Aim: Pinus dabeshanensis, an endemic species in the Dabieshan Mountains, has
significant scientific values for studying the taxonomy, phylogenetic relationships,
and distribution of the Pinus genus.
Currently, the wild population of P.
dabeshanensis is severely limited in natural regeneration and is critically
endangered. Here, we explored the potential effects of seed predation and
dispersal by animals on the regeneration of P.
dabeshanensis.
Methods: First, we investigated the seed production of P. dabeshanensis by focusing all the
adult trees in two 1-ha plots (n =
88). Second, by tracking the fate of 2,000 seeds, we compared the seed
predation and dispersal by animals between P.
dabeshanensis and three sympatric
tree species. These included two dominant native species, Castanea seguinii and Quercus
serrata, and an introduced species Pinus
armandii that is a sister species
of P. dabeshanensis, which all mainly depend on
scatter-hoarding animals for seed dispersal. Third, we compared the visitation
frequency of potential seed predators and dispersers between P. dabeshanensis and its sympatric species by using camera-trap surveys.
Results: The results showed that: (1) The seed production of P. dabeshanensis was low, with only 312
cones produced by 21 of the
88 adult trees surveyed, and the seed abortion rate reaching 51.89% ± 0.07%
(mean ± SE). (2) A total of 146 cones were collected to assess the seed predation
by birds, and 90 of them were pecked by birds which was significantly more than
un-pecked cones (n = 56), with an
average pecking intensity of 8.94% ± 0.55%. (3) Small rodents and
ground-dwelling birds (e.g., Garrulus
glandarius) were the main visitors to the seeds in the forest ground, and
visitation frequency varied significantly among different tree species.
Specifically, for P. dabeshanensis,
birds visited the seeds more frequently (n = 77) than rodents (n = 46). (4)
Seeds of C. seguinii were harvested
the fastest, followed by Q. serrata and P. dabeshanensis, while P. armandii were harvested the slowest.
(5) Of the 2,000 seeds released in the forest,
157 seeds were successfully dispersed, including
96 P. armandii seeds and 57 P. dabeshanensis seeds, which were
significantly more than C.
seguinii (3 seeds)
and Q. serrata (1 seed). (6) The seed dispersal
distance of C. seguinii was 13.9 ±
4.0 m (mean ± SE), followed by P. dabeshanensis (7.3 ± 0.8 m), P. armandii (3.8 ± 0.4 m) and Q. serrata (1.5 m, only one seed was
successfully dispersed).
Conclusion: In conclusion, both
rodents and birds are potential seed dispersers of
P. dabeshanensis.
Compared to sympatric tree species,
P. dabeshanensis does not suffer heavy
seed predation or limited seed dispersal, indicating that seed predation
pressure and seed dispersal limitation do not explain the poor natural
regeneration of
P. dabeshanensis. In addition, our results
suggest that the low seed production and high abortion rate may be important
factors hindering the natural regeneration of
P. dabeshanensis.