宁夏典型草原不同退耕年限草地植物-土壤生态化学计量特征

为了研究宁夏典型草原不同退耕年限草地优势植物及土壤C、N、P化学计量特征,本研究以宁夏南部典型草原区退耕草地为对象,分别对退耕0、1、3、5、6、8、11、15、20年草地优势植物及土壤碳、氮、磷等生态化学计量特征进行研究。结果表明,各植物全氮含量均表现为地上部分大于地下部分,且猪毛蒿整体全氮含量较其他植物高。全磷含量除赖草外也表现为地上部分大于地下部分。退耕1年狗尾草和退耕3年赖草有机碳含量表现为地下部分大于地上部分,其余各退耕年限地上部分大于地下部分。优势植物C∶N、C∶P、N∶P整体表现为退耕20年长芒草最大。赖草和猪毛蒿最小。退耕6年以上20年以内土壤有机碳含量由表层向深层逐层递减;全氮含量退耕0~6年呈波动式变化,退耕8年后全氮含量由表层向深层逐层递减;全磷含量变化趋势与全氮相同。研究区土壤C∶N变化范围为7.08~19.62,C∶P变化范围为6.60~35.25,N∶P变化范围为0.82~2.17。各层土壤C∶N平均值变化范围为11.18~15.03,C∶P平均值变化范围为14.09~24.55,N∶P平均值变化范围为1.06~1.98;除C∶N接近我国土壤C∶N均值外,研究区土壤C∶P和N∶P均低于我国土壤C∶P和N∶P均值。并且相应地表优势植物C∶N、C∶P、N∶P明显高于表层土壤。本研究中土壤C∶N与土壤有机碳之间相关性不显著,与全N呈负相关,意味着C∶N主要受N控制,而C∶P与有机碳呈显著正相关,与全P相关性不显著。土壤N∶P与土壤全N含量呈显著正相关,与土壤全P含量相关性不显著,说明主要受N控制,而土壤全N含量随退耕年限的增加呈波动式上升趋势。植物与土壤碳、氮、磷相关性显示:植物全N与土壤N之间相关性不显著(P0.05),植物全P与土壤全N、全P呈极显著的相关关系(P0.01),与土壤有机碳和N∶P呈显著的相关关系(P0.05)。

Effect of grassland restoration duration on plant-soil ecological stoichiometry characteristics in a typical steppe

To determine the influence of restoration period on the stoichiometry of dominant plant species and soil C,N,P of typical steppe in Ningxia,China,the stoichiometric characteristics of dominant plant species and soil C,N,P in grassland abandoned for periods of 0,1,3,5,6,8,11,15 and 20 years.The total nitrogen content of individual plants showed that the aboveground portion is greater than the belowground portion;the total nitrogen content of Artemisia scoparia was higher than other species.Similarly the total P content of plants was dominated by the above ground portion with the exception of Leym us secalinus plants.The organic carbon in grassland abandoned for 1 year Setaria viridis and 3 years L.secalinus was greater in the underground portion;for remaining abandonment periods the aboveground portion was greater than underground portion.The highest C ∶ N,C ∶ P,N ∶ P ratio's in dominant plants in 20 year grassland occurred in S.bungeana and the lowest in L.secalinus and A.scoparia.Abandonment periods between 6 and 20 years resulted in soil organic carbon content layer decreasing from the surface with increasing depth while abandonment periods between 0-6 years resulted in fluctuating changes in soil N.The response of total P to abandonment period was similar to that of total N.The soil C ∶ N ration varied from 7.08-19.62,C ∶ P ranged from 6.60 to 35.25,N ∶ P varied from 0.82 to 2.17;the mean soil C ∶ N ration ranged from 11.18 to 15.03 in different soil layers,C ∶ P from 14.09 to 24.55 and N ∶ P from 1.06 to 1.98;The soil C ∶ P and N ∶ P ratio's were generally lower than those typically found in other regions of China while the C ∶ N ration was similar to typical values in China.There was no correlation between soil C ∶ N and soil organic carbon but there was a negative correlation with total N,meaning that C ∶ N was mainly controlled by N;the C ∶ P ratio was significantly positively correlated with organic carbon but not with total P.There was a significant positive correlation between soil N ∶ P and total soil N,indicating this ration is primarily controlled by N.Total soil N showed a fluctuating upward trend with increasing abandonment period.There was a strong correlation between total plant P and total soil P (P＜0.01);soil organic C was also correlated with N ∶ P (P＜0.05).