Context

In temperate hardwood forests, increased intensity of soil and canopy disturbances tends to increase species richness due to the establishment of numerous early-successional plant species. However, while competitive pioneer species from early stages of succession can become recalcitrant and alter patterns of natural regeneration, very few studies have examined longer-term effects of these treatments on plant biodiversity.

Aims

In this study, we investigated mid-term (ca. 20 years) effects of different regeneration treatments with varying soil and canopy disturbance intensities. We compared understory plant communities in temperate hardwood forests from all the South of Quebec (Canada).

Methods

Using circular experimental plots of 1962.5 m² (radius = 25 m), we measured taxonomic and functional diversity indices and soil properties using four levels of disturbance intensity in six temperate hardwood forests of Quebec distributed along a longitudinal gradient. Reference forests, i.e. control forests with no silvicultural treatment known for ≥ 80 years, were compared to 20-year-old single-tree selection cuts, group-selection cuts and group-selection cuts with soil scarification.

Results

Species richness in both group-selection treatments was higher than that in reference forests. Plant equitability and beta diversity among sites in both group-selection treatments were lower than in single-tree selection cuts and control forests. More intense treatments contributed to the mid-term persistence of recalcitrant competitor species (e.g. Rubus idaeus L., Prunus pensylvanica L.f.) whereas soil scarification appears to have negative sustained effects on species known to be sensitive to regeneration treatments (e.g. Monotropa uniflora L., Dryopteris spinulosa Kuhn).

Conclusions

In temperate hardwood forests of Southern Quebec, silvicultural treatments of higher intensities resulted in detrimental effects on soil properties, especially in the surface horizon, 20 years after disturbance. This legacy, in turn, affected the composition and diversity of understory plant communities. The more intense silvicultural treatments contributed to the persistence of pioneer species better adapted to a wider range of environmental conditions and resulted in a decrease in understory plant community heterogeneity among sites. Conversely, single-tree selection cutting appeared to be the most appropriate silvicultural treatment for maintaining soil functions and heterogeneity of understory plant communities after 20 years; composition and structure being similar to long-undisturbed forests.

中文翻译：

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增加再生处理强度降低了扰动20年后温带阔叶林下层的β多样性

语境

在温带阔叶林中，由于大量早期演替植物物种的建立，土壤和树冠干扰强度的增加往往会增加物种丰富度。然而，虽然来自演替早期阶段的竞争先驱物种可能会变得顽固并改变自然再生的模式，但很少有研究检查这些处理对植物生物多样性的长期影响。

目标

在这项研究中，我们调查了具有不同土壤和冠层干扰强度的不同再生处理的中期（约 20 年）影响。我们比较了魁北克（加拿大）南部所有温带阔叶林中的林下植物群落。

方法

使用 1962.5 m ²（半径 = 25 m）的圆形实验地块，我们使用魁北克六个温带阔叶林沿纵向梯度分布的四个干扰强度水平测量了分类和功能多样性指数和土壤特性。参考森林，即已知 ≥ 80 年未进行造林处理的对照森林，与 20 年树龄的单树选择砍伐、组选择砍伐和土壤松散化的组选择砍伐进行了比较。

结果

两种组选择处理的物种丰富度均高于参考森林。两种组选择处理的地点之间的植物公平性和β多样性低于单树选择砍伐和对照森林。更强烈的处理有助于顽固的竞争物种（例如Rubus idaeus L.、Prunus pensylvanica Lf）的中期持续存在，而土壤松土似乎对已知对再生处理敏感的物种（例如Monotropa uniflora L.、Dryopteris spinulosa Kuhn)。

结论

在魁北克南部的温带阔叶林中，较高强度的造林处理会对土壤特性产生不利影响，尤其是在干扰 20 年后的地表层。反过来，这种遗产影响了林下植物群落的组成和多样性。更强烈的造林处理有助于先驱物种的持续存在，更好地适应更广泛的环境条件，并导致林下植物群落异质性降低。相反，单树选择扦插似乎是 20 年后维持土壤功能和林下植物群落异质性的最合适的造林处理；组成和结构类似于长期未受干扰的森林。