This document discusses the role of roots and mycorrhizal fungi in forest ecosystems. It covers root characteristics like diameter, density, depth and seasonality. It also discusses mycorrhizal association types and how they vary in different plant species and stages of stand development. The document outlines how roots and mycorrhizal fungi influence tree productivity, carbon allocation, nutrient cycles and how they are impacted by various management activities like thinning, fertilization and soil disturbance. In conclusion, it emphasizes that fine roots and mycorrhizal associations play an important role in forest carbon and nutrient cycles and more research is needed on their dynamics under field conditions in plantation forests.

1. Roots and mycorrhiza in
plantation ecosystem

2. Contents
1. Introduction
2. Role of roots and mycorrhizas in forest ecosystem
1. Root characteristics
2. Mycorrhiza association characteristics
3. Tree productivity, carbon allocation, and abiotic control
4. Stand development and succession
5. Nutrient cycles, roots and mycorrhizal association
3. Roots and mycorrhiza in management
1. Fungal pathogen and insect pest
2. Heavy metal toxicity
3. Management activity
4. Conclusion

3. Introduction:
Below ground component – roots and mycorrhizas are an integral part of the ecosystem – helps
in acquiring nutrients and water – affects plant carbon allocation between the shoots and roots
in short and long term
Mycorrhizal fungi : - a specialized root like organs – present in soil – as a symbiotic association
with roots – receive carbon from host plants – helps the plant in receiving nutrients from soil.

4. Role of roots and mycorrhizas in forest
ecosystem
1. Root characteristics
2. Mycorrhiza association characteristics
3. Tree productivity, carbon allocation, and abiotic control
4. Stand development and succession
5. Nutrient cycles, roots and mycorrhizal association

5. 1. Root characteristics
a. Root diameter and function
◦ Fine roots <2 mm dia – nutrient uptake
◦ Small to medium roots >2mm dia – transport and storage of carbohydrates and nutrients
◦ Coarse and primary tap roots – anchorage for plant- resist from wind damage – take up water
from deeper sources.

6. b. Root density and nutrient uptake
• Useful indication of plant ability to access soil nutrients
• Barley (1970) – soil nutrient depletion curves that related rooting density to
the mobility of soil nutrients ( highly, poorly or non mobile)
• For highly mobile elements (nitrates & sulfate) >2cm/cm³
• For poorly mobile elements > 4cm/cm³
mycorrhizae helps in facilitating nutrient uptake in poorly mobile and non mobile
elements ( ammonium, phosphate, copper and zinc)
c. Rooting depth

7. d. Fine root seasonality
• Cold temperate zone – high root growth occur immediately before or after of high
shoot growth
• Tropical wet forest – dry period duration has strong influence on high fine root
growth
• Tropical dry forest – misture availability controls the timing of fine root growth
e. Root adaptation
• Soil chemical
• Physical environment
• Root grafting

8. 2. Mycorrhiza association characteristics
a. Types and distribution of mycorrhizal
association
i. Ecto-mycorrhiza – change morphology of
roots – increase the surface area
◦ Fagaceae
◦ Dipterocarpaceae
◦ Pinaceae
◦ Myrtaeae
◦ betulaceae
ii. Endo-mycorrhiza – do not modify the structure of
root – present inside the root cortical cells.
• Found in all non-ectomycorrhizal plants

10. b. Mycorrhizal attributes
 Fungi help in – uptake of nutrients, protect plants against pathogens
 Plant - supplies the growth and maintenance requirements of fungus
c. Variability in host plant and fungus relationship
 Obligatory mycotrophs
 Facultative mycotrophs
 Non-mycorrhizal

11. 3. Tree productivity, carbon allocation,
and abiotic control
a. Roots
◦ Cold temperate conifers – show a decrease in carbon allocation to fine roots when water and/or
nutrient availability is increased
◦ In tropics – same pattern of carbon allocation ( Gonclaves, 1994)
b. Symbiotic association
◦ Ecto-mycorrhiza – having greater biomasses and more extensive sheath and hyphal network – requires
greater carbohydrate investment by the host plant than VA mycorrhizas.

12. 4. Stand development and succession
a. Fine roots
◦ Fine root biomass – peaking at canopy closure & levelling off after this time
b. Symbiotic association
◦ VA mycorrhiza dominate during early stages – ectomycorrhizal fungi dominate in later stage (Eucalyptus
plantation)
◦ No. of mycorrhizal species is greater for the younger trees than older trees (Termorshulzen and
Schaffers, 1989 )
◦ Management activities that effect surface organic horizons or the soil may influence mycorrhizal fungal
succession.

13. 5. Nutrient cycles, roots and mycorrhizal
association
a. Nutrients and plant carbon allocation
◦ N availability increases – plant decreases carbon allocation to root biomass, to mycorrhizal fungi –
increases allocation to above ground tissues
◦ Decrease in fine root biomass due to excessive addition of one nutrient with strong effects on carbon
allocation – result in deficiency in other nutrients

14. b. Roots, mycorrhiza and nutrient availability
 Fine roots and mycorrhizas – affect soil nutrient availability through
 secretion of organic acids, soluble sugars and carbon dioxide,
 upon senescence of fine roots and mycorrhizal tissues
 P. menziesii Mycorrhizal roots comprised of 6% of living biomass – contributing 48% of the
organic matter to soil

15. Roots and mycorrhiza in management
1. Fungal pathogen and insect pest
2. Heavy metal toxicity
3. Management activity

16. 1. Fungal pathogen and insect pest
Tropical plantations may be highly susceptible to fungal pathogens and insect pests – capable of
eliminating young trees planted after harvesting - Seedlings may have been planted out with an
introduced mycorrhizal fungus
Mycorrhizal fungi have been studied to be very effective at preventing the infection of plant
roots by pathogenic fungi (Marx, 1973)
Enhanced resistance of mycorrhizal plants to disease may be largely due to indirect effects of
improving plant nutrition and health

17. 2. Heavy metal toxicity
Some Plants are able to tolerate and accumulate heavy metals with mycorrhizal associations on
their roots – either exclude metals or – accumulate them within their mental sheaths (Vogt e al,
1987; wilkins, 1991)

18. 3. Management activity
Fertilizers
◦ Excessive application of P and N fertilizer alter mycorrhizal relationships – due to high conc – results in
change in species composition
Pesticide and herbicide
◦ Excess pesticide and herbicide application causes deleterious effect on VAM fungi
Thinning
◦ Thinning reduces fine root longevity.
Soil disturbance

19. Conclusion
Fine roots and mycorrhiza association constitute an interface between plants and soils and thus
play a crucial role in forest carbon, nutrient and water cycles. Their continuous growth and
dieback, often termed turnover of fine roots, may constitute a major carbon input to soils and
significantly contribute to belowground carbon cycle.
As most of plantation species are exotic – focus on testing exotic symbiotic fungi is obvious.
Most studies have concentrated on determining the effect of single symbiont on seedling
establishment in pot house/ nursery condition – study need for effect in field condition.

20. Thank you