Forest gap, a dominant form of small-scale disturbance in secondary forests, is the beginning of forest cycle regeneration. Gap size and within-gap position, as two key characteristics of gap structure, can affect the tree regeneration by changing microenvironments.
After gap formation, many sprouts commonly occur from stumps and roots of fell trees. However, previous studies used to concentrate on the influence of gap structure on seed regeneration and ignore the significance of sprout regeneration.
Promoting sprout regeneration of dominant tree species by creating forest gap is a crucial measure to recover secondary forests. Therefore, researchers at Institute of Applied Ecology of Chinese Academy of Sciences want to explore the effects of gap size and within-gap position on sprout regeneration.
They established twelve artificial gaps with three size types (large gap of the size > 600 m2, medium gap of the size 300~600 m2, small gap of the size < 300 m2) in the secondary forests at Qingyuan Forest Chinese Ecosystem Research Network (CERN), Chinese Academy of Sciences, in 2015.
Quercus mongolica,Acer monoandTilia mandshuricaare three dominant tree species in the secondary forests with contrasting shade tolerance and all of them have strong sprout ability.
Theymeasured the growth and photosynthesis of two-year-old stump sprouts of these three species at five within-gap positions (north, south, east, west and center) from large-medium gaps and at the center of gaps from two gap sizes (large gap and small gap) during the growing season in 2016.
The results indicated that of all three tree species with different shade tolerance.
OnlyQ. mongolica(shade intolerant tree species) andA. mono(intermediate shade tolerance tree species) were sensitive to the changing environment due to the variation of gap size and within-gap position at the early stage of gap formation. The photosynthesis and growth of the two could be promoted in the large gap and at the central position of gaps with moderate light condition.
Therefore, creating gaps by controlling the gap size and within-gap position where the target species are located can facilitate sprout regeneration in secondary forests.
The study was supported by grants from the National Natural Science Foundation of China and the Youth Innovation Promotion Association of Chinese Academy of Sciences.
Secondary forests, derived from the natural regeneration of primary forests after destructive disturbances, have become major forest resources worldwide. Compared with primary forests, several problems have been observed in broadleaved secondary forests, including unoptimizable stand structure, unsuccessful natural regeneration of dominant tree species and unsustainability in both ecosystem services and productivity.