Arboreal / Arbustive Component Associated to Livestock Systems in San Vicente del Caguán Municipality , Caquetá — Colombia

Livestock is the most important economic activity in San Vicente del Caguán municipality, Caquetá department (located in Colombian Amazon region). Indeed, livestock activities have a big responsibility of Colombian Amazon forest deforestation for extensive grazing lands formation, causing soil degradation processes. However, recently some cattle ranchers have changed their thoughts to a sustainable production, applying different ecological strategies. So, application of silvopastoral systems, which is a very important mode of agroforestry, consists that in the same area and time, it can interact in the ecosystem stratums different species among grasses, shrubs, and trees. On this way, the objective of this study is to determine descriptively the arboreal/arbustive component associated to livestock systems, represented according to its uses in San Vicente del Caguán, Colombia. It was made through a direct survey to 13 smallholders in this municipality. As a result, mainly, we found 58 plant species (49 arboreal and nine arbustive, corresponding to 84.48% and 15.52%, respectively). Of these, 20 species had more than one use at a time. In fact, the shade was the use most common with 29 species, corresponding to 34.94% of total species (25 arboreal and just four arbustive, corresponding to 30.12% and 4.82%, respectively). On this way, according to smallholders surveyed, we can conclude that shade provided by trees integration in silvopastoral systems is for diminishing heat stress on cattle caused by enduring climate change of tropical, thus contributing to good welfare for animals.


Introduction
The bovine livestock is an important economic activity in Colombia, especially in Caquetá department/state, which is the 5 th position like the department in the greatest number of animals (1,486,685 bovines).Also according to bovine population census done by the Instituto Colombiano Agropecuario-ICA in 2017 [1], San Vicente del Caguán is the municipality of Caquetá department with most animals (688,004 bovines), contributing with 46.28% of the total from that department and 2.93% of the national total.Indeed, the San Vicente del Caguán municipality is supported economically by livestock activity, where dual-purpose livestock system is the most common, but this still is too traditional by the extensive way [2].In fact, this livestock practice has damaged natural ecosystem by irrational deforestation, transforming a big part of the Amazonian forest to large pastures [3] [4].In addition, soil resource has become less productive [3] [5], to point being a livestock system unsustainable on long [5].
However, recently cattle ranchers have changed their thoughts to a sustainable production, applying different ecological strategies [6] [7].On this way, application of silvopastoral systems, which are very important modes of agroforestry practice, consists that in the same area and time, it can interact in the ecosystem stratums different species among grasses, shrubs and trees [8] [9].
On the other hand, in livestock production, silvopastoral component/system is a recent trend in agroforestry that in practice, is a low-cost alternative for food production as well as environment protection [10] [11].Besides, it can promote soil conservation and nutrients recycling while producing fruits, fodder, timber and fuelwood [12] [13], constituting in productivity, environment and socioeconomics benefices [14].
On this way, the aim of this study is to determine descriptively the arboreal/arbustive component associated to livestock systems, represented according to its uses by 13 smallholders in San Vicente del Caguán, Colombia.

Materials and Methods
Information was taken from a direct survey to 13 livestock smallholders by field professionals in San Vicente del Caguán municipality, Caquetá department (Figure 1).It is located the Southern Colombia at 2˚6'55"N, 74˚46'12"W, with an area of 28,300 km 2 .It has an average elevation of 280 m and its annual rainfall median is 2486 mm/year, its mean temperature is 25˚C and relative humidity is 82%.Indeed, according to the Holdridge life zones, it is classified as wet forest.
On this way, we asked them about trees and shrubs associated to pasture into their farms, respectively.In fact, each one said us about such plants in its common names, moreover, about its respective uses, including: shade, timber, fodder, firewood, medicinal, water conservation and human food.
Then, for guaranteeing the accuracy of field information, each common name of such plants (tree/shrub) was collated and identified using three handbooks for American Journal of Plant Sciences plant identification in Colombian Amazon edited by the Instituto Amazónico de Investigaciones Científicas SINCHI [15] [16] [17].Thus, we determined its respective scientific name.Moreover, according to growth type characteristic of each plant (trees and shrubs), we confirmed the two types in this analysis: 1) arboreal and 2) arbustive, respectively.On the other hand, descriptive statistical was used for data analysis.

Results
We found 58 plant species (49 arboreal and nine arbustive).Of these species, 20 had more than one use at a time (Table 1).So, arboreal species constitute the largest component of all uses (Figure 2), especially for advantage its shade by livestock producers in San Vicente del Caguán municipality.Indeed, the shade was the use most common with 29 species (25 arboreal and just four arbustive).
In contrast, we found no arbustive species used for timber.
Moreover, arbustive species constitute the largest component of all uses, (Figure 2), especially for advantage its shade by livestock producers in San Vicente del Caguán municipality.In fact, we found no arbustive species used for timber.
On this sense, of all found 58 plant species, the proportions of arboreal and arbustive type species correspond to 84.48% and 15.52%, respectively (Figure 3).
According to all plant found, arboreal species were the most used in all usages surveyed.So, the shade was the most prominent with 34.94% of total specie (with a participation of 30.12% and 4.82%, arboreal and arbustive species, respectively).Although for timber use we did not found arbustive species, all were arboreal species with 21.69%.
In addition, fodder using is the third most important with 14.46% of the total    of the plants found (with a participation of 9.64% and 4.82%, arboreal and arbustive, respectively.).The rest of uses (firewood, medicinal, water conservation and human food) have a short participation with 10.84%, 9.64%, 4.82% and 3.61%, respectively.Indeed, in all these uses, arboreal species were more used than arbustive species, each one of these latter with just 1.20% of participation of all plant found (Figure 3).

Discussions
Amazon forest is the greatest rainforest on Earth, which has a notable influence on global climate, regulating global water and carbon cycles [18] [19].However,

% Arboreal/arbustive species
Uses American Journal of Plant Sciences a major of Amazon soils are poor in inorganic nutrients, but naturally, its fertility relays on nutrient cycling from organic matter via litter [20] [21] [22].So, organic matter is formed and incorporated from fallen leaves decomposition of rainforest trees for fertility maintaining [22].
There is the importance of trees for Amazon soil qualities maintaining.Nevertheless, deforestation has been a constant process for livestock expanding in Colombian Amazon region, transforming its rainforests to grazing pastures [23].
Indeed, deforestation has environmental effects to Amazonia [24], especially, resulting in its soil degradation process [23] [25] [26].Thereby, balance on the soil-plan-animal system is interrupted, causing ecological disturbance [25] Although Colombian Amazon forest has been affected by deforestation for grazing pasture establishment in livestock activity, this activity is indeed, the most important economic holding in San Vicente del Caguán municipality, where the dual purpose is the most common production system, but still is a too traditional way with extensive grazing [2] [25].
According to our results, we found that arboreal species (n = 49) were more numerous than arbustive species (n = 9) in all livestock farms visited.In this sense, we had waited that arboreal species were most used for timber, because there are a large number of timber tree species for logging in Colombian Amazon region [28].But, those were mostly used for shade.Nevertheless, some species have more one use at the same time.
In fact, P. guajava was arboreal species with the most uses (four: shade, timber, medicinal and human food) by smallholders surveyed in this study.On one hand, this species is widely used in tropical agro-pastoral and agro-silvopastoral systems for its positive impact in some environments [29].But otherwise, it is considered an invasive species in other regions, which has high dispersal and seed production that requires control practices of its density [30].
In addition, three arboreal species were found: A. squamosa, G. sepium and C. peltata, which had three combined uses at the same time but not for timber.In- deed, the two first species are commonly used in different agro-silvopastoral systems, where smallholders use their shade, mainly [31], as well as smallholders surveyed.Moreover, fruit A. squamosal is very used for human food and its timber for firewood [31].G. sepium is a leguminous plant that is widely used for fodder with high yield production and high nutritional quality [32] [33] [34] [35].Likewise, its leaves are just used for anti-atherogenic like medicinal [36].
However, this species has a special ability for N fixation, being used for intercropping and soil proprieties stabilization [31] [37] [38] and as alley cropping in Indonesia [39].
Even smallholder surveyed in this study said Yarumo tree (C.peltata) was used for fodder, firewood and water conservation; this arboreal species was not widely used in silvopastoral systems.In fact, there was a study about the silvopastoral usage of C. peltata in Guatemala, resulting in a species with high forage potential [40].However, this tree has a lot of medicinal uses in Venezuela and other tropical regions [41] [42] [43].
On the other hand, dual-purpose cattle production system involves bovine crossbreeding between types Bos taurus (humpless cattle of European and northern Asiatic origin, where is temperate climates and fertile soils) and Bos indicus or Zebu (humped cattle of southern Asiatic origin, where is very warm climates and poorly fertile soils) [44] [45].So, B. taurus gives high dairy production, in our case dual-purpose system; and B. indicus gives rusticity and high adaptability to warm climates, so similar to tropical region [45].On this, those cattle crossbreeding are made for achieving dual-purpose production system in San Vicente del Caguán municipality [46], as well as other places of tropical America [47] [48] [49].
Nevertheless, cattle adaptive capacities are not successful to endure high solar radiation [50] and climate change of tropical region, causing heat stress on it [51].Indeed, this stress has acute effects on cattle welfare, therefore on its productivity either [52].Thus, a way for lessening such effects is shade usage through the integration of trees to pastures in silvopastoral systems [53] [54], contributing to good welfare for animals [54] [55].
On this way, according to smallholders surveyed, we can conclude that shade was the most common use, and it was provided by trees integration for diminishing heat stress on cattle caused by enduring high solar radiation and climate change of tropical, thus contributing to good welfare for animals.However, some authors say pasture shade does not have significant effects on cow improvement productivity in tropics [56].In addition, shade may decrease the pasture biomass, contributing to soil compaction in the shaded areas due to the increase in the number of animals looking for comfort [57].
On the other hand, the integrated trees to pastures in silvopastoral systems give a lot of other benefits in livestock production [31] [55] [58] [59] [60], especially when managed with a greater trees density [61].Thus benefit not only includes animal welfare, but that also improves: soil fertility by nutrient dynamics; forage production; carrying capacity of the land; environmental conditions, increasing relative humidity, carbon sequestration/accumulation and reducing greenhouse gas emissions [62].Thereby, we recommend this system, not only by these benefits mentioned but also for farmer incomes by higher farm outputs, indeed, which is a cleaner way of achieving a biological, ecological and socio-economic livestock production efficiently and sustainably.

Figure 1 .
Figure 1.Location of studied livestock farms in San Vicente del Caguán municipality.

Table 1 .
Uses of arboreal/arbustive species found in San Vicente del Caguán livestock farms.