Aims

Soil processes in arid ecosystems are strongly controlled by resource scarcity. Grazing intensification can induce changes in ecosystem processes through multiple pathways, adding new constraints to those of local conditions. We focus on grazing-induced changes in litter traits and soil environment that may affect litter decomposition and N dynamics in temperate grass-shrub steppes.

Methods

We performed three litterbag decomposition experiments to evaluate: i) the effect of litter traits in a common garden (ex situ), ii) the effect of soil environment using a foreign common litter substrate (in situ), and iii) the interactive effects of litter traits and soil environment (grazed vs. exclosure communities, reciprocal transplants in situ). Field experiments were replicated in three blocks with paired plots under a long-term exclosure (> 25 years) and under year-round sheep grazing. Local litter included mixtures of species of grasses and shrubs, separately.

Results

Grazing exclusion did not alter litter decomposition rates, either through changes in litter traits or in soil environment. Nevertheless, N released during grass litter decomposition was 286% higher in exclosures than in grazing communities. The difference was associated to changes in litter C:N ratio. The effects were maintained when results were integrated to the entire litter community.

Conclusion

Our study suggests that litter decomposition rates in arid steppes are strongly controlled by local drivers. Ungulate grazing does not have an important influence on litter mass loss, but it can exert a strong control on N flux during decomposition, by changing grass litter traits.

中文翻译：

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家养有蹄类动物的长期影响与干旱草原凋落物分解过程的当地控制

宗旨

干旱生态系统中的土壤过程受到资源稀缺性的强烈控制。放牧集约化可以通过多种途径引起生态系统过程的变化，给当地条件增加新的限制。我们关注放牧引起的凋落物性状和土壤环境的变化，这些变化可能影响温带草灌木草原的凋落物分解和氮动态。

方法

我们进行了三个垃圾袋分解实验来评估：i) 普通花园中凋落物性状的影响（异地），ii）使用外国普通垃圾基质（原位）的土壤环境的影响，以及 iii）凋落物特性和土壤环境（放牧与封闭社区，原位互惠移植）。在长期围栏（> 25 年）和全年放牧的羊群下，在三个区块中重复进行田间试验，成对地块。当地的垃圾包括草和灌木的混合物，分别。

结果

放牧排斥并没有通过凋落物特征或土壤环境的变化改变凋落物分解率。尽管如此，围栏的草屑分解过程中释放的氮比放牧社区高 286%。这种差异与垫料 C:N 比的变化有关。当结果被整合到整个垃圾社区时，效果得以保持。

结论

我们的研究表明，干旱草原的凋落物分解率受到当地驱动因素的强烈控制。有蹄类动物放牧对凋落物质量损失没有重要影响，但它可以通过改变草凋落物性状对分解过程中的 N 通量施加强有力的控制。