Agroforestry Tree Species Research Articles

GENETIC VARIABILITY AND INTERRELATIONSHIP AMONG MORPHOLOGICAL TRAITS IN AFRICAN PEAR FRUIT (DACRYODES EDULIS (G.DON) H.J. LAM) ACCESSIONS

African pear fruit (Dacryodes edulis) is a highly sought for multipurpose agroforestry tree species that has the potential for both local and international trades, Nigeria is among the leading producer of the fruit, but its pattern and extent of its genetic variability is currently unknown. Hence, a study was carried out to determine the pattern and extent of genetic variability and interrelationships among 13 morphological traits of African pear fruit accessions. The experiment was laid in a Completely Randomized Design in 5 replications. Data collected on number of leaf production, leaf length, leaf breadth, leaf length/breadth ratio, internode distances, plant height, collar diameter, fresh leaf weight, fresh stem weight, fresh root weight, dry leaf weight, dry stem weight, dry root weight and biomass accumulation were subjected to Analysis of Variance. Treatment means were separated using Duncan’s Multiple Range Test at 5% probability level. Results showed significant (p<0.05) differences among the D. edulis genotypes for most of the traits evaluated indicated variation in the performance of the genotypes and pattern of clustering indicated that there was no association between eco-geographical distribution of genotypes and genetic diversity. PCA revealed that fourteen axes accounted for 100% of the variations observed while the first five axes contributed 73.23% of the total variation observed. The first axis accounted for 25.61% of the total variation while the second and third accounted for 15.43 and 15.01%, respectively. The fourth axis contributed 9.82% of the total variation while the fifth axis contributed 7.36% of the total variation. Significant phenotypic and genotypic correlations were observed between most of the plant characters evaluated and biomass accumulation which is an indication that the phenotypic association will be a good index for the genotypic association.

Does land use type impact the demographic and spatial structures of Adansonia digitata L. in the Pendjari Biosphere Reserve in Northern Benin?

Changes in land use type (LUT) are a major driver of biodiversity loss and species decline. Responses to changes in LUT are species-specific, which may in turn be context-dependent. Understanding such responses is essential for the management of socio-economically important wild tree species. The baobab, Adansonia digitata L., is an important traditional agroforestry tree species in Sub-Saharan Africa. This study assesses how LUT affects the demographic and spatial structure of baobab stands. Using data from a census and mapping of baobab trees in 12 plots of 250 m × 250 m each, the study compared baobab tree density, total height and diameter, diameter size-class distribution (SCD), stand stability, and spatial relationships in a strictly protected area (national park), a buffer zone and farmlands (Matéri and Boukombé) in the Pendjari Biosphere Reserve in Benin. The results show that the highest young and adult tree densities are in farmlands (particularly in Matéri), followed by the buffer zone and the national park. No significant differences in tree diameter and total height of baobab trees were found among the different LUT. The SCD had a reverse J-shape with a better negative slope and population stability metrics in farmlands (particularly in Matéri) but a flattened slope in the buffer zone. The spatial distributions of juvenile and adult baobab trees were random, and independent of each other. The spatial distribution of juvenile and adult baobabs was also independent of the other tree species, irrespective of LUT. It was concluded that baobab conservation is better in farmlands than in the national park but that the difference between park and farmlands may be context-dependent, probably linked to local environmental conditions, the socio-ecological context and interactions with baobab trees.

Allelopathic Influence of <i>Quercus</i> Species on Performance of Traditional Food Crops of the Western Himalayan Region

The present study was undertaken to assess the allelopathic effect of three Quercus species viz., Q. leucotrichophora , Q. floribunda and Q. serrata on germination and radicle-plumule growth of small millets ( Echinochloa frumentacea , Eleusine coracana and Amaranthus caudatus ) and one cereal crop wheat ( Triticum aestivum ) which are the major agricultural hill crops through laboratory bioassay. The aqueous extracts were prepared from the leaf and bark of the selected Quercus species and diluted to get 10, 25, 50, 75 and 100% concentrations. When increasing concentrations of leaf and bark extracts from 10 to 100%, it inhibited the germination and growth performance of test crops. Among the test crops, T. aestivum and E. frumentacea were found most susceptible while E. coracana and A. caudatus were the most resistant test crops. The leaf extracts were found to be more toxic in inhibiting germination and radicle-plumule growth of test crops as compared to bark extracts. The importance of these tree crops as prominent agroforestry tree species decreased in order Q. leucotrichophora < Q. floribunda < Q. serrata respectively Therefore, the results obtained within the scope of our study yielded sufficient preliminary evidence for considerable allelopathic effects from Q. floribunda and Q. serrata .

Fine-scale spatial genetic structure, mating, and gene dispersal patterns in Parkia biglobosa populations with different levels of habitat fragmentation.

PremiseA good understanding of genetic variation and gene dispersal in tree populations is crucial for their sustainable management, particularly in a context of rapid environmental changes. West African Sudanian savannahs are being fragmented and degraded, partly due to expansion of crop cultivation and monocultures that reduce tree density and may impact pollinators. The population dynamics of important indigenous trees could also be affected. We investigated the influence of habitat fragmentation on patterns of genetic diversity and gene dispersal of a key Sudanian agroforestry tree species, Parkia biglobosa.MethodsUsing 10 highly polymorphic nuclear microsatellites, we genotyped 2475 samples from reproductive trees, seedlings, and embryos in four tree populations presenting different levels of habitat fragmentation.Results Parkia biglobosa presented similar high genetic diversity across the four populations studied. Genetic diversity and inbreeding were similar between adults and embryo cohorts. In all four populations, the selfing rate was less than 1%. The effective number of pollen donors per tree was high (N EP~ 18–22), as was the pollen immigration rate (from 34 to 74%). Pollen dispersal was characterized by a fat‐tailed distribution with mean estimates exceeding 200 m. In three populations, stem diameter had a pronounced effect on male reproductive success. Here, the highest male reproductive success was observed in trees with a diameter at breast height between 60 and 75 cm.ConclusionsAt the scale analyzed, fragmentation does not seem to pose limitations to gene flow in any of the sites investigated, regardless of the landscape configuration associated with the different tree stands. The study provides useful insights on the reproductive biology of an important tree species in the West African savannahs.

Dynamics in tropical lowland soil nutrients as influenced by leafy biomass of some agroforestry trees

One of the major challenges of the developing countries is the production of sufficient food for the rapidly increasing population, and over cultivation of land resulting to soil infertility. Hence, transfer of nutrients through tree biomass contribute to micro variability in soil fertility and plant growth. A field research was conducted in the forest nursery of the Federal University of Agriculture, Abeokuta (FUNAAB), Nigeria to investigate the response of tropical lowland soil to the application of leafy biomass of some agroforestry tree species; Anogeissus leiocarpus, Enterolobium cyclocarpum, Gliricidia sepium, Leuceana leucocephala and Treculia africana at the rate of 5 tons per hectare (5t ha-1 or 5000 kg ha-1). The soil samples were collected at 2, 4, 6, 8 and 10 weeks after application (WAP). Split plot experimental design was used with the time of soil sampling as main plots, mulch type as sub-plots. Data were statistically analysed using Analysis of Variance (ANOVA) at p =0.05 on pH, organic carbon, total N, P, K, Ca, Mg and Na. L. leucocephala had highest nutrient release values on; total nitrogen (0.019±0.002), calcium (41.07±3.75), sodium (139.0±36.927). Control plots was high in organic carbon (3.12±0.067), as well as pH (6.45±0.029). However, E. cyclocarpus also had highest nutrient contents in potassium (90.0±4.79) and magnesium (152.50±24.575). It is concluded that L. leucocephala had fast decomposition rate and its rapid nutrient release is a good alternative to improving soil nutrients in lowland tropical soil and therefore recommended as a better choice soil improvement agroforestry tree leafy biomass among other species as investigated from the study.

Policy forum: Shifting cultivation and agroforestry in the Amazon: Premises for REDD+

Evidence shows that there is a close link between the intensification of shifting cultivation (SC) and the Amazon forest resilience. However, SC, to this day, is a widely implemented agricultural practice around the Amazon region due to its cultural, social, and economic relevance. In pristine indigenous communities, which have not experienced Western influence, SC will continue to be the main livelihood as part of the conservation of a patrimony of the humanity. Nevertheless, the main adverse effects of SC on ecosystems (i.e. forest degradation), particularly on Amazon forests, are our grounds to justify the implementation of public policies aiming to the substitution by agroforestry systems (AFS) as a sustainable food system. In this context, we propose linking AFS to Reducing Emissions from Deforestation and forest Degradation (REDD+ strategies) in shifting cultivation landscapes where there is high local-scale expansion and intensification of SC. AFS has higher potential as sustainable food systems for degraded forest rehabilitation and reduction of the expansion and intensification of SC. Consequently, AFS reduce deforestation of new forest areas for SC, meanwhile, sustainable management of second-growth forests could also be implemented through improved fallows, increasing the planting density of long-cycle agroforestry tree species. AFS should be implemented in local communities, in particular, those undergoing human-modified Amazon landscapes, where there is a high intensification of SC.

Effects of Tree Forest Plantations on Soil Physicochemical Properties in the Arboretumof Ruhande,Southern Province of Rwanda

Different tree speciesare blamed to have negative effects on soil ecosystems by changing soil physicochemical properties, and hence soil quality. However, few researches to verify this statement were done in Rwanda. This study provides prior information on the effects of planted forest tree species on soil physicochemical properties. It was conducted in the Arboretum of Ruhande, in southern Rwanda. Soil cores were collected in plots of exotic, native and agroforestry tree species. Collected soils were analysed for soil pH, total nitrogen, organic carbon, available phosphorus, aggregate stability, bulk density, soil humidity, cation exchange capacity, and soil texture. Soils sampled under exotic tree species were acidic, richin soil organic carbon, and in soil available phosphorus. Native and agroforestry tree species offer better conditions in soil pH, soil water content, cation exchange capacity, clay and silt. Less variations in soil total nitrogen and soil bulk density were found in soils sampled under all studied forest types. Research concluded that studiedtree species have different effects on soil physicochemical parameters. It recommended further studies to generalize these findings.
 Key words: soil, exotic, native, agroforestry, soil properties

Selection and evaluation of superior planting materials of Ailanthus triphysa (Dennst.) in Thrissur district, Kerala

An experiment was carried out to test the seedling characters and early field growth performance of candidate plus trees of Ailanthus triphysa from Thrissur district, Kerala. This species is one of the most widely cultivated agroforestry tree species in Kerala. Its major uses are for making match splints, furniture manufacturing, and aromatic resin called Halmaddi, used for making incense sticks. Twelve candidate plus trees were selected based on the comparison tree method from three distinct agro ecological zones of Thrissur District, Kerala. The germination and biometric characters of the progenies showed significant difference at nursery and at field level. Highest germination percentage of 83.50 was recorded by CPT-11 and lowest of 67 percentage by CPT-1. The CPT-11 showed significantly higher height of 88.67 cm at nursery and attained maximum height of 99 cm and girth of 21.04 mm from the field performance (180 DAP). Other promising progenies at the field level were CPT-10 and CPT-09.

Biomass production and nutrient content of three agroforestry tree species growing on an acid Anthropic Ferralsol under recurrent harvesting at different cutting heights

Agroforestry systems may alleviate challenges relating to soil degradation and low livestock production for smallholder farmers. Species-adjusted management regimes will determine how agroforestry fits in farming systems. Long-term productivity of biomass in agroforestry systems managed for fodder production requires tree species that coppice after repeated cutting. This study evaluated the effect of different cutting heights (0.3 and 1.0 m) and repeated harvests (1–5) on biomass production and chemical composition of the leguminous trees Acacia angustissima, Leucaena pallida and Mimosa scabrella in a field study on an Anthropic Ferralsol in Southern Rwanda. Shoot biomass production was highest at 0.3 m cutting height for A. angustissima and L. pallida, but M. scabrella could not survive that cutting height. Shoot biomass was highest for A. angustissima and lowest for M. scabrella, which did not adapt to repeated harvests. Leaf:stem ratio was not affected by cutting height. Cutting height did not affect crude protein (CP), but neutral detergent fibre (NDF), acid detergent fibre (ADF) and total polyphenol (TP) concentrations were higher at 1.0 m cutting height than at 0.3 m. Crude protein was highest in A. angustissima and lowest in M. scabrella, while NDF and ADF were highest in M. scabrella. Although all species provided high feed quality in terms of high CP content at both cutting heights, low cutting height (0.3 m) is recommended for A. angustissima and L. pallida for higher overall quality and biomass production.

Measurement of Sequestered Standing Carbon Stock in Major Agroforestry Tree Species

In the present investigation, the aboveground and belowground carbon sequestration potential of agroforestry tree species from seven sectors of Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU) campus was measured as a proxy of carbon fixation of agroforestry trees in Bangladesh. This campus occupies the area of 75.55 ha. Carbon emission has been increasing day by day due to anthropogenic activities and contributing to global climate change. Biomass production in different forms, i.e., aboveground biomass (AGB), belowground biomass (BGB), total biomass (TB), plays an essential role in carbon sequestration in trees. We estimated these biomasses by the nondestructive method to calculate the aboveground carbon (AGC), belowground carbon (BGC), total carbon (TC), and total CO2 of the study area. We found that the standing aboveground biomass and belowground biomass of agroforestry trees were 29.97 tha-1 and 7.79 tha-1 respectively, while the total standing biomass of agroforestry trees in 75.55 ha area was 37.76 tha-1. In the case of carbon, we observed that the total carbon sequestration and total carbon dioxide intake of agroforestry trees were 18.88 tha-1 and 69.29 tons CO2, respectively, in the study area. The highest carbon dioxide sequestration was observed in sector 6 (25%), and the lowest was observed in sector 3 (5%). The findings of carbon sequestration obtained from this study will be helpful for policymakers to take necessary steps against the adverse effect of global warming through carbon emission.

Agro-Economic Implications of Combined Application of Organic and Mineral Fertilizers on Maize

Continuous cultivation without adequate fertilizer application is responsible for plant nutrient depletion and yield decline of major food crops in sub-Saharan Africa. Field experiments were conducted on umbric Cambisol in Babungo and ustic Oxisol in Bansoa in the Western Highlands of Cameroon over two years to evaluate the effects of combined application of leaf biomass of agroforestry species and mineral fertilizers with their economic returns on maize yield performance. Ten treatments encompassing sole mineral fertilizer, sole leaf biomass of Calliandra, Leucaena, Acacia and Cassia, leaf biomasses combined with mineral fertilizer and absolute control were laid in a randomized complete block design and replicated three times. Data collected on maize grain yield was subjected to analysis of variance using XLSTAT version 2014 statistical software. In addition, an economic analysis was performed to evaluate the profitability of the different treatment combinations. The results showed significant differences (P ≤ 0.05) amongst the different treatments on maize yield on both soil types. The highest maize yields which stood at 5.93 t/ha and 6.01 t/ha were recorded in plots treated with Acacia and Cassia plus half recommended mineral fertilizer on umbric Cambisol and ustic Oxisol respectively. Economic analyses showed that Acacia and Cassia plus half recommended mineral fertilizer gave the highest net benefit and return to labor of 286500 FCFA and 5.1 on umbric Cambisol and 296051 FCFA and 5.3 on ustic Oxisol respectively. On both soils, all the treatments except Calliandra with half recommended mineral fertilizers were economically profitable with benefit to cost ratios that ranged from 2.02 to 2.92. Combined application of agroforestry tree species leaf biomass and mineral fertilizers is an appropriate technology to enhance maize grain yield and is economically profitable except Calliandra with half recommended mineral fertilizers and is therefore recommended for degraded Calliandra and Oxisols in the Western Highlands of Cameroon.

Effect of agronomic treatments on arbuscular mycorrhizal fungi under nursery conditions of Warangal

Influence of different agronomic practices on root nodulation, AM colonization and growth of forest tree species was studied in two agroforestry tree species Acacia nilotica and Albizia lebbeck. Neem cake and Farmyard manure and sewage water were analyzed for their effect on A. nilotica and A.lebbeck. These treatments along with different AM fungi were also analyzed. Farmyard manure was found to be effective with Glomus fasiculatum in A. nilotica and Neem cake was given best results in A.l ebbeck with Glomus fasiculatum.

English

Moringa stenopetala is one of the indigenous agro-forestry tree species cultivated in multi-storey inter-cropping system in the southern dry land areas of Ethiopia. It is an economically important tree species in which most parts of the plant are used for different purposes. Leaves of the plant collected from age classes of the tree are edible after processing. Despite its wider usage in the southern parts of the country, little is known about the nutritional composition of the leaves at different age classes of the tree. We investigated the effect of tree age on nutritional, ant-nutritional and proximate composition of M. stenopetala leaves and determined the moisture content, ash content, crude fiber, crude protein, fat, tannin content, phytate content, iron, calcium, phosphorus and potassium in the leaves. Authentic representative M. stenopetala leave samples were collected from 3, 4, 5, 6 and 7 years old tree in Derashe area, southern part of Ethiopia. The collected leaf samples were dried and subjected to physico-chemical analysis following standard methods of analysis. The laboratory results were analyzed using SAS Statistical software. The analysis indicated a significant difference in the main effect of all nutrition and anti- nutritional parameters between the five classes at 1% significant level. However, there was no significant difference in the cationic composition of iron and zinc among age classes of the tree. This study suggests that plant age has an influence on nutrition, anti-nutritional composition and most of the proximate elements. M. stenopetala trees that grew up well and reached age of five had better nutritional, anti-nutritional and proximate composition implying that leaf collection should to be done on trees that are established and grown well and reached at least five years of age.   Key words:  Moringa stenopetala, nutritional, anti-nutritional, proximate composition.

Developing tree volume equation for Parkia timoriana grown in home gardens and shifting cultivation areas of North-East India

ABSTRACTParkia timoriana (DC.) Merr. is an economically important agroforestry tree species grown in home gardens and shifting cultivation areas throughout the North-eastern states of India. This study aimed to establish a best fit volume model to facilitate estimation of biomass and carbon stock of the species without destructive sampling. Stem volumes of 360 trees representing 12 populations were estimated, and the data were used to develop 19 volume models involving diameter at breast height (D) and height (H). These models were then subjected to statistical test, and then cross-validated to select the best fitting model. The coefficient of determination (R2), root mean square error (RMSE), mean absolute deviation (MAD) and Akaike’s Information Criterion (AIC) were used for model selection, and scattered plot with residuals along with paired t-test were used for validation of the resultant models. Among the models compared, V = 0.12500–2.40265D + 21.43248D2 was found to be the best using single independent variable (D), while V = 0.03177 + 1.032D2H was the best model among the models with two independent variables (D and H). These two models gave high accuracy and hence can be used for future referencing.

EFFECT OF THE BOTANICAL PELLETINGS AND STORAGE PERIODS ON THE GERMINATION OF AFRICAN STAR APPLE (CHRYSOPHYLLUM ALBIDUM G. DON) SEEDS

There is paucity of quantified information on the simple, safe and affordable methods of invigorating seeds and storage of recalcitrant seeds. In this light, investigation was conducted in the screen house of the Federal College of Forestry Mechanization, Afaka, Kaduna on the effect of the botanical pelletings and storage periods of C. albidum seeds. A seed pellet is a coating, usually of clay mixed with other inerts, which streamlines the size, shape, and uniformity of a small, non-round seed. A split-plot experimental design with four (4) replications was laid down to assess the effect of botanical pelletings with the leaves of six agro-forestry tree species (Gliricidia sepium, Leucaena leucocephala, Albizia lebbeck, Acacia auriculiformis, Parkia biglobosa and Dacryodus edulis) and storage periods (0, 1, 2, 3 and 4 weeks) on the germination of C. albidum seeds stored in the refrigerator. The data were subjected to analysis of variance (ANOVA)using SAS (2003)software. The percentage germination of seeds pelletized with G. sepium, L leucocephala, A. lebbeck, A. auriculiformis, P. biglobosa and D. edulis ranged between 18.50%-42.00%, 8.3%-13.60%, 5.2%-18.80%, 3.6% -16.30%, 5.0%-14.30%, and 2.5%-11.10%, for 2-8 weeks respectively. The percentage germination of seeds stored for 0, 1, 2, 3 and 4 weeks ranged between 8.50%-21%, 4.70%-24.58%, 9.42%-22.75%, 8.67%-19.58% and 3.33%-8.83% respectively. The percentage germination of seeds pelletized with the leaves of G. sepium, L. leucocephala, A. lebbeck, A. auriculiformis, P. biglobosa and D. edulis and stored for storage periods ranged between 1-65%, 0-30%, 0-30.5%, 1-25%, 0-20% and 0-30%. Botanical pelletings and storage periods significantly (P<0.05) enhanced the germination of C. albidum seeds. Highest germination percentage of 65% was recorded for seeds pelletized with G. sepium leaves and stored for 3 weeks. The research therefore recommends seed pelleting with G. sepium leaves and storage for 3 weeks for mass production of C. albidum seedlings for agro-forestry systems.

Acclimatization of Terminalia Arjuna saplings to salt stress: characterization of growth, biomass and photosynthetic parameters

ABSTRACTTerminalia Arjuna is an ecologically important agroforestry tree species across Central Asia where imbalance between water inputs and plant uptake is resulting in secondary salinization. Therefore, this study was conducted to evidence its survival capability under control, medium and high salt stress condition (2, 8, 16 dS m−1, respectively). Two independent experiments were conducted and various parameters such as (i) germination percentage (ii) growth and biomass production and, (iii) leaf gas exchange parameters were measured. The results showed that irrespective of salt stress treatment, germination percentage decreased significantly with increase in salt stress. However, growth parameters and biomass production in leaves, stem and roots were not impacted under medium salt stress but decreased significantly under high salt stress. Stomatal conductance decreased significantly under both salt stress treatments whereas CO2 assimilation rate and water use efficiency was not impacted by medium salt stress. Finally, an increase in biomass production was positively correlated to both increase in CO2 assimilation rate and stomatal conductance. The results showed that although germination in Terminalia arjuna was highly sensitive to salt stress, young plants can tolerate medium salt stress due to their ability to sustain CO2 assimilation rate and increased water use efficiency.

Adoption and Impact of the Improved Fallow Technique on Cotton Productivity and Income in Zambia

An improved fallow is a soil fertility agroforestry technique that has commonly been used in the staple maize production systems of Zambia and sub-Saharan Africa. Several studies have assessed the adoption and impact of the improved fallow on maize production. Generally, it has been observed that though the improved fallow does increase maize yields, its efficacy on welfare in terms of increased income is low. The use of the technique on cash crops that could significantly contribute to household welfare has rarely been investigated. This study assessed the factors affecting the adoption and impact of improved fallows on a commonly grown cash crop, cotton, in the cotton growing provinces of Zambia. The study used a sub sample (N=1206) of the nationally representative 2014/15 Rural Agricultural Livelihoods Survey (RALS) data which was randomly collected by the Indaba Agricultural Policy Research Institute (IAPRI) and Central Statistical Office (CSO) of Zambia. The determinants of improved fallow adoption among the cotton farmers were examined through the use of the probit model while the impact of the technique on cotton production and income was evaluated by using the propensity score matching and the endogenous switching regression models. Among the socioeconomic factors significantly increasing the probability of improved fallow adoption included: increases in age, education level, and per capita productive assets of the farmer, in addition to the area under cotton production and the distance of the homestead to the market. Institutional factors found to increase the farmer’s likelihood of adopting the improved fallow in the cotton production systems included; farmer membership to a cooperative, receiving improved fallow seedlings from the government projects and having information on agroforestry tree species. On the other hand, an increase in land size per capita was found to negatively affect the likelihood of improved tree fallow adoption. Impact estimates showed significant cotton yield and income increases as a result of adopting the technique. The continuous provision of information on relatively new techniques such as the improved fallows preferably in farmer organized groups, and support towards the provision of the technique’s planting materials are some of the areas requiring government and NGOs attention. In addition, the study recommends that the farmers’ formal education level should be enhanced and that improved tree fallows should also be explicitly promoted on cash crops that have similar agronomic requirements to maize such as cotton.

Ecophysiological response of early stage Albizia lebbeck to cadmium toxicity and biochar addition

Cadmium (Cd) toxicity is among the most prominent issues regarding land degradation. Traditional approaches for soil remediation are not effective. However, phytoremediation is described as the most efficient, economical, and sustainable approach to combat with terrestrial heavy metal pollution. Moreover, if phytoremediation is used in combination with soil amendment, its effectiveness can be increased several folds. Among soil amendments, biochar is considered the best amendment due to its potential for remediation and plant growth. The objective of this study was to determine the phytoremediation potential of Albizia lebbeck in Cd-contaminated and biochar-amended soils. A pot experiment was planned to test the ecophysiological response and Cd uptake of 3-month-old uniform-sized Albizia lebbeck seedlings. Cadmium was induced in soil through irrigational water at the rate of 25 mg/L. Two concentrations of biochar were used: B1 (3%) and B2 (6%). A total of six treatments were applied: Cd0B0 (T1), Cd0B1 (T2), Cd0B2 (T3), Cd1B0 (T4), Cd1B1 (T5), and Cd1B2 (T6), where, Cd0 and B0 designate the control treatment. The plants were harvested after 4 months of growth in the soil with amendments. The maximum growth and gas exchange characteristics were showed by the plant of T3. Cadmium toxicity reduced the growth and gas exchange characteristics to a great extent. Plants of T4 showed the minimum growth compared to the other amendments. The addition of 6% biochar in Cd-contaminated soil (T6) resulted in the decent increase in the growth of plants. The maximum root length (67.18 cm) and shoot length (80.06 cm) were observed in the plants of T3, whereas, the minimum root length (13.94 cm) and shoot length (35.03 cm) were observed in the plants of T4. This study suggests that biochar can be used to enhance the growth of agroforestry tree species like Albizzia lebbek in Cd-contaminated soils.

Contrasting water use patterns of two important agroforestry tree species in the Mt Elgon region of Uganda

ABSTRACTLack of information on water use of key agroforestry species is an obstacle to understanding their influence on crop productivity. Cordia africana and Albizia coriaria are the dominant tree species of smallholder farming systems in the Mt Elgon region of Uganda and have multiple uses in agroforestry systems. This study deployed six sap flow meters on stems of three selected trees each of C. africana and A. coriaria on-farm. The objective of the study was to assess the daily water use patterns of these agroforestry tree species at different times of the year. We measured the daily sap flow of these two species using the heat ratio method over a period of 18 months. There was a significant main effect of the interaction between tree species and season on daily water use. The two species show contrasting patterns of seasonal water use across leaf shedding stages characterised by episodes of reverse flow in A. coriaria at specific periods of the year. We propose that reverse flows in A. coriaria were triggered by leaf shading while the zero flows in C. africana, which occurred during rainfall events, could have resulted from a lag phase, an indication that the two species may have different water-use strategies. Although C. africana uses 12–15 l day−1 and A. coriaria uses 20–32 l day−1 based on the study trees, C. africana generally uses 12% more water than A. coriaria on a standardised daily basis. Albizia coriaria exhibited radial variation of sap velocities between the inner and outer thermocouples at different periods of measurement, a phenomenon worth investigating further. The leaf shedding patterns of the two trees provide an opportunity for maximising the temporal complementarities of agroforestry systems where these trees exist. This knowledge of C. africana and A. coriaria tree water use provides critical insight for developing successful long-term tree monitoring and management programs in agroforestry systems.

Impact of Climate Change on Species Distribution and Carbon Storage of Agroforestry Trees on Isolated East African Mountains

Changes in climate will affect conditions for species growth and distribution, particularly along elevation gradients, where environmental conditions change abruptly. Agroforestry tree (AGT) species on the densely inhabited slopes of Mount Kilimanjaro and Taita Hills will change their elevation distribution, and associated carbon storage. This study assesses the potential impacts of climate change by modelling species distribution using maximum entropy. We focus on important agroforestry tree species (Albiziagummifera, Mangiferaindica and Perseaamericana) and projected climate variables under IPCC-AR5 RCP 4.5 and 8.5 for the mid-century (2055) and late century (2085). Results show differential response: downward migration for M. indica on the slopes of Mount Kilimanjaro is contrasted with Avocado that will shift upslope on the Taita Hills under RCP 8.5. Perseaamericana will lose suitable habitat on Kilimanjaro whereas M. indica will expand habitat suitability. Potential increase in suitable areas for agroforestry species in Taita Hills will occur except for Albizia and Mango which will potentially decrease in suitable areas under RCP 4.5 for period 2055. Shift in minimum elevation range will affect species suitable areas ultimately influencing AGC on the slopes of Mount Kilimanjaro and Taita Hills. The AGC for agroforestry species will decrease on the slopes of Mount Kilimanjaro but AGC for Mango will increase under RCP 8.5 for period 2055 and 2085. In Taita Hills, AGC will remain relatively stable for A. gummifera and P. americana under RCP 8.5 for period 2055 and 2085 but decrease in AGC will occur for M. indica under projected climate change. Climate change will affect AGT species and the amount of carbon stored differently between the sites. Such insight can inform AGT species choice, and conservation and support development by improving carbon sequestration on sites and reliable food production.