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University of Helsinki (2015)

Atmospheric Deposition and Canopy Interactions in Afromontane Forests in the Taita Hills, Kenya

Arcaro, Anthony Matthew

Titre : Atmospheric Deposition and Canopy Interactions in Afromontane Forests in the Taita Hills, Kenya

Auteur : Arcaro, Anthony Matthew

Université de soutenance : University of Helsinki,

Grade : Master 2015

Résumé
Canopy interactions and their effects on the chemical composition of throughfall were studied in three plots within two forests of Taita Hills, Kenya over a period of one year. The two forests studied are hilltop forest fragments at the elevated peak of Vuria and northern and southern Ngangao. The stands represent lower evergreen rainforest and upper montane rain/cloud forest ecosystems, which are becoming increasingly vulnerable to degradation by human population growth in the area and the effects of climate change. The forest plots have recently been placed under government protection and the data in this study has been collected as part of the TAITAWATER project of the Academy of Finland. The objective of this thesis is to quantify and chemically analyze rainfall and throughfall in order to compare the canopy interactions occurring in the three study plots. Hemispherical photographs of the canopy were also taken to assess leaf area index. Tree mapping and species identification were also carried out. In an attempt to evaluate the influence that indigenous forests in the region have on fresh water availability and quality the amount, pH, and electrical conductivity of collected rainfall or throughfall was recorded weekly. Additionally, water samples were taken and analyzed for their chemical content (Total N, NH4-, NO3-, S, Cl, Ca, Mg, K, P, Na, Si, B) in a laboratory using ICP. In agreement with previous studies the data exhibits a few trends, which indicate that canopy interception and cloud drip result in higher throughfall amounts in cloud forests, particularly during drier parts of the year when heavy rain events are scarce. Canopy interactions can also alter the chemical composition of precipitation as it passes through the canopy towards the forest floor. The canopy interactions in Taita Hills enriched throughfall with nearly all solutes leading to significant increases in EC while maintaining lower pH. The canopy with a higher presence of bryophyte and lichen species showed a greater propensity to influence the nutrient fluxes of total nitrogen and phosphorus despite containing less biomass.

Mots clés : throughfall canopy interactions atmospheric deposition

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Page publiée le 26 avril 2018