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THIS ISSUE AT A GLANCE
Page Article
3 Seed Use Efficiency Meeting
4 Introduction
5Weyerhaeuser - An Integrated Seed-Seedling Supply System
6P o l i c y a n d G e n e t i c R e s o u r c eManagement Directions
7Forest Genetics Council of BC: SeedPlanning Structure
8Seed Use Efficiency: From the Forest tothe Forest
8 Climate-based Seed Transfer
11 Natural Stand Seed Production
11 Coastal Seed Orchard Production
12 Interior Seed Orchard Production
12 Seedlot Production
13Sowing Guidelines, SPAR and SeedUse Efficiencies
14 Upgrading Abies Seedlots
15 Mini-Plug Transplants
16Report on Juniperus Bibliography forISTA Tree and Shrub Seed Committee
17 Upcoming Meetings
17 Recent Publications
CANADIAN TREE IMPROVEMENT ASSOCIATION/ASSOCIATION CANADIENNE POUR L’AMÉLIORATION DES ARBRES
Tree Seed Working Group
NEWS BULLETIN
No. 47 August 2008
SEED USE EFFICIENCY
CHAIR’S ‘ARMCHAIR’ REPORT
Hello and welcome to News Bulletin Number 47.The intent was for the News Bulletin to be an openforum for seed topics and when June rolled aroundDale and I received no contributions outside of ourimmediate circles. That was disappointing as westart flirting with the 25 anniversary of the Newsth
Bulletin and our group. This edition will primarilybe focused on summaries of presentations thatoccurred at a Seed Use Efficiency meeting held inLangley, BC on July 30 and 31. I’ll elaboratemore on the workshop in the News Bulletin itself,but I consider it a success with about 95 peopleattending to learn more about differentperspectives on and activities to increase seed useefficiency from cone collection to sowing [theseed handling system]. Thank you to all of ourspeakers, participants, and those who helped withall of the preparations.
Hopefully the News Bulletin arrives to you beforethe CTIA meeting with our Tree Seed WorkingGroup tour (August 24 ) and workshop (Augustth
25 ). The link to the conference, including papersth
to be presented, can be found at this address:http://www.iufro-ctia2008.ca. Thank you inadvance to Fabienne and others who helpedorganize these events.
As indicated, our December News Bulletin willmark the 25 anniversary of the Tree Seedth
Working Group. The Group formed fromsuccessful seed workshops at both the 1981 and1983 CTIA meetings. Ben Wang served as thefirst interim chair with Bob Farmer, FredHaavisto, Yves Lamontagne and Doug Skeates asexecutive members and George Edwards taking onthe editorial duties of the newly minted NewsBulletin. For those interested in a trip downmemory lane, all past editions of the NewsB u l l e t i n a r e a v a i l a b l e a t :http://www.for.gov.bc.ca/hti/treeseedcentre/tsc/t
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swg.htm.
For our December (25 anniversary) edition, I’mth
again asking for contributions. These can be articlesrelated to seed science & technology, changes in seedpolicy or legislation, meeting summaries, or personalopinions. I’m also keen on any contributionsregarding those no longer with us, but who madesignificant contributions to our field. All articles arewelcome and I’ll ask that people send theircontributions to Dale Simpson before December 10 th
to enable him to edit and assemble them before theholidays.
In British Columbia we have just been through a littlenavel-gazing with a challenge dialogue process (notas scary as it sounds) to address Forest Tree GeneticResource Management and Conservation (GRM).Background information and our final report can bef o u n d a t t h e f o l l o w i n g l i n k :http://www.for.gov.bc.ca/hti/grm/grm_dialogue.htm.One aspect that I have been directly involved with istrying to advance our “cataloguing methods” withregards to our seed bank samples solely dedicated togenetic conservation. I’ll be speaking about this at theTSWG workshop. The information will help usmanage our seed bank and also flow into the nationalCAFGRIS initiative aimed at providing a nationalperspective on genetic conservation by tree species.
I look forward to seeing many of you at CTIA andfinally meeting many international e-mail colleaguesat the IUFRO Tree Seed meeting at Royal BotanicGardens, Kew, England.
Dave KoloteloTSWG Chair
EDITOR’S NOTES
The efficient use of seed was not an issue until seedorchard seed started to become available. As orchardsbegan to produce their first seed crops everybody wasexcited to finally see the “fruit” of their labour. At thesame time this seed was in short supply andreforestation programs had large demands. Adjustingseedling lines to sow as few seed as possible percavity was one way of helping this seed go farther.
Genetically improved seed is expensive to producebut the cost is still a minor component of the overallreforestation costs. By efficiently using seed, lessseed orchard area needs to be planted and managedthereby saving the orchard manager money. Efficientseed use impacts the financial operating line of
nurseries. With costs continuing to rise andrevenue from seedling sales remaining constant orslightly increasing nursery managers must becontinuously innovative in developing ways andmeans of controlling their costs.
Dave put together an excellent program for a twoday Seed Use Efficiency meeting held just a fewweeks ago. I appreciate the response from so manys p e a k e r s in b e in g a b le to p ro v id eabstracts/summaries of their presentations to sharetheir knowledge and ideas with a larger audience.Unfortunately not all speakers were able to submitan article. If you are interested in a particular topicthat is not presented in this News Bulletin I amsure that Dave can put you in contact with thatspeaker.
Another reason for organizing the meeting was tocelebrate the 50 anniversary of the BC Tree Seedth
Centre. This is an impressive facility that is vitallyimportant for the management of BC’s forests.Congratulations!
Also, as Dave pointed out, this is the 25 th
anniversary of the Tree Seed Working Group.Wow! I hope that many of you will considersubmitting an article for the December issue of theNews Bulletin when given a ‘gentle’ nudge.
Dale SimpsonEditor
TREE SEED WORKING GROUP
ChairpersonDave Kolotelo
BC Ministry of Forests and RangeTree Seed Centre
18793 - 32 Avenuend
Surrey, BC V3F 0L5Tel.: (604) 541-1683 x 228
Fax.: (604) 541-1685 E-mail: [email protected]
EditorDale Simpson
Natural Resources CanadaCanadian Forest ServiceAtlantic Forestry Centre
P.O. Box 4000Fredericton, NB E3B 5P7
Tel.: (506) 452-3530Fax.: (506) 452-3525
E-mail: [email protected]
SPAR is the Seed Planning and Registration web based tool that has the following main functions: tree seed and1
vegetative lot registry, service requests, and reporting. See http://www.for.gov.bc.ca/hti/spar/index.htm for moreinformation.
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Comments, suggestions, and contributions for theNews Bulletin are welcomed by the Chairperson andEditor.
SEED USE EFFICIENCY MEETING
In conjunction with our 50 Anniversary as part ofth
the BC Forest Service, the Tree Seed Centre hosted aSeed Use Efficiency meeting in Langley, BC (July 30
and 31). The meeting included 1.5 days ofpresentations followed by a tour of the Tree SeedCentre and a BBQ at our facility. An outline of theprogram is included below. The intent was to startwith a big picture “spaceship” view and zoom inon the activities, challenges, opportunities andcosts throughout the seed handling system. All ofthe speakers did a great job – thank you.
The event attracted about 95 people from breedingand seed orchard programs, cone collectors andprocessors, nursery personnel and a host of
Day 1
Introduction Dave KoloteloSeed Use Efficiency at Weyerhaeuser, USA Dave HodginPolicy and Genetic Resource Management Directions Brian BarberForest Genetics Council Seed Planning Structure Jack WoodsPotential Efficiency Gains in the Seed Handling System Dr. Yousry El-KassabyClimate-based Seed Transfer Dr. Greg O’NeillNatural Stand Seed Production Emile BeginSeed Orchard Seed Production Coast : Annette van Niejenhuis
Interior: Chris WalshSeedlot Production Dave Kolotelo Seedling Production John KitchenSowing Guidelines and SPAR Aids to Efficiency Susan Zedel1
Day 2
Costs: Seed and Seedling Costs Over time Al McDonaldSeedling Specification Perspectives Producer: Norm Livingstone
Purchaser: Stephen JoyceCone Collection Technologies (also equipment exhibits @ TSC BBQ)
Fandrich Cone Harvesters Helmut FandrichSilvaTech Developments Erik Bergvinson / Fred Prufer
Operational Seed Efficiency Gains With Coastal Douglas-fir Bevin WigmoreUpgrading of Abies Seedlots Jamie FarrerBenefits of Thermal Priming and Other Seed Handling Practices Robin DawesMini-plug Transplants Fernando Rey
forestry professionals looking for ways to increaseseed use efficiency. Many more individualsexpressed an interest, but due to our difficulteconomic times were unable to attend. The plan isto present summaries of most talks in the NewsBulletin and also prepare a dedicated websitewhere the presentations could reside. Not allspeakers are able to provide summaries.
There were many good discussions and I think afar better understanding of the various businessesinvolved in the Seed Handling System after themeeting. We will keep on examining opportunitiesfor increased seed use efficiencies and welcomecomments on the subject from attendees andothers who have ideas, practices, or results to
increase seed use efficiency.
Dave KoloteloBC Ministry of Forests and RangeTree Seed Centre18793 - 32 Avenuend
Surrey, BC V3F 0L5E-mail: [email protected]
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INTRODUCTION
The objectives of the Seed Use Efficiency meetingwere:1. To promote activities to increase seed use
efficiency.2. To provide a dedicated forum for the
exchange of information spanning the entireSeed Handling System.
3. To better understand each other’s business,the drivers, and bottlenecks (both financialand biological.
4. To celebrate the Tree Seed Centre’s 50 th
anniversary
The scope of the meeting was the Seed HandlingSystem spanning all activities from conecollection (or cone induction for seed orchardoperations) to the sowing of seed in the nursery.This chain of custody involves a variety ofbusinesses with different drivers and bottlenecks.An appreciation of the entire system is importantas any previous link can impact the quality of theproduct produced. It is also important toappreciate that product value increases throughthe system as ‘investments’ are made to go fromreproductive buds to the seedlings we desire forreforestation.
Conifers are extremely variable organisms andthis diversity is a very good thing for these long-lived species. It is also this variability thatcomplicates direct adoption of seed treatmentsdesigned for low variability agricultural crops.One of the fundamental tenants of qualityassurance is to reduce variability and to someextent seed is part of a sophisticated materialhandling system. The trick is to not remove anygenetic variability as we try to make the systemmore efficient.
I’ll initially provide some broad context to seeduse in BC and then briefly present seedcharacteristics of our major reforestation species.In 2008, provincial sowing aimed to produce 214million seedlings - down substantially from 265million in 2007, but approximately equal to our15-year average. Seed orchard seed accounted for46% of sowing in 2008 and is expected tocontinue to rise to approximately 70% by 2013. InBC, there are approximately twenty one treespecies used in commercial forestry, butlodgepole pine (Pinus contorta) and interiorspruce (Picea glauca x engelmannii) togetheraccount for 78% of the sowing. Adding Douglas-fir (Pseudotsuga menziesii) and western red-cedar(Thuja plicata) to the mix we have the “Big Four”accounting for 93% of provincial sowing.
The germination patterns of these four speciesillustrate the extremely rapid germination oflodgepole pine and the delayed germination ofwestern redcedar (Fig. 1).
Seeds per gram SPG), used to describe seed‘size’, is the other seedlot input, in addition togermination capacity, that translates orders fortrees into grams of seed to withdraw, possiblytreat, and ship to nurseries. Seeds per gramaverages are shown in Table 1 for the Big 4species by genetic class (orchard or wild stand)and a ratio indicating relative difference. Thelargest difference in seed size between orchardand wild seed is found with lodgepole pine.
As we move through the seed handling system itis important to address what the largest sources ofvariability or bottlenecks are. Path analysis issuggested as a good means to address thisquantification. A system that is complicated withdifferent business drivers also will include someunforeseen feedback loops. If anyone has seen the‘gorilla’ video you will understand “you can misssome really big things if you are focussed toomuch in one area” and I think that is worthconsidering. I’ll also offer the following favouritequote “Most mistakes in thinking are inadequaciesof perception rather than mistakes of logic”.Enjoy the meeting!
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Figure 1. Comparison of germination capacity among the four principal tree species planted in BritishColumbia.
Table 1. Average seeds per gram (SPG) for four tree species for seed from seed orchards and wild standsand their ratio.
Species Orchard SPG Wild SPG Orchard/Wild
Lodgepole pine 253 338 0.75
Interior spruce 390 459 0.85
Douglas-fir 87 96 0.91
Western redcedar 751 805 0.93
Dave KoloteloBC Ministry of Forests and RangeTree Seed Centre18793 - 32 Avenuend
Surrey, BC V3F 0L5E-mail: [email protected]
WEYERHAEUSER – AN INTEGRATED SEED-SEEDLING SUPPLY SYSTEM
The subject of efficient use of seed, in particularA class seed, has arisen twice at Weyerhaeuser.The first time was in the early 1980’s, with the
initial production phase of our seed orchards,when supply was limited and the goal was tomaximize the breadth of acreage that we wereable to impact with genetically improved stock.When our seed supply capacity exceeded ourrequirements, the emphasis refocused on seedlingquality and order volume, frequently at theexpense of efficient use of seed. This wasparticularly true as we initiated development ofnew stock types, where the growing processeswere as yet poorly defined.
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The increasing use of A class seed and itsincreased cost structure, necessitates that growingfacilities review their growing processes forimprovements which will lead to more efficientuse of seed. Seed cost, as a component of totalseedling cost, is a significant proportion even inan internal supply system and in particular whenan end-user is purchasing A class seed. Thiscomponent of total seedling cost is oftenoverlooked when the seed is supplied to a contractgrowing facility by the end-user.
All seed producers, growers, and foresters striveto do the very best job possible. Each have theirown metrics of success, but sometimes they donot include the success of the next in linecustomer. For the seed producer it is volume ofcones harvested and seed yielded, the growerachieving order and seedling specification targets,and the forester achieving a target number of trees/land unit and planting cost. These are all goodmetrics, but are intermediate or componentmetrics. The absolute measurement of success isthe right genetics delivered to a specific unit andsurvival of the seedlings to free to grow, at theleast possible cost. Only then will forestryoperations achieve a return on investment thatwarrants continued investment, particularly in theprivate sector
At Weyerhaeuser each component of the supplysystem has its intermediate metrics, but we arecollectively held accountable to each other toachieve successful plantation establishment. Eachyear seed producers and seedling growers visiteach internal customer to review the successesand failures of the last and previous plantingseasons. In cooperation with each other, andincluding the nursery and silvicultural scientists,courses of corrective actions are developed toaddress weak performance. We communicateacross the spectrum of the delivery system.
Corrective actions can and do span across eachdiscipline and frequently are articulated fromoutside the discipline. We have control over ourseed, both supply dependability and genetics. Weknow more about the seedlot attributes thangermination, but also its growth habits and frostsusceptibility. Growth curves and yields aretracked by seed type and growing prescriptionsand growing locations are modified tocompensate. We have developed focusedphysiological requirements for stock types andplanting environments. We have achieved andbeen able to achieve this because we operate as asystem, each held accountable to the other. Wehave achieved this through good communication.
Dave HodginSeed Production ManagerWeyerhaeuser Co.Western Timberlands7935 Hwy 12 SWRochester, WA 98579E-mail: [email protected]
POLICY AND GENETIC RESOURCE MANAGEMENT DIRECTIONS
or Who moved my seed?
There are a number of provincial issues andpolicies influencing, or will influence, seed use inBC. These include state of the BC forest sector,the mountain pine beetle (MPB) epidemic, climatechange, and policy responses to them.
A weak US housing market, strong Canadian $,and increased energy costs have reduced softwoodlumber sales in 2007 (-24% compared to 2006 and-36% compared to 2003). As a result, only 80% ofthe provincial annual allowable cut (AAC) of 80million m is being harvested. Reduced harvest3
levels equate to fewer areas being reforested.Seedlings requested for planting in 2007 were 270million. However, requests for sowing in 2008were only 214 million seedlings. Reforestation ofareas denuded by the MPB and planting forincreased fibre production through governmentfunded programs such as Forests for Tomorroware, however, expected to increase planting andseed use over the next five years. Issuance of newtenures, to communities and First Nations, arealso increasing the number and diversity of seeduses. As a result, there will be continued demandfor high quality seed, but with increased pressureto reduce costs and optimize seed use efficiency.
The BC Government has introduced aggressivegreenhouse gas (GHG) emission reduction targets.They have also committed to achieve net zerodeforestation (conversion of forestland to otheruses, e.g., housing) in BC by 2012. The role offorests in offsetting GHG emissions under aregional cap and trade system has yet to bedetermined. Managing forests for carbon storageand biofuels is being considered and these willlikely become new forest values.
Managing forests in response to climate change(adaptation) is also a focus of the Ministry ofForests and Range (MFR) under the Future ForestE c o s y s t e m I n i t i a t i v e ( F F E I )http://www.for.gov.bc.ca/hts/Future_Forests/ .
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Changes to species selection guidelines and seedtransfer standards are being examined so plantedforests may be better adapted to future climates.Research in assisted migration is underway withthe intent of introducing a new climate-based seedtransfer system within 3–5 years (see O’Neill’ssummary). In the interim, minor changes to theelevational transfer limits for several species arebeing considered for the fall of 2008. Informationand updates regarding changes to seed transferw i l l b e p o s t e d a t :http://www.for.gov.bc.ca/hti/climate_change/index.htm.
Changes to species selection and seed transfer willhave significant impacts on seed supply and useover the coming years. Increasing speciesdiversity in plantations may increase seed demandfor broadleaf species. Tree breeding programs andseed orchards may need to shift focus andlocations as the climate warms. Seed crops inorchards and wild stands may also face increasedincidence of insect and disease damage. Seedownership and inventories will also need to moveas the seed suitable for one operating area shiftsover time. The utility of some seed sources willincrease and the utility of others will diminish.
In response to the state of the forest industry,MPB, climate change, and other drivers, theForest Genetics Council of BC (FGC), TreeImprovement Branch, and Research Branchundertook Challenge Dialogue with membersTM
of the genetic resource management (GRM)community of practice and stakeholders in2006–08. The purpose of this dialogue was tocreate a collective vision and strategy formanaging and conserving BC’s forest tree geneticresources. This goal was accomplished andobjectives for the 3 main components of GRM(Conservation, Resilience, and Value) wereidentified. The final GRM report can bed o w n l o a d e d a t :http://www.for.gov.bc.ca/hti/grm/grm_dialogue.htm . This report will guide the establishment ofthe FGC’s next 5-year strategic plan, which willinclude performance measures for the identifiedobjectives.
In changing times and climes, seed demand anduse will continue to change. To avoid surprises,take note of the sage advice offered by StephenJohnson in his parable Who moved my cheese? Change happens - they keep moving the seed.Anticipate change - get ready for the seed tomove. Monitor change – check the seed often soyou know when it is getting old. Adapt to changequickly - the quicker you let go of old seed, thesooner you can enjoy new seed. Change - move
with the seed. Enjoy change! - savor theadventure and enjoy the new seed! Be ready tochange quickly and enjoy it again & again -keep moving the seed.
Congratulations to the Tree Seed Centre incelebrating 50 years of excellence in cone andseed services.
Brian BarberTree Improvement BranchMinistry of Forests and RangePO Box 9518 Stn. Prov. Govt.Victoria, BC V8W 9C2E-mail: [email protected]
FOREST GENETICS COUNCIL OF BC: SEED PLANNING STRUCTURE
Provincial objectives set by the multi-stakeholderForest Genetics Council of British Columbia(FGC) call for 75% select seed use by 2013 and1
for an average genetic worth for growth of 20%by 2020. With annual provincial plantingaveraging about 225 million seedlings per yearacross over 14 species, priority setting and seedplanning are significant tasks.
The planning process involves a series of steps.Initially, there is a process for setting prioritiesamoung various seed planning units (SPU). For2
SPUs that meet criteria for breeding and seedorchard investments, seed needs within each zoneare forecast. Historic orchard production curvesare developed, and based on these, total orchardsize needs are predicted. Seed use and orchardproduction figures are tracked and presented
Select seed is seed from trees that have been1
genetically selected from natural populations,including orchard seed from parents with knownand positive breeding values and seed fromprovenances with known superior traits. No seedused in BC is genetically modified.
A seed planning unit is a unique combination of2
species, seed zone, and elevation band which isused for seed planning and which have specificbreeding and seed orchard populations. Anexample would be Douglas-fir in the maritimeseed zone under 700 m elevation.
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annually to aid orchard managers in thedevelopment of specific orchards and to helpbroader planning to ensure provincial objectivesare met. Breeding investments are guided by SPUpriorities and by orchard development timing.Orchard roguing decisions are made by individualowners, but cooperative planning and discussionsprovide them with the information they need tomake informed decisions. Provincial financialsupport for boosting seed orchard quality (seedlotgenetic worth) and for adjustments to meet FGCobjectives provide added incentive for orchardoperators to undertake management that willultimately support FGC objectives.
In the multi-stakeholder system in BC, orchardsare owned and operated by both the public andprivate sectors. Providing good information onseed needs, on annual production and on forecastproduction, is a key element to ensuring opendiscussion and cooperation among participantsand to the development of a comprehensive seedproduction system that meets broader stakeholderobjectives.
Jack WoodsProgram ManagerForest Genetics Council of BC3370 Drinkwater RoadDuncan, BC V9L 5Z2Email: [email protected]
SEED USE EFFICIENCY: FROM THE FOREST TO THE FOREST
Seed utilization is viewed as an integralcomponent of an inter-connected treeimprovement delivery system. Investigating anycomponent of the system, such as seed utilization,must be viewed holistically (i.e., it cannot bedetermined or explained by its component partsalone; instead, the system as a whole determines,in an important way, how the parts behave). Thus,efficient seed utilization is affected by thephenotypic selection of superior individualsforming the breeding population; the intricacies ofbreeding à testing à genotypic selection ofproduction populations’ (seed orchards) parents;seed crop management practices (cone harvesting,processing, seed handling, storage, and pre-treatments; and ends with the production ofseedlings for reforestation). Changes in geneticgain and diversity were monitored throughout the
system, indicating that the interaction betweengenetics (the magnitude of genetic control overreproductive phenology and output, germinationspeed, dormancy and aging) and managementpractices (e.g., individual vs. bulk seedharvesting, single vs. multiple sowing) couldimpart significant unintentional directionalselection where genetic gain and diversity couldbe drastically affected.
Yousry A. El-KassabyFaculty of ForestryUniversity of British ColumbiaVancouver, BC V6T 1Z4E-mail: [email protected]
CLIMATE-BASED SEED TRANSFER
Background
A well designed seed transfer system maximizesplantation productivity and wood quality, ensuresthe capture of genetic gains, and minimizes therisk of maladaptation due to pests, disease andclimate change by ensuring that trees are welladapted to their planting location.
A revolution in the field of genecology relating tothe development of new climate models,geographic information systems (GIS), theavailability of mature provenance data, and newstatistical techniques make it possible to developan improved seed transfer system. A new climate-based seed transfer (CBST) system will greatlyenable effective implementation of assistingmigration of seed (i.e., planting seed adapted tofuture climates), which has been widely regardedas a key climate change adaptation strategy inforestry.1
Research Branch has initiated a project to developa CBST system that will identify seedlots that arebest suited climatically to each plantation over thecourse of the rotation. The system will beoperationally simple, will apply to both selected(class A) and wildstand (class B) seed, and will bewell suited for implementing measures to mitigatethe impacts of climate change.
A small degree of assisted migration can be1
accommodated within the current seed transfersystem. In September 2008 Research Branch willrecommend minor changes to the current systemto encourage assisted migration.
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Methods
Five fixed-zone seed transfer systems weredeveloped and compared with BC’s current Bclass seed transfer system to assess the degree ofadaptation and deployability that each systemwould provide. Five zonation systems werecreated, each dividing British Columbia into 12climate zones. The zonation systems were basedon: mean annual temperature (MAT), MAT andmean annual precipitation (MAT x MAP), twoprincipal components (PC) which consolidatedeight climate variables, two principal componentswhich were clustered (PC cluster) using ahierarchical clustering procedure to minimizeclimatic variation among clusters, and BC’sforested biogeoclimatic zones. The MAT x MAPzonation system is illustrated in Fig. 1.
The level of maladaptation (and associateddisease, pest, stem deformation, and growth
losses) associated with seed transfer increaseswith climatic transfer distance. Therefore, toevaluate the level of adaptation that would beinherent in each zonation system, a large numberof hypothetical seed transfers was created withineach zone of each system and the climatic transferdistance determined for each transfer. Climatictransfer distance was then averaged over eachzone and zonation system. To assessdeployability, the areal extent of each zone ofeach system was determined using a geographicalinformation system.
Results and Discussion
Climate transfer distance of seed transfers wassubstantially shorter in the zonation systems thatwere based on MAT x MAP, PC, and PC clusterthan the systems based on MAT, biogeoclimaticzones, or the current class B zonation system (Fig.2).
Figure. 1. An example of one of the five climate-based seed transfer systems examined. Twelve fixed-zoneclimate zones were created for British Columbia on the basis of mean annual temperature (MAT)and log of mean annual precipitation (logMAP).
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Figure. 2. Results of analysis to estimate the level of adaptation expected to be associated with seedtransfers from five climate-based seed transfer systems and the current class B seed transfersystem in British Columbia. Climate transfer distance is used as a surrogate measure ofmaladaptation.
Deployability was considerably greater for all fivezonation systems compared with the current classB zonation system (Fig. 3). These results suggestthat a new seed transfer system based on fixedzones developed from MAT x MAP, PC, or PCclusters would provide substantial improvementsin adaptation and seed deployability. In addition,these systems would facilitate the implementationof a system of assisted migration that could beincorporated incrementally and without the needto revise zone boundaries.
Research Branch staff of the Ministry of Forestsand Range intend to complete analyses required topropose a new climate-based seed transfer systemby mid 2009. Tree Improvement Branch will thenreview and implement the recommended system.To minimize disruption in seed planning forlicensees, a “roll-out” period (3–5 years) is beingconsidered to provide time for stakeholders toadjust seed inventories.
Gregory A. O’Neill and Nicholas K. UkrainetzMinistry of Forests and RangeResearch Branch3401 Reservoir RoadVernon, BC V1B 2C7E-mail: [email protected]
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Figure. 3. Results of an analysis to estimate the level of deployability expected to be associated with seedtransfers from five climate-based seed transfer systems and the current class B seed transfersystem in British Columbia. Deployability is the spatial extent (km ) to which each seedlot can2
be transferred.
NATURAL STAND SEED PRODUCTION
The presentation reviews most aspects of Class“B” cone collection including: legislation, naturalseed planning zones, lodgepole pine (Pinuscontorta) biology, mountain pine beetleconsiderations, and operational activities withcosts leading to SPAR registration. The focus ison lodgepole pine collections within the PrinceGeorge Business Area including defining manychallenges and solutions for consideration inpreparing and undertaking a cone collectionprogram. A draft process, currently in use withBCTS Prince George, is provided and can be usedto develop a cone collection program fromharvesting to collections. BCTS Prince George iscurrently collecting over 20 years of lodgepolepine seed in each seed planning zone, includingseed from other species supporting BC TimberSales meeting legal reforestation obligations.
Emile BeginTSP Practices ForesterMinistry of Forests and RangePrince George District Office2000 S Ospika Blvd.Prince George, BC V2N 4W5E-mail: [email protected]
COASTAL SEED ORCHARD PRODUCTION
The expert staff at the coastal seed orchardproduction facilities deliver orchard seed of highgenetic quality and good viability. Productionreflects the status of breeding programs and meetsm o s t c o as ta l n eed s . L o n g -te rm p l animplementation will address current shortfalls.Costs of orchard seed are significantly greaterthan those of wild seed collections because ofcrop management inputs and cost-averaging thatincludes good and poor crops.
Orchard sites are selected for spring drought and
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low background pollen levels. Grafting selectedparents, planting the orchard, and tending thetrees to cone-bearing size requires irrigation,fertilization, and pest and competition control.Cone crops are induced by water stress, girdling,pruning, and hormone treatments. Seed set isimproved with supplemental mass pollination.Timely cone harvest and curing, followed by seedextraction and seedlot registration results in seedfor regeneration programs.
To meet the Chief Forester’s Standards for SeedUse, effective population size and weightedaverage genetic worth of the parents contributingto the lot are calculated. Male contributionestimates employ pollen data, and femalecontribution calculations use harvest measures.
Pesticides, including hormones, are infrequentlylabelled for use in conifer seed orchards. Pestcontrol and induction options are thereforelimited. Drainage is a challenge at some orchardsites, affecting orchard tree survival.
Advanced generation orchard seed is listedsurplus in SPAR for low elevation westernredcedar (Thuja plicata), low elevation Douglas-fir (Pseudotsuga menziesii), low and highelevation western hemlock (Tsuga heterophylla),and blister-rust tolerant western white pine (Pinusmonticola). High elevation Douglas-fir andweevil-resistant Sitka spruce (Picea sitchensis)will come on stream as orchard productionincreases. United States orchards supply seed forlow elevation Douglas-fir needs.
Can high-value seed in short supply at presentdeliver more seedlings? Can client cost beunaffected, but the nursery price increase and theseed price decrease with the provision of less seedfor seedling orders? High-value seed with highgermination rates provides opportunity fornegotiations among nursery service providers andclients.
Annette van NiejenhuisWestern Forest Products Inc.8067 East Saanich RoadSaanichton, BC V8M 1K1E-mail: [email protected]
INTERIOR SEED ORCHARD PRODUCTION
Seed orchards deliver improved seed forreforestation. Seed orchard efficiency in itssimplest terms is concerned with how we canproduce seed as economically as possible. Fivefacets are discussed regarding how seed orchardscan affect the efficiency of the entire seedhandling system. They are: orchard planning anddesign, maximizing cones produced per orchardtree, maximizing seeds per cone, optimizing conecondition to maximize seed recovery at extraction,and maximizing germination capacity of seedproduced. Orchard planning attempts to matchorchard production to seedling needs. Cones pertree, seeds per cone, and seed recovery areaffected by orchard management practicesincluding cone induction, pest control, culturaltreatments, and cone handling. Germinationcapacity significantly determines seed useefficiency in nurseries. Some observations arepresented on how timing of collection relates togermination capacity.
Chris WalshSeed Orchard ManagerKalamalka Seed OrchardsMinistry of Forests and Range3401 Reservoir Rd.Vernon, BC V1B 2C7E-mail: [email protected]
SEEDLOT PRODUCTION
Seedlot production involves the steps of cone andseed processing, seed testing, registration, storage,pre-treatment, and distribution for seedlingproduction. In British Columbia the previouslymentioned underlined items are consideredstewardship responsibilities and costs notforwarded to clients. Cone and seed processingand seed pre-treatment are offered on a costrecovery basis. Quality Assurance (QA) will beemphasized and is defined as “the evaluation,monitoring, and management of information andpractices related to activities in the Seed HandlingSystem”. Our QA foundations are:1. Avoid physical contamination (debris).2. Avoid genetic contamination (between
seedlots).3. Information management (organization).4. Handling a perishable product (care).
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Considerations regarding quality begin at thestage of pre-collection evaluation when crop sizeis estimated to plan for required resources, thepresence of pest problems is determined, and thematurity level assessed to ensure cones arecollected at the optimum time. Interim fieldstorage is important to reduce cone moistureslowly in most crops, but serotinous lodgepolepine (Pinus contorta) cones can be shippedimmediately. Cutting tests or seed anatomy testsare important tools for assessing maturity, quality,and determining if pests are an issue.
Cone processing consists of: 1) removal of seedalready released from cones, 2) kilning, for mostspecies, and 3) separation of seed from conesthrough tumbling. Species containing resinvesicles (Abies spp., western redcedar (Thujaplicata), and hemlock (Tsuga heterophylla)) arecurrently not kilned, but allowed to dry under coolconditioning so that the cone scales will flex.Lodgepole pine is kilned at a peak temperature of60ºC while all other species are kilned at a peaktemperature of 40ºC. The stage of tumbling iscritical as it is the separation of seeds from cones,so monitoring is important to ensure all viableseeds are removed.
Seed processing starts with scalping to removedebris that can be abrasive, add moisture, orcontain pathogens. This stage also greatly reducesthe volume of material subsequently handled.Dewinging is performed on all species exceptw e s t e r n r e d c e d a r a n d y e l l o w - c e d a r(Chamaecyparis nootkatensis). For pine andspruce species, wet dewinging is employed as thewing connection is quite weak and wetting allowsfor efficient release of the wings from the seed.The remaining species have a stronger wing-seedconnection and wings are removed solely throughmechanical forces, although small wing fragmentsmay be retained compared to wet dewingedspecies. Wings are removed by vacuum duringthe process and the process shifts from removingdebris to removing non-viable seed during finalcleaning. This can occur via pneumatic separatorsor the gravity table, but both separate seed intothree fractions based on specific gravity.Equipment calibration and decisions regardingseed to include/exclude in seedlots is supportedby cutting tests and seed evaluations. In contrastto other seed processes, some seed may requirefinal cleaning multiple times to ensure that viableand non-viable seeds are separated. Once finalcleaning is completed the seedlot can be blendedand then sampled for testing.
Seedlot sampling is conducted in accordance withISTA sampling guidelines. Moisture content isfirst tested and if between 4.0 and 9.9% theseedlot can then be placed into long-term storage
at -18°C. Seedlot purity is then determined andmust be above 97% for registration. Moisturecontent and purity are legislated requirementsunder the Chief Forester’s Standards for Seed Usein BC. The seed weight test is performed and incombination with seedlot purity the variable seedsper gram is calculated [seeds per gram = purity%/ weight of 100 seeds]. Germination tests are alsoperformed and the germination capacity and seedsper gram are the variables used to translatebetween seed and seedlings. Germination isretested at intervals in relation to the speciesdeterioration rate, so a rapidly declining specieslike western redcedar is tested every 18 months,but a species with good storage longevity likeSitka spruce (Picea sitchensis) is retested every 48months.
In addition to the standard tests described abovefor seedlots, there are a variety of QA testsperformed on a subset of a seedlot. These includemoisture content of unkilned seed, pelletassessments, germination testing of sowingrequests, and returned seed.
Seedlot registration occurs following testing,confirmation of seedlot weight, and for seedorchard crops, calculation of the Genetic Worth(GW) and effective population size (Ne). Forseedling production, seed pretreatments areequivalent to those used in testing. Activitiesinvolved in seed preparation are: 1) scheduling(nursery sow date is what we work back from), 2)manage changes, 3) withdraw seed, 4) prepareseed in one of the following ways – soak andstratify, pellet, or send dry to nursery, 5) monitorduring stratification, especially with speciesrequiring long stratification periods, and 6) shipseed to the nursery.
Dave KoloteloBC Ministry of Forests and RangeTree Seed Centre18793 - 32 Avenuend
Surrey, BC V3F 0L5E-mail: [email protected]
SOWING GUIDELINES, SPAR AND SEED USE EFFICIENCIES
The Seed Planning and Registry web application(SPAR) contains the registry of all seedlots fromcommercial forest species that are collected inBritish Columbia. Seedlots are registered
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following current BC Ministry of Forests andRange legislation and policy (Chief Forester’sStandards for Seed Use). Seedlots are then used toproduce seedlings for reforestation of Crown land.
For each seedling request entered in SPAR, aseedlot is selected for the request using defaultsowing guideline calculations. Sowing guidelinesare a set of calculations that convert the number ofseedlings requested by forest professionals to thequantity of seed that needs to be removed fromlong-term freezer storage.
Sowing guidelines have evolved since the 1980’swhen very basic sowing rules existed (2, 3 or 4seeds per cavity, and 1 seed/cavity for Class Alots) with > 90% germination, along with oversowfactors. In 1996 a “Sowing Guideline Task group”was formed and recommended that the differencebetween Class A and B rules be removed and thatseeds per cavity and sowing correction factors beadjusted.
Sowing guideline changes in 1999 streamlined theallocation of seeds to correspond closely togermination capacity changes and fractionalsowing was introduced (see Extension Note Vol3 No 4 ). In 2001 the sowing guidelines refinedthe calculations of “seeds per seedling”.Extension Note Vol 5 No 2 describes sowingguidelines and the calculation method. In 2007,reductions in seeds per seedling were made forinterior lodgepole pine (Pinus contorta var.latifolia) only (see SPAR website).
The general business and information flow forseed and seedlings in SPAR is:1. Seedlots are registered on SPAR and stored at
the Tree Seed Centre.2. Seedling Requests are entered by agencies (
e.g., licensees, BC Timber Sales, FFT,woodlots) for species, seedlot, quantity, stocktype, planting year/season. Grams of seedrequired for each request are calculated usingdefault sowing guidelines, based on seedlotgermination capacity, seeds per gram, andamount of seedlings requested. The SPARcalculations are used by many forestcompanies and nurseries, however, someadjust the grams of seed required (usuallydownwards) based on past experience orlimitations placed on high-value seed by theowner.
3. A nursery can also change sowing dates forrequests assigned to them to stagger the timethat seed will arrive at the nursery for sowing.
4. Information flows between SPAR andCONSEP (local Tree Seed Centre system).
5. Tree Seed Centre does seed withdrawal,preparation (some nurseries do stratification)and ships seed to nurseries based on sowing
dates.6. Nurseries receive seed and sow in specified
container type on appropriate sowing dates.
In terms of seed use efficiency, the quantity ofseed saved by reducing grams for seedlingrequests is measured by the difference betweenseedlings requested and seedlings calculated.
For the 2008 sowing year, for all species, 214.4million seedlings were requested. The gramamount calculates to 188 million seedlings, soseed for the potential of 26.4 million seedlingswere saved.
For lodgepole pine only, in 2008, 99.1 millionseedlings were requested and 81.5 millioncalculated. Therefore, 17.6 million potentialseedlings were saved.
Economic incentives to reduce seed quantities forrequest agencies are obvious as it reduces theirseed costs, but economic incentives for reducinggrams at the nursery are not as straight-forward.Discussions (negotiations) between the customerand nursery are encouraged and will result ingreater seed-use efficiencies. Nurseries areencouraged to calculate the actual grams of seedrequired for their seedling requests based on theirown practices and experience.
Thank you to those nurseries and seed ownerswho reduced grams of seed for seedling requestsand saved valuable seed, which also reduced theamount of seed returned to the Tree Seed Centre,saving resources.
Susan ZedelTree Improvement BranchMinistry of Forests and RangePO Box 9518 Stn Prov. Govt.Victoria, BC V8W 9C2E-mail: [email protected]
UPGRADING Abies SEEDLOTS
Overview
This topic is directly tied to the discussions wehave been having on the need to better utilize ourseed resources. Whereas the overall reduction ofcertain types of seed is required to guarantee thelong term sustainability of our industry, theupgrading of Abies seedlots is a good example of
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how nurseries have been trying to make the bestuse of the seed they get for upwards of 15 years(the length of time we have been upgrading).Nurseries are currently expending a large amountof time and money working on better utilizingtheir seed resources, even on minor crops, such asAbies.
Abies Production in BC
Total production of forest seedlings in BC for2008 was 214 million. Total production of Abiesseedlings was 2.2 million (approximately 1% oftotal grown).
Reasons for Upgrading
The average germination capacity of amabilis fir(Abies amabilis) and subalpine fir (Abieslasiocarpa) is 60%. With the Ministry sowingrules that gives us 4.3 seeds per cavity. This isoperationally very difficult to accurately sow. Theprocess of upgrading was developed to remove asmuch of the unproductive seed as possible tobetter facilitate the sowing and growing of thecrop (4.3 seeds per cavity can often be reduced to3.5 seeds per cavity by upgrading). Upgradingremoves empty seeds and leaves less, but moreproductive seed that can be better distributed inthe blocks during sowing. Better distributed seedleads to more uniform germination, lesstransplanting, and a more consistent crop.
Limitations to the Upgrading Process
Upgrading cannot remove all seed issues. Emptyseeds are easily removed in the process, but thefollowing can still be present after the upgradingis complete: insect damage, immature seed,mechanical damage, and disease.
Upgrading Process
Planning is critical to the success of the operation.PRT is producing just over 950 000 Abiesseedlings in 2008 (half of the total Abiesproduction in the province). There were roughly123 kg of Abies seed that needed to be upgraded.All of this to produce trees for less than half of1% of the total trees grown in 2008.
Upgrading must be planned so that the process iscomplete and seed is at the desired nursery in timefor it to be sown. Equipment needs are minimal.Seed is soaked for 1–8 hrs in clear Rubbermaidbins. As seed sinks, the percentage of filled seedsis checked to determine if the process is complete.
Once the percentage of filled seed remainingfloating is less than 10%, it is skimmed anddiscarded. The total seeds available is recalculatedand a new seeds per cavity number is generatedfor sowing.
Jamie FarrerProduction SuperintendentPRT Campbell River nursery3820 Snowden RoadCampbell River, BC V9H 1P5E-mail: [email protected]
MINI-PLUG TRANSPLANTS
Mini-plug transplants are recognized to be one ofthe best production systems for optimizing seeduse efficiency. In container conifer seedlingproduction, this system allows nurserymen tomaximize seed usage by single-sowing anyseedlot, regardless of its germination capacity,into mini trays and by transplanting them intobigger containers to produce the requestedstocktypes. Other benefits this system offersinclude reduction of heating costs by increasinggreenhouse space efficiency, and by reducingthinning and manual transplanting operations.
The implementation of the mini-plug technologyinto conifer seedling production at PRT-Pelton(formerly Pelton Reforestation) however, hastaken several years to develop. Adaptation ofexisting technology used in the horticulture sectorhad to overcome limitations such as compatibilitywith the Styroblock container system and the lackof cohesiveness of mini-plug conifer seedlings towithstand handling through the different phases ofproduction. At PRT-Pelton we use a heat sensitivefibre (Fibreneth®) blended with Coir medium tofill the trays and pre-form the mini plugs beforeseeding.
A successful mini-plug transplant program startswith accurate single-sow seeding of mini trays tooptimize use seed efficiency. For optimalgermination and early growth of mini-plugseedlings, we have set up a “growth chamber”with insulated walls and supplementary lighting atphotosynthetic levels of intensity. Theseenvironmental conditions promote the productionof compact seedlings to facilitate the subsequentphases of mini-transplants. Depending on thegermination capacity of the seedlot, the mini-trayscan have a number of blank cells. As the
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machines transplant every cell from the mini-trayto the destination Styroblock, the blank cells areremoved and replaced (gapped-up) by other mini-seedlings. This operation is accomplished byrunning the mini-trays through scanningequipment to blowout the empties and throughanother scanner that directs the robotic arm to gapthe blank cells with seedlings from another mini-tray to produce a 100% filled tray. Gapping themini-trays makes the transplanting operation moreefficient. Mini-plug trays can also be used tomanually backfill empty cavities in conventionalsingle-sown Styroblocks, reducing transplantingshock and producing a more uniform crop.
Early results and experiences of implementingthis technology into seedling production presenteddifferent challenges. Optimal conditions ofmedium density in the mini-plug trays forgerminant radicle penetration, optimal growingconditions to promote compact-seedling growth inhigh density trays, algae, and liverwort control toeliminate scanning interference for gapping up,and customer’s acceptance of transplanted stockwere some of the difficulties to overcome.Successful results of mini-plug transplants includespecies like spruces, Douglas-fir (Pseudotsugamenziesii), western larch (Larix occidentalis),western hemlock (Tsuga heterophylla), andwestern red cedar (Thuja plicata). Using mini-plug transplants in 2008 has allowed us toproduce 80 000 to 300 000 extra seedlings ofspruces, western larch, and Douglas-fir over theconventional direct-seeded production system.
There are great advantages of using mini-plugtransplants in the production of conifers such as:efficient use of seed, 100% cavity fills onstyroblock containers, lower thinning costs,reduction/elimination of manual transplanting,and reduction of heating costs. However, there aresome limitations of the system that can discourageits implementation such as: high capital cost,limited production capacity (slow process), higherproduction risks from its high seedling density ina small growing area, precise schedulingrequirements of the different stages of production,and limited stocktype availability. Moreover, theincreasing trend for the demand of smallerstocktype seedlings makes the mini-plugtransplant system less effective as a powerful toolto increase seed use efficiency.
Fernando ReyCrop Production Manager PRT – PELTON 12930 203rd StreetMaple Ridge, BC V2X 4N2E-mail: [email protected]
REPORT ON Juniperus BIBLIOGRAPHY FOR ISTA TREE AND SHRUB SEED
COMMITTEE
The purpose of the project for the InternationalSeed Testing Association was to provide an up-to-date bibliography of all Juniperus seed researchfor people in underdeveloped and developednations to access easily on the internet or throughword processing software. Mostly articles relatingto seeds are included in the bibliography. Othercitations on fire and management may be includedfor some species.
Beti Piotto was the leader of the project. USDAForest Service National Seed Laboratorypurchased Procite software and Jill Barbour typedor copied the abstracts into Procite Software. Betireceived assistance from colleagues within Italy tosearch several databases for journal articles onJuniperus propagation.
Juniperus is an extremely ecologically importantgenus in many parts of the world. Seedpropagation is quite difficult for many Juniperusspecies because the seed can have different kindsof dormancy. To propagate the speciessuccessfully it is important that people haveinformation to aid them in germinating the seeds.
All Juniperus species are included. Eachbibliography contains 1,010 citations organizedby year in descending order from 2006 to 1893.Abstracts are in English even though the articlemay be in a different language.
Several bibliography formats were created fromProcite. Each format is saved as .rtf (rich textformat) files and then converted to .pdf (portabledocument format) files for the internet. Thebibliographies can be searched through .pdfsoftware or word processing software. Threeformats are available: Subject by date.rft; Byworkform.rtf; Subject by keywords.rft. Theworkform format is the only bibliography thatlists the author’s location at the time the articlewas written.
Subject by Keywords.rft
Keywords are organized by species’ scientificname. Next to the name in parentheses are thenumber of articles listed. Under each speciesarticles are sorted in alphabetical order by theauthors’ last name. If the author has more thanone citation, the citations are organized by theoldest date to the most recent date. Scientificnames are in italics. The species’ scientific nameis always the first word under the keywords
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section. Each citation is arranged by author,article title, journal title, date, volume, issue, pagenumber, ISSN number (if available), keywords,and abstract.
By Workform.rtf
This bibliography is alphabetically arranged byauthor’s last name with a record number. Eachcitation is arranged in outline form with recordnumber, author name, article title, journal title,date, volume, issue, pages, address, ISSN, Notes,abstract, call number, keywords.
Subject by Date.rft
This bibliography organizes the articles by year indescending order. The number of articles areincluded in parentheses next to each date. Theauthors are alphabetized by last name within eachyear. The citations are organized by author name,article title, journal title, date, volume, issue,pages, ISSN, keywords, and abstract.
Conclusion
Now that the bibliographies are complete andhave been edited one time they need to be placedon as many websites as possible so that as manypeople as possible can use them. The most recentarticles from 2006 and 2007 will be added to thebibliography as an update in the near future.
Beti Piotto and Roberto CrostiAPAT Agenzia per la protezione dell’ ambiente eper i servizi tecniciVia Curtatone 3, 00185Rome, ItalyE-mail: [email protected]
Jill BarbourUSDA Forest Service National Seed Laboratory5675 Riggins Mill Road Dry Branch, GA, USA 31020
Sara CampeggianiMuseo di Storia Naturale di TrentoItaly
Marianna Mormile
Massimo Nepi and Ettore Pacini University of SienaSiena, Italy
EDITOR’S NOTE: You may access this
bibliography by going to the following web site:http://www.nsl.fs.fed.us/nsl_fsstc.html
UPCOMING MEETINGS
CTIA Tree Seed Working Group Tour and WorkshopAugust 24/25, 2008 Berthier and Quebec CityContact: Fabienne Colas
Canadian Tree Improvement Associationjoint with IUFRO Work. Grps. 2.04.01 & 2.04.10“Adaptation, Breeding and Conservation in the Eraof Forest Tree Genomics and Environmental Change”Aug 25–28, 2008 Quebec City, QCContact: Jean Beaulieu
IUFRO Tree Seed Symposium“Tree Seeds 2008 – Trees, Seeds and a ChangingClimate”Sep 22–25, 2008 Wakehurst Place, UKContact: Matt Daws [email protected]
ISTA Tropical Tree and Shrub SeedWorkshopPurity, Moisture Content, Germination, Storage,TetrazoliumApril 7–10, 2009 Curitiba, BrazilContact: Antonio Medeiros
RECENT PUBLICATIONS
Bower, A.D.; Aitken, S.N. 2008. Ecologicalgenetics and seed transfer guidelines for Pinusalbicau lis (P inaceae). A m. J . Bot.95(1):66–76.
El-Kassaby, Y.A.; Moss, I.; Kolotelo, D.; Stoehr,M. 2008. Seed germination: Mathematicalrepresentation and parameters extraction. For.Sci. 54(2):220–227.
Ellis, R.H.; Hong, T.D. 2007. Seed longevity -moisture content relationships in hermetic andop en s to rage . S eed S c i . Technol.35(2):423–431.
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Gomez-Campo, C. 2006. Erosion of geneticresources within seed genebanks: the role ofs e e d c o n ta in e r s . S e e d S c i . R e s .16(4):291–294.
McKinney, S.T.; Tomback, D.F. 2007. Theinfluence of white pine blister rust on seeddispersal in whitebark pine. Can. J. For. Res.37:1044–1057.
Owens, J.N.; Kittirat, T.; Mahalovich, M.F. 2008.Whitebark pine (Pinus albicaulis Engelm.)seed production in natural stands. For. Ecol.Manage. 255(3-4):803–809.
Potter, K.M.; Dvorak, W.S.; Crane, B.S.; Hipkins,V.D.; Jetton, R.M.; Whittier, W.A.; Rhea, R.2008. Allozyme variation and recentevolutionary history of eastern hemlock(Tsuga canadensis) in the southeastern UnitedStates. New For. 35(2):131–145.
Simpson, D.; Daigle, B.; Hayes, D. 2007. Impactof storage on viability of white spruce seed.Tree Plant. Notes 52(2):4–8.
Walters, C. 2007. Materials used for seed storagecontainers: Response to Gomez-Campo [SeedScience Research 16, 291-294 (2006)]. SeedSci. Res. 17(4): 233–242.
Williams, C.G. 2008. Selfed embryo death inPinus taeda: a phenotypic profile. NewPhytol. 178(1):210–222.
