Background and Aims

Litter decomposition is poorly investigated in young temperate alley cropping (AC) systems but may be an integrative indicator to explore the early effect of trees on overall biological activity throughout soil profile. We evaluated the effect of four-year-old trees on recalcitrant-rooibos and labile-green tea mass loss at different soil depths at the Ramecourt AC experimental site.

Methods

In May 2021, tea bags were inserted within aluminum ingrowth bags and incubated at three depths 1.5 m from a reference tree for 6 months. The tea mass loss variability was analyzed according to factors: type of tea, type of system (AC, sole-crop control or CC and forest plantation control or FC), soil incubation depth, tree species and was correlated with fine roots and soil parameters.

Results

At 30 cm depth, the mass loss was significantly lower for rooibos than green tea regardless of the type of system, whereas at 50 cm and 100 cm depth, this difference was observed only in AC and FC. We observed a lower rooibos mass loss in AC than in CC at 100 cm depth. At 30 cm depth, soil mineral nitrogen content explained 23% of the rooibos tea mass loss variability whereas, soil organic matter content and fine root biomass within tea bags accounted for 50% of green tea mass loss variability.

Conclusion

We highlighted the ability of AC to slow recalcitrant litter decomposition in depth, however further works are needed to elucidate the processes leading to retarded decomposition.

中文翻译：

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用茶袋法揭示了温带小巷种植系统中不同土壤深度树木对凋落物质量损失的影响

 背景和目标

在年轻的温带林作（AC）系统中，凋落物分解的研究很少，但可能是探索树木对整个土壤剖面整体生物活性的早期影响的综合指标。我们在 Ramecourt AC 实验地点的不同土壤深度评估了四年树龄树对顽固性路易波士茶和不稳定绿茶质量损失的影响。

 方法

2021 年 5 月，将茶袋插入铝制长入袋中，并在距离参考树 1.5 m 的三个深度处培育 6 个月。根据以下因素分析茶叶质量损失变异性：茶叶类型、系统类型（AC、单作对照或 CC 和人工林对照或 FC）、土壤培育深度、树种，并与细根和土壤参数相关。

 结果

在 30 厘米深度，无论系统类型如何，路易波士茶的质量损失均显着低于绿茶，而在 50 厘米和 100 厘米深度，仅在 AC 和 FC 中观察到这种差异。我们观察到，在 100 厘米深度处，AC 中的路易波士质量损失低于 CC 中的质量损失。在 30 厘米深度，土壤矿物质氮含量解释了 23% 的路易波士茶质量损失变异性，而土壤有机质含量和茶袋内的细根生物量则解释了 50% 的绿茶质量损失变异性。

 结论

我们强调了 AC 深度减缓顽固性凋落物分解的能力，但需要进一步的工作来阐明导致分解延迟的过程。