高寒草原矮火绒草和紫花针茅微斑块对Rb^(+)的吸收距离

Potential absorption distance for Rb^(+)by Stipa purpurea and Leontopodium nanum in an alpine steppe

植物微斑块是草原植被基本的空间分布形式,空白裸地上的土壤养分资源在多远距离上能够被植物吸收是一个重要问题。利用稀有元素铷(Rb)示踪方法,通过分析Rb^(+)的吸收量和吸收距离,探讨青藏高原高寒草原群落群落优势种紫花针茅(Stipa purpurea)和伴生种(同时也是退化草地常见种)矮火绒草(Leontopodium nanum)对土壤养分和水分资源的吸收范围。结果表明:紫花针茅斑块对Rb^(+)的平均最大吸收距离(5.6 cm)约等于平均斑块间距(5.7 cm),而矮火绒草斑块平均最大吸收距离(34.2 cm)远大于紫花针茅和平均斑块间距;2个物种对Rb^(+)的吸收量都与斑块大小(生物量)呈极显著正相关(P<0.001);无论吸收量还是吸收距离,矮火绒草均大于紫花针茅。这说明裸地土壤中的养分资源可以被植物微斑块吸收利用,而且大斑块对资源占有的能力也越强。

Micro-patches are basic spatial units of steppe vegetation,which cause redistribution of soil nutrients during the formation and break of the patches.To what extent the resources in inter-patch bare ground could be utilized by plants is of an important issue to be answered.In this study,we injected rare elemental tracer Rb^(+)into the soil at different distances from the vegetation patch.By measuring the amount and distance of Rb^(+)being absorbed by vegetation micro-patches,we found that:1)the average potential absorption distance of Rb^(+)by the dominant species Stipa purpurea is 5.6 cm,which almost equals the average interval of 5.7 cm among patches;2)the average potential absorption distance by companion species Leontopodium nanum is 34.2 cm,which is much larger than that of S.purpurea and average interval among patches;3)the total amount of Rb^(+)absorption is significantly positively correlated(P<0.001)with the biomass/size of the micro-patches in both species.These results indicate that the nutrient resources in the bare soil are accessible to adjacent plant patches and that large patches have higher utilization potential and broader foraging area than small ones.