呼伦贝尔草地植物群落与土壤化学计量学特征沿经度梯度变化

植物化学计量学特征在大尺度上主要受纬度和经度两个因素影响。纬度梯度上温度因子变化对植物化学计量特征的影响已有大量研究,但是关于经度梯度上降雨因子变化对植物化学计量特征影响的研究却较少。选取呼伦贝尔草原,研究经度梯度上植物化学计量特征和土壤养分指标的变化规律,从经度梯度和养分供给两方面分析植物群落化学计量特征的变化规律,研究结果如下:1)植物群落叶片C含量变化范围为440.76—452.72 mg/g,N含量变化范围为17.79—30.88 mg/g,P含量变化范围为1.31—1.71 mg/g;群落叶片C含量、C/N随经度升高显著增加;群落叶片N含量随经度升高显著下降;植物群落P含量也呈下降趋势,但是关系不显著;植物群落C、N和P元素总量随着经度升高而显著增加。2)0—10 cm土壤全碳、全氮、全磷、有机碳受降雨量变化和植物群落元素总量影响,随着经度梯度升高而增加;但土壤铵态氮、硝态氮在经度梯度上没有表现出规律性的变化趋势。3)土壤全碳、有机碳、全氮、全磷和速效磷与植物群落叶片C、N和P含量没有显著相关关系,但与植物群落C、N和P元素总量呈显著正相关关系。该区土壤有效磷含量(8.13 mg/kg)高于全球平均值(7.65 mg/kg),但植物群落叶片磷含量平均值(1.5 mg/g)低于全球平均值(1.77 mg/g)。通过研究结果推测:植物通过对气候条件的长期适应,群落水平C、N和P含量沿经度梯度形成一定的分布格局;降雨量影响植物群落元素积累的总量,从而与土壤养分含量呈显著正相关关系;植物叶片P含量低的原因并非是由于土壤中磷的供给不足所致,而是植物对环境长期适应形成的策略。

Longitude gradient changes on plant community and soil stoichiometry characteristics of grassland in Hulunbeir

In large scale, plant stoichiometry is mainly affected by latitude and longitude. Many works has have been done to study the effects of temperature on plant stoichiometry along the latitude gradient, while researches on the precipitation along the longitude gradient are rare. In this research, we studied the stoichiometry characteristics of grassland communities along the longitude gradient in Hulunbeir. The results showed as follow: 1)the range of leaf carbon was 440.76-452.72 mg/g, leaf nitrogen was 17.79-30.88 mg/g,and leaf phosphorous was 1.31-1.71 mg/g. Both the leaf carbon and C/N ratio significantly increased with the increasing longitude. Leaf nitrogen significantly decreased with the increasing longitude, and leaf phosphorous showed an increasing tendency, however, the relationship between leaf phosphorous and longitude was not significant. The amount of carbon, nitrogen and phosphorous of grassland communities significantly increased with the increasing longitude. 2)For the 0-10cm soil depth, total carbon, total nitrogen, total phosphorus and organic carbon were significantly affected by precipitation and increased with longitude; however, soil ammonium nitrogen (NH₄⁺-N) and nitrate nitrogen (NH₃^--N) were less affected by precipitation and didn't change significantly with longitude. 3)Soil total carbon, organic carbon, total nitrogen, total phosphorus and available phosphorus did not have significant effects on plant leave carbon, nitrogen and phosphorus, but had a significant effects on the amount of carbon, nitrogen and phosphorous of grassland communities. In this studied region, soil available phosphorus was 8.13 mg/ kg, which was higher than the Global Average Value (7.65 mg/kg), but the average leaf phosphorous was 1.5 mg/g and lower than the Global Average Value (1.77 mg/kg). Our research suggested that variation in leaf carbon, leaf nitrogen and leaf phosphorus concentration and its strong correlation with precipitation reveal that, to some extent, stoichiometry characteristics at the community level are adaptive to local precipitation condition. The amount of carbon, nitrogen and phosphorus of grassland communities have a high relationship with the local precipitation, and have a significant correlation with soil total carbon, total nitrogen, total phosphorus. The shortage in soil available phosphorus is not the major factor for the low plant leaf phosphorus concentration in our studied region, and the low plant leaf phosphorus is a result of adaptation.