The Lacandon Maya of Chiapas, southern Mexico, have traditionally used a long fallow rotational slash-and-burn system for maize production in small clearings within tropical forest. Although successional processes usually lead to rapid restoration of abandoned fields, the invasive fern, Pteridium aquilinium (commonly known as Bracken), can block natural succession. The Lacandon are aware of this and use the fast-growing tree Balsa (Ochroma pyramidale) to accelerate succession toward mature forest. We carried out a 12-month-long experiment in a Brackeninfested area to test the effectiveness of the Lacandon's low-input restoration techniques. We found that we could successfully establish Balsa in plots dominated by Bracken using the Lacandon methodology. Their technique involves broadcasting large numbers of small seeds and applying traditional weeding techniques. After 12 months' growth, Balsa reached a top height of over 6 m and basal areas of 4.1 (±0.3) m 2 /ha. We contrasted this low-cost traditional fallow management with more costly techniques involving transplanting Balsa seedlings and sowing directly in the experimental area. The results validated the effectiveness of the Lacandon method for directing succession and confirmed the general potential of Balsa as a facilitator in the restoration of degraded tropical forest areas.

No abstract

No abstract

The Lacandon Maya of Chiapas, Mexico practice a system of swidden agroforestry that mimics the surrounding ecosystem and its successional stages. Their fields rotate through grass (milpa), and shrub (acahual) and forest fallow stages that regenerate soil, nutrients, and seed banks. Each successional stage, including the fallow stages, produces over 25 types of crops, raw materials, and medicines. Lacandon traditionally do not use fertilizers, pesticides or herbicides. An emergy evaluation of Lacandon agroforestry was conducted to quantify resource use, productivity, environmental impact, and overall sustainability. Six systems were analyzed. The Emergy Yield Ratios of the systems ranged from 4.5 to 50.7, which indicated a high level of output per purchased investments. The agroforestry systems had minimal environmental impacts as shown by Environmental Loading Ratios between 0.03 and 0.38. The Emergy Sustainability Index (ESI) of the systems ranged from 12 to 1740, indicating a high level of sustainability. The high ESI values were partially due to a large fraction of renewable resources that varied from 0.72 to 0.97. ESI was dependent upon land area devoted to the system for each family, where greater land area resulted in higher values of ESI. Labor invested did not exhibit a direct effect on sustainability.

Summary1. Large areas of agricultural land around the world are degraded as a consequence of dominance by bracken fern (Pteridium spp.). Tropical production systems based on shifting cultivation and cattle breeding are particularly vulnerable to invasion of this species. In spite of this, effective methods for tropical bracken control are limited. 2. Fast-growing tree species have been used successfully to out-compete aggressively colonizing heliophytes and trigger natural succession. Drawing on a traditional Mayan management technique, we evaluate the potential of the pioneer tree balsa (Ochroma pyramidale) to control Pteridium caudatum in Chiapas, Mexico. We tested different bracken cutting frequencies and balsa propagation methods in a factorial randomized block experiment. Eighteen months later, we quantified bracken biomass under the young balsa canopy. 3. Living bracken rhizome biomass correlated significantly with balsa basal area, leaf litter biomass and understorey light intensity. While bracken rhizomes persisted in control plots, it was completely eradicated in plots with a minimum balsa basal area of 11 m 2 ha À1 . This threshold value was reached in less than 18 months with any of the tested propagation methods (seed broadcasting, direct sowing or nursery seedlings), on the condition of at least monthly bracken cutting during the first six months. 4. The ability of fast-growing broad-leaved pioneer trees like balsa to quickly out-compete bracken fern offers opportunities for large-scale application in tropical rural areas where economic and technical resources are scarce. 5. Synthesis and applications. Mayan subsistence farmers traditionally use balsa to outcompete invasive weeds, including bracken fern. Here, we highlight the usefulness of this method for quick and effective bracken control in southern Mexico. This approach, in combination with balsa's short rotation cycle, creates opportunities to rapidly convert bracken land into forest stands with commercial potential, thus providing local income and increasing the likelihood of adoption by rural people. We encourage further research to test the potential of balsa and other fast-growing pioneer trees species for controlling bracken and similar weeds.