Plant Species Interactions Research Articles

Glyphosate-Modulated Biosynthesis Driving Plant Defense and Species Interactions.

Glyphosate has become the best-selling herbicide used in agriculture, horticulture, silviculture, and urban environments. It disrupts the shikimate metabolic pathway and thereby blocks the production of aromatic amino acids, which are the basis for several plant metabolites. Glyphosate residues are reported in soils from diverse environments, but the effects on plant physiology and consequences for species interactions are largely unknown. Here, we emphasize the complexity of these physiological processes, and argue that glyphosate residues modulate biosynthetic pathways, individually or interactively, which may affect interactions between plants and heterotrophic organisms. In this way, glyphosate residues can substantially interfere with plant resistance and the attraction of beneficial insects, both of which are essential elements in integrated pest management and healthy ecosystems.

Experimental drought re‐ordered assemblages of root‐associated fungi across North American grasslands

AbstractPlant‐associated fungi can ameliorate abiotic stress in their hosts, and changes in these fungal communities can alter plant productivity, species interactions, community structure and ecosystem processes.We investigated the response of root‐associated fungi to experimental drought (66% reduction in growing season precipitation) across six North American grassland ecosystem types to determine how extreme drought alters root‐associated fungi, and understand what abiotic factors influence root fungal community composition across grassland ecosystems.Next generation sequencing of the fungal ITS2 region demonstrated that drought primarily re‐ordered fungal species' relative abundances within host plant species, with different fungal responses depending on host identity. Grass species that declined more under drought trended toward less community re‐ordering of root fungi than species less sensitive to drought. Host identity and grassland ecosystem type defined the magnitude of drought effects on community composition, diversity and root colonization, and the most important factor affecting fungal composition was plant species identity.Fungal diversity was less responsive to drought than fungal composition. Across ecosystems, latitude and soil pH were better predictors of fungal diversity than experimental drought. Drought significantly reduced fungal diversity and evenness only in sideoats gramaBouteloua curtipendulaand reduced root colonization only in blue gramaB. gracilis.Our results illustrate that predicting the effects of drought on root‐associated fungi will require attention to host plant identity and ecosystem type. By comparing our findings against soil microbe responses in the same experiment, we propose the hypothesis that fungi in plant roots are less sensitive to drought than fungi inhabiting soils. Our study highlights the importance of studying community‐level re‐ordering of fungal composition for understanding plant responses to climate change.

Global variation in diurnal asymmetry in temperature, cloud cover, specific humidity and precipitation and its association with leaf area index.

The impacts of the changing climate on the biological world vary across latitudes, habitats and spatial scales. By contrast, the time of day at which these changes are occurring has received relatively little attention. As biologically significant organismal activities often occur at particular times of day, any asymmetry in the rate of change between the daytime and night-time will skew the climatic pressures placed on them, and this could have profound impacts on the natural world. Here we determine global spatial variation in the difference in the mean annual rate at which near-surface daytime maximum and night-time minimum temperatures and mean daytime and mean night-time cloud cover, specific humidity and precipitation have changed over land. For the years 1983-2017, we derived hourly climate data and assigned each hour as occurring during daylight or darkness. In regions that showed warming asymmetry of >0.5°C (equivalent to mean surface temperature warming during the 20th century) we investigated corresponding changes in cloud cover, specific humidity and precipitation. We then examined the proportional change in leaf area index (LAI) as one potential biological response to diel warming asymmetry. We demonstrate that where night-time temperatures increased by >0.5°C more than daytime temperatures, cloud cover, specific humidity and precipitation increased. Conversely, where daytime temperatures increased by >0.5°C more than night-time temperatures, cloud cover, specific humidity and precipitation decreased. Driven primarily by increased cloud cover resulting in a dampening of daytime temperatures, over twice the area of land has experienced night-time warming by >0.25°C more than daytime warming, and has become wetter, with important consequences for plant phenology and species interactions. Conversely, greater daytime relative to night-time warming is associated with hotter, drier conditions, increasing species vulnerability to heat stress and water budgets. This was demonstrated by a divergent response of LAI to warming asymmetry.

Functional Diversity Effects of Vegetation on Runoff to Design Herbaceous Hedges for Sediment Retention

Background: Functional diversity effects on ecosystem processes, like on soil erosion, are not fully understood. Runoff and soil erosion in agricultural landscapes are reduced by the hydraulic roughness (HR) of vegetation patches, which furthers sediment retention. Vegetation with important stem density, diameters, leaf areas, and density impact the HR. A functional structure composed of these negatively correlated traits involved in the increase of the HR would constitute a positive effect of the functional diversity. Methods: Runoff simulations were undertaken on four mono-specific and two multi-specific communities, using herbaceous plant species from North-West Europe, presenting six contrasting aboveground functional traits involved in the HR increase. Results: An effect of dominant traits in the community was found on the HR, identified as the community-weighted leaf density. The non-additive effect of functional diversity on the HR could be explained by the presence of species presenting large stems in the communities with high functional diversity. Conclusion: We argued that functional diversity effect on the HR could change due to idiosyncratic effects of the plant traits, which would be influenced by soil properties, phylogeny diversity, and plant species interactions. These findings constitute an advancement in the understanding of plant trait assemblage on runoff and soil erosion processes.

Plant-Soil Feedbacks and Facilitation Influence the Demography of Herbaceous Alpine Species in Response to Woody Plant Range Expansion

Plant species migrations, or range shifts, in response to changing climate are one of many interacting factors influencing plant population and community dynamics in an era of global change. Range shifts may cause novel assemblages of competing species because species may respond to changing climate at different rates. Range-expanding species may directly influence resident species through resource competition or indirectly by modifying the local environment both aboveground and belowground. Further, range-expanding plant species can create novel plant-soil feedbacks (PSFs) by altering soil microbial community structure and function and the interactions of resident plant species with microbial symbionts. These changes can have important implications for resident plant population dynamics and their ability to coexist with novel competitors. Here we test the impacts of competitive interactions and plant-soil feedbacks (PSFs) of a range-expanding sagebrush species (Artemisia. rothrockii) on the demography and population growth rates of two resident alpine plant species (Koeleria macrantha and Eriogonum ovalifolium). We use an experimental, multi-year field approach combined with integral projection modeling to determine how PSFs and competition influence species coexistence in both the historic and range expansion zone of A. rothrockii. We find that sagebrush has an overall net negative effect on herbaceous plant demography, primarily due to negative PSFs for plants growing in sagebrush-conditioned soil. However, these negative soil effects are partially buffered via facilitation effects for herbs growing under or nearby sagebrush canopies. In general, population growth rates were more sensitive to survival than other demographic rates, furthermore this sensitivity to survival was higher for herbaceous species in sagebrush soils. Identifying the major drivers of plant population dynamics and species interactions remains an important and unresolved question in ecology. PSFs are a central mechanism influencing plant species interactions, yet the majority of PSF research has made little direct connection between plant population dynamics and PSFs in situ. We believe that utilizing a field-based approach, focusing on multiple components of plant demography, is an important next step in understanding the role of PSFs and species interactions in a rapidly changing world.

How does timing of flowering affect competition for pollinators, flower visitation and seed set in an early spring grassland plant?

Knowledge on how the timing of flowering is related to plant fitness and species interactions is crucial to understand consequences of phenological shifts as they occur under climate change. Early flowering plants may face advantages of low competition for pollinators and disadvantages of low pollinator abundances and unfavourable weather conditions. However, it is unknown how this trade-off changes over the season and how the timing affects reproductive success. On eight grasslands we recorded intra-seasonal changes in pollinators, co-flowering plants, weather conditions, flower visitation rates, floral longevity and seed set of Pulsatilla vulgaris. Although bee abundances and the number of pollinator-suitable hours were low at the beginning of the season, early flowers of P. vulgaris received higher flower visitation rates and estimated total number of bee visits than later flowers, which was positively related to seed set. Flower visitation rates decreased over time and with increasing number of co-flowering plants, which competed with P. vulgaris for pollinators. Low interspecific competition for pollinators seems to be a major driver for early flowering dates. Thus, non-synchronous temporal shifts of co-flowering plants as they may occur under climate warming can be expected to strongly affect plant-pollinator interactions and the fitness of the involved plants.

Small-sized fish as possible seed dispersers: disclosing novel fish and plant species interactions in the Pantanal wetland

ABSTRACTSeed dispersion is a critical process to vegetation dynamics which is particularly complex in mosaic-like landscapes as the Pantanal wetlands. We analyzed some aspects of ichthyochory in the Pantanal flooded grasslands. The fish were collected and had their whole intestinal contents removed and submitted to suitable germination conditions for 179 days. We collected 661 specimens belonging to 40 species. Feces from Astyanax lacustris, Poptela paraguayensis, Moenkhausia sanctafilomena and Moenkhausia bonita produced 15 seedlings of herbaceous plant of the species Ludwigia inclinata, Ludwigia leptocarpa and a non-identified monocotyledon. A total of 30.4 g of fecal mass was recovered with a rate of 0.49 seedling.gram−1. There is a positive relation between the number of seedlings obtained and the amount of fish fecal mass (g). Currently, Pantanal landscape dynamics is under rising pressure of field compartmentalization due to man-made roads which restrains fish transit.

Effects of Earthworms and Agricultural Plant Species on the Soil Nematode Community in a Microcosm Experiment

Both earthworms and plants may affect the soil nematode community. However, the effects of earthworms and plant species interactions on soil nematode community are poorly understood. We explored how an epigeic earthworm Eisenia fetida affects the soil nematode community in systems with three representative plants (wheat, cotton and cabbage) which were grown in pots with or without added earthworms under greenhouse conditions. Earthworm presence decreased the abundance of total nematode and all four nematode trophic groups, except for the fungivore and predator/omnivore nematodes in wheat systems, but increased the genus richness of nematode in all treatments. Due to plant identity and different root exudates, plants had significant effects on soil nematode abundance. Compared with the no plant and without earthworm treatment, wheat and cabbage had the higher stimulation of the abundance of total nematode, bacterivores and fungivores, and cotton had the higher stimulation of the abundance of fungivores and predators-omnivores; whereas earthworm presence mostly weakened the stimulation effects of plant species on soil nematode abundance which indicated earthworms had the enhanced effects in the presence of plants. The interaction affected soil nematode abundance (total nematodes, bacterivore, fungivore and omnivore-predators) and community diversity indices (diversity index H′, evenness index J′, community maturity index ∑MI, Simpson dominance index λ and nematode channel ratio NCR). Principal component analysis showed that plant species affected soil nematode community composition. Redundancy analysis indicated plant species and biomass accounted for 41.60% and 34.13% of the variation in soil nematode community structure, respectively; while earthworms explained only 6.13%. Overall, current study suggest that earthworm could inhibit nematode abundance; whereas, plants have exerted greater influences on nematode community structure than earthworm presence due to their species-specific effects on different trophic groups of nematodes.

Plant traits and species interactions along gradients of N, P and K availabilities

Abstract Plant performance is driven by nutrient availability. So far, studies on plant nutrient relationships mostly focused on nitrogen (N) and phosphorus (P), whereas potassium (K) received less attention. We evaluated whether plant responses to variation in nutrient availability are similar or different for the nutrients N, P and K and whether the same plant traits are decisive for the competitive ability of species along gradients of N, P and K availabilities. We studied plant trait responses of three temperate perennial grass species (Alopecurus pratensis, Agrostis capillaris and Anthoxanthum odoratum, each dominant under N limitation, P limitation and K limitation, respectively). Each gradient consisted of eight treatments (N1–N8, P1–P8, K1–K8), with N:P:K supply rates being 1:0.8:6 (N1), 128:0.8:6 (N8), 12:0.075:6 (P1), 12:9.6:6 (P8), 12:0.8:0.56 (K1) and 12:0.8:72 (K8) (total supply per plant individual in mg). Plant individuals were kept either in single‐species pots (intraspecific competition) or in mixed‐species pots (interspecific competition). After 2 months, plant biomass, leaf and root traits and root enzyme activity were measured. Most below‐ground traits (e.g. total root length, root diameter) responded most strongly to competition as predictor variable and only secondly to the type of nutrient or their supply rates (unlike RGRTotal and SLA). Leaf chlorophyll content and root enzyme activity responded most strongly to supply rate of nutrients and the interaction of nutrient type and supply rate, respectively. In line with our prediction, A. pratensis was the superior competitor under N limitation and A. odoratum was the superior competitor under K limitation (assessed by relative dominance [RD] and relative competitive strength [RCS]). Both species showed high investment in total root length. Opposite to our expectation, A. capillaris was a bad competitor under P limitation, with low root length but higher root phosphatase activity. Our results indicate that below‐ground plant traits are decisive in nutrient‐related competition between plant species. Further, competitive strength is determined by a high total root length per soil volume both under N and K limitation. Under P limitation, the model species A. capillaris showed a weak competitive performance either because it was lacking colonization with mycorrhiza and/or the high investment in phosphatase activity posed a trade‐off with higher N investment in phosphatase production. A free Plain Language Summary can be found within the Supporting Information of this article.

Competitive reversal between plant species is driven by species‐specific tolerance to flooding stress and nutrient acquisition during early marsh succession

Abstract Understanding plant species interactions along successional trajectories is critical for managing and restoring ecosystems, as both resource availability and abiotic stresses change over time to affect competitive outcomes and species distributions. Newly created ecosystems experience a succession of plant species and rapid changes in resource availability, which may influence the outcome of biotic interactions. How these biotic interactions vary along abiotic gradients in early successional systems is not well understood. Here, we tested the hypothesis that species‐specific tolerances to flooding would influence their relative ability to capture resources (i.e. nutrients) and affect competition intensity between pioneer and secondary successional species in an early successional created tidal marsh. We transplanted a competitively dominant higher marsh species, saltmeadow cordgrass (Spartina patens), across an elevation gradient within and outside of clones of a pioneer stress‐tolerant low marsh species, smooth cordgrass (S. alterniflora). Within 6 months, S. alterniflora had suppressed the stature and growth of S. patens; however, the magnitude of this competitive effect increased at lower marsh elevations where S. alterniflora was more efficient at capturing available nitrogen (N). In unvegetated areas, where S. patens vigour was high, the amount of available N was approximately 40 times greater than within S. alterniflora clones. Synthesis and applications. Our results demonstrate that competition intensity of the stress‐tolerant species over the competitive species depended on relative resource capture in response to abiotic stress. Managing for specific vegetation communities in marsh restoration, therefore, requires insight into these relationships and interactions. Specifically, marsh restoration in high nutrient environments will limit the succession to high density competitive species due to competition with stress‐tolerant pioneer species, particularly at lower elevations.

Mycorrhizal network assembly in a community context: The presence of neighbours matters

Abstract Understanding the factors and mechanisms driving the structure of ecological networks is a challenge for community ecologists. Notably, it remains unclear whether observed interaction patterns between two trophic groups are a result of (a) preferential partner selection between groups, or (b) species interactions within groups. We conducted an experiment in order to disentangle these two drivers, using the plant–mycorrhizal symbiosis as a model system. We followed mycorrhizal colonization of plant roots growing either with or without neighbours. This allowed us to assess the relative importance of interaction within trophic groups (here, plant‐to‐plant interactions) on ecological network assembly. Results showed that plants were not equally affected by the presence of neighbours and that network nestedness was higher when plants grew without neighbours. We also found a poor correlation between the centrality (i.e., standardized number of interactions) of plant species grown in communities and those grown without neighbours, while the reverse was true for mycorrhizal fungi. This suggests that the optimum level of specificity or generalism in mycorrhizal selection is not a fixed plant trait, but a plastic, context‐dependent one. Synthesis. Our results show that ecological networks are not only shaped by preferential partner selection, but also by interactions within a given trophic group. This finding should be considered in future modelling exercises on ecological network dynamics. Moreover, our nestedness results suggest that in the presence of multiple host plants, mycorrhizal fungi display preferences for specific interactions, suggesting that local plant diversity may shape mycorrhizal fungal community structure.

The role of plant species and soil condition in the structural development of the rhizosphere.

Roots naturally exert axial and radial pressures during growth, which alter the structural arrangement of soil at the root–soil interface. However, empirical models suggest soil densification, which can have negative impacts on water and nutrient uptake, occurs at the immediate root surface with decreasing distance from the root. Here, we spatially map structural gradients in the soil surrounding roots using non‐invasive imaging, to ascertain the role of root growth in early stage formation of soil structure. X‐ray computed tomography provided a means not only to visualize a root system in situ and in 3‐D but also to assess the precise root‐induced alterations to soil structure close to, and at selected distances away from the root–soil interface. We spatially quantified the changes in soil structure generated by three common but contrasting plant species (pea, tomato, and wheat) under different soil texture and compaction treatments. Across the three plant types, significant increases in porosity at the immediate root surface were found in both clay loam and loamy sand soils and not soil densification, the currently assumed norm. Densification of the soil was recorded, at some distance away from the root, dependent on soil texture and plant type. There was a significant soil texture × bulk density × plant species interaction for the root convex hull, a measure of the extent to which root systems explore the soil, which suggested pea and wheat grew better in the clay soil when at a high bulk density, compared with tomato, which preferred lower bulk density soils. These results, only revealed by high resolution non‐destructive imagery, show that although the root penetration mechanisms can lead to soil densification (which could have a negative impact on growth), the immediate root–soil interface is actually a zone of high porosity, which is very important for several key rhizosphere processes occurring at this scale including water and nutrient uptake and gaseous diffusion.

Plant invasion correlation with climate anomaly: an Indian retrospect

Plant invasion is highly responsive to rising temperature, altered precipitation and various anthropogenic disturbances. Therefore, climate anomalies might provide opportunities to identify the relationship of past climate in deriving the distribution of invasive species and to detect their probable future distribution. In this work, we studied the correlation of climate anomaly i.e. temperature and precipitation with an indicative map of plant invasive species (1° grid) of India. The indicative map was generated through the plant data available from the project ‘Biodiversity Characterization at Landscape Level’. Climate anomaly was calculated and represented by average temperature and precipitation using ‘Climate Research Unit’ data for the period of 1901 to 2000. A comparison of local geographically weighted regression (GWR) model and a global ordinary least square regression (OLS) model was carried out for statistical analysis to depict the correlation at 1° spatial grids. Overall, 20,501 records with a total of 9112 unique plots and 161 unique invasive species were recorded in the database that shows a maximum of 15 invasive species in a 0.04 ha nested quadrat. Cumulative analysis showed a maximum of 53 invasive species at 1° grid. Individually, GWR could reveal a significant correlation with invasive species distribution for temperature anomaly (r2 = 0.73, AIC= 2206) and precipitation anomaly (r2 = 0.74, AIC= 2221), while OLS model did not offer a good correlation (r2 2400) compared to GWR. Combination of temperature and precipitation anomaly (shared model) showed an improved spatial correlation (r2 > 0.75) using GWR. Variation partitioning revealed the dominant influence (> 0.40 of variation) of temperature anomaly over Deccan Peninsula, Himalaya and North East zone. Influence of precipitation anomaly was more prominent over arid and semi-arid zone explaining > 0.35 of variation. Results revealed the strength of GWR to see the interaction of invasive plant species w.r.t. climate anomalies that explain the influence of spatial variation due to heterogeneity at varying neighbour distances. The significant correlation of invasive species with both the anomalies revealed the affinity of invasive species towards warmer, drier and wet places. This gives an indication that the distribution of invasive species could be triggered by climate anomaly. The use of other predictor variables (i.e. edaphic and anthropogenic) could be an inclusive input in a future perspective.

Study on nitrogen removal from rice paddy field drainage by interaction of plant species and hydraulic conditions in eco-ditches.

Eco-ditches (ecological ditches) not only drain water from rice paddies, but also facilitate the removal of nitrogen (N). We established an experiment with both static and flowing water in 2017 to observe N removal from rice paddy drainage by eco-ditches containing three different types of monoculture vegetation: Zizania aquatica, Canna indica L., and Pontederia cordata. Results showed that ammonia volatilization and plant uptake contributed little to N removal. Harvest of Z. aquatica from the eco-ditch during the late growing season had an appreciable effect on N removal. However, harvest of C. indica L. and P. cordata had negligible effects. During static test, the concentration of total N (TN) and ammonium N (NH4+-N) and the pH all decreased from the surface to the bottom of water. The concentration of nitrate N (NO3--N) did not exhibit stratification. In a flowing water experiment, ditches with Z. aquatica, C. indica L., and P. cordata had the following average removal rates: TN 15.8%, 11.6%, and 27.9%; NO3--N 4.2%, 8.4%, and 17.8%; NH4+-N 22.8%, 16.4%, and 37.5%, respectively. The removal rates of TN and NH4+-N decreased with the increase of water level, while that of NO3--N increased significantly. Nitrogen removal rates decreased with the increase of influent TN concentration or flow rate. Nitrogen removal rate of P. cordata ditch was highly dependent on the influent TN concentration, but the flow rate was not as important due to the great drag caused by its large density. While the contrary was observed in the C. indica L. ditch. For Z. aquatica ditch, both the flow rate and the TN concentration had a strong negative correlation with the N removal rate.

Plant Secondary Metabolite Diversity and Species Interactions

Ever since the first plant secondary metabolites (PSMs) were isolated and identified, questions about their ecological functions and diversity have been raised. Recent advances in analytical chemistry and complex data computation, as well as progress in chemical ecology from mechanistic to functional and evolutionary questions, open a new box of hypotheses. Addressing these hypotheses includes the measurement of complex traits, such as chemodiversity, in a context-dependent manner and allows for a deeper understanding of the multifunctionality and functional redundancy of PSMs. Here we review a hypothesis framework that addresses PSM diversity on multiple ecological levels (α, β, and γ chemodiversity), its variation in space and time, and the potential agents of natural selection. We use the concept of chemical information transfer as mediator of antagonistic and mutualistic interaction to interpret functional and microevolutionary studies and create a hypothesis framework for understanding chemodiversity as a factor driving ecological processes.

Allelopathic effect of two medicinal plants on seed germination, seedling growth and grain production of purslane (Portulaca oleraceae L.) weed

<p>A laboratory factorial (2 × 5) experiment was carried out based on completely randomized block in four replications to evaluate the effect of plant species and concentration of their allelopathic extracts on seed germination and seedling growth of purslane weed (<em>Portulaca oleraceae</em> L.). The first factor studied was plant species (<em>Artemisia sieberi </em>and <em>Salvia syriaca</em>) and the second one the concentration percentage of plant ethanol extract (0.0, 5 %, 10 %, 15 % and 20 %). The effect of <em>Artemisia </em>on<em> </em>germination reduction of purslane<em> </em>was stronger compared to <em>Salvia.</em> The results indicated that higher extract concentration led to decreased germination percentage, germination speed and seedling growth indices of purslane including leaf length, leaf number, leaf width, leaf dry mass, stem mass and stem length. The effect of <em>Artemisia </em>was higher than that of <em>Salvia</em>. In a complementary experiment, the effect plant residues of <em>Artemisia </em>and <em>Salvia </em>(0.0, 1, 2, 3 and 4 g kg<sup>-1</sup> soil) were evaluated in a factorial experiment base on completely randomized block design with three replications. The results of field experiment showed that plant residues significantly (P ≤ 0.01) reduced capsule number per plant, seed number per capsule, seed production and shoot dry mass, while its effect on 1000-seed mass was not substantial. The effect of plant species and the interaction of plant species and their allelopathic extracts concentration had no major impact on the above-mentioned properties. The increase in plant residues in soil, led to the reduction of growth and seed production of purslane induced by plant number per unit area and capsule per plant. <em>Artemisia sieberi </em>Bess<em>. </em>and<em> Salvia syriaca </em>L.<em> </em>residues can be successfully used for non-chemical control of purslane weed.</p>

Diversified Forage Cropping Systems and Their Implications on Resilience and Productivity

Plant diversity is associated with resilient ecosystems. Loss of plant biodiversity triggered by anthropogenic and climatic factors jeopardizes environmental stability and sustainable forage production. The understanding of biodiversity mechanisms and functional traits of species can help to design forage production systems to buffer against perturbations. Resilience and productivity are linked to plant species characteristics and interactions that enable them to recover from adverse conditions and compensate for the loss of susceptible species. Benefits of diversified crops including enhanced carbon assimilation, nitrogen fixation, and turnover are transferred to soil microbes which in return contribute to resilience against drought and poor soil fertility. In the absence of disturbances, these mechanisms are credited for stability and climax ecosystems. Cultivated systems are more fragile because management interferes with many functions while maintaining few. Strategies that sustain an entire range of functions can increase production regardless of climatic and management factors. This has been demonstrated in binary mixtures of cool season grasses including meadow bromegrass (Bromus biebersteinii Roem. & Schult.), orchardgrass (Dactylis glomerata L.), smooth bromegrass (Bromus inermis Leyss.), and intermediate wheatgrass (Thinopyrum intermedium (Host) Barkworth & D.R. Dewey) with alfalfa (Medicago sativa L.). Suitable combinations of perennial species and cultivars bred for compatible traits can enhance resilience and productivity in a wide range of ecosystems.

Differentiating plant functional types using reflectance: which traits make the difference?

AbstractAbiotic ecosystem properties together with plant species interaction create differences in structural and physiological traits among plant species. Certain plant traits cause a spatial and temporal variation in canopy reflectance that enables the differentiation of plant functional types, using earth observation data. However, it often remains unclear which traits drive the differences in reflectance between plant functional types, since the spectral regions in which electromagnetic radiation is influenced by certain plant traits are often overlapping. The present study aims to assess the relative (statistical) contributions of plant traits to the separability of plant functional groups using their reflectance. We apply the radiative transfer model PROSAIL to simulate optical canopy reflectance of 38 herbaceous plant species based on field‐measured traits such as leaf area index, leaf inclination distribution, chlorophyll content, carotenoid content, water and dry matter content. These traits of the selected grassland species were measured in an outdoor plant experiment. The 38 species differed in growth form and strategy types according to Grime′s CSR model and hence represented a broad range of plant functioning. We determined the relative (statistical) contribution of each plant trait for separating plant functional groups via reflectance. Therein we used a separation into growth forms, that is graminoids and herbs, and into CSR strategy types. Our results show that the relative contribution of plant traits to differentiate between the examined plant functional types (PFT) groups using canopy reflectance depends on the PFT scheme applied. Plant traits describing the canopy structure were more important in this regard than leaf traits. Accordingly, leaf area index (LAI) and leaf inclination showed consistently high importance for separating the examined PFT groups. This indicates that the role of canopy structure for spectrally differentiating PFT might have been underestimated.

Nutrient foraging by mycorrhizas: From species functional traits to ecosystem processes

Abstract Plant roots and the associated mycorrhizal fungal hyphae often selectively proliferate into patchily distributed soil nutrient hotspots, but interactions between these two components of a mycorrhizal root system are usually ignored or experimentally isolated in nutrient foraging studies. From studies in which both roots and mycorrhizal hyphae had access to nutrient hotspots, we compiled data on root foraging precision (increase in roots in nutrient hotspots relative to outside hotspots) of plant species from different ecosystems, ranging from temperate grasslands to subtropical forests. We found that root foraging precision across the wide range of plant species was strongly influenced by root morphology and mycorrhizal type. The precision of root nutrient foraging, as a plant functional trait, may coordinate with other root traits that are related to the economics of nutrient acquisition. High foraging precision is expected to associate with the strategy of fast return on the investment in roots, such as low construction cost, high metabolic rate and rapid turnover. Nutrient foraging by mycorrhizal fungi alone may be influenced by functional traits such as hyphal exploration distance, hyphal turnover, and hyphal uptake capacity and efficiency, but such data are limited to a small portion of mycorrhizal fungal species. We propose a conceptual framework in which to simulate nitrogen and phosphorus acquisition from both nutrient hotspots and outside hotspots in mixed‐species plant communities. Simulation outputs suggest that plant species with varying root morphology and mycorrhizal type can be adaptive to a range of nutrient heterogeneity. Although there are still knowledge gaps related to nutrient foraging, as well as many unexplored plant and fungal species, we suggest that scaling nutrient foraging from individual plants to communities would advance understanding of plant species interactions and below‐ground ecosystem function. A plain language summary is available for this article.

Ecological responses of Stipa steppe in Inner Mongolia to experimentally increased temperature and precipitation 5: Synthesis and implications

A randomised block experiment was conducted to study the response of plant community characteristics (biomass, density and diversity) and ecosystem carbon exchange processes to warming, increased precipitation and their combination on Stipa steppe in Inner Mongolia. Increased precipitation enhanced the effect that warming had in promoting community diversity and biomass. Increased precipitation directly increased net ecosystem exchange and gross ecosystem productivity, although ecosystem respiration and soil respiration also increased. However, warming did not have a significant effect on net ecosystem exchange and gross ecosystem productivity, whereas ecosystem respiration and soil respiration were significantly decreased by warming. All carbon flux processes had a significantly positive correlation with soil moisture. However, the carbon sequestration processes, gross ecosystem productivity and net ecosystem exchange, were significantly negatively correlated with temperature, contrary to carbon emission processes, soil respiration and ecosystem respiration. Results suggest that Stipa steppe may be benefited by future climate change, as the predicted precipitation is increasing with warming in Inner Mongolia. However, it is hard to predict the feedback of Stipa steppe to climate, because of the uncertainty in magnitude and temporal dynamics of climate change. To reveal the mechanism of the observed responses, further studies are suggested in this region on the effects of altered climate variables on plant species interactions, soil organic carbon composition, soil extracellular enzyme activity, microbial biomass and microbial respiration.