The combined impacts of deep shade and drought on the growth and biomass allocation of shade-tolerant woody seedlings
The combined impacts of deep shade and drought on the growth and biomass allocation of shade-tolerant woody seedlings
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DOI：
10.1007/s00442-002-0873-0
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发表时间：
2002-04
期刊：
影响因子：
2.7
通讯作者：
L. Sack;P. Grubb
中科院分区：
文献类型：
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作者：
L. Sack;P. Grubb
为了检验干旱对第一季耐荫木本幼苗在低辐照度和高辐照度下生长和生物量分配的影响是否存在差异，以马缨丹荚莲属植物（Viburnum lantana, V.奥普鲁斯，V.红花和常春藤以两种浇水频率×三种辐照度在盆中生长。最近文献中的假设有多种预测，相对于中度遮荫，干旱对深荫下幼苗相对生长率（RGR）的影响更强、更弱或相等。实验辐照度水平选择在温带落叶林幼苗的林下或空地的典型范围内：3-4% 日光（低红色：远红色阴影）、3-4% 日光（中性阴影）和 30-40% 日光（中性阴影）。浇水“频繁”（每 3-4 天一次）或“不频繁”（在为期 8 周的实验期间浇水五次），产生低至 –0.03 MPa 和 –2 MPa 的土壤基质势。为了防止辐照和浇水处理的相互作用，每棵幼苗都生长在一个“遮荫塔”中，周围是一片未覆盖的草丛（羊茅），无论幼苗的种类或其辐照处理如何，它都会以相同的速度耗尽盆水。遮荫影响所有物种：3.5% 日光下的幼苗生长速度是 35% 日光下干质量 RGR 的 56-73%。低红色：远红色色调使 Hederato 的 RGR 降低为其中性色调值的 68%。不频繁浇水显着降低了马缨丹和V的RGR。 opulus，在辐照度处理中的比例大致相同。不频繁浇水并没有显着改变任何物种在辐照处理中的生物量分配。深荫和干旱对幼苗生长和生物量分配的这种正交影响表明，森林幼苗物种在辐照度和供水组合方面存在巨大的生态位分化潜力，并提出了一种乘法效应方法，用于模拟具有不同辐照度和供水组合的微场地中幼苗的表现。
To test whether the impact of drought on the growth and biomass allocation of first-season shade-tolerant woody seedlings in low irradiance differs from that in high irradiance, seedlings ofViburnum lantana,V. opulus,V. tinusandHedera helixwere grown in pots at two watering frequencies × three irradiances. Hypotheses in the recent literature variously predict that drought will have a stronger, weaker or equal impact on seedling relative growth rate (RGR) in deep shade relative to that in moderate shade. Experimental irradiance levels were selected in the typical range for temperate deciduous forest seedlings in either understorey or clearings: 3–4% daylight (low red: far-red shade), 3–4% daylight (neutral shade), and 30–40% daylight (neutral shade). Watering was 'frequent' (every 3–4 days) or 'infrequent' (five times during the 8-week experiment), producing soil matric potentials as low as –0.03 MPa, and –2 MPa. To prevent the interaction of irradiance and watering treatments, each seedling was grown in a 'shade tower' that was surrounded by an uncovered sward of grass (Festuca rubra), which depleted pot water at the same rate regardless of the species of seedling, or its irradiance treatment. Shading affected all species: seedlings in 3.5% daylight grew at 56–73% of their dry-mass RGR in 35% daylight. Low red: far-red shade reduced the RGR ofHederato 68% of its value in neutral shade. Infrequent watering significantly reduced the RGR of onlyV.lantanaandV. opulus, by approximately the same proportion across irradiance treatments. Infrequent watering did not significantly alter any species' biomass allocation across irradiance treatments. Such orthogonal impacts of deep shade and drought on seedling growth and biomass allocation indicate a large potential for niche differentiation at combinations of irradiance and water supply for species of forest seedlings, and suggest a multiplicative-effects approach for modelling seedling performance in microsites with different combinations of irradiance and water supply.