Phosphorus Fractions and Arbuscular Mycorrhizal Fungi as Influenced by Forest Conversion in Central Highlands of Kenya

Abstract

<p><strong>Background:</strong> Forest conversion to other land use types lead to changes in soil physico-chemical properties and a reduction in soil fertility. Although forest conversion is extensively recognized to alter soil properties, the influence on distribution of soil phosphorus (P) fractions and abundance and diversity of soil biota is not well explored. <strong>Objective:</strong> To assess the effects of converting undisturbed natural forest to plantation forest (cypress), grazed pastures and potato fields on soil phosphorus (P) fractions and abundance and diversity of arbuscular mycorrhizal fungi (AMF) in Nyandarua County, Kenya. <strong>Methodology:</strong> Transects laid out in triplicate were established in each land use type. In potato fields and grazed pastures, transects measured 50 m with three sampling points established 15 m apart along each transect, each point measuring 1 m² divided into 25 grids with each grid being 400 cm². Transect length was increased to 150 m in forest sites due to relatively larger size of the area studied and sampling points were placed at 50 m apart, each point measuring 25 m² and divided into 1² m grids. Soil and plant samples were randomly collected from sampling points and were used to determine chemical properties, soil P fractions and AMF spore examination. Data were analyzed by analysis of variance (ANOVA). <strong>Results:</strong> Soil chemical properties were significantly (<em>p</em><0.001) higher in natural forest compared to potato fields, grazed pasture and cypress forest. On the contrary, readily labile and moderately labile P was higher in fields cultivated with potato (125.3 mg and 258.2 mg P kg<sup>-1</sup>, respectively) than in natural forest (51.1 mg and 95.3 mg P kg<sup>-1</sup>) and cypress forest (36.4 mg and 82.7 mg P kg<sup>-1</sup>, respectively). However, non-labile P was higher in natural forest (599.1 mg P kg<sup>-1</sup>) and lower in cypress forest (251.3 mg kg<sup>-1</sup>). Of the ten AMF genera identified, only <em>Glomus</em> and <em>Acaulospora</em> were significantly (<em>p</em><0.01) affected by land use change, where they were more abundant in fields cultivated with potato than the other three land use types. Land use type did not significantly influence diversity and richness in AMF. However, AMF composition varied across the land use types. <strong>Implication:</strong> Land use change may negatively affect soil chemical properties, enhance redistribution of soil P, and change AMF community composition, and this could have long-term implications on soil fertility. <strong>Conclusion:</strong> Land use change from natural ecosystems to croplands, grazed pastures and tree plantations alter soil chemical properties, AMF composition and spore abundance, and redistribute soil P fractions by increasing labile P and reducing non-labile P fractions showing that the type of land use chosen significantly influence soil physical and chemical properties and soil biodiversity.</p>