From canopy complementarity to asymmetric competition: The negative relationship between structural diversity and productivity during succession. (29th November 2021)

• Record Type: Journal Article
• Authors: Yi, Xiaoxia; Wang, Ningning; Ren, Haibao; Yu, Jianping; Hu, Tianyu; Su, Yanjun; Mi, Xiangcheng; Guo, Qinghua; Ma, Keping
• Is Part Of: Journal of ecology. Volume 110:Number 2(2022)
• Page Start: 457
• Page End: 465
• Publication Date: 2021-11-29
• Subjects: asymmetric competition -- canopy structural diversity -- coarse woody productivity -- community composition -- disturbance regime -- leaf area index -- species diversity; Plant ecology -- Periodicals; 577.05
• DOI: 10.1111/1365-2745.13813
• Languages: English
• ISSNs: 0022-0477

Abstract

Abstract: Positive relationships between structural diversity and forest productivity have been documented in controlled experiments and early secondary forests, however, negative relationships have also been observed in late successional forests. The mechanisms causing observed relationships between structural diversity and productivity are not well‐established, but complementarity among crowns and asymmetric competition have been suggested. We used LiDAR and repeated census data to examine the relationship between canopy structural diversity and productivity in nine 1‐ha subtropical forest plots along a disturbance gradient in southeastern China. We quantified the relative importance of community composition, species diversity, canopy structural diversity, leaf area index (LAI) and disturbance regime on productivity using piecewise structural equation modelling. We also tested how vertical leaf area distribution affected productivity. Contrary to many prior observations, we found a negative relationship between canopy structural diversity and forest productivity. The negative effect may stem from asymmetric competition between overstorey and understorey leaves, leading to a lower leaf area efficiency (i.e. wood production per leaf area). Asymmetric competition was suggested by a negative relationship between understorey leaf area and total productivity. Changes in community composition over the disturbance gradient, but not species diversity, had a significant effect on productivity. Synthesis . Our study suggests that leaf area and canopy structural diversity have contrasting effects on productivity in this subtropical forest, and this needs to be considered when estimating rates of carbon sequestration in secondary forests. The negative effect of asymmetric competition on productivity is comparable to that of the shift in species composition over succession, highlighting the role of canopy structural diversity in shaping forest productivity. Abstract : Contrary to many prior observations, we found a negative relationship between canopy structural diversity and coarse woody productivity in the subtropical forests along a disturbance gradient in southeastern China. The negative effect may stem from asymmetric light competition between overstorey and understorey crowns in structurally complex forests, leading to a lower leaf area efficiency. 摘要: 很多之前的研究在控制实验和演替早期的次生林中发现了结构多样性对生产力的正效应, 但另一些研究在演替后期的森林中发现结构多样性对生产力具有负效应。目前结构多样性和生产力关系的生态学机制尚不完善, 但是可能的机制是上层和下层树冠之间利用光资源的互补效应或不对称竞争。 我们用9个不同演替阶段的1‐ha森林样地的长期调查数据和激光雷达数据来探究结构多样性与生产力的关系。首先我们用结构方程模型检验了群落物种组成、物种多样性、冠层结构多样性、叶面积指数和演替阶段等多个因素对生产力的影响。同时, 我们进一步检验了叶面积的垂直分布对生产力的影响。 与以往大多数研究结论相反, 我们发现冠层结构多样性对生产力存在负效应, 这种负效应可能源于上层和下层树冠对光资源的不对称竞争, 导致了下层树冠较低的叶面积利用效率。同时, 林下层叶面积与总体生产力之间的负关系为不对称竞争机制提供了进一步的证据。同时, 我们还发现, 演替过程中群落物种组成的变化显著影响生产力, 但物种多样性的变化并不影响生产力。 我们的研究表明, 叶面积总量和冠层结构多样性对生产力的影响相反, 在估计次生林的碳固存速率时应同时考虑叶面积和冠层结构多样性。不对称竞争与演替过程中物种组成变化对生产力的作用强度相当, 凸显了林冠结构多样性在决定森林生产力中的重要性。