forest genetic resources training guide tree seed supply chains tree planting on farms in east...

Forest Genetic Resources Training Guide

Tree seed supply chains

Tree planting on farms in East Africa: how to ensure genetic diversity?David Boshier,Ian Dawson &Ard Lengkeek


Location of the countries and survey areas

KenyaUganda

Tanzania

Kabale

Mabira

Arusha

Meru

Nairobi

Location of nursery survey sites


Nursery sites


Why bother about genetic diversity?

• adaptation to changing environments• direct use of genetic resources• viability of populations in short term• - seed production• - inbreeding depression


Inbreeding depression in Acacia mangium in Sabah

Seed source

1st generation

2nd generation

3rd generation

Seedling height (cm)

32.5

20.7

18.1

Sim, 1984


Theory

• direct impacts

• decrease population size

• increase spatial isolation

• decrease densities

• change local environment

genetic processes

genetic drift

gene flow

mating - inbreeding

selection


Bottleneck genetic drift


Isolated trees– mating patterns?


Altered mating patterns in farm trees?

• Predictions: increased inbreeding• greater pollen dispersal• fewer sires

• Isolated farm tree Continuous forest

inbreedingdispersal

sires


How many trees to collect from?


Data collected in a survey of seed-propagated tree species in tree nurseries from five areas in East Africa

Survey area (country) All areas

Kabale (Uganda)

Mabira (Uganda)

Nairobi (Kenya)

Meru (Kenya)

Arusha (Tanzania)

Nurseries [client data*] 7 [6] 9 [7] 21 [16] 12 [8] 22 [22] 71 [59]Cases [client data] 15 [8] 26 [16] 31 [25] 17 [10] 54 [54] 143 [113]All species 11 14 16 7 16 43Indigenous species 3 6 6 1 3 15Cases indigenous species 4 10 6 2 5 27Cases five most common species

2 3 11 10 40 66

Cases of unique species occurrence

3 6 6 2 5 22

Single tree collections all species

7 4 8 7 5 31

Single tree collections indigenous species

2 1 2 0 1 6

Seed trees per nursery lot, Nm: mean (SD)

3.7 1.8 (3.6)

5.1 2.3 (6.0)

5.8 3.1 (8.9)

5.7 3.1 (6.5)

8.2 3.8 (14.1)

6.4 1.7 (10.3)

Seedlings per nursery lot, Ns: mean (SD)

871 712 (1408)

2060 1408 (3661)

787 432 (1228)

1339 1011 (2127)

1543 676 (2535)

1378 401 (2446)

Clients per nursery lot, Nc: mean (SD)

12 14 (20)

41 27 (55)

17 9 (22) 81 92 (149)

22 5 (20) 28 10 (53)


Cupressus lusitanica

Wind pollinatedHermaphrodite, self compatible100,000 seed produced per tree


Calliandra calothyrsus

Bat/moth pollinatedHermaphrodite and male flowers, Mainly outcrossing1,000 seed produced per tree


Dovyalis caffra

Bird?/insect pollinatedDioecious270-470 seed produced per tree


Sclerocarya birrea – male tree being cut as not producing fruits


Grevillea robusta

• Self incompatible with protandry• Fruit set cross-pollination (5.9-17.5%)

>open-pollination on farms (0.1%-3.3%)• Open-pollinated flower stigmas – most no

pollen or only self-pollen• Lack of cross-pollen may limit seed

production


Senna siamea

• Insect pollinated• Hermaphrodite• Self–compatible?• High seed production per

tree


Procurement pathwaysNGOs compared with CBOs


Distribution pathways


Think about and discuss

• Where are bottlenecks to genetic diversity? How to overcome these?

• In 5 main species, how does seed production per tree influence number of trees seed collected from? How species biology affects genetic diversity in seed collections?

• How can mixing seed ensure use and maintenance of existing genetic diversity? mean Ns/Nc vs mean Ns/Nm.

• Advice/training to improve situation? Figs 2-4; to NGOs and/or directly to communities? What specific advice/training?

• How does seed collection and plant production occur? • Are seeds and plants transferred and if so how? Does this provide

limitations or opportunities?


Plan objective: ensure maintenance of genetic diversity in the collection & supply of seed, & improved nursery practice

• Plan should identify: • influences on genetic diversity(bottlenecks, selection,

genetic drift) associated with current seed collection and distribution paths

• key actors (individuals, institutions), processes (what actors do), social limits in seed supply chain (policy, trade, institutional, capacity). Communication/training needs related to key actors.

• Specific actions to improve situation, addressing diversity issues in seed system (e.g. practical ways to collect & distribute seed/seedlings to ensure genetic diversity in nurseries & material planted in field)

forest genetic resources training guide tree seed supply chains tree planting on farms in east...

Documents

tree slide

genetic diversity

tree nurseries

survey of seed

seed trees

propagated tree species

ian dawson ard lengkeek

nursery lot