Arbuscular Mycorrhizal Spore Density, Composition and Richness across Four Major Land-use Types in Upper Hantana in Sri Lanka

Abstract

Arbuscular mycorrhizal (AM) fungi are widespread in different ecosystems and areassociated with more than 80% of all terrestrial species. AM play an influencing role in plantdiversity, productivity, community structure and ecosystem processes. Understanding howAM respond to vegetation changes may help understand and interpret the recovery patterns ofvegetation. The present study was designed to assess the status of AM spore density, speciescomposition and richness in four major landuse types; Paraserianthus stand (PST) dry patanagrassland (DPG) restored pine (RPI) and natural forest patch (NFP) in the Upper Hantanaarea.

From each site 10 soil samples (each is a composite of 3 samples) were taken from 0-20 cmdepth. AM spores were extracted using wet sieving and decanting method and identified totheir generic level using keys. A total of 8,234 spores were counted in NFP while 3,721,1,922 and 1,571 spores were recovered from RPI, DPG and PST respectively. Highestnumber of spore morphotypes (20) was recorded in NFP, while 18, 16 and 14 were identifiedfrom RPI, PST and DPG respectively. Out of the total spore morphotypes, 14, 10, 10 and 6were identified to their generic levels in NEP, RPI, PST and DPG landuse types respectively.The four landuse types showed contrasting patterns of different-sized spore distribution. NFPhad significantly higher densities of larger- (> 125 μm) and medium-sized spores (> 63 μm)compared to the other 3 land use types. Glomus was the most abundant genus in all fourlanduse types. In PST, 5 morphotypes were belonged to the genus Glomus, 3 Acaulosporaand 2 Gigaspora. In DPG, 3 Acaulospora spp., 2 Glomus spp. and 1 Scutellospora spp. InRPI, 7 Glomus spp., 3 Gigaspora spp. and in NFP 10 Glomus spp. 2 Gigaspora spp. and 2Scutellospora spp. were identified. Out of the four landuse types, NFP showed the highestAMF richness with a Shannon-Weiner Index of 2.436 which followed by RPI, DPG and PST(2.280, 2.173 and 2.139 respectively).

The results suggest that the study sites demonstrated distinct AM communities indicating thatthe vegetation cover and landuse history may play a role in determining the communitystructure of AM. The higher AM abundance and richness observed in recently restored Pinusstand (RPI) compared to PST and DPG suggest that the AM population can be rapidlyrestored through increasing plant diversity with native species, which may eventually helprestore these ecosystems.