Background and aims

Understanding soil nematode responses is crucial for assessing and predicting the effects of afforestation on soil food webs. While we possess good knowledge of the nematode taxonomic indicators (e.g., abundance and richness), the response of nematode trait distribution (e.g., body size) to afforestation, offering insights into community assembly, remains poorly understood.

Methods

We investigated the influence of afforestation (19-, 11- and 3-year-old forests and unplanted meadows) on soil nematode structure and trait distribution in a subalpine ecosystem.

Results

Taxonomically, afforestation did not enhance nematode community performance, e.g., nematode abundance in 11- and 3-year-old forests was lower than in unplanted meadows. However, afforestation significantly impacted distributions of body size. In 11- and 19-year-old forests, nematodes tended to be large-bodied, with body sizes more evenly distributed and less skewed, suggesting niche differentiation. However, in 3-year-old forests and unplanted meadows, nematodes were highly concentrated around smaller sizes, with only a few large-bodied individuals, indicating environmental filtering. According to redundancy analysis, we found that small-bodied nematodes in 3-year-old forests and unplanted meadows related to poor soil fertility with high carbon: nitrogen ratio, while large-bodied nematodes in 11- and 19-year-old forests were associated with fertile soils, as indicated by high nitrate and available phosphorus.

Conclusion

Our study reveals assembly rules for soil nematodes: afforestation leads to the replacement of smaller nematodes in meadows with larger ones in older forests, mainly due to increased niche differentiation. This research highlights the importance of trait distribution in understanding afforestation’s ecological impacts on soil food webs.

中文翻译：

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从亚高山生态系统中的体型分布揭示线虫对造林的响应

 背景和目标

了解土壤线虫响应对于评估和预测植树造林对土壤食物网的影响至关重要。虽然我们对线虫分类指标（例如，丰度和丰富度）有很好的了解，但线虫性状分布（例如，体型）对造林的响应，为群落组装提供了见解，仍然知之甚少。

 方法

我们研究了植树造林 （19 年、11 年和 3 年生森林和未种植的草地） 对亚高山生态系统中土壤线虫结构和性状分布的影响。

 结果

从分类学上讲，植树造林并没有提高线虫群落的表现，例如，11 年和 3 年生森林的线虫丰度低于未种植的草地。然而，植树造林显着影响了体型的分布。在 11 年和 19 年树龄的森林中，线虫往往体型较大，体型分布更均匀，歪斜较小，表明生态位分化。然而，在 3 年生森林和未种植的草地中，线虫高度集中在较小的尺寸周围，只有少数体型较大的个体，表明存在环境过滤。根据冗余分析，我们发现 3 年生森林和未种植草甸中的小体线虫与土壤肥力差和高碳氮比有关，而 11 年和 19 年生森林中的大体线虫与肥沃的土壤有关，如高硝酸盐和高有效磷所示。

 结论

我们的研究揭示了土壤线虫的组装规则：植树造林导致草甸中较小的线虫被老森林中较大的线虫取代，这主要是由于生态位分化的增加。这项研究强调了性状分布在理解植树造林对土壤食物网的生态影响方面的重要性。