Herbaceous Crops Research Articles

Investigating the Relationship between X-Band SAR Data from COSMO-SkyMed Satellite and NDVI for LAI Detection

Monitoring spatial and temporal variability of vegetation is important to manage land and water resources, with significant impact on the sustainability of modern agriculture. Cloud cover noticeably reduces the temporal resolution of retrievals based on optical data. COSMO-SkyMed (the new Italian Synthetic Aperture RADAR-SAR) opened new opportunities to develop agro-hydrological applications. Indeed, it represents a valuable source of data for operational use, due to the high spatial and temporal resolutions. Although X-band is not the most suitable to model agricultural and hydrological processes, an assessment of vegetation development can be achieved combing optical vegetation indices (VIs) and SAR backscattering data. In this paper, a correlation analysis has been performed between the crossed horizontal-vertical (HV) backscattering (s°HV) and optical VIs (VIopt) on several plots. The correlation analysis was based on incidence angle, spatial resolution and polarization mode. Results have shown that temporal changes of s°HV (Δs°HV) acquired with high angles (off nadir angle; θ > 40°) best correlates with variations of VIopt (ΔVI). The correlation between ΔVI and Δs°HV has been shown to be temporally robust. Based on this experimental evidence, a model to infer a VI from s° (VISAR) at the time, ti + 1, once known, the VIopt at a reference time, ti, and Δs°HV between times, ti + 1 and ti, was implemented and verified. This approach has led to the development and validation of an algorithm for coupling a VIopt derived from DEIMOS-1 images and s°HV. The study was carried out over the Sele plain (Campania, Italy), which is mainly characterized by herbaceous crops. In situ measurements included leaf area index (LAI), which were collected weekly between August and September 2011 in 25 sites, simultaneously to COSMO-SkyMed (CSK) and DEIMOS-1 imaging. Results confirm that VISAR obtained using the combined model is able to increase the feasibility of operational satellite-based products for supporting agricultural practices. This study is carried out in the framework of the COSMOLAND project (Use of COSMO-SkyMed SAR data for LAND cover classification and surface parameters retrieval over agricultural sites) funded by the Italian Space Agency (ASI).

Pollen and sediment evidence for late-Holocene human impact at the Seonam-dong archeological site, Gwangju, Korea

We present pollen and sediment evidence for late-Holocene human impact from the Seonam-dong archeological site in Gwangju in southwest Korea. Due to the lack of undisturbed profiles with high sedimentation rates, the relationship between the environment and agricultural activities has not been properly investigated in Korea using a paleoenvironmental approach. This study shows possible climate-induced changes in chestnut production, which was contemporaneously recognized by the Chinese as an important and unique local food source in southwestern Korea. Our results also show that human adaptation to climate change may have resulted in both the degradation and recovery of the local forest ecosystem in the study area. The data from the Seonam-dong archeological site provided evidence supporting the following hypotheses. 1) Chestnut cultivation declined from 400 BC to AD 200 (2350–1750cal BP), as herbaceous crop production may have sufficiently expanded to sustain the population, possibly due to agricultural improvements and/or climatic amelioration. 2) Chestnut cultivation was enhanced from AD 200 to AD 800 (1750–1150cal BP), probably to compensate for decreased herbaceous crop yields due to climatic deterioration. 3) The increase in chestnut cultivation led to forest disturbance and increased flooding, with intermittent forest recovery during periods of decreased cultivation.

Management of Insect and Mite Resistance in Ornamental Crops

Resistance of arthropods to crop management chemicals has been problematic since the early era of synthetic organic pesticides. During the 1970s and early 1980s leafminer outbreaks heavily damaged herbaceous ornamental crops such as chrysanthemum, gypsophila, aster, and marigold in fields, shade houses and greenhouses. Several effective insecticides including organophosphates, carbamates, pyrethroids, and a triazine were identified for leafminer control during the outbreak; however, control was short-lived as the leafminer developed resistance to each insecticide. This 11-page fact sheet was written by James F. Price, Elzie McCord, Jr., and Curtis Nagle, and published by the UF Department of Entomology and Nematology, November 2012.
 http://edis.ifas.ufl.edu/in715

Investigating seed dormancy in switchgrass (Panicum virgatum L.): understanding the physiology and mechanisms of coat-imposed seed dormancy

Switchgrass (Panicum virgatum L.), a perennial warm-season grass established by seed has been recommended by the US Department of Energy as a model herbaceous biofuel crop. Neoteric seeds may be dormant resulting in delayed and sporadic germination and emergence, jeopardizing establishment of a good plant stand. Switchgrass dormancy may be alleviated by mechanical or chemical scarification, stratification, and after-ripening, suggesting physical and/or physiological dormancy. The underlying mechanisms and physiology of dormancy in these seeds; however, are not well understood. This work investigates the physiology of switchgrass seed dormancy; first by identifying the contribution of the different switchgrass structures (glumes, lemma, palea, pericarp/testa, endosperm) on regulating germination, and then by testing specific mechanisms of coat-imposed dormancy. We sequentially removed structures of freshly harvested seeds of two upland (Cave-in-Rock, Trailblazer) and two lowland (Alamo, Kanlow) cultivars. The main structure inhibiting germination was the pericarp/testa, with the lemma and palea (bracts) having a secondary effect that differed by genotype. Seeds with glumes and bracts removed, and pericarp/testa cut with endosperm either attached or removed just above the embryo, resulted in high germination percentages and rate, indicating no morphological dormancy, and no effect of the endosperm on germination. The lemma, palea, and pericarp/testa were neither a barrier for water uptake nor contained inhibitory compounds. By adjusting the oxygen concentration of the environment and the physical integrity of the covering structures, we found the enclosing structures acted as barriers to oxygen. Puncturing the pericarp/testa of seeds with glumes and bracts removed, enhanced germination at 1, 10, 21 or 100% oxygen. Combined results showed that the structural integrity of the pericarp/testa (primary) and lemma/palea (secondary) influenced germination, suggesting an important mechanical effect of these layers as barriers for radicle protrusion. Therefore, a combination of seed-coat mechanisms regulates germination in switchgrass seeds.

Switchgrass Genomic Diversity, Ploidy, and Evolution: Novel Insights from a Network-Based SNP Discovery Protocol

Switchgrass (Panicum virgatum L.) is a perennial grass that has been designated as an herbaceous model biofuel crop for the United States of America. To facilitate accelerated breeding programs of switchgrass, we developed both an association panel and linkage populations for genome-wide association study (GWAS) and genomic selection (GS). All of the 840 individuals were then genotyped using genotyping by sequencing (GBS), generating 350 GB of sequence in total. As a highly heterozygous polyploid (tetraploid and octoploid) species lacking a reference genome, switchgrass is highly intractable with earlier methodologies of single nucleotide polymorphism (SNP) discovery. To access the genetic diversity of species like switchgrass, we developed a SNP discovery pipeline based on a network approach called the Universal Network-Enabled Analysis Kit (UNEAK). Complexities that hinder single nucleotide polymorphism discovery, such as repeats, paralogs, and sequencing errors, are easily resolved with UNEAK. Here, 1.2 million putative SNPs were discovered in a diverse collection of primarily upland, northern-adapted switchgrass populations. Further analysis of this data set revealed the fundamentally diploid nature of tetraploid switchgrass. Taking advantage of the high conservation of genome structure between switchgrass and foxtail millet (Setaria italica (L.) P. Beauv.), two parent-specific, synteny-based, ultra high-density linkage maps containing a total of 88,217 SNPs were constructed. Also, our results showed clear patterns of isolation-by-distance and isolation-by-ploidy in natural populations of switchgrass. Phylogenetic analysis supported a general south-to-north migration path of switchgrass. In addition, this analysis suggested that upland tetraploid arose from upland octoploid. All together, this study provides unparalleled insights into the diversity, genomic complexity, population structure, phylogeny, phylogeography, ploidy, and evolutionary dynamics of switchgrass.

Giant reed (Arundo donax L.) harvesting system, an economic and technical evaluation

The giant reed is a herbaceous energy crop that demonstrates a good adaptability for areas of central-northern Italy. However, its size and stem resistance to cutting pose problems for harvesting in relation both to the availability of suitable machinery and costs of the operation. A technical and economic evaluation has been conducted of a harvesting system based on an experimental machine, the biotriturator, developed by University of Bologna in collaboration with the Nobili Company (Bologna, Italy) and adapted to field operating conditions. The harvesting system consists of cutting-shredding and baling in a single pass. The system was evaluated by performing a winter harvest when the crop was in quiescence and had a low moisture content. The total harvesting costs were evaluated as 11.6 € Mg-1 dry biomass. Given that the estimated area that can be covered by the harvesting system was 123 hectares per year the system represents an effective solution for not very large areas and is therefore suitable for the Italian environment where average farm sizes are slightly over seven hectares (ISTAT, 2011).

Evaluation of herbaceous crops irrigated with treated wastewater for ethanol production

The competition for freshwater between agricultural, industrial, and civil uses has greatly increased in Mediterranean basin characterized by prolonged dry seasons. The aim of this study was to evaluate biomass production and the potential ethanol production of promising “no-food” herbaceous crops irrigated with low quality water at different ETc restitutions (0%, 50 and 100%). The research was carried out, in 2011 and 2012, in an open field near the full-scale constructed wetland (CW) municipal treatment plant located in the Eastern Sicily (Italy). The CW effluent has been applied in a experimental irrigation field of Vetiveria zizanoides (L.) Nash, Miscanthus x giganteus Greef et Deu. and Arundo donax (L.). Physical, chemical and microbiological analyses were carried out on wastewater samples collected at inlet and outlet of CW and pollutant removal efficiencies were calculated for each parameter. Bio-agronomical analysis on herbaceous species were made with the goal to evaluate the main parameters such as the plant dimension, the growth response and the biomass production. Biomass dry samples were processed with a three-step chemical pretreatment, hydrolysed with a mix of commercial enzymes and next fermented to obtain the yield of ethanol production. Average TSS, COD and TN removal for CW were about 74%, 67% and 68%, respectively. Although the satisfactory Escherichia coli removal, about 3.5 log unit for both beds on average, CW didn’t achieve the restrictive Italian law limits for wastewater reuse. As expected, irrigation was beneficial and the full ET replenishment increase the biomass productivity as compared to the other two treatment. The mean productivity of Vetiveria zizanoides and Myscanthus x giganteus were about 9, 26 and 38 t ha–1 and 3, 7 and 12 t ha–1 respectively in 0%, 50% and 100% ETc restitutions. Arundo donax gave higher values of dry biomass (78 t ha–1 in 100% ETc restitution in 2011 season), and potential ethanol production (about 3,744 kg ha–1). These results suggest the interest in the use of constructed wetland effluents for the irrigation of energy crops to obtain second generation ethanol, particularly in semiarid regions such as the Mediterranean area.

Land Cover Map Delineation, for Agriculture Development, Case Study in North Sinai, Egypt Using SPOT4 Data and Geographic Information System

Land cover map for a part of North Sinai was produced using the FAO—Land Cover Classification System (LCCS) of 2004. The standard FAO classification scheme provides a standardized system of classification that can be used to analyze spatial and temporal land cover variability in the study area. This approach also has the advantage of facilitating the integration of Sinai land cover mapping products to be included with the regional and global land cover datasets. The total study area is 7450 km2 (1,773,842) feddans. The landscape classification was performed on SPOT4 data acquired in 2011 using combined multi-spectral bands of 20 meter spatial resolution. Geographic Information System (GIS) was used to edit the classification result in order to reach the maximum possible accuracy. GIS was also used to include all necessary information. The identified vegetative land cover classes of the study area are irrigated herbaceous crops, irrigated tree crops and rain fed tree crops. The non-vegetated land covers in the study area include: bare rock, bare soil, bare soil stony, bare soil very stony, bare soil salt crusts, loose and shifting sands and sand dunes. The water bodies were classified as artificial perennial water bodies (fish ponds and irrigated canals) and natural perennial water bodies as lakes (standing) and rivers (flowing). Artificial surfaces in the study area include linear and non-linear. The produced maps and the statistics of the different land covers are included in the following sub-sections.

Co‐hydrolysis of lignocellulosic biomass for microbial lipid accumulation

The herbaceous perennial energy crops miscanthus, giant reed, and switchgrass, along with the annual crop residue corn stover, were evaluated for their bioconversion potential. A co-hydrolysis process, which applied dilute acid pretreatment, directly followed by enzymatic saccharification without detoxification and liquid-solid separation between these two steps was implemented to convert lignocellulose into monomeric sugars (glucose and xylose). A factorial experiment in a randomized block design was employed to optimize the co-hydrolysis process. Under the optimal reaction conditions, corn stover exhibited the greatest total sugar yield (glucose + xylose) at 0.545 g g(-1) dry biomass at 83.3% of the theoretical yield, followed by switch grass (0.44 g g(-1) dry biomass, 65.8% of theoretical yield), giant reed (0.355 g g(-1) dry biomass, 64.7% of theoretical yield), and miscanthus (0.349 g g(-1) dry biomass, 58.1% of theoretical yield). The influence of combined severity factor on the susceptibility of pretreated substrates to enzymatic hydrolysis was clearly discernible, showing that co-hydrolysis is a technically feasible approach to release sugars from lignocellulosic biomass. The oleaginous fungus Mortierella isabellina was selected and applied to the co-hydrolysate mediums to accumulate fungal lipids due to its capability of utilizing both C5 and C6 sugars. Fungal cultivations grown on the co-hydrolysates exhibited comparable cell mass and lipid production to the synthetic medium with pure glucose and xylose. These results elucidated that combining fungal fermentation and co-hydrolysis to accumulate lipids could have the potential to enhance the utilization efficiency of lignocellulosic biomass for advanced biofuels production.

MODEL-ASSISTED ANALYSIS OF ELEVATED TEMPERATURE AND VAPOUR PRESSURE DEFICIT EFFECTS ON TOMATO STEM AND FRUIT WATER BALANCE

Maintaining good plant water status is crucial for optimal production and quality of tomato in greenhouses. Various new climate control technologies have been introduced to make greenhouse cultivation more energy-efficient, resulting in a modified greenhouse climate. Recently, there has been growing interest in the use of plant-based methods to steer the climate. Monitoring stem diameter variations (SDV) has been extensively studied in tree species, but is also very promising for herbaceous crops. Stem and fruit diameter variations provide crucial information about plant water status, though unambiguous interpretation of these dynamics is often difficult. Mechanistic modelling can help to elucidate the mechanisms driving plant behaviour and is therefore an important tool for interpreting the dynamic response of the plants to changes in microclimate. In the present study, tomato plants (Solanum lycopersicum L.) were subjected to elevated air temperature (Ta) and vapour pressure deficit (VPD), while SDV, sap flow and fruit growth were continuously monitored. Results indicated that stem shrinkage became more pronounced and fruits shrank during periods of high Ta and VPD. Simulation results showed that reduced fruit growth resulted from both increased fruit transpiration and decreased phloem inflow. Moreover, xylem backflow appeared when Ta and VPD reached maximum values. It was demonstrated that the reduced fruit growth resulted mainly from changes in stem water potential, rather than fruit water potential.

A suspended sediment budget for the agricultural Can Revull catchment (Mallorca, Spain)

Extensive rainfed herbaceous crops are one of the most representative agricultural elements of Mediterranean region, which should be one of the major factors affecting erosion processes. Although land use is commonly seen as resulting in increased sediment yields, the implementation of soil and water conservation practices can have the reverse effect. A sediment budget has been established in Can Revull, a small agricultural catchment (1.03 km2) on the island of Mallorca, by using 137Cs measurements, sediment source fi ngerprinting and more traditional monitoring techniques to quantify the individual components of the budget. A large proportion of the material mobilized from cultivated fi elds without conservation practices (gross erosion of 775 t yr 1, 1,270 t km 2 yr 1) was subsequently deposited either within the fi eld of origin (112 t yr 1, 180 t km 2 yr 1) or at intermediate locations between the source fi eld and the channel network (fi eld-to-channel conveyance loss was 454 t yr 1, 744 t km 2 yr 1). The estimates of sediment accumulation rates on the fl oodplain in the lower reaches of the catchment indicate that the mean sedimentation rate was 0.14 g cm-2 yr-1. This value was extrapolated to the total area of the fl oodplain to estimate a total annual conveyance loss or storage of 445 t yr 1. Monitoring at the catchment outlet over the study period (2004–2008) indicated a mean annual suspended sediment yield of 7 t km-2 yr-1. The sum of the estimates of sediment yield and fl oodplain storage (452 t yr-1) was taken to represent the total annual input of suspended sediment to the channel system. This value was subsequently apportioned using the information provided by the fi ngerprinting investigation, to estimate the mass of sediment reaching the channel network from cultivated fi elds and from eroding channel banks. Thus the annual contribution from channel banks was estimated to be 242 t yr-1. In the case of the contributions from cultivated fi elds, the estimates obtained were, as expected, signifi cantly less than the values of net soil loss from these zones provided by the 137Cs measurements due to conveyance losses associated to fi eld-to-channel conveyance loss. The overall sediment delivery ratios (< 1 %) indicate that approximately 99 % of the sediment mobilized by erosion within the Can Revull catchment is subsequently deposited before reaching the monitoring station. As such, the low sediment outputs from the study catchment should be seen as refl ecting the importance of conveyance losses and storage rather than a lack of sediment mobilization from the catchment surface, although part of the catchment headwaters was modifi ed historically by means of terraces and transverse walls to prevent erosion.

Energetic environmental and economic assessment of three tree species and one herbaceous crop irrigated with primary treated sewage effluent

The energetic, environmental, and economic performance of four bioenergy plant species (Αcacia cyanophylla, Eucalyptus camaldulensis, Populus nigra, and Arundo donax), irrigated with pre-treated effluent in a three-year-field trial, was investigated. Results showed that irrigation was more energy demanding compared to other practices. A. cyanophylla achieved 34, 83, and 189% higher above ground biomass energy yield than E. camaldulensis, A. donax, and P. nigra, respectively. A. cyanophylla and E. camaldulensis had higher energy requirements but they achieved higher net energy yield and energy ratio. P. nigra (3.49 € GJ−1) and A. donax (2.34 € GJ−1) were found to have higher energy production cost compared to E. camaldulensis (1.65 € GJ−1) and A. cyanophylla (1.24 € GJ−1). P. nigra and A. donax had the highest nutrient use efficiency for nitrogen (NUE-N) and phosphorus (NUE-P), respectively. It was concluded that species with low NUE, which is opposite to current directions, and high water use efficiency (WUE) (i.e. plant species with relatively low water demands and great biomass allocation in leaves), are more suitable when irrigation with strong effluent occur and N removal is primary objective. Such plant species have comparatively lower energy requirements, which is consistent with the current trend for low energy inputs in agriculture. To mitigate the losses in plant biomass and reduce the adverse environmental impacts from nutrients, additional practices should be adopted. Our results help us to draw important conclusions in order to set criteria in the selection of suitable bioenergy crops and practices.

FlowersOnTime: A Computer Decision-Support Tool for Floriculture Crop Producers

A computer decision-support tool was developed as an Extension outcome of the Floriculture Research Alliance to help commercial plant growers and educators estimate the effect of changing average air temperature on production time of over 60 species and cultivars of herbaceous ornamental crop plants. Cropping time predictions are based on research data from 16 sources. This information can help growers determine appropriate greenhouse temperature settings so that their plants are in flower on time to meet pre-determined market dates. The target audiences are growers, Extension professionals, and crop consultants.

Irrigation of energy crops with urban wastewater: Effects on biomass yields, soils and heating values

Exploitation of energy crops irrigated with non-conventional water resources on a large scale could decrease negative impacts from fossil fuel use, at the same time saving potable supplies and reducing disposal of polluting effluents in surface water, particularly in environments with water scarcity as Mediterranean basin.To this end, three energy crops (Typha latifolia, Arundo donax and Phragmites australis) were planted in experimental plots and irrigated over a 2-year period with the effluents of an urban wastewater depuration plant. Biomass and energy yields of the crops were evaluated; the effects on the main physical and chemical properties of soils (e.g. pH, EC, SOC, N, P) and leachate (pH, EC, COD) resulting from irrigation with wastewater were compared to those of irrigation with conventional water.In general, treatment with wastewater increased the biomass yield: this may be ascribed to the fertilising value of the wastewater. Irrigation with wastewater did not result in either notable changes of the soil's physical and chemical properties, or risks of soil structure decay, when compared to irrigation with conventional water. Only a slight and insignificant reduction of the soil's hydraulic saturated conductivity was measured.Percolation of contaminants (such as organic compounds and salts) into groundwater reserves was limited, as shown by the analysis of the leachate accumulated in lysimeters after irrigation with wastewater.Heating values measured by calorimetric tests were higher for T. latifolia in comparison to the other experimental species; nevertheless, the higher biomass productivity of A. donax makes the energy yield per unit of cultivated surface much higher than those of T. latifolia and P. australis.Even though the results achieved require further verification by mid- or long-term research, the present investigation shows that herbaceous crops irrigated with wastewater can produce appreciable biomass and energy yields. This is also an environmentally and economically sound way of wastewater disposal.

Energy from Agricultural and Animal Farming Residues: Potential at a Local Scale

Animal wastes from high-density farming have severe impacts on the nitrogen cycle. According to current regulations, the disposal of manure on cropland is constrained by nitrogen content in the agricultural soils. On the contrary, anaerobic digestion (AD) of these wastes can produce energy and a digestate, which is easier to handle than manure and can be applied for agronomic uses. When herbaceous crops are co-digested with manure to increase the efficiency of biogas production, the nitrogen content in the digestate further increases, unless these larger plants are equipped with nitrogen stripping technologies. We propose a model to compare larger (cooperative) and smaller (single parcel) AD conversion plants. The whole process is modeled: from the collection of manures, to the cultivation of energy crops, to the disposal of the digestate. The model maximizes the energy produced on the basis of available biomass, road network, local heat demand and local availability of land for digestate disposal. Results are the optimal size and location of the plants, their technology and collection basins. The environmental performances of such plants are also evaluated. The study has been applied to the province of Forlì-Cesena, an Italian district where animal farming is particularly relevant.

Comparative assessment of different methods for using land-cover variables for distribution modelling ofSalamandra salamandra longirotris

SUMMARYPredictive models are frequently used to define the most suitable areas for species protection or reintroduction. Land-cover variables can be used in different ways for distribution modelling. The surface area of a set of land-cover classes is often used, each land-cover presence/absence or the distance to them from any point of the study area can be preferred; multiple types of land-cover variables may be combined to produce a single model. This paper assesses whether different approaches to using land-cover variables may lead to different ecological conclusions when interpreted for conservation by focusing on the distribution of the salamaderSalamandra salamandra longirostris, an endangered amphibian subspecies in the south of the Iberian Peninsula. Twenty-eight land-cover classes and another 42 environmental variables were used to construct four different models. Three models used a unique type of land-cover variable: either the presence of each class, the surface area of each class or the distance to each class, with all three variable types jointly entered in a fourth model. All models attained acceptable scores according to some criteria (discrimination, descriptive and predictive capacities, classification accuracy and parsimony); however most of the assessment parameters computed indicated a better performance of the models using either the surface area of land classes or the distance to them from every sampled square, compared to the model using class presences. The best scores were obtained with the fourth model, which combined different types of land-cover variables. This model suggested that oak forest fragmentation in favour of herbaceous crops and pastures may have negative effects on the distribution ofS. s. longirostris. This was only partially suggested by the first three models, which considered a single type of land-cover variable, demonstrating the importance of considering a multi-variable analysis for conservation planning.

Conversion of Carbohydrates in Herbaceous Crops during Anaerobic Digestion

The methane yields and conversion of pentoses (xylose) and hexoses (cellulose) in hemp, maize, and white lupin were studied over 30 days of anaerobic digestion. Preservation of hemp increased the methane yield by 23% compared with the fresh hemp. The increased methane yield of hemp was verified by the enhanced conversion of C6 sugars, increasing from 48% to about 70%, whereas the conversion of C5 sugars increased from only 9% to nearly 50%. The consumption of all carbohydrates in fresh maize was almost complete in the 30 days of anaerobic digestion. Hence, there was no major difference in carbohydrate consumption between fresh and preserved maize during biogas production. Fresh white lupin produced the highest methane yield (343 ± 33 dm(3) kg(-1) TS) in this work, mainly due to its highest amount of proteins. Conversion of C6 sugars was 80%, but that of C5 sugars was notably less at 46%.

Impacts of herbaceous bioenergy crops on atmospheric volatile organic composition and potential consequences for global climate change

AbstractThe introduction of new crops to agroecosystems can change the chemical composition of the atmosphere by altering the amount and type of plant‐derived biogenic volatile organic compounds (BVOCs). BVOCs are produced by plants to aid in defense, pollination, and communication. Once released into the atmosphere, they have the ability to influence its chemical and physical properties. In this study, we compared BVOC emissions from three potential bioenergy crops and estimated their theoretical impacts on bioenergy agroecosystems. The crops chosen were miscanthus (Miscanthus × giganteus), switchgrass (Panicum virgatum), and an assemblage of prairie species (mix of ~28 species). The concentration of BVOCs was different within and above plant canopies. All crops produced higher levels of emissions at the upper canopy level. Miscanthus produced lower amounts of volatiles compared with other grasses. The chemical composition of volatiles differed significantly among plant communities. BVOCs from miscanthus were depleted in terpenoids relative to the other vegetation types. The carbon flux via BVOC emissions, calculated using the flux‐gradient method, was significantly higher in the prairie assemblage compared with miscanthus and switchgrass. The BVOC carbon flux was approximately three orders of magnitude lower than the net fluxes of carbon measured over the same fields using eddy covariance systems. Extrapolation of our findings to the landscape scale leads us to suggest that the widespread adoption of bioenergy crops could potentially alter the composition of BVOCs in the atmosphere, thereby influencing its warming potential, the formation of atmospheric particulates, and interactions between plants and arthropods. Our data and projections indicate that, among at least these three potential options for bioenergy production, miscanthus is likely to have lower impacts on atmospheric chemistry and biotic interactions mediated by these volatiles when miscanthus is planted on the landscape scale.

Challenges in enzymatic hydrolysis and fermentation of pretreated Arundo donax revealed by a comparison between SHF and SSF

The perennial herbaceous crop Arundo donax is a potential feedstock for second-generation bioethanol production. In the present work, two different process options were investigated for the conversion of two differently steam-pretreated batches of A. donax. The pretreated raw material was converted to ethanol with a xylose-consuming Saccharomyces cerevisiae strain, VTT C-10880, by applying either separate hydrolysis and fermentation (SHF) or simultaneous saccharification and fermentation (SSF). The highest overall ethanol yield and final ethanol concentration were achieved using SHF (0.27gg−1 and 20.6gL−1 compared to 0.24gg−1 and 19.0gL−1 when SSF was used). The performance of both SHF and SSF was improved by complementing the cellulolytic enzymes with hemicellulases. The higher amount of acetic acid in one of the batches was shown to strongly affect xylose consumption in the fermentation. Only half of the xylose was consumed when batch 1 (high acetic acid) was fermented, compared to that 94% of the xylose was consumed in fermentation of batch 2 (lower acetic acid). Furthermore, the high amount of xylooligomers present in the pretreated materials considerably inhibited the enzymatic hydrolysis. Both the formation of xylooligomers and acetic acid thus need to be considered in the pretreatment process in order to achieve efficient conversion of A. donax to ethanol.

Susceptibility of common herbaceous crops to Phytophthora cinnamomi and its influence on Quercus root rot in rangelands

The susceptibility to Phytophthora cinnamomi of four crops (wheat, oat, vetch, and yellow lupin) commonly planted in rangeland ecosystems in southern Spain was evaluated. By means of in vitro infection experiments, the presence of the pathogen into the roots of yellow lupin (symptomatic) and vetch (asymptomatic) was observed, but never into wheat and oat roots (asymptomatic). It was also demonstrated that yellow lupin stimulated the production of zoospores of P. cinnamomi. Vetch, wheat and oat did not stimulate zoospore production. Under controlled conditions, only yellow lupin induced an increase in the number of viable chlamydospores in the soil. We concluded that the culture of wheat, oat, and vetch in rangelands did not influence the epidemiology of the Quercus root disease, even when asymptomatically-infected vetch is grown, and these crops can constitute an alternative to the culture of yellow lupin in rangeland ecosystems affected by Quercus root rot.