In Turkish forests restored after a fire about 75 years ago, it is still noticeable which trees were planted then. Under dense fir, plant diversity drops sharply, whereas pine and cedar plots leave far more room for grasses and shrubs. The decision about species made after the fire proved long-lasting: it continues to determine what the forest looks like today.
In November 2026, a paper was published in the journal Plant Biosystems that studied several historical experimental reforestation plots in Turkey. The scientists compared stands of Scots pine (Pinus sylvestris), Nordmann fir subspecies equi-trojani (Abies nordmanniana subsp. equi-trojani) and Lebanon cedar (Cedrus libani) with stands of black pine subspecies pallasiana (Pinus nigra subsp. pallasiana), which served for comparison. In each stand type, they measured canopy closure and assessed the species richness of the understory in small plots.
The differences were most pronounced in the fir stands. At canopy closure of 88–97 percent, only 24 plant species were counted there, and in individual plots — from 3,2 to 7,0 species. Shade-tolerant plants adapted to a moist and shaded environment predominated. In the pine and cedar stands, species richness was noticeably higher — from 36 to 43 species.
An important indicator is beta diversity, that is, how much plant composition changes from one plot to another. In the fir stands it was 1,57–2,44, in the cedar stands — about 1,95, whereas in black pine — 0,96–1,10, and in Scots pine — 1,16–1,38. In other words, neighboring plots under fir and cedar differ from one another noticeably more than under pines. The analysis showed that understory composition largely depends on light availability, and that, in turn, is determined by tree species and canopy density.
Particularly indicative is laurel-leaved rockrose (Cistus laurifolius) — a shrub typical of places of recent fires. As the canopy closed, its abundance fell: the correlation coefficient was r = −0,38 at p = 0,015. This means that the choice of species during restoration influences not only the trees but also the subsequent succession of plant communities — succession.
A similar picture is seen in other post-fire forests of Turkey. In a study on Turkish pine (Pinus brutia), the number of species did not differ significantly between restoration variants, but the composition and structure of the vegetation changed noticeably: active measures shifted the community from woody-shrubby to annual-grassy. This is a reminder that “restoring a forest” and “restoring a plant community” are not the same thing.
The results yield a practical conclusion: when planning post-fire restoration, it is important to consider not only the fact of planting but also which species are chosen and what light regime they will create beneath the canopy. Such decisions can influence the understory for decades. The advice to choose species that produce moderate canopy closure is a reasonable extrapolation of the data: the study shows a relationship between canopy closure and diversity, but a universal rule for all forests does not follow directly from it.
