Mycorrhizal symbiosis and seedling performance of the frankincense tree (Boswellia papyrifera)

E.B. Hizikias

Research output: Thesisinternal PhD, WU

Abstract

Arid areas are characterized by a seasonal climate with a long dry period. In such stressful

environment, resource availability is driven by longterm and shorterm rainfall pulses.

Arbuscular Mycorrhizal (AM) fungi enhance access to moisture and nutrients and thereby

influence plant performance. In this dissertation I applied field observations and

greenhouse experiments to address four questions: 1) What are the major environmental

factors influencing AM incidence in the Boswellia-dominated dry deciduous woodlands?

2) How do Boswellia seedlings respond when they are exposed to AM fungi and water

pulses? 3) How do AM fungi, water deficit and soil fertility influence the growth and gas

exchange of Boswellia and Acacia seedlings? 4) Does the AM symbiosis influence

competition between Acacia and Boswellia seedlings at different water pulse levels?

The present study showed that almost all woodland plants in northern Ethiopia are

colonized by AM fungi. Root colonization levels in dry and wet seasons demonstrated that

in the sites with the harshest conditions, AM plants and fungi respond to pulsed resource

availability by temporally disconnecting carbon gain by the plant and carbon expenditure

by the fungus. Consequently, we studied below-ground processes in conferring adaptation

to highly pulsed resources in Boswellia seedlings. The strong interactive AM fungi and

water pulse showed that mycorrhizal Boswellia benefits from drought pulses during the

short rainy season. Boswellia acquires carbon and water after rain events and store

probably carbon and water in coarse roots, suggesting conservative strategy. From this

observation we carried out an experiment to test whether other trees (Acacias) than

Boswellia in this habitat also show this conservative acquisition strategy, or whether more

acquisitive strategies may also be beneficial under such climates.

My study show that acquisitive and conservative species both benefit from the AM

symbiosis, but that the acquisitive Acacias mainly benefit at higher water availability,

whereas the conservative Boswellia benefits at water or nutrient-stressed conditions. I also

investigate on how mycorrhiza and water availability affect competition between plants

with different resource acquisition strategies in these drylands. Seedlings of Boswellia are

competitively inferior to seedlings of Acacia, and neither the presence of AM fungi nor a

stronger water limitation (through pulsing) affected this outcome. 

Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Wageningen University
Supervisors/Advisors
  • Bongers, Frans, Promotor
  • Kuijper, Thomas, Promotor
  • Sterck, Frank, Co-promotor
Award date14 Sep 2011
Place of Publication[S.l.]
Print ISBNs9789085859635
Publication statusPublished - 2011

Keywords

  • boswellia
  • mycorrhizas
  • symbiosis
  • seedlings
  • vesicular arbuscular mycorrhizas
  • water availability
  • water stress
  • tropics
  • ethiopia

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