Changes in community diversity and dynamics after fires in Mediterranean ecosystems are rarely investigated more than a few years after the fire even though pronounced changes can be expected in the longer term due to substitution of canopy species. Pinus halepensis is strongly promoted by wildfire and should therefore be gradually substituted by Quercus species as the time since the last fire increases. We hypothesized that this tree substitution would cause changes in understorey plant diversity by changing resource availability and the abundance and properties of woody debris, leading to changes in biogeochemical processes. To test this hypothesis, we investigated the effect of the time since last fire on vascular plant composition and diversity by studying a 130 years post-fire chronosequence in mixed Mediterranean forests. The canopy composition went from domination by Pinus halepensis to domination by Quercus 70 years after the most recent fire. This transformation was associated with a change in the understorey involving a rarefaction of species present during the first decades after the fire. The plant density or cover also changed with time since the last fire, indicating a succession driven by species rarefaction rather than substitution. The mean richness and Shannon diversity per quadrat were highest shortly after the fire, and were significantly lower 70 or more years after the last fire. Fires are important for supporting highly diversified fire-dependent plant communities, and total plant richness decreases monotonically over time after fires, suggesting that fire suppression may reduce diversity in Mediterranean forests.

在地中海大火发生后的几年中，很少对地中海生态系统大火发生后群落多样性和动态的变化进行调查，尽管从长远来看，由于冠层物种的替代，可以预期会有明显的变化。野火强烈促进了哈氏松，因此应逐渐用栎属取代自上次大火以来的时间逐渐增加。我们假设这种树木替代会通过改变资源的可获得性以及木屑的丰度和性质而引起林下植物多样性的变化，从而导致生物地球化学过程的变化。为了验证这一假设，我们通过研究地中海混交林火灾后130年的时间序列，研究了自上次火灾以来的时间对维管植物成分和多样性的影响。冠层组成从哈尔滨松的控制到栎属的控制最近一次大火过了70年。这种转变与底层的变化有关，底层的变化涉及大火后最初几十年中存在的物种的稀有性。自上次大火以来，植物的密度或覆盖率也随时间而变化，表明其演替是由物种稀少而不是替代引起的。火灾后不久，每平方度的平均富裕度和香农多样性最高，而上次火灾后70年或更长时间则显着降低。火灾对于支持高度多样化的依赖火的植物群落非常重要，火灾后总植物丰富度会随时间单调下降，这表明抑制火势可能会减少地中海森林的多样性。