C4 Grasses Research Articles

CO2 exchanges and evapotranspiration of a grazed pasture under tropical climate conditions

• Evapotranspiration and CO 2 exchange were assessed in grazed pasture. • The seasonality of CO 2 exchange was strongly agreement with rainfall seasonality. • Grazed tropical pasture acted as CO 2 sink taking into account all uncertainties. • Averaged NEE 2 year was -230 ± 22 gC m −2 y −1 . • WUE was similar to the values found in other pastures around the world. Studies concerning the role of livestock farming on the regional budget of CO 2 in Northeast of Brazil are scarce. Thus, our main objective was to evaluate the variability of CO 2 exchange and evapotranspiration (ET) of a cultivated tropical forage C4 grass ( Brachiaria brizantha ) grazed by sheep for meat production. The experiment was conducted during the period from 2015-oct-01 to 2017-sep-30 using an eddy covariance flux tower. The pasture acted as a moderate CO 2 sink, with mean annual net ecosystem exchange of -215 ± 22 g C m −2 y −1 , while the average uncertainty associated with the calculation procedure was 15 g C m −2 ± 7.20% of NEP. The mean annual ET was 967 ± 245 mm. Carbon use efficiency at the ecosystem level was 0.20 ± 0.03, which is more efficient compared to similar experiments in grazed environments around the world. Water use efficiency at the ecosystem level was 1.14 ± 0.01 g C (kg H 2 O) −1 .

Physiological performance of sweet sorghum in Assam

Sweet sorghum (Sorghum bicolor L. Moench) is a self-pollinated, diploid (2n=20), C4 grass species belonging to the family Poaceae. It is a drought tolerant crop, used as food for humans and feed for animals. Currently, the crop has been given more importance due to its capacity to produce bio-ethanol or bio fuels. As in Assam, its cultivation is very limited, therefore, a field experiment was conducted at ICR farm of Assam Agricultural University, Jorhat during rabi season of 2019-20 with twelve diverse genotypes of sweet sorghum with the objectives to evaluate sweet sorghum genotypes on the basis of morpho- physiological traits under rabi season. The experiment was laid out in randomized complete block design (RCBD) with three replications and the crop was raised following the recommended package of practices. The morpho-physiological parameters of the crop and yield were recorded following standard methodologies. The results indicated significant differences in all the morpho-physiological parameters and grain yield among different sweet sorghum genotypes. All these characters were found significantly higher in the genotype ICSV 15006 followed by ICSV 25274, while significantly lower values of all the above were recorded in ICSV 13012. Among the genotypes, ICSV15006 possessed significantly higher plant height, number of tillers, total dry matter and total sugars in both stalks and grains at harvest. The number of green leaves, leaf area index, relative leaf water content, total leaf chlorophyll and absolute growth rate were also found significantly higher in the genotype ICSV 15006 followed by ICSV 25274. Significantly higher grain yield with 1.06 t ha-1 was observed in the genotype ICSV 15006 followed by ICSV 25274 with 1.03 t ha-1. Based on morpho-physiological characters and yield, the genotypes ICSV 15006 and ICSV 25274 were identified as the superior genotypes which can be used in different breeding programme for yield improvement in sweet sorghum, more particularly during rabi season in Assam.

Physiological performance of sweet sorghum in Assam

Sweet sorghum (Sorghum bicolor L. Moench) is a self-pollinated, diploid (2n=20), C4 grass species belonging to the family Poaceae. It is a drought tolerant crop, used as food for humans and feed for animals. Currently, the crop has been given more importance due to its capacity to produce bio-ethanol or bio fuels. As in Assam, its cultivation is very limited, therefore, a field experiment was conducted at ICR farm of Assam Agricultural University, Jorhat during rabi season of 2019-20 with twelve diverse genotypes of sweet sorghum with the objectives to evaluate sweet sorghum genotypes on the basis of morpho- physiological traits under rabi season. The experiment was laid out in randomized complete block design (RCBD) with three replications and the crop was raised following the recommended package of practices. The morpho-physiological parameters of the crop and yield were recorded following standard methodologies. The results indicated significant differences in all the morpho-physiological parameters and grain yield among different sweet sorghum genotypes. All these characters were found significantly higher in the genotype ICSV 15006 followed by ICSV 25274, while significantly lower values of all the above were recorded in ICSV 13012. Among the genotypes, ICSV15006 possessed significantly higher plant height, number of tillers, total dry matter and total sugars in both stalks and grains at harvest. The number of green leaves, leaf area index, relative leaf water content, total leaf chlorophyll and absolute growth rate were also found significantly higher in the genotype ICSV 15006 followed by ICSV 25274. Significantly higher grain yield with 1.06 t ha-1 was observed in the genotype ICSV 15006 followed by ICSV 25274 with 1.03 t ha-1. Based on morpho-physiological characters and yield, the genotypes ICSV 15006 and ICSV 25274 were identified as the superior genotypes which can be used in different breeding programme for yield improvement in sweet sorghum, more particularly during rabi season in Assam.

Pyruvate, phosphate dikinase regulatory protein impacts light response of C4 photosynthesis in Setaria viridis.

In C4 plants, the pyruvate (Pyr), phosphate dikinase regulatory protein (PDRP) regulates the activity of the C4 pathway enzyme Pyr, phosphate dikinase (PPDK) in a light-/dark-dependent manner. The importance of this regulatory action to C4 pathway function and overall C4 photosynthesis is unknown. To resolve this question, we assessed in vivo PPDK phospho-regulation and whole leaf photophysiology in a CRISPR-Cas9 PDRP knockout (KO) mutant of the NADP-ME C4 grass green millet (Setaria viridis). PDRP enzyme activity was undetectable in leaf extracts from PDRP KO lines. Likewise, PPDK phosphorylated at the PDRP-regulatory Thr residue was immunologically undetectable in leaf extracts. PPDK enzyme activity in rapid leaf extracts was constitutively high in the PDRP KO lines, irrespective of light or dark pretreatment of leaves. Gas exchange analysis of net CO2 assimilation revealed PDRP KO leaves had markedly slower light induction kinetics when leaves transition from dark to high-light or low-light to high-light. In the initial 30 min of the light induction phase, KO leaves had an ∼15% lower net CO2 assimilation rate versus the wild-type (WT). Despite the impaired slower induction kinetics, we found growth and vigor of the KO lines to be visibly indistinguishable from the WT when grown in normal air and under standard growth chamber conditions. However, the PDRP KO plants grown under a fluctuating light regime exhibited a gradual multi-day decline in Fv/Fm, indicative of progressive photosystem II damage due to the absence of PDRP. Collectively, our results demonstrate that one of PDRP's functions in C4 photosynthesis is to ensure optimal photosynthetic light induction kinetics during dynamic changes in incident light.

Near infrared spectroscopy calibration strategies to predict multiple nutritional parameters of pasture species from different functional groups

Near infrared reflectance (NIR) spectroscopy has been used by the agricultural industry as a rapid and inexpensive technique to quantify nutritional chemistry in plants. The aim of this study was to evaluate the performance of NIR calibrations in predicting the nutritional composition of ten pasture species that underpin livestock industries in many countries. The species comprised a range of functional diversity (C3 legumes; C3/C4 grasses; annuals/perennials) and origins (tropical/temperate; introduced/native) that grew under varied environmental conditions (control and experimentally induced warming and drought) over a period of more than two years ( n = 2622). A maximal calibration set including 391 samples was used to develop and evaluate calibrations for all ten pasture species (global calibrations), as well as for subsets comprised of the plant functional groups. This study found that the global calibrations were appropriate to predict the six key nutritional quality parameters for the studied pasture species, with the highest estimation quality found for ash (ASH), crude protein (CP), amylase-treated neutral detergent fibre (aNDF) and acid detergent fibre (ADF), and the lowest for ether extract (EE) and acid detergent lignin (ADL) parameters. The plant functional group calibrations for C3 grasses performed better than the global calibrations for ASH, CP, ADF and EE parameters, whereas for C3 legumes and C4 grasses the functional group calibrations performed less well than the global calibrations for all nutritional parameters of these groups. Additionally, the calibrations were able to capture the range of variation in forage nutritional quality caused by future climate scenarios of warming and severe drought.

Global Integrated Genomic and Transcriptomic Analyses of MYB Transcription Factor Superfamily in C3 Model Plant Oryza sativa (L.) Unravel Potential Candidates Involved in Abiotic Stress Signaling.

Plant transcription factors (TFs) are significant players in transcriptional regulations, signal transduction, and constitute an integral part of signaling networks. MYB TFs are major TF superfamilies that play pivotal roles in regulation of transcriptional reprogramming, physiological processes, and abiotic stress (AbS) responses. To explore the understanding of MYB TFs, genome and transcriptome-wide identification was performed in the C3 model plant, Oryza sativa (OsMYB). This study retrieved 114 OsMYB TFs that were computationally analyzed for their expression profiling, gene organization, cis-acting elements, and physicochemical properties. Based on the microarray datasets, six OsMYB genes which were sorted out and identified by a differential expression pattern were noted in various tissues. Systematic expression profiling of OsMYB TFs showed their meta-differential expression of different AbS treatments, spatio-temporal gene expression of various tissues and their growth in the field, and gene expression profiling in responses to phytohormones. In addition, the circular ideogram of OsMYB genes in related C4 grass plants conferred the gene synteny. Protein–protein interactions of these genes revealed the molecular crosstalk of OsMYB TFs. Transcriptional analysis (qPCR) of six OsMYB players in response to drought and salinity stress suggested the involvement in individual and combined AbS responses. To decipher how these OsMYB play functional roles in AbS dynamics, further research is a prerequisite.

Precipitation variations, rather than N deposition, determine plant ecophysiological traits in a desert steppe in Northern China

Understanding how plant ecophysiological traits of coexisting species within a community respond to environmental changes could help to predict the shift in plant community structure and function, but it remains limited in the scenarios of co-occurring precipitation variations and N deposition. A two-year field experiment was conducted to explore the effects of large precipitation changes (reduced and increased precipitation amount by 25% and 50% relative to ambient control) and high N deposition (10 g N m−2 yr−1) on a series of leaf ecophysiological traits of three dominant species (Stipa tianschanica, a C3 grass; Cleistogenes squarrosa, a C4 grass; and Artemisia capillaris, a C3 forb) in a desert steppe in Northern China. Increasing precipitation significantly linearly promoted the leaf light-saturated photosynthesis rate (Asat) and N use efficiency of the two C3 species, irrespective of N addition. The rises in Asat of both C3 species were mainly caused by increased soil moisture, which strongly induced increases in leaf stomatal conductance (gs) and declines in quantum yield of photosystem II (ΦPSII). However, the Asat of the two C3 species was weakly correlated with their specific leaf area and leaf N concentration, whereas the Asat of the C4 grass was negatively related to its leaf N. Moreover, the Asat, height, and aboveground biomass of the forbs were much more water-sensitive than those of both grass species, with a consequence of the most dominant species turning from grass to forbs as precipitation increased. Our findings highlight that water limitation, rather than N deficit, is the largest factor controlling plant growth in drylands, and plant species-specific ecophysiological responses to precipitation fluctuations will cause a substantial shift in the production and composition of plant community.

Grazing and defoliation timing effects in Great Plains ponderosa pine woodland following a large summer wildfire

There remains a high level of ambiguity around post-fire grazing management. The Lodgepole Complex fire burned 109,346 ha in east-central Montana in July 2017, including areas previously burned in 2003 by the Bureau of Land Management for fuels mitigation. We hypothesized that herbaceous productivity and species composition in ponderosa pine woodlands are resistant to moderate grazing and timing of defoliation the first growing season after fire. Eight exclosures (25 × 15 m) were built, 4 on reburned area and 4 on wildfire area. To determine grazing effects, a 15 × 10 m sampling area in each exclosure was paired with a grazed section outside the exclosure. Additionally, four 5x10-m plots were established within each exclosure and were mowed to 10 cm in June, July, August, or not mowed to determine seasonal defoliation effects. Differences between grazed and nongrazed sites in 2019 were limited. There was a trend for less old dead biomass in grazed than nongrazed treatments. Species richness was greater on grazed sites than nongrazed or reburn sites. Native species richness was greater on grazed sites than nongrazed sites and reburn sites had an intermediate level of native species richness. Standing crop was reduced by defoliation, with current year and perennial grass biomass being unaffected. The reduction in standing crop was driven by less old dead biomass on defoliated plots. June defoliation reduced C3 grasses and increased C4 grasses, and June and July defoliation each reduced annual grasses. Simpson’s and native Simpson’s diversity were greater on defoliated plots. Results indicate ponderosa pine woodland is resilient to moderate post-fire grazing.

Genetic Determinants of Biomass in C4 Crops: Molecular and Agronomic Approaches to Increase Biomass for Biofuels.

Bio-based fuels have become popular being efficient, cost-effective, and eco-friendly alternatives to fossil fuels. Among plant sources exploited as feedstocks, C4 grasses, such as sugarcane, maize, sorghum, and miscanthus, are highly resourceful in converting solar energy into chemical energy. For a sustainable and reliable supply of feedstocks for biofuels, we expect dedicated bioenergy crops to produce high biomass using minimum input resources. In recent years, molecular and genetic advancements identified various factors regulating growth, biomass accumulation, and assimilate partitioning. Here, we reviewed important genes involved in cell cycle regulation, hormone dynamics, and cell wall biosynthesis. A number of important transcription factors and miRNAs aid in activation of important genes responsible for cell wall growth and re-construction. Also, environmental components interacting with genetic controls modulate plant biomass by modifying gene expression in multiple interacting pathways. Finally, we discussed recent progress using hybridization and genome editing techniques to improve biomass yield in C4 grasses. This review summarizes genes and environmental factors contributing biomass yield in C4 biofuel crops which can help to discover and design bioenergy crops adapting to changing climate conditions.

New site at Olduvai Gorge (AGS, Bed I, 1.84 Mya) widens the range of locations where hominins engaged in butchery

Outstanding questions about human evolution include systematic connections between critical landscape resources—such as water and food—and how these shaped the competitive and biodiverse environment(s) that our ancestors inhabited. Here, we report fossil n-alkyl lipid biomarkers and their associated δ13C values across a newly discovered Olduvai Gorge site (AGS) dated to 1.84 million years ago, enabling a multiproxy analysis of the distributions of critical local landscape resources across an explicit locus of hominin activity. Our results reveal that AGS was a seasonally waterlogged, largely unvegetated lakeside site situated near an ephemeral freshwater river surrounded by arid-adapted C4 grasses. The sparse vegetation at AGS contrasts with reconstructed (micro)habitats at the other anthropogenic sites at Olduvai Gorge, suggesting that central-provisioning places depended more heavily on water access than vegetation viz. woody plants as is often observed for modern hunter-gatherers. As hominins at AGS performed similar butchering activities as at other Bed I sites, our results suggest they did not need the shelter of trees and thus occupied a competitive position within the predatory guild.

Plant–soil feedbacks help explain plant community productivity

Plant productivity often increases with species richness, but the mechanisms explaining this diversity-productivity relationship are not fully understood. We tested if plant-soil feedbacks (PSF) can help to explain how biomass production changes with species richness. Using a greenhouse experiment, we measured all 240 possible PSFs for 16 plant species. At the same time, 49 plant communities with diversities ranging from one to 16 species were grown in replicated pots. A suite of plant community growth models, parameterized with (PSF) or without PSF (Null) effects, was used to predict plant growth observed in the communities. Selection effects and complementarity effects in modeled and observed data were separated. Plants created soils that increased or decreased subsequent plant growth by 25%±10%, but because PSFs were negative for C3 and C4 grasses, neutral for forbs, and positive for legumes, the net effect of all PSFs was a 2%±17% decrease in plant growth. Experimental plant communities with 16 species produced 37% more biomass than monocultures due to complementarity. Null models incorrectly predicted that 16-species communities would overyield due to selection effects. Adding PSF effects to Null models decreased selection effects, increased complementarity effects, and improved correlations between observed and predicted community biomass. PSF models predicted 26% of overyielding caused by complementarity observed in experimental communities. Relative to Null models, PSF models improved the predictions of the magnitude and mechanism of the diversity-productivity relationship. Results provide clear support for PSFs as one of several mechanisms that determine diversity-productivity relationships and help close the gap in understanding how biodiversity enhances ecosystem services such as biomass production.

Microbotanical signatures of kreb: differentiating inflorescence phytoliths from northern African wild grasses

Throughout northern Africa, evidence for an intensification of wild grass gathering is reflected in Holocene archaeological contexts. However, both the recovery of macrobotanical assemblages and the specificity of their taxonomic classification are heavily influenced by food processing and post-depositional conditions. In contrast, inflorescence phytoliths provide high levels of taxonomic specificity and preserve well in most archaeological contexts. This study analyses the in situ morphology of inflorescence phytoliths from modern specimens of nine wild C4 grass species commonly observed in ethnographic studies and recovered in seed assemblages from archaeological contexts across northern Africa. Morphological differences in Interdigitate phytoliths within the fertile florets of six Paniceae species enabled differentiation between them. The morphological parameters established in this study provide an additional resource for archaeological and palaeoecological analyses using phytoliths, which demonstrates the effectiveness of applying this method to African wild grass species.

Moving warm‐season forage bermudagrass (Cynodon spp.) into temperate regions of North America

AbstractGeorgia, located in the Southeastern USA, has been historically dominated by two perennial forage grass production systems. Tall fescue (Lolium arundinaceum [Schreb.] S.J. Darbyshire) is more prevalent in the northern parts of the state, while bermudagrass [Cynodon dactylon (L.) Pers.] is ubiquitous to the southern portion. Climatologists have documented notable changes in temperature and precipitation patterns in the state that have contributed to an invasion of warm‐season species in the northern portion of the state. In the transition zones between warm‐season and‐cool‐season perennial grass‐dominated regions of North America, C4 grasses can maintain productivity at high temperatures while C3 grasses are transitioning to a reproductive stage with minimal vegetative growth during summer. For this reason, warm‐season grasses could replace a portion of the grasslands at latitudes greater than 35°. This manuscript documents the expansion of warm‐season bermudagrass into northern Georgia, explores the climatic factors driving this transition, and highlights previous and on‐going research. We specifically focus on evaluating freeze or cold tolerance of bermudagrass germplasm. The C. dactylon cultivars exhibit more cold tolerance than C. nlemfuënsis (stargrass) since they are more rhizomatous and rely less on above‐ground stolons for regrowth and winter survival. Conversely, these cultivars tend to have poor nutritive value and are highly susceptible to insect damage. On‐going research is identifying germplasm that provides adequate cold tolerance to meet the needs of farmers transitioning to warm‐season production systems in the lower transition zone.

Legacy effects of nutrient addition reduces and displaces trophic niches in Collembola communities in a Brazilian woodland savanna

Ecosystems worldwide are being subjected to increasing rates of nutrient deposition. Additional nitrogen (N) and phosphorus (P) inputs and liming are common practices in agroecosystems that have long-term consequences for plant and microbial diversity and community structure during ecosystem restoration. However, legacy effects of nutrient deposition on multitrophic biodiversity and trophic interactions of soil organisms are poorly understood. Collembola is a good model group to study such effects. These small soil invertebrates are intimately linked to plants and microbes, and play an important role in soils by supporting soil fertility and energy channeling to higher trophic levels in soil food webs. Here, we studied the trophic niche structure of epigeic Collembola during a long-term (20 years) nutrient addition experiment in the Central Brazilian savanna (Cerrado), one of the tropical agricultural frontiers. We used descriptive isotopic metrics of Collembola communities based on stable isotopes of carbon and nitrogen to evaluate the legacy effects of fertilization (with N, P, and N + P additions) and liming on their trophic-niche structure. The strongest trophic niche shifts were observed under N addition, manifested in the form of (i) a reduction in trophic niche widththat is, decreased diversity of consumed basal resources available to the Collembola communityand (ii) in a more even distribution of Collembola taxa in trophic space. Community trophic niche was strongly displaced under P, N + P, and liming additions (i.e., it did not overlap with the control), reflecting intensified trophic links of Collembola to exotic C4 grasses. Overall, our results indicate that increased atmospheric N deposition simplifies the trophic structure of Collembola communities, which may affect the efficiency and pathways of energy channeling in soil food webs and soil functioning. In addition, the observed niche shifts suggests the need for flexibility in feeding by soil animals in savanna to persist under supplemental N + P and liming. Our study is among the first to explore the trophic structure of invertebrates in tropical soils and provides further evidence that nutrient deposition and agricultural fertilization and liming legacy effects have long-term consequences for soil organisms on multiple trophic levels.

Root trait shifts towards an avoidance strategy promote productivity and recovery in C3 and C4 pasture grasses under drought

Abstract Plant species show a broad spectrum of plasticity in their covarying root traits in response to soil water limitation ranging from no change to shifts towards traits that enhance water and nutrient acquisition. Knowledge of root trait correlations and associated trait plasticity under drought is crucial to sustaining grassland production, including rangelands and pastures, under future, drier climates. Here, we investigated below‐ground responses to drought in four C3 and three C4 grasses and whether these explain above‐ground responses during extreme cool‐season drought and post‐drought recovery in a well‐replicated field experiment. We hypothesised that (a) C3 and C4 functional groups differ in their below‐ground trait responses to drought: C3 species shift their traits in line with a drought avoidance strategy and C4 species shift towards drought tolerance strategies; (b) post‐drought recovery is associated with below‐ground carbon reserves in both functional groups. Root traits in the C3 functional group differed from C4 by having higher values for specific root length, nitrogen and soluble sugar concentrations, while C4 root traits were associated with higher mean diameter, tissue density and starch concentrations. Drought‐induced plasticity in root traits in both functional groups was evidenced by increased values for specific root length, soluble sugars and nitrogen concentrations, and reduced values for tissue density, which we interpret as a drought avoidance strategy. Increasing root soluble sugars in C3 and C4 grasses and lower root tissue density in C4 species under drought were associated with greater above‐ground productivity. Above‐ground biomass recovery post‐drought was predicted by root and crown soluble sugar concentrations and root longevity across both plant functional groups. These findings highlight the importance of understanding links between root trait plasticity and plant productivity during and following drought for predicting plant species' responses to changes in a future climate. Read the free Plain Language Summary for this article on the Journal blog.

Soil susceptibility to salinity and sodicity in sorghum areas under abiotic stress

Sorghum is a C4 grass adapted to saline and water stress, common in semiarid regions. Therefore, deficit irrigation is an alternative for rural producers, since productivity is not considerably affected. However, the use of brackish water can lead to salinization and/or sodification of the soil. Based on this, the objective was to evaluate the effect of irrigation water salinity and deficient irrigation depth on the soil sodification and salinization process. Two different experiments were carried out, designed in randomized blocks, under four irrigation blades (IB1 = 53%, IB2 = 67%, IB3 = 85% and IB4 = 94% of Culture evapotranspiration (ETc)) and four salinities, expressed in electrical conductivity (ECw) - 1.5; 3.0; 4.5 and 6.0 dS m-1. The variables analyzed were conductivity of the saturation extract (ECse) and the Sodium Adsorption Ratio of the extract (SARse), estimated by soil-water suspension 1:2.5 in layers 0 - 20 and 20 - 40 cm of the soil, considering their average.

Herbivore isotopic dietary ecology of the middle Miocene Maboko Formation, Kenya

Middle Miocene deposits at Maboko Island in the Nyanza Rift of Western Kenya (~15–14 Ma) have yielded a rich fossil mammalian record that documents a mid-Miocene faunal shift. Palaeoecological proxies for Maboko have previously been interpreted to indicate heterogeneous habitats, ranging from grassland to closed canopy forest and implicated in this turnover. Stable carbon and oxygen isotope data of fossil herbivore enamel from catarrhine-bearing deposits at Maboko were analyzed to reconstruct the nature of C3 vegetation (i.e., water-stressed or subcanopy), as well as determining if any C4 biomass, representative of more open woodland or grassland habitats, were consumed. Taxa sampled include representatives of ruminants, suoids, rhinocerotids, and proboscideans. δ13Cenamel and δ18Oenamel values of Maboko fossil herbivores indicate foraging strategies consistent with a C3 dominated ecosystem, exhibiting a range of δ13Cenamel signatures similar to those of extant browsing herbivores foraging in mosaics of open forest/woodland habitats. Within the Maboko sequence, isotopic evidence indicates varying environments based on variable dietary spectra associated with discrete fossiliferous units within the succession. Relative to other stratigraphic beds, isotopic signals of herbivore enamel from Bed 5b, for example, reflect more closed woodland/forest foraging. The overall ~4‰ range of δ13Cenamel values from Maboko (−14.1‰ to −10.2‰) is statistically similar to δ13Cenamel values from the slightly younger middle Miocene site of Fort Ternan and is consistent with faunal and paleosol evidence from Maboko suggesting ecological variability. However, the isotopic evidence from Maboko indicates that environmental variability is more constrained than previously reconstructed, instead ranging from more open canopy forest to open woodland habitats, albeit with some spatial and temporal heterogeneity. Closed canopy forest plants and C4 biomass were not detectable as dietary components for any herbivores sampled thus far; nor was there evidence of significantly water-stressed C3 vegetation (possibly C3 grasses) being consumed.

Abandoned pastures and restored savannas have distinct patterns of plant–soil feedback and nutrient cycling compared with native Brazilian savannas

Abstract Around 40% of the original Brazilian savanna territory is occupied by pastures dominated by fast‐growing exotic C4 grasses, which impact ecosystem nutrient cycling. The restoration of these areas depends on the re‐establishment of soil processes. We assessed how restoration of abandoned pastures through direct seeding of native species and land‐management practices (burning and ploughing) affect soil nutrient cycling dynamics compared with native savannas. We compared the activity of soil enzymes related to carbon, nitrogen (N) and phosphorus (P) cycling as well as soil microbial biomass and soil chemical properties (pH and the concentration of N, P, potassium [K] and soil organic matter) among abandoned pastures, native savanna and restored areas. Abandoned pastures had faster nutrient turnover than native savanna, dominated by slow‐growing native species. This pattern was evident from the overall higher biomass‐specific enzyme activities in abandoned pastures than in native savanna. Compared with native savanna, restored areas had similar levels of soil enzyme activities, but lower microbial biomass and soil organic matter. The low enzyme activity in restored areas was likely related to a reduced soil organic carbon concentration due to practices such as burning and ploughing, rather than the restoration of plant–soil feedback. The lower immobilization of nutrients in microbial biomass and lower retention of nutrients in restored areas, compared with native savanna, is expected to favour the re‐establishment of fast‐growing exotic species. Synthesis and application. Despite reducing the resprouting and germination of exotic grasses and improving the establishment of native grasses in the short term, restoration practices have major impacts on the soil microbial community and soil fertility. The reduction of soil microbial biomass and organic matter content reduces the immobilization of soil nutrients and is expected to favour a fast nutrient turnover in the ecosystem. This may result in the re‐establishment of exotic grasses in the long term. Future efforts should focus on the recovery of soil organic matter content and the establishment of soil microbial communities similar to native ecosystems after the application of land‐management practices. Therefore, the restoration of abandoned pastures should consider a greater focus on restoring soil carbon and nutrient cycling

The Australasian grass flora in a global context

AbstractAustralia's flora and fauna have long been considered unique, but whether this applies to its grasses is less known. This study characterises the Australasian grass flora biogeographically. We investigate the distribution of C3 and C4 grass genera across four continents and construct broad profiles of their grass flora. We use endemism to examine global patterns of specialisation, and inter‐continental distributions as indicators of dispersal, using databases constructed over twenty years. We examined Australasian patterns with regard to endemicity and shared groups and categorised all of the region's genera into four age classes, from Australia's separation from Gondwana to the present. Globally, each continent presented a unique profile and C4 grasses were more widely shared than C3. Australasia's grasses equally comprise C3 and C4 genera; it shared two thirds of its C4 types with other continents, whereas C3 types split evenly between shared and endemic. Australasia shared relatively few genera with just one neighbour (7% C3, 13% C4), primarily with EurAsia. Australasian grass genera and species were either endemic or globally widespread, and 88% of C3 and 93% of C4 species were derived from lineages that originated elsewhere. We conclude Southeast Asia was the gateway for dispersal into Australasia, akin to rainforest taxa exchanges which increased from c12 Ma, with about 65% of Australasia's grass genera arriving in the past 3.5 Ma. The strong presence of C4 grasses in Australasia implies they have infiltrated a wide range of ecosystems, many probably occupied by ancient taxa with which they had not co‐evolved.

Seasonal soil moisture variability, not drought, drives differences in photosynthetic physiology of two C4 grass species

Seasonal soil moisture variability, not drought, drives differences in photosynthetic physiology of two C4 grass species