Hydraulic and mechanical dysfunction of Norway spruce sapwood due to extreme summer drought in Scandinavia
Hydraulic and mechanical dysfunction of Norway spruce sapwood due to extreme summer drought in Scandinavia
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DOI：
10.1016/j.foreco.2017.11.051
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发表时间：
2018-02
影响因子：
3.7
通讯作者：
S. Rosner;N. Gierlinger;Matthias M Klepsch;B. Karlsson;Rob Evans;S. Lundqvist;J. Svetlik;I. Børja;Lise Dalsgaard;K. Andreassen;S. Solberg;S. Jansen
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文献类型：
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作者：
S. Rosner;N. Gierlinger;Matthias M Klepsch;B. Karlsson;Rob Evans;S. Lundqvist;J. Svetlik;I. Børja;Lise Dalsgaard;K. Andreassen;S. Solberg;S. Jansen
预测的气候变化情景，如频繁发生的夏季干旱，是对北方针叶林健康的巨大威胁。我们发现了挪威云杉中具有管胞的木材容易出现水力和机械功能障碍的明显特征，提出了为什么这种现象是在严重的夏季干旱期间形成的，并假设了导致管胞塌陷和茎裂缝的机制。来自瑞典南部的树木表现出对干旱反应严重的迹象，即茎裂缝沿着树干，与健康、未受损的树木进行比较。调查的年轮包括2006年形成的年轮，这一年在研究地区夏季非常干燥。在挪威南部，我们调查了树木和没有干旱引起的顶梢枯死症状。分析了管胞腔径、细胞壁厚度及其各层的解剖特征（S1、S2和S3），利用拉曼技术研究了木质素在细胞壁和复合中层中的分布，并进行了水力流动和收缩实验，结果表明，尽管有皱缩迹象的年轮管胞的切向管腔直径大于“正常”年轮管胞，年轮，我们得出结论，管胞壁的崩溃主要取决于壁厚，这是在很大程度上由遗传决定。云杉树生产的早材细胞壁极薄，在干旱的影响下，可能会出现细胞壁坍塌和内部裂缝。我们还提出了一种新的诊断工具，用于检测个人，容易细胞壁坍塌和干裂纹：透明带，即带在新鲜边材非常薄的细胞壁和不均匀的木质素分布在S-层和化合物中间层，失去了他们的液压功能，由于严重的夏季干旱的时期。检测基因型与清晰的带可能是有用的，对个人的早期选择，容易在严重的夏季干旱的影响下，干裂纹，也为早期降级的日志容易开裂在工业窑干燥。
Projected climate change scenarios such as frequently occurring dry summer spells are an enormous threat to the health of boreal conifer forests. We identified visible features indicating wood with tracheids predisposed for hydraulic and mechanical dysfunction in Norway spruce, suggest why this is formed during severe summer drought and hypothesised on mechanism that would cause tracheid collapse and stem cracks.Trees from southern Sweden that showed signs of severe reaction to drought, i.e. stem cracks along the trunk, were compared to healthy, undamaged trees. Rings investigated included those formed in 2006, a year with an extremely dry summer season in the study region. In southern Norway, we investigated trees with and without drought-induced top dieback symptoms. We analysed anatomical features such as tracheid lumen diameter, thickness of cell wall and its various layers (S1, S2 and S3), applied Raman imaging in order to get information on the lignin distribution in the cell wall and the compound middle lamellae and performed hydraulic flow and shrinkage experiments.Although tracheids in annual rings with signs of collapse had higher tangential lumen diameters than those in “normal” annual rings, we conclude that collapse of tracheid walls depends mainly on wall thickness, which is genetically determined to a large extent. Spruce trees that produce earlywood with extremely thin cell walls can develop wall collapse and internal cracks under the impact of dry spells. We also present a new diagnostic tool for detecting individuals that are prone to cell wall collapse and stem cracks: Lucid bands, i.e. bands in the fresh sapwood with very thin cell walls and inhomogeneous lignin distribution in the S-layers and the compound middle lamellae that lost their hydraulic function due to periods of severe summer drought. The detection of genotypes with lucid bands could be useful for an early selection against individuals that are prone to stem cracks under the impact of severe summer drought, and also for early downgrading of logs prone to cracking during industrial kiln drying.