Seed dispersal of Korean pine Pinus koraiensis labeled by two different tags in a northern temperate forest, northeast China

Two types of tagging methods, i.e., a 1 × 3-cm tin tag attached to seed with a 10- to 12-cm metal wire (total weight 0.32 g) and a 2 × 4-cm white plastic tag fastened to seed with an identical metal wire (total weight 0.57 g) were used to study their effects on seed dispersal of Korean pine by small rodents. A total of 600 seeds were released to assess four main points: (1) difference in seed survival rates, (2) difference in caching behaviors of small rodents, (3) difference in dispersal distances, and (4) proportion of seed missing. The results demonstrated that seed removal for wire-plastic-tagged seeds was faster than that for wire-tin-tagged seeds. There was no apparent difference in the proportion of seeds eaten in situ (42% and 52% for wire-plastic-tagged seeds and wire-tin-tagged seeds, respectively). We found 41% and 1% of seeds were moved and hoarded for wire-plastic-tagged seeds and wire-tin-tagged seeds, respectively. However, 2.33% and 14% of seeds were missing, and their ultimate fates were not known for wire-plastic-tagged seeds and wire-tin-tagged seeds, respectively. We found the wire-plastic-tagged seeds easier to track than the wire-tin-tagged seeds due to the fact that the white plastic tags were more salient than the tin tags in field environments. The average dispersal distances were 4.11 ± 2.40 m and 3.01 ± 2.06 m for wire-plastic-tagged seeds and wire-tin-tagged seeds, respectively, and showed great difference. Despite most being eaten in situ or after removal, 41% of seeds were cached for wire-plastic-tagged seeds, much more than for wire-tin-tagged seeds. A total of 71 primary caches (123 seeds) were found for wire-plastic-tagged seeds, with the average and maximum cache sizes being 1.73 and 6, respectively. However, only three caches were found, and cache size was equal to one for wire-tin-tagged seeds. The above data suggests there is some uncertainty in different tagging methods to used track seed fates. Despite their effectiveness in helping to trace seed dispersal or movement by seed-dispersing rodents, different tagging methods—including size, color, and mass—need to be fully understand in enclosure experiments .