TITLE:
Structure of Isolated Acer grandidentatum (Bigtooth Maple) Communities and Potential Population Changes
AUTHORS:
Oscar W. Van Auken, Donna L. Taylor, Chen-chen Shen, Janis K. Bush
KEYWORDS:
Age structure, Community Structure, Dendrochronology, Diameter Structure, Population Dynamics, Weibull Analyses
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.8 No.6,
May
26,
2017
ABSTRACT: Isolated, relic populations of Acer grandidentatum (bigtooth maple, Sapindaceae) were found in deep canyons in central
Texas. Associated with them on hilltops were communities of Juniperus ashei (ash juniper). We determined the structure of relic A. grandidentatum populations and compared them to adjacent J. ashei populations. The overstory and understory density
was counted and basal area was determined for all woody species in both
communities using the quadrat procedure. Acer grandidentatum was the highest density (788 ± 964 or 52%) and basal area (29 ± 35 or
52%) overstory species in the canyon communities while J. ashei had the highest density (1589 ± 146 or 92%) and
basal area (51 ± 13 or 88%) in the hilltop communities. In the understory of
the canyon communities, there were five juvenile tree species including A. grandidentatum which had the fourth highest density (13% or 176 ± 110 plants/ha). In the
hilltop communities, J. ashei was the high density understory tree species (52%
or 994 ± 400 plants/ha). There were no A. Grandidentatum overstory or understory plants in the hilltop Juniperus communities. Acer grandidentatum had an inverse quadratic size distribution with few juveniles. Although
we counted a number of seedlings, there was little recruitment over the last 16
years and very little potential recruitment in the previous 20 years. Juniperus ashei had an inverse exponential size distribution with
many understory plants and considerable recruitment. Weibull age/size
distributions showed one A. grandidentatum established in the 1670’s and 2 in the 1760’s, with peak establishment in
the 1970’s. Causes of the lack of recent recruitment are uncertain, but it
could be episodic due to changes in herbivory, management or other
environmental conditions.