J. D. H. Lambert

Caracol, Belize: Evidence of Ancient Maya Agricultural Terraces

AbstractRecent studies of ancient Maya settlement and demography indicate population densities exceeding those achievable using traditional swidden farming techniques, and suggest that more intensive farming methodologies such as terracing were employed. This paper describes recent archaeological investigations at the major Maya ceremonial center of Caracol, Cayo District, Belize, a poorly known region of the southern Maya lowlands. Research concentrated upon a six-hectare zone of terraced hillslope and included detailed mapping and excavations. An examination of the terraces and associated residential units is made, with discussion of the antiquity of these structures, their distribution, terrace size, form, and probable function. The first radiocarbon dates for Caracol, as well as data on terrace soils and pollen, are presented.

Allelopathic properties of α-terthienyl and phenylheptatriyne, naturally occurring compounds from species of asteraceae

Alpha-terthienyl (α-T), a naturally occurring polyacetylene derivative from roots ofTagetes erecta L., and phenylheptatriyne (PHT), from leaves ofBidens pilosa L., were tested as possible allelopathic agents against four seedling species (Asclepias syriaca L.,Chenopodium album L.,Phleum pratense L.,Trifolium pratense L.).Asclepias was the most sensitive of the species. Allelopathic activity was enhanced in the presence of sunlight or sources of near-UV, with LC50s forA. syriaca of 0.15 ppm and 0.66 ppm with α-T and PHT, respectively; 0.27 and 0.85 forC. album; 0.79 and 1.43 forP. pratense, and 1.93 and 1.82 forT. pratense. Near-UV exposure was saturating but never more than found in summer sunlight at Ottawa, Canada. Growth inhibition was observed with seedlings treated with α-T and PHT but without near-UV irradiation. Germination of seedlings was also sensitive to α-T and PHT with or without near-UV treatment. α-T was extracted from soil surrounding the roots ofTagetes. Concentrations calculated for the soil (0.4 ppm) indicate that seedling growth could be significantly hindered. The activity and specificity of α-T was sufficiently high to warrant future field trials to assess its potential as a natural weed-control agent.

Maya medicinal plants of San Jose Succotz, Belize.

The traditional use of plants for medicine was studied in the Maya village of San José Succotz, Belize. Sixty-four species were collected and 106 remedies are described. The ethnobotany of Succotz is discussed in relation to traditional concepts of medicine, ritual and magic in treatment of illnesses, and biochemically active constituents of the plants. Use of plants in Belize and the Yucatan is compared.

LEAF-LITTER AND CHANGING NUTRIENT LEVELS IN A SEASONALLY DRY TROPICAL HARDWOOD FOREST, BELIZE, C.A.

SummaryTotal above ground plant biomass in a 45 year old seasonally dry tropical hardwood forest was estimated to be approximately 56,000 kg/ha oven dry weight. Nutrients immobilized in the standing vegetation were: N, 203 kg/ha; P, 24 kg/ha; K, 234 kg/ha; Ca, 195 kg/ha; Mg, 47 kg/ha; Na, 9 kg/ha; Mn, 1 kg/ha; Cu, 0.5 kg/ha; Zn, 3 kg/ha; Fe, 4 kg/ha. Total nutrients returned each year through the litter were: N, 156 kg/ha; P, 9 kg/ha; K, 59 kg/ha; Ca, 373 kg/ha; Mg, 32 kg/ha; Na, 5 kg/ha; Mn, 1 kg/ha; Al, 21 kg/ha; Zn, 0.3 kg/ha; Fe, 9 kg/ha. Half of the nutrients immobilized in the standing vegetation were found in the leaves and are returned annually to the soil. Although litter fall is interrupted during the year, the mean nutrient content of the litter was high −5.2%.A decomposition rate of 0.48 percent per day was considered high for a seasonally dry tropical hardwood forest. Fluctuations in soil nutrient levels showed a sharp increase at the start of the rainy season. Later during the dry season nutrient levels decreased to concentrations similar to what they were just prior to the rainy season. Soil organic matter levels were very high −20% in the top 12 cm.

Nutrient dynamics in milpa agriculture and the role of weeds in initial stages of secondary succession in Belize, C.A.

Nutrient levels, soil moisture and soil organic matter were monitored monthly during a three year period in a site cleared for shifting agriculture (milpa) and in adjacement undisturbed high bush forest soils in Belize. Throughout the study there was no evidence of a decline in available nutrient levels in the cleared site. Sharp changes in P and Mn were considered indicative of wetting and drying periods.Corn yields for the rainy season crop in the first two years were average for the region ca 2500 kg ha−1 dry wt, but declined dramatically in the third year. Total weed biomass for the rainy season crop conversely increased every year and reduced grain yield probably through competition for nutrients (especially N), light and water. Substantial amounts of nutrients were also immobilized in the weed biomass, which served the agroecological purpose of preventing nutrient loss by leaching.

Decline of soil fertility due to intensification of land use by shifting agriculturists in Belize, Central America

Abstract Intensification of land use by shifting Maya agriculturists in Belize, Central America, has led to a decline in soil fertility and crop yields. Examination of eleven nutrients in crop plants and soil, and changes in nutrient levels with the length of the cropping period, indicated that phosphorus was the limiting factor for plant growth. Physical analyses of the soil and visual evidence suggested that erosion is a contributing factor to declining soil quality. A variety of solutions to the infertility problem are discussed.

Woody species and nutrient accumulation during the fallow period of milpa farming in Belize, C.A.

Plant lifeform composition and levels of nutrients accumulated by fallows aged 1, 2 and 3 years under shifting (milpa) cultivation in Belize were measured. Levels of N, P and K allocated to leaves rapidly reached a plateau in 1 year old fallows with little increase in 2 and 3 year old sites. In stem material, K was accumulated rapidly, with little increase after the first year of fallow growth, while N and P accumulation proceeded at steady rates during three years of fallow development. Total biomass in 3 year old fallows averaged 2070 g m−2 with 10.3 g m−2 N, 0.73 g m−2P and 13.2 g m−2K. Nutrient concentrations in early successional species were higher than in species of later successional status, suggesting different strategies for nutrient utilization.Woody lifeforms dominated the fallow vegetation, accounting for 80% of total biomass in first year fallows and eliminating herbaceous species after 2 and 3 years of fallow growth. The importance of rapid recovery of woody species is discussed as it relates to fallow management and weed control.

Mineral cycling in a tropical palm forest

Nutrient cycling and biomass characteristics of a tropical palm forest dominated byOrbignya cohune were found to be different from thsoe of hardwood dominated forests. The cohune palm forest had a high proportion of biomass in leaves (5%), a reduced sapling layer, a large amount of standing forest litter and an exceptionally low decomposition rate factor (0.1 year−1). Mineral concentrations in palm leaves were generally lower than in hardwood species with the exception of Na, which was exceptionally high inOrbignya cohune. Biomass was estimated at 226 tons ha−1 containing 1173 kg ha−1 N; 126 kg ha−1 P; 437 kg ha−1 K; 1869 kg ha−1 Mg; 125 kg ha−1 Ca, and 2177 kg ha−1 Na. Soils of cohune association did not differ significantly from those of neighbouring hardwood dominated associations with the exception of Na which occurred in higher concentration because of bioaccumulation in the dominant. The results suggest that the growth habits and physiology of a dominant can strongly influence some of the ecological parameters used to describe aforest association.

Nitrogen cycling in the seasonally dry forest zone of Belize, Central America

Two forest associations, cohune palm (Cohune Ridge) and mixed tropical hardwood (High Bush), were assessed on the basis of nutrient movement and storage for their suitability for agriculture. Continuous monitoring of soil nitrogen and leaf litterfall over a one-year period provided information on soil building processes in the forest fallow. Destructive cuts revealed the storage of 690 kg N ha-1 in the standing biomass of the Cohune forest versus 203 kg N ha-1 in the High Bush. Litter biomass was exceptionally high in the Cohune Ridge (497 kg ha-1 dry matter) as compared to the High Bush (65 kg ha-1 dry matter) and other tropical forests. This is probably because of a low rate of decomposition in the Cohune Ridge palm forest. A substantial reserve of nitrogen is present in both forests’ fallows, and this can in part be harvested by the small farmer for crop production.

Nutrient levels in corn and competing weed species in a first year milpa, Indian church, Belize, C.A.

SummaryGrain production in two 1/4 hectare plots gave 2971 and 1380 kg/ha for an average yield of 2175 kg/ha. Average yield for local farmers was 1700 kg/ha. Weed biomass accounted for 50% of total bioomass in the hydric Site 4, but held 64–83% of the total nutrients. In the mesic Site 1, values were 5% and 3–29% respectively.Canna edulis was the most abundant weed species. Soil nutrient levels neither increased or decreased significantly between clearing and harvesting. Any decline in future crop production would be due to increased weed competition and not a decline in soil fertility. Weevil (Sitophilus zeamais) infestation is a serious problem in hybrid corn not encountered with local varieties.