Population Viability Analysis of American Ginseng and Wild Leek Harvested in Stochastic Environments

摘要: Many populations of threatened American ginseng (Panax quinquefolium) and vulnerable wild leek (Allium tricoccum) have declined gone extinct because overharvesting in Canada. We assessed the impact harvesting on these species stochastically varying environments estimated their extinction thresholds minimum viable populations. With both we used four transition ma- trices taken from literature stochastic population projections under various regimes. For gingseng mean growth rate (A) with increasing (h) accord- ing to number years between harvests (tr), as -0.54 h tr0-( 909. When plants more than two leaves are harvested every 5 years, a harvest approximately 30% was sufficient bring A below equi- librium value 1.0. Extinction thresholds, needed rebuild population, varied 30 90 plants, size at 170 plants. Only dozen known Canada exceed so most could not support any harvest- without serious threats long-term persistence. leek, strategies were identi- fied confiscated, illegal Gatineau Park (Quebec): (1) "cboosy" harvesters collect fewer but larger bulbs, (2) "busy" numerous smaller bulbs. These data allowed simulations more-realistic strategies. The decline along gradient faster for At rates I 8% proba- bility that falls equilibrium less 5%. threshold esti- mated 140-480 300-1030 according