太白山不同海拔土壤碳、氮、磷含量及生态化学计量特征

为探究太白山土壤碳(C)、氮(N)、磷(P)含量垂直分布特征,阐明土壤C、N、P生态化学计量学特征对海拔梯度的响应规律,在秦岭太白山1 700~3 500 m区域以100 m海拔间隔进行研究。结果表明:(1)不同海拔高度下土壤有机碳、全氮、全磷变化范围分别是23.56~83.59g kg-1、2.00~5.77 g kg-1、0.32~0.47 g kg-1。土壤有机碳与全氮含量随海拔梯度升高先增后降,土壤全磷含量空间变异较小;(2)土壤C∶N、C∶P、N∶P范围分别为7.17~18.41、60.61~190.4、5.81~12.26。随海拔增加,土壤C∶N在阔叶林带呈降低趋势,针叶林带时转变为增加趋势。土壤C∶P随海拔梯度的变化趋势与土壤C∶N类似,N∶P随海拔梯度增加先升后降,至3 200 m有所升高;(3)两个阔叶林带(辽东栎林带和桦木林带)与高山草甸的土壤C、N含量及生态化学计量比高。冷杉林带C、N含量及其生态化学计量比最小;(4)温度、含水量、海拔和植被对土壤C、N、P化学计量特征具有重要影响,通过冗余分析揭示每个因素分别可解释系统变异信息的25.0%、24.3%、11.1%和6.9%,合计为67.3%。可见这些环境因素直接决定了土壤养分及生态化学计量特征。结果可为探明森林土壤养分供应状况和限制因素及太白山生态系统的保护、森林土壤质量评价等提供基础。

Carbon, Nitrogen and Phosphorus Contents in Soils on Taibai Mountain and Their Ecological Stoichiometry relative to Elevation

Objective]This study is to explore how soil carbon,nitrogen and phosphorus were distributed vertically along the slope of the Taibai Mountain and elaborate eco-stoichiometric characteristics of these soil nutrient elements relative to elevation from 1 700 m to 3 500 m.[Method]Soil samples were collected along the slope at an interval of 100 m in elevation and soil physicochemical properties were mensurated for analysis. [Result]Results show as follows.(1)Soil organic carbon(SOC),total nitrogen (TN)and total phosphorus(TP)in the soil varied in the range of 23.56~83.59 g kg -1,2.00~5.77 g kg-1 and 0.32~0.47 g kg-1,respectively,and averaged 40.58 g kg-1,3.11 g kg-1 and 0.39 g kg-1, respectively. Soil organic carbon and TN displayed a trend of rising-first-and-declining-later with the rising elevation and a peak appeared at 3 000 m. The content of SOC was obviously higher in the middle section of the slope,2 200~2 300 m in elevation than in the upper and lower sections of the slope and TN varied similarly in vertical distribution. So soil carbon and nitrogen content were quite consistent in spatial variation. However,TP varied much less spatially and along the altitude gradient. Along the slope of the Taibai Mountain,stand different types of forests in belt. In these different forest belts,regardless of type,the distributions of soil carbon,nitrogen,phosphorus were somewhat coupled. Soil C∶N,C∶P and N∶P varied in the range of 7.17~18.41,60.61~190.4 and 5.81~12.26,respectively,and averaged 12.99,102.2 and 7.90. With rising elevation,soil C∶N decreased in the broad-leaved forest belt and increased in the coniferous forest;soil C∶N was quite close to the average(12.4)of the global forest soil(0~10 cm);soil C∶P varied in a trend similar to what soil C∶N did,and peaked in the section of the slope,2 200~2 300 m in elevation,getting higher than the average(81.9)of the global forest soil(0~10 cm);and soil N∶P was similar to soil C∶N in variation.(2)SOC,TN and TP varied in the range of 23.84~49.54 g kg-1,2.42~3.62 g kg-1 and 0.36~0.42 g kg-1,and averaged 39.82 g kg-1,2.97 g kg-1 and 0.39 g kg-1, respectively,in the studied slope under whatever type of forest. SOC was obviously lower in the fir forest belt than in the broad-leaved forest(Quercus acutidentata forest,liaodong oak forest,birch forest)belt;soil TN in the coniferous forest belt was significantly lower than that in the Quercus liaotungensis forest and alpine meadow belts,and similar to those in the others;and soil TP differed slightly between forest belts. Soil C∶N,C∶P and N∶P varied in the range of 9.80~15.49,67.01~119.44 and 6.32~9.21,and averaged 13.36,100.81 and 7.54,respectively. The two broad-leaved forests(Quercus liaotungensis forest belt and birch forest belt)and the alpine meadow belt were the highest in content of soil carbon and nitrogen and their ecological stoichiometric ratio,while the fir forest belt was the lowest.(3)Temperature,water content,elevation and vegetation may quite well explain the variation of the ecological stoichiometry of soil carbon,nitrogen and phosphorus. Redundancy analysis shows that the points of Ⅰ and Ⅰ on the sequencing axis may explain 57.94% and 9.21% of the variation of the contents of soil nutrients and their stoichiometric characteristics,and the four factors,temperature,water content,elevation and vegetation,may explain 25.7%,22.5%,20.9% and 18.7%,respectively,of the system variation. Obviously,elevation is the major factor that directly determines vegetation type and environmental conditions,which in turn affect distribution and eco-stoichiometry of soil nutrients. [Conclusion]All the findings in this study may serve as scientific basis for determining soil nutrient supply and its limiting factors in these forest soils and evaluating quality of these soils. However,more effects should be made to further discuss the issue of soil nutrients and their eco-stoichiometric characteristics,and to expose stoichiometric characteristics,mutual relationships and spatial variation of the forest system of vegetation-litter-soil.