CHEN+Luhong1,+YU+Yanwen++SU+Kaiwen++GONG+Hede

Abstract：This paper took the soil of dominant thickets in central Yunnan province as the research object， analyzed the SOC distribution characteristics of dominant thickets in Central Yunnan province. the results show that 1）the holistic spatial distribution of philanthropy emblematic shrub's SOC is lessen from southeast to northwest， the soil organic content of South candle， Myrica nanashrub integrally decrease from the centre to periphery. 2） the soil organic content of philanthropy emblematic shrub shows the feature of decrease from surface to downward； the vertical distribution of South candle， Myrica nanashrub's organic carbon content remains relatively stable.

Key Words：South candle； Myrica nana； Philanthropy emblematic； dominant thickets； soil； organic carbon

Thicket is the main vegetation of arid ecosystems （Wang Bing， etc.， 2015）， based on the absorption and deposition of soil resources （stark J M， 1994， unusual non-stick W G， 1997）， effected on the distribution of SOC and the carbon cycle （Binkley D&Giardina C， 1998， Kieft T L， 1998）. This study selected the zonal vegetation in Yunnan central region of Yunnan province as research object， included philanthropy emblematic community、South candle community and Myrica nana community.researched the characteristic of the SOC， aimed to expand Yunnan terrestrial ecosystem carbon library for basic data， provided theoretical basis for regional thickets soil degradation and recovery.

1.Materials and Methods

1.1Basic Situation of Study Area

The study area is located in the central Yunnan province， valley thickets use philanthropy emblematic for constructive species， soil based on purple soil， red soil and latosolic red soil （Gong Hede， etc.， 2012）. Mountain thickets use south candle and Myrica nanafor constructive species， soil based on red soil， yellow soil， brown soil and purple soil （Yang Yueyuan etc.， 2013）.

1.2 The Research Methods

1.2.1 Sampling and Sample Testing

Chose six philanthropy emblematic thickets research samples and 25 south candle， Myrica nana thickets research samples， each sample established four 5 m x 5 m samples， every profile is divided into 6 level to sampling，involved the 0 to 10， 10 ～ 20， 20 ～ 30， 30 ～ 50， 50 ～ 70， and 70 ～ 100 cm， Soil samples are measured by the relevant methods of《analysis of soil agro-chemistry》， using heavy cadmium acid potassium outside heating method to determine SOC （BaoShidan， 2000）.

2. The Results

2.1 The Spatial Distribution of SOC

Getting the results of the spatial distribution of SOC of dominant thickets in central Yunnan provinceby Kriging interpolation of SOC. As shown in figure 1.

a.philanthropy emblematic shrub

b. South candle， Myrica nanashrub

Fig.1Spatial distribution pattern of SOCcontent

2.2 The Statistical Characteristics of SOC

The results ofregional total organic carbon are shown in table1， the 0 ～ 100 cm SOC of philanthropy emblematic thickets is 0.96 ±0.4 g/kg， the variation coefficient is 0.40% ～ 0.56%， decrease with the increase of soil depth in SOC， the SOC variation extent is big， belongs to the moderate variation. 0 ～ 100 cm SOC of South candle， Myrica nanais 0.85±0.78 g/kg， the variation coefficient is 0.90% ～ 0.92%， and SOC and degree of variation is not large， but the overall variation degree is higher for the variation coefficient are both more than 90%， belong to moderate variation. Research results show that （Table1）.

Table 1Statistical characteristics of SOC

3. The main conclusion

（1） The SOC spatial distribution layout of philanthropy emblematic thicket and South candle， Myrica nana thicket are different. This is mainly due to the ecological environment， under the condition of drought， the soil humidity is low， weak soil respiration， plant photosynthetic ability is abate， water become a limit factor， it is not conducive to accumulation of organic carbon （post et al.， 1990； FanHengwen etc.， 2002； HaoYanbin etc.， 2010）， the trend of holistic spatial distribution of philanthropy emblematic shrub's SOC is lessen from southeast to northwestis consistent withthe precipitation pattern in Yunnan（TaoYun， 2003）.

（2） The philanthropy emblematic thicket of SOC decrease with the increase of soil depth in the study， surface-aggregation is apparent， for the reasons are the roots ofphilanthropy emblematic thicket concentrated distribute in the soil， and fine roots have important status， root system has large biomass， high degree of rotting， lead to the high surface SOC accumulation. With the increase of soil layer， the concentration of organic carbon in the earth's surface can only rely on water or other media to spread， surface carbon moving to the lower layer under the effect of vertical movement of soil moisture and precipitation eluviation， lead to SOC presented the feature of decline from surface （LeiPifeng etc.， 2004）.

References

[1]Xu NZ， Liu HY， Wei F. （2011）. Research progress on soil carbon pool and its changes.Jiangsu Agricultural Sciences， 39（2）， 1～5.（in Chinese with English abstract）.

[2]Zhang XH， Zhang YD， Gu FX， Liu SR. （2011）. Dynamics of shrubs normalized differencevegetation index and its correlations with climatic factors in Southwest China. ActaEcologicaSinca， 30（11）， 2577～2583.（in Chinese with English abstract）.

[3]Wei YY， Yin HJ， Liu Q， Li YX. （2009）.Advance in research of forest carbon cycling under climate warming，Chinese Journal of Applied & Environmental Biology， 15（6），888～894.（in Chinese with English abstract）.

[4]Zhou GM， Liu EB， She GH.（2006）. Summary of estimated methods on forest soil's carbon pool.Journal of Zhejiang Forestry， 23（2）， 207～216.（in Chinese with English abstract）.

[5]Gong HD， Du LL， Yin HJ， YIN CY. （2012）. Biomass distribution characteristic in phyllaythusemblica shrub ecosystem in Yunnan province. World Sci～Tech R&D.，34， 607～610 （in Chinese with English abstract）.

Author's brief：

The first author introduction： Chen Luhong （1992 -）， female， master graduate student， majoring in natural geography. Email：943343625@qq.com

corresponding author introduction： Gong Hede （1978 -）， male， associate professor， mainly engaged in forest ecological research. Email： GongHede3@163.com