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

1.1 Introduction

Since 1950, China has implemented numerous, and sometimes conflicting, policies affecting the ownership of land for both agriculture and forests (Xu and others 1999). The total area of rubber plantation in Xishuangbanna increased significantly from 6130 ha in 1963 to 136,782 ha in 1998 (Jiang 2003). Rubber has been planted after cutting natural forests. Soil microbial and fungal activity is an important indicator of soil conditions.

In all ecosystems, soil microbes play important roles in decomposition of organic matter, nutrient cycling, and plant nutrient availability (Paul and Clark, 1989). The activity and biomass of microbes respond to soil management, organic matter, and the abiotic environment, and are influenced by plant litter and rhizosphere effects (Zaady et al., 1996; Hooper and Vitousek, 1998; Jones, 1998; Caldero´n et al., 2000; Chen and Stark, 2000).

1.2 Background of study

Xishuangbanna is a biologically diverse region that covers only 0.2% of the land area of China yet contains 25% of all plant species in the entire country (Guan 1998). Over the last decades, forest cover has decreased dramatically from 63% to 34% (Yan and Chen 1992).Changes in land use and land cover are among the most important human alterations affecting the surface of the earth (Lambin and others 2001). Land-use and land-cover changes directly impact biological diversity (Sala and others 2000).

1.3 Hypothesis

l      Natural forests exhibit highest rates of microbial and fungal activity

l      Change of landuse of natural forests reduce soil biodiversity

1.4 Objectives of study

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

2.0 Materials and methods

2.1 Materials

l      Tape measure

l      Ropes

l      100cm auger

l      Buckets

l      Relascope

l      Compass

l      PVC pipes

l      Plastic bags

2.2 Site description and selection

Xishuangbanna, located in southeast China province, bordering Laos and Myanmar, is a transition zone between the tropics and subtropics。Southern Yunnan has a typical monsoon climate. Mean annual temperature is 21.7°C at 550m and 15.1°C at 1979m above sea level. Annual r/fall is between 1193mm – 2491mm. More than 80% of the R/fall falls during the rainy season from May to October.

2.3 Soil sampling and analysis

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 codes for these enzymes. Presence of these enzymes indicate more fungal activity and higher rates of decomposition.

3.1 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 from 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.

3.2Limitations

This is a study that employs techniques in isolation of DNA, use of PCR(polumerase chain reaction and DNA sequencing. Advanced lab techniques require long periods of time and rare equipment some of which may be available in Kunming. As a result, this research may take longer than expected and results may not be totally available before the end of the course.

3.3Outputs

• This study offeres an opportunity to provide insight into the consequences of landuse changes in the Xishuangbanna area.
• The study will help guide future decision making and help in choosing what landuse systems are more beneficial to the integrity of the soils and other associated natural resources

Workplan

Activity	Time schedule	Comments
Proposal development	4days
Presentation of proposal	July 20th
Review of proposal	July 22nd
Data collection	2days
Reporting and review	August 4th
Presentation	August 6th

References

Jiang, Q. N. 2003.  Actualities of Yunnan natural rubber industry, Yunnan Tropical Sciences and Technology 25:34–38.

Paul, E.A., Clark, F.E., 1989. Soil microbiology and biochemistry. Academic, San Diego, CA (273pp).

Schimel, D.S., Coleman, D.C., Horton, K.A., 1985. Soil organic matter dynamics in paired rangeland and cropland toposequences in North

Xu, J., J. Fox, L. Xing, N. Podger, S. Leisz, and A. Xihui. 1999.Effects of swidden cultivation, population growth, and state policies on land cover in Yunnan, China. Mountain Research and Development 19:123–132.