

根据当前森林分类经营和实施天保工程的要求以及森林资源现状和每年对采伐迹地的调查经验 ,我们对现行森林采伐更新规程从其时效性、与资源的吻合性、科学性、操作性等多方面做了思考和评价 ,为今后采伐更新规程的修订及森林资源管理提供参考依据和思路。     

Canopy gap characteristics and its influence on the regeneration of broad-leaved Korean pine forests in Changbai Mountain

lntroductionBroad-leavedKoreanpineforestisacldriaxforestli1tCm-peratezoneofNortheaster11Cl1ina.ltscharacteristichasIligllstabilityandproductivity.Therewerenlanyresearcl1worksfocusedontl1estructure,dynandcsanditsmain-tainingmechanisn1.Researchontheforestregeneratio11wasamali1approaclltoundersta11dtlleforestdynanlicsI;j.ThereweremanyresearcI1eso11tl1erege11erationofh1iskindofforestsincel95ol5~ll].Butfewoftl1emweredoneundertheconsiderationofcanopygapdistUrbance.Sincel99O's,moreandmoreresearch…     

Comparative regeneration ecology of three leguminous timber species in a Bolivian tropical dry forest

A comparative study of the regeneration ecology ofthree lesser-known leguminous timber species wasconducted in the seasonally dry forests of SantaCruz, Bolivia to determine species regenerationstrategies and make silvicultural recommendationsfor these species. The study included arepresentative from each subfamily of Leguminosae:Anadenanthera colubrina (Vell. Conc.) Benth.(Mimosaceae), Copaifera chodatiana Kunth.(Caesalpinaceae), and Centrolobium microchaeteC. Martius (Fabaceae). After production in themid-late dry season, seeds of all species sufferedhigh (>30%) rates of predation. For seedssurviving predation, Anadenanthera germinatedwithin three days after the first rains and a highgermination capacity (82%), but most seedlings diedfrom inadequate light or during subsequent periodsof drought. Copaifera germinated more slowlybut had high germination capacity (85%). Centrolobium had very low germination capacity(4%) and germinative energy. Most successfulregeneration of Centrolobium occurred viasprouting from damaged roots on or near loggingroads where it had a density of 261 root sprouts/ha.Anadenanthera regenerated best from seedin areas with soil disturbance or burning. Theregeneration of these species will likely increaseunder more intensive logging and/or post-harvestcompetition control treatments in logging gaps. Themore shade-tolerant Copaifera is most suitedto the current regime of light selective logging,but all three species are likely to be responsive topost-harvest competition control treatments. Impacts of controlled and natural fire were mixed,but generally seedling regeneration and growth wereeither not significantly affected or were increasedby fire.     

Bryophytes as potential indicators of forest integrity

Forest integrity has been proposed as one conservation endpoint that integrates desirable characteristics such as natural biodiversity, stand structure and continuity. Although its defining criteria are still under discussion, any surrogates must effectively represent or predict their status, and be easier to measure than the criteria themselves. Bryophytes have been proposed as such surrogates, because they are important components of forest integrity, and considerable research indicates that some groups are sensitive to the changes associated with specific forest management regimes. The objectives of this paper are (1) to review the issues in determining indicators of forest integrity, including desirable qualities in such indicators, (2) to review the state of knowledge concerning bryophytes as components of forest integrity (i.e. their responses to forest management practices), and (3) to assess bryophytes as potential indicators of forest integrity, in terms of both qualities desirable in indicators and our understanding of bryophyte response patterns. Although bryophytes possess some characteristics that suggest potential indicator value, many challenges prevent their reliable application. I highlight key areas in which research is required to identify operational bryophyte indicators of forest integrity. Along with a standardized protocol to select and calibrate such indicators, we urgently require strategic research to compile data on undisturbed reference forests on which to base selection of endpoints; species-specific ecological tolerances, with consideration of complex interactions; mechanisms of response to disturbance, with consideration of temporal aspects; population viability thresholds; and recruitment effects on community assembly. Whether we succeed in finding bryophyte indicators of forest integrity, this research would also provide the data to monitor and interpret the integrity of the bryophyte community.     

Woody plant regeneration after blowdown, salvage logging, and prescribed fire in a northern Minnesota forest

Salvage logging after natural disturbance has received increased scrutiny in recent years because of concerns over detrimental effects on tree regeneration and increased fine fuel levels. Most research on tree regeneration after salvage logging comes from fire-prone systems and is short-term in scope. Limited information is available on longer term responses to salvage logging after windstorms or from forests outside of fire-prone regions. We examined tree and shrub regeneration after a stand-replacing windstorm, with and without salvage logging and prescribed fire. Our study takes place in northern Minnesota, USA, a region where salvage logging impacts have received little attention. We asked the following questions: (i) does composition and abundance of woody species differ among post-disturbance treatments, including no salvage, salvage alone, and salvage with prescribed burning, 12 years after the windstorm?; (ii) is regeneration of Populus, the dominant pre-blowdown species, inhibited in unsalvaged treatments?; and (iii) how do early successional trajectories differ among post-blowdown treatments? Twelve years after the wind disturbance, the unsalvaged forest had distinctly different composition and abundance of trees and woody shrubs compared to the two salvage treatments, despite experiencing similar wind disturbance severities and having similar composition immediately after the blowdown. Unsalvaged forest had greater abundance of shade tolerant hardwoods and lower abundance of Populus, woody shrubs, and Betulapapyrifera, compared to salvage treatments. There was some evidence that adding prescribed fire after the blowdown and salvage logging further increased disturbance severity, since the highest abundances of shrubs and early successional tree species occurred in the burning treatment. These results suggest that salvage treatments (or a lack thereof) can be used to direct compositional development of a post-blowdown forest along different trajectories, specifically, towards initial dominance by early successional Populus and B.papyrifera with salvage logging or towards early dominance by shade tolerant hardwoods, with some Populus, if left unsalvaged.     

Effects of widely spaced trees and livestock grazing on understory environments in tropical savannas

The effects of widely spaced trees ofAcacia tortilis andAdansonia digitata on their understory environments were investigated in four savannas located along a gradient of increasing livestock utilization in Tsavo National Park (West), Kenya. Plant species composition and biomass and the physical and chemical properties of soils that occur below tree crowns were compared to open grasslands. The tree-crown zones at lightly and moderately grazed sites had a unique understory flora and higher plant biomass, lower temperatures and bulk densities, and higher levels of P, K, Ca and mineralizable N than their associated opengrassland zones. In the heavily grazed savanna, few differences between tree-crown and grassland zones were found. The beneficial effects of savanna trees on their understory environments appear to diminish with increasing livestock utilization.     

Effects of harvesting on soil properties and regeneration quality in larch-birch forest in China

INTRoDUCTIONoneopeationsite,locatCdin5O'47'Nandl24"2o'E,wasselectCdastCstsite,Wherethelarch(Larixgmelinii)dominatesmostlythetreepopulahonwithnearlyeightypercentin.standingvolume.Theresttreesarebirch.Annalprecipitation,tethperAnandvaPori-zationare5lonun,-2.4Cand3lommrespec-tively.Elevationisaround45Omoversealevel.CuttingmethodsusedinthissitewereselechvecuningandclearcuttingwithgrQUndtractorskiddingaswellasasmallpwtofani-malskidding.CHANGESoFSoILPRoPERTIESCAUSEDBYHARVESTI…     

Forest natural regeneration and biomass production after slash and burn in a seasonally dry forest in the Southern Brazilian Amazon

This study estimates the aboveground biomass accumulation after forest clearing and slash burning and describes the structure and successional development of the secondary forest in the seasonally dry southern Amazon. The original burn study was conducted in four land clearings in 1997, 1998, and 1999. The size of the clearings varied from 1 to 9 ha. The native forest was felled, allowed to dry for approximately three months and then burned by the end of the dry season. A census was conducted in the central 1-ha forest on each site prior to the area's felling and burn. The aboveground biomass (AGB) and structure were similar to other primary tropical forests. However, the high density of Cecropia spp. before the forest felling and burn treatment indicates past low intensity disturbances. Seven and eight years after the fire, the fallow forests were still in an early successional stage dominated by Cecropia spp. The four areas had a high biomass accumulation during the studied period, varying from 7.5 to 15.0 Mg ha⁻¹ year⁻¹. The lower biomass accumulation in one plot was an effect of a higher fire severity, produced by the one-year difference in time between slash and burn of the forest, slowing the natural regeneration of Cecropia spp. The time needed for this forest to recover to the pre-fire AGB levels ranged from 20 to 30 years, assuming the current AGB accumulation rates are maintained. Considering these results, the maintenance of regenerating secondary forests in the Amazon would be a significant contribution to soil and watershed protection, minimizing biodiversity losses and perhaps mitigating climatic changes effects in the region.     

Regeneration of timber trees in a logged tropical forest in North Bolivia

For sustainable forest management, it is important to know the response of timber species to the change in environment caused by logging. We performed a 2-year study on germination, survival and growth of four timber species, Cedrela odorata, Swietenia macrophylla, Hymenaea courbaril, and Cariniana micrantha, and one non-commercial species Tachigali vasquezii. We sowed seeds of these species in five microenvironments: log landing, gap-crown and gap-trunk, skidder trail and understory, in a tropical lowland moist rain forest in northern Bolivia. We related seed and seedling performance to light availability, soil compaction, and plant competition. Germination did not differ significantly between microenvironments but survival of germinated seeds for most species was significantly higher (P < 0.05) in the log landing (46–100%) than in the understory (0–7%). After 2 years, the tallest plants were always found in the log landing (119–190 cm) and the smallest in the understory (12–26 cm) caused by a higher relative height growth rate (RHGR) in the log landing (0.003–0.004 cm cm⁻¹ per day) compared to the understory (0.000–0.001 cm cm⁻¹ per day). During the first year RHGR was positively related to canopy openness for all species and negatively to the number of overtopping competitors for three species. During the second year also water infiltration explained observed variation to RHGR. These results show that abandoned log landings and logging gaps are suitable environments for the regeneration of timber species studied. This finding suggests that the removal of competitors in log landings and logging gaps combined with leaving seed trees near these microenvironments or sowing seeds, will improve regeneration of timber species in tropical forests.     

沙质岸黑松海防林更新属于改造技术的研究

应用典型调查与定位试验相结合的方法,探讨了黑松海防林低质低效的形成原因,据其成因将这些林分划分为5种类型,提出了相应的改造意见,并编制出黑松海防林密度管理表。通过更新造林和抚育技术试验,提出了较合理的更新方式,主要有林冠下更新造林、留伐桩萌芽更新、隔行更新造林、人工促进天然更新、带状更新等,其中,带状更新适于在林分条件相对较好的情况下应用,其它几种更新方式较适于低效林的更新改造;采用稀疏林补植、林下种植灌木或绿肥压青、封禁保护枯落物等技术,可有效地改善林分状况。     

Spatial distribution,advanced regeneration and stand structure of Nepalese Sal (Shorea robusta) forests subject to disturbances of different intensities

We investigated the spatial distribution, advanced regeneration and stand structure of five Shorea robusta-dominated forests in 25 1-ha plots subject to disturbances of different intensities. We aim to elucidate the relationships of advanced regeneration and spatial patterns of the tree species with degree of disturbance magnitude. Sixty-seven tree species were recorded in the forest plots; 41 species were found in the least disturbed forests, while only 10 species were found in the heavily disturbed forests. We found 5320 trees with >1.5 cm diameter at breast height, in total, and found that moderately disturbed forests contained the highest advanced regeneration (sapling)/pole densities. No significant differences were observed in stem basal area among forests. The overall stand density changed quadratically across the disturbance gradient. A strong inverse relationship was found between the overall stand density and diameter class in the least disturbed and moderately disturbed forests. Ten species showed variation in their dispersion patterns across the disturbance gradient. Most of the socio-economically important tree species analyzed showed little or no regeneration in the least and most heavily disturbed forests. Individual species showed different responses to disturbance ranging from ‘tolerant’ (Shorea robusta, Lagerstroemia parviflora and Symplocos spp.) to ‘sensitive’ (Trewia nudiflora, Adina cardifolia and Terminalia alata). We concluded that moderate disturbance intensity not only ensures high stand density, but also enhances the advanced regeneration of socio-economically important tree species and affects their dispersion patterns. Future management strategy must balance the consumptive needs of the local community with those of species conservation by allowing regulated access to the forests.     

Structure and regeneration status of mangrove patches along the estuarine and coastal stretches of Kerala,India

This study presents the structural characteristics and regeneration potential of mangrove patches in the estuarine and coastal areas of Kerala, a tropical maritime state in India. Field surveys were carried out at 46 selected sites during August 2015 to May 2016. In each site, the vegetative structure and regeneration status were assessed using the quadrat method. Altogether 219 quadrates were laid out and a total of 13 true mangrove species, belonging to 5 families and 8 genera, were recorded. The total tree density and stand basal area of the study region was1678.08/ha and 20.33 m^2/ha respectively. The low basal areas indicate the reduced structural development in mangroves. Of the 13 tree species, Avicennia constitutes 56%of the total Important Value Index(IVI) and Avicennia officinalis represents 41% of the IVI in Kerala, followed by Avicennia marina(15%), Rhizophora mucronata(15%),Sonneratia alba(8%) Rhizophora apiculata(7%) and Excoecaria agallocha(7%). The diameter at breast height(DBH) in the study area revealed that 47% of the tree species came under the 1–10 cm DBH class. Total sapling and seedling density in Kerala was 2238.35 and 3232.42 individuals/ha respectively. Density of young plants(seedlings ? saplings) was only 31% greater of tree density and varied from 3–63%, which indicates poor regeneration potential. The Maturity index value(MIV) and complexity index(Ic) value of mangroves were 18.30 and 109.81 respectively. However, the low Ic value(\ 10) observed in seven out of ten coastal districts indicated poor structural development of mangroves in Kerala. Therefore, locationspecific conservation and management measures, guided by the knowledge on spatial distribution and habitat requirements of mangrove varieties should be taken to preserve the mangrove diversity of Kerala.