Rainfall interception and fog precipitation in a tropical montane cloud forest of Guatemala

Tropical montane cloud forest hydrology is complex because of the presence of epiphytic life-forms that increase canopy surfaces and fog persistency. Fog precipitation is a hydrological input common to cloud forests, and forms when fog droplets are intercepted by the canopy and fall to the forest floor. Interception and fog precipitation was determined for a 2100 m site and a 2550 m site in a first-order tributary of the Sierra de las Minas Biosphere Reserve, Guatemala by calculating the difference between throughfall and gross precipitation for a 44-week period. Both sites were situated within closed-canopy cloud forests. The 2100 m site was on the windward slope of Montaña de Miranda near the lower boundary of the cloud forest and the 2550 m site was at the summit. Fog precipitation was found during periods in which throughfall exceeds gross precipitation. Fog precipitation was greater at 2550 m than at 2100 m. Data collected by precipitation and throughfall gauges demonstrate the existence of seasonal fog precipitation with the greatest fog precipitation occurring in the dry season (November–April). Fog precipitation contributes approximately 1 mm per day to the hydrological budget of the cloud forest at 2550 m during the dry season, and 0.5 mm per day during the rainy season (May–October).     

Determinants of Agricultural Intensity Index “Scores” in a Frontier Region: An Analysis of Data from Northern Guatemala

Data on farming systems in Petén, Guatemala, were used to develop an agricultural intensity index. The index can be used to assign an intensity “score” to a given farming system based on the array of practices used by the farmer, each practice’s contribution to production intensity, and the scale at which these practices are used. The scores assigned to 118 farmers in three study areas in Petén were analyzed through analysis of variance (ANOVA) to identify the factors that account for the variation in intensity levels, as measured through the index. The analyses reveal that the factors influencing agricultural intensity in Petén vary greatly from one study area to the next. This is due to differences in livelihood opportunities and strategies that, in turn, affect how agriculture fits into the local economy and how and why intensification is pursued. Variation in intensity levels can best be understood by considering the factors at the household and sub-regional scales that influence (a) whether farmers feel a need to intensify, (b) whether they see some benefit in doing so, and (c) whether they have the resources required to intensify production through particular strategies. Close attention must be paid to these factors by conservation and development organizations seeking to influence land use patterns and conserve forest in Petén. Avrum J. Shriar is an Assistant Professor at Virginia Commonwealth University where he specializes in Environmental Geography, Rural Development and Land Use, Farming Systems, and Latin America and the Caribbean. He holds a BA in Geography from Bishop’s University in Lennoxville, Quebec, a Master of Environmental Studies (MES) from Dalhousie University in Halifax, Nova Scotia; and a PhD in Geography from the University of Florida in Gainesville. Some of his recent articles have appeared in Food Policy, Geoforum, Human Ecology, Agroforestry Systems, and the Delaware Review of Latin American Studies.     

Adoption potential of fruit-tree-based agroforestry on small farms in the subtropical highlands

Worldwide, fruit-tree-based agroforestry systems have been only modestly studied, although they are common on smallholder farms. Such systems based on apple (Malus spp.), peach (Prunus spp.), and pear (Pyrus spp.) are common in northwest Guatemala as low intensity homegardens and are known to increase total farm productivity in communities where farm size is a limiting factor. This study investigated the potential for adoption of fruit-tree-based agroforestry by resource-limited farmers using ethnographic investigation and linear programming simulations of farm activities at the household level. Two communities with differing demographics, infrastructure, and access to regional markets were selected based on the presence of extensive fruit-tree-based agroforestry. The influences of family size, land holdings, and tree and crop yields on the optimal adoption levels of fruit trees were evaluated through a comparative study of the varying social and physical infrastructure present in the two communities. Fruit-tree-based agroforestry was potentially more attractive to relatively prosperous families or those with larger land holdings. Improvements in fruit-tree productivity and interspecies competition were of greater importance where family land holdings were smaller. The inability of families to produce sufficient food to meet annual needs, poor fruit quality, and lack of market infrastructure were identified as constraints that limit adoption. The complementarity of production with the dominant maize (Zea mays) crop, home consumption of fruit, and the potential to generate additional cash on limited land holdings were identified as factors promoting adoption of fruit-tree-based agroforestry.     

Traditional knowledge and pest management in the Guatemalan highlands

Adoption of integrated pest management(IPM) practices in the Guatemalan highlands has beenlimited by the failure of researchers andextensionists to promote genuine farmer participationin their efforts. Some attempts have been made toredress this failure in the diffusion-adoptionprocess, but farmers are still largely excluded fromthe research process. Understanding farmers'agricultural knowledge must be an early step toward amore participatory research process. With this inmind, we conducted a semi-structured survey of 75Cakchiquel Maya farmers in Patzún, Guatemala, tobegin documenting their pest control practices. Theirresponses revealed that their understanding ofbiological and curative pest control is limited.However, their broad knowledge of cultural preventivepest control practices could explain why they hadfaced few pest problems in their traditionalmilpa (intercrop of corn, beans, and other edibleplants). The majority of these preventive practicesare probably efficient and environmentallyinnocuous.     

Predicting Maize Yield,Nutrient Concentration,and Uptake in Phosphorus- and Potassium-Fertilized Soils: Pressurized Hot Water and Other Alternatives to Mehlich I Extraction in Guatemala Soils

Abstract

Poor accessibility and cost of soil testing reduce effectiveness of fertilizer use on small‐scale subsistence farms, and inadequate funding promotes adoption of soil tests in developing countries with minimal validation. For example, Mehlich I extraction of phosphorus (P) currently used extensively in Guatemala may not be suitable for Guatemala's broad range of soils. At least four alternatives are available but relatively untested [Bray 1, Mehlich III, Olsen, and pressurized hot water (PHW)]. Pressurized hot water is relatively simple and inexpensive but is not yet tested against other extraction methods under variable P or potassium (K) fertilization levels. To determine whether PHW‐extracted nutrients could be used to predict maize yield and nutrient concentration and uptake, soil, plant tissue and grain samples were obtained from a multiple‐site field study, and calibration studies were conducted using five rates of P and three rates of K on soils incubated without plants or cropped with maize in greenhouse and field conditions. In the multiple‐site field study, maize yield related significantly to PHW‐extractable P (r²=0.36) and to leaf P concentration (r²=0.23), but Mehlich I–extractable P did not. In the two soils used in the greenhouse study, maize yield, vegetative P concentration, and total P uptake by maize were predicted by PHW‐extractable P (R²=0.72, 0.75, and 0.90, respectively). In the field experiment, grain yield was not improved by P or K application, but P concentration of maize leaf tissue did relate significantly with PHW‐extracted P (R²=0.40). Mehlich I did not. There were no yield responses to K application in any experiment, but relationships defined between extractable K for all five K‐extraction procedures and soil‐applied K were similarly significant. In comparison, PHW was as good as or better than Olsen whereas Bray 1 and Mehlich III were less consistent. Mehlich I was overall the poorest P extractant. Mehlich I extraction of P should be replaced by one of the four alternatives tested. PHW is the least expensive and, therefore, most viable for use in Guatemala soils.     

Evaluation of p as a limiting macronutrient in volcanic ash soils of guatemala

Abstract

P status of soils derived from volcanic ash in Guatemala was investigated. Growth chamber and greenhouse studies were conducted with H‐3 hybrid corn (Zea mays). All plants exhibited P deficiency symptoms and yielded less dry matter when they were grown on soils that received only lime at a rate equivalent to 2,240 and 4,480 kg/ha. The P content of plants was low and correlated with P deficiency symptoms. Application of P (336 and 672 kg/ha) under constant liming corrected the P deficiencies and increased dry matter. In comparative studies, plants grown on a highly fertile, non‐volcanic soil showed vigorous growth and yielded high dry matter. Apparently, P was limiting productivity in volcanic ash soils of Guatemala, and due to low exchangeable Al, addition of only lime did not produce beneficial results. The soils responded to P fertilization and they should be supplied large quantities of this macronutrient.     

Fallow management practices in Guatemala's Western Highlands: social drivers and biophysical impacts

Land pressures and environmental degradation are driving forces behind shortened fallow periods in the tropics, often resulting in reduced crop yields and increased migration from rural areas. This paper describes contemporary fallow practices in the Western Highlands of Guatemala based on interdisciplinary data collected using participatory rural appraisal and qualitative research methods in combination with a quantitative evaluation of the impacts of fallow management decisions on soil fertility. Case studies of two communities in San Marcos department illustrate contemporary and traditional land use practices. Currently, over 70 per cent of families engage in a variety of fallow management practices, with combined cropping‐fallow cycles within a field averaging 3–6 years. Despite the reduction in length of fallow cycles, new fallow practices in the study area appear to improve some aspects of soil fertility while also providing fodder and fuelwood. Calcium and magnesium concentrations in fallow soil were twice that of cropped plots, indicating that weathering reactions and atmospheric deposition during fallow periods are able to restore base cation fertility that is taken up by potato crops during cropping cycles. Soil in cropped plots, however, showed 25 per cent higher soil organic matter and five times higher nitrate concentrations than soil in fallow plots, which resulted from additions of compost and inorganic fertilizer to cropped plots. Nevertheless, the ¹³C/¹²C isotopic ratio of soil organic carbon indicated that as soil organic matter content decreases in cropped plots, the remaining carbon is increasingly degraded. Potential improvements in fallow management practices proposed by farmers and researchers are also presented. Copyright © 2007 John Wiley & Sons, Ltd.     

The compatibility of timber and non-timber forest product extraction and management

We discuss the extent of compatibility of timber and non-timber forest product (NTFP) extraction in two neotropical localities from biophysical, social, and institutional perspectives: the community concession forests of the Petén, Guatemala, and extractivist communities in northern Bolivia. In both localities, timber is harvested via reduced-impact logging (RIL) practices. In Guatemala, the main NTFP extracted is foliage from the understory xate palm (Chamaedorea spp.); in northern Bolivia, the fruits of the Brazil nut tree (Bertholletia excelsa). The Guatemalan case suggests a relatively high degree of compatibility due to low timber harvesting intensities, coupled with temporal, spatial, and social segregation of xate extraction in a well-defined land tenure system. In northern Bolivia, forest management regulations pay little attention to NTFPs and land tenure issues and related conflict complicate efforts to limit timber harvesting impacts on Brazil nut trees. The introduction of timber management plans overlain on customary property rights systems in which the extraction of Brazil nut is organized could undercut its management system. The two case studies suggest that specific legislative, education, and project interventions may help to promote the compatibility of timber and NTFP extraction and management. These include formal training of foresters on NTFP ecology and management while taking into account the perspectives of multiple stakeholders in the design of management plans. Tropical forest users, research managers, and policy makers will also better understand the need for integrated management of timber and NTFPs, if the trade-offs and potential economic benefits from NTFP extraction are clarified.     

Nitrogen-Fixing Trees in Small-Scale Agriculture of Mountainous Southeast Guatemala

Abstract

Intensive, subsistence agriculture on hillsides of southeast Guatemala has caused extensive soil degradation. This retrospective study evaluated the success of an agroforestry treatment in improving the sustainability of mountainous agricultural systems in terms of soil nutrient status and erosion control. Three years after maize (Zea mays) and pasture fields were alley-cropped with N-fixing Gliricidia sepium trees, soil nutrient levels were examined and compared to nonalley-cropped controls. Agroforestry treatment showed significantly higher soil organic matter (SOM) over paired plots with no alley-cropping (mean 4.3% vs. 3.2% C, p < 0.05). Mean total N was also higher, with 0.12% in the nonagro-forestry control plots compared to 0.16% underthe agroforestry treatment (p <0.05). Some improvement in soil water-holding capacity(WHC) was also observed in the agroforestry systems. Differences in soil levels of available P, ranging from 8.0 to 64.4 μg/g, were not significant and correlated more with site than with agroforestry treatment versus control. Specific soil and site properties such as texture and slope as well as land use and ground cover management largely influenced improvements in soil nutrient status under the agroforestry treatment at each site. Despite increases in soil nutrients, maize plant productivity showed no response to the agroforestry treatment in terms of leaf chlorophyll index or maize plant height. Three years after the initiation of agroforestry, soil erosion rates showed no difference from paired controls; rates were correlated with ground cover and soil characteristics such as texture and surface rockiness rather than with agroforestry treatment. While soil nutrient status had not reached levels optimum for maize growth after three years, the positive trajectory of change in soil nutrients suggests the potential for using agroforestry systems in mountainous regions of Guatemala to increase the sustainability of agricultural production.