农牧交错带草地植被土壤氮磷比季节动态及相关分析

Seasonal Dynamic and Correlation Analysis of Nitrogen/Phosphorus Ratio of Plant and Soil in Grassland of the Agro-pastoral Ecotone

近年来,典型草原面临严重的退化和沙化,草地生产力低下。了解典型草原植被土壤养分季节动态,尤其是植被土壤N:P的季节变化,有助于指示植被缺素状态。因此,以北方农牧交错带典型草原为研究对象,探讨植物-土壤N:P比季节变化,并分析植物土壤N:P比之间的关系,调查草地群落地上生物量的月动态变化,为合理利用与科学管理草原提供理论依据。结果表明,随着生长季温度的升高和降雨量的增加,草地植物群落地上生物量也不断增加,在8月份达到峰值后开始下降。植物N、P质量分数随生长季的推进而显著降低(P<0.01),且与月份呈极显著负相关(P<0.01),而N:P与月份呈极显著正相关(P<0.01)。土壤N、P质量分数和N:P的变化情况与植物相似,表现为土壤总N、P质量分数随生长季的推进而显著降低(P<0.01),且与月份呈极显著负相关(P<0.01),而总N:P与月份呈极显著正相关(P=0.0008)。就土壤有效N、P质量分数和N:P的动态变化来看,土壤有效N质量分数随生长季的推进显著下降(P<0.01),而有效P也具有下降趋势,但差异不显著(P>0.05);但有效N、P质量分数及其N:P均与月份呈极显著负相关(P<0.01)。植物N:P与土壤总N:P呈显著正相关关系(r^2=0.42,P=0.026),而与土壤有效N:P呈极显著负相关关系(r^2=0.62,P<0.01),且与有效N:P的相关性更高。综上所述,土壤总N:P和有效N:P均可反映植物N:P的情况,土壤有效N:P能更好地反映植物的缺素状态。

In recent years,typical grassland is facing serious degradation and desertification,grassland productivity is low.Understanding the seasonal dynamics of plant and soil nutrient in typical steppe,especially the seasonal variation of N.P ratio,is helpful to indicate the status of nutrient deficiency.The objective was to examine the relationship of N.P ratio between plant and soil,and to investigate monthly dynamics of aboveground biomass of plant community in agro-pastoral ecotone in Northern China.The results showed that the aboveground biomass of plant community increased with the increasing temperature and precipitation in the growing season,which decreased after reaching the peak in August.The content of N and P decreased significantly with the advancing of growing season(P<0.01),and negatively correlated with the months(P<0.01),while the N.P ratio was positively correlated with the months(P<0.01).The changes of soil total N,P content and N.P ratio were similar to those of plant.The soil total N,P content significantly decreased with the advancing of the growing season(P<0.01),and had significantly negative correlation with the months(P<0.01),and total N∶P ratio had significantly positive correlation with the months(P=0.000 8).The content of soil available N significantly decreased with the advancing of growing season(P<0.01),and soil available P also had a downward trend,but showed no significant difference(P>0.05);but the soil available N,P and N.P ratio were significantly negatively correlated with the months(P<0.01).Plant N.P ratio was positively correlated with soil total N.P ratio(r2=0.42,P=0.026),and negatively correlated with soil available N.P ratio(r2=0.62,P<0.01),and had a higher correlation with soil available N.P ratio.In summary,the soil total N.P ratio and the soil available N.P ratio can reflect the plant N.P ratio,and the soil available N.P ratio can better reflect plant nutrient deficiency.