Total Aboveground Dry Biomass Research Articles

Development of site-specific allometric equation and predicting aboveground biomass of natural and plantation forests of Oxytenathera abyssinica (A. Rich.) Munro, Northwestern Ethiopia

Bamboo is an ideal plant for commercial production due to its rapid growth rate, high biomass production, low cost of production and environmental friendliness. Although Ethiopia has the highest bamboo cover in Africa, allometric equations for estimating its biomass are scarce. Most allometric models developed to date have been largely concerned with trees and shrubs. The objective of this study was to generate species- and site-specific allometric models that could be used to estimate the total aboveground dry biomass and culm dry biomass of lowland bamboo in northwest Ethiopia. Three power form-based allometric models were created using diameter at breast height (DBH) and culm height (H) as independent variables. One hundred and eight Oxytenathera abyssinica culms were used to predict the total aboveground biomass and culm biomass. Model one (M1) was the best model to predict the culm and total aboveground biomass of the species, regardless of forest type. The allometric models may provide useful information about aboveground biomass and culm biomass estimation methods to forestry professionals, bamboo producers and other stakeholders, and could help in the calculation of the country’s contribution to global carbon sequestration and trade.

Effect of Combined Application of Vermicompost and NPS Fertilizer Rates on Growth, Yield and Yield Components of Maize (Zea mays L.) at Toke Kutaye District, Ethiopia

Maize is one of the major and important cereal crops in Western Shewa Zone, particularly, in the Toke Kutaye district. However, the yield of the crop is low mainly due to the low fertility status of the soils. Integrated use of vermicompost and NPS fertilizers is indispensable to improve this condition of the soil. In this context, a study was conducted in 2019/2020 to assess the effect of the combined use of vermicompost and NPS fertilizer on yield and yield components of maize. To achieve this objective field experiment was laid out in a randomized complete block design and replicated three times. The results of this study revealed that the current scenarios of maize production in Toke Kutaye district call for appropriate ways of adding nutrients to the soil to obtain optimum maize productivity. In response to this, the combined application of different rates of vermicompost and NPS fertilizer to soil significantly affected most parameters used for this investigation such as plant height, leaf number, leaf length, leaf area, stand count, ear length, and a number of ears per plant, thousand-grain weight, total above-ground dry biomass and grain yield of maize. Moreover, the combined form of NPS blended fertilizer and vermicompost was applied and the result revealed that the sole application of recommended NPS fertilizer and vermicompost increased maize yield by 52.27 and 55.72% over control treatments, respectively. Besides this, the combined use of vermicompost and NPS fertilizer by the rating of half of the recommended rate of both fertilizers increased maize yield by 60.05% over the control treatment. This indicates that the best option for soil fertility management is integrated soil fertility management that involves the combined use of vermicompost and NPS fertilizers as nutrient sources than the strategy of using organic or inorganic amendments alone. Then, it could be concluded that the use of blended NPS fertilizer at 50 kg ha-1with supplemental vermicompost at 5 t ha-1 to Jibat variety is the realistic approach to address the problem of low productivity of maize in the study area and other similar agroecology. Based on the findings and conclusions of this study it can be recommended that farmers in the study area should, therefore, be advised to use this variety and combined use of vermicompost and NPS fertilizer at a rate of 5 t ha-1 VC +50 kg ha-1 NPS for sustainable maize crop production tentatively. Nevertheless, further studies are needed to recommend agronomical optimum and to measure the long-term effects of the integrated soil fertility management techniques in more seasons, soil types and crop varieties before giving a conclusive recommendation.

Simple Allometry To Estimate The Aboveground Tree Biomass For Five Cool-Broadleaved Species Of Bhutan Himalaya

Million tons of carbon was found to be stored in the forest biomass with maximum storage capacity in the broadleaved trees. Developing tree biomass allometric equation being considered fundamental to determine the carbon sequestration potential of tree species. Thus, five broadleaved tree species of Quercus lamellosa, Beilschemidia sikkimensis, Castonopsis hystrix, Persea clerkania and Symplocos sumintia were destructively sampled using Randomized Branch Sampling technique (RBS) to develop allometry for aboveground biomass estimation in cool broadleaved forests in Bhutan. The total of 159 sample trees with minimum 32 trees from each species under different diameter class (5 cm < 90 cm), height class (4 m < 46 m) from four physiographic zones were sampled. The observed total aboveground dry biomass of the trees ranges from 4.12 < 5579.31 kg; 3.62 < 3464.51 kg; 5.99 < 3600.52; 8.89 < 3689.82 kg; kg and 7.08 < 2993.22 kg respectively for above five species. Linear regression was attributed to heteroskedasticity with un-equal distribution of the residual errors. While linearized regression with transformed variables exhibited the best fit line for biomass estimation. Significant prediction of aboveground tree biomass was observed with natural log base transformed linearized power function of DBH -tree height relationships (t (29) = 11.91, 1.63, p ≤ .001) R² = .98) followed by the transformed model of DBH as independent variable (t (30) = 34.31, p ≤ .001) R² = .97). Therefore, the study concluded that, linearized power function with antilog bias correction factor seemed better in predicting aboveground tree biomass of cool broadleaved species in Bhutan

Crop Yield and Essential Oil Composition of Two Thymus vulgaris Chemotypes along Three Years of Organic Cultivation in a Hilly Area of Central Italy.

Thymus vulgaris L. is one of the most commonly used medicinal and aromatic plants (MAPs), owing to a range of therapeutic properties of its essential oil. Plant growth, biomass yield, essential oil content and composition are influenced by chemotype, environmental conditions, cultivation techniques and vegetative development. Since in MAPs cultivation special attention is paid on high quality of raw material, the adoption of sustainable agriculture methods is of pivotal importance. Therefore, we evaluated the agronomic and qualitative performances of two Thymus vulgaris L. chemotypes, organically cultivated under the Mediterranean climate of hilly lands of central Italy for three consecutive years (2017–2019). Along the trial, total above-ground dry biomass significantly increased from the 1st to 3rd year after planting and large variations in the main biological, biometric and productive traits were observed between the two chemotypes. The ‘thymol’ chemotype EO obviously showed thymol as the major constituent (51.26–49.87%) followed by γ-terpinene and p-cymene. The ‘linalool’ chemotype EO showed high percentages of oxygenated monoterpenes (about 90%) with linalool (75%), linalyl acetate (8.15%) and b-caryophyllene (3.2%) as main constituents. This study highlighted that T. vulgaris can be successfully organically grown in the hilly lands of Tuscany, with interesting biomass and essential oil yields, even though the plants were in the initial years of crop establishment (start in 2017). The introduction of this species into organic cultivation systems could contribute to obtain high-quality raw material, as well as to enhance crop rotation diversification, which is of pivotal importance in the management of organic farms.

Effect of deficit irrigation on physiology, plant growth, and fruit yield of cucumber cultivars

Increased water scarcity necessitates the implementation of water-conserving irrigation management practices to sustain crop production,especially in water-limited areas. A two-year field study was conducted during 2019 and 2020 to evaluate the effect of deficit irrigation on physiology, plant growth, and yield of cucumber cultivars. The experiment was conducted in a split-plot design with four irrigation levels (100% ETc (crop evapotranspiration), 80% ETc, 60% ETc, and 40% ETc) as main plot factor and two cultivars (Poinsett 76 and Marketmore 76) as subplot factor with three replications. Results showed that stomatal conductance (gs), transpiration rate (E), photosynthesis rate (Pn), intercellular CO2 concentration (Ci), and leaf area were significantly lower in 60% ETc and 40% ETc compared to 100% ETc while stomatal limitations, intrinsic water use efficiency (WUEi), and relative leaf temperature were significantly higher in 60% ETc and 40% ETc compared to 100% ETc. The observed values of these aforementioned parameters were comparable between 100% ETc and 80% ETc. A decrease in leaf area, as well as a decrease in Pn, resulted in a decline in overall photosynthesis per plant in 60% ETc and 40% ETc compared to 100% ETc. As a consequence of this, plant dry biomass and total fruit yield were significantly lower in 60% ETc and 40% ETc compared to 100% ETc. However, photosynthesis per plant was comparable between 100% ETc and 80% ETc due to comparable Pn and leaf area between them. Because of comparable photosynthesis per plant, plant dry biomass and fruit yield were comparable between 100% ETc and 80% ETc. Marketmore 76 had significantly higher gs, E, Pn, Ci, and leaf area and it had significantly lower stomatal limitations, WUEi, and relative leaf temperature than Poinsett 76. Vegetative dry biomass and total above-ground dry biomass were higher in Marketmore 76 but fruit yield was higher in Poinsett 76. These results suggest that 80% ETc irrigation level and Poinsett 76 cultivar can be recommended for successful cucumber production without causing a significant decline in fruit yield in water-limited Southern High Plains of United States.

Assessing resource use in gerbera genotypes for precision nutrient use in protected condition

The present study was conducted in the existing germplasm block of gerbera under protected condition at ICAR-IIHR, Bengaluru, India during 2017–2019 to obtain comprehensive information on biomass partitioning, nutrient uptake pattern and flower yields in different genotypes for precision use of critical inputs. The number of leaves (187.6–353.2 m−2 yr−1) and flower stalks (166.9–274.5 m−2 yr−1) varied significantly among genotypes. Specific leaf area (SLA) was similar among Balance, Stanza, Arka Aswha and Terra Kalina cultivars (0.150–0.156 cm2 mg−1). Strong positive influence of SLA on number of flower stalks was evident from the significant correlation (r = –0.774). Significant positive correlations among number of flower stalks and leaves, leaf area and SLA substantiate the flower yield pattern in gerbera. Optimum leaf number per plant was estimated at 18.6, while optimum range was quantified at 14.1 to 22.4. In gerbera genotypes, the partitioning of total aboveground dry biomass to leaves and flower stalks was 46–61% and 39–54%, respectively. The average nutrient removal was quantified at 32.8 g N, 7.3 g P, 78.7 g K, 24.7 g Ca and 4.1 g Mg m−2 yr−1 and the uptake of macronutrients was in the order of K > N > Ca > P > Mg. The order of micronutrient removal (g m−2 yr−1) was Fe (0.2), Zn (0.08), Mn (0.06) and Cu (0.03). The soil fertility status at uniform management was above optimum. It is clear that leaf number, biomass partitioning and nutrient removal pattern had direct impact on flower stalk yields of gerbera.

Allometric equations for total aboveground dry biomass and carbon content of Pinus occidentalis trees

Although precise species-specific aboveground tree biomass equations are needed in the Dominican Republic to quantify potential carbon storage in the context of climate change and sustainable forest management, there has been a lack of available information concerning total aboveground biomass and/or carbon content for naturally occurring Pinus occidentalis trees. The objectives of the study were to develop species-specific allometric biomass models for P. occidentalis, as well as to assess variation in carbon concentration among stem plus bark, branches and foliage by means of chemical analyses. Predictor variables included diameter at breast height (DBH) and total tree height (H), alone and in combination. Model fitting methods employing linear and nonlinear regression techniques were used and evaluated based on goodness-of-fit criteria. Two competing biomass models produced similar goodness-of-fit statistics: model 4, fitted by the Weighted Non-linear Least Squares technique, , and model 6, fitted by modeling the variance component and applying the Maximum Likelihood method, . Average carbon concentration (%) was highest in foliage tissue (49.8%), followed by branches (46.37%) and, lastly, stem plus bark (45.95%). On average, each individual tree is storing 175 kg of total aboveground carbon. To our knowledge, this is the first account reporting carbon fraction for this tropical species. Calculated wood carbon fractions from the study can be easily incorporated into forest C accounting, and may reduce errors in forest C valuations, which nowadays are performed using global estimates published elsewhere.

Assessing forest availability for wood supply in Europe

The quantification of forests available for wood supply (FAWS) is essential for decision-making with regard to the maintenance and enhancement of forest resources and their contribution to the global carbon cycle. The provision of harmonized forest statistics is necessary for the development of forest associated policies and to support decision-making. Based on the National Forest Inventory (NFI) data from 13 European countries, we quantify and compare the areas and aboveground dry biomass (AGB) of FAWS and forest not available for wood supply (FNAWS) according to national and reference definitions by determining the restrictions and associated thresholds considered at country level to classify forests as FAWS or FNAWS.FAWS represent between 75 and 95 % of forest area and AGB for most of the countries in this study. Economic restrictions are the main factor limiting the availability of forests for wood supply, accounting for 67 % of the total FNAWS area and 56 % of the total FNAWS AGB, followed by environmental restrictions. Profitability, slope and accessibility as economic restrictions, and protected areas as environmental restrictions are the factors most frequently considered to distinguish between FAWS and FNAWS. With respect to the area of FNAWS associated with each type of restriction, an overlap among the restrictions of 13.7 % was identified. For most countries, the differences in the FNAWS areas and AGB estimates between national and reference definitions ranged from 0 to 5 %. These results highlight the applicability and reliability of a FAWS reference definition for most of the European countries studied, thereby facilitating a consistent approach to assess forests available for supply for the purpose of international reporting.

Improving resilience of an old-growth urban forest in Southern Italy: Lesson(s) from a stand-replacing windstorm

There is a current concern that the capacity of urban forests to recover from the effects of climate change may be diminishing. New management options are needed so that they can continue to provide ecosystem services to local communities. After a windstorm occurred on June 2014 pre- and post-disturbance stand conditions (years 2010 and 2015, respectively) of the historical old-growth holm oak forest of Parco Gussone were analysed by combining ground- and satellite-based methodologies. Results highlighted that Parco Gussone was primarily valued for its historical importance and, despite the phytosanitary conditions of the trees, no silvicultural treatments were made since 1986, most probably due to conflicts arisen between different stakeholders. Therefore in 2014, the windstorm damaged 406 trees (8.1% of the total aboveground forest dry biomass) and it was stand-replacing on 1.53 ha (9.3 % of the total forest area). Windthrows, heterogeneously distributed and unequally sized (103 canopy gap ranging between ∼6 to 1632 m2), caused, overall, a significant reduction of LAI (∼19%). The presence of large gaps promoted the invasion of non-native herbaceous species whereas native species of the shrubs and herbaceous layers were favoured when felled trees were left on the ground or removed mechanically during harvest, respectively. In this context, urban forests should be considered as ‘complex adaptive systems’, therefore natural processes can be simulated by applying a ‘close-to-nature’ silviculture (e.g. by opening small gaps), vulnerability assessed (e.g. using a tree-by-tree VTA), biodiversity and ecological resilience improved and short- and long term disturbance effects evaluated (e.g. analysis of disturbance attributes and stand dynamics) so that specific conservation goals can be adapted to a specific landscape and biotic community. By implementing and applying the proposed guidelines in urban forest planning, we are confident that the resilience of those Mediterranean urban forest ecosystems could be effectively restored and improved.

Allometric Equations to Estimate Sugarcane Aboveground Biomass

Sugarcane harvest implies in the movement of very large amounts of biomass and, therefore, demands careful planning of logistics. Accurate pre-harvest estimation of sugarcane field productivity provides useful data to plan harvest, transportation, selling and industrial processing activities. Currently, the estimation of sugarcane biomass in the field is based on destructive techniques. The use of allometric equations is an adequate, nondestructive tool to provide this information, but these equations are scarcely available for sugarcane. We created regression models to estimate stem fresh (SFB, kg) and total aboveground dry biomass (AB, kg) based on plant height (H, cm) and diameter (D, cm), for different Brazilian sugarcane varieties. The models adequately estimated biomass for all sugarcane varieties. Based on that, we developed two general equations valid for all varieties: SFB = 0.046 H × D1.5647 and AB = 0.4001 H × D1.0743. To calculate biomass per hectare, SFB and AB must be multiplied by the average number of stems in the row (N) and divided by row spacing (S). In our study site, N was adequately estimated counting stems in four 100-m row segments. Overall, precise estimates of stem and whole plant biomass for sugarcane can be obtained using the general equations and the number of stems per area. We believe these equations are also useful to estimate biomass for other sugarcane varieties around the world, considering the simplicity of sugarcane plant structure.

Nutrient Utilization and Yield Response of Lentil (<i>Lens culinaris</i> Medikus) to <i>Rhizobium</i> Inoculant and Sulphur Fertilization

Lentil (Lens culinaris Medikus) is a major food crop in Ethiopian. It is affordable protein source and important in sustaining soil fertility through nitrogen fixation. However, its current national productivity of 1.46 t ha-1 is lower than its potential due to inadequate agronomic management practices, nutrient imbalance and lack of indigenous or commercial Rhizobium strains of lentil. Therefore, the field experiment was conducted at Ada’a district under rain-fed condition during 2016/17 main cropping season to assess the role of S and Rhizobium inoculant on nodulation, nutrient utilization and yield response of lentil. The experiment consisted of three levels of S (0, 20 and 40 kg ha-1) and Rhizobium inoculant (un-inoculated and inoculated) in a factorial combination using Alemaya lentil variety as a test crop. The experiment was conducted using randomized complete block design with three replications. The result showed the interaction of sulphur fertilization and Rhizobium inoculant were significant on days to flowering, number of nodules plant-1, nodule dry weight plant-1, number of seeds pod-1, aboveground dry biomass, seed yield, seed S uptake, haulm S uptake, total S uptake, sulphur agronomic and recovery efficiency as well as sulphur harvest index. Application of 40 kg S ha-1 without Rhizobium inoculant led to produce the highest seed yield (2.27 t ha-1) and delayed days to flowering (46 days) of lentil whereas, the highest nodule dry weight plant-1 (1.1mg) and sulphur harvest index (17.68%) were obtained at the rate of 40 kg S ha-1under Rhizobium inoculations. On the other hand the maximum number of nodule plant-1 (15.60), number of seed pod-1 (1.99), total aboveground dry biomass (8.22 t ha-1), Sulphur agronomic efficiency (32.11kg ha-1), sulphur recovery efficiency (66.00 kg ha-1) were obtained in response to sulphur application at 20 kg ha-1 under Rhizobium inoculations. Moreover, Rhizobium inoculation without S fertilization gave the highest seed (3.88kg ha-1), haulm (23.33kg ha-1) and total S uptake (24.89 kg ha-1). Rhizobium inoculation without S application had high net benefit, relatively low variable cost with an acceptable and maximum MRR for lentil production in Ada'a district. However, since the experiment was conducted only for one season and one site, repeating the trial at different sites as well as in the same trial site would be important in order to draw sound recommendation.

Can mulching of maize straw complement deficit irrigation to improve water use efficiency and productivity of winter wheat in North China Plain?

Improving resource-use efficiency is vital for sustainable agricultural production and food security in water-scarce regions such as North China Plain. The aim of this study was to assess the effects of irrigation and straw-mulch on accumulated intercepted photosynthetically active radiation (AIPAR), radiation-use efficiency (RUE) and water-use efficiency (WUE) of wheat. A two-factorial field experiment was carried out at Luancheng Research Station (China) during 2015–16 and 2016–17. The factors included three irrigation levels – full (FI), deficit (DI) and partial root-zone drying (PRD), which besides rainfall received 200, 100 and 100 mm of irrigation, respectively, and two mulching strategies – mulch and no-mulch: ∼8 and 0 Mg ha−1, respectively. The results showed that mulch reduced AIPAR (6–11%) and increased RUE for total aboveground dry biomass (3–9%). Mulch affected intercepted photosynthetically active radiation (IPAR) between the tillering and anthesis stages, largely because of reduced soil surface temperature (0.8–1.5 °C), which led to delayed growth/development and impaired light interception. No significant difference was observed between DI and PRD for grain yield; however, effects on WUE varied during the two seasons. DI led to higher WUE during season I compared to PRD, while PRD resulted in highest WUE during season II. AIPAR was reduced under DI and PRD; however, RUE remained unaffected for irrigation treatments. The complementary effects of mulch were observed only under DI where WUE was increased by 4–6%. The results imply that the PRD irrigation under field conditions is not as effective as it has been anticipated, especially in soils with high clay content. Mulch induced reduction in growth/development tends to nullify its positive effects through water conservation. Taken together, these results reiterate the need to further optimize mulching and PRD irrigation practices before recommending their use under field conditions, especially for small grain cereals.

A coupled hydrological-plant growth model for simulating the effect of elevated CO2 on a temperate grassland

Elevated CO2 (eCO2) reduces transpiration at the leaf level by inducing stomatal closure. However, this water saving effect might be offset at the canopy level by increased leaf area as a consequence of eCO2 fertilization. To investigate this bi-directional effect, we coupled a plant growth and a soil hydrological model. The model performance and the uncertainty in model parameters were checked using a 13year data set of a Free Air Carbon dioxide Enrichment (FACE) experiment on grassland in Germany. We found a good agreement of simulated and observed data for soil moisture and total above-ground dry biomass (TAB) under ambient CO2 (∼395ppm) and eCO2 (∼480ppm). Optima for soil and plant growth model parameters were identified, which can be used in future studies. Our study presents a robust modelling approach for the investigation of effects of eCO2 on grassland biomass and water dynamics. We show an offset of the stomatal water saving effect at the canopy level because of a significant increase in TAB (6.5%, p<0.001) leading to an increase in transpiration by +3.0±6.0mm, though insignificant (p=0.1). However, the increased water loss through transpiration was counteracted by a significant decrease in soil evaporation (−2.1±1.7mm, p<0.01) as a consequence of higher TAB. Hence, evapotranspiration was not affected by the increased eCO2 (+0.9±4.9mm, p=0.5). This in turn led to a significantly better performance of the water use efficiency by 5.2% (p<0.001). Our results indicate that mown, temperate grasslands can benefit from an increasing biomass production while maintaining water consumption at the +20% increase of eCO2 studied.

Arbuscular Mycorrhizal Fungi Enhance Plant Diversity, Density and Productivity of Spring Ephemeral Community in Desert Ecosystem

Arbuscular mycorrhizal (AM) fungi form intimate associations with the roots of about 85% of all terrestrial plants, and can greatly increase a plant’s uptake of soil nutrients and have been shown to influence plant diversity in several ecosystems. A lot of studies have reported the effect of arbuscular mycorrhizas on plant density, species diversity, richness and productivity in desert herbland in Gurbantonggut desert, China. Here, we conduct a mycorrhizal functional study by suppressing AM fungi by applying the fungicide benomyl as a soil drench in soil cores and field in-situ experiment. The mycorrhiza-responsiveness of the dominant species Erodium oxyrrhynchum is assessed in intact soil cores containing the indigenous AM fungi. The soil-cores experiment displayed E. oxyrrhynchum to have a significant positive shoot and root growth response, and this is in response to the abundance of the indigenous AM fungal colonisation. The field experiment indicates the total aboveground dry biomass is negatively influenced by the suppression of AM fungi, though, no significant effect produced in the dominant and common plant species. The fungal suppression also affected density, species diversity and richness. The density of non-mycorrhizal plant Alyssum linifolium increases significantly in the treatment of suppressed AM fungi. The spore density decreases significantly in benomyl-treated plots. Our results showed that AM fungi were very important in desert ecosystem for the maintaining of plant biodiversity, richness and productivity.

Hybrid three-phase estimators for large-area forest inventory using ground plots, airborne lidar, and space lidar

Previous studies have utilized ground plots, airborne lidar scanning or profiling data, and space lidar profiling data to estimate biomass across large regions, but these studies have failed to take into account the variance components associated with multiple models because the proper variance equations were not available. Previous large-domain studies estimated the variances of their biomass density estimates as the sum of the GLAS sampling variability plus the model variability associated with the models that predict airborne lidar estimates of biomass density (Y) as a function of satellite lidar measurements (X). This approach ignores the additional variability associated with the predictive models used to estimate ground biomass density as a function of airborne lidar measurements. This paper addresses that shortcoming. Analytic variance expressions are provided that include sampling variability and model variability in situations where multiple models are employed to generate estimates of biomass. As an example, the forest biomass of the continental US is estimated, by forest stratum within state, using a space lidar system (ICESat/GLAS). An airborne laser system (ALS) is used as an intermediary to tie the GLAS measurements of forest height to a small subset of US Forest Service (USFS) ground plots by flying the ALS over the ground plots and, independently, over individual GLAS footprints. Two sets of models are employed to relate satellite measurements to the ground plots. The first set of equations relates USFS ground plot estimates of total aboveground dry biomass density (Y1) to spatially coincident ALS forest canopy measurements (X1). The second set of models predicts those ALS canopy height measurements (X1) used in the first set of models to GLAS waveform measurements (X2). The following important conclusions are noted. (1) The variability associated with estimation of the plot-ALS model coefficients is significant and should be included in the overall estimate of biomass density variance. In the continental US, the total variance of mean forest biomass density (98.06t/ha) increases by a factor of 3.6×, i.e., from 1.91 to 6.94t2/ha2, when plot-ALS model variance is included in the calculation of total variance. (2) State-level results are more variable, but on average, the percent model variance at the state level, i.e., (model variance/total variance)∗100, increases from 16% to 59% when plot-ALS model variance is included. (3) The overall model variance is driven in large part by the number of plots overflown by the ALS and the number of GLAS pulses overflown by the ALS. Given a choice of improving precision by either increasing the number of plot-ALS observations or increasing ALS-GLAS observations, there is no obvious benefit to selecting one over the other. However, typically the number of ground plots overflown is the limiting factor. (4) If heteroskedasticity is evident in either the ground-air or air-satellite models, it can modeled using weighted regression techniques and incorporated into these model variance formulas in straightforward fashion. The results are unambiguous; in a hybrid three-phase sampling framework, both the ground-air and air-satellite model variance components are significant and should be taken into account.

Improving biomass estimation in a Populus short rotation coppice plantation

Short Rotation Coppice (SRC) plantations are important to biomass supply in the biomass market. The biomass stocks estimations should be based on robust models that allow the most accurate estimations. We have evaluated the changes in allometry for the estimation of biomass production at individual stool level in a short rotation, high density poplar plantation under a coppice system during two rotations of three years. The plantation was established in central-northern Spain, with a density of 17,316 stools ha−1. The influence of different factors in the allometry has been evaluated to improve the methodology for more robust biomass prediction. In an SRC system, the influence of age was more pronounced in the first year after each coppicing than in subsequent years of the cycle. Our findings suggest that this feature of nature must be accommodated in the modelling procedure either through the model formulation (decreasing the parameter variability with the inclusion of age as a dummy predictor variable) or by selecting the sample according to the stage of development of the above-ground biomass (which will depend on the goals of the predictions). The minimum sample size proposed to construct a model capable of predicting biomass regardless of age in SRC was 50 trees. Furthermore, the uncertainty was quantified in two models for total above-ground dry woody biomass, the first based only on the basal diameter and the other on the basal diameter along with the number of shoots per stool; the inclusion of the latter was advisable to increase the accuracy and reduce the mean deviation in biomass predictions at different ages.

Detection of diversity and stand parameters in Mediterranean forests using leaf-off discrete return LiDAR data

A methodological approach based on detailed land-use map, high-resolution LiDAR data and field surveys was developed to categorize productive and non-productive mixed forests, both in term of stand attributes and structural diversity. In 2011, leaf-off dedicated airborne LiDAR data were collected in a 20,000ha inland patchy area which was representative of soil land use in the Apennines mountains of southern Italy. By combining field and LiDAR data in 5574ha of forests with coexisting evergreen and deciduous species, we modelled common forest stand variables (height, diameter, volume and biomass) with high accuracy (0.60≤Adj.R2≤0.89). Moreover, a moderate correlation (0.425≤τ≤0.462) between field- and LiDAR-derived diversity indices was found. About 3393ha of forests are enclosed in protected areas of the Natura 2000 network, which in turn possesses 77% (~576,286Mg) of total aboveground dry biomass. Overall, eight forest types were identified, one of which, the European beech, is only found in the Natura 2000 sites, while other forest types are also found elsewhere. This is the first study to undertake a LiDAR analysis of Mediterranean forests in the Campania Region and might help better evaluate trade-off, especially in protected areas, in order to enhance multiple benefits and support sustainable management of forests.

Lidar-based estimates of aboveground biomass in the continental US and Mexico using ground, airborne, and satellite observations

Existing national forest inventory plots, an airborne lidar scanning (ALS) system, and a space profiling lidar system (ICESat-GLAS) are used to generate circa 2005 estimates of total aboveground dry biomass (AGB) in forest strata, by state, in the continental United States (CONUS) and Mexico. The airborne lidar is used to link ground observations of AGB to space lidar measurements. Two sets of models are generated, the first relating ground estimates of AGB to airborne laser scanning (ALS) measurements and the second set relating ALS estimates of AGB (generated using the first model set) to GLAS measurements. GLAS then, is used as a sampling tool within a hybrid estimation framework to generate stratum-, state-, and national-level AGB estimates. A two-phase variance estimator is employed to quantify GLAS sampling variability and, additively, ALS-GLAS model variability in this current, three-phase (ground-ALS-space lidar) study. The model variance component characterizes the variability of the regression coefficients used to predict ALS-based estimates of biomass as a function of GLAS measurements. Three different types of predictive models are considered in CONUS to determine which produced biomass totals closest to ground-based national forest inventory estimates - (1) linear (LIN), (2) linear-no-intercept (LNI), and (3) log-linear. For CONUS at the national level, the GLAS LNI model estimate (23.95±0.45Gt AGB), agreed most closely with the US national forest inventory ground estimate, 24.17±0.06Gt, i.e., within 1%. The national biomass total based on linear ground-ALS and ALS-GLAS models (25.87±0.49Gt) overestimated the national ground-based estimate by 7.5%. The comparable log-linear model result (63.29±1.36Gt) overestimated ground results by 261%. All three national biomass GLAS estimates, LIN, LNI, and log-linear, are based on 241,718 pulses collected on 230 orbits. The US national forest inventory (ground) estimates are based on 119,414 ground plots. At the US state level, the average absolute value of the deviation of LNI GLAS estimates from the comparable ground estimate of total biomass was 18.8% (range: Oregon, −40.8% to North Dakota, 128.6%). Log-linear models produced gross overestimates in the continental US, i.e., >2.6x, and the use of this model to predict regional biomass using GLAS data in temperate, western hemisphere forests is not appropriate. The best model form, LNI, is used to produce biomass estimates in Mexico. The average biomass density in Mexican forests is 53.10±0.88t/ha, and the total biomass for the country, given a total forest area of 688,096km2, is 3.65±0.06Gt. In Mexico, our GLAS biomass total underestimated a 2005 FAO estimate (4.152Gt) by 12% and overestimated a 2007/8 radar study's figure (3.06Gt) by 19%.

Biomass partition and productive aptitude of wild and cultivated cardoon genotypes (Cynara cardunculus L.) in a marginal land of Central Italy

A very limited number of field studies have addressed the suitability of Cynara cardunculus L. genotypes to local environmental conditions in terms of productive aptitude.Four genotypes of Cardoon, under low input conditions (reduced nitrogen fertilization and rainfed conditions) were compared in a marginal land of Central Italy during the 2012–2014 period: two cultivated (CDL07 and Gigante) and two wild cardoon genotypes (RCT10 and Tolfa). At the ripening stage of capitula, all plant components were weighed separately, yields were calculated, and biometric traits were measured. Genotypes showed different productive aptitudes and suitability to the pedo-climatic conditions of growth. The total aboveground dry biomass per plant ranged between 114.4 and 353.6g with variable values within genotypes and years, whereas the partition of the aboveground biomass was strongly affected by genotypes only. Analysis of variance (ANOVA) showed a general prevalent influence of the genotype factor on crop yields. Capitula components were of greatest importance in cultivated cardoons, but strongly affected by the annual climatic trends. The maximum achenes yield was in 2012 with 3.2tha−1 as a mean of the cultivated cardoons, whereas the wild genotype Tolfa reached a mean production of 2.1tha−1.In general the wild genotype RCT10 demonstrated a poor adaptability to the conditions of the experimental site. On the other hand, wild genotype Tolfa might be incorporated into the local cropping systems as an industrial or bioenergy crop, due the low management inputs required, its adaptability to the local conditions, and the fairy good aboveground biomass and achenes production.

Weed Management, Training, and Irrigation Practices for Organic Production of Trailing Blackberry: III. Accumulation and Removal of Aboveground Biomass, Carbon, and Nutrients

Relatively little is known about aboveground nutrient content of organic blackberry, and there is no published work on total carbon (C) content. Treatment effects on biomass, C, and nutrient content, accumulation, and removal were assessed over 2 years in a mature organic trailing blackberry (Rubus L. subgenus Rubus, Watson) production system that was machine harvested for the processed market. Treatments included two irrigation options (no irrigation after harvest and continuous summer irrigation), three weed management strategies (weed mat, hand-weeded, and nonweeded), and two primocane training times (August and February) in two cultivars (Black Diamond and Marion). Floricanes comprised an average of 45% of the total aboveground plant dry biomass, while primocanes and fruit comprised 30% and 25%, respectively. Depending on the treatment, the total aboveground dry biomass accumulation over the course of the season was 5.0–6.5 t·ha−1 per year, while C stock of the planting was an estimated 0.4–1.1 t·ha−1 in late winter. Carbon accounted for ≈50% of the dry biomass of each aboveground plant part, including primocanes, floricanes, and fruit. Weed management had the largest impact on plant biomass and nutrient content. No weed control reduced aboveground dry biomass, the content of nutrients in the primocanes, floricanes, and fruit, and the annual accumulation of dry biomass and nutrients, whereas use of weed mat resulted in the most dry biomass and nutrient content. Nutrient accumulation was similar between the cultivars, although February-trained ‘Marion’ plants had a greater removal of most nutrients in 2014 than the year prior. The amount of nitrogen (N) removed in the fruit was 22, 18, and 12 kg·ha−1 for weed mat, hand-weeded, and nonweeded plots, respectively, in 2013. In 2014, ‘Marion’ and ‘Black Diamond’ differed in N removed in harvested fruit when grown with weed mat at 18 and 24 kg·ha−1, respectively, whereas there was no cultivar effect when plants were grown in hand-weeded or nonweeded plots. Plots with weed mat tended to have the most nutrients removed through harvested fruit in both years. In 2014, N removal from August-trained ‘Marion’ was 5 kg·ha−1 N less than the other training time and cultivar combinations. Plants that were irrigated throughout the summer accumulated more dry biomass, N, potassium (K), magnesium (Mg), sulfur (S), boron (B), and copper in one or both years than those that received no irrigation after fruit harvest. The irrigation treatment had inconsistent effects on nutrient content of each individual plant part between the two years. Removal of nutrients was often higher than what was applied through fertilization, especially for N, K, and B, which would eventually lead to depletion of those nutrients in the planting.