TY - JOUR
T1 - Gaps present a trade-off between dispersal and establishment that nourishes species diversity
AU - Terborgh, John
AU - Huanca Nuñez, Nohemi
AU - Feeley, Kenneth
AU - Beck, Harald
N1 - Funding Information:
We are grateful to the managers of Per??s Manu National Park (SERNANP, and earlier, INRENA and DGFF) for annually issuing us permits to conduct research at Cocha Cashu for more than 40 yr. Research assistants, far too numerous to name, contributed indispensable support in data gathering and data transcription. We also thank two anonymous reviewers for helpful suggestions. Financial support of the Andrew Mellon Foundation and National Science Foundation (DEB0742830) is gratefully acknowledged. J. Terborgh designed the project, participated in the fieldwork and was lead author; N. H. Nu?ez participated in the field work and conducted several of the analyses; K. Feeley and H. Beck contributed essential data, and N. H. Nu?ez, K. Feeley, and H. Beck offered helpful comments on the manuscript.
PY - 2020/5/1
Y1 - 2020/5/1
N2 - We took advantage of two natural experiments to investigate processes that regulate tree recruitment in gaps. In the first, we examined the recruitment of small and large saplings and trees into 31 gaps resulting from treefalls occurring between 1984 and 2015 in the 2.25-ha core area of a 4-ha tree plot at Cocha Cashu in Perú. In the second, we identified the tallest saplings recruiting into 69 gaps created during a violent wind storm in February 2000. In the established tree plot, we were able to compare the composition of saplings in the disturbance zones of gaps prior to, during, and subsequent to the period of gap formation. Recruitment in gaps was compared with that in “nofall” zones, areas within the plot that had not experienced a treefall at least since the early 1980s. Our results confirmed earlier findings that a consistently high proportion (~60%) of established saplings survived gap formation. Light demanding species, as proxied by mortality rates, recruited under all conditions, but preferentially during periods of gap formation, a pattern that was especially strong among gap pioneers. Similar results were noted, separately, for small and large saplings and trees recruiting at ≥10 cm dbh. One hundred percent of previously untagged trees recruiting into gaps in the first post-disturbance census were gap pioneers, suggesting rapid development. This conclusion was strongly supported in a follow-up survey taken of 69 gaps 19 months after they had been synchronously created in a wind storm. Ten species of gap pioneers, eight of which are not normally present in the advance regeneration, had attained heights of 6–10 m in 19 months. The 10 gap pioneers were dispersed, variously, by primates, bats, birds, and wind and reached maximum frequency in different-sized gaps (range '100 m2 to '1,000 m2). Both gap size and limited dispersal of zoochorous species into gaps serve as filters for establishment, creating a complex mosaic of conditions that enhances species diversity.
AB - We took advantage of two natural experiments to investigate processes that regulate tree recruitment in gaps. In the first, we examined the recruitment of small and large saplings and trees into 31 gaps resulting from treefalls occurring between 1984 and 2015 in the 2.25-ha core area of a 4-ha tree plot at Cocha Cashu in Perú. In the second, we identified the tallest saplings recruiting into 69 gaps created during a violent wind storm in February 2000. In the established tree plot, we were able to compare the composition of saplings in the disturbance zones of gaps prior to, during, and subsequent to the period of gap formation. Recruitment in gaps was compared with that in “nofall” zones, areas within the plot that had not experienced a treefall at least since the early 1980s. Our results confirmed earlier findings that a consistently high proportion (~60%) of established saplings survived gap formation. Light demanding species, as proxied by mortality rates, recruited under all conditions, but preferentially during periods of gap formation, a pattern that was especially strong among gap pioneers. Similar results were noted, separately, for small and large saplings and trees recruiting at ≥10 cm dbh. One hundred percent of previously untagged trees recruiting into gaps in the first post-disturbance census were gap pioneers, suggesting rapid development. This conclusion was strongly supported in a follow-up survey taken of 69 gaps 19 months after they had been synchronously created in a wind storm. Ten species of gap pioneers, eight of which are not normally present in the advance regeneration, had attained heights of 6–10 m in 19 months. The 10 gap pioneers were dispersed, variously, by primates, bats, birds, and wind and reached maximum frequency in different-sized gaps (range '100 m2 to '1,000 m2). Both gap size and limited dispersal of zoochorous species into gaps serve as filters for establishment, creating a complex mosaic of conditions that enhances species diversity.
KW - Amazonia
KW - Cocha Cashu Biological Station
KW - Perú
KW - gap
KW - gap pioneer
KW - sapling recruitment
KW - sapling survivorship
KW - seed dispersal
KW - treefall
KW - tropical forest
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U2 - 10.1002/ecy.2996
DO - 10.1002/ecy.2996
M3 - Article
AN - SCOPUS:85081231350
VL - 101
JO - Ecology
JF - Ecology
SN - 0012-9658
IS - 5
M1 - e02996
ER -