The decomposition of organic matter in soils by fungi

  • Rachel Kabuyah

Student thesis: Phd


Macromolecular structures, such as lignin and cellulose, are important components ofsoil organic carbon, the major terrestrial global carbon pool. The degradation of thesemacromolecules, including lignin and cellulose, in plant-derived soil organic matter, isimportant to the global carbon cycle. In grasslands, saprotrophic (decomposer) fungi aremajor decomposers of such organic material.Some of these compounds, such as lignin are relatively resistant to decay by themicrobial community if compared with other compound classes such as cellulose.In this work we investigate the involvement of fungi in the decomposition of both ligninand cellulose and look to link the decomposition processes observed in the field to thoseobserved in a laboratory-controlled environment.The key findings of this work are:-Field based experiments in both tropical and temperate environments indicatedthat lignin can be degraded completely, most likely by white-rot fungi, as shownby the shifts in the [Ac/Al]S, [Ac/Al]G and [S/G] relative lignin decompositionstate proxies. The results confirm that even in a very low carbon environment,fungi are able to completely degrade lignin over time. However, lignin isdegraded much faster in tropical environments.-Culturing experiments showed that it was possible to isolate a number of fungipresent on the degraded wheat straw collected in the field., especially soft-rotfungi .When used in microcosm experiments using a range of organic substrates,the relative lignin decomposition state proxies indicated that Absidiacylindrospora and Trichoderma koningii are not able to completely degradelignin but preferentially degrade cellulose.-Cellulose degradation rates are much higher than those of lignin in degradedfield samples over time, confirming previous work.
Date of Award1 Aug 2013
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorClare Robinson (Supervisor) & Bart Van Dongen (Supervisor)


  • lignin, cellulose, fungi, guaiacyl, syringyl, decomposition, grasslands

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