Sustainable leaf harvesting and effects of plant density on wild leek cultivation plots and natural stands in Southern Quebec, Canada

摘要

Overharvesting reduces the populations of wild leek in deciduous temperate forests of North America. Forest farming relying on planted bulbs that are fertilized and selectively harvested could enhance and sustain wild leek production. Density reduction following bulb harvest could improve yield in natural wild leek stands that reach growth-limiting densities. Limiting the harvest to leaves may also provide an alternative form of exploitation, but could slow growth by reducing both carbon and nutrient reserves depending on the timing and intensity of such harvest. Our objectives were to assess the effects of (1) planting density and post-harvest density reduction, and (2) the timing and intensity of leaf harvest on subsequent growth and reproduction of wild leek. Three experiments were established. Bulbs were planted at densities from 44 to 356 bulbs m(-2), covering the range surveyed in natural populations. Plots in dense populations were subjected to up to 40 % bulb harvest. In cultivated plots, either half or all the leaves on each plant were harvested, from 15 to 25 days after unfolding. Plants growing in higher density plots exhibited slower growth and reproduction rates, but greater productivity per cultivated area. A similar effect, albeit marginal, was obtained following bulb harvests in natural populations. Harvesting leaves did not affect survival, but delaying the harvest and harvesting only half of the leaves favored subsequent plant growth. We recommend harvesting down to a fixed bulb density rather than harvesting a percentage of bulbs, and harvesting leaves only as ways to ensure sustainable exploitation of leeks.