RESEARCH WORK

Faunistic characterization in a silvopastoral system intended for beef cattle

J. Iraola¹, E. Muñoz¹, Yenny García¹ and J. L. Hernández ¹

¹Instituto de Ciencia Animal, Apdo. postal 24, San José de las Lajas, Mayabeque, Cuba
E-mail: jiraola@ica.co.cu

ABSTRACT

The research was developed during five years, in order to evaluate the faunistic performance in a silvopastoral system intended for beef cattle. A mixed linear model was applied where the year, season and the year by season interaction were used as fixed effects, and the quadrants were used as random effect. The ecological indexes number of individuals, richness and diversity were determined. The tree survival and biomass production were also determined, and a biological carrying capacity Index was analyzed. Simple regression analyses were made among the biomass, the trees, and the indexes number of individuals and diversity. Difference (p < 0,001) was observed in the number of total individuals between the two initial years, while the second did not differ from the third and the fourth year differed from the fifth. The richness indicator differed (p< 0,001) among the different years. Likewise, there were differences (p< 0,001) in the biological diversity and positive relations were found among the tree component, the biomass and the indexes total individual number and species diversity. It is concluded that the silvopastoral system, as cover model, allowed a wider habitat for faunistic development, and improved the relation of the ecological indexes due to the presence of the trees and the increase of biomass in the system.

Key words: Fauna, habitat, silvopastoral systems.

The systematic succession of actions in the management that depends on external inputs and adverse practices by livestock production farmers with regards to the natural resources, soil, diversity, vegetation and water sources and natural flows, does not favor the balanced and natural functioning of pastureland agroecosystems to sustain the life capacity. Consequently, according to Fornara and Tilman (2009), Jarvis et al. (2010) and Rivera et al. (2013), if such actions are maintained or their excesses last in time, the systems tend to decline the diversity, the capacity to offer ecosystem services, or they can collapse.

According to DeClerck (2011), Iraola (2014) and Montagnini (2015), forestry arrangements, among them silvopastoral and agrosilvopastoral systems, frequently maintain a higher diversity of species and, thus, a higher functional diversity; and, in theory, they preserve the predicted ecosystem services.

In this sense, some studies conducted by Alonso et al. (2007) showed a significant increase in the species richness and Shannon biological diversity index, as a silvopastoral system composed by Leucaena leucocephala-Panicum maximum was developed for cattle milk production. Thus, the objective of this research was to evaluate the faunistic performance in a silvopastoral system aimed at beef cattle.

MATERIALS AND METHODS

Location and edaphoclimatic conditions. The study was conducted in experimental areas of the Institute of Animal Science, located at 22º 53' North latitude and 82º 02' West longitude, and at 92 m.a.s.l., in the San José de las Lajas municipality Mayabeque province, Cuba, on a Brown soil with carbonate (Hernández et al., 1999); such areas are dedicated to the production of beef cattle under grazing conditions.

The average temperature in the years the study lasted was 23 ºC, the highest one reached 34 ºC in August and the minimum was 5 ºC in January. The annual rainfall reached 1 426 mm, with the highest values in July (244,6 mm). The recorded values were similar to the historical averages of the last 43 years (data taken from the meteorological station of the Institute of Animal Science, 2014).

General characteristics of the experimental area. A restoration strategy was developed in a system of pasturelands for beef cattle under grazing conditions, with a physical surface of 50 ha; approximately 60 % of this area is characterized as degraded, as a consequence of overgrazing before starting the research. The system was divided into three paddocks and maintained a stocking rate of 2,5 heads per hectare. It did not have timber or fruit trees, only some living fences and less than 0,75 dispersed trees per hectare.

A silvopastoral system was used as a model of plant cover, adapted to the context where the research was developed. The restoration process involved: a) gradually developing a plant architecture per strata, with higher diversification of the vegetation in the physical space; b) including improved grasses, timber trees (590), fruit trees (493), living fences and leucaena in association with grasses, with population density between 5 000 and 7 000 plants per hectare and maintenance prunings every 2,5 years, without using irrigation or chemical fertilizers; c) leaving from three to 40 paddocks with limited access of cattle, resting for more than 50 days in the rainy season (RS) and no less than 60 days in the dry season (DS), with short occupation periods (of one to two days per paddock); d) making the transformations without stopping the zootechnical flow of four production cycles with Zebu genotypes and their crossbreds (1,48; 1,60; 1,80 and 1,80 animals ha^-1 year^-1, respectively), which achieved adequate growth (from 250 kg to 420 kg of LW), with good physical and health conditions at slaughter; e) providing, with the diversity of the plant community, different ecosystem services in the system.

Experimental procedure. The faunistic performance in the system was monitored during five years. For such purpose a mixed linear model was applied and the GLIMMIX macro was used through the software SAS version 9.1 (2007).

In the mixed linear model the year, season and year by season interaction were considered as fixed effect, and the quadrants were considered as random effect. The equation of the mixed model (MM) was the following:

y_jkl = ì + a_i + ß_j + (a ß)_j + F_k + e_ijkl

Where:

y_jkl= f (µ) value of the expected individuals

µ= general mean or intercept

a_i= fixed effect of the i-eth year (i = 1,..., 5)

ß_j= fixed effect of the j-eth season (j = 1 y 2)

(a ß)_j=effect of the i-eth year (i = 1,..., 5) in the j-eth season (j = 1 y 2)

F_k= associated random effect of the k-eth quadrant (k = 1, 2,..., 4)

e_ijkl = random error associated to the observations

Measurements. In order to observe the variations among the individuals as the restoration of the system advanced, an evaluation was carried out per season. For such purpose the transept method, described by Taylor (2003), was adapted. The system was divided into four quadrants of 12,5 ha, each of which included 10 paddocks of 1,25 ha. It was randomly walked in transepts and two spots were taken per paddock, with an approximate radius of 7 m and a minimum separation of 25 m; in them the observer, during 15 minutes, quantified the observed birds and also other species (frogs, rodents and reptiles). Between one spot and the other there was a 15-minutes wait to perform the sampling, and also there were 5 minutes of adaptation before quantifying the species in the morning (7:00 a.m.-9:00 a.m.), noon (11:30 a.m.-12:30 p.m.) and evening (4:30 p.m.-6:30 p.m.), with a frequency of three consecutive days per season in each quadrant.

The ecological indexes number of individuals per species (expressed in total), richness of species and diversity were calculated, and the percentage of birds per year was determined. The calculations were adapted through the method proposed by Fontenla et al. (1987), and the classical formulas suggested by Shannon-Weaver (1949) were used.

The percentage of timber and fruit trees that survived was determined by individual count, at the end of each rainy season. The production of herbaceous biomass was estimated according to the method proposed by Haydock and Shaw (1975), and 100 observations were made per paddock. In the case of the leucaena availability, the method proposed by Mahecha et al. (2000) was adopted: R²aj= 0,85. The calculation of biomass (tons of DM) was made with the aid of the CALRAC software (Roche et al., 1999). An index of biological carrying capacity (IBCC) was analyzed per year for this system, expressed among the individuals that were quantified (including the cattle) and the biomass.

For the effects that were significant in the model (p< 0,05) the multiple comparison test for the minimum quadratic means was applied, according to the Tukey-Kramer test (Kramer, 1956). The variables number of individuals and richness were transformed according to «x. Multiple regression analysis was carried out to explore the relation in time among the characteristics of the total trees present (timber trees, fruit trees, dispersed trees and living fences), the biomass and the fauna quantified in the silvopastoral system (number of total individuals and diversity) through the software SAS version 9.1 (2007).

RESULTS AND DISCUSSION

Table 1 shows the faunistic performance, its stability and its status during the five years of evolution and development of the plant community, as an indicator of the improvement of the ecological balance.

For the effect year difference was found (p < 0,001) on the number of individuals (birds, reptiles, frogs and rodents) between the two initial years; the second one did not differ from the third and the fourth year differed from the fifth one, in which 73 total individuals were found over the initial number (19) in the first year; among them the presence of different bird species stood out. On the other hand, the effects season and year by season interaction were not significant in the model.

For the indicator richness difference was found (p< 0,001) among the years. Difference was also observed (p< 0,001) for the Shannon index, and in the fifth year of the research this indicator increased from 1,08 to 2,17.

On the increase of the number of individuals and the richness of species in time the presence of the following birds had incidence: dickcissel (Spiza americana), yellow-faced grassquit (Tiaris olivaceous), cattle egret (Bubulcus ibis), mockingbird (Mimus polyglottos), common quail (Coturnix coturnix), among others, which represented between 63 and 78 % of the individuals.

The response in quantity and diversity of the fauna proved the capacity of the silvopastoral system to provide adequate conditions for the diverse forms of life that use different food sources. Thus, it is inferred that in the system the possibilities of self-regulation increased among the populations and they showed a certain degree of stability. Such status was observed for the indicators richness and diversity since the fourth year, mainly given by the presence of leucaena and the dispersed trees, controlled by the maintenance prunnings. Nevertheless, in the fifth year a relative increase was observed in all the indicators, which could have been related to the resilience capacity that agroforestry systems can offer against disturbances, according to Rivera et al. (2013).

As reported by Kimberly (2012), an adequate faunistic performance can be related to the best possibilities of habitats provided by the diversity of plant cover which in turn allows higher direct ecosystem services. In such sense, for the fifth year the production of herbaceous biomass, the presence of growing timber (survival of 66 %) and fruit trees (survival of 44 %), increased in 60 %, as well as the living fences (from 2 trees ha^-1 to 4 trees ha^-1) and the dispersed trees (from 117 to 608).

The presence of dispersed trees in the system allowed to improve the shade conditions for the animals, among other ecosystem benefits. However, at the end of this research 53 % of them were still in juvenile stages, and 9,58 randomly distributed trees ha^-1 were achieved as average. According to Iraola et al. (2011) and Iraola et al. (2014), this system showed the possibility of introducing a higher quantity of woody trees considered to be of protection, which would allow to provide in time a higher contribution of biomass and a higher ecological balance in the system.

In correspondence with the above-explained facts, Cárdenas (2002), Carpenter et al. (2009) and Marinidou et al. (2013) stated that a higher presence of tree component and the abundant herbaceous plant cover in the pastureland systems indicate higher possibilities of resources for the presence and refuge of the fauna. This is confirmed by some studies conducted in Cuba by Alonso (2011) and in Colombia by Fajardo et al. (2009), where several silvopastoral systems and grass systems were monitored. A Shannon diversity index higher than 0,83 was found in silvopastoral systems, while in the systems of grasses without trees it reached only 0,34. In that sense, there is coincidence with these authors in the fact that the presence of a tree component within livestock production systems benefits the increase of the fauna and, in turn, favors a better connection among the agroecosystems for the different forms of wildlife.

Thus, with an adequate management by men, the presence of trees would contribute to improve the useful life of pasturelands, to increase the functional diversity and to sustain a certain biological carrying capacity, changing in time and conditioned by many factors in each agroecosystem. Figure 1 shows the IBCC analyzed for this system from the observed individuals.

An improvement was found in the index of biological carrying capacity (from 0,36 to 1,50); hence the recovery was reached in harmony with the increase of the stocking rate of cattle and the other forms of plant and animal life with which it was directly or indirectly related in the system.

According to Garbach et al. (2012) and Iraola (2014), the IBCC is defined not only by the quantity, diversity, nutrient and energy production of the plant populations, but also by their capacity to hold and supply water and propitiate favorable habitats for the development of life, in which the different individuals co-inhabit and share in a certain system. This is confirmed by the favorable conditions that were propitiated with the development of this silvopastoral system, expressed by the IBCC.

On the other hand, positive relations were found, with determination coefficients higher than 80 % in all the cases, among the tree component, the biomass and the ecological indexes number of total individuals and diversity (fig. 2). This indicates that there was a close relation between the tree component that was being promoted in the system and the increase of biomass, which evidently had an important effect on the fauna, used as ecological and health indicator to show the evolution of the system during the five years of research.

From the results, the potential that can be reached by using a plant cover model such as silvopastoral systems is shown. This coincides with the report by Lang et al. (2003) in Costa Rica, where the presence of trees and the increase of biomass positively influenced the ecological indexes. Other results related to these ecological indexes were reported in Cuba by Alonso (2003) and Alonso et al. (2004) in a silvopastoral system with more than 10 years of exploitation for milk production, where favorable increases of biodiversity were reached.

The diversity this silvopastoral system could offer, used as cover model, confirmed the dynamic advantages of the interactions in such system, with a higher capacity of habitats for the associated fauna and possibilities for animal rearing. However, according to Vargas (2008), Laliberté and Legendre (2010) and Mouchet et al. (2010), there are no ideal ecological indexes that could explain all the situations in the agrocosystems. There is not a universal criterion either regarding which are the most important traits to be measured within a system; but the usefulness of the indexes that are quantified, in order to be able to monitor different aspects of functional diversity, depends to a large extent on the objectives conceived in each study.

In correspondence with the above-explained facts and according to such authors as Díaz et al. (2007), DeClerck (2011), Lavorel et al. (2011), Schneiders et al. (2012) and Montagnini (2015), an adequate management by man and a higher diversity of plants (grasses, legumes, shrubs and trees), together with the components (soil-animal-climate-man), would allow to achieve these purposes that are mentioned and contribute to the capacity of the system to provide ecosystem services and responses to disturbances. This not only guarantees the presence and refuge of the different life forms, but also generates a higher capacity to sustain life, where many species converge which can co-inhabit in the pastureland agroecosystems. Thus, the restoration of livestock production systems has to be aimed at a more environment-friendly livestock production, which can satisfy the ecological, productive and economic needs of human beings.

It is concluded that the silvopastoral system, as cover model, allowed wider habitats for the faunistic development and improved the relation of ecological indicators with the presence of trees and the increase of biomass production in the system.

ACKNOWLEDGEMENTS

The authors would like to thank the department of Biomathematics and the workers of the grazing cattle fattening farm Cebadero Ayala, of the Institute of Animal Science.

Received: April 16, 2015
Accepted: September 24, 2015