Growth and yield of maize in Eucalyptus tree alley cropping agroforestry practice in Kafa Zone, Ethiopia

Variability in allometric relationships for temperate woodland Eucalyptus trees

Machine learning (ML) algorithms can be used to predict wood volume in a faster and more accurate way, providing reliable answers in forest inventories. The objective of this work was to evaluate the performance of different ML techniques to predict the volume of eucalyptus wood, using diameter at breast height (DBH) and total height (Ht) as input variables, obtained by measuring DBH and Ht of 72 trees of six eucalyptus species (Eucalyptus camaldulensis, E. uroplylla, E. saligna, E. grandis, E. urograndis, and Corymbria citriodora). The trees were cut down in two different epochs, rendering 48 samples at 24 months and 24 samples at 48 months, and the volume of each tree was measured using the Smailian method. This research explores five machine learning models, namely artificial neural networks (ANN), K-nearest neighbor (KNN), multiple linear regression (LR), random forest (RF) and support vector machine (SVM), to estimate the volume of eucalyptus wood using DBH and Ht. Artificial neural networks achieved higher correlations between observed and estimated wood volume values. However, the RF outperformed all models by providing lower MAE and higher correlations between observed and estimated wood volume values. Therefore, RF is the most accurate for predicting wood volume in eucalyptus species.

Allometry and partitioning of above- and below-ground biomass in farmed eucalyptus species dominant in Western Kenyan agricultural landscapes

River red gum (Eucalyptus camaldulensis), native to Australia, has been introduced into Taiwan in the past decade for the purpose of paper manufacturing. Field survey of weed flora inside and outside of this eucalyptus forest area and subsequent seed bank investigation of soils collected from the forest showed that the germination and growth of several indigenous weed species were suppressed by eucalyptus trees, possibly due to competition, shading and/or allelopathic effect. Seedling test of seven weed species at 5 to 7-leaf stage cultivated in medium premixed with different amounts of eucalyptus leaf powder showed that the growth of three weeds of Amaranthaceae family were significantly retarded by this powder at 17% (v/v) rate, and the injury index of slim amaranth was dramatically increased even at a rate of 9% (v/v). In addition, sedge weeds were also affected, though at a less extent, and Gramineae spp. weeds were the least susceptible. Seed germination of edible amaranthus and some Brassica spp., such as field mustard, Fung-Shan cabbage and radish, was significantly inhibited within 2 to 3 days by the water extract of eucalyptus leaves. In addition, the radicle growth of five vegetables was all significantly inhibited more than ca. 70% by this water extract. The allelopathic potential of this eucalyptus species may be worth considering in the development and/or application of bioherbicides in organic farming system.

This research assessed the carbon sequestration potential of ornamental trees within Isaac Boro Park Port Harcourt. Data on tree height and diameter at breast height (DBH) were collected using the purposeful sampling technique with the aid of D-tape and digital clinometer. The allometric method was employed to estimate carbon sequestrated from the above and below ground biomass derived from tree height and DBH measurement. Eucalyptus camaldulensis, Peltophorum pterocarpum, and Delonix regia had the highest mean heights of 107.82m, 94.88m, and 52.84m, respectively, while Roystonia regia and Pinus caribaea recorded the least heights at 96.28m and 81.04m. Eucalyptus camaldulensis, Delonix regia, and Peltophorum pterocarpum recorded the highest mean DBH values of 85.40cm, 63.85cm, and 63.33cm, respectively, while Roystonia regia and Pinus caribaea had the lowest DBH 46.95cm and 45.33cm respectively. The below ground biomass was highest for Eucalyptus camaldulensis (144,426.58kg/m³), followed by Peltophorum pterocarpum and Delonix regia (67,511.34kg/m³ and 33,914.45kg/m³, respectively). Similarly, Eucalyptus camaldulensis recorded the highest above ground biomass (120,355.48kg/m³) and sequestered the highest carbon (160117.9221kg). Pinus caribaea and Roystonia regia sequestered the lowest carbon (38748.5775kg and 39823.7612kg respectively). This study provides valuable insights into the mean height, DBH, and carbon sequestration potential of ornamental trees in Isaac Boro Park Port Harcourt. Eucalyptus camaldulensis, Peltophorum pterocarpum, and Delonix regia should be integrated into urban forestry initiatives for dual benefits of beautification and climate mitigation.

This study examined the effect of alley cropping of Leucaena leucocephala and Faidherbia albida on wood biomass, maize grain yield and soil nitrogen status. The treatments were: trees planted alone at 1 × 5 m spacing; trees intercropped with maize and a sole maize crop. Mulch biomass averaged 6.18 and 0.97 t ha−1 for L. leucocephala and F. albida, respectively. Corresponding wood production was 1.71 and 1.11 t ha−1. Both total N and inorganic N (NO 3 − –N plus 4 + –N) were higher under F. albida and lowest under L. leucocephala. Similarly, foliar N concentration in maize was higher in plots intercropped with F. albida and least in L. leucocephala intercropping. Maize grain yield was little affected by the tree intercrop as competition for resources was reduced through periodic pruning and clean weeding. There was no gain in maize grain yield due to the presence of L. leucocephala and F. albida. These results suggest that alley cropping in Gario is justified for wood production but not for increasing maize grain yield.

Flavonoids are essential molecules that affect plant growth and development and act as defense mechanisms against biotic and abiotic factors. This study aimed to assess whether the content of flavonoids in different species of Eucalyptus is related to tree growth. The objective of the work is (i) to identify whether there is a relationship between flavonoids, height and diameter among Eucalyptus species and (ii) to identify differences in flavonoid content between species. The experimental design was randomized blocks with three replicates, with 20 plants in each experimental plot. The treatments consisted of six Eucalyptus species: Eucalyptus camaldulensis, E. saligna, E. grandis, E. urophylla, C. citriodora and a GG100 clone (hybrid clone of E. urophylla × E. grandis). This study measured plant diameter at breast height (DBH) and height (HC). Leaf samples were taken from the species in their respective repetitions for flavonoid evaluation, and subsequent separation and quantification of the isoflavones, daidzein (D1), daidzin (D2), genistein (G1), genistin (G2), using liquid chromatography. In general, the E. grandis species showed the best results for DAP and AP. D1 was higher than what? for C. citriodora and E. saligna. D2 was higher than what? for E. camaldulensis. The principal component analysis demonstrated a negative relationship among the variables AP and DAP with D1, D2, G1, and G2. With the results of this study, it can be inferred that there is no relationship between height, diameter, and flavonoids among the Eucalyptus species evaluated since the species with the lowest concentrations of isoflavones had the highest growth and diameter.

O plantio consorciado de eucalipto com leguminosas pode promover a melhoria da qualidade biológica do solo em áreas degradadas e também ser vantajoso para as espécies do consórcio. O objetivo deste trabalho foi avaliar a influência de sistemas de plantios (puros e consorciados) de Acacia mangium (AM), Sesbania virgata (SV) e Eucalyptus camaldulensis (EC), sobre o desenvolvimento das plantas em estudo (variáveis dendrométricas) e especificamente sobre a fauna da serapilheira e dos primeiros 5 cm do solo. Realizou-se um experimento, cujo delineamento utilizado foi o de blocos casualizados com seis tratamentos e três repetições. Os tratamentos utilizados para avaliação dos atributos dendrométricos foram: 100EC (100 % EC) e 100AM (100 % AM); 50EC:50AM (50 % EC + 50 % AM); 50EC:50SV (50 % EC + 50 % SV); e 50AM:50SV (50 % AM + 50 % SV). Para avaliação da fauna do solo foram: 100EC, 100AM, 100SV (100 % SV), 50EC:50SV e 50 AM:50SV. Aos 48 meses após o plantio, foram feitas medições de altura (H) e diâmetro à altura do peito (DAP) das espécies E. camaldulensis e A. mangium e estimativas da área basal (AB) e volume de madeira com casca por indivíduo (VCI). Na serapilheira e no solo (0-5 cm), foram avaliadas a abundância e diversidade da fauna edáfica. O E. camaldulensis quando cultivado em consórcio com as leguminosas apresentou maior DAP, AB e VCI. Em contrapartida, a A. mangium não teve essas variáveis influenciadas quando em consórcio com o E. camaldulensis e com a S. virgata. Plantios de E. camaldulensis e S. virgata em consórcio promoveram maior abundância total de organismos e maiores valores dos índices de diversidade de Shannon e Pielou, principalmente no que se refere ao compartimento serapilheira.

Machine learning techniques (ML) have gained attention in precision agriculture practices since they efficiently address multiple applications, like estimating the growth and yield of trees in forest plantations. The combination between ML algorithms and spectral vegetation indices (VIs) from high-spatial-resolution line measurement, segment: 0.079024 m multispectral imagery, could optimize the prediction of these biometric variables. In this paper, we investigate the performance of ML techniques and VIs acquired with an unnamed aerial vehicle (UAV) to predict the diameter at breast height (DBH) and total height (Ht) of eucalyptus trees. An experimental site with six eucalyptus species was selected, and the Parrot Sequoia sensor was used. Several ML techniques were evaluated, like random forest (RF), REPTree (DT), alternating model tree (AT,) k-nearest neighbor (KNN), support vector machine (SVM), artificial neural network (ANN), linear regression (LR), and radial basis function (RBF). Each algorithm performance was verified using the correlation coefficient (r) and the mean absolute error (MAE). We used, as input, 34 VIs as numeric variables to predict DHB and Ht. We also added to the model a categorical variable as input identifying the different eucalyptus trees species. The RF technique obtained an overall superior estimation for all the tested configurations. Still, the RBF also showed a higher performance for predicting DHB, numerically surpassing the RF both in r and MAE, in some cases. For Ht variable, the technique that obtained the smallest MAE was SVM, though in a particular test. In this regard, we conclude that a combination of ML and VIs extracted from UAV-based imagery is suitable to estimate DBH and Ht in eucalyptus species. The approach presented constitutes an interesting contribution to the inventory and management of planted forests.

On-farm experiments were conducted in the Philippines to study over a 4-year period the growth of two timber trees, gmelina (Gmelina arborea R. Br.) and bagras (Eucalyptus deglupta Blume), and their impact on the grain yield of intercropped maize. The experiment consisted of maize monocropping plots (control) and maize intercropped between trees planted in block (2 × 2.5 m), and hedgerow arrangement (1 × 10 m). Three maize crops were planted in the block plots before canopy closure, and seven maize crops were planted in the hedgerow and monocropping plots. Maize grain yield in the hedgerow and in the block arrangement with gmelina were respectively 37% (16.58 tons ha−1) and 68% (8.3 tons ha−1) lower than in monocropping (26.21 tons ha−1). In the plots with bagras, maize grain yield in hedgerow and in block arrangement were respectively 19% (24.8 tons ha−1) and 66% (10.4 tons ha−1) lower than in monocropping (30.6 tons ha−1). For both tree species, the diameter at breast height (dbh) was greater in hedgerow than in block arrangement, with the difference being more pronounced with age. It was estimated that gmelina planted in hedgerows would produce 6–8 m3 ha−1 of merchantable volume more than if planted in block. The study verifies the hypothesis that intercropping between widely-spaced trees rows (planted at 10 m or more) is more profitable and feasible to smallholders than either maize monocropping or woodlots, and concludes with recommendations on how to further improve the productivity of tree-intercropping systems.

Genus Eucalyptus belongs to the family Myrtaceae and consists of more than 900 species, various hybrids and varieties. The major species that are grown in Kenya are Eucalyptus grandis, E. globulus, E. saligna and E. camaldulensis. Most Eucalyptus species are highly dependent on rainfall and this is challenged by climatic changes owing to global warming making it difficult to effectively match the availability of mature trees and the market demand especially for use as power transmission poles. With the widespread availability of other naturally occurring Eucalyptus species such as E. camaldulensis and E. globulus, it becomes important to determine the genetic diversity and to analyze the phenotypic traits of these species for suitability as power transmission poles in order to counter the overdependence on E. grandis. Phenotypic traits investigated included measuring total tree height and diameter at breast height (DBH), while molecular data were obtained from sequencing MatK, rbcL and TrnL-F genes from selected species and evolutionary analyses such as nucleotide substitution rates, base composition disparity indices, evolutionary divergence, nucleotide diversity indices and phylogeny construction were conducted in MEGA 11. Significant differences in DBH and height among Eucalyptus species were observed when the phenotypic data were subjected to ANOVA. In this study, E. robusta, E. paniculata, E. maculata, E. dunnii, E. camaldulensis and E. citriodora are fit to be used as power transmission poles but they are limited by their short height. However, E. tereticornis and E. glaucina have the desired DBH and height and hence can be used as substitutes for E.grandis. Generally, the molecular phylogeny study has shown that the studied Eucalyptus species are closely related and form various monophyletic clades which can be attributed to the short genetic distances, low substitution rates, low nucleotide bias disparity indices and low diversity scores. Further phylogenetic and gene expression studies involving more Eucalyptus species are needed to better understand Eucalyptus phylogeny, and diversity and identify species with similar genetic make-up to that of E. grandis which has been used extensively for the provision of electricity transmission poles.

In forest modeling to estimate the volume of wood, artificial intelligence has been shown to be quite efficient, especially using artificial neural networks (ANNs). Here we tested whether diameter at breast height (DBH) and the total plant height (Ht) of eucalyptus can be predicted at the stand level using spectral bands measured by an unmanned aerial vehicle (UAV) multispectral sensor and vegetation indices. To do so, using the data obtained by the UAV as input variables, we tested different configurations (number of hidden layers and number of neurons in each layer) of ANNs for predicting DBH and Ht at stand level for different Eucalyptus species. The experimental design was randomized blocks with four replicates, with 20 trees in each experimental plot. The treatments comprised five Eucalyptus species (E. camaldulensis, E. uroplylla, E. saligna, E. grandis, and E. urograndis) and Corymbria citriodora. DBH and Ht for each plot at the stand level were measured seven times in separate overflights by the UAV, so that the multispectral sensor could obtain spectral bands to calculate vegetation indices (VIs). ANNs were then constructed using spectral bands and VIs as input layers, in addition to the categorical variable (species), to predict DBH and Ht at the stand level simultaneously. This report represents one of the first applications of high-throughput phenotyping for plant size traits in Eucalyptus species. In general, ANNs containing three hidden layers gave better statistical performance (higher estimated r, lower estimated root mean squared error–RMSE) due to their greater capacity for self-learning. Among these ANNs, the best contained eight neurons in the first layer, seven in the second, and five in the third (8 − 7 − 5). The results reported here reveal the potential of using the generated models to perform accurate forest inventories based on spectral bands and VIs obtained with a UAV multispectral sensor and ANNs, reducing labor and time.

The volume of each butt log and middle log of an individual tree at a 5-meter log length was calculated by using five different formulas (Newton`s, Smalian`s, Huber`s, Hossfeld`s, and Centroid method). The volume of the butt logs and middle logs was compared to the real volume (control), which was calculated by aggregating the volume measurements at (0.5) meters using Newton's method. Measurements were taken from 50 trees of (Eucalyptus camaldulensis) planted in Al-Khabat area in Erbil governorate. The sampled trees presented diameter at breast height (DBH) ranged from 30.2 to 75.6 cm and total tree height range from 13 to 27 m. The result showed that Newton`s formula was superior to all other formulas for estimating butt log volume of eucalyptus tree species plantation and Smalian`s formula was less accurate than other formulas. On the other hand, the centroid method was superior to all other formulas for estimating the middle log volume of eucalyptus tree species in the district of khabat in Erbil province. Moreover, the Hossfeld formula was less accurate than other formulas.

Pot and field experiments were conducted in the greenhouse and at three field sites (Marondera, Domboshawa and Makoholi) in Zimbabwe to examine the effects of soils and fertilizers on nutrient uptake and growth of 6 exotic tree species (Eucalyptus camaldulensis, E. grandis, E. tereticornis, Leucaena leucocephala, Casuarina cunninghamiana, and Acacia holosericea). Plant growth, N and P contents of all species were increased by the application of N, P, K and micronutrient fertilizers. The effect of individual nutrients (N, P, K and micronutrients) and their combination on Eucalyptus species was further investigated in a pot experiment using soil from Domboshawa. Eucalyptus species responded only to N application and no significant interactions were found between N and the other elements. Nutrient uptake results showed that E. camaldulensis and E. tereticornis removed more cations than the N-fixing trees but only in the fertilized treatments. L. leucocephala and C. cunninghamiana were higher in P, but no clear trends were observed for N. Plant growth and nutrient uptake by E. camaldulensis. C. cunninghamiana and A. holosericea were assessed in the field at the three sites. Plant species grown in the Marondera site had greater height and diameter at breast height (DBH) than those in the two other sites. These results followed trends in soil nutrient contents. The analysis of foliage revealed differences in the nutrient concentration of leaves from different trees, but no effect of site was found. The interrelationships between plant characteristics, soil and foliage nutrients were examined. In a pot experiment, mineral N was the only variable correlated with growth response and nutrient uptake, while in the field the only significant correlation was obtained with soil pH.

Summary For decades the floodplain forests of the River Murray have endured the effects of prolonged water stress. This has resulted in significant crown dieback and loss of condition. The Living Murray (TLM) initiative aims to restore the ecological health of six Icon Sites along the River. The two eucalypts River Red Gum (Eucalyptus camaldulensis) and Black Box (Eucalyptus largiflorens) that dominate the forests at five of the six Icon Sites are undergoing widespread decline. To enable effective management and restoration of these forests, we developed a standardised tree condition assessment method. Named the TLM tree condition assessment method, it utilises visual assessment of a range of tree crown variables (extent and density of the foliage in the crown, epicormic growth, new tip growth, reproductive activity, leaf die‐off, mistletoe infestation) and measurements of bark condition, diameter at breast height and dominance class. This article describes the TLM tree condition assessment method and assesses it for consistency between multiple observer teams after limited training. The level of observer agreement between six teams each comprised of two observers was assessed for seven of the ten variables. Intra‐class correlation was used to compare scores of 30 River Red Gum trees assessed on Gunbower Island on the River Murray. The level of agreement for all variables was statistically significant with six of seven variables having correlation coefficients over R = 0.5. The TLM tree condition assessment method was found to provide accurate estimates of a range of tree variables that can be used to determine tree condition. The TLM tree condition assessment method provides a valuable monitoring tool that can be used to assess management interventions, such as management flooding and silvicultural thinning.