Cacao Agroforestry Systems Research Articles

Effects of land tenure and urbanization on the change of land use of cacao (Theobroma cacao) agroforestry systems in southeast Mexico

Production of cacao and its products such as chocolate generate a global market. Despite demand, production has declined in a region historically important in the domestication of cacao in Mesoamerica. Chontalpa in southeast Mexico is an important area for cacao agroforestry systems, but a number of factors have affected current production, resulting in the elimination of many agroforestry systems. This study analyzes land use changes in the cacao production region of Tabasco State of SE Mexico using Landsat images from 2003 to 2016 to evaluate whether changes in cacao agroforestry systems into other land use forms are related to land tenure and distance to urban centers. Our results determined that land use changes were significantly lower in ejido lands, compared to other types of land tenure. A shorter distance to urban centers was associated with a higher probability of changing from cacao agroforestry systems to other land uses (grasslands, urban constructions). Members of young generations in the Chontalpa tend to move to urban centers that are continually growing at the expense of other land uses. Therefore, cacao agroforestry systems close to urban areas are more likely to change into this type of land use.

Deep soil carbon storage in tree-dominated land use systems in tropical lowlands of Kalimantan

Although carbon (C) stored deep in soils of tree-dominated land use systems in the tropics represents a large reservoir of organic matter its vulnerability to land use change has been hardly assessed. To fill this gap, we sampled Acrisols down to 3 m under three different land use systems; namely, recent cacao agroforestry (<2 years old; not deeper than 1 m), young and old rubber gardens (<10 years and >50 years), and secondary forest (>50 years) all located in Kapuas Hulu regency, West Kalimantan, Indonesia. We then assessed soil organic carbon (SOC) stocks as well as C accumulated in above- and belowground biomass, litter and dead wood debris at the soil surface. The amount of C stored in soils to a depth of 1 m exceeded the amount stored in living biomass (Σ C stored in roots, understorey and overstorey) strongly in the cacao agroforestry systems (69 Mg SOC vs. 12 Mg biomass-C ha−1), slightly in young rubber gardens (85 Mg SOC vs. 69 Mg C ha−1), but not in old rubber gardens (87 Mg SOC vs. 200 Mg C ha−1) and secondary forests (65 Mg SOC vs. 138 Mg C ha−1). Additionally in the older systems, up to 140 Mg C ha−1 (old rubber gardens) and 116 Mg C ha−1 (secondary forest) were found in soils to a depth of 3 m, thus raising soil C stocks by 60 to 80% relative to C stored in upper soil (0 to 1 m). We conclude that (1) the form of land use and land use change can substantially affect C stocks in living biomass, with aboveground biomass in old rubber gardens comparable to that of secondary forests; and (2) that land use change can reduce SOC in topsoil, but that substantial C stocks found in deep (down to 3 m) subsoil remain stable.

Stable carbon in soils under rubber tree (Hevea brasiliensis) agroforestry systems in the south of Bahia, Brazil

The early natural forest conversion to pasture, rubber tree plantations or agroforestry systems (AFSs) will not negatively affect soil organic carbon (SOC) accumulation due to the lack of soil tillage and the continuous contribution of vegetal residues to the soil, over the years, which would favor C occlusion in soil aggregates. The objectives of this study were: to evaluate the potential of AFSs with rubber trees to accumulate SOC up to 100 cm; to evaluate the δ13C variations over the soil profile after forest to pasture and rubber tree plantation (RTP) conversion; and to verify the C physical protection in aggregates as a mechanism of C stability in these soils. SOC was quantified up to 100 cm in whole soil and in three fraction-size classes (macroaggregates, microaggregates and silt + clay class). The occluded C was quantified in macro- and microaggregates by using an ultrasonic method. The relative contributions of C3 and C4 plants-derived C were quantified. The RTP system presented the highest SOC values, up to 100 cm depth, contributing with 20 Mg C ha−1 from belowground input, during 35-year old of system implantation. However, about 90% of SOC was not physically protected in the soil aggregates. The forest to rubber + cacao agroforestry system (AFS) conversion reduced SOC stock up to 100 cm approximately 72 Mg ha−1, and the reduction in SOC stock after forest to rubber tree + acai AFS was around 34 Mg ha−1. Rubber tree + cacao and rubber tree + acai AFSs had significant contributions of occluded C in soil aggregates.

Variation in fine root traits reveals nutrient-specific acquisition strategies in agroforestry systems

Changes in root functional traits reveal important nutrient acquisition strategies, with well documented patterns in root trait expression within complex communities or along gradients of singular nutrients. In this field study, we investigate intra-root functional trait expression with six soil macro- and micro-nutrients in Theobroma cacao agroforestry systems. Using image, chemical, and spatial analysis, the fine root distribution, architecture, and morphology of T. cacao were compared to localized soil nutrients on two-dimensional soil profiles with conspecific and heterospecific neighbours. Fine-scale variation in soil nutrients was observed within the range of T. cacao root systems. Higher NH4+ and Ca2+ was associated with greater root length and biomass densities, coupled with greater investment to individual roots, expressed as increased fine root tissue density and diameter and lower specific root length. Conversely, NO3− had the opposite effect. Overall, roots tended towards higher acquisitive trait values when next to a shade tree. Plants generally employ several concomitant and at times opposing strategies for nutrient acquisition in heterogeneous soils. We show that fine-scale root plasticity is highly linked to localized nutrient-specific and neighbour-specific effects, driving patterns of nutrient acquisition in agroforestry systems.

Invertebrates associated to Ponerine ants nests in two cocoa farming systems in the southeast of the state of Bahia, Brazil

The fauna associated to nest belonging to nine species of three genera of Ponerinae ants were studied in two cacao agroforestry systems (Cabrua and Derruba Total) in southeast of the state of Bahia, Brazil. A total of 27 invertebrates orders comprising 87 recognized taxonomic units (RTU), were found associated to these nests. No differences were found in the abundances recorded in both agroforestry systems. The high values of the species richness and diversity of associated invertebrates were recorded to Neoponera verenae in both agroforestry systems, while the lowest value was recorded for the nest of Mayaponera constricta collected only in Cabruca. The most frequent groups were Collembola which was found in 95.8% of the reviewed nest, follow by Acari (94.7%), Hymenoptera (other ants species as well as parasitoids; 86.2%), Coleoptera (69.1%), Araneae (51%) and Symphyla (48.9%). Our study also shows the importance of Ponerinae ants’ nests as safe habitats that are attractive to many invertebrate groups, and also the importance of the cacao agroforestry system to conservation of a range of invertebrates associated to the nests of these ants.

Formation of Macroaggregates and Organic Carbon in Cocoa Agroforestry Systems

ABSTRACT The objective of this study was to analyze the biological contribution to macroaggregate formation under cocoa agroforestry systems, as well as to evaluate the potential of macroaggregates to store carbon. The variation of the populations of macrofauna and the relationship with the morphology of aggregates was monitored in five agroforestry systems associated with cocoa established from different land uses, taking as reference the forest and pasture. Some cacao agroforestry systems favored the presence of macrofauna functional groups similar to the forest (p < 0.05). According to the principal component analysis, the effect of land use on macroaggregate formation is highly significant (p < 0.001) and explained 55% of the total variance. The macrofauna and macroaggregates showed significant covariation (RV = 0.22, p-value = 0.001). Biogenic macroaggregates contained more carbon when they came from agroforestry systems.

Exploring the suitability of bromeliads as aquatic breeding habitats for cacao pollinators

Bromeliads are common plants in the Neotropics. Being epiphytic, they are often incorrectly considered as parasites and removed from agroforestry systems. However, their water-filled leaf axils provide habitats for a diverse group of aquatic organisms, potentially including cacao pollinating dipterans which could be beneficial to local farmers. Thus far, it is unclear how frequently and abundantly potential pollinators occur in bromeliads in cacao plantations. Therefore, we investigated the aquatic fauna in different types of bromeliads in Nicaraguan cacao agroforestry systems. Our main goal was to study the impact of bromeliad morphology and vertical position on aquatic biodiversity with particular attention for larvae of presumed cacao pollinators. Aquatic biodiversity was higher in larger bromeliads and in bromeliads positioned closer to the ground. Particularly invertebrates without flying life stages were deficient in elevated bromeliads suggesting dispersal limitation. Potential cacao pollinators occurred in 66% of the bromeliads and were most abundant in bromeliads with larger tanks that were located higher in the canopy rather than on the plantation floor. We conclude that larvae of cacao pollinators can be common and relatively abundant inhabitants of tank bromeliads in cacao trees, and it is likely that preserving these habitats could boost local pollinator abundances.

Soil organic matter and CO2 fluxes in small tropical watersheds under forest and cacao agroforestry.

Annual estimates of CO2 and dissolved carbon concentrations in the soil profile provide valuable insight into the dynamics of organic matter in soil and the effect of changes to vegetation cover. The aim of this study was to observe the spatial influence of litter decomposition in the first few centimeters of the soil for CO2 fluxes and to describe the processing of soil organic matter throughout the soil profile by comparing three small tropical watersheds. Data were collected biweekly for six months, from December 2015 to May 2016. CO2 was measured using an infrared gas analyzer in fixed chambers and the dissolved carbon of soil solution was analyzed in a TOC analyzer. No differences were found in the total soil CO2 fluxes (control flux treatments) between the three study areas. In both cacao agroforestry systems (managed and unmanaged), total CO2 fluxes were influenced by the decomposition of litter. CO2 emissions in the soil profile of the cacao agroforestry systems were highly variable, compared to the preserved forest, and highly dependent on the soil characteristics attributed to the type of vegetation cover. Although a definite pattern between the temperature and soil moisture was not identified, these parameters showed a strong relationship in controlling the release of CO2 between treatments. The organic and inorganic dissolved carbon patterns in the soil solution of the three areas revealed different responses of soil organic matter processing related to soil characteristics and vegetation. The results confirm the hypothesis that the top of soils (total CO2 fluxes) of both cacao agroforestry systems (managed and unmanaged) emits fluxes of CO2, which do not differ statistically from the preserved forest. However, depending on the soil characteristics, the cacao agroforestry system can result in an accumulation of CO2 and dissolved inorganic carbon in the soil profile that is prone to being transported by hydrological routes to groundwater and stream water.

Shade trees composition and diversity in cacao agroforestry systems of southern Pará, Brazilian Amazon

Agroforestry systems (AFS) are important agricultural land use in synergy with socio-environmental aspects, especially with cacao (Theobroma cacao L.) crop, a commodity mainly produced by smallholders in the humid tropics. In southern Para, Brazilian Amazon, farmers manage native shade trees growing with cacao, but species selection may be not appropriate to AFS maintenance over time. The objective of this study was to understand the shade trees transition between successional management phases of cacao-AFS, considering its initial shade (IS) and secondary shade (SS). It was sampled 10 plots in each situation (20,000 m2 in total) identifying individuals with CBH ≥ 15 cm. As expected, floristic composition was different and SS had greater species richness and diversity than IS, where only 17% of species were the shared among them. Musa sp. and Carica papaya L. were found only in IS and were dominant species, representing almost a half of the individuals. Although there was increase of late succession species from IS to SS, this still keeps high abundance of early succession species, such as Cecropia sp. The result shows an unexploited potential products and gap of services provision, such as N-fixing. The conclusion highlights the necessity of long-term succession planning and management practices to guarantee cacao crop maintenance and improve diversification with other income sources, such as fruits and wood. The role of biodiversity conservation, provided by shade trees, should be the target of political strategies to encourage its maintenance, such as payment for ecosystems services or other economic incentives.

Entomofauna Associated with Agroforestry Systems of Timber Species and Cacao in the Southern Region of the Maracaibo Lake Basin (Mérida, Venezuela).

Agroforestry systems are environment-friendly production systems which help to preserve biodiversity while providing people with a way of earning a living. Cacao is a historically important crop in Venezuela that traditionally has been produced in agroforestry systems. However, few studies have evaluated how different trees used in those systems affect the dynamics and abundance of insects. The present study evaluated the entomofauna assemblages associated with different combinations of four timber-yielding trees and four Criollo cacao cultivars established in a lowland tropical ecosystem in Venezuela. A randomized block design with two replicates was used, each block having 16 plots which included all 16 possible combinations of four native timber trees (Cordia thaisiana, Cedrela odorata, Swietenia macrophylla, and Tabebuia rosea) and four Criollo cacao cultivars (Porcelana, Guasare, Lobatera and Criollo Merideño). Insects were collected with yellow pan traps and sorted to order. Coleoptera and parasitoid Hymenoptera were determined to the family level. In total, 49,538 individuals of seven orders were collected, with Hymenoptera, Diptera, and Hemiptera being the most abundant, although only Lepidoptera and Coleoptera abundances were significantly influenced by the timber tree species. Twenty-three families of parasitoid Hymenoptera and 26 of Coleoptera were found. Significant differences in insects’ assemblages were found both in parasitoid Hymenoptera and Coleoptera families associated to every shade tree, with the families Eulophidae and Lycidae being indicators for Cordia, and Chalcididae for Swietenia. The entomofauna relationship with the cacao cultivar was barely significant, although Scydmaenidae and Scarabaeidae were indicators for Lobatera and Merideño, respectively. No significant effects were found for interaction with cacao cultivars and native trees. We concluded that the particular insect assemblages found in Cedrela odorata and Cordia thaisiana, together with their high growing rates, make these two species an optimal choice for cacao agroforestry systems.

Carbon storage potential of cacao agroforestry systems of different age and management intensity

ABSTRACTThis study was carried out in Traditional and Innovative Cocoa Agroforestry Systems (CAS) of the Central Region of Cameroon. The aim was to assess carbon sequestration potential and tree species richness of each CAS. Sampling was done in 82 plots of 25 × 25 m in Traditional and Innovative CAS of different age classes. In addition to cocoa trees, associated trees with dbh ≥10 cm were inventoried. Aboveground biomass was evaluated using the non-destructive method for cocoa trees and woody plants and destructive method for herbaceous plants, litter and roots. A total of 5843 individuals belonging to 25 families, 35 genera and 39 species were inventoried in these CAS. The most represented species were Elaies guineensis and Carica papaya in Innovative CAS, Citrus sinensis and Dacryodes edulis in Traditional CAS. In the study area, species richness found in all Traditional and Innovative CAS sampled was respectively 38 and 6. Basal area and shade trees density of Innovative CAS were respectively 4.7 m2.ha−1, and 21 trees.ha−1 against 38, 13.7 m2.ha−1 and 84 trees.ha−1 in Traditional CAS. The total carbon stock of Traditional CAS represented three-times more (138.1 t C.ha−1) that of Innovative CAS (46.9 t C.ha−1). Carbon stock increased significantly with age of Innovative CAS whereas in Traditional CAS, there were no significant differences. Innovative CAS are less preferable as a basic model in the REDD+ process compared to Traditional CAS in carbon storage and biodiversity conservation contexts.

Variability and correlation of physical attributes of soils cultivated with cacao trees in two climate zones in Southern Bahia, Brazil

Cacao (Theobroma cacao) is a very important crop in Southern Bahia, Brazil, which needs good climate and soil conditions and management for great productivity. In this region, cacao is grown on a large number of soil types, and soil properties have great effects on its sustainability and production potentials. The aim of this study was to evaluate the variability of physical attributes of soils cultivated with cacao in two climate zones in Southern Bahia, Brazil, as well as to evaluate the correlation between these physical attributes. Eighty soil samples were evaluated from 20 cacao farms with cacao agroforestry systems, from the 0–0.1 and 0.1–0.3 m soil layers. The soil analyses comprised granulometry, soil bulk density, particle density, porosity (total, macro, and micro), gravimetric moisture, and soil resistance to penetration. The data were submitted to descriptive statistical analysis and correlation between variables. Most variables had normal distribution (p > 0.05) and high variability. In general, these soils had good physical conditions for the production of cacao, except for the high resistance to root penetration which can be limiting factor. The greatest differences in physical attributes of the soils were: gravimetric moisture, resistance to penetration, macroporosity, and sand content. The correlations between physical attributes of the soils varied according to the sampled layer and the climate zone. The resistance to penetration was not correlated with any of the determined physical attribute.

Soil microbial communities under cacao agroforestry and cover crop systems in Peru

Cacao (Theobroma cacao) trees are grown in tropical regions worldwide for chocolate production. We studied the effects of agroforestry management systems and cover cropping on soil microbial communities under cacao in two different replicated field experiments in Peru. In the first experiment, two agroforestry systems, Improved Traditional Agroforestry System (ITAS) and Improved Natural Agroforestry System (INAS), were compared. ITAS was a ‘slash and burn’ system in which all native vegetation was removed prior to replanting with cacao and other trees while INAS used selective removal of uneconomical trees followed by cacao planting. Soil microbial communities were analyzed by phospholipid fatty acid (PLFA) analysis and terminal restriction fragment length polymorphism (TRFLP) analysis. Soils in the ITAS system had altered microbial community structure and a lower Gram-negative to Gram-positive ratio when compared to soils in the INAS system. However, soil microbial community structure was also affected by a large soil pH gradient (three pH units) across this experiment. In the cover crop experiment, five cover crops, Arachis pintoi (perennial peanut), Calopogonium mucunoides (calopo), Canavalia ensiformis (jackbean), Centrosema macrocarpum (centro), and Callisia repens (callisia), and two controls (one with and one without nitrogen fertilization), were compared. Cover cropping with centro or perennial peanut increased the Gram-negative to Gram-positive ratio, while centro reduced the fungal biomass. Microbial community structure was significantly affected by cover cropping. Our results indicate that management systems and cover cropping can affect soil microbial community structure in tropical agroforestry systems, but the effects of soil edaphic properties must be considered as well.

Soil Quality Assessment for Yield Improvement of Clove, Cacao and Cardamom Agro-Forestry System in Menoreh Mountains Area, Indonesia

Soil Quality Assessment for Yield Improvement of Clove, Cacao and Cardamom Agro-Forestry System in Menoreh Mountains Area, Indonesia

Supporting and regulating ecosystem services in cacao agroforestry systems

Cacao agroforestry systems (CAFS) can provide supporting services such as optimum light conditions for cacao growth, water and nutrient cycling and regulating services such as pest and disease control and climate regulation. This review considers recent literature on the manifestation of these services in CAFS around the world to provide an overview of scientific knowledge. Crown structures of associated trees can facilitate optimum light conditions for cacao growth, and provide water through vertical root segregation. Leaf litter fall and roots from associated species contribute to nutrient cycling. Both nitrogen-fixing and non-nitrogen-fixing species can provide nutrients to the cacao plant, though competition from certain species may limit phosphorus and potassium uptake. Pest and disease regulating services can arise through careful shade management to create a microclimate which reduces susceptibility of cacao to fungal diseases and sun-loving pests. All CAFS store carbon to varying degrees; those resembling original forest much more than simple two-species systems from which shade trees are removed after maturity of the cacao stand. CAFS also promotes biodiversity conservation depending on structure, management, and landscape arrangement, though not to the extent of natural forests. Research opportunities to increase provision of these services include optimal spatial arrangement for nutrient cycling and functional diversity as well as landscape connectivity for biodiversity conservation. Trade-offs between carbon storage, biodiversity, cacao yield and socio-economic resilience are presented, indicating that optimization of ecosystem services in CAFS requires consideration of interactions between all services, including socio-cultural and economic ones. (Resume d'auteur)

Leaf litter and its nutrient contribution in the cacao agroforestry system

Cacao agroforestry systems (cacao-AFS) produce abundant litter. After decomposing, litter releases nutrients into the soil. The aim of this research was to estimate litter production and its nutrient content in 35- and 55-year-old cacao-AFS. The research was conducted in three cacao-AFS of each age, in Cardenas, Tabasco, Mexico. Four traps per cacao-AFS were used to collect litter. Litter was collected every 15 days for one year. It was then fractioned into cacao leaves, shade tree leaves, petioles, branches and stems, and cacao flowers and fruits. To determine nutrient content of litter, samples were composited by age of cacao-AFS and by season of the year. Then chemical analysis was done in triplicate. Data were subjected to analysis of variance, orthogonal contrasts, and Student t and Duncan tests. Cacao-AFS produce litter all year. Thirty-five-year-old cacao-AFS produced more litter than 55-year-old cacao-AFS (2042 vs 1570 kg DM ha−1 year−1). Except for the shade tree leaf fraction (559.5 vs 642 kg DM ha−1), 35-year-old cacao-AFS were superior to 55-year-old cacao-AFS in all the other litter fractions. Cacao leaf fraction was the main source of litter in cacao-AFS of both ages. Neither age of cacao-AFS nor the season of the year affected N, K, Zn or S content in litter. Orthogonal contrasts indicated statistical differences between ages of cacao-AFS for P, Ca, and Fe content in litter. Both N–P–K–Ca–Mg contents in litter of 35-year-old cacao-AFS (1.2–0.4–1.2–1.7–0.4%) and in litter of 55-year-old cacao-AFS (1.1–0.6–1.2–1.4–0.4%) are enough to recover the nutrients extracted by the cacao crop.

Contribution of associated trees to long-term species conservation, carbon storage and sustainability: a functional analysis of tree communities in cacao plantations of Central Cameroon

ABSTRACTIn Central Africa, most cacao is still cultivated in low-input agroforests where cacao associated trees are traditionally valued by farmers. These systems are sustainable on the long run, support biodiversity conservation and carbon storage. Yet, little knowledge exists on the contribution of tree community management to explain such results. In Central Cameroon, we investigated cacao agroforest associated tree community contributions to the long-term (i) maintenance of tree species encountering a conservation issue and (ii) carbon storage. We further simulated the simplification of these systems by checking for the effect of tree density decrease on community functional groups or traits. Finally, we linked farmers’ use of associated trees to their functional features and conservation status. Cacao agroforestry systems were able to combine high levels of species richness with long-term conservation abilities and carbon storage. Simplification emphasized consistent shifts of functional traits/groups that will change the way they function and alter the existing balances between different associated tree uses. Since traditional agroforests are now foreseen as providers of timber/non-timber forest products, our study argues that this paradigm change in such low-input systems - if carried improperly - is likely to impair the provision of the services they currently provide as well as their sustainability.

Cacao agroforestry systems have higher return on labor compared to full-sun monocultures

The global demand for cacao has recently increased. To meet this demand, the cultivated area has been expanded in tropical forest areas and production has intensified by replacing traditional agroforestry systems with monocultures. This has led to a loss of biodiversity in cacao-growing areas. More sustainable production systems such as agroforestry and organic managed systems are expected to yield less cacao, but by-crops and premium prices, respectively, might economically compensate for the lower yields. Here, we compared the productivity and the return on labor, that is the return per working day, of four different cacao production systems: agroforestry and monocultures under organic and conventional management. Cacao and by-crop yields, costs, revenues, and labor were registered during the first 5 years after establishment. Results show that cacao yields were, on average, 41% higher in monocultures, but the revenues derived from agroforestry by-crops economically overcompensated for this difference. Indeed, the return on labor across the years was roughly twice as high in the agroforestry systems compared to the monocultures. We found similar cacao yields and return on labor in conventional and organically managed agroforestry systems. However, in the monocultures, cacao yields were 48% lower under organic compared with conventional farming, but the return on labor was similar, mainly due to the higher costs associated to the conventional management. Overall, our findings show that cacao agroforestry systems have higher return on labor.

Shade tree diversity and aboveground carbon stocks in Theobroma cacao agroforestry systems: implications for REDD+implementation in a West African cacao landscape.

BackgroundThe promotion of cacao agroforestry is one of the ways of diversifying farmer income and creating incentives through their inclusion in REDD+ interventions. We estimated the aboveground carbon stocks in cacao and shade trees, determined the floristic diversity of shade trees and explored the possibility of implementing REDD+ interventions in cacao landscapes. Using replicated multi-site transect approach, data were collected from nine 1-ha plots established on 5 km long transects in ten cacao growing districts in Ghana West Africa. Biomass of cacao and shade trees was determined using allometric equations.ResultsOne thousand four hundred and one (1401) shade trees comprising 109 species from 33 families were recorded. Total number of species ranged from 34 to 49. Newbouldia laevis (Bignoniacea) was the most frequently occurring specie and constituted 43.2 % of all shade trees. The most predominant families were Sterculiaceae and Moraceae (10 species each), followed by Meliaceae and Mimosaceae (8 species each) and Caesalpiniacaea (6 species). Shannon diversity indices (H’, Hmax and J’) and species richness were low compared to other similar studies. Shade tree densities ranged from 16.2 ± 3.0 to 22.8 ± 1.7 stems ha−1 and differed significantly between sites. Carbon stocks of shade trees differed between sites but were similar in cacao trees. The average C stock in cacao trees was 7.45 ± 0.41 Mg C ha−1 compared with 8.32 ± 1.15 Mg C ha−1 in the shade trees.ConclusionsCacao landscapes in Ghana have the potential of contributing to forest carbon stocks enhancement by increasing the stocking density of shade trees to recommended levels.Electronic supplementary materialThe online version of this article (doi:10.1186/s13021-016-0061-x) contains supplementary material, which is available to authorized users.

Contrasting effects of habitat management on different feeding guilds of herbivorous insects in cacao agroforestry systems

Human pressure on natural habitats increases the importance of agroforests for biodiversity conservation. The objective of this study was to evaluate the role of cacao traditional cultivation system (CTCS) on the conservation of the herbivorous insect community when compared with a monodominant rubber agroforest, a type of agricultural system for cacao cultivation. The insects were sampled in three habitats in Southeastern Bahia, Brazil: native forests, CTCS and rubber agroforests. In each habitat, 18 plots of 10 m2 were established, and the structural measures were collected and herbivorous insects were sampled with a Malaise/window trap. The diversity of folivorous decreased with the simplification of vegetation structure, but species composition was similar among habitats. In addition to a decrease in the availability of resources in monodominant rubber agroforests, the latex present in these systems have limited the occurrence of species that cannot circumvent latex toxicity. The diversity of sap-sucking insects was similar among habitats, but species composition was similar only in the CTCS and native forest, and it was different in the rubber agroforest. We observed turnover and a higher frequency of individuals of the family Psyllidae in the rubber agroforest. The biology and behavior of Psyllids and absence of natural enemies enable their diversity to increase when they are adapted to a new host. We observed a shift in the composition of xylophagous insects in the rubber agroforest compared to that in other habitats. Moreover, this agroforest has low species richness, but high individual abundance. Latex extraction is likely an important additional source of volatile compounds discharged into the environment, and it increases the attraction and recruitment of coleoborers to these sites. We concluded that CTCS has an herbivorous insect community with a structure similar to the community found in native forests of the region, and they present a more interesting conservation strategy when compared to rubber agroforests. We also emphasized the potential risk of local pest outbreaks in rubber agroforests for both the rubber and associated cacao trees.