Effect Of Shade Trees Research Articles

Biological soil health indicators are sensitive to shade tree management in a young cacao (Theobroma cacao L.) production system

Cacao agroforestry systems can offer important benefits, such as greenhouse gas mitigation, microclimate regulation and improved soil health. The selection of tree species for cacao agroforestry systems is a critical step impacting cacao yields, as well as the environmental and economic sustainability of the production system. However, the effects of different tree species on soil processes and functions have been poorly studied. We assessed a series of soil health indicators in a five-year-old agroforestry trial located in the Ecuadorian Amazon. The following treatments: “control” (cacao monoculture), “timber” (cacao with Cedrelinga cateniformis Ducke; a leguminous tree), “fruit” (cacao with Bactris gasipaes), “N-fix” (cacao with Erythrina velutina Wild) and “mixed” (cacao with C. cateniformis + E. velutina) were replicated 3 times in randomized blocks. The experiment was managed organically with low levels of external inputs. We collected soil, litter and leaf samples of cacao trees at two different distances (∼2 m and ∼ 6 m) from the shade tree. Biological (potential soil respiration, and macrofauna abundance, richness and Shannon diversity), chemical (pH, CEC, total C and N, macro and micronutrients and Cd), and physical (bulk density and water holding capacity) soil health indicators were measured. Additionally, we analysed nutrients and Cd in cacao leaves and litter. Results showed positive effects of the “timber” and “mixed” treatments on biological soil health indicators, primarily earthworm abundance and potential respiration, as compared to cacao monocultures. Treatment effects on potential respiration showed different trends in litter versus soil, indicating that effects of shade trees on litter respiration do not transfer directly to soil respiration. Physical and chemical soil indicators, including available Cd which is irrelevant in the context of food safety regulations, did not show any differences among the treatments. Five years after establishment, no significant differences in yields were found among the control and any of the shade tree treatments.

Farmers’ Perception of Coffee Agroforestry Systems in an Area Targeted for Organic Certification in Burundi

Taking into account the current understanding of a system by farmers is an important starting point in every project aiming at the economic and social development of human beings. In the process of organic certification of coffee growers, training sessions on various topics are conducted. In addition to these sessions, there are field visits to farms by experts. And it is most often done through a top-down approach. A household survey was carried out on a purposive sample of households in the zone of the central plateaus in Burundi. Data were collected using a questionnaire through smartphones. Data analysis was carried out using IBM SPSS Statistics software by calculating means, frequencies and cross-analyses of variables. Results show that, besides bananas that are deliberately considered as shading crops, Grevillea robusta is the most frequent shade tree which is present on 62% of coffee plots. It is followed by an indigenous tree: Ficus sp. which is present on 14.6% of plots, and a fruit tree, Persea americana present on 13.9% of plots. The effects of shade trees on soil properties are well recognized by farmers. For their search of certification (75% of farmers are involved in the process of organic certification), chemicals application is banned. Farmers use a locally-made biopesticide decoction. They prepare it from a set of five plants: Tephrosia vogelii, Solanum aculeastrum, Neorautanenia mitis, Capsicum frutescens, and Tithonia diversifolia. This research has proven that the integration of shade trees in coffee plots is a reality in the region.

Dispersion patterns and monitoring samplings of termite pests in cocoa agroforestry systems of Southern Cameroon

Termites are major emerging pests of cocoa in Africa. However, their dispersion models on cocoa trees as well as their sampling plans remain unclear. Moreover, the effect of shade trees on the severity of termite infestation on cocoa is poorly known. We evaluated the severity of termite infestation on cocoa trees in relation to shade management in five cocoa agroforestry systems in southern Cameroon with shade cover ranging from rustic to full sun. The dispersion models of termites on cocoa were analyzed using Taylor’s power law, Nachman model and Iwao’s method. We then simulated the optimal sampling sizes for pest monitoring based on parameters of the best-fitted dispersion model using Southwood’s and Green’s formulas. Our results suggest that shade trees reduce belowground infestation by termites and encourage aboveground infestation; however, belowground infestation is more severe. Taylor’s power law was the best-fitted model to describe the aggregative dispersion pattern of termites on cocoa trees. The estimated sampling plans suggested that Green’s sampling was more precise for termites sampling, where less trees is required, than Southwood’s sampling. This study is pioneer on dispersion patterns and sampling plans of termites on cocoa and could be used by researchers and farmers for decision making about pesticide application.

Effects of shade trees on robusta coffee growth, yield and quality. A meta-analysis

Productivity of coffee plantations is threatened by both climate change and decreasing revenues of coffee growers. Using shade trees might protect against temperature variability, erosion and excessive radiation but there may be trade-offs in productivity and quality. While impacts of shade trees on arabica (Coffea arabica) have been reviewed, a global synthesis on robusta (Coffea canephora) coffee is lacking. We assessed how shade affects robusta growth and productivity, and what are the interactions and trade-offs. We conducted a systematic literature search in Web of Science and CAB s on 16 December 2019. Thirty papers fulfilled our inclusion criteria of being experimental studies on the impact of overstory trees with approximately half being from Brazil or India. Shade improved robusta tree growth and yield with some contrasting effects on physicochemical and biochemical properties. Shade (> 30%) was associated with reduced beverage quality. Significant interactions between shade and location, rainfall level and robusta clone were found. Among the clones tested, 06V, C153, LB1, GG229 and JM2 showed a higher productivity and growth (from + 17 to + 280%) under moderate shade (41–65%). This is the first meta-analysis of the effects of shade on robusta coffee. By synthesizing data from different studies, we highlight for the first time that the effect of shade on robusta coffee depends on tree age. Shade had positive impacts on older robusta trees (mean of 16 years), while the impact of shade on younger trees was either insignificant or negative. We highlight the importance of both clone type and tree ages. Research gaps included a lack of knowledge on the effects of shade with respect to coffee and shade tree age as well as interactive effects. More in-depth studies are needed to understand the mechanisms of how shade trees affect robusta coffee.

The Effect of Shade Trees in the Coffee Ecosystem to the Population and Diurnal Activity of Insect Pollinators

Insect pollinators is one of the important factors in the cross-pollination of coffee flowers, which affects the coffee fruit set. However, there is still a limited understanding of how shade trees in the coffee ecosystem affect insect pollinators. The purpose of this study was to obtain information on the effect of climate variations at different shading levels in the coffee ecosystem to the population and diurnal activity of insect pollinators. The shade levels are categorized in three ways, namely high shade, low shade, and open shade. The observation was conducted at the time when the flower blooms with sample units a flower in two coffee branches. Insect pollinators that show feeding behavior in coffee flowers were recorded in the morning, while the diurnal activity of each species pollinator was observed in the morning, midday, and afternoon. The study showed five species of insects belonging to three families and two orders, Hymenoptera and Lepidoptera that showed feeding behavior on coffee flowers. Apis cerana and Apis mellifera were the dominant pollinators of coffee flowers. The difference in shade levels did not affect pollinator species to visit coffee flowers, but their population tends to decrease in the open shade, except Apis cerana. The peak of diurnal activity of insect pollinator recorded in the morning decreased at midday and showed an increase slightly in the afternoon until the end of the diurnal activity. An increase of temperature may significantly decrease the number of pollinators that visit coffee flowers, while humidity and light intensity showed no significant effect.

A comparison of coffee floral traits under two different agricultural practices

Floral traits and rewards are important in mediating interactions between plants and pollinators. Agricultural management practices can affect abiotic factors known to influence floral traits; however, our understanding of the links between agricultural practices and floral trait expression is still poorly understood. Variation in floral morphological, nectar, and pollen traits of two important agricultural species, Coffea arabica and C. canephora, was assessed under different agricultural practices (sun and shade). Corolla diameter and corolla tube length were larger and pollen total nitrogen content greater in shade plantations of C. canephora than sun plantations. Corolla tube length and anther filament length were larger in shade plantations of C. arabica. No effect of agricultural practice was found on nectar volume, sugar or caffeine concentrations, or pollen production. Pollen total nitrogen content was lower in sun than shade plantations of C. canephora, but no difference was found between sun and shade for C. arabica. This study provides baseline data on the influence of agronomic practices on C. arabica and C. canephora floral traits and also helps fill a gap in knowledge about the effects of shade trees on floral traits, which can be pertinent to other agroforestry systems.

Cooling Effect of Urban Trees on the Built Environment of Contiguous United States

AbstractExacerbated heat stress has resulted in a series of environmental issues in urban areas. Mounting empirical evidence shows that urban trees are effective in mitigating the thermal stress in the built environment, whereas large‐scale numerical simulations remain scarce. In this study, the effects of shade trees on the built environment, in terms of radiative cooling, pedestrian thermal comfort, and urban land surface energy balance, were evaluated over the contiguous United States. The projected scenario was simulated using a coupled Weather Research and Forecasting‐urban modeling system, incorporating the radiative shading of urban trees only. Results show that on average the mean near‐surface air temperature in urban areas decreases by 3.06 °C over the entire contiguous United States with the shading effect. Analysis of pedestrian thermal comfort shows that shade trees improve the thermal comfort level in summers, but could be detrimental in winters for cities located in temperate or subpolar climate zones. In addition, it was found that trees alter the surface energy balance by primarily enhancing the radiative cooling, leading to significant changes in the sensible heat but the ground heat comparatively intact.

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.

Thermal Comfort Conditions in Outdoor Urban Spaces: Hot Dry Climate -Ghardaia- Algeria

One of the great challenges facing our generation of scientists is how to mitigate the effects of urban heat island. This problem become more and more important for the well being of man. The aim of this study is to enable designers to produce comfortable outdoor spaces. Many researchers believe that the causes of the microclimatic variation in cities are linked to urban geometry, and the effect of shade trees. The main aim of this paper is to discuss and assess the impact of the geometry and shade trees on the open spaces climate, in Ghardaia (hot dry climate) –Algeria.

Effect of shade tree planting and soil management on rehabilitation success of a 22-year-old degraded cocoa (Theobroma cacao L.) plantation

Since productivity of current cocoa plantations is stagnating or declining, increasing global demand for cocoa products puts pressure on tropical, primary forests to be cut for new plantations. To address this problem, sustainable increase of cocoa yield on current plantations is needed. On a 22-year-old, 61ha cocoa plantation in peninsular Malaysia, shade tree planting and soil management treatments, including targeted mineral fertilization, intense organic fertilization and combinations of these with compost application and cover crop (Centrosema pubescens) planting, were assessed as a rehabilitation strategy of degraded cocoa plantations with sub-optimum yield. Treatment effects on cocoa yield and on proxy indicators soil fauna abundance and diversity, and soil nutrient status, was tested 3.5 years after implementation in four harvesting rounds between 28 November 2014 and 12 March 2015. Across all treatments, large differences were found in the yield of the two clones tested (PBC130 and PBC123). The effect of shade trees (mainly Musa sp., with some permanent shade trees) on yield interacted with the factor ‘clone’. Mean wet bean yield of PBC123 trees in full-sun cultivation was 0.74kg as compared with 1.08kg for trees in the agroforestry system (46% increase). Mean wet bean yield of PBC130 trees, however, was 20% lower in the same agroforestry system (0.08kg) in comparison with mean wet bean yield of trees in full-sun cultivation (0.10kg). Soil management treatments did not result in clear yield improvement as compared with common-practice, control plots. However, cover crop treatment had a positive effect on proxy indicators soil nutrient status and endogeic soil fauna diversity. It is concluded that in the rehabilitation of degraded cocoa plantations, possible yield impact of applying a straightforward agroforestry system, as the one in our experiments, is high. Furthermore, it was shown that in a degraded plantation with a long history of intensive fertilization, improved soil management has little effect. Positive effects of shade trees on cocoa yield are therefore probably linked with the creation of an environment that improves cocoa crop physiology and reduces pressure of pests and diseases, rather than with the improvement of soil quality as a consequence of intercropping with trees.

Local knowledge of impacts of tree cover on ecosystem services in smallholder coffee production systems

The potential for tree components of coffee agroforestry systems to provide ecosystem services is widely recognized. Management practices are a key factor in the amount and quality of ecosystem services provided. There is relatively abundant information on ecosystem services provision within agroforestry systems, but comparatively scant information regarding how coffee farmers manage their plantations, the factors influencing their farming practices and the extent to which farmers’ local knowledge – as opposed to global scientific understanding – underpins management decisions. Policymakers and scientists too frequently design development programs and projects in the coffee sector. On occasion technicians are included in the design process, but farmers and their knowledge are always excluded. This research explores farmers’ knowledge regarding how trees affect coffee productivity and ecosystem services in Costa Rica. Farmers’ knowledge on the effects of trees on coffee productivity was compared with that of other knowledge sources: coffee processors, technicians and scientists. Farmers were shown to have detailed knowledge regarding ecosystem services that their coffee agroforestry systems provide as well as on the interactions between trees and coffee productivity. When asked on the services that trees provide, farmers classified trees according to water protection, soil formation, or contribution to biodiversity conservation. These classifications were related to tree attributes such as leaf size, biomass production or root abundance. Comparison of coffee productivity knowledge from different knowledge sources revealed considerable complementarity and little contradiction.The effects of shade trees on biophysical conditions and their interactions with coffee productivity were well understood by farmers. They recorded and classified shade trees as ‘fresh’ (suitable for integration with coffee) or ‘hot’ (unsuitable) based on their leaf texture and size, foliage density, crown shape, and root system attributes. The fresh/hot classification significantly related to positive/negative provision of services. This classification was widely used by farmers, and unknown by coffee technicians.Detailed local knowledge included several different topics, such as the role of trees in soil formation and in abundance of pollinators. Farmers were also aware of the influence of these ecosystem services on crop productivity. Generally, management decisions were made to maintain coffee productivity rather than ecosystem services. Based on these results, it is suggested that technical interventions addressing the improvement of coffee plantations are more likely to be successful if they take into account not only the scientific information on agroforestry interactions but also the knowledge possessed by farmers. Lack of comprehension of local coffee knowledge could be expected to reduce the success of development programs and projects aimed at improving productivity or other ecosystem services.

Effects of shade trees on Coffea Arabica pests and diseases

The coffee tree is a shade tolerant plant originating from Africa. Its cultivation however developed mainly apart from its zone of origin, particularly in Latin America, with intensive systems in full sun. With the extension of the zones of cultivation, certain traditional pests and diseases of the coffee tree, such as the coffee berry borer, also colonized new territories while others, such as the agent of the coffee berry disease Colletotrichum kahawae, remained on the continent of origin. During the extension of its zone of cultivation, the coffee tree encountered other pests and diseases which were already adapted to the new zones. The cultivation in full sun facilitates high production but requires more inputs, particularly pesticides. Today, the association of the coffee tree with shade trees in agroforestry systems is being studied from the point of view of greater crop and environmental sustainability. This paper presents an overview of the impact of shade trees on several important pests and diseases of the coffee tree. Various mechanisms, such as the barrier effect or the microclimate modification, will be discussed using examples. Lastly, recommendations will be proposed according to the pest and disease existing in the cultivation zones. The use of shade trees is particularly recommended in zones where the coffee berry disease prevails and agroforestry systems are especially recommended for use in these areas.

Effects of Shade Trees on Illuminance in Classrooms in the United Arab Emirates

This study investigated the potential of shade-trees to improve lighting conditions in the indoor space of a standard classroom in the United Arab Emirates (UAE) using computer simulation with the Radiance program. Shade trees are defined as selected suitable types of trees using certain criteria (i.e. evergreen, proper canopy density, proper height, growth in extreme hot climate conditions, safe roots) based on literature survey and consultation with landscape experts. It focuses on analysis of illuminance levels at desk locations (task) inside a standard classroom oriented to the North, East, South, and West for the selected critical times that are relevant to the locality. An initial group of simulation runs was done at the outset to choose proper tree spacing. The dependent variables are illuminance level and illuminance range resulted from manipulating two independent variables, shade tree type and orientation. The simulation runs includes a base case with no shade trees against other improvement cases with shade trees. The findings show the significance of the shade trees for improved lighting distribution and quality. This is evident in the reduction of illuminance ranges throughout the classroom as it is the case with the Neem shade trees at 2 m providing the lowest range from 125–570 Lux on front of the window and from 130–498 Lux on front of the wall. Yet, some reduction in the overall levels of illuminance is experienced (18–31% reduction for North orientation; 87–96% reduction for other orientations) and an increase in the estimated operating hours of electric lighting. Finally, some passive methods such as high strip windows and roof monitors were recommended to compensate for the illuminance reduction, rather than using electric lighting.

Limitation of coffee leaf photosynthesis by stomatal conductance and light availability under different shade levels

In agroforestry systems, the effect of shade trees on coffee net photosynthesis (A n) has been the object of debates among coffee scientists. In this study, we undertook over 600 coffee A n “spot” measurements under four different artificial shade levels (100, 72, 45 and 19% of full solar irradiance) and analyzed limitations to A n by low light availability (photon flux density, PFD) and stomatal conductance (g s). These gas exchange measurements were carried out during two consecutive coffee growing seasons in a commercial plantation in the Orosi valley of Costa Rica. Levels of A n were related to PFD and g s in order to calculate envelope functions which were used to establish PFD or g s limitations to A n. Under the growing conditions of the present trial, mean leaf A n remained stable for growth irradiance (GI) as low as 45% of full sun and decreased by ~20% at 19% GI. Limitation to A n due to g s was strong in full sun and decreasing with increasing shade levels. On the other hand, limitation due to PFD remained at a similar level for all shade treatments. These different evolutions of limitations of A n by PFD and g s in response to shade explain the absence of a decrease in coffee leaf A n with a shade level up to 55%. Consequently, these results confirm that Arabica coffee is a shade-adapted plant with leaves that can maintain a high photosynthetic performance under low light availability.

Effects of Tree Shade on Home Cooling Requirements

This study was implemented to provide more information on the effects of shade trees on summer cooling energy reduction. A sample of 113 homes of similar setting and design in College Station, Texas was used. Electrical data reduced to kilowatt hours per square foot of living area were used as the dependent variable. Shade proved to be the most significant of several variables observed in reducing electrical energy usage.

Effect of shade trees on tea yields

Planting of Grevillea robusta shade trees throughout tea gardens has been shown, under East African conditions, to cause a considerable reduction in yield of var. assamica tea, amounting overall to 10–15%; a single test indicated that tea quality was also adversely affected. Results were obtained by visual counts of bushes shaded during periods of bright sunshine and by separate plucking of plots of tea at different distances from mature shade trees in two areas of contrasting climate with 50 inches and 70 inches annual rainfall respectively. The reduction in yield from increasing shade was as great in rows near to the shade trees as in rows most distant from them.