Plant-soil Interface Research Articles

Grazing period management affects the accumulation of plant functional groups, and soil nutrient pools and regulates stoichiometry in the desert steppe of Northwest China

To understand how nutrient cycling and sequestration are influenced by different grazing periods, the C:N:P stoichiometry features of the plant–soil interface in the desert steppe were measured and evaluated. The 5-year seasonal grazing experiment employed four grazing period treatments: traditional time of grazing (TG), early termination of grazing (EG), delayed start of grazing (DG), and delayed start and early termination of grazing (DEG). Additionally, fenced off desert steppe served as the control. The grazing periods each had a differing impact on the C:N:P stoichiometry in both plant functional group and soil depth comparisons. Compared to the EG, DG, and DEG treatments, the TG treatment had a more significant impact on the C, N, and P pools of grass, as well as the C:P and N:P ratios of forbs, but had a reduced effect on the C:P and N:P ratios of legumes. In contrast to plants, the DG treatment exhibited greater advantages in increasing C pools within the 0–40 cm soil layer. Furthermore, in the 10–20 cm soil layer, the C:P and N:P ratios under the EG treatment were significantly higher, ranging from 8.88% to 53.41% and 72.34%–121.79%, respectively, compared to the other treatments (TG, DG, and DGE). The primary drivers of the C, N, and P pools during different grazing periods were above-ground biomass (AGB) and litter biomass (LB). Both lowering the plant C:P and N:P ratios and considerably raising the plant P pool during different grazing periods greatly weakened the P limitation of the desert steppe environment. It is predicted that delayed start grazing might be a management strategy for long-term ecosystem sustainability, as it regulates above-ground nutrient allocation and has a positive effect on soil C and N pools.

Advances in Plant–Soil Feedback Driven by Root Exudates in Forest Ecosystems

Plant–soil feedback (PSF) was initially developed in the field of agricultural practices. In recent years, PSF has been extended to various ecosystems. Root exudates, essential for the exchange of materials, energy, and information at the plant–soil interface, significantly influence PSF. However, how PSF is driven by root secretions and the role of these secretions in different PSF pathways still needs to be further explored, particularly in forest ecosystems. Soil nutrients, microbial communities, and nematodes are important research topics in the process of PSF driven by root exudates. Investigating these aspects driven by root exudates provides valuable insights into the complex interactions both above ground and below the surface. This research can offer theoretical support and guidance for building stable, healthy, and sustainable forest ecosystems in the future.

A Versatile Glass Jar System for Semihydroponic Root Exudate Profiling.

Root exudates shape the plant-soil interface, are involved in nutrient cyclingand modulate interactions with soil organisms. Root exudates are dynamic and shaped by biological, environmental, and experimental conditions. Due to their wide diversity and low concentrations, accurate exudate profiles are challenging to determine, even more so in natural environments where other organisms are present, turning over plant-derived compounds and producing additional compounds themselves. The semihydroponic glass jar experimental system introduced here allows control over biological, environmental, and experimental factors. It allows the growth of various phylogenetically distinct plant species for up to several months with or without microbes, in a variety of different growth media. The glass-based design offers a low metabolite background for high sensitivity and low environmental impact as it can be reused. Exudates can be sampled nondestructively, and conditions can be altered over the course of an experiment if desired. The setup is compatible with mass spectrometry analytics and other downstream analytical procedures. In summary, we present a versatile growth system suited for sensitive root exudate analysis in a variety of conditions.

Potential short-term effects of earthquake on the plant-soil interface in alpine grassland of the Qinghai-Tibetan Plateau.

Earthquakes are environmental disturbances affecting ecosystem functioning, health, and biodiversity, but their potential impacts on plant-soil interface are still poorly understood. In this study, grassland habitats in areas near and away from the seismo-fault in Madou, a region typical of alpine conditions on the Qinghai-Tibetan Plateau, were randomly selected. The impacts of earthquake on soil properties and plant nutrient content in the short term were emphasized, and their potential relationships with community diversity and productivity were examined. According to the findings of the study, the Maduo earthquake led to a decrease in soil nutrient content in alpine grassland ecosystems, especially soil TC, TN, TP, TCa, AP, AK, NH4 +-N, and SOC, and inhibited the absorption of N, Ca, and Mg nutrients by plants. In addition, the diversity and productivity of communities were affected by both direct and indirect earthquake pathways. The negative impacts of seismic fracture on soil structure had the most significant direct impact on plant community diversity. Earthquakes also indirectly reduced community productivity by reducing the soil N content and inhibiting the absorption of plant nutrients. Our findings suggested that earthquakes could potentially decrease the stability of the alpine grassland ecosystem on the QTP by affecting nutrient availability at the plant-soil interface.

Effects and Consequences of Nano Fertilizer Application on Plant Growth and Developments: A Review

Nano fertilizers have emerged as a cutting-edge innovation in agricultural practices, poised to redefine nutrient delivery and management at the plant-soil interface. This review provides a comprehensive overview of the effects and consequences of nano fertilizer application on plant wellness. The inherent properties of nanoparticles allow for enhanced nutrient absorption, precise delivery, and increased bioavailability, potentially revolutionizing traditional fertilization methods. The results, as evidenced by multiple studies, indicate significant improvements in growth parameters, seed production, and overall plant health. Moreover, plants treated with nano fertilizers have shown heightened resistance to both biotic and abiotic stresses. However, while the benefits are promising, concerns arise regarding the ecological persistence of nanoparticles, potential bio-magnification, and implications for human health. A comparative analysis with conventional fertilizers revealed nano fertilizers' superior efficiency, but also brought forth economic considerations and environmental footprints. The current regulatory landscape is dynamic, with policies adapting to the rapid advancements of nanotechnology in agriculture. As research continues to bridge existing gaps, technological advancements are concurrently shaping the future prospects of nano fertilizer application. This review underscores the need for a balanced understanding of the potential and challenges, emphasizing collaborative efforts to harness nano fertilizers' full potential while ensuring ecological and human health safety.

Integrating fine root diameter and watershed mapping to characterize rhizosphere hydrology

Root morphology and soil hydraulic characteristics were integrated using watershed distance mapping to show water distribution and uptake across the plant-soil interface. Poplar (Populus deltoides, P. trichocarpa), maize (Zea mays), juniper (Juniperus virginiana), grape (Vitis rotundifolia) and maple (Acer saccharum) seedlings were grown in sand, after which root diameter and soil water dynamics were assessed via sequential neutron radiography. Three local soil regions (root-soil interface or edge, rhizosphere, bulk soil) were classified based on both radial distance from the root surface and diameter of the nearest root, from which changes in water content and distribution were characterized using digital image processing. Water content dynamics across the rhizosphere showed two different species-independent processes: a consistently elevated water content at the root-soil edge interface which increased with root diameter, and hysteresis as the rhizosphere transitioned to bulk soil (∼0.5 cm from the root), independent of root diameter. Water uptake per unit root surface area declined exponentially with root diameter, independent of species. Results highlight the species-independent hydrologic characteristics of the rhizosphere and the potential for evaluating them in a local spatially connected soil context. Avenues for improved integration of soil and root characteristics are discussed.

Meta-omics integration approach reveals the effect of soil native microbiome diversity in the performance of inoculant Azospirillum brasilense.

Plant growth promoting bacteria (PGPB) have been used as integrative inputs to minimize the use of chemical fertilizers. However, a holistic comprehension about PGPB-plant-microbiome interactions is still incipient. Furthermore, the interaction among PGPB and the holobiont (host-microbiome association) represent a new frontier to plant breeding programs. We aimed to characterize maize bulk soil and rhizosphere microbiomes in irradiated soil (IS) and a native soil (NS) microbial community gradient (dilution-to-extinction) with Azospirillum brasilense Ab-V5, a PGPB commercial inoculant. Our hypothesis was that plant growth promotion efficiency is a result of PGPB niche occupation and persistence according to the holobiont conditions. The effects of Ab-V5 and NS microbial communities were evaluated in microcosms by a combined approach of microbiomics (species-specific qPCR, 16S rRNA metataxonomics and metagenomics) and plant phenomics (conventional and high-throughput methods). Our results revealed a weak maize growth promoting effect of Ab-V5 inoculation in undiluted NS, contrasting the positive effects of NS dilutions 10-3, 10-6, 10-9 and IS with Ab-V5. Alpha diversity in NS + Ab-V5 soil samples was higher than in all other treatments in a time course of 25 days after sowing (DAS). At 15 DAS, alpha diversity indexes were different between NS and IS, but similar in all NS dilutions in rhizospheric samples. These differences were not persistent at 25 DAS, demonstrating a stabilization process in the rhizobiomes. In NS 10-3 +Ab-V5 and NS 10-6 Ab-V5, Ab-V5 persisted in the maize rhizosphere until 15 DAS in higher abundances compared to NS. In NS + Ab-V5, abundance of six taxa were positively correlated with response to (a)biotic stresses in plant-soil interface. Genes involved in bacterial metabolism of riboses and amino acids, and cresol degradation were abundant on NS 10-3 + Ab-V5, indicating that these pathways can contribute to plant growth promotion and might be a result of Ab-V5 performance as a microbial recruiter of beneficial functions to the plant. Our results demonstrated the effects of holobiont on Ab-V5 performance. The meta-omics integration supported by plant phenomics opens new perspectives to better understanding of inoculants-holobiont interaction and for developing better strategies for optimization in the use of microbial products.

Water limitation intensity shifts carbon allocation dynamics in Scots pine mesocosms

Background and aimsTree species worldwide suffer from extended periods of water limitation. These conditions not only affect the growth and vitality of trees but also feed back on the cycling of carbon (C) at the plant-soil interface. However, the impact of progressing water loss from soils on the transfer of assimilated C belowground remains unresolved.MethodsUsing mesocosms, we assessed how increasing levels of water deficit affect the growth of Pinus sylvestris saplings and performed a 13C-CO2 pulse labelling experiment to trace the pathway of assimilated C into needles, fine roots, soil pore CO2, and phospholipid fatty acids of soil microbial groups.ResultsWith increasing water limitation, trees partitioned more biomass belowground at the expense of aboveground growth. Moderate levels of water limitation barely affected the uptake of 13C label and the transit time of C from needles to the soil pore CO2. Comparatively, more severe water limitation increased the fraction of 13C label that trees allocated to fine roots and soil fungi while a lower fraction of 13CO2 was readily respired from the soil.ConclusionsWhen soil water becomes largely unavailable, C cycling within trees becomes slower, and a fraction of C allocated belowground may accumulate in fine roots or be transferred to the soil and associated microorganisms without being metabolically used.

Influence of Paulownia fortunei (Seem.) Hemsl. roots on preferential flow in the red soil hilly region

Preferential water flow in soil significantly affects runoff, water infiltration, storage, groundwater environment, and soil stability. Plant roots positively affect preferential flow development. This study explored the relationship between the root system of <i>Paulownia fortunei</i> (Seem.) Hemsl. and preferential flow using dyeing tracer test and image analysis techniques. A typical red soil hilly region on the outskirts of Guilin City (Guangxi, China) was selected as the study area. A Bright Blue solution was used to visualize the pathways followed by the infiltrated water in simulated rainfall experiments, and Image Analyzer of Plants was used to analyze the root length, surface area, and volume. The results revealed significant differences in the root surface area density of coarse roots (RSAD-CR) and length index of preferential flow (LI) among soil profiles at various distances from the tree trunk. The root volume density of coarse (RVD-CR) and total roots (RVD-TR), the root length density of coarse roots (RLD-CR), and RSAD-CR were significantly correlated with the characteristics of dyeing morphology. Conversely, the root length density and root surface area density of fine (RLD-FR and RSAD-FR, respectively) and total roots (RLD-TR and RSAD-TR, respectively), and the root volume density of fine roots (RVD-FR) were not significantly correlated with the characteristic parameters of dyeing morphology. The root systems of <i>P. fortunei</i> were critical for enhancing soil water infiltration and developing preferential flow in red soil hilly regions. Coarse roots had a greater impact on the development of preferential flow than fine roots, and root volume had a greater influence on preferential flow development than root length and root surface area. This study contributes to a better understanding of the hydrological cycle at the plant-soil interface in red soil hilly regions.

Synergistic action of humic acid substances and bio-inoculants in guava (Psidium guajava L.): impact on growth traits, fruiting, nutrient profiling and rhizosphere stochiometry in meadow rainy season plant-soil interface

The present investigation was conducted on guava cv. Lalit spaced at 2 m × 1.5 m in meadow plant-soil interface during two consecutive rainy seasons of 2017 and 2018. Foliar application of humic acid was carried out at bud burst stage in two different levels i.e. 30 ml/L (HA30) and 60 ml/L (HA60), bio-inoculants were applied to the rhizosphere of the trees at two combinations, B1: PSB @ 10 ml/plant + Azotobacter chroococcum @ 10 g/plant, and B2: PGPR @ 25 ml/plant + AM fungi @ 25 g/plant along with reduced recommended dose of fertilizers (RDF) of N:P:K (360:740:200) i.e. 90 per cent of RDF (NPK90) and 80 per cent of RDF (NPK80). The experiment was laid out in Randomized Complete Block Design with eight treatment combinations, replicated thrice along with a control. The results showed that application of humic acid at 60 ml/L along with each of PSB and A. chroococcum at 10 ml/plant along with 80 per cent of NPK resulted in growth and fruiting over control. This combination also recorded significant increase in fruit set with marked reduction in fruit drop. Fruit yield was 1.89 times compared to control. Both physical and biochemical fruit quality traits were also significantly affected by this conjoint application. Microbial biomass in terms of actinomycetes, A. chroococcum, PSB and AM fungi were also tremendously increased compared to control. This combination also exhibited considerably greater amount of leaf N (2.55%), leaf P (0.24%) and leaf K (1.32%) under meadow plant-soil interface.

Do plant-soil interactions influence how the microbial community responds to environmental change?

Global change alters ecosystems and their functioning, and biotic interactions can either buffer or amplify such changes. We utilized a long-term nitrogen (N) addition and species removal experiment in the Front Range of Colorado, USA to determine whether a codominant forb and a codominant grass, with different effects on nutrient cycling and plant community structure, would buffer or amplify the effects of simulated N deposition on soil bacterial and fungal communities. While the plant community was strongly shaped by both the presence of dominant species and N addition, we did not find a mediating effect of the plant community on soil microbial response to N. In contrast to our hypothesis, we found a decoupling of the plant and microbial communities such that the soil microbial community shifted under N independently of directional shifts in the plant community. These findings suggest there are not strong cascading effects of N deposition across the plant-soil interface in our system.

Mycotoxin Uptake in Wheat - Eavesdropping Fusarium Presence for Priming Plant Defenses or a Trojan Horse to Weaken Them?

Fusarium mycotoxins represent a major threat for cereal crops and food safety. While previous investigations have described plant biotransforming properties on mycotoxins or metabolic relapses of fungal infections in plants, so far, the potential consequences of radical exposure in healthy crops are mostly unknown. Therefore, we aimed at evaluating whether the exposure to mycotoxins, deoxynivalenol (DON) and zearalenone (ZEN), at the plant-soil interface may be considered a form of biotic stress capable of inducing priming or a potential initiation of fungal attack. To address this, we used atmospheric-pressure scanning microprobe matrix-assisted laser desorption/ionization mass spectrometry imaging to investigate the activation or the inhibition of specific biosynthetic pathways and in situ localization of primary and secondary metabolites in wheat. According to our untargeted metabolomics investigation, the translocation of plant defense metabolites (i.e., hydroxycinnamic acid amide and flavones) follows the mycotoxin accumulation organs, which is the root for ZEN-treated plantlet and culm for DON-treated sample, suggesting a local “defense-on-demand response.” Therefore, it can be hypothesized that DON and ZEN are involved in the eavesdropping of Fusarium presence in soil and that wheat response based on secondary metabolites may operate on multiple organs with a potential interplay that involves masked mycotoxins.

Invasive knotweed modifies predator–prey interactions in the soil food web

Invasive plants often modify the structure of the community of native plants and animals, but their potential impact on the plant–soil interface is poorly studied. In this study, we looked at the impact of invasive knotweed (Reynoutria spp.) on the taxonomic and functional structure of three trophic levels (plants, detritivores and predators). We wanted to determine if knotweed had a cascading impact from plants to predators. The plants and soil invertebrates were sampled in seven sites in northern France in three knotweed cover classes (control, mid and high). Our results showed that knotweed had a low impact on invertebrate communities despite decreasing plant richness and functional diversity. However, we observed that the functional diversity of detritivores (based on palatability traits) and predators (based on feeding traits) were highly correlated in control sites without knotweed, but that this correlation was no longer present in knotweed invaded sites. This result suggests that feeding interactions are an important feature determining community structure in control plots, but that unidentified factors are more important in the presence of knotweed. Consequently, it can be hypothesised that the presence of knotweed disrupts functional linkages within the soil food web, which may ultimately modify ecosystem stability and functioning.

Environmental Control of Phosphorus Acquisition: A Piece of the Molecular Framework Underlying Nutritional Homeostasis.

Homeostasis of phosphorus (P), an essential macronutrient, is vital for plant growth under diverse environmental conditions. Although plants acquire P from the soil as inorganic phosphate (Pi), its availability is generally limited. Therefore, plants employ mechanisms involving various Pi transporters that facilitate efficient Pi uptake against a steep concentration gradient across the plant-soil interface. Among the different types of Pi transporters in plants, some members of the PHOSPHATE TRANSPORTER 1 (PHT1) family, present in the plasma membrane of root epidermal cells and root hairs, are chiefly responsible for Pi uptake from the rhizosphere. Therefore, accurate regulation of PHT1 expression is crucial for the maintenance of P homeostasis. Previous investigations positioned the Pi-dependent posttranslational regulation of PHOSPHATE STARVATION RESPONSE 1 (PHR1) transcription factor activity at the center of the regulatory mechanism controlling PHT1 expression and P homeostasis; however, recent studies indicate that several other factors also regulate the expression of PHT1 to modulate P acquisition and sustain P homeostasis against environmental fluctuations. Together with PHR1, several transcription factors that mediate the availability of other nutrients (such as nitrogen and zinc), light, and stress signals form an intricate transcriptional network to maintain P homeostasis under highly diverse environments. In this review, we summarize this intricate transcriptional network for the maintenance of P homeostasis under different environmental conditions, with a main focus on the mechanisms identified in Arabidopsis.

Root exudates drive soil-microbe-nutrient feedbacks in response to plant growth.

Although interactions between plants and microbes at the plant-soil interface are known to be important for plant nutrient acquisition, relatively little is known about how root exudates contribute to nutrient exchange over the course of plant development. In this study, root exudates from slow- and fast-growing stages of Arabidopsis thaliana plants were collected, chemically analysed and then applied to a sandy nutrient-depleted soil. We then tracked the impacts of these exudates on soil bacterial communities, soil nutrients (ammonium, nitrate, available phosphorus and potassium) and plant growth. Both pools of exudates shifted bacterial community structure. GeoChip analyses revealed increases in the functional gene potential of both exudate-treated soils, with similar responses observed for slow-growing and fast-growing plant exudate treatments. The fast-growing stage root exudates induced higher nutrient mineralization and enhanced plant growth as compared to treatments with slow-growing stage exudates and the control. These results suggest that plants may adjust their exudation patterns over the course of their different growth phases to help tailor microbial recruitment to meet increased nutrient demands during periods demanding faster growth.

Can irrigating more frequently mitigate detrimental heat wave effects on perennial ryegrass growth and persistence?

Heat waves are problematic for grazing livestock systems in regions dependant on temperate (cool-season) pasture species, owing to the often minimal heat tolerance (thermotolerance) of these pastures. A field experiment in north-west Tasmania, Australia, tested the hypothesis irrigating more frequently reduces detrimental heat wave effects on perennial ryegrass (Lolium perenne L.) above-ground growth and short-term persistence (measured via basal frequency). Heat wave conditions were imposed using freestanding infrared heater arrays fitted with a novel control system designed for evaluating heat wave mitigation options. The control system enabled the extent of warming to be regulated, whilst applying an equal infrared flux (heating) to all heated plots. Increasing the frequency of irrigation events suppressed crown temperature (plant-soil interface) elevation under heaters. When irrigation was applied every 2, 5 or 10 days, median crown temperature elevation under heaters equalled 5.5 °C, 6.5 °C and 7.0 °C, respectively. However, detrimental effects of imposed heat wave conditions on perennial ryegrass growth were not mitigated by more frequent irrigation events. This resulted from the small differences in crown temperature elevation between irrigation frequency treatments, combined with supraoptimal crown temperatures occurring <10% of the time during the simulated 10-day heat wave events. The infrequent occurrence of supraoptimal crown temperatures: (i) resulted from mild ambient conditions (mean ambient air temperature, 17.2 °C); and (ii) explains why applied heating only reduced perennial ryegrass growth by 13 kg DM ha−1 day−1 (23%) when heaters were operated, with no residual effect in the accompanying recovery regrowth cycle. Applied heating also had no appreciable effect on perennial ryegrass basal frequency. Under more extreme heat wave conditions, irrigation frequency may have a larger effect on perennial ryegrass tissue temperature and subsequent growth, especially in environments characterised by higher crown temperatures.

An Approach to the study of vessels climber species

The angiosperms are characterized by vessels in wood, and therefore, vessel elements were selected to study them in climber species. Xylem is the specialized tissue that transports water and nutrients from the plant–soil interface to stem and leaves and provides mechanical support and storage. Water is the primary solvent for plant nutrition and metabolism and is essential for photosynthesis, turgor and for transport of minerals, hormones and other molecules. Studies on vessels showed that the characters of vessels can throw some light on the phylogeny of species. The short vessel members with many perforation plates with a single large perforation are most specialized and those that were long with elongate obliquely placed perforation plates with many perforations separated by bars that together give a scalariform appearance are primitive. The degree of specialization of vessel elements can be measured in terms of vessel length, breadth and the number of bars on the end plate of vessels. Vessels show highly evolved and primitive vessel elements. Mostly elongated vessel elements are present in middle region of the stem. During this study the broadest vessels were found in the middle part of the stem of dicots (Clitoria, Daemia and Aristolochia) and root of the monocots (Gloriosa) and the narrowest vessel elements were found in different parts of the species investigated. The present work is supported with line drawings of prepared stained sections, provides a framework of the vessels. This study will be very useful to a wideseries of community, who work with plants.

Preferential water flow: Influence of alfalfa (Medicago sativa L.) decayed root channels on soil water infiltration

Soil water infiltration is an important part of the land surface hydrological cycle, and plays an important role in the hydrological response of the soil, such as soil erosion. High infiltration rates favor an increase in the soil water storage capacity that allows maintaining vegetation restoration in arid and semi-arid regions. Alfalfa (Medicago sativa L.) is a quality perennial legume grassland, which is widely planted in semi-arid areas. In this study, the effects of the root channels formed by the decay of alfalfa on preferential flow were evaluated as a driving force to improve soil water infiltration and soil water supply. A double-ring infiltrometer (30-cm inner diameter and 60-cm outer diameter) was used to measure the infiltration process with the falling head method. Methylene blue was used to visualize the pathways followed by the infiltrated water. The results showed that the initial infiltration rate in the alfalfa grassland increased by 27.7%, compared with the control bare land, and the total cumulative infiltration was 1.13 times higher. The steady infiltration rate of the grassland increased by 31.8% compared to the bare land. The root channel diameters were measured with a Vernier caliper, and the average root channel area (RCA) was calculated through the average root channel diameter (ARCD). The values of ARCD and RCA were significantly and positively correlated with the infiltration rates, being the coefficients of determination 0.815 and 0.789, respectively. Our results indicated that root channels formed by the decayed roots of alfalfa played an important role in increasing soil water infiltration and soil water supply under semi-arid conditions. Our research improves the understanding of the hydrological cycle processes at the plant-soil interface in semi-arid areas.

Fire regime and ecosystem responses: adaptive forest management in a changing world (Part 1)

Although fire is an intrinsic factor in most terrestrial biomes, it is often perceived as a negative disturbance that must be suppressed. The application of successful fire prevention policies can lead to unsustainable fire events for ecosystems adapted to a specific fire regime. In addition, new climate and land use scenarios are influencing fire parameters and ecosystem services. Consequently, adaptive forest and landscape management must include knowledge on vulnerability, resistance and resilience of terrestrial ecosystems. To help address this need, we convened a special issue (divided in two separate parts) to synthesise ongoing research focused on obtaining a better understanding of wildfire response decisions and actions, including preventive management and post-fire restoration. We conceived a collection of research studies covering a wide diversity of geographical settings characterised by different climates and forest types, under scenarios of changing climate and land use. Here, we summarise the key findings from the six papers published in the first section of the special issue. They deal with diverse topics and assessments, such as adaptions to fire regimes, the effects of burn severity on the plant–soil interface, and post-fire management taking advantage of indices obtained from satellite images (dNBR, NDVI), dendrochronology, soil sampling and analysis of biological indicators. We highlight the new knowledge developed to enhance fire management decision making in a time of rapidly changing scenarios around the world.

Effect of stubble-height management on crown temperature of perennial ryegrass, tall fescue and chicory

Defoliating pasture to shorter stubble heights (height above the soil surface) may increase temperature at the plant crown (plant–soil interface). This is especially relevant to summer C3 pasture production in parts of south-eastern Australia, where above-optimal ambient temperatures (≥30°C) are often recorded. A rainfed field experiment in north-west Tasmania, Australia, quantified the effect of stubble-height management on the upper distribution of crown temperatures (90th and 75th percentiles) experienced by three pasture species: perennial ryegrass (Lolium perenne L.), tall fescue (Festuca arundinacea Schreb.; syn. Schedonorus arundinaceus (Schreb.) Dumort.; syn. L. arundinaceum (Schreb.) Darbysh.), and chicory (Cichorium intybus L.). Three stubble-height treatment levels were evaluated: 35, 55 and 115mm. Defoliation to shorter stubble heights (35 or 55mm cf. 115mm) increased the crown temperature of all species in the subsequent regrowth cycle (period between successive defoliation events). In the second summer, defoliating to shorter stubble heights increased the 90th percentile of crown temperature by an average of 4.2°C for perennial ryegrass, 3.6°C for tall fescue and 1.8°C for chicory. Chicory and second-year tall fescue swards experienced less-extreme crown temperatures than perennial ryegrass. This may partly explain why these two species often outyield perennial ryegrass in hotter summer environments than north-west Tasmania, and hence the increasing interest in their use.