Multi-purpose species in the Kuxur Rum agroforestry system on the dry corridor area, Guatemala

Introduction

The geographic area of the dry corridor in Guatemala is highly affected by weather extremes with unpredictable changes in terms of rainfall and temperature (Quesada-Hernández et al., 2019Quesada-Hernández, L. E., Calvo-Solano, O. D., Hidalgo, H. G., Pérez-Briceño, P. M., & Alfaro, E. J. (2019). Dynamical delimitation of the Central American Dry Corridor (CADC) using drought indices and aridity values. Progress in Physical Geography: Earth and Environment, 43(5), 627-642. https://doi.org/10.1177/0309133319860224). Drought periods during summer started to become longer, reducing the crop season (Petrone & Preti, 2010Petrone, A., & Preti, F. (2010). Soil bioengineering for risk mitigation and environmental restoration in a humid tropical area. Hydrology and Earth System Sciences, 14(2), 239-250. https://doi.org/10.5194/hess-14-239-2010). Farmers are now cropping species and cultivars with shorter cycles of growth and, consequently, less yielding.

The negative effects due to unpredictable weather are faced with the “Kuxur Rum” agroforestry system, a word than in the local language Ch'Ortí’ means “My wet soil”, and suggests the convenience of maintaining humidity inside the soil for a long time. Even when this is not covered by plants, and enables continuing incorporation of organic matter into the upper layers of soil. Some research has proven also the positive effect of the Kuxur Rum agroforestry system into the fight to soil erosion (Posada Quinteros, 2012Posada Quinteros, K. E. (2012). Impacto del Sistema Agroforestal Kuxur Rum en la sostenibilidad de los medios de vida de las familias rurales en Camotán y Jocotán, Guatemala [Magister Scientiae en Socioeconomía Ambiental, CENTRO AGRONÓMICO TROPICAL DE INVESTIGACIÓN Y ENSEÑANZA]. https://agritrop.cirad.fr/575304/1/document_575304.pdf).

The Kuxur Rum agroforestry system is based on the planting of Madrecacao trees (Gliricidia sepium (Jacq.) Walp.) in rows intercropped with grains like Phaseolus vulgaris L. and Zea mays (L.). Every year, before the sowing of the crops, the Madrecacao trees are strongly pruned or even coppiced, leaving the residues grounded as mulching above the soil. The use of Gliricidia sepium is because as a leguminous species native from Central America has a high level of adaptability to the environment, and thanks to this, it is commonly used by farmers as a living fence, or as fodder for livestock (mostly leaves).

Although research has been done on the effects of the Kuxur Rum agroforestry system on intercrop productivity and soil fertility (Villafuerte Lemus & Morales Calderón, 2019Villafuerte Lemus, H. A., & Morales Calderón, B. J. (2019). Validación de la forma de aplicación de la materia verde en el sistema agroforestal Kuxur rum, para la producción de frijol negro, en el corredor seco de Chiquimula. Guatemala 2018 (p. 28). https://cria.iica.int/system/files/files/2024-03/Informe%20Final%20Validacio%CC%81n%20Kuxur%20Rum%20CUNORI.pdf), not much is known about its effects on the biodiversity of plant species. Experience has shown that even increasing crop productivity as much as possible with the Kuxur Rum, this is not enough to improve farmer’s wealth, and at the same time, many of the species present on the KR have also unknown medicinal properties that can be useful to next generations.

The objective of this research was to measure and quantify the plant biodiversity in the Kuxur Rum agroforestry system, compared to the most popular crop in Guatemala (Milpas, cornfields based on rotations).

Materials and methods

The research has been done in the dry corridor area, in September - December 2019, and has investigated the biodiversity present inside the Kuxur Rum system and compared with the plant species present on the Milpas (cornfields), moreover, we asked about the traditional uses of the plants known by the farmers and in the literature reviewed.

We compared two different kinds of treatments: 9 Kuxur + 9 Milpas. All plots shared similar ecological conditions, climate, altitude, slope, aspect, kind of soil and cropping history. The cornfields analyzed were selected near the areas with the KR agroforestry system. The botanical composition of every plot was investigated by linear analysis, 100 m long and with identification points at 50 cm of distance.

The plant uses referred by local farmers were investigated by semi-structured interviews, moreover, moreover farmers were asked about the productivity and management of the agroforestry system. All plant species were identified at the Cunori facilities, with Latin scientific name according to the “The plan list Index”, a working list of all known vascular plant species.

To know the use of medicinal plant species and plant parts, open interviews were done to farmers and local people. Afterward, two rural communities of the Dry corridor area (“Dos quebradas” and “Lantinquin” villages, both in the municipality of Camotan) were visited with the technicians of the NGO “Santiago de Jocotan”, (partner of Mani tese, Italia). Many interviews about medicinal uses of plants were done to women from the rural communities, during the interviews, plant samples or photographs were shown for identification (Thomas et al., 2007Thomas, E., Vandebroek, I., & Van Damme, P. (2007). What works in the field? A comparison of different interviewing methods in ethnobotany with special reference to the use of photographs. Economic Botany, 61(4), 376-384. https://doi.org/10.1663/0013-0001(2007)61[376:WWITFA]2.0.CO;2).

This research has been possible thanks to the collaboration of the University of Florence (Italy), Cunori of the San Carlos University (Guatemala), the NGO “Mani Tese” (Italy) and their partner in Guatemala, the NGO “Santiago de Jocotan”.

Results and discussion

The total number of plant species (Table 1) has been higher inside the KR (55) than on the cornfields (42), probably, because most of the identified species are small weeds and, on the agroforestry, system have the advantage of less competition than in the traditional management of the land.

Moreover, the average number of species per plot (Figure 1) has been higher in Kuxur Rum (18.3) than outside (10.0). This suggests than the reduced presence of tree species (like Mangifera indica or Gliricidia sepium) or tree-like plants (ex: Carica papaya or Musa x paradisiaca bananas) favours the fertility of the soil and reduces the need of chemical weeding, thus permitting the existence of small native plants. Even if many of these trees or tree-like species were found on both different land treatments, they are present in different proportions and sizes.

Conclusions

The findings of this study show than the Kuxur Rum agroforestry system has increased the tree canopy cover, sparse enough to allow the growth of an herbal under layer. Although the lower spontaneous plants are popularly considered weeds, most of them have interesting uses on traditional medicine, partially or still not yet investigated by science.

The common cornfields (Milpas), with frequent ecological control of these weeds (mostly with chemicals, but also with manual control) keeps their presence controlled, and on the other hand, permits their subsistence.

In turn, the controlled conditions of the Kuxur Rum provide a better environment for the survival of small-sized herbs, which most of them produce useful secondary metabolites. We conclude that the Kuxur Rum agroforestry system provides not only a useful crop differentiation and better soil conservation but also better conditions for the conservation of the biodiversity in terms of plant species than in the traditional Milpas, thus the agroforestry system should be considered also useful on the conservation of traditional knowledge of plant uses.