Shade Tree Diversity Research Articles

Impact of common shade tree species on microclimate and cocoa growth in agroforestry systems in Ghana

Climate change is a growing threat to agriculture globally, with most substantial impacts expected in tropical smallholder systems such as cocoa farms in West Africa. Cocoa agroforestry is widely believed to enhance resilience to climatic extremes due to protection and a favourable microclimate under the shade trees. Morphological traits of many locally used shade tree species and their specific contribution to microclimate for climate-resilient cocoa production remain unclear. Therefore, aboveground morphology and sub canopy microclimate of eight common shade tree species were investigated in cocoa agroforestry systems in the Ahafo region, Ghana. Additionally, the growth of cocoa trees in three different distance zones to the shade tree stem was measured. The eight different shade tree species exhibited considerable variation in their impact on microclimate and cocoa growth. M. indica and M. excelsa allowed lowest light transmission, with the highest microclimatic buffering effect, i.e., reducing vapour pressure deficit and daily fluctuations of temperature and relative humidity. Cocoa trees around M. lucida and F. capensis were the highest in growth, characterized by height and stem diameter. However, a universally superior shade tree species could not be identified implying the need for shade tree diversity allowing various microclimatic conditions within an agroforestry system to spread risk of climate extremes. Cocoa tree growth was more affected by distance to the shade tree than by shade tree species, resulting in enhanced growth with distance to the stem. These findings provide a better understanding of species-related differences on cocoa growing conditions and climate change adaptation strategies.

Shade tree trait diversity and functions in agroforestry systems: A review of which traits matter

Abstract Shade trees in agroforestry systems confer ecosystem services, such as enhanced soil fertility from diverse litter inputs, microclimate regulation via shade, and disease mitigation through trophic and abiotic interactions. With this thriving role of agroforestry in sustainable agriculture, particularly for tree crops, systematic and reliable methods to select shade trees for specific agroecosystem outcomes are crucial. Plant functional traits offer a framework to describe, select and manage shade trees. Over the last decade, shade tree leaf functional traits and whole plant traits have been assessed in agroforestry systems. Yet, we lack amalgamated information on (i) what we know about shade tree trait relationships with functions to achieve desired agroecosystem outcomes, (ii) how decades of shade tree selection by farmers impacts agroforests inter‐ and intraspecific trait diversity, and (iii) which shade tree traits should be considered for achieving farmer priorities. We consolidate literature on Coffea arabica (coffee) and Theobroma cacao (cocoa) agroforestry systems to summarize the role of shade tree functional traits in three key ecosystem functions: soil fertility, microclimate modification and crop productivity. We compile global and regional datasets on tree functional trait diversity to show the functional space of agroforestry tree species compared with the overall functional space observed in plants. Despite, or maybe because of, high shade tree diversity, shade tree trait characterization remains coarse and commonly measured at the community scale in the literature. Based on published trait data, we show that farmers adjust the functional composition of shade trees to increase the recycling of soil nutrients (high leaf nitrogen), the production of wood (skewing towards lower wood densities) and the production of fruits (tendency towards high seed size). Common shade trees in coffee and cocoa systems fall in the mid‐range of leaf acquisitive to conservative strategies, providing evidence that expanding shade tree portfolios can improve, or even accelerate, functions. Synthesis and applications: Based on the agroforestry literature and on trait‐environment relationships, we propose a matrix of shade tree traits that influence desirable agroecosystem outcomes for farmers, which can guide fine‐scale coordination of trait expression and agroforestry functions.

The dynamic of shade trees in cocoa agrosystems

Cocoa agrosystems can provide available habitats for wildlife species, due to the structure and diversity of established shade trees in plantations. The objective of this research is to calculate the index of importance and forest value of shade trees used in cocoa agrosystems in the region of Comalcalco, Tabasco, Mexico. Field sampling was carried out to collect data on breast height diameter, canopy diameter and canopy height, these variables were used to estimate the importance value index and the forest value index. The trees with the best indexes of importance and forest value are Erythrina americana (IVI = 62.34 and FVI = 50.94), Bursera simaruba (IVI = 62.53 and FVI = 66.99) and Samanea saman (IVI = 56, 85 and FVI = 42.93). The dynamic of shade trees in cocoa agrosystems is important since it could be used as an input variable to evaluate and predict, through an ecological niche model, the quality of the available habitat for the conservation of wildlife such as birds, reptiles and arboreal mammals.

Ecological quality as a coffee quality enhancer. A review.

As both coffee quality and sustainability become increasingly important, there is growing interest in understanding how ecological quality affects coffee quality. Here we analyze, for the first time, the state of evidence that ecological quality, in terms of biodiversity and ecosystem functions, impacts the quality of Coffea arabica and C. canephora, based on 78 studies. The following ecosystem functions were included: pollination; weed, disease, and pest control; water and soil fertility regulation. Biodiversity was described by the presence, percentage, and diversity of shade trees. Coffee quality was described by the green bean physical characteristics, biochemical compounds, and organoleptic characteristics. The presence and diversity of shade trees positively impacted bean size and weight and reduced the percentage of rejected beans, but these observations were not consistent over different altitudes. In fact, little is known about the diversity of shade trees and their influence on biochemical compounds. All biochemical compounds varied with the presence of shade, percentage of shade, and elevation. Coffee beans from more diverse tree shade plantations obtained higher scores for final total organoleptic quality than simplified tree shade and unshaded plantations. Decreasing ecological quality diminished ecosystem functions such as pollination, which in turn negatively affected bean quality. Shade affected pests and diseases in different ways, but weeds were reduced. High soil quality positively affected coffee quality. Shade improved the water use efficiency, such that coffee plants were not water stressed and coffee quality was improved. While knowledge on the influence of shade trees on overall coffee quality remains scarce, there is evidence that agroecosystem simplification is negatively correlated with coffee quality. Given global concerns about biodiversity and habitat loss, we recommend that the overall definition of coffee quality include measures of ecological quality, although these aspects are not always detectable in certain coffee quality characteristics or the final cup.

Shade tree diversity may not drive prey-predator interaction in coffee agroforests of the Western Ghats biodiversity hotspot, India

Agricultural intensification can decrease biodiversity and ecosystem services they deliver to agroecosystems. Diverse trees-shaded coffee is structurally and functionally complex and has biodiversity adequate for sustainable production of coffee and mitigation of biodiversity loss due to deforestation. However, shade tree simplification is intense in coffee agroforests worldwide, threatening their economic and environmental targets. In south India, native trees have been replaced by silver oak (Grevillea robusta) trees. Native trees-shaded coffee is floristically complex and diverse than oak-shaded coffee. We hypothesize that the natural prey removal fares better in native trees-shaded coffee than in oak-shaded coffee. Artificial caterpillar models of three colors were installed rotationally on leaves, stems, and branches of coffee plants in native trees-shaded- and oak-shaded coffee, and assessed the predation rates for fruiting and leaf-flushing periods of coffee to test this. Forty-four percent of the caterpillars were predated. Arthropods, and in particular the ants, were the predominant predators. Lizards followed by birds, and mammals were second, third, and fourth important predators of coffee agroforests. Overall, predation rates did not differ with the shade diversity, but lizard predation rates were higher in diverse trees-shaded coffee than in oak-shaded coffee. The predation rates were slightly higher in the fruiting season of coffee. Predation rates of any predator taxa were higher for the caterpillars placed on stems and branches than on leaves. The study does not support the hypothesis that the natural predation rates might be higher in floristically complex coffee agroforests, but highlights the biocontrol potential of lizards in diverse-shaded coffee.

Disease prevalence and shade tree diversity in smallholder cocoa (Theobroma cacao) farms: case of Bundibugyo District, Western Uganda

Cocoa (Theobroma cacao) growing systems in Uganda consists of shade systems with different tree species. Tree shade systems are the pure stand trees in the cocoa plantation which have been attributed towards reducing on pests and disease incidences, shade provision, boosting fertility, Agro biodiversity, fodder and improving production. The study was aimed at identifying potential shade tree species that can minimize disease threats on cocoa farms. Eighty-two cocoa farmers were reached out of 120 cocoa farmers in Bundibugyo that possessed at least five acres of the plantation in a purposive sampling approach.
 Black pod disease was non-significantly associated with presence of shade tree diversities. It was established that incidence of black pod rot disease was non-significantly associated with presence of all shade tree species; association between witch’s broom disease incidence with presence of Maesopsis eminii was highly significant (χ2= 55.41, (p<0.05); Association between witch’s broom and presence of Persea Americana (χ2=9.79), (p<0.05), Eucalyptus globulus (χ2=16.71), (p<0.05), Markhamia obtusifolia (χ2=3.95), (p<0.001), schefflera actinophylla (χ2=4.32), (p<0.001), Mangifera indica (χ2=6.46), (p<0.001) was significant though these trees were planted in small numbers. Association between frosty rot disease incidence with presence of Maesopsis eminii was highly significant (χ2= 25.90), (p<0.05). there was a significant association between frosty with presence of Eucalyptus globulus (χ2=6.76), (p<0.05); Mangifera indica (χ2=4.85), (p<0.001); though these trees were planted in small numbers. There was a highly significant association between swollen shoot virus with presence of Maesopsis eminii (χ2= 31.55), (p<0.05), and Cinnamomum tamala (χ2= 19.22), (p<0.05). Association between die back disease incidence with presence of Maesopsis eminii was highly significant (χ2= 52.73), (p<0.05).

Rehabilitation practices in cocoa agroforestry systems mitigate outbreaks of termites and support cocoa tree development and yield

Most smallholder cocoa farmers in West Africa are not equipped with the necessary tools, techniques, and practices to rejuvenate their aging cocoa farms. Instead, they rather prefer to establish new cocoa farms at the expense of forest remnants. Poor management of their overaged farms has resulted in the emergence and outbreaks of new pest species such as termites feeding on the remaining productive trees and negatively affecting overall yield. We investigated how rehabilitation pruning of cocoa trees influences termite outbreaks and yield in three cocoa agroforestry systems (rustic, intermediate and full sun systems). We monitored cocoa and non-cocoa trees at different development stages after rehabilitation pruning and assessed termite diversity and damage. We demonstrated that farm rehabilitation practices are associated with high beta diversity of shade trees and linked with a high diversity of beneficial termite species. Cocoa trees and farm age were positively correlated with the level of infestation by termite species. We also showed that rehabilitation practices improve cocoa tree vigor and yield in cocoa agroforestry systems with the intermediate systems as the most productive after pruning (167 % of yield increase after pruning). Rehabilitation pruning is a suitable practice to rejuvenate aging trees and increase short-term cocoa yield while mitigating the negative effects of insect pests such as termites. It could be recommended as an effective measure for sustainable cocoa production, thereby enhancing ecosystem services provided by local biodiversity and avoiding forest clearance.

Estructura y carbono específico en una cronosecuencia de sistemas agroforestales de Teobroma cacao L. en Tabasco, México

Ante el impacto que representa el cambio de uso de suelo en la pérdida de biodiversidad y deterioro del medio ambiente, los sistemas agroforestales de cacao de sombra son una alternativa para la conservación de biodiversidad y almacén de carbono. El objetivo de este trabajo fue conocer el efecto de la edad de los sistemas agroforestales de cacao en la diversidad arbórea y almacenes de carbono de su vegetación de sombra. Se compararon 258 parcelas distribuidas en once sistemas agroforestales entre 10 años y 70 años, totalizando 7.87 ha. Dentro de cada parcela se midió el diámetro normal (DN) y altura total de todos los árboles >5 cm (DN) para estimar su biomasa aérea con una ecuación general y otra específica, y conocer la discrepancia de ambos métodos. Los sistemas agroforestales de 70 años presentaron en promedio más especies arbóreas por hectárea (23), índice de diversidad Shannon (2.0) y almacén de carbono (75 Mg ha-1) que los de 10 años (p < 0.01; 10 Mg ha-1, 1.1 Mg ha-1 y 36 Mg ha-1; respectivamente). La ecuación alométrica específica estimó 27.7% (p = 0.05) más biomasa aérea que la ecuación general, por lo que se considera de mayor precisión para estos sistemas agroforestales en particular, y se recomienda su uso para estos tipos de vegetación. Se concluye que, particularmente para México, conservar sistemas agroforestales de cacao de edad madura contribuye a la conservación de la biodiversidad arbórea y almacenes de carbono de la vegetación tropical, asemejando relictos de la vegetación original.

Biomass and carbon stocks of organic and conventional cocoa agroforests, Ghana

Cocoa production is a globally important commodity that has been a major driver of deforestation in humid tropical areas. Cocoa agroforestry systems have been credited for storing significant stocks of carbon potentially mitigating some of the negative impacts of cocoa production on ecosystem services but the impact of organic management on this potential is unclear, especially in Africa. We quantified cocoa and shade tree biomass, above and below ground and soil carbon stocks of 42 organic and 42 conventional cocoa agroforestry systems in Ghana (a globally important cocoa producing country) across three cocoa-age groups; young (≤ 15 years), mature (16–30 years) and old (≥ 31). We used the carbon stocks data to estimate the monetary value of the stored carbon in the two systems. Mean aboveground biomass C (Org. 41.3 ± 3.62 vs. Con. 22.9 ± 2.60 Mg C ha−1), belowground biomass C (Org. 7.8 ± 0.67 vs. Con. 4.2 ± 0.66 Mg C ha−1) and soil C stocks (Org. 59.7 ± 3.36 vs. Con. 49.7 ± 3.33 Mg C ha−1) were higher on organic farms compared to conventional farms. The dominant shade tree species on both organic (15 spp.) and conventional (15 spp.) stored more than 70 % of vegetation carbon stocks on both farm types. The estimated monetary value of the rate of CO2 equivalent of stored carbon by organic cocoa systems ranged from 74.58 US$ ha−1 yr−1 in old farms to 208.07 US$ ha−1 yr−1 in young farms compared to a range of 39.08 US$ ha−1 yr−1 in old farms to 99.60 US$ ha−1 yr−1 in young farms on conventional cocoa farms. The results show that organic cocoa agroforestry systems in our study area hold a greater potential to accumulate carbon and in addition benefit from carbon schemes than conventional cocoa agroforestry systems. Organic farms had higher shade tree diversity and richness which reflected the willingness of organic farmers to maintain/plant agroforestry trees. This indicate organic cocoa agroforestry system can help retain important ecosystem services within the cocoa production areas while providing some additional income to small holder cocoa farmers.

Farmer influence on shade tree diversity in rustic plots of Coffea canephora in Panama coffee-agroforestry

Coffee-agroforestry includes biodiversity conservation in tropical regions. The least economically valuable yet widely cultivated “robusta” coffee was studied in Panama, considering management practices and tree diversity. Fifty households were interviewed and a detailed tree census was conducted in 29 coffee plots owned by 13 households. Besides C. canephora there were 638 stems of 90 species in 41 plant families. Coffee plantings ≤ 10 years of age had higher tree diversity. With different degrees of management and original forest conditions, the coffee-agroforestry landscape was not uniform. Local vegetation was partly conserved. Farmers did not focus directly on productivity but instead emphasized flexible use and management, with moderate labor input, under changing socio-economic circumstances. Such rustic management, with attitudes and actions not governed by immediate monetary benefit, influenced biodiversity and rural life.

Combining participatory games and backcasting to support collective scenario evaluation: an action research approach for sustainable agroforestry landscape management

The combined and interacting effects of land-use change, resource extraction and climate change threaten the sustainability of millions of mainly smallholder farms in tropical agroforested landscapes. In many of these landscapes, coordinated action among stakeholders at landscape level would help to address challenges such as pests and diseases, price crises and climate change. However, methods to facilitate the co-production of sustainable landscape management in such complex multi-stakeholder systems are currently largely lacking. In this paper, we present a novel approach to explore pathways for the sustainability transition of agroforestry systems. By combining participatory forecasting and backcasting approaches, based on serious games and future vision development, we explore relevant agroforestry management strategies for reaching sustainable future coffee-based agroforestry landscapes. We focused our research on the challenges faced in the main coffee-producing area in Nicaragua. Here, we organized five participatory game sessions to explore farmer decision-making processes, farming strategies and to develop new networks and stimulate social learning among farmers. In the associated backcasting workshop, the most influential game session participants joined technicians, researchers and municipality officials to collectively envision sustainable future landscape management. In all game sessions, farmers developed diversified coffee-based agroforested landscapes characterised by increased density and diversity of shade trees, for the purpose of income diversification as well as forest conservation. During the backcasting workshop, the participants identified policy instruments and community-based solutions for the transition to sustainable landscapes. Our participatory approach facilitated discussion on landscape planning among farmers and other stakeholders and allowed the outline of a pathway towards the collective envisioned future landscape. The combination of participatory forecasting and backcasting proved to be a helpful tool to support multi-stakeholder processes towards sustainable landscape management in this and other complex landscapes.

Plant community composition and functional characteristics define invasion and infestation of termites in cocoa agroforestry systems

The effects of farm management on non-native species and the structure and function of native communities and ecosystems on crop yield is poorly documented especially in the cocoa agroforestry systems of West Africa. We assessed termite damages, cocoa plantations structural characteristic and local farmer knowledge to refine the critical role of shade trees management on subterranean crops pests and the consequences on marketable yield in five cocoa agroforestry systems. Farmers recognized termites as the most damaging subterranean pests and clearly described the type of damages they cause on cocoa trees and seedlings. Complete shade removal or very heavy shade on very old cocoa trees were responsible of the invasion of termites with negative effect on marketable yield. Some tree species, specifically fruit tree species planted in high proportion or solely may act as termite attractants and reservoirs by facilitating the building of galleries on cocoa trees. Many plant parts from roots to pods are preferred by termites with higher incidence on stems (52%), roots (34%) and young branches (27%). Damages on plant parts varied significantly with shade management. We found that the relationship between yield and the infestation of termites was weak in unshaded systems and very strong under shaded systems. We also found that the sales of agroforestry products significantly contribute to offset yield loss due to termite infestations. We conclude that intermediate shaded cocoa agroforestry systems with a diversity of shade trees will limit the outbreaks of termites. The intermediate shaded systems provide agroforestry products that offset marketable yield loss due to termites with positive impacts on income and the sustainability of cocoa production.

Native coffee agroforestry in the Western Ghats of India maintains higher carbon storage and tree diversity compared to exotic agroforestry

The ongoing introduction of the exotic Grevillea robusta tree species into agroforestry systems (AFS) of the Indian Western Ghats could become a threat to both climate change mitigation and tree diversity conservation.Here, we quantified carbon (C) storage and shade tree diversity in native forests and coffee AFS under contrasted management (native versus exotic shade trees, Robusta versus Arabica systems) at 67 plots along a 3500 mm precipitation gradient in the Cauvery watershed, India.Despite a substantial reduction of shade tree cover in native AFS compared to forest (from 90% to 32% in the high precipitation area), native AFS and forests displayed high and comparable C stocks (max. 228 MgC ha−1 and 234 MgC ha-1, respectively) and tree diversity (max. 44 and 45 species, respectively). Both variables were negatively impacted by the introduction of G. robusta, especially in Robusta coffee systems (max. 158 MgC ha−1, 12 species).The current trend toward the introduction of G. robusta in coffee AFS of the study area (exotic agroforestry) negatively affects C storage and tree diversity, especially in Robusta coffee systems. Policy makers should take advantage of the carbon-tree diversity positive correlation found in the agroforestry landscape of the Western Ghats of India to promote conservation and climate change mitigation.

Simplification of shade tree diversity reduces nutrient cycling resilience in coffee agroforestry

Abstract Agroforestry systems are refuges for biodiversity and provide multiple ecosystem functions and services. Diverse multispecies shade tree canopies are increasingly replaced by monospecific shade, often dominated by non‐native tree species. The loss of tree diversity and the nature of the dominating tree can have strong implications for ecosystem functions, for example, nutrient cycling ultimately reducing crop production. To understand direct and indirect impacts of shade trees on nutrient cycling and crop production, we studied coffee agroforestry systems in India along a gradient from native multispecies canopies to Grevillea robusta (Proteaceae) ‐dominated canopy cover. We identified 25 agroforests, across a broad rainfall and management gradient and assessed litter quantity and quality, decomposition, nutrient release, soil fertility and coffee nutrient limitations. Increasing G. robusta dominance affected nutrient cycling predominantly by; (a) changing of litter phenology, (b) reducing phosphorus (P), potassium (K), magnesium (Mg), boron (B) and zinc (Zn) inputs via litterfall, decelerated litter decomposition and immobilization of P and Zn due to low‐quality litter, (c) reducing soil carbon (C) and micronutrients (especially sulphur (S), Mg and B). Coffee plants were deficient in several nutrients (nitrogen (N), calcium (Ca), manganese (Mn), Mg and S in organic and B in conventional management). (d) Overall G. robusta‐dominated agroforests were characterized by a reduction of P cycling due to low inputs, strong immobilization while decomposition and antagonistic effects on its release in litter mixtures with coffee. Synthesis and applications. The conversion of shade cover in coffee agroforestry systems from diverse tree canopies to canopies dominated by Grevillea robusta (Proteaceae) reduces the inputs and cycling of several micro‐ and macronutrients. Soil fertility is therefore expected to decline in Grevillea robusta‐dominated systems, with likely impacts on coffee production. These negative effects might increase under the longer dry periods projected by regional climate change scenarios due to the pronounced litter phenology of Grevillea robusta. Maintaining diverse shade canopies can more effectively sustain micro‐ and macronutrients in a more seasonal climate.

Opportunities for sustainable intensification of coffee agro-ecosystems along an altitudinal gradient on Mt. Elgon, Uganda

The viability of coffee farming in East Africa is endangered by multiple factors including climate change, population pressure, low yields, and coffee price volatility. Sustainable intensification (SI) through intercropping and/or agroforestry has been suggested to improve farmers’ livelihoods, facilitate adaptation of coffee production to climate change and contribute to biodiversity conservation.In order to understand how sustainable intensification through an ecosystem-based approach might offer opportunities to respond to changes in temperature and rainfall, we analyzed a variety of existing coffee agro-ecosystems that differ in vegetation structure, shade tree diversity, and socio-economic characteristics on Mt. Elgon, Uganda along an altitudinal gradient (1100–2100 m.a.s.l.). We (i) compared the performance of the agro-ecosystems regarding coffee yield and shade tree diversity, and (ii) analyzed determinants of adoption of each system. Three different coffee agro-ecosystems were identified: open canopy coffee system, coffee-banana intercropping, and coffee-tree systems, based on the vegetation structure of 144 coffee plots.The vegetation structure of the analyzed coffee systems varied along the altitudinal gradient. Banana density increased with increasing altitude, while shade tree density and diversity increased with decreasing altitude. Coffee yield also increased with increasing altitude, but this relationship varied with shade level. Coffee yields benefited from shade trees at low altitudes, while no yield differences among systems were observed at mid and high altitudes. Increasing water availability and reliance on on-farm food crops with increasing altitude were identified as the main determinants of the increasing intercropped banana densities. High temperatures and longer dry season in combination with reduced access to forest products at lower altitudes, appeared to be the main driver for increased adoption of coffee-tree systems. Furthermore, socio-economic status of farmers influenced the type of coffee system adopted; poor farmers preferred high intercropping (either with bananas and/or shade trees) to diversify income and reduce risks related to open systems, while wealthier farmers mainly owned open canopy coffee systems.Climate, farm and household size, and access to forests and markets, play a crucial role in determining what constellation of plot-level provisioning ecosystem services benefit farmers’ livelihoods on Mt. Elgon. Our findings reveal inherent trade-offs in socio-ecological conditions. Minimizing these is required for achieving the multiple objectives of livelihood improvement, sustainable intensification of coffee production, and biodiversity conservation.

Effects of shade tree cover and diversity on root system structure and dynamics in cacao agroforests: The role of root competition and space partitioning

To increase yield, cacao is planted increasingly in unshaded monocultures, replacing a more traditional cultivation under shade. We investigated how shade tree cover and species diversity affect the root system and its dynamics. In a replicated study in Sulawesi (Indonesia), we studied the fine and coarse root system down to 3 m soil depth in three modern and more traditional cacao cultivation systems: unshaded cacao monoculture (Cacao-mono), cacao under either the legume Gliricidia sepium (Cacao-Gliricidia), or a diverse (> 6 species) shade tree cover (Cacao-multi). We analysed the vertical distribution of fine, large and coarse roots as well as fine root production, turnover and morphology on the species level. Stand-level fine root biomass showed a doubling with increasing shade tree cover (from 206 to 432 g m−2), but a tendency for a decrease in cacao fine root biomass. The presence of Gliricidia roots seemed to shift the cacao fine roots to a more shallow distribution, while the presence of shade tree roots in the Cacao-multi systems caused a biomass reduction and relative downward shift of the cacao roots. The turnover of cacao fine roots was much higher in the Cacao-multi stands than in the other two cultivation systems, although stand-level root production remained unchanged across the three systems. According to the stable isotope signature, Gliricidia extracted water from deeper soil layers than cacao, while no soil water partitioning was observed in the Cacao-multi stands. Our data suggest that the cacao trees altered their fine root distribution patterns in response to root competition. Both interspecific competition and root system segregation seem to play an important role in cacao agroforests with different shade tree cover.

Does shade tree diversity increase soil fertility in cocoa plantations?

Abstract Complex agroforests have been promoted as a potential solutions to address trade-offs between environmental conservation efforts and the need for increased agricultural productivity for smallholder farmers in the tropics. However, the effects of tree diversification on soil fertility in tropical agroforests remain unclear. In this study, we examine whether tree diversification in cocoa plantations is associated with soil fertility benefits and can contribute to soil restoration after deforestation. We tested for positive associations between increasing tree species diversity and increased soil aggregation, soil nutrients and microbial communities across a diversity gradient ranging from cocoa monocultures to complex cocoa agroforests. Secondary forests and primary forests were used as reference ecosystems. Increase in tree diversity within cocoa plantations did not increase soil fertility parameters in topsoil layers or cocoa yields. Mean soil C contents were 8% lower, mean weight diameter of aggregates 48% lower and total bacterial biomass 35% lower in cocoa plantations than in primary and secondary forest systems, whereas soil P content was 22% higher. Across all land-use systems, microbial biomass was greater in sites with higher soil carbon contents and soil aggregation. This suggests soil function restoration in terms of microbial communities, soil C and aggregate stabilization in secondary forests. However, in cocoa plantations tree diversification alone may not be an effective solution to mitigate soil degradation after deforestation. Rather, preserving remaining forests or promoting farming approaches that allow for secondary forest regeneration (e.g. implementing forest strips and regular fallow rotations) might have a more substantial impact on soil health.

Shade tree diversity enhances coffee production and quality in agroforestry systems in the Western Ghats

Abstract Intensification of multispecies coffee agroforests reduces shade tree diversity with implications for tropical biodiversity. We investigated how tree biodiversity and its effects on coffee production and quality changes along a gradient of intensification (from diverse multispecies to Grevillea robusta dominated shade) across 25 Coffea canephora agroforests in Kodagu, India. Intensification causes a marked reduction in tree biodiversity (Shannon’s diversity: 2.74 to 0.29). Reduced tree diversity negatively affected both coffee production and quality (in terms of bean size), and increased incidences of pest attack, the coffee berry borer (Hypothenemus hampei). These results were consistent across a broad rainfall gradient (1060 mm yr−1 to 4370 mm yr−1) and management systems (conventional vs. organic farming and irrigation). Our results reveal important co-benefits of multispecies agroforestry systems for biodiversity conservation and coffee production. Nonetheless, intensification provides farmers with new livelihood options and income sources. To maintain high diversity agroforests, these opportunity costs need to be accounted for in developing realistic market strategies for biodiversity conservation.

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.

Agroforestry coffee production increased by native shade trees, irrigation, and liming

Agroforestry systems usually include a high density and diversity of shade trees. Such systems often have a large diversity of fauna and flora and provide local and regional ecosystem services. Shade trees are, however, being removed to increase crop production in many tropical regions. There is little knowledge on the effect of shade trees on crop production in the context of trade-offs with other management practices. We therefore compared the benefits of exotic versus native shade trees on coffee production. We evaluated the importance of shade tree management for crop production in the context of management practices. Management practices included fertilization, liming, coffee pruning, weeding, and irrigation in 113 coffee agroforests in Kodagu, India, over a wide range of shade tree density, tree species diversity, and shade cover. We studied, in particular, Grevillea and non-Grevillea shade trees, the latter including mostly native tree species. Results show that a rise of 100 non-Grevillea shade tree per hectare increased production of berries by 5.6 % and larger beans by 6.25 %. Irrigation and liming increased berry production respectively by 16 and 20 %. These management interventions are likely to offset the relatively small negative effect of reducing shade density of non-Grevillea trees on coffee production. Recommendations based on an understanding of shade tree management alone can be misleading with regard to crop production.