Marking springtails (Folsomia candida) with rubidium

Marking springtails is a basic tool to evaluate their fundamental ecological phenomena. Rb marking is based on the fact that enriched rubidium in an organism can be tracked trough the experiment. Our goal was to improve the rubidium-marking technique in Folsomia candida (Willem) for both microcosm and field experiments. We investigated four methodological problems of this technique, in particular, we determined the required Rb concentration in the diet to reach marking level, measured the period when labeling could be detected under two different feeding conditions, and we estimated the effects of Rb on springtails' growth. Because marked and unmarked animals are always mixed in the course of recapture we also measured the levels of contamination between labeled springtails and those in the control groups. For introducing rubidium, we fed animals with Rb-treated Baker's yeast. Rubidium-chloride labeling persisted in springtails for 27 days during which the Rb-levels in marked animals remained distinguishable from those in unmarked ones. Rb-elimination rate depended highly on the feeding conditions, with Rb-elimination being faster when food was in excess. The fitted exponential model to Rb-elimination suggested that Rb-labeling may be used for 46 and 103 days for experiments with and without food respectively. We found no effect on Collembola growth at low Rb-levels (1.2 μg Rb/g dry yeast) but at higher concentration growth was reduced. We found that contamination occurred when springtails were stored together in glycerin, however the unmarked sample with the highest Rb content was still just 4.8% of the lowest marked sample. These results provide a basis for mark-release-recapture and other studies using Rb marking on springtails.     

油用向日葵需钾量的试验

利用~(86)Rb作示踪剂进行盆栽,结合大田的小区试验,对向日葵合理施钾量的研究表明;在N、P肥为基础正常施量情况下,以每亩7.5—15公斤施钾量最佳,既能促进前期的生长发育,又能增加百粒重,提高产量。经方差分析达1％极显著水平。     

Quantifying resource use complementarity in grassland species: A comparison of different nutrient tracers

Stable isotopes (e.g. ¹⁵N) and rare elements (e.g. Li⁺, Rb⁺, Sr²⁺) have been applied to trace nutrient uptake in plants. Tracer methods are increasingly used to quantify soil resource niche partitioning in multi-species communities. Niche partitioning allows for complementarity in nutrient uptake. Spatial complementarity is most frequently measured on separate plots, which bears a risk of between plot variations. This could be avoided with a method that allows for quantification of nutrient partitioning within the same plot. However, there is uncertainty whether uptake is sufficiently similar among different tracers to allow for direct comparison. Therefore we tested uptake similarity between Li⁺ and Rb⁺ to determine if they can serve as analogues to quantify nutrient uptake from different soil depths. We found a strong overall correlation between Li⁺ and Rb⁺ accumulation, irrespective of the duration of tracer exposition and plant species identity. However, the slope of the regression between both elements was different in roots and shoots and between different functional groups, pointing to the need of correction factors. Comparisons with other tracers showed that Li⁺ and Rb⁺ accumulation is clearly more similar to each other than to Sr²⁺ and ¹⁵N accumulation. We therefore conclude: Li⁺ and Rb⁺ have a strong potential to be used as tracers for quantifying spatial complementarity within one given plot under field conditions.     

Rubidium ‐ availability and plant uptake in natural soils

Abstract

High soil acidity (low metal ion saturation) favours the absorption of Rb from natural soils by vascular plants and fungi, whereas the absorption of K is little or not influenced. The difference in Rb uptake may be as great as one order of magnitude between soils of high and low acidity. Results of several studies are presented and discussed.