Ecosystem health and sustainability of an indigenous agroforestry system in Chiapas, Mexico

1
Ecosystem health and sustainability of an
indigenous agroforestry system in Chiapas, Mexico
Stewart A.W. Diemont and Jay F. Martin
Ecological Engineering Group Department of Food,
Agricultural, and Biological Engineering The
Ohio State University
Abstract The Lacandon Maya of Chiapas, Mexico
practice a system of agroforestry that mimics the
surrounding ecosystem and its successional
stages. Their fields rotate through grass
(milpa), and shrub (acahual) and forest fallow
sages 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. Emergy, plant community, nematode
and soil chemistry analyses were used to evaluate
the system. Emergy calculations resulted in high
emergy sustainability indices (ESI) ranging from
31 to 4356. ESI was found to be a function of
fallow area and did not relate to management
practice. In contrast, nematodes were found to be
a function of management practice. In milpas
where weeds were removed and applied to the
field, plant parasites were reduced by 44 and
fungivorous nematode concentrations were cut in
half. In these same fields, bacterivorous
nematodes were found to be a function of soil
organic matter (Plt 0.05). These results indicate
that Lacandon management practices delayed the
nematode successional processes. Lacandon Maya
land management, although limited by land
pressures, offers insights into pest reduction
and fertility maintenance in agroecosystems.

Methods Sampling was conducted during July and
August 2003 in six Lacandon Maya agroforestry
systems in Lacanja Chansayab, Mexico. Soil and
plant community sampling was performed in each
successional stage from each system in three
traditional Lacandon systems and three
non-traditional systems. In addition to the three
field stages, milpa, acahual, and secondary
forest, one primary forest was also sampled.
Only one non-traditional acahual was
sampled. Sampling locations were determined in
each field stage using a transect method. Soil
samples were collected within a circular 1-m2
quadrat at each sampling location. Soil samples
were partitioned for organic matter, inorganic
nitrogen, total nitrogen and nematode analysis.
Using the Baermann wet funnel technique,
nematodes were extracted into water from 20-g
soil samples for 72 hours. The nematodes were
then identified to trophic level using a 45x
stereoscopic dissecting microscope. Plant cover
assessment was conducted at each sampling
location. In the milpa, all plants in the quadrat
were recorded based on percent cover. In the
acahuals, secondary and primary forests, plants
with a stem or trunk diameter greater than 1-cm
were counted in the quadrat, and all plants with
a diameter greater than 5-cm were counted within
a 20 m2 circular area. Interviews for emergy
evaluations were conducted during July and August
2003 with six Lacandon Maya farmers in Lacanja
Chansayab, Mexico. The six farmers included three
who fallow traditional methods (Manuel
Castellanos, Kin Bor, and Jorge Paneagua) and
three non-traditional (Vicente Paneagua, Enrique
Paneagua, and Kin Paneagua). The ratio of
cultivated area to total land area spanned a
broad range across the six systems.

Figure 4. Nematode fungivore concentration as a
function of nematode plant parasite concentration.
Results 1. The agroforestry system is highly
sustainable. The emergy sustainability index
(ESI) was greater than 30 (Table 1). These
results are due to a large proportion of
renewable resources utilized. ESI was not
dependent upon adherence to traditional practice,
but was proportional (on a log-log scale) to the
land area occupied by the system (or the amount
of area in fallow) (Figure 3). 2. Nematode
population, soil chemistry, and plant community
was dependent upon successional stage and
adherence to traditional practice. a. Plant
parasite nematode concentrations were
proportional to fungivorous nematode
concentrations (Figure 4). b. Plant parasite
concentrations were greater in non-traditional
than traditional systems. Weedy species were
greater in non-traditional systems. c. Weedy
species management affected both plant parasites
and the successional conversion of the
degradation pathway of a field from bacterivorous
to fungivorous (Figure 5). d. Soil organic
matter and total nitrogen increased with
successional stage and also differed between
traditional and non-traditional systems.

Figure 1. Lacanja Chansayab is the home to 400
Lacandon Maya who practice swidden agroforestry

• Introduction
• The Lacandon rainforest of Chiapas, Mexico is
  losing 7 of the remaining forest each year.
  Erosion has moderately degraded 10 to 25 of the
  arable soil and severely degraded 5 of the
  arable soil in the coffee-producing lowlands of
  Chiapas (Howard and Homer-Dixon 1996). These
  problems are endemic throughout the tropics, as
  increasing population densities stress the
  environment through demands on agricultural land
  (Lal 1995, Alvarez and Naughton-Treves 2003).
  These demands result in diminished fallow time,
  which leads to deforestation and soil erosion
  (Drechsel et al. 2001).
• Numerous researchers recognize the importance of
  recording indigenous knowledge to better
  understand sustainable methods of land management
  (De Clerk and Negreros-Castillo 2000, Fox et al.
  2000, Long and Zhou 2001, Hardwick et. al. 2004).
  Swidden agroforestry systems can be productive
  (Long and Nair 1999) while maintaining ecological
  integrity (Zhijun and Young 2003). The indigenous
  knowledge in southern Mexico is quickly
  disappearing as younger members of the community
  seek work in urban centers and in ecotourism
  (Trujillo 1998, McGee 2002, Gillespie et al.
  2004). This makes it vital to understand how
  indigenous knowledge is used to design
  agroforestry systems.
• The Lacandon Maya are an indigenous group living
  in Lacanja Chansayab, Mexico (Figure 1) who have
  supported themselves for centuries through
  effective use of their surrounding environment.
  They practice a unique method of swidden
  agroforestry in which they manage the fallow
  period for production and soil regeneration
  (Nations and Nigh 1980, Levy 2000, McGee 2002).
  Their system cycles through three field stages of
  production starting with the milpa, progressing
  to the acahual, and then to the secondary forest,
  before returning to the milpa (Figure 2).
  Components of their agroforestry could serve as a
  model to farmers in Chiapas and in similar
  ecological regions throughout the tropics.
• In order to better understand the Lacandon
  agroforestry system, research was conducted
  during 2003 that evaluated
• Emergy
• Plant community
• Soil chemistry
• Soil nematodes
• It was hypothesized that traditional management
  of Lacandon systems would impact the system
  differently than systems where traditional
  management was no longer being practiced.

Figure 2. Systems diagram of Lacandon Maya
swidden agroforestry system
Figure 5. Nematode concentration as affected by
weed management in traditional Lacandon
agroecosystems
Conclusions The Lacandon agroforestry swidden
system offers insight into how sustainable land
management can be conducted in tropical regions.
Emergy analysis determined that the system is
highly sustainable, although the sustainability
is dependent upon land area devoted to the
system. System management that adheres to
traditional practices results in fewer live
weeds, reduced plant parasite pests, and a slower
conversion of the degradation pathways in the
field from bacterivorous to fungivorous. These
results indicate that pests can be reduced and
fertility maintained if the traditional
management is utilized and adequate land is
available for the swidden system.
R2 0.90 y 1.4x 1.1 P 0.005
Table 1. Emergy indices of the Lacandon
agroforestry systems.
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Figure 3. Log of the Emergy Sustainability Index
(ESI) as a function of Log of the land area
devoted to Lacandon agroforestry system