Demography and potential extractive use of the liana palm Desmoncus orthacanthos Martius (Arecaceae) in southern Quintana Roo Mexico
Escalante S; Montana C; Orellana R
Forest Ecology and Management
In order to evaluate the extractive use potential of Desmoncus orthacanthos various matrix models were employed to assess population structure and dynamics. To this end populations of this liana palm were investigated in southern Quintana Roo Mexico at two localities showing contrasting fragmentation levels arising from different land use regimes. In one case continuous forest (CF) are maintained under forestry management while in the other (fragmented forest FF) isolated forest patches remain inside of a matrix of crop and livestock lands. Three forest conditions: mature forest (MF) young forest (YF) and forest edge (FE) were nested in each fragmentation level. Results showed that more plants were encountered under FF situations than under CF conditions; however no differences were noted in exploitable shoots (i.e. total numbers and lengths) when both were compared. Under forest conditions number and length of exploitable shoots did not differ between FE and MF populations however these values were smallest in YF populations. Intrinsic population growth rates ([lambda]) were lower under FF than under CF as reflected by periodic matrix values of 0.964 and 1.594 respectively. With respect to forest conditions [lambda] for FE>[lambda] for YF>[lambda] for MF and periodic matrix values were 1.441 1.193 and 1.075 respectively. Elasticity analyses for annual matrices showed that the demographic process having most influence on variations in [lambda] was (periodic matrix values) permanence (43-63%) followed by growth and retrogression (15-22% and 14-23% respectively); fecundity had the lowest influence in changes of [lambda]-values (8-13%). Analyses of the simulated extraction of shoots >=5 m suggested that FE and CF populations might support harvest rates of 40% per year since [lambda]>1; however simulation of harvest rates as low as 20% in other populations always resulted in [lambda][lambda] especially for FE populations; simulations combining shoot extraction with the addition of juveniles suggested that high levels of harvest may be possible even while maintaining [lambda]>1; but only if sound forest management is practiced and agricultural fires are restricted. This work showed the value of matrix models for analyzing populations dynamics in establishing sustainable use strategies for D. orthacanthos as opposed to static evaluation of population numbers.