3.3 | Primary seed dispersers
The distribution of four primary seed dispersers and their overlap ratio
with different pine distribution areas are shown in Fig. 2 and table 4,
respectively.
N. caryocatactes is a typical coniferous forest bird that is
mainly distributed across Northeast China (Fig. 2a). The distribution
areas of N. caryocatactes cover 84.56% of P. armandii’sdistribution area. Additionally, it overlaps with all the
distribution areas of the other pine trees, including P.
koraiensis, P. pumila, and P. sibirica . Among the other pines of
undetermined seed dispersal trends by N. caryocatactes , part of
the distribution area of P. dabeshanensis and P.
fenzeliana is are in the active area of N. caryocatactes , where
the distribution areas of P. gerardiana and P. bungeanaare completely within the range of N. caryocatacte . This bird is
very likely to eat the seeds of these pines, which indicates its
potential role as their seed disperser.
S. vulgaris is mainly distributed across Northeastern to North
China and is also present in some mountain forests in Northwestern China
(Fig. 2b). At present, S. vulgaris have been reported to disperse
the seeds of P. koraiensis and P. armandii . The natural
geographical distribution of these two pines are all within the activity
range of S. vulgaris . In addition, the distribution areas ofS. vulgaris coincided with the geographical distribution area ofP. sibirica and north of that as well as 7.20% of the
distribution area of P. armandii , which also overlaps with
11.51% of the distribution area of P. bungeana . Therefore,S. vulgaris is likely to feed on the seeds of P. sibirica,
P. armandii , and P. bungeana and disperses their seeds.
S. davidianus is mainly found in North China to Southwest China
and East China to Midwest China (Fig. 2c). This covers all the
geographical distribution areas of P. dabeshanensis , P.
bungeana , 75.71% of P. armandii , and 6.16% of P.
koraiensis . P. armandii and P. koraiensis have related
reports in terms of seed dispersal by S. davidianus , where
91.61% of the geographical distribution areas of P. bungeana ,P. dabeshanensis, and P. fenzeliana, with punctate
distribution, overlap with that of S. davidianus , hence, S.
davidianus is likely to feed on the seeds of the aforementioned pines
and disperse their seeds through storage behavior.
T. sibiricus are mainly distributed in the northeast to the
midwest of China (Fig. 2d). At present, there have been reports
regarding the effect of T. sibiricus on the seed dispersal ofP. koraiensis and P. armandii, where its geographic
distribution covers 94.19% of the area of P. koraiensis and
57.21% of P. armandii’s area. In addition, 49.58% of the
geographical distribution areas of P. bungeana, part of P.
fenzeliana , the total area of both P. pumila and P.
sibirica coincided with that of T. sibiricus , in which it is
likely to practice foraging and store behavior on the pine seeds, which
would affect their seed dispersal.
Generally speaking, the distribution of the primary seed dispersers and
the eight large-seeded pines showed a high degree of consistency, where
central spreading of the Pinus plants was observed. The natural
distribution areas of P. dabeshanensis , P. koraiensis ,P. armandii , and P. sibirica were all within the range of
their main seed dispersers. For pines of undetermined seed dispersal
trends, there were potential seed dispersers in some or all of their
distribution areas. For each seed disperser species, its distribution
range was wide with complete or partial overlaps with four or more
species of the large-seeded pines. In addition to P. gerardiana ,
which is distributed at the highest altitude of 2700 m, there were three
or more seed dispersers in the distribution area of the other seven pine
species, but two of them were only a small population with a spotty
pattern of distribution.