SOIL MICROBIAL AND FUNGAL DIVERSITY AMONG LAND USE HISTORIES IN XISHUANGBANNA TROPICAL BOTANICAL GARDENS(XTBG)- Peter Alele, Deng Wen, Liu Shengjie, Zhang Ming-gang

Hypothesis

l      Natural forests exhibit highest microbial and fungal diversity

l      Change of landuse of natural forests reduce soil biodiversity

Objectives

l      To determine the species richness and diversity of different bacteria and fungi in two landuse types in XTBG.

l      Use of metagenomics and enzymatic activity to study soil bacterial and fungal activity

Method

A survey of 2 different landuse histories: rubber plantation and pomelo plantation will be conducted. 3 plots of 40mX40m will be selected and established in each landuse type. 4 circular sub- plots will be established within each plot with their centers 10 meters from each side of the larger square plot (of 40mX40m). Each circular sub-plot will have a radius of 5m. Within each sub-plot, top soil and leaf-litter samples will be collected with each plot treated as a treatment block. DNA will then be extracted from the soil samples and techniques in genomics will be used to study microbial activity.

Fungal activity will be studied by examination of indicators of activity of enzymes peroxidase and phenol oxidase. These are enzymes that break down lignin and help decompose woody tissue. The primer will look for laccase gene that code for these enzymes. Presence of these enzymes indicates more fungal activity and higher rates of decomposition.

Discussions

Rubber plantations and pomelo plantations represent two types of land use that have distinct effects on soil characteristics and soil microbiology. A strong decline in soil carbon (C) occurs after repeated tillage (Schimel et al., 1985; Elliott, 1986; Burke et al., 1989; Woods, 1989; Conant et al., 2001),and this occurs in both landuse systems;  while grasslands tend to support increased soil C and microbial biomass with greater spatial heterogeneity within the soil profile than in cultivated soils (Woods, 1989; Kandeler and Murer, 1993; Caldero´n et al., 2000). Agricultural practices such as residue incorporation, cropping sequence, irrigation, and tillage alter soil microbial biomass (Anderson and Gray, 1990; Sparling et al., 1994; Franzluebbers et al., 1995) and soil microbial community composition (Bossio et al., 1998; Lundquist et al., 1999; Caldero´n et al., 2000). In some cases, cultivation history has long-term effects on microbial community structure in abandoned agricultural fields (Buckley and Schmidt, 2001), and gradients in soil fertility in either grasslands (Donnison et al., 2000; Grayston et al., 2001) or cultivated sites (Yao et al., 2000) have been shown to influence microbial community composition.

In this study, microbial diversity will be studied in soils and comparisons made between a rubber plantation and pomelo plantation. This will give us an insight into the impact of these two landuse systems on microbial diversity and fungal activity which are both strong indicators of soil health.

Workplan