Analysis of C, N and P stoichiometry of secondary forest in different landforms in karst area.

【Objective】The carbon,nitrogen,and phosphorus stoichiometry,as the ecological indicators,were investigated to interpret the nutrient cycle between each ingredient in karst area,as well as to illuminate the stability of karst ecosystem. 【Method】Surface soil samples fromsummit of hill,hillside tothe foot of a karst hill were collected respectively in secondary forest of karst area. Soil organic carbon(SOC),total nitrogen(TN)and total phosphorus(TP)were tested to reveal the soil carbon,nitrogen,and phosphorus stoichiometry in different karst landforms. 【Result】The contents of soil organic carbon,total nitrogen and total phosphorus range from 28.09 to 189.98 g/kg,1.19 to 8.79 g/kg,and 0.50 to 1.62 g/kg respectively.The content of P in soil was stable,and the variation of C and N was similar.Soil C∶N ratio ranges from 3.66 to47.27,C∶P ratio ranges from 26.25 to 189.06 and N∶P ratio ranges from 1.52 to 12.80. C/N and C/P were not normal distribution,while N/P was normal distribution(P0.05). The contents of SOC and TN were the highest at the foot of the mountain and have a significant difference with that of hillside and peak of the mountain(P0.05,the same below). The content of TP at the peakwas significantly higher than that of the foot of the mountain and hillside.The C/N increases with the increase of altitude,while the trend of N/P and C/P was the opposite,that was,with the increase of the altitude,N/P and C/P was gradually smaller.And there were significant differences between different landforms. Between two of SOC,TN and TP,there was extremely significant positive correlation(P0.01,the same below).The relationship between C/N and C/P wasextremely significantpositive correlation,and between C/N and N/P was extremely significant negative correlation,whilethe relationship between C/P and N/P wasextremely significantpositive correlation. 【Conclusion】The contents of soil organic matter is higher than that of other soils in the same climate condition.The total contents of both nitrogen and phosphorus are rich,but from the stoichiometry,the available contents of them are low. And the soil carbon,nitrogen and phosphorus stoichiometryis influenced by the landforms.