Trees In Agroforestry Systems Research Articles

Pests and diseases on Falcataria moluccana trees in agroforestry systems with pineapple in East Java, Indonesia

Abstract. Rahayu S, Triyogo A, Widyastuti SM, Musyafa’, Ardianyah F. 2021. Pests and diseases on Falcataria moluccana trees in agroforestry systems with pineapple in East Java, Indonesia. Biodiversitas 22: 2779-2788. The agroforestry system using Falcataria moluccana (Sengon) and Ananas comosus (pineapple) is considered as a profitable intercropping system in Indonesia. To make it viable, it is necessary to evaluate the effect of mixed cropping on the incidence and severity of diseases and pests on Sengon trees and apply management measures. The present study was conducted (i) to assess the pest and disease problems on Sengon trees in the agroforestry system and (ii) to identify the most harmful pathogen/pest which affects the growth and causes mortality of Sengon trees at the beginning of intercropping and after the removal of pineapple from the system. Incidence of pests and diseases were assessed in 3 replicate blocks with one-year-old Sengon trees mixed with pineapple, and in another 3 plots with four-year-old Sengon trees from where pineapple was removed after harvesting. Sengon and pineapple were planted in the plots using alley cropping method with 3 x 4 m2 spacing. The results showed that there were no significant pest and disease problems on pineapple. However, Sengon was infested by the white grub Lepidiota stigma, gall rust caused by the fungus Uromycladium falcatarium, the stem borer Xystrocera festiva, and mistletoe Scurrula sp. However, stem borer and gall rust were the only pest and disease issues recorded in the monocultures of Sengon in Indonesia. The occurrence of stem borer and gall rust disease had a significant effect on the diameter growth of trees and in some instances, these caused mortality of one-year-old trees. Significant mortality of four-year-old trees was caused by mistletoe infestation only. Although the incidence of gall rust and stem borer in the agroforestry system was not significantly low compared to the monoculture, the former had wider spacing between trees, more open canopy and resultant low humidity and faster wind speed reduced the severity of the gall rust disease and stem borer attack. However, the intercropping resulted in the white grub attack on young Sengon trees which calls for application of contaminant-free fertilizers in pineapple plantings.

Modelling and Comparing Shading Effects of 3D Tree Structures with Virtual Leaves

Reduced solar radiation brought about by trees on agricultural land can both positively and negatively affect crop growth. For a better understanding of this issue, we aim for an improved simulation of the shade cast by trees in agroforestry systems and a precise estimation of insolation reduction. We present a leaf creation algorithm to generate realistic leaves to be placed upon quantitative structure models (QSMs) of real trees. Further, we couple it with an enhanced approach of a 3D model capable of quantifying shading effects of a tree, at a high temporal and spatial resolution. Hence, 3D data derived from wild cherry trees (Prunus avium L.) generated by terrestrial laser scanner technology formed a basis for the tree reconstruction, and served as leaf-off mode. Two leaf-on modes were simulated: realistic leaves, fed with leaf data from wild cherry trees; and ellipsoidal leaves, having ellipsoids as leaf-replacement. For comparison, we assessed the shading effects using hemispherical photography as an alternative method. Results showed that insolation reduction was higher using realistic leaves, and that the shaded area was greater in size than with the ellipsoidal leaves or leaf-off conditions. All shading effects were similarly distributed on the ground, with the exception of those derived through hemispherical photography, which were greater in size, but with less insolation reduction than realistic leaves. The main achievements of this study are: the enhancement of the leaf-on mode for QSMs with realistic leaves, the updates of the shadow model, and the comparison of shading effects. We provide evidence that the inclusion of realistic leaves with precise 3D data might be fundamental to accurately model the shading effects of trees.

Fruit and seed biometry of Carpotroche brasiliensis (RB) A. Gray (Achariaceae), a tropical tree with great potential to provide natural forest products

Carpotroche brasiliensis (RB) A. Gray (Achariaceae) is a native tree species of the Brazilian Atlantic Forest with great potential provide natural forest products in agroforestry systems. The oil of its seeds contains medicinal and cosmetic properties, and the fruits are appreciated by wild animals. In this study, we analyzed the biometry of fruits and seeds collected from naturally-grown trees in agroforestry systems on small farms in southern Bahia, Brazil. Fresh fruit mass (FFM), fruit length (FL), fruit diameter (FD), number of seeds per fruit (NSF), total fresh seed mass per fruit (FSMF), total dry mass of seeds per fruit (DMSF), and mass of 1,000 seeds (MTS) were collected from 66 fruits of 18 trees on six rural properties. Seed length (SL) and seed diameter (SD) were also evaluated for 5335 seeds. From this sample universe, 697 seeds represented an adequate sample size to measure these dimensions with statistical precision. The fruits analyzed in this study had uniform values for most of the biometric variables among the sites. The average values of NSF, FFM, and MTS were approximately 88 seeds, 0.5 kg, and 1.3 kg, respectively. Seeds of C. brasiliensis obtained from freshly-harvested fruits had high water content, with an average of more than 45%. Strongly significant correlations between FFM and FD and between FMSF and DMSF indicate the possibility of developing simple procedures to estimate seed pro-duction for commercial purposes from field evaluations

Tree longevity drives conservation value of shade coffee farms for vascular epiphytes

Forest loss and fragmentation threaten the high diversity of tropical forests. Tropical epiphytes are a key component of plant diversity and significant for ecosystem functioning, and they are vulnerable to these forces. We explored the potential of shade trees in agroforestry systems to sustain and restore epiphyte communities where forest cover has been lost. We investigated epiphyte colonization patterns using surveys of 748 trees within 87 variously-aged plots in coffee agroecosystems in northern Nicaragua. Species richness increased with stand age, reflecting effects of area, time, and the niche differentiation possible within larger trees. Young trees near mature trees were almost five times more likely to support epiphytes than those surrounded by other young trees, suggesting that propagule sources severely limit colonization in young, even-aged stands. We identified three stages of epiphyte colonization: an initial stage where trees lack epiphytes; a colonization stage where epiphyte abundance increases slowly; and a mature stage where accumulation accelerates as trees become large enough to support distinct microhabitats. Atmospheric bromeliads and several fern species with traits that facilitate dispersal, colonization, and persistence under open, sunny environmental conditions colonized young trees first. Thus, both environmental filtering and dispersal limitation drive community assembly in these agroforests. Because epiphytes colonize gradually, consistent land tenure and long-term management allow time for newly planted trees in shade coffee farms to develop to the size and structural complexity needed to support diverse epiphyte communities. Because ideal conditions for epiphytes may be at odds with managing for maximum coffee yields and some epiphyte species may never colonize coffee farms, even mature shade trees in coffee plantations cannot replace protecting native forests.

Conversion of monoculture cropland and open grassland to agroforestry alters the abundance of soil bacteria, fungi and soil-N-cycling genes.

Integration of trees in agroforestry systems can increase the system sustainability compared to monocultures. The resulting increase in system complexity is likely to affect soil-N cycling by altering soil microbial community structure and functions. Our study aimed to assess the abundance of genes encoding enzymes involved in soil-N cycling in paired monoculture and agroforestry cropland in a Phaeozem soil, and paired open grassland and agroforestry grassland in Histosol and Anthrosol soils. The soil fungi-to-bacteria ratio was greater in the tree row than in the crop or grass rows of the monoculture cropland and open grassland in all soil types, possibly due to increased input of tree residues and the absence of tillage in the Phaeozem (cropland) soil. In the Phaeozem (cropland) soil, gene abundances of amoA indicated a niche differentiation between archaeal and bacterial ammonia oxidizers that distinctly separated the influence of the tree row from the crop row and monoculture system. Abundances of nitrate (napA and narG), nitrite (nirK and nirS) and nitrous oxide reductase genes (nosZ clade I) were largely influenced by soil type rather than management system. The soil types’ effects were associated with their differences in soil organic C, total N and pH. Our findings show that in temperate regions, conversion of monoculture cropland and open grassland to agroforestry systems can alter the abundance of soil bacteria and fungi and soil-N-cycling genes, particularly genes involved in ammonium oxidation.

Carbon Stock of Indigenous Agroforestry Practices in Dellomenna District Southeast Ethiopia: Implication for Climate Change Mitigation

Trees in agroforestry systems are potential sinks of atmospheric carbon (C) due to their fast growth, productivity, high and long-term biomass C stock. Soil under forest and agroforestry also plays a major role in global C sequestration. This study was initiated to assess woody species and soil C sequestration of traditional agroforestry practices. Three study sites (namely: Buriketu, Chire and Erba) were systematically selected based on the presence of traditional agroforestry practices. Forty eight sample quadrats (16 quadrats in each site) having an area of 20m x 20m (400 m 2 ) were used for vegetation biomass estimation. Soil organic carbon (SOC) was sampled by using “X” design at depths of 0-30cm within each quadrats. Woody species biomass carbon stocks were estimated using an allometry equation of Y (Kg) = 34.4703 - 8.0671 DBH + 0.6589 DBH 2 . The types of agroforestry practices found in the study area are scattered trees in farm lands (parkland agroforestry), homegarden and live fence system. The mean AGBC stock showed an increasing trend from DBH ≥ 5 cm to 71 cm while a decreasing trend was noticed greater than 71 cm diameter classes. The mean carbon stocks (Means±Std) of different carbon pools in the indigenous agroforestry practice were 47.82±10.09, 11.96±2.52, 59.77±12.61, 150.61±6.9, 210.39±14.1 for AGBC stock, BGBC stock, TBC stock, SOC and TCSD, respectively. CO 2 assimilation by total biomass of woody species ≥ 5cm DBH in traditional agroforestry practices was estimated to be 219.15ton/ha. Estimation of CO 2 sequestration indicated that indigenous agroforestry practices of the area have been sequestered (772.02 ton/ha). The results of the present study confirmed that indigenous agroforestry practice play a major role in climate change mitigation. This study was focused on the biomass carbon stock of woody species ≥5 cm DBH, however, woody species <5cm DBH, dead wood, dead standing trees, fallen branches and litter-fine woody debris were also have a potential for C stock, thus further study on these components is recommended to provide reliable information. Keywords Biomass carbon, Ecosystem services , Global warming, Soil organic carbon. DOI : 10.7176/JEES/9-5-03 Publication date :May 31 st 2019

Carbon Stock of Indigenous Agroforestry Practices in Dellomenna District Southeast Ethiopia: Implication for Climate Change Mitigation

Trees in agroforestry systems are potential sinks of atmospheric carbon (C) due to their fast growth, productivity, high and long-term biomass C stock. Soil under forest and agroforestry also plays a major role in global C sequestration. This study was initiated to assess woody species and soil C sequestration of traditional agroforestry practices. Three study sites (namely: Buriketu, Chire and Erba) were systematically selected based on the presence of traditional agroforestry practices. Forty eight sample quadrats (16 quadrats in each site) having an area of 20m x 20m (400 m 2 ) were used for vegetation biomass estimation. Soil organic carbon (SOC) was sampled by using “X” design at depths of 0-30cm within each quadrats. Woody species biomass carbon stocks were estimated using an allometry equation of Y (Kg) = 34.4703 - 8.0671 DBH + 0.6589 DBH 2 . The types of agroforestry practices found in the study area are scattered trees in farm lands (parkland agroforestry), homegarden and live fence system. The mean AGBC stock showed an increasing trend from DBH ≥ 5 cm to 71 cm while a decreasing trend was noticed greater than 71 cm diameter classes. The mean carbon stocks (Means±Std) of different carbon pools in the indigenous agroforestry practice were 47.82±10.09, 11.96±2.52, 59.77±12.61, 150.61±6.9, 210.39±14.1 for AGBC stock, BGBC stock, TBC stock, SOC and TCSD, respectively. CO 2 assimilation by total biomass of woody species ≥ 5cm DBH in traditional agroforestry practices was estimated to be 219.15ton/ha. Estimation of CO 2 sequestration indicated that indigenous agroforestry practices of the area have been sequestered (772.02 ton/ha). The results of the present study confirmed that indigenous agroforestry practice play a major role in climate change mitigation. This study was focused on the biomass carbon stock of woody species ≥5 cm DBH, however, woody species <5cm DBH, dead wood, dead standing trees, fallen branches and litter-fine woody debris were also have a potential for C stock, thus further study on these components is recommended to provide reliable information. Keywords Biomass carbon, Ecosystem services , Global warming, Soil organic carbon. DOI : 10.7176/JRDM/54-01 Publication date : April 30 th 2019

Views and Attitudes of Local Farmers towards Planting, Growing and Managing Trees in Agroforestry System in Basona Worena District, Ethiopia

Agroforestry is a dynamic ecological-based natural resources management practice that integrates food crops, trees, and livestock in an agricultural landscape where the components may have ecological, economical, and social impacts. This study aimed at examining the views and attitudes of local farmers towards ‘planting, growing, and managing trees in agroforestry system’ in Basona Worena District, Ethiopia. As there was already a traditional agroforestry adopted by the farmers, the study kebele was purposely selected. A structured questionnaire was developed by accounting different socioeconomic variables. A total of 94 respondents were randomly contacted to collect the questionnaire data. Multiple linear regression technique was employed to analyze and interpret the data. Contrary to expectation, the findings showed that a greater proportion (about 60%) of the respondents did not practice agroforestry. However, those farmers who used to practice traditional agroforestry mainly exercised it to meet their household wood demands. Based on their economic values, the most commonly preferred tree species planted and grown by the farmers in descending order, included eucalyptus species, Acacia abyssinica, Croton macrostachyus, Sesbania sesban, Cupressus lusitanica, and Olea africana. The results also suggested that the farmers had conscious perceptions to determine the negative and positive effects of tree species on food crops, soils, and water. Generally, a greater proportion of the farmers strongly agreed (73.33%) that they had developed positive attitudes towards ‘planting, growing, and managing trees in agroforestry system’. Moreover, the multiple linear regression models showed that different socioeconomic variables significantly influenced the attitudes of farmers towards ‘planting, growing, and managing trees in agroforestry system’. Generally, the regression model explained about 36% of the variance in attitudes of the respondents towards ‘planting, growing, and managing trees’. Hence, providing improved agroforestry extension services, including incentives (e.g., seeds, tree seedlings, technical supports, and credits) may help increase the active participation of the farmers to adopt plant, grow, and manage trees in agroforestry system. Moreover, provision of adequate technical trainings on agroforestry technologies and establishing demonstration site is indispensable to increase the awareness level of the local farmers and thereby promote the adoption of agroforestry technologies in Basona Worena District and elsewhere.

Changes in soil carbon stocks across the Forest-Agroforest-Agriculture/Pasture continuum in various agroecological regions: A meta-analysis

The contribution of agroforestry systems (AFS) to enhance soil organic carbon (SOC) storage in soil layers due to the presence of deep tree roots are of interest in the context of promoting carbon sinks and greenhouse gas mitigation. To quantify the relative soil C contribution from trees in agroforestry systems (AFS), this study assessed the reported differences in SOC stocks under agroforestry systems in comparison with other land-use systems (Agriculture, Forestry, Pasture, or Uncultivated Land) in various soil-depth classes in four agroecological regions (arid and semiarid, ASA; lowland humid tropics, LHT; Mediterranean, MED; and temperate, TEM) around the world. Using mixed-effect models and a meta-analytical approach, we synthesized data from 78 peer-reviewed studies that generated 858 data points (sites) on SOC stock under various AFS practiced globally. Comparing Agroforest vs. Agriculture or Agroforest vs. Pasture, SOC stocks under AFS were higher by +27% in the ASA region, +26% in LHT, and +5.8% in TEM, but –5.3% in the TEM in the 0–100 cm soil depth. The Agroforest aged between 10–20 years had higher SOC stock than newly established, as well as <10-year-old systems across all soil-depth classes and agroecological regions. Overall, Agroforest vs. Agriculture land management practices resulted in positive SOC stock changes within AFS up to 100 cm soil depth, whereas SOC stock under AFS was lower than under Forest. The results suggest that a general pattern of Forest – Agroforest – Agriculture – Pasture continuum could be expected in SOC stock decline during land-use changes. Improvement of SOC stocks under AFS varied across agroecological regions, the highest being under arid and semiarid region, closely followed by the low humid tropics. The important outcome of this meta-analysis is worthy of emphasizing of the role of AFS in climate change adaptation and greenhouse gas mitigation strategies by promoting carbon sinks.

Extreme natural drought enhances interspecific facilitation in semiarid agroforestry systems

Agroforestry is a widely advocated adaptation strategy for enhancing agricultural resilience to extreme climates. However, it is somewhat controversial and there is limited evidence regarding its efficacy in semiarid regions. Here we describe studies on jujube agroforestry regimes using two different cash crops: the annual fodder species rape (Brassica napus) and the perennial daylily (Hemerocallis fulva). The jujube agroforestry systems were characterized with respect to their interspecific water interactions and their responses to extreme natural drought using stable isotopic techniques and in situ soil water observations in China’s semiarid Loess Plateau region. We found that agroforestry altered the jujube trees’ water sources but its impact depended on soil wetness: compared to monocultures, jujube trees in agroforestry systems generally shifted to deeper water under dry conditions but to shallower water under wet conditions. Complementary water use between jujube trees and crops was observed on most sampling dates, but there was clear evidence of water competition in the shallow layer under relatively wet conditions. Furthermore, a simple index, Relative Difference in Soil Water content (RDSW), was developed to indicate interspecific water interactions under various wetness conditions. It was found that facilitative interspecific interactions were clearly enhanced in both agroforestry systems during extreme drought. In addition, jujube yields in agroforestry systems were clearly higher than in monoculture. These findings demonstrate that agroforestry is a climate-smart agricultural system and can increase the resilience of semiarid jujube plantations to extreme real-world drought.

Shade trees and tree pruning alter throughfall and microclimate in cocoa (Theobroma cacao L.) production systems

Shade trees in agroforestry systems protect the understory cocoa from climate extremes. Shade tree pruning manages microclimatic conditions in favor of cocoa production while tree diversity is maintained. Adaptation of pruning has to consider seasonal changes in temperature and precipitation to protect the understory cocoa. Structural characteristics of tree stands such as species diversity, tree density, and stratification can affect throughfall and microclimate. Pruning changes the canopy and may therefore modulate internal conditions. The aim of this study is to assess the environmental growing conditions of cocoa trees. We monitored canopy openness and the impact of stand structure on throughfall and microclimate in three cocoa production systems (monoculture, agroforestry, and successional agroforestry) and a natural regrowth in a long-term trial in Bolivia from 2013 to 2015. We further focused on the effect of annual shade tree and cocoa pruning on these variables to evaluate the potential impact of this activity. Agroforestry systems buffered extreme climate events like temperature fluctuations compared to monocultures but reduced light and throughfall drastically. Spatial variability of throughfall and transmitted light were low under a high and closed shade tree canopy. Shade tree pruning resulted in higher canopy openness, light transmittance, and throughfall, while the buffer function of the agroforestry systems concerning temperature and humidity fluctuations was reduced. Differences between cocoa production systems regarding throughfall and microclimate were overlain by pruning activities. Cocoa agroforestry systems are temporal dynamic systems. Pruning timing and intensity is pivotal for balancing light and water availability under seasonally varying environmental conditions to conserve micro-environments for cocoa production with less exposure to unfavorable climate.

Local tree knowledge can fast-track agroforestry recommendations for coffee smallholders along a climate gradient in Mount Elgon, Uganda

Arabica coffee (Coffea arabica) is economically important for many smallholder farmers in the Mount Elgon region of East Uganda, but its production is increasingly threatened by climate change. However, ecosystem services (ES) provided by companion trees in coffee agroforestry systems (AFS) can help farmers adapt to climate change. The objectives of this research were to develop agroforestry species recommendations and tailor these to the farmers’ needs and local context, taking into consideration gender. Local knowledge of agroforestry species and ES preferences was collected through farmer interviews and rankings. Using the Bradley-Terry approach, analysis was done along an altitudinal gradient in order to study different climate change scenarios for coffee suitability. Farmers had different needs in terms of ES and tree species at different altitudes, e.g. at low altitude they need a relatively larger set of ES to sustain their coffee production and livelihood. Local knowledge is found to be gender blind as no differences were observed in the rankings of species and ES by men and women. Ranking species by ES and ranking ES by preference is a useful method to help scientists and extension agents to use local knowledge for the development of recommendations on companion trees in AFS for smallholder farmers.

Agroforestry and Management of Trees in Bunya County, Mayuge District, Uganda

Woody plant resources continue to disappear in anthropogenic landscapes in Uganda. To slow down further loss of these resources requires the collaboration of farmers in tree planting in agroforestry systems. Tree planting interventions with the collaboration of farmers require a good understanding of tree management practices as well as trees that best satisfy farmers’ needs. We carried out this research to determine (1) the most preferred tree species and reasons why they are preferred, (2) the species conservation statuses, and (3) existing tree management practices and challenges to tree planting. Fourteen priority species valued because they yield edible fruits and timber have been prioritised in this study. Farmers are interested in managing trees but are constrained by many factors, key among which is scarcity of land and financial capital to manage tree planting. Trees are managed in crop fields and around the homestead. From farmers’ reports, the highly valued species are increasing in the landscape. In conclusion, the potential to manage trees in agroforestry systems exists but is hampered by many challenges. Secondly, the liking of trees that supply edible fruits seems to support the welfare maximisation theory which ideally states that rural people manage trees with the aim of having regular access to products that satisfy their household needs and not for income generation.

Density responses and spatial distribution of cotton yield and yield components in jujube (Zizyphus jujube)/cotton (Gossypium hirsutum) agroforestry

Abstract Trees are the dominant species in agroforestry systems, profoundly affecting the performance of understory crops. Proximity to trees is a key factor in crop performance, but rather little information is available on the spatial distribution of yield and yield components of crop species under the influence of trees in agroforestry systems. Also, little information is available on how crop density may be exploited to optimize the yield in such systems. Here we studied the performance of cotton in jujube/cotton agroforestry. Field experiments were conducted in 2012 and 2013 in Hetian, Xinjiang, China. Cotton was grown at a row distance of 60 cm in three densities, 13.5, 18.0 and 22.5 plants m−2 in six m wide paths between tree lines in a jujube plantation. Plant density affected both cotton aboveground dry matter and yield significantly. The highest yield was attained at the intermediate density of 18.0 plants m−2 (20.0 plants m−2 corresponding in sole cotton), lower than the optimal density in sole cotton (25.0 plants m−2). Yield at the lower density was constrained by the low number of bolls per m2 as a direct consequence of the low density, whereas at the high plant density yield was constrained by a lower allocation of assimilates to cotton seed and lint, as a consequence of intraspecific and interspecific competitions. There were strong gradients in yield and yield components in relation to the distance from the tree rows. Leaf area and total dry matter of cotton in rows close to the tree lines were reduced, especially in the rows next to the trees. Moreover, biomass allocation to cotton fruits was reduced in these rows. Competitive influences from the trees on cotton performance extended two rows deep in a six-year old jujube stand, and even three rows deep in a seven-year old stand. Shading effects on cotton yield were compensated by increasing plant density as a result of greater boll numbers per unit ground area. Data from this study help guide the design of optimal plant density of cotton in jujube plantations and give insight in the spatial distribution and dynamics of competitive effects in agroforestry systems in general.

Determinants of bacterial communities in Canadian agroforestry systems.

Land-use change is one of the most important factors influencing soil microbial communities, which play a pivotal role in most biogeochemical and ecological processes. Using agroforestry systems as a model, this study examined the effects of land uses and edaphic properties on bacterial communities in three agroforestry types covering a 270 km soil-climate gradient in Alberta, Canada. Our results demonstrate that land-use patterns exert stronger effects on soil bacterial communities than soil zones in these agroforestry systems. Plots with trees in agroforestry systems promoted greater bacterial abundance and to some extent species richness, which was associated with more nutrient-rich soil resources. While Acidobacteria, Actinobacteria and Alphaproteobacteria were the dominant bacterial phyla and subphyla across land uses, Arthrobacter, Acidobacteria_Gp16, Burkholderia, Rhodanobacter and Rhizobium were the keystone taxa in these agroforestry systems. Soil pH and carbon contents emerged as the major determinants of bacterial community characteristics. We found non-random co-occurrence and modular patterns of soil bacterial communities, and these patterns were controlled by edaphic factors and not their taxonomy. Overall, this study highlights the drivers and co-occurrence patterns of soil microbial communities in agroforestry systems.

Agroforestry systems of the lowland alluvial valleys of the Tehuacán-Cuicatlán Biosphere Reserve: an evaluation of their biocultural capacity

BackgroundAgroforestry systems (AFS) are valuable production systems that allow concealing benefits provision with conservation of biodiversity and ecosystem services. We analysed AFS of the zone of alluvial valleys of the Tehuacán-Cuicatlán Valley (TCV), Mexico, the most intensive agricultural systems within a region recognized for harbouring one of the most ancient agricultural experience of the New World. We hypothesized that the biodiversity conservation capacity of AFS would be directly related to traditional agricultural features and inversely related to management intensity.MethodsAgricultural practices, use frequency of machinery and chemical inputs, and proportion of forest and cultivated areas were described in 15 AFS plots in alluvial valleys of the Salado River in three villages of the region. With the information, we constructed a management intensity index and compared among plots and villages. We documented the reasons why people maintain wild plant species and traditional practices. Perennial plant species were sampled in vegetation of AFS (15 plots) and unmanaged forests (12 plots 500 m2) in order to compare richness, diversity and other ecological indicators in AFS and forest.ResultsIn all studied sites, people combine traditional and intensive agricultural practices. Main agroforestry practices are ground terraces and borders surrounding AFS plots where people maintain vegetation. According to people, the reasons for maintaining shrubs and trees in AFS were in order of importance are: Beauty and shade provision (14% of people), fruit provision (7%), protection against strong wind, and favouring water and soil retention. We recorded 66 species of trees and shrubs in the AFS studied, 81% of them being native species that represent 38% of the perennial plant species recorded in forests sampled. Land tenure and institutions vary among sites but not influenced the actions for maintaining the vegetation cover in AFS. Plant diversity decreased with increasing agricultural intensity.ConclusionsMaintenance of vegetation cover did not confront markedly with the intensive agricultural practices. It is possible the expansion and enrichment of vegetation in terraces and borders of AFS. Information available on plant species and local techniques is potentially useful for a regional program of biodiversity conservation considering AFS as keystones.

Does litterfall from native trees support rainfed agriculture? Analysis of Ficus trees in agroforestry systems of southern dry agroclimatic zone of Karnataka, southern India

Trees of the genus Ficus, integral components of indigenous rainfed agro-ecosystems of the southern dry agro-climatic zone of Karnataka, southern India, have traditionally been associated with the ecological service of soil quality enhancement in addition to various direct use benefits. We assessed the soil enrichment service of Ficus benghalensis L. a common Ficus species in these agroforestry systems, by quantifying nutrient return via litter fall. Litterfall estimation and chemical analysis of litter showed that F. benghalensis trees produce 3,512 kg·ha−1 of litter annually which, on decomposition, can satisfy up to 76.70 % of N, 20.24% of P and 67.76% of K requirements of dryland crops annually per hectare. This can lead to an avoided cost of compost of US $ 36.46 ha−1·a−1 in dryland farming systems. The slow rate of decay of Ficus litter, as revealed in litter decomposition studies indicates its potential as ideal mulch for dryland soils. We discuss the complementarity between Ficus litterfall and cropping patterns in Mandya, and its implications for rainfed agricultural systems.

Symbiotic dinitrogen fixation by trees: an underestimated resource in agroforestry systems?

We compiled quantitative estimates on symbiotic N2 fixation by trees in agroforestry systems (AFS) in order to evaluate the critical environmental and management factors that affect the benefit from N2 fixation to system N economy. The so-called “N2-fixing tree” is a tripartite symbiotic system composed of the plant, N2-fixing bacteria, and mycorrhizae-forming fungi. Almost 100 recognised rhizobial species associated with legumes do not form an evolutionary homologous clade and are functionally diverse. The global bacterial diversity is still unknown. Actinorrhizal symbioses in AFS remain almost unstudied. Dinitrogen fixation in AFS should be quantified using N isotopic methods or long-term system N balances. The general average ± standard deviation of tree dependency on N2 fixation (%Ndfa) in 38 cases using N isotopic analyses was 59 ± 16.6 %. Under humid and sub-humid conditions, the percentage was higher in young (69 ± 10.7 %) and periodically pruned trees (63 ± 11.8 %) than in free-growing trees (54 ± 11.7 %). High variability was observed in drylands (range 10–84 %) indicating need for careful species and provenance selection in these areas. Annual N2 fixation was the highest in improved fallow and protein bank systems, 300–650 kg [N] ha−1. General average for 16 very variable AFS was 246 kg [N] ha−1, which is enough for fulfilling crop N needs for sustained or increasing yield in low-input agriculture and reducing N-fertiliser use in large-scale agribusiness. Leaf litter and green mulch applications release N slowly to the soil and mostly benefit the crop through long-term soil improvement. Root and nodule turnover and N rhizodeposition from N2-fixing trees are sources of easily available N for the crop yet they have been largely ignored in agroforestry research. There is also increasing evidence on direct N transfer from N2-fixing trees to crops, e.g. via common mycelial networks of mycorrhizal fungi or absorption of tree root exudates by the crop. Research on the below-ground tree-crop-microbia interactions is needed for fully understanding and managing N2 fixation in AFS.

Seasonal changes in litter fall and its quality from three sub-tropical fruit tree species at Nelspruit, South Africa

Litter fall from upper storey trees in agroforestry systems contributes to nutrient cycling for the benefit of all components of the system besides serving as mulch. This study examined the seasonal changes in the quantity and quality of leaf litter fall from three sub-tropical fruit trees viz: avocado (Persea americana L.), mango (Mangifera indica L.) and litchi (Litchi chinensis L.) which have potential for use in agroforestry. Leaf litter production was estimated using nylon mesh litter traps erected over five randomly selected trees of each species in a completely randomised design. Litter quality was determined by analysing ash content and polyphenol, carbon, cellulose, lignin and nutrient concentrations over a 2 year period (2007–2008). Total annual leaf litter production during the study period (dry matter basis) was 8.3, 6.3 and 5.6 t ha−1 year−1 for litchi, mango and avocado, respectively. In both years, leaf litter fall was greatest during autumn and lowest during winter in all species. There were no significant differences in S, Ca, Mg and Mn concentrations in the leaf litter, but polyphenol, N, P and K concentrations differed significantly (P < 0.05) between species. It was concluded that litter quality from all three tree species was low and would require appropriate management to improve its quality.

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.