School of Geographical and Earth Sciences, University of Glasgow, Scotland, UK.
Institute of Forest Growth and Forest Computer Sciences, Technische Universität Dresden, Dresden, Germany.
Commun Biol. 2021 May 5;4(1):513. doi: 10.1038/s42003-021-02044-x.
The occurrence of natural root grafts, the union of roots of the same or different trees, is common and shared across tree species. However, their significance for forest ecology remains little understood. While early research suggested negative effects of root grafting with the risk of pathogen transmission, recent evidence supports the hypothesis that it is an adaptive strategy that reduces stress by facilitating resource exchange. Here, by analysing mangrove root graft networks in a non-destructive way at stand level, we show further evidence of cooperation-associated benefits of root grafting. Grafted trees were found to dominate the upper canopy of the forest, and as the probability of grafting and the frequency of grafted groups increased with a higher environmental stress, the mean number of trees within grafted groups decreased. While trees do not actively 'choose' neighbours to graft to, our findings point to the existence of underlying mechanisms that regulate 'optimal group size' selection related to resource use within cooperating networks. This work calls for further studies to better understand tree interactions (i.e. network hydraulic redistribution) and their consequences for individual tree and forest stand resilience.
天然根嫁接的发生，即同一树种或不同树种的根系结合，是普遍存在且为不同树种所共有的。然而，其对森林生态的意义仍知之甚少。尽管早期的研究表明根嫁接可能有传播病原体的风险，但最近的证据支持了这样一种假设，即根嫁接是一种适应性策略，可以通过促进资源交换来减轻压力。在这里，我们通过在林分水平上以非破坏性的方式分析红树林根嫁接网络，进一步证明了根嫁接与合作相关的益处。嫁接树被发现占据了森林上层树冠的主导地位，并且随着嫁接概率和嫁接群体的频率随着环境压力的增加而增加，嫁接群体内的平均树木数量减少。虽然树木不会主动“选择”要嫁接的邻居，但我们的研究结果表明，存在调节与合作网络中资源利用相关的“最佳群体大小”选择的潜在机制。这项工作呼吁进一步研究，以更好地了解树木之间的相互作用（即网络水力再分配）及其对单个树木和森林林分恢复力的影响。
