Assessing the Quality of Seedlings in Small-scale Nurseries in the Highlands of Cameroon: The Use of Growth Characteristics and Quality Thresholds as Indicators

In developing countries seedlings are often produced in small-scale nurseries as a means to raise tree planting materials and, provided they are of high quality, these can form the basis for successful forest plantation initiatives. This study uses morphological characteristics to assess the quality of seedlings of three tree species (Persea americana, Cola acuminata and Dacryodes edulis) in the Western Highlands of Cameroon. The growth characteristics and quality indicators of seedlings produced in two nursery categories were compared—three nurseries collaborating with the tree domestication program implemented by the World Agroforestry Centre (Category 1) and three nurseries collaborating with government and non-governmental projects (Category 2). Seedlings produced in nurseries in the first nursery category were found to be uniform in terms of growth characteristics and quality indicators. In the second category, there were relatively higher seedling proportions having measured parameters out of threshold standards for root to shoot ratio and for sturdiness quotient. Significant differences between nursery categories (at α = 0.05) were detected in root collar diameter of C. acuminata and D. edulis and in shoot dry weight of D. edulis. These differences could be attributed to better nursery management as a results of training and technical backstopping received by nursery operators in Category 1. The level of experience of nursery operators in both categories was found to be insufficient and greater exposure to skills and knowledge could enhance the production of high quality seedlings.     

A Critical Overview of Forestry Seedling Production Policies and Practices in Relation to Smallholder Forestry in Developing Countries

This paper reviews forestry seedling production systems in South-east and East Asia and identifies problems with respect to seedling quality, seedling distribution and financial sustainability, and measures which have been adopted or advocated to improve performance in this sector. The paper draws in particular on experience in a series of research projects on smallholder forestry in the Philippines. Some observations are also drawn from the following papers in this combined special issue of Small-scale Forestry. It is found that a mix of public and private sector models are adopted for forestry seedling production, between and even within countries. Often nurseries are set up to provide seedlings for a government-directed expansion in tree planting, and have difficulty surviving once the initial planting purpose is completed. Private nurseries often lack resources, and depend on contracts to supply seedlings for financial viability. Demand tends to be highest for fast-growing species (often exotics), fruit trees, and ornamentals in the case of urban nurseries. Government policies typically favour quantity over quality of the seedlings produced. Considerable scope exists for adopting best or at least improved management practice in seedling nurseries.     

Enhancing Tree Seedling Supply to Smallholders in Leyte Province, Philippines: An Evaluation of the Production System of Government Nursery Sector and Support to Smallholder Tree Farmers

A decentralized seedling production is regarded as the most effective means of providing smallholders with planting materials. However, the sustainability of smallholder nursery operation is constrained by several factors, including the limited availability of germplasm, lack of technical skills and low seedling demand low viability of seedling market. The government nursery sector could complement the weaknesses of the smallholder nursery group but government nurseries are not operating effectively to enhance the availability of high quality seedlings of a wide species base for smallholder forestry. Seedling production in government nurseries is quantity-orientated with low emphasis on the production of high quality planting materials. Germplasm used in seedling production is mostly collected from unselected sources and seedlings produced are mostly of low physical quality. The species selection in government nurseries is heavily based on the availability of germplasm which resulted in the production of a few species which are commonly raised on private nurseries. The duplication of species of most seedlings raised in government nurseries with those produced in private nurseries and the far distance of government nurseries from the villages has resulted in low uptake of seedlings by smallholder tree farmers. For the government nursery sector to become more effective in providing support in the present paradigm of decentralized seeding production, a change from its production system and a broadening of the role it plays is needed. The social mobilization on seedling production as a scheme of implementing the Green Philippines Program has led the Department of Environment and Natural Resources to acknowledge the seedling production activity of private individual and communal nursery groups. This can be an opportunity for organizing the private and government nursery sectors to promote the operational effectiveness of the overall forest nursery industry.     

State of Urban Nurseries in Bangladesh: A Case Study from the North-Eastern Region

The state of urban seedling nurseries in the north-eastern region of Bangladesh is examined with a focus on production and profitability of the enterprises. Twenty-eight sample nurseries out of the 97 nursery enterprises in Sylhet town were selected at random, and operators personally interviewed. It was found that the entrepreneurs are not highly educated though they believed that a basic level of education is required to understand the management of young nursery stock. Labourers of various employment categories work in the enterprises and their wage is determined by their skill, gender and efficiency. Capital and operating costs vary among the enterprises according to land value, production capacity, infrastructure type and workforce size. Production capacity ranges from 10,000 to 5 M seedlings/year with an average 836,000, though actual average production is only 341,000 seedlings/year. The production cost per seedling ranges from Tk. 4 to 50 while sale value ranges from Tk. 10 to 60. The most frequently sold species are Acacia mangium, Swietenia macrophylla, Tectona grandis, Mangifera indica, Litchi chinensis and Cocos nucifera. Nursery techniques and cultural practices adopted by nursery operators depend on the type of species and its silvicultural requirement. Despite some problems, including lack of suitable land for nursery establishment and inadequate level of technical knowledge for high quality seedling management, it seems that production of tree seedlings is a promising profitable small-scale business in the study area.     

Effect of fertilization on growth and ectomycorrhizal development of container-grown and bare-root nursery conifer seedlings

The effect of three levels of fertilizer on thegrowth of three species of containerized-grownconifer seedlings (Pinus contorta, Picea glauca, and Picea mariana) and twospecies of bare-root conifer seedlings (Pinus sylvestris and Larix sibirica),and on the colonization of these seedlings bysix species of ectomycorrhizal fungi (Hebeloma longicaudum, Laccaria bicolor,Paxillus involutus, Pisolithustinctorius, Rhizopogon vinicolor andSuillus tomentosus), was studied. Thegrowth of the seedlings in both container-grownand bare-root nurseries increased as the levelsof fertilizer increased. For better seedlinggrowth and environmental quality it may be possible to reduce the level of fertilizers in commercial nurseries upto 33% by using selected mycorrhizal fungi.Ectomycorrhizal colonization in all seedlingswas not affected by fertilizer levels. Hebeloma longicaudum, L. bicolor, P.involutus, and P. tinctorius formedwell-developed ectomycorrhizae, whereasectomycorrhizal development by R.vinicolor and S. tomentosus was poor.Native mycorrhizal fungi colonizednon-inoculated control seedlings; however,their colonization was always lower than withinoculated fungi.     

Ultrastructural aberrations referring to viruses in the needles of young growth disturbed pine seedlings

Ultrastructural abnormalities in phloem albuminous cells of needles of young pine seedlings from two Finnish nurseries suffering from the growth disturbances of conifer seedlings were studied. Needle samples were taken from growth disturbed seedlings and from healthy looking nursery seedlings as well as from naturally born forest seedlings. The results are discussed in relation to the possibility of virus disease in growth disturbed seedlings. The first trials to observe the viruslike particles from abnormal seedlings will be discussed, too.     

The ectomycorrhizal status of European larch (Larix decidua Mill.) seedlings from bare-root forest nurseries

In this paper, we report molecular investigation of an ectomycorrhizal fungi (EMF) community of European larch (Larix decidua Mill.) seedlings grown in a bare-root nursery. In total, we surveyed 32 nurseries that were each active in supplying planting stocks to restock forests and for afforestation of post-agricultural land. Sequence-based approach was used to identify EMF taxa, quantify EMF richness, and document differences in the relative abundance of individual taxa. We identified seven fungal species that might contribute to the mycorrhizal community structure of 1 to 3-year-old L. decidua seedlings. The species richness in the examined larches varied between one and four fungal taxa, depending on both the nursery stock samples (NSS) and age class of the seedlings. The average was 1.4 for 1-year-old seedlings and 2.3 for 2- and 3-year-old plants. The dominance of Ascomycota over Basidiomycota and the prevalence of two species, Wilcoxina mikolae and Suillus grevillei, as EMF partners were characteristic features of nursery-grown L. decidua seedlings. S. grevillei was the only one basidiomycetes colonized roots of tested seedlings. The rest of the mycorrhizal pool from forest nurseries was typically dominated by pioneer fungal ascomycetes. W. mikolae was the most common mycorrhizal ascomycete present at a high frequency on NSS from both age classes and with very high abundance (average 90%) on 1-year-old seedlings. Some other ascomycetes (Pezizales 1, Pezizales 2 and Pezizales 3) appeared on tested larches at a low frequency, but sometimes in high abundance. Tuber spp. appeared at a low frequency and low abundance. The relative abundance of S. grevillei was positively correlated with the age of seedlings, while W. mikolae was negatively correlated with age. Tuber sp. 1 and 2, Pezizales 2, and W. mikolae were positively associated with the basic soil pH values. However, forward selection of the environmental variables showed that only the age of the larch seedlings contributed significantly (F = 11.45, P = 0.02) to the variance in the ECF community.     

Variation in water relations characteristics of terminal shoots of Port-Orford-cedar (Chamaecyparis lawsoniana) seedlings

We measured water relations attributes of the terminal shoots of 3-year-old Port-Orford-cedar (Chamaecyparis lawsoniana (A. Murr.) Parl.) seedlings that represented its geographic range. Pressure-volume curves were developed and osmotic potentials at full (psi(sf)) and zero turgor (psi(sz)), relative water content at zero turgor, and an index of tissue elasticity (IE) were calculated for 38 families during early, mid- and late summer at an inland nursery, and for 12 of these families during mid- and late summer at a coastal nursery. Compared with other conifer species, psi(sz) was high (-1.4 to -1.5 MPa) and declined in seedlings at both nurseries as the season progressed. Both IE and osmotic amplitude (psi(sf)-psi(sz)) increased during the season. Osmotic potential at zero turgor was lower and osmotic amplitude greater in seedlings at the inland nursery than at the coastal nursery. Correlations of water relations attributes with geographic location of the seed sources were weak and usually not significant. High elevation southern sources exhibited smaller differences in psi(sz) between nurseries than low elevation northern sources. The small differences in water relations attributes among sources and between nurseries suggest that some may be of marginal physiological importance; however, sources that produced larger seedlings appeared to be less desiccation tolerant. We conclude that, when moving genotypes during reforestation, decisions based on patterns in tree size and timing of growth will account for these small differences in water relations.     

Microbial Inoculants for Sustainable Forests

Abstract

Fungal root pathogens are widespread and may cause substantial seedling losses in conifer nurseries. Furthermore, poor seedling survival and growth on reforestation sites results in reduced forest regeneration. Use of microbial inoculants for disease control and plant growth promotion has become an important endeavour. A microbial culture collection of 500 strains was assessed for biological control of fungal root pathogens and/or plant growth promotion of conifer seedlings. Seven of these strains showed significant suppres-sive effects on various soil-bome fungal pathogens. On Douglas fir, two strains, RAL3 and 64-3, reduced disease caused by Fusariumby. 7-42% in repeated growth room assays. The same strains significantly increased healthy stand of white spruce seedlings inoculated with Fusariumand Pythiumin a conifer nursery, and increased the survival of bare-root white spruce seedlings planted on a reforestation site by 19-23%. Both strains also significantly increased new root and total plant dry weights. Strain RAL3 in commercial formulation maintained a viable population of about log 8-9 cfu/ml for over a year when stored at 5°C. Strain survival on seed varied with conifer species. No decreases in bacterial populations were observed on seeds of jack pine or Douglas fir after 37 to 44 days storage at 5°C, but decreases were observed on seeds of white spruce and Scots pine. This study has provided candidate beneficial microbial inocu-lants which offer promise for development of commercial inoculants for the forestry industry.     

欧美国家针叶树容器苗生产与启示

针叶树是芬兰、瑞典、挪威、美国、加拿大等欧美国家主要的商品林树种。容器苗是针叶树重要的育苗类型。与裸根苗比较,容器苗具有育苗周期更短、造林季节可延长、苗木适应性更广、苗木质量更一致的优点。因此,容器育苗成为精准林业发展的必然趋势。为了借鉴欧美容器育苗的技术方法,提高我国容器苗的质量,为我国针叶树容器苗发展提供参考,文中主要从4个方面综述了欧美国家检测与提高苗木质量的方法,即列举了针叶树常用的苗木质量检测指标,总结了育苗容器与育苗基质的改良进展,介绍了养分、水分、光照与温度等培养条件的优化手段,简要概述了容器苗病虫害防控的进展,提出了我国相关树种容器苗生产的启示与借鉴。     

Regeneration of mixed conifer forests under group tree selection harvest management in western Bhutan Himalayas

Group selection tree harvest has been proposed as an ecologically sustainable silvicultural technique in mixed conifer forests of the western Bhutan Himalayas. To evaluate this silvicultural technique, we studied the ecological consequences of a group selection tree harvest in mixed conifer forests by assessing 127 circular plots (71 in logged and 56 in unlogged stands) in two forest management units (FMUs). Tree species composition and diversity were similar between logged and unlogged stands. Seedling density and height growth vary by species and were influenced by logging and microsites, with generally taller seedlings found in the logged versus unlogged stands. Early successional shade-intolerant species colonized logged stands. Seedlings growing on bare soil scarified by harvesting had medium vigour while seedlings growing on bryophyte mats showed good vigour in both logged and unlogged stands. Moist sites with a northerly aspect supported profuse conifer seedling regeneration, compared to sites with a dry southerly aspect. Damage to conifer seedlings from herbivore browsing was minimal. Conifer seedling density and height growth was negatively affected by competition from herbaceous vegetation, most notably Salvia officinalis. Group selection tree harvest in southern dry exposures in spruce-dominated stands is silviculturally unsuitable because it alters tree succession.     

Small-scale forestry development in Leyte,Philippines: The central role of nurseries

This paper presents results of survey research into the role of the forestry nursery sector in the development of smallholder forestry in Leyte, Philippines. Seedling production in the province is basically carried out by three categories of nurseries: individual, communal and the government. Seedlings in the government nurseries are primarily raised for free distribution to landholders but the extension scheme fails to reach the majority of the smallholder farmers. Seedling demand of landholders is mostly catered for by the more numerous and accessible individual and communal nurseries. However, problems of capital outlay, sources and supply of germplasm, technical knowledge in nursery management for both timber and fruit trees and low sales are among the major impediments in the sustainability of small-scale nurseries. Most of the communal nurseries fail to sustain the operation after the withdrawal of supporting agencies. Knowledge on site-species matching is needed not only by small-scale nursery operators but also by the managers of government nurseries. It is concluded that the seedling industry in the province is not well established and there is a need to organise better the overall nursery system so as to improve the availability of seedlings and promote appropriate site and species combinations.     

Can methyl jasmonate treatment of conifer seedlings be used as a tool to stop height growth in nursery forest trees?

A plant's induced defense system can be triggered by the application of the plant hormone methyl jasmonate (MeJA), and recent research suggest that MeJA treatment may become a tool for protection of conifer seedlings against insect herbivory (e.g. by the pine weevil Hylobius abietis). A side-effect of MeJA application is temporarily reduced height growth. This has generally been considered as negative, but in forest tree nurseries this could instead be beneficial since it is commonly desired to stop the growth of nursery seedlings in late summer. Artificially longer dark periods (long nights/short days) are widely used in high-latitude nurseries to terminate height growth and induce freezing tolerance. However, long night treatment requires specialized nursery equipment and are labor intensive. Therefore alternatives are sought after. We compared long-night and MeJA treatments by following the growth of Norway spruce (Picea abies) seedlings throughout one season. The regulatory effect of MeJA on height growth was similar if not even better than that of long nights, i.e. it was terminated faster. However, MeJA treatment also reduced root growth and delayed the development of freezing tolerance. MeJA may therefore not replace long-night treatments, but it could facilitate a more flexible application of long nights by gaining a longer time interval during which this treatment can be used without risking the seedlings growing too large.

     

Performance of <Emphasis Type="Italic">Quercus suber</Emphasis> L. at nursery stage—application of two bio-inoculants under two distinct environments

Key message

Despite the fact that the technique of application of bioinoculants improved the quality of Quercus suber L. seedlings produced in nurseries, these benefits are dependent on the ecological conditions of the site and the composition of the applied inoculum, which interferes with the profile of the local fungal community.

Context

Quercus suber L. plays a key ecological and socio-economical role in the Iberian Peninsula. Symbiotic ectomycorrhizal fungi-ECM are crucial partners of several tree species, and assessing the efficacy of bioinoculants at nursery stage helps devising tools to increase plant resilience.

Aims

The aim of this study was to compare the effects of two inocula formulations of mixed ECM fungi and bacteria on the quality of seedlings produced in two forest nurseries, differing in environmental conditions and forest embedment.

Methods

Quercus suber L. seedlings were inoculated with a commercial product containing Pisolithus tinctorius (Pers) Coker & Couch, Scleroderma sp., and six bacterial species and with a non-commercial fungal and bacterial dual inoculum (Suillus granulatus (L.) Roussel + Mesorhizobium sp.). Biometric and nutritional parameters and morphological quality indexes were determined on seedlings. The ECM community was assessed by denaturing gradient gel electrophoresis and cloning-sequencing.

Results

In both nurseries, the seedling quality index in inoculated was up to 2-fold higher than in non-inoculated seedlings. Plant biomass differed significantly among nurseries. The inoculum influenced the profile of the fungal community. S. granulatus and P. tinctorius persisted for 6 months in the inoculated seedlings.

Conclusion

The nursery ecosystem influenced plant growth. Inoculation treatments increased plant performance; however, the dual inoculum resulted in more consistent improvements of Q. suber at nursery stage, highlighting the importance of inocula selection.

     

Effect of Pre-sowing Moist-chilling Treatments on Seedbed Emergence of Sitka Spruce Seed Infected by Geniculodendron pyriforme, Salt

Burial of seed in moist sand for several weeks during winter(pit stratification), and early sowing have been common practicesin forest nurseries for breaking dormancy of conifer seed. However,in the experiments reported here the emergence of Sitka sprucewas greatly reduced when seeds naturallly infected by Geniculodendronpyriforme, were moist-chilled for 6 weeks in a stratificationpit or in moist sand in a refrigerator at about 4° C. Reductionin emergence was less when seed was refrigerated without sand(naked), and negligible when the seed was treated with Thiramor Captan before chilling. Sowing 6 weeks early produced erraticresults, often giving fewer but larger seedlings. Moist-chillingof seed did not increase total emergence but normally made it1–2 weeks earlier so that the seedlings were larger byautumn. Addition of extra water to the seedbeds did not increaseemergence or growth, even in a dry season.     

Broadleaf seedling responses to warmer temperatures “chilled” by late frost that favors conifers

Climate change includes not only shifts in mean conditions but also changes in the frequency and timing of extreme weather events. Tree seedlings, as the potential future overstory, are responding to the selective pressures of both mean and extreme conditions. We investigated how increases in mean temperature and the occurrence of late spring frosts affect emergence, development, growth, and survival of 13 native and non-native broadleaf and conifer tree species common in central Europe. Three temperature levels (ambient, +3, and +6 °C) and three spring frost treatments (control, late, and very late) were applied. Development responses of first-year seedlings to warmer temperatures were similar in direction and magnitude for broadleaf and conifer species. Stem size also increased with rising mean temperature for most species, though broadleaf species had maximal height advantage over conifer species in the warmest treatment. Sensitivity to frost differed sharply between the broadleaf and conifer groups. Broadleaf survival and stem length exhibited strong reductions due to frost events while conifer species only showed minor decreases in survival. Importantly, more rapid development and earlier leaf-out in response to warmer temperatures were associated with increased mortality from frost for broadleaf species but decreased mortality for conifer species. This research suggests that compositional shifts in the direction of species favored by increasing mean temperatures may be slowed by extreme events, and thus, the occurrence and impacts of such weather events must be acknowledged and incorporated into research and forest planning.     

Commercial viability of conservation and social forestry outreach nurseries in South Africa

Nurseries are risky ventures, even in conducive operating environments. Unlike many of their international counterparts, financial objectives are usually important to South African outreach nurseries, to generate funds for projects and/or to enhance local livelihoods. However, most are situated in low-income areas where residents have limited spending power. This paper examines the commercial viability of ten outreach nurseries from six provinces, with a range of conservation objectives. Management performance was assessed through correspondence and financial ratio analyses. Although seven projects had built up steady markets, this took 5–8 years to achieve, even in intensively funded projects. Only one nursery had achieved a steady annual net profit. The prolonged establishment phases impacted negatively on participants’ livelihoods and project processes. Marketing difficulties included a lack of markets, nurseries being located far from markets, pricing difficulties, inadequate transport and limited marketing communications. Seasonal factors exacerbated liquidity shortfalls. Conservation activities such as greening and rehabilitation programmes provided markets, but medicinal plant nurseries struggled to achieve both conservation and socio-economic objectives, largely through difficulties experienced in providing seedlings at prices that subsistence sector resource users could afford. To achieve commercial viability, outreach enterprises need to adhere to business fundamentals viz. effective planning, management and coordination of resources, monitoring and control. Thorough viability studies are crucial. Alternate natural resource management and income generating strategies need to be evaluated, as a nursery may not be the best means of achieving these. The current Build–Operate–Transfer approach to projects by many supporting organisations is cause for concern as even small-scale projects usually require intensive support.     

Virulence of Fusarium oxysporum and F. commune to Douglas‐fir (Pseudotsuga menziesii) seedlings

Fusarium species can cause damping‐off and root rot of young conifer seedlings, resulting in severe crop and economic losses in forest nurseries. Disease control within tree nurseries is difficult because of the inability to characterize and quantify Fusarium spp. populations with regard to disease potential because of high variability in isolate virulence. Fusarium isolates were collected from healthy and diseased seedlings of Douglas‐fir (Pseudotsuga menziesii) and western white pine (Pinus monticola) from a nursery in Idaho, USA. Molecular markers such as DNA sequences (mitochondrial small subunit and nuclear translation elongation factor 1‐alpha) and amplified fragment length polymorphism were used to identify isolates as either F. oxysporum or F. commune. In addition, diagnostic primers were developed to detect and distinguish F. commune from F. oxysporum. In vitro and greenhouse virulence tests were completed on Douglas‐fir germinants and seedlings. For Douglas‐fir germinants and seedlings, F. oxysporum isolates generally caused less severe symptoms, whereas most F. commune isolates caused mortality through damping‐off. This is the first report of direct evidence that F. commune can cause damping‐off disease on Douglas‐fir seedlings under greenhouse conditions.     

Explaining conifer dominance in Afrotemperate forests: Shade tolerance favours Podocarpus latifolius over angiosperm species

We contrasted the regeneration success of angiosperm canopy species with that of Podocarpus latifolius to test whether this conifer was sufficiently shade tolerant to be favoured on infrequently disturbed and well-shaded sites. Seedling and sapling population structures were measured in several habitats representing a light gradient in warm temperate forest in the Drakenberg mountains of South Africa. The angiosperm-dominated forest was well-shaded (∼5.5% PAR) and lacked ground vegetation. Seedlings of angiosperm canopy species were abundant but the absence of saplings indicated regeneration failure. In contrast, P. latifolius was represented by all size classes beneath the intact canopy indicating continuous regeneration in angiosperm-dominated forest. Angiosperm regeneration was similarly poor in forest gaps, which were dominated by grasses, ferns and vines. P. latifolius entered the advanced regeneration in gaps by establishing in shade before gap formation. The floor of the Podocarpus-dominated forest was less shaded (∼7.5% PAR) than angiosperm-dominated forest and dominated by grass, which suppressed most conifer regeneration. Gaps in Podocarpus forest were more than double the size of gaps in angiosperm forest and dominated by vines and understorey shrubs. There was no clear winner of the angiosperm–conifer contest in Podocarpus forest gaps. Consequently, gaps maintain limited angiosperm diversity in Podocarpus forest. Angiosperm canopy species regenerated continuously in the high light (∼11.5% PAR) thicket environment. Few seedlings of P. latifolius were recorded in the thicket environment. Our findings are consistent with the hypothesis that shaded and infrequently disturbed forest sites favour shade-tolerant conifers over relatively light-demanding angiosperm species. The outcome of the competitive interaction between angiosperm and conifer at the regeneration phase depends on the relative shade-tolerance of associated species.     

Survival of tanoak (Lithocarpus densiflorus) and Pacific madrone (Arbutus menziesii) seedlings in forests of southwestern Oregon

Survival of tanoak (Lithocarpus densiflorus) and Pacific madrone (Arbutus menziesii) seedlings was studied in order to interpret succession in conifer hardwood forests and to determine ways to suppress establishment of these species. Seed protected from rodents and birds, and unprotected seed was sown in clearcuts and in conifer stands 40 to 200+ years old. Second-year survival rates of tanoak seedlings were high (50–70%) in exposed clearcuts and conifer stands. Seed predators appear to be of prime importance in limiting tanoak establishment. Survival rates of Pacific madrone seedlings on the same sites as the tanoak were low (0–8%), and many factors caused mortality. Seedlings of both species grew slowly; after 3 years, average tanoak height was only 6.0 to 14.0 cm, average madrone height 2.0 to 6.0 cm.