Towards an ecological index for tropical soil quality based on soil macrofauna

The objective of this work was to construct a simple index based on the presence/absence of different groups of soil macrofauna to determine the ecological quality of soils. The index was tested with data from 20 sites in South and Central Tabasco, Mexico, and a positive relation between the model and the field observations was detected. The index showed that diverse agroforestry systems had the highest soil quality index (1.00), and monocrops without trees, such as pineapple, showed the lowest soil quality index (0.08). Further research is required to improve this model for natural systems that have very low earthworm biomass

Species, functional groups, and habitat preferences of birds in five agroforestry classes in Tabasco, Mexico

We studied species, functional groups, and habitat preferences of birds in five classes of agroforestry systems: agroforests, animal agroforestry, linear agroforestry, sequential agroforestry, and crops under tree cover in Tabasco, Mexico. Sampling sites were >2 km from natural forest fragments. Observations were made at 38 sites using 30-min point and transect counts in the morning and afternoon in the rainy season, season of northern winds, and dry season from June 2008 to May 2009. We observed 3,551 birds, which were assigned to 102 species: 72 were resident and 30 were migratory species. Overall efficiency of sampling was 82.4% and varied from 68.7% in linear agroforestry to 81.5% in animal agroforestry. Total species richness varied from 43 in sequential agroforestry to 64 in animal agroforestry. Species richness and Shannon diversity indices revealed no differences among agroforestry classes. Bird communities in animal agroforestry, linear agroforestry, and sequential agroforestry had similar species compositions, as did agroforests and crops under tree cover. Birds in all agroforestry classes were mainly forest generalists, although specialists of open areas were common, particularly in animal and sequential agroforestry. Only one individual of a forest specialist species was observed during sampling. Migrant species were mostly forest generalists, but some open area specialists occurred in animal agroforestry. Resident birds were distributed over all foraging guilds in all agroforestry classes, whereas migrants were mainly foliage-gleaning insectivores. Foraging guilds had different relative abundances among agroforestry classes. Structural diversity of agroforestry classes did not seem to influence bird species richness. Forest specialist species were virtually absent in agroforestry classes, but the avifauna in agroforestry is diverse and valuable in itsel

Species, functional groups, and habitat preferences of birds in five agroforestry classes in Tabasco, Mexico

We studied species, functional groups, and habitat preferences of birds in five classes of agroforestry systems: agroforests, animal agroforestry, linear agroforestry, sequential agroforestry, and crops under tree cover in Tabasco, Mexico. Sampling sites were >2 km from natural forest fragments. Observations were made at 38 sites using 30-min point and transect counts in the morning and afternoon in the rainy season, season of northern winds, and dry season from June 2008 to May 2009. We observed 3,551 birds, which were assigned to 102 species: 72 were resident and 30 were migratory species. Overall efficiency of sampling was 82.4% and varied from 68.7% in linear agroforestry to 81.5% in animal agroforestry. Total species richness varied from 43 in sequential agroforestry to 64 in animal agroforestry. Species richness and Shannon diversity indices revealed no differences among agroforestry classes. Bird communities in animal agroforestry, linear agroforestry, and sequential agroforestry had similar species compositions, as did agroforests and crops under tree cover. Birds in all agroforestry classes were mainly forest generalists, although specialists of open areas were common, particularly in animal and sequential agroforestry. Only one individual of a forest specialist species was observed during sampling. Migrant species were mostly forest generalists, but some open area specialists occurred in animal agroforestry. Resident birds were distributed over all foraging guilds in all agroforestry classes, whereas migrants were mainly foliage-gleaning insectivores. Foraging guilds had different relative abundances among agroforestry classes. Structural diversity of agroforestry classes did not seem to influence bird species richness. Forest specialist species were virtually absent in agroforestry classes, but the avifauna in agroforestry is diverse and valuable in itsel

Indicators of environmentally sound land use in the humid tropics: The potential roles of expert opinion, knowledge engineering and knowledge discovery

Despite abundant literature on indicators for sustainable resource management, practical tools to help local users to apply its general concepts at a local to regional level are scarce. This means that decisions over land evaluation and land use at a local level are often not based on the formal application of indicators or decision support systems for environmentally sound management but instead on the opinion of local expertise, for instance forest managers, cattle breeders, farmers and/or academics. This is particularly seen to be the case in the tropics where access to modern communication and information technologies is restricted. As the opinions of experts are often based on and influenced by personal experience, intuition, heuristics and bias, their evaluations and decision are often unclear to the non-expert working at a local level. In order to make their reasoning more comprehensible to the non-expert, the ecological condition of 176 plots in the tropical Southeast of Mexico were evaluated by experts on soil fertility, forest management, cattle breeding and agriculture. With the assistance of a knowledge engineer (one who converts expert knowledge and reasoning into a model), these expert opinions and reasoning were then translated into a formal computer model. As an alternative approach we applied a knowledge discovery technique, namely the induction of regression trees and automatically developed models using the expert evaluations as training data. Where knowledge engineering was tedious and time consuming, regression models could be rapidly generated. Moreover, the correspondence between regression trees and expert opinions was considerably higher than the correspondence between expert opinion and their own models. The regression trees used less explicative variables than the models generated by the experts. The minimisation of sampling effort due to variable space reduction means that the application of regression tree induction has a high potential for a rapid development of indicators for narrowly defined ecological assessments, needed for decision making on a local or regional scal

Effects of land use-change on some properties of tropical soils - An example from Southeast Mexico

We studied the effects of land-use and land-cover changes on physical and chemical properties of soil in tropical South-East Mexico. In the study area of about 5500 km2, the dominant land use is pastureland (Pa seasonal agriculture (TA), fruit plantations (FP), sugarcane, (SC) secondary (SF) and primary forest (PF) and other not specified land-use types (undefined). From 1988 to 2003 severe deforestation took place and pastureland increased by 179% while primary forest decreased to 17% of the initial area. Based on topographic and soil maps we selected 176 sampling sites covering the combinations of topography and soil type. In 2005, we took soil samples in each selected site from two soil depths (0–20 cm and 20–40 cm). We analyzed fertility parameters like pH, texture and contents of organic carbon, total nitrogen and available phosphorus. Furthermore, we measured soil resistance against penetration in layers of 5 cm down to a depth of 40 cm. We estimated land-use changes between 1988 and 2005 using digital land-use maps derived from satellite and aerial photography interpretation. We compared soil properties of different soil types, soils under different current land use and under the influence of land-cover changes. Gleysols, Vertisols, Regosols, Luvisols and Leptosols showed clay to clay loam texture, whereas Cambisols were characterized by sandy clay loam texture. All soil groups in the study region were slightly acidic with pH(KCl) values between 5.3 and 6.2. Furthermore, they neither showed significant differences in available P content nor in C/N ratio. However, the investigated soil associations displayed different organic carbon and total nitrogen contents in the upper 20 cm depth. Soils under different current land use did not show any significant differences with respect to available phosphorus, organic carbon, total nitrogen and C/N ratio whereas the pH value was significantly higher under seasonal agriculture than under pasture. Land-use changes between 1988 and 2003 did not significantly influence the contents of available phosphorus and organic carbon or the C/N ratio. However, total nitrogen was significantly higher in soils which were changed from forest in 1988 to seasonal agriculture in 2003 (F-TA) than in soils changed from forest to pastureland (F-Pa) or from pasture to forestland (Pa-F). Furthermore, soils under land-use change F-TA were less acidic in both depths than soils under Pa-F, TA-Pa, or which remained pastureland over the whole time (Pa-Pa). Soils in pastureland were significantly more compacted in all layers than soils used for seasonal agriculture. Soils that were used for pastureland already in 1988 showed significantly higher compaction than most of the other soils. We conclude that land-use change in a period of 15 years did not lead to chemical soil degradation. However, permanent pastureland leads to a severe compaction of soils

Mineralización en suelos con incorporación de residuos orgánicos en los altos de Chiapas, México

Atributos criticos de la region Altos de Chiapas son el relieve abrupto, suelos con baja disponibilidad de nutrientes y acidez, la intensificacion de su uso y el crecimiento de la superficie agropecuaria a expensas de los bosques. El objetivo del estudio fue conocer el efecto del estiercol de bovino, la cascarilla de cacao y la composta, incorporados a suelos Acrisol humico y Feozem haplico, cultivados o forestales, en la mineralizacion de la materia organica y su potencial para aumentar su fertilidad. La variable utilizada fue la tasa de mineralizacion, como dioxido de carbono formado en mezclas de suelo mas residuo organico, incubadas durante 10 dias. Se utilizo un diseno completamente al azar, con un arreglo factorial 4x4 y cuatro repeticiones. Ambos suelos cultivados, comparados con los forestales, disminuyeron 24 y 39% su contenido de materia organica e incrementaron 21 y 23% su densidad aparente. En los sitios cultivado y forestal, la incorporacion del estiercol, en el Acrisol humico tuvo tasas medias de mineralizacion de 180 y 146 ¿Êg CO2 g.1d.1 y en el Feozem haplico, 245 y 359 ¿Êg CO2 g.1d.1 respectivamente. Estas fueron mas altas (ANDEVA; F=3.33; p=0.0031) que sus controles y mezclas con cascarilla o composta. La incorporacion del estiercol mostro mayor potencial para restituir y aumentar su fertilidad. Este residuo incorporado al Acrisol humico cultivado incremento 164% la tasa de mineralizacion. Este incremento fue el mas alto de todos los sitios comparados con sus respectivos controles