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Grevillea robusta is widely interplanted with crops in Maragua subcounty, a practice that enhances biomass quantities in farmlands. However, quick tools for estimating biomass of such trees are lacking resulting in undervaluation of the farm product. This study sought to develop allometric equations for estimating tree biomass using diameter at bre...
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In this note, I record the death of a mature Grevillea whiteana McGillivray, 1986 (Proteaceae) tree growing in a local council verge in Junction Road, Winstons Hills, New South Wales during middle 2020. The termites destroyed the base of the tree resulting in the death of the rest of the tree. The tree was later blown over completely dead. Termites...
The taxonomy of Grevillea (Proteaceae) in New Caledonia is reviewed. The names G. deplanchei, G. macmillanii, G. rubiginosa, and G. sinuata are re-instated at the species rank. A new name, G. mondorensis, is provided for the plants previously identified as G. gillivrayi var. glabriflora, and two new species are described, G. nepwiensis and G. vunia...
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... Many studies have investigated the carbon sequestration potential of Silky Oak [36][37][38][39][40] using allometric equations and applying them to areas with mixed compositions, specific locations, biogeographical regions, or biomes with particular climates [41]. However, no studies have been published on the carbon sequestration potential of Silky Oak in Thailand. ...
... 0.68 GtCyr −1 , and the primary superstructure would account for the largest share of carbon storage (~80%) in a building assembly [36]. Many studies have investigated the carbon sequestration potential of Silky Oak [36][37][38][39][40] using allometric equations and applying them to areas with mixed compositions, specific locations, biogeographical regions, or biomes with particular climates [41]. However, no studies have been published on the carbon sequestration potential of Silky Oak in Thailand. ...
... A healthy soil provides a wide range of ecosystem goods and services that play a crucial role in sustaining biological productivity on marginal lands. There is a large potential for carbon sequestration in Silky Oak tree plantations [38]. When comparing the carbon storage potential in our sites with those found for different geographical areas and climates, we found that it was higher than that reported for Ethiopia (Africa); the aboveground carbon storage for trees of different ages (i.e., 5-10 years, 11-15 years, and more than 16 years) was 12.68, 25.63, and 157.90 tC·ha −1 , respectively [39], whereas the leaf and root biomass percentages varied between trees of different ages ( Table 6). ...
Silky Oak or Silver Oak (Grevillea robusta A.Cunn. ex R.Br.) is classified as a high-value economic wood in Thailand, it is also considered to be a plant that can grow rapidly, and it has the potential to efficiently reduce greenhouse gases emitted into the atmosphere. This research aimed to study and develop an allometric equation to evaluate the biomass of F1 Silky Oak, which was imported to Thailand from Australia, and grown in Thailand’s economic woods in Silky Oak sites in Pak Chong District, Nakhon Ratchasima Province. The sample group consisted of trees of different ages (i.e., of 2 years, 3–4 years, and 7 years). An allometric equation was used to determine the tree biomass, based on mathematical models that describe the relationship between tree biomass and diameter at breast height (DBH). It was developed in the form of a quadratic equation by multiplying the square DBH by the total height (DBH2 × Ht). Subsequently, the equation was separated into different components, which corresponded with different parts of the tree (i.e., stem, branches, leaves, and roots). The following equations were obtained for the stem: Ws = 0.0721 (D2H) 0.8297 R2 = 0.998. The following equations were obtained for the branches: Wb = 0.0772 (D2H) 0.7027 R2 = 0.977. The following equations were obtained for the leaves, Wl = 0.2085 (D2H) 0.4313 R2 = 0.990. The following equations were obtained for the roots: Wr = 0.3337 (D2H) 0.4886 R2 = 0.957. The results of a laboratory elemental analysis of the carbon sequestration in the biomass, using a CHN elemental analyzer, showed that the mean percentage of carbon content in the stems, branches, leaves, and roots was 45.805. Applying the developed allometric equation for evaluating carbon sequestration, using the survey data from the sample sites of Silky Oak, it was found that the amount of carbon sequestration for the aboveground biomass in three sites was 130.63 tCO2eq. When the amount was converted into carbon dioxide, which was absorbed in the three sites, we obtained a value of 478.99 tCO2eq. The results of the application of the allometric equation showed that there was substantial carbon sequestration potential in the surveyed sites, emphasizing the role of Silky Oak plantations for climate change mitigation and sustainable land management. This study advances our understanding of Silky Oak growth and carbon storage dynamics, offering valuable tools for biomass estimation and promoting environmentally beneficial land use practices.
... Grevillea robusta (silky oak) has been widely planted in warm temperate, sub-tropical and tropical highland regions of many countries as a shade tree for tea and coffee and as an agroforestry tree in small scale farms [8]. The species is native in Australia but has successfully naturalized in Kenya where it is grown in the lowlands mostly preferred as a fast growing agroforestry tree species [9]. The growing of this species in agricultural systems releases pressure on reliability of conventional forest resources and, therefore, play a major role in sustaining the productivity of agricultural and forested landscapes. ...
Flooding has become a common occurrence due to climate change leading to prolonged water-logging which suffocates plant rooting, thus reduced growth, yield or total loss. Limited research has been conducted on the same. This study is aimed at investigating the effect of flooding period on the early growth of Grevillea robusta nursery seedlings in Njoro, Kenya. An experiment was set up for 2 months in Egerton University Agroforestry tree nursery using a six months old Grevillea seedlings. Completely randomized block design (RCBD) with 4 treatments replicated 3 times was used. The treatments were: Non-flooding, 2 days flooding, 4 days flooding and 6 days flooding. Data was collected for shoot, foliage and root variables and analyzed using SAS statistical package while means were separated using least significance difference (LSD). Non-flooding recorded the highest performance for all the shoot and foliage variables while the least was 2 days flooding. On the other hand, 6 days flooding was the second in performance for most of the variables especially 3rd internode length (20.2 mm) and fresh shoot biomass (56.4 g) were significantly (P=0.002 and 0.05) higher respectively compared with 2 days flooding (13.5 mm and 46.7 g) respectively. In conclusion, flooding affects the growth of Grevillea seedlings negatively by reducing their growth and this was more pronounced in 2 days flooding. However, for 6 days flooding, the seedlings seem to adjust through development of adaptive strategies in the roots. Further research needs to be conducted on other species and also prolonged flooding period.
... Under the banana-grevillea intercrops, soil sampling was done at fixed points around the tree [22] as an adaptation of the method described by Kamau et al. [23]. The area around the selected trees was delineated into four concentric zones, A, B, C and D. Approximately, the sampling point A, B, C and D around the single grevillea tree were always taken at 0.25; 1; 2 and 5 m from the tree stem, respectively, since the average diameter of these trees was 5 m under the current management scheme in the Central Kenya [24]. In banana and grevillea pure stands, two sampling points were marked [25]. ...
In Africa, banana is mainly produced by smallscale farmers under complex production systems for both home consumption and income generation. Low soil fertility continually constraints its production and farmers are embarking on emerging technologies such as improved fallow, cover crops, integrated soil fertility management, agroforestry with fast growing tree species to address this challenge. This study aims at assessing the sustainability of grevillea-banana agroforestry systems by investigating the variability in their soil physico-chemical properties. Soil samples were collected in banana sole stands, Grevillea robusta sole stands and grevillea-banana intercrops in three agro-ecological zones during the dry and rainy seasons. Soil physico-chemical properties significantly differed among agroecological zones, cropping systems and between seasons. Soil moisture, total organic carbon (TOC), P, N, Mg decreased from the highland to the lowland zone, through the midland zone whereas soil pH, K and Ca showed the opposite trend. Soil bulk density, moisture, TOC, NH4+-N, K and Mg were significantly higher in the dry season compared to the rainy season but total N was higher in the rainy season. Intercropping banana with grevillea trees significantly decreased soil bulk density, TOC, K, Mg, Ca and P. Soils under banana sole stands accumulated higher potassium, magnesium, calcium, phosphorus with a higher soil bulk density and pH compared to grevillea-banana intercrops and grevillea sole stands. This suggests that intercropping banana and grevillea trees increases the competition for these nutrients and requires careful attention for the optimization of their interactive benefits.
... A recent global survey has shown that over 45% of agricultural lands have more than 10% treecover (Zomer et al., 2016) with farmers growing both native and exotic trees on their farms for various purposes (Nyaga et al., 2015;Agevi et al., 2019). The presence of trees on farmland helps to offset pressure on natural forests in addition to contributing to the improvement of productivity of agricultural and forest landscapes (Mugo, Mwangi and Omamo, 2018). The native trees can either be planted or grow naturally based on the soil seed bank or proximity to a natural forest stand from which seed dispersers like birds and simians frequently visit the adjacent farmlands. ...
Background: Growing of trees on-farms has contributed significantly in easing pressure on the Kakamega-Nandi Forest Ecosystem. There are however concerns that Eucalyptus species is becoming the dominant tree in this landscape and may have adverse effects on the environment. Objectives: To determine the trade-offs in tree species selection and carbon offsets on farms in the margins of the Kakamega-Nandi Forest Ecosystem. Methodology: It employed a nested experimental design where the study area was divided into three 3x1 km sentinel blocks. Three different landscape models were chosen: Eucalyptus dominated tree stand, mixed tree stands and pure native tree stands. A sample plot comprised a main plot of 20m by 10m plot for measuring trees with a diameter at breast height (DBH) ≥ 10 cm, a sub-plot of 10m by 5m nested within the main plot for measuring saplings and shrubs of DBH less than 10cm. Data was collected on tree species type, stem DBH for trees, tree height, counts of trees, saplings and shrubs. The data was subjected to both exploratory and inferential statistical analysis using R Gui Version 4.2.1. Woody species diversity and carbon stocks were subjected to analysis of variance (ANOVA) at 5% significance level. Results: Native dominated tree stands had the highest biomass carbon (0.50-512.84 MgC ha-1) followed by mixed tree stands (0.10-110.82 MgC ha-1). Eucalyptus dominated was the least (0.10-68.58 MgC ha-1). The above ground biomass in the Eucalyptus dominated tree stands and mixed trees stands was significantly lower than in the adjacent native trees stands (p=0.001). The mean carbon estimated in the treatments was 2.62 MgC ha-1 in the Eucalyptus trees dominated stands, 3.09 MgC ha-1 in mixed trees species stands and 19.05 MgC ha-1 in native tree species stand. Implications: Increase in the concentration of Eucalyptus trees led to a reduction in tree diversity. Trees in the Eucalyptus dominated tree stand and mixed trees stand had significantly lower stem diameters, basal area and tree biomass than in the adjacent indigenous trees stand. The fast rate of growth of Eucalyptus trees may have ensured that the trees grow fast at the expense of other woody species due to water and nutrient competition. Conclusion: The study revealed a general trend of increasing biomass carbon with increasing tree size in all the treatments. The majority of large trees were found in native tree stand indicating that they store majority of biomass carbon stocks. Across the treatment, carbon sequestration in the trees was directly related to above ground biomass production. RESUMEN Antecedentes: El cultivo de árboles en las granjas ha contribuido significativamente a aliviar la presión sobre el ecosistema forestal de Kakamega-Nandi. Sin embargo, existe la preocupación de que las especies de eucaliptos se estén convirtiendo en los árboles dominantes en este paisaje y puedan tener efectos adversos en el medio ambiente. Objetivo: Determinar las compensaciones en la selección de especies de árboles y las compensaciones de carbono en fincas en los márgenes del ecosistema forestal Kakamega-Nandi. Metodología: Se empleó un diseño experimental anidado y el área de estudio se dividió en tres bloques centinela de 3x1 km. Se eligieron tres modelos de paisaje diferentes: una parcela de muestra compuesta por una parcela principal de 20 m por 10 m † Work licensed under a CC-BY 4.0 License. https://creativecommons.org/licenses/by/4.0/ ISSN: 1870-0462. Tropical and Subtropical Agroecosystems 26 (2023): #090 Muigai et al., 2023 2 para medir árboles con un diámetro a la altura del pecho (DAP) ≥ 10 cm, una subparcela de 10 m por 5 m anidada dentro de la parcela principal para medir árboles jóvenes y arbustos de DAP inferior a 10 cm. Se recopilaron datos sobre el tipo de especie de árbol, el DAP del tallo de los árboles, la altura de los árboles, el recuento de árboles, árboles jóvenes y arbustos. Los datos se sometieron a análisis estadístico exploratorio e inferencial utilizando R Gui Versión 4.2.1. La diversidad de especies leñosas y las existencias de carbono se sometieron a análisis de varianza (ANOVA) con un nivel de significación del 5 %. Resultado Los rodales de árboles dominados por especies nativas tenían la biomasa de carbono más alta (0.50-512.84 MgC ha-1), seguidos de los rodales de árboles mixtos (0.10-110.82 MgC ha-1). La biomasa dominada por eucaliptos fue la menor (0.10-68.58 MgC ha-1). La biomasa aérea en los rodales de árboles dominados por eucaliptos y en los rodales de árboles especies nativass adyacentes (p=0.001). El carbono medio estimado en los tratamientos fue de 2.62 MgC ha-1 en los rodales dominados por eucaliptos, 3.09 MgC ha-1 en los rodales de especies de árboles mixtos y 19.05 MgC ha-1 en los rodales de especies nativas. Implicaciones: El aumento en la concentración de árboles de eucalipto condujo a una reducción en la diversidad de árboles. Los árboles en la masa arbórea dominada por eucaliptos y en la masa arbórea mixta tenían diámetros de tallo, área basal y biomasa arbórea significativamente más bajos que en la masa arbórea autóctona adyacente. La rápida tasa de crecimiento de los árboles de eucalipto puede haber asegurado que los árboles crecieran rápidamente a expensas de otras especies leñosas debido a la competencia por el agua y los nutrientes. Conclusión: El estudio reveló una tendencia general de aumento del carbono en la biomasa con el aumento del tamaño de los árboles en todos los tratamientos. La mayoría de los árboles grandes se encontraron en rodales de árboles nativos, lo que indica que almacenan la mayoría de las reservas de carbono de la biomasa. En todo el tratamiento, el secuestro de carbono en los árboles estuvo directamente relacionado con la producción de biomasa aérea.
... Based on the obtained estimate of stem volume, we calculated bole total dry weight using a wood density value of 610 kg/m 3 (Olale et al., 2019). The biomass proportion allocated to leaves and branches was estimated based on the allometric equations of Owate et al. (2018). ...
This study was developed in the context of the Provision of Adequate Tree Seed Portfolios (PATSPO) initiative in Ethiopia. PATSPO aims to strengthen the existing tree-seed system by ensuring access to high-quality tree germplasm. Here, we estimate the socioeconomic impact of establishing a breeding seedling orchard (BSO) and distributing quality planting material of the tree Grevillea robusta (grevillea) in Ethiopia. Grevillea is a commercially important and popular agroforestry tree species grown in East African smallholder farms. Our study starts by modelling tree growth with a one-parameter regression fitted to literature-sourced growth characteristics. For the purpose of modelling, we identify three ‘quality scenarios’ (related to the germplasm used) and two ‘planting options’. Based on the model’s outputs, we investigate the effects of increased tree productivity on farmland economy, on the provision of environmental services, and on the wider forestry sector. Findings are outscaled based on the demand for grevillea planting material in Ethiopia and an assumed reach of PATSPO-derived high-quality germplasm. Our growth models indicated that higher than baseline quality scenarios could produce a significant increase in volume (and biomass productivity). This resulted in several-fold increases in the net present value over the production cycle of agroforestry and woodlot plantings, as well as significant benefits in other economic indicators. At the country scale, our analysis estimated that after 50 years the increase in cumulative net present value of on-farm grevillea plantings should be between Birr 2.7 billion and 1.9 billion when using high-quality germplasm compared to an unimproved germplasm baseline, a significant boost (38 Birr = 1 USD at the time of calculations in 2021). We therefore reveal that establishing a grevillea BSO in Ethiopia could produce significant economic returns for tree growers that are much higher than the initial investment that we determine to be required. Furthermore, using BSO germplasm compared to an unimproved germplasm baseline could over 50 years after the BSO’s establishment sequester an extra 1.7 million tonnes of CO2 equivalents annually and achieve an increase in net present value annually of Birr 44 million in roundwood milling into sawnwood. In summary, our current analysis indicated that a focus on grevillea’s germplasm quality is predicted to bring significant economic and environmental benefits in Ethiopia. Our approach to estimate the benefits of using quality germplasm in tree planting represents an advance on previous methods and can be widely applied to a broad range of species, production systems and locations.
... Grevillea robusta is a popular species for farm plantings in the eastern and central Africa highlands including Ethiopia. In Africa, it is grown mainly as shade tree for tea, coffee plantation (Nesper et al., 2017), fuel wood and timber products (Owate et al., 2018). ...
Grevillea robusta is recognized by the pinnate and deeply lobed fernlike leaves, dark green adaxial, silky with whitish, by showy yellowish flowers clustered on and by black curved pod. Techniques of seed dormancy avoidance were written for different species by different authors. However, a combined effect of watering frequency and germination percentage for successful germination of G. robusta seed is scantly documented. Therefore, this study was conducted with the aim of evaluating the effect of mulching and watering frequency on seed germination, height and leaf number. The research design was factorial experiment in the arrangement of eight different treatments with three replications. The plot size was 1m by 1m and the spacing between plot and block were 0.4m and 1m respectively. The frequency of watering (w) and mulching (M) percentage results variation in height and germination percentage. M0% with watering in one day gap (w1), M0% with watering all day (wa), mulching above 75% and no mulching generally delay total germination percentages of seedling. The optimum mulching (%) and frequency of water for rate of normal seed germination was between mulching M25% wa to M50% wa. The optimum mulching and frequency of water for seedling height was attended at M50% wa. Therefore, the germination responses of seed of G. robusta vary as per mulching percentage and watering frequency it has. Further study on how mulching and watering frequency improve the soil microbial activity and temperature during seed germination of G. robusta species on the seedbed across Agroecology is needed.
... Grevillea robusta is a popular species for farm plantings in the eastern and central Africa highlands including Ethiopia. In Africa, it is grown mainly as shade tree for tea, coffee plantation (Nesper et al., 2017), fuel wood and timber products (Owate et al., 2018). ...
Grevillea robusta is recognized by the pinnate and deeply lobed fernlike leaves, dark green adaxial, silky with whitish, by showy yellowish flowers clustered on and by black curved pod. Techniques of seed dormancy avoidance were written for different species by different authors. However, a combined effect of watering frequency and germination percentage for successful germination of G. robusta seed is scantly documented. Therefore, this study was conducted with the aim of evaluating the effect of mulching and watering frequency on seed germination, height and leaf number. The research design was factorial experiment in the arrangement of eight different treatments with three replications. The plot size was 1m by 1m and the spacing between plot and block were 0.4m and 1m respectively. The frequency of watering (w) and mulching (M) percentage results variation in height and germination percentage. M0% with watering in one day gap (w1), M0% with watering all day (wa), mulching above 75% and no mulching generally delay total germination percentages of seedling. The optimum mulching (%) and frequency of water for rate of normal seed germination was between mulching M25% wa to M50% wa. The optimum mulching and frequency of water for seedling height was attended at M50% wa. Therefore, the germination responses of seed of G. robusta vary as per mulching percentage and watering frequency it has. Further study on how mulching and watering frequency improve the soil microbial activity and temperature during seed germination of G. robusta species on the seedbed across Agroecology is needed.
... and with basal area (R 2 = 0.90-0.96). Similar studies on relationship of DBH, height and basal area of above ground biomass (AGB) has also been done widely (Tumwebaze et al. 2013;Owate et al. 2018). ...
Large-scale surface mining are the major causes for ecological disaster at the landscape level, but ecological restoration in post mining areas offers an opportunity to redevelop an ecosystem. The present research programme was undertaken in Panchapatmali Bauxite Mines in Koraput district of Odisha which is one of the biggest mines in Eastern Ghats ecoregion. The above ground biomass (AGB) and soil parameters inside and outside the mines (natural forest) were compared and their interrelationships were also tested at 1% level of significance. For the three dominant species Pinus insularis, Euca-lyptus hybrid and Samenia saman, the regression coefficient (R 2) values for AGB were significant with respect to DBH (R 2 = 0.80-0.90), height (R 2 = 0.35-0.76) and with basal area (R 2 = 0.90-0.96). Species wise, maximum biomass was shown by Pinus insularis followed by Eucalyptus hybrid and Samenia saman which reveals that exotic species have overruled the indigenous species in the plantation areas. An accurate cokriging geospatial model with minimum errors predicted the AGB values to range from 45.6 to 416.4 t/ha compared to the observed biomass range 5.90-507.06 t/ha through the developed regression equation y = 1.003x + 0.24. The overall AGB of the reclaimed area was at par with the natural forest outside the mines. Increasing the pH level of soils, planting indigenous species and increasing green ground cover species will have lesser negative competition with the trees in the reclaimed zone that can restore the fragile ecosystem.
... Accordingly, for Cupressus lusitanica, we used the model by [49] with DBH and height as predictor variables. For Eucalyptus species and Grevillea robusta, models by [50,51] were used, respectively, having DBH and height as predictor variables. The plot-level AGB data in units of kg m −2 were converted to Mg ha −1 (megagrams per hectare) since the data were collected from large plots (1000 m 2 ). ...
Periodic assessment of forest aboveground biomass (AGB) is essential to regulate the impacts of the changing climate. However, AGB estimation using field-based sample survey (FBSS) has limited precision due to cost and accessibility constraints. Fortunately, remote sensing technologies assist to improve AGB estimation precisions. Thus, this study assessed the role of remotely sensed (RS) data in improving the precision of AGB estimation in an Afromontane forest in south-central Ethiopia. The research objectives were to identify RS variables that are useful for estimating AGB and evaluate the extent of improvement in the precision of the remote sensing-assisted AGB estimates beyond the precision of a pure FBSS. Reference AGB data for model calibration and estimation were collected from 111 systematically distributed circular sample plots (SPs) of 1000 m 2 area. Independent variables were derived from Landsat-8, Sentinel-2 and PlanetScope images acquired in January 2019. The area-weighted mean and standard deviation of the spectral reflectance, spectral index and texture (only for PlanetScope) variables were extracted for each SP. A maximum of two independent variables from each image type was fitted to a generalized linear model for AGB estimation using model-assisted estimators. The results of this study revealed that the Landsat-8 model with the predictor variable of shortwave infrared band reflectance and the PlanetScope model with the predictor variable of green band reflectance had estimation efficiency of 1.40 and 1.37, respectively. Similarly, the Sentinel-2 model, which had predictor variables of shortwave infrared reflectance and standard deviation of green leaf index, improved AGB estimation with the relative efficiency of 1.68. Utilizing freely available Sentinel-2 data seems to enhance the AGB estimation efficiency and reduce cost and extensive fieldwork in inaccessible areas.
... These results suggest that the error variance is adequately estimated; the confidence intervals and the estimations of A. lechuguilla AGB are efficient and unbiased [22]. In some cases, validation of equations is directed toward selection of the best statistics for their predictive capacity and, in the best of cases, to distribution of the residuals (e.g., Owate et al. [70]; Moore [71]; Zeng et al. [63]), leaving aside parametric tests that could verify regression assumptions and corroborate efficiency of the coefficients. ...
Quantifying biomass is important for determining the carbon stores in land ecosystems. The objective of this study was to predict aboveground biomass (AGB) of Agave lechuguilla Torr., in the states of Coahuila (Coah), San Luis Potosí (SLP) and Zacatecas (Zac), Mexico. To quantify AGB, we applied the direct method, selecting and harvesting representative plants from 32 sampling sites. To predict AGB, the potential and the Schumacher–Hall equations were tested using the ordinary least squares method using the average crown diameter (Cd) and total plant height (Ht) as predictors. Selection of the best model was based on coefficient of determination (R2 adj.), standard error (Sxy), and the Akaike information criterion (AIC). Studentized residues, atypical observations, influential data, normality, variance homogeneity, and independence of errors were also analyzed. To validate the models, the statistic prediction error sum of squares (PRESS) was used. Moreover, dummy variables were included to define the existence of a global model. A total of 533 A. lechuguilla plants were sampled. The highest AGB was 8.17 kg; the plant heights varied from 3.50 cm to 118.00 cm. The Schumacher–Hall equation had the best statistics (R2 adj. = 0.77, Sxy = 0.418, PRESS = 102.25, AIC = 632.2), but the dummy variables revealed different populations of this species, that is, an equation for each state. Satisfying the regression model assumptions assures that the predictions of A. lechuguilla AGB are robust and efficient, and thus able to quantify carbon reserves of the arid and semiarid regions of Mexico.
