RESEARCH WORK

Edaphic mesofauna in different land uses in the Red Plain of Mayabeque and Artemisa, Cuba

Ana A. Socarrás ¹ y Nayla Robaina²

¹Instituto de Ecología y Sistemática. CITMA Carretera de Varona km 3½, Capdevila, Boyeros, C. P. 10800 Ciudad de La Habana, Cuba
E-mail: anameri@ecologia.cu
²Estación Experimental de Plantas Medicinales, Güira de Melena, Artemisa, Cuba

ABSTRACT

The conservation status of soils with different uses was characterized using the taxonomic and trophic composition of the edaphic mesofauna. The research was conducted during the rainy season of 2009 in 11 sites selected under four general classes of land use (GCLU): regenerated forests, pasturelands, sugarcane plantations and varied crops (mainly potatoes). Three soil samples were taken in each land use replication, at only one depth level (0-10 cm), following a stratified completely randomized sampling design. For the extraction Berlese-Tullgren funnels were used, with a source of light and heat, during seven days. The highest values of taxonomic composition of these soil microarthropods were found in the forests, with 16 families, followed by pasturelands with nine families, varied crops and sugarcane plantations with six families each. On the other hand, the largest representation of detritivorous groups appeared in the forest with four orders, 15 families and 151 individuals, followed by varied crops with two orders, five families and 62 individuals, and pasturelands with two orders, eight families and 37 individuals; while in sugarcane plantations fungivores were the best represented by an order and 22 individuals. The taxonomic and trophic composition of the groups that integrate the edaphic mesofauna indicated the soil degradation status in the order sugarcane plantation-varied crops, followed by pastureland and, finally, forest.

Key words: Multiple land use, soil fauna.

INTRODUCTION

The degradation processes that are present in Cuban soils (mainly those of ferralitic composition in the western region of the country), because of the intensification of agricultural and livestock production activities, as well as bad soil management, have a strong impact on the pH changes, soil porosity degree and decrease of the organic matter content and the structural stability of agroecosystems, according to the report by Masri and Ryan (2006).

Directly related to the transformation of soil properties, a component of the edaphic biota can be mentioned, which acts as microengineer of the ecosystem and contributes, efficiently, to the improvement of aeration, porosity, water infiltration and a higher contribution of nutritional sources throughout the profile. This zoological category is known as soil mesofauna, which main function is to participate in the organic matter decomposition increasing the action area of decomposing microorganisms through the fragmentation of plant residues. They also participate in the acceleration of nutrient recycling and the process of nitrogen and phosphorus mineralization (Seastedt and Crossley, 1980). Some of the groups that integrate it are detritivores, such as oribatids, springtails and uropods, which play an important role in soil fertility and stability; other groups are predators, herbivores and fungivores, and their main function is maintaining the balance of populations and the edaphic environment in general.

Precisely due to the ecological role they play, Usher et al. (2006) stated that many of the groups that form the mesofauna are considered bioindicators of soil stability and fertility, as they are very sensitive to the changes of the edaphic environment, and establish the soil conservation status in different land uses.

The objective of this work was to characterize, through the taxonomic and trophic composition of the edaphic mesofauna, the conservation status of ferralitic-composition soils of the Red Plain of Mayabeque and Artemisa, with different uses.

MATERIALS AND METHODS

The study was conducted in the Red Plain of Mayabeque and Artemisa, Cuba, in four land uses on Ferralitic Red soils (Hernández et al., 1999), in the period of highest rainfall of 2009 (October). A stratified random sampling protocol was followed; 11 sites in the selected areas were sampled in the four general classes of land use (GCLU), which are related below:

Regenerated forest. Three sites were chosen: two semi-deciduous ones located in Managua (22º56'44.80" N, 82º16'11.07" W) and Nazareno (22º58'05.40" N, 82º14'02.72" W) where timber species prevailed, such as Cordia gerascanthus L., Roystonea regia(Kunth) O. F. Cook, Calophyllum inophyllum L., Swietenia mahagoni (L.) Jacq.and Cedrela odorata L.; their herbaceous and shrubby strata allowed total soil cover. The other site was located in Aguacate (22º59'17.90" N, 81º50'01.03" W), with a high anthropization level and predominance of fruit trees, such as Pouteria sapota H. E. Moore & Stearn, Mangifera indica L., Persea americana L. and Crysophyllum cainito L.; the herbaceous and shrubby strata were dispersed.

Pasturelands. Two were selected: one is located in the dairy unit 3 of the Institute of Animal Science (23º00'01.50" N, 82º09'49.10" W), Güines municipality, where the Voisin rational grazing system was applied and the prevailing grass was Guinea grass (Panicum maximum Jacq.) with a 70% soil cover. The other chosen dairy unit was 025 from Guayabal (22º53'52.10" N, 82º02'08.12" W), San José municipality, without a defined grazing system. The prevailing species were star grass (Cynodon nlemfuensis Vanderyst) and Guinea grass with 90% soil cover. Neither area was subject to any type of additional organic input, except the litter from pastures and the direct contribution of cattle manure.

Varied crops. Three areas were selected, dedicated to agriculture for more than 10 years, located in the Güines (22º47'43.60" N, 82º02'31.46" W), Batabanó (22º46'42.40" N, 82º15'08.27" W) and Güira de Melena (22º45'40.50" N, 82º29'21.71" W) municipalities, with a traditional tillage system and electrical spray irrigation, of central pivot. In addition, the full NPK formula with a dose of 1 490 kg/ha and 224 kg of urea/ha were applied, as well as fertigation in three or four applications. The main crop of these areas was potato (Solanum tuberosum L.), which was in constant rotation with sweet potato (Ipomoea batatas L.), beans (Phaseolus vulgaris L.) and corn (Zea mays L.), among others. Weeds were represented by Sorghum halepense L. Pers., Amaranthus hybridus L. and Cyperus rotundus L.

Sugarcane plantations. Three sugarcane production units were sampled, from the Güira de Melena (22º50'24.80" N, 82º26'50.56.» W), San Nicolás de Bari (22º46'32.60" N, 81º55'05.90" W) and Madruga (22º58'47.00" N, 81º50'49.24" W) municipalities. Each area had been exploited for more than 20 years and had an extension of around 15 ha. The sugarcane (Saccharum officinarum L.) varieties used were CP 52-43, C 86-12, C 323-68 and C 86-56. Gravity irrigation was used, with an adequate land leveling. The following inorganic fertilization doses were applied: N (62,13 kg/ha), P2O5 25,73 kg/ha) and K2O (82,78 kg/ha). The main weeds detected were S. halepense, C. rotundus, Rottoboellia conchinchinesis L.F. and Eleusine indica (L.) Gaerth.

Sampling of edaphic mesofauna

Three soil samples were taken in the 11 sampling sites, at only one depth level (0-10 cm), with a cylinder of 5 cm diameter and 10 cm depth.

For the extraction of the edaphic fauna, Berlese-Tullgren funnels were used, with a light and heat source, through the direct action of 40-W fluorescent lamps, for seven days. The individuals were counted and separated under the stereoscope, with the aid of a teasing needle. The collected specimens were preserved in 70% alcohol and they were identified according to the classification of Brusca and Brusca (2003) and Krantz (2009) to the family category

Statistical data processing

In order to corroborate the best represented groups from the trophic point of view in each sampling site, the Kruskal-Wallis test was used; in the cases in which the differences were significant, the Student-Newman-Keuls (SNK) test was applied. The statistical processing was made using the package of the automated program TONYSTAT (Sigarroa, 1987).

RESULTS AND DISCUSSION

Taxonomic composition in the different land uses

The mesofauna communities in the four land uses (GCLU) belong to the phylum Arthropoda, represented by two subphyla, three classes, two subclasses and seven orders. Particularly, the subclass Arachnida was composed by four orders. The orders Collembola, Oribatida, Mesostigmata and Diplura were represented by 17 families, and for the orders Astigmata, Prostigmata and Psocoptera 41 morphospecies were determined (table 1).

In the forest a total of 170 individuals were obtained belonging to the two classes, one subclass, six orders and 16 families. From the subclass Arachnida, Oribatida was represented by nine families, Mesostigmata by two and Astigmata by the lowest amount of individuals. The order Diplura was represented by one family and Collembola by four families.

Prieto et al. (2005) reported a higher number of families for Oribatida in another Cuban secondary forest (21 families). The use regenerated forest showed certain anthropization degree, as one of them was dedicated to environmental education and the recreation of its inhabitants; in addition, there was not much litter accumulated on the soil and the herbaceous and shrubby strata were scarce, although the tree canopy provided large shade. These aspects can be the cause of the family number decrease of these orders in this case.

Nevertheless, in this land use four families of the order Oribatida appeared exclusively, two of Collembola, one of Mesostigmata and one of Diplura (table 1). The families of the order Oribatida were: Nothridae, Haplozetidae, Protoplophoridae and Collohmanidae, which show a more whitish body with less chitin, characteristics which make them more sensitive to alterations of the edaphic environment. Dicyrtomidae and Onychiuridae are the families of springtails which only appeared in the regenerated forest. The former is acknowledged by specialists as indicator of preserved areas as they show lower ecological plasticity due to their morphological characteristics (globose and little chitinized body); while Onychiuridae is considered a bioindicator of the disturbance in plant stratification (González et al., 2003). On the other hand, Arroyo et al. (2003) reported in Spanish agroecosystems the presence of these springtails in all plots, which provides information of their high ecological value as biological indicator of the health of edaphic ecosystems.

Uropodidae and Campodeidae were the families from the orders Mesostigmata and Diplura, respectively, which were found only in the use regenerated forest. Both families need abundant organic matter and moisture for the establishment and development of their populations.

An impoverishment in the total number of organisms (43), orders (four) and families (nine) was observed in grazing, and the number of classes and subclasses present was preserved as compared to the taxa reported for the forest (table 1). In this land use eight families were found, six from the order Oribatida and two from the order Collembola. The presence of the family Oppiidae only in this use indicates disturbance or alteration of the edaphic environment. Berch et al. (2007) consider it an indicator of disturbance in pasturelands and agroecosystems, and pioneer when colonizing agricultural areas.

Another family of mites with a less restricted distribution is Ceratozetidae, which appears in the uses regenerated forest and pastureland and is considered poor in agroecosystems and ecosystems altered by anthropic activity (Norton, 1994).

In the uses destined to varied crops a total of 113 individuals representatives of three classes, two subclasses, six orders and only six families, were obtained. In the sugarcane plantation 54 specimens were present, belonging to two classes, one subclass, four orders and six families. In both land uses the families belonged to the following orders: four to Oribatida, one to Collembola and another to Mesostigmata. Arroyo et al. (2003) found, in cultivated fields in Spain, similar results as the ones obtained in this study regarding the number of families present for oribatids; while other authors refer for springtails higher values of family richness in cultivated fields with common beans, coffee and sugarcane, in Costa Rica and Cuba (González et al., 2003; Guillén et al., 2006).

The agroecosystems were subject to disturbances in their physical, chemical and biological properties of the edaphic environment, due to the intense tillage and the application of pesticides and chemical fertilization to the crops, which caused the elimination of groups susceptible to temperature increase and humidity decrease, as well as the destruction of niches, especially of those taxa with a longest life cycle as in the case of oribatids (Behan-Pelletier, 1999).

Specifically in the edaphic fauna there is disappearance of «exclusive» taxa, which are more fragile before environment disturbances and are substituted by cosmopolitan taxa, pioneer of altered environments (Wardle et al., 2004). This is the case of the families Scheloribatidae, Oribatulidae, Achipteridae and Galumnidae, common and with a higher number of individuals in all the studied land uses. According to Norton (1994) the families Scheloribatidae and Oribatulidae respond to agricultural practices in a predictable way and they can be used to know the soil degradation status, and the Galumnidae family is tolerant to environmental fluctuations. In the case of springtail families, Poduridae was the best represented in all land uses; while Hipogastruridae was present only in the regenerated forest and the pastureland.

Trophic composition of the mesofauna components in the different land uses

The communities of soil microarthropods were composed by three trophic categories: detritivores, predators and fungivores (fig. 1). The Kruskal-Wallis test showed significant differences among trophic groups regarding the number of individuals (forest: H = 21,01; pastureland: H = 8,27 and varied crops: H = 7,81 p<0,05, gl = 2), and according to SNK detritivores were the most abundant in the forest, the pastureland and in varied crops. In the sugarcane plantations (H = 1,33, p<0,05, gl = 2) there were no significant differences among these trophic groups, and fungivores were the most represented in such use.

A higher number of detritivore individuals (151) and families (15) was observed in the regenerated forest than in the other soil uses; among them there were very demanding taxa in terms of the edaphoclimatic conditions and the quality and quantity of the available organic material for its decomposition. The majority presence of this trophic group is an indicator of the fertility and stability of the edaphic environment. This land use had an average of 80 years of establishment and it showed neither livestock production interventions nor addition of external sources of organic material, or chemical products; for such reason it can be considered as a more ecologically stable and balanced use, with a higher number of plants with mycorrhizal associations, which also serve to feed the populations of the edaphic mesofauna and improve the conditions for the establishment of these trophic groups (Bardgett and Wardle, 2003).

In this same land use the representation of fungivores was minimal (three) in spite of the food abundance (fungi) this group has, according to the report by Ponce de León et al. (2009). Fungivores, represented by the order Astigmata, are a group that consumes fungal hyphae and mycelia, abundant in soils with natural or anthropic disturbances, for which it is known as a good indicator of the ecological conditions of the edaphic environment (Andrés, 1990).

Predators were observed in the regenerated forest, with a representation of 16 individuals. In this use a higher number was found of individuals that constitute their prey (immature stages of oribatids and springtails). Vásquez et al. (2007) stated that their quantities depend on their prey, but always in lesser amounts, because their role is to control the edaphic fauna communities; when this ratio is not respected, this trophic group becomes an indicator of soil disturbance or alteration.

In the pastureland 37 individuals with detritivore habits were reported. These pasturelands had been established for 80 years as average, with approximately 80% cover, which favors temperature decrease and moisture increase in the edaphic environment; in addition, they were managed with a low or moderate stocking rate, which guarantees a discreet additional contribution of organic matter to the soil; all these are important factors for the development and permanence of this trophic group in such use type. Similar results were found by Socarrás (2006) in a pastureland with similar characteristics, in an organically managed farm of the Artemisa province.

The presence of fungivore organisms (2) and predators (4) was poorly represented in this pastureland. In the case of fungivores this could have occurred due to the lower amount of fungi reported by Ponce de León et al. (2009), which constitute their food source.

In spite of the intense tillage and the supply of pesticides and chemical fertilization, a high number of detritivores (62) was reached in the land used destined for varied crops. Their abundant presence could have been associated to a high percentage of weeds together with the crop, which increased soil cover, beneficial aspect for the mesofauna establishment by providing shade, decreasing temperature and increasing soil moisture and food availability. Thirty-seven fungivores were found, due to the influence of the adverse conditions that are present in this use type. Predators had a lower presence (13), but there was a higher quantity of different groups and higher prey availability.

In sugarcane plantations the minimum values of detritivore organisms (15) were observed. This is a crop with a non uniform plant cover, with chemical fertilization and intense tillage, aspects which do not favor the presence and establishment of these edaphic groups. Nevertheless, in this land use the conditions favored the establishment of fungivores (22) and predators (17), which reached a wide representation by responding positively to the disturbances caused in the edaphic environment; in addition, the fungi values reported by Ponce de León et al. (2009) for this use allow having a remarkable food amount for their establishment.

In general, the trophic structure of the mesofauna communities in the studied uses showed different strategies in the regulation of edaphic processes. The predominance of a detritivorous fauna in the forest, the pastureland and varied crops should contribute to prevent the accumulation of a higher quantity of the organic matter that enters these systems, favoring decomposition rate and the nutrient cycle. In the use sugarcane plantation, the plant cover is less homogeneous and, thus, the soil is more exposed to sun incidence and rainfall, and the nutrient mineralization and leaching processes occur more intensively. In this case, the higher proportion of fungivore organisms compensates these processes, by crushing fungal material and accelerating nutrient decomposition and incorporation to the soil.

CONCLUSIONS

1. The edaphic mesofauna communities in the four land uses were constituted by a phylum, two subphyla, three classes, two subclasses, seven orders and 17 determined families.

2. In the forest 16 families were found, 15 detritivore ones and from them eight were exclusive of this use; in the pastureland there were nine families, eight detritivore ones and only one exclusive; while in varied crops and sugarcane plantations six families appeared, five of them detritivores and all generalists.

3. In general, the taxonomic composition and the presence of detritivore groups of the edaphic mesofauna increased in the sense: sugarcane plantation-varied crops, followed by pastureland and, finally, forest, which indicates the soil conservation status in each land use.