Aims

Deposition of urine and dung is a key mechanism by which herbivores influence the nutrient cycling of terrestrial ecosystems. Yet, little is known about the roles of urine, dung and their mixtures in regulating the plant and soil carbon:nitrogen:phosphorus (C:N:P) stoichiometry and their interactions.

Methods

We explored how different excrement types (urine, dung and their mixtures) and supply levels [urine: 0.5, 1.0 and 1.5 L m⁻²; dung: 4.7, 9.4 and 14.2 g m⁻²; mixtures (urine+dung): 0.5 + 4.7, 1.0 + 9.4 and 1.5 + 14.2] altered the plant and soil C:N:P stoichiometry in a semi-arid grassland on the Loess Plateau.

Results

We found that the aboveground biomass of the whole community was highest at the highest mixtures application rate, while the highest aboveground biomass of the three dominant species was detected at applications of 0.5 L m⁻² urine for Stipa bungeana, 9.4 g m⁻² dung for Lespedeza davurica and 1.0 L m⁻² urine +9.4 g m⁻² dung for Artemisia capillaris. Urine and dung alone increased plant N concentration, which peaked at 1.0 L m⁻² urine. Plant P concentration at 1.5 + 14.2 mixtures was significantly higher than that at control without significant difference between excrement types. Compared to the control, excrement deposition did not significantly change plant C concentration and C:N, C:P and N:P ratios. However, plant C:P and N:P ratios under the mixtures were significantly lower than those under urine or dung. Excrement applications led to more soil (total, microbial and organic) C, N and P accumulations. Compared to urine and dung, the mixtures induced higher total P concentration but lower total N concentration in soil.

Conclusions

Our study demonstrated that the impacts of sheep urine and dung on plant and soil C and nutrient concentrations and stoichiometry differed from that of mixtures. The plant N:P ratio indicated balanced N:P supply for urine and dung applications but N limitation for mixtures application. This study provides experimental evidence that the excrement of herbivores plays an important role in altering ecological stoichiometry in plants and soil.

中文翻译：

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黄土高原典型草原绵羊粪便类型和供应水平对植物和土壤C：N：P化学计量的不同影响

目的

尿液和粪便的沉积是草食动物影响陆地生态系统养分循环的关键机制。然而，关于尿，粪便及其混合物在调节植物和土壤碳：氮：磷（C：N：P）化学计量中的作用及其相互作用所知甚少。

方法

我们探索了不同的排泄类型（尿，粪便及其混合物）和供应水平[尿：0.5、1.0和1.5 L m ^-2；粪便：4.7、9.4和14.2g m ^-2；混合物（尿+粪）：0.5 + 4.7、1.0 + 9.4和1.5 + 14.2]改变了黄土高原半干旱草原上植物和土壤的C：N：P化学计量关系。

结果

我们发现，在最高混合施用量下，整个群落的地上生物量最高，而在施密加针茅（Stipa bungeana）的尿量为0.5 L m ^-2，对粪便为9.4 g m ^-2时，三种优势种的地上生物量最高。淡水艾草（Lespedeza davurica）和1.0 L m ^-2尿液+9.4 g m ^-2粪便用于艾蒿。仅尿液和粪便就增加了植物氮的浓度，最高浓度为1.0 L m ^-2尿。1.5 + 14.2混合液中的植物P浓度显着高于对照，排泄物类型之间无显着差异。与对照相比，排泄物沉积没有显着改变植物C的浓度以及C：N，C：P和N：P的比例。但是，混合物下植物的C：P和N：P比率显着低于尿液或粪便下的植物。粪便的施用导致土壤（全部，微生物和有机）的碳，氮和磷积累量增加。与尿液和粪便相比，混合物在土壤中诱导了较高的总磷浓度，但降低了总氮浓度。

结论

我们的研究表明，绵羊尿和粪便对植物和土壤碳，养分浓度和化学计量的影响与混合物的影响不同。植物的N：P比率表明尿液和粪便的N：P供给平衡，但混合物的N限制。这项研究提供了实验证据，表明草食动物的排泄物在改变植物和土壤的生态化学计量方面起着重要作用。