Astigarraga Julen, Andivia Enrique, Zavala Miguel A, Gazol Antonio, Cruz-Alonso Verónica, Vicente-Serrano Sergio M, Ruiz-Benito Paloma
Forest Ecology and Restoration Group, Department of Life Sciences, University of Alcala, Alcalá de Henares, Spain.
Department of Biodiversity, Ecology & Evolution, Complutense University of Madrid, Madrid, Spain.
Glob Chang Biol. 2020 Sep;26(9):5063-5076. doi: 10.1111/gcb.15198. Epub 2020 Jul 3.
Climate and forest structure are considered major drivers of forest demography and productivity. However, recent evidence suggests that the relationships between climate and tree growth are generally non-stationary (i.e. non-time stable), and it remains uncertain whether the relationships between climate, forest structure, demography and productivity are stationary or are being altered by recent climatic and structural changes. Here we analysed three surveys from the Spanish Forest Inventory covering c. 30 years of information and we applied mixed and structural equation models to assess temporal trends in forest structure (stand density, basal area, tree size and tree size inequality), forest demography (ingrowth, growth and mortality) and above-ground forest productivity. We also quantified whether the interactive effects of climate and forest structure on forest demography and above-ground forest productivity were stationary over two consecutive time periods. Since the 1980s, density, basal area and tree size increased in Iberian forests, and tree size inequality decreased. In addition, we observed reductions in ingrowth and growth, and increases in mortality. Initial forest structure and water availability mainly modulated the temporal trends in forest structure and demography. The magnitude and direction of the interactive effects of climate and forest structure on forest demography changed over the two time periods analysed indicating non-stationary relationships between climate, forest structure and demography. Above-ground forest productivity increased due to a positive balance between ingrowth, growth and mortality. Despite increasing productivity over time, we observed an aggravation of the negative effects of climate change and increased competition on forest demography, reducing ingrowth and growth, and increasing mortality. Interestingly, our results suggest that the negative effects of climate change on forest demography could be ameliorated through forest management, which has profound implications for forest adaptation to climate change.
气候和森林结构被认为是森林种群动态和生产力的主要驱动因素。然而，最近的证据表明，气候与树木生长之间的关系通常是非平稳的（即非时间稳定的），气候、森林结构、种群动态和生产力之间的关系是否平稳，或者是否正在被近期的气候和结构变化所改变，仍不确定。在此，我们分析了西班牙森林清查的三项调查，涵盖约30年的信息，并应用混合模型和结构方程模型来评估森林结构（林分密度、断面积、树木大小和树木大小不平等）、森林种群动态（内生长、生长和死亡率）以及地上森林生产力的时间趋势。我们还量化了气候和森林结构对森林种群动态和地上森林生产力的交互作用在两个连续时间段内是否平稳。自20世纪80年代以来，伊比利亚森林的密度、断面积和树木大小增加，树木大小不平等程度降低。此外，我们观察到内生长和生长减少，死亡率增加。初始森林结构和水分可利用性主要调节了森林结构和种群动态的时间趋势。在分析的两个时间段内，气候和森林结构对森林种群动态的交互作用的大小和方向发生了变化，表明气候、森林结构和种群动态之间存在非平稳关系。地上森林生产力因内生长、生长和死亡率之间的正平衡而增加。尽管生产力随时间增加，但我们观察到气候变化和竞争加剧对森林种群动态的负面影响，减少了内生长和生长，并增加了死亡率。有趣的是，我们的结果表明，气候变化对森林种群动态的负面影响可以通过森林管理得到缓解，这对森林适应气候变化具有深远意义。
