Alter Plant Community Composition Research Articles

Vegetation responses to large dam removal on the Elwha River, Washington, USA

Large dam removal can trigger changes to physical and biological processes that influence vegetation dynamics in former reservoirs, along river corridors downstream of former dams, and at a river’s terminus in deltas and estuaries. We present the first comprehensive review of vegetation response to major fluvial disturbance caused by the world’s largest dam removal. After being in place for nearly a century, two large dams were removed along the Elwha River, Washington, USA, between 2011 and 2014. The exposure, erosion, transport, and deposition of large volumes of sediment and large wood that were impounded behind the dams created new fluvial surfaces where plant colonization and growth have occurred. In the former reservoirs, dam removal exposed ~290 ha of unvegetated sediment distributed on three main landforms: valley walls, high terraces, and dynamic floodplains. In addition to natural revegetation in the former reservoirs, weed control and seeding and planting of desirable plants influenced vegetation trajectories. In early years following dam removal, ~20.5 Mt of trapped sediment were eroded from the former reservoirs and transported downstream. This sediment pulse, in combination with transport of large wood, led to channel widening, an increase in gravel bars, and floodplain deposition. The primary vegetation responses along the river corridor were a reduction in vegetated area associated with channel widening, plant establishment on new gravel bars, increased hydrochory, and altered plant community composition on gravel bars and floodplains. Plant species diversity increased in some river segments. In the delta, sediment deposition led to the creation of ~26.8 ha of new land surfaces and altered the distribution and dynamics of intertidal water bodies. Vegetation colonized ~16.4 ha of new surfaces: mixed pioneer vegetation colonized supratidal beach, river bars, and river mouth bars, and emergent marsh vegetation colonized intertidal aquatic habitats. In addition to the sediment-dominated processes that have created opportunities for plant colonization and growth, biological processes such as restored hydrochory and anadromous fish passage with associated delivery of marine-derived nutrients may influence vegetation dynamics over time. Rapid changes to landforms and vegetation growth were related to the large sediment pulse in the early years following dam removal, and the rate of change is expected to attenuate as the system adjusts to natural flow and sediment regimes.

Exotic herbivores and fire energy drive standing herbaceous biomass but do not alter compositional patterns in a semiarid savanna ecosystem

AbstractQuestionsFire regime alterations are pushing open ecosystems worldwide past tipping points where alternative steady states characterized by woody dominance prevail. This reduces the frequency and intensity of surface fires, further limiting their effectiveness for controlling cover of woody plants. In addition, grazing pressure (exotic or native grazers) can reinforce woody encroachment by potentially reducing fine‐fuel loads. We investigated the effects of different fire energies on the herbaceous plant community, together with mammalian wildlife herbivory (exotic and native combined) exclusion, to inform best management practices.LocationTexas semi‐arid savanna, southern Great Plains, USA.MethodsWe conducted an experiment in which we manipulated fire intensity and herbivore access to herbaceous biomass in a split‐plot design. We altered fire energy via fuel addition rather than applying fire under different environmental conditions to control for differences in standing biomass and composition attributable to differential plant physiological status and fire season.ResultsHigh‐energy fire did not reduce herbaceous biomass or alter plant community composition, although it did increase among‐plot variability in composition and forb biomass relative to low‐energy fire and non‐burned controls. Grazing pressure from native and non‐native mammalian herbivores reduced above‐ground herbaceous biomass regardless of fire treatments, but did not alter community composition.ConclusionsManagers seeking to apply high‐intensity prescribed fire to reduce woody encroachment will not negatively impact herbaceous plant productivity or alter community composition. However, they should be cognizant that repeated fires necessary for greatly reducing woody plants in heavily invaded areas might be difficult to accomplish due to fine‐fuel reduction from wild herbivores. High fencing to restrict access by wildlife herbivores or culling might be necessary to build fuels sufficient to conduct high‐intensity burns for woody‐plant reduction.

Warming‐induced functional shifts in the decomposer community interact with plant community compositional shifts to impact litter decomposition

Abstract Climate warming is altering plant and soil microbial communities, with important implications for ecosystem processes like litter decomposition. As warming alters plant community composition, the quality of litter will change. Further, shifts in microbial community activity and/or composition will alter microbial function. However, it is not yet completely understood how these shifts will interact to drive decomposition. We explored how changes in plant and microbial communities interact to influence litter decomposition using a 15‐year‐old grassland warming experiment. Previous studies within this system have shown that warming shifted the microbial community in ways that accelerate litter decomposition while simultaneously shifting the plant community in ways that may slow decomposition. Specifically, warming increased abundance of Sorghastrum nutans, while decreasing abundance of the previously dominant Schizachyrium scoparium. Using a series of lab‐based microcosm experiments, we examined the rate at which eight common grasses and, separately, varying abundances of S. nutans and S. scoparium decomposed. Using litter and soil from the warming experiment, we then incubated soils from warmed or control plots with different abundances of S. nutans and S. scoparium in a reciprocal design. We found S. nutans to be the slowest‐decomposing grass in our system. Further, decomposition slowed as S. nutans increased and S. scoparium decreased. When examining the interaction of plant and microbial communities, decomposition was generally greater early in our experiment as the relative abundance of S. scoparium increased. However, soil microbial community origin and litter composition interacted significantly. Specifically, decomposition increased with greater relative abundance of S. scoparium on soils derived from control plots, while litter composition did not shape rates of decomposition on soils from warmed plots. The influence of litter species on decomposition waned in the later stages of the experiment when decomposition was driven by microbial community origin. These results suggest that warming‐induced changes in microbial community function may interact with changes in plant litter composition to mitigate the impacts of warming on rates of decomposition. This emphasizes the importance of considering concurrent warming‐induced changes in both plant and microbial communities on ecosystem processes like decomposition. Read the free Plain Language Summary for this article on the Journal blog.

Experimental climate change in desert steppe reveals the importance of C4 plants for ecosystem carbon exchange

Global climate change has greatly altered plant community composition and affected ecosystem carbon exchange of grasslands. However, the influences of long-term increasing temperature and precipitation on the composition of plant community and the ecosystem carbon exchange in degraded desert steppe remain unclear. After seven years of simulated climate warming (ambient temperature, W0, 2 ℃ and 4 ℃ increase in temperature, W1 and W2) and increasing precipitation (plant growing season precipitation, P0, 25% and 50% increase in precipitation, P1 and P2), we recorded the composition of plant community, the moisture and temperature of soil and calculated net ecosystem CO2 exchange (NEE). Results showed that 1) long-term warming and increasing precipitation improved the cover and height of C4 plants in the plant community, while decreasing the cover and density of C3 plants. 2) Climate warming and increasing precipitation significantly increased NEE. Compared with W0P0, the mean NEE in the plant growing season increased by 115% in W2P2. 3) Redundancy analysis showed that soil moisture content and the height and density of C4 plants significantly explained ecosystem carbon exchange (P < 0.01), while the effect of C3 plants on ecosystem carbon exchange was insignificant (P > 0.01). Therefore, our research revealed that warming and increasing precipitation positively affected ecosystem carbon exchange in degraded desert steppe through changes in plant community composition, and C4 plants will play a vital role in ecosystem carbon exchange in desert steppe under climate change.

Beyond the Hydro-Regime: Differential Regulation of Plant Functional Groups in Seasonal Ponds

Plant community assembly can be influenced by many environmental factors. In seasonal wetlands, most studies focus on the considerable variation that occurs from the hydro-regime (patterns of inundation and desiccation). Other factors and their interactions also influence plants but are seldom studied, including nutrient and thatch levels. Furthermore, the responses of aquatic and terrestrial functional groups can provide important insights into patterns of cover and richness. The aim of this study was to evaluate how algae and plant functional groups (aquatic and terrestrial plants) respond to variation in hydro-regime (stable and unstable), nutrient addition (none and added), and thatch (none, native plants, and exotic plants) addition. We measured algal cover, total species richness, and the cover of the functional groups over two years. Algal cover increased with unstable hydroperiods and the addition of nutrients. Algae were also negatively associated with aquatic plant cover and positively associated with terrestrial plant cover. Aquatic plant cover increased with a stable hydro-regime and decreased with increased thatch. Terrestrial plant cover increased with an unstable hydro-regime and decreased with thatch addition. Thatch accumulation and excess nutrients can be linked to human activities, which directly and indirectly alter plant community composition. The interactions of these factors with the hydro-regime should be considered when evaluating a plant community’s response to changing environmental conditions. Overall, these results are necessary for the conservation and management of essential wetland functions and services.

Mycorrhizal fungi mitigate nitrogen losses of an experimental grassland by facilitating plant uptake and soil microbial immobilization

Nitrogen (N) is one of the most limited nutrients of terrestrial ecosystems, whose losses are prevented in tightly coupled cycles in finely tuned systems. Global change-induced N enrichment through atmospheric deposition and application of vast amounts of fertilizer nowadays challenge the terrestrial N cycle. Arbuscular mycorrhizal fungi (AMF) are known drivers of plant-soil nutrient fluxes, yet a comprehensive assessment of AMF involvement in N cycling under global change is still lacking. Here we simulated N enrichment by fertilization in experimental grassland microcosms grown under greenhouse conditions in the presence or absence of AMF and steadily monitored different N pathways over nine months. We found that N enrichment by fertilization decreased the relative abundance of legumes, and the plant species dominating the plant community changed from grasses to forbs in the presence of AMF based on aboveground biomass. AMF always maintained plant N: phosphorus (P) ratio between 14 and 16, no matter changes in the soil N availability. Shifting plant N:P ratios due to the increased plant N and P uptake thus might be a primary pathway of AMF altering plant community composition. Furthermore, we constructed a comprehensive picture of AMFs' role in N cycling, highlighting that AMF reduced N losses primarily by mitigating N leaching, while N2O emissions played a marginal role. AMF reduced N2O emissions directly through the promotion of N2O-consuming denitrifiers. The underlying mechanism for reducing N leaching is mainly the AMF-mediated improved nutrient uptake and AMF-associated microbial immobilization. Our results indicate that synergies between AMF and other soil microorganisms cannot be ignored in N cycling, and the integral roles of AMF in N cycle terrestrial ecosystems can buffer the upcoming global changes.

Long-term phosphorus addition alters plant community composition but not ecosystem stability of a nitrogen-enriched desert steppe

Under ongoing global change, whether grassland ecosystems can maintain their functions and services depends largely on their stability. However, how ecosystem stability responds to increasing phosphorus (P) inputs under nitrogen (N) loading remains unclear. We conducted a 7-year field experiment to examine the influence of elevated P inputs (ranging from 0 to 16 g P m−2 yr−1) on the temporal stability of aboveground net primary productivity (ANPP) under N addition of 5 g N·m−2·yr−1 in a desert steppe. We found that under N loading, P addition altered plant community composition but did not significantly affect ecosystem stability. Specifically, with the increase in the P addition rate, declines in the relative ANPP of legume could be compensated for by an increase in the relative ANPP of grass and forb species, yet community ANPP and diversity remained unchanged. Notably, the stability and asynchrony of dominant species tended to decrease with increasing P addition, and a significant decrease in legume stability was observed at high P rates (>8 g P m−2 yr−1). Moreover, P addition indirectly affected ecosystem stability by multiple pathways (e.g., species diversity, species asynchrony, dominant species asynchrony, and dominant species stability), as revealed by structural equation modeling results. Our results suggest that multiple mechanisms work concurrently in stabilizing the ecosystem stability of desert steppes and that increasing P inputs may not alter desert steppe ecosystem stability under future N-enriched scenarios. Our results will help improve the accuracy of vegetation dynamics assessments in arid ecosystems under future global change.

Nitrogen addition and fungal symbiosis alter early dune plant succession.

Anthropogenic nitrogen (N) enrichment can have complex effects on plant communities. In low-nutrient, primary successional systems such as sand dunes, N enrichment may alter the trajectory of plant community assembly or the dominance of foundational, ecosystem-engineering plants. Predicting the consequences of N enrichment may be complicated by plant interactions with microbial symbionts because increases in a limiting resource, such as N, could alter the costs and benefits of symbiosis. To evaluate the direct and interactive effects of microbial symbiosis and N addition on plant succession, we established a long-term field experiment in Michigan, USA, manipulating the presence of the symbiotic fungal endophyte Epichloë amarillans in Ammophila breviligulata, a dominant ecosystem-engineering dune grass species. From 2016 to 2020, we implemented N fertilization treatments (control, low, high) in a subset of the long-term experiment. N addition suppressed the accumulation of plant diversity over time mainly by reducing species richness of colonizing plants. However, this suppression occurred only when the endophyte was present in Ammophila. Although Epichloë enhanced Ammophila tiller density over time, N addition did not strongly interact with Epichloë symbiosis to influence vegetative growth of Ammophila. Instead, N addition directly altered plant community composition by increasing the abundance of efficient colonizers, especially C4 grasses. In conclusion, hidden microbial symbionts can alter the consequences of N enrichment on plant primary succession.

Multiple global change drivers show independent, not interactive effects: a long-term case study in tallgrass prairie.

Ecosystems are faced with an onslaught of co-occurring global change drivers. While frequently studied independently, the effects of multiple global change drivers have the potential to be additive, antagonistic, or synergistic. Global warming, for example, may intensify the effects of more variable precipitation regimes with warmer temperatures increasing evapotranspiration and thereby amplifying the effect of already dry soils. Here, we present the long-term effects (11 years) of altered precipitation patterns (increased intra-annual variability in the growing season) and warming (1°Cyear-round) on plant community composition and aboveground net primary productivity (ANPP), a key measure of ecosystem functioning in mesic tallgrass prairie. Based on past results, we expected that increased precipitation variability and warming would have additive effects on both community composition and ANPP. Increased precipitation variability altered plant community composition and increased richness, with no effect on ANPP. In contrast, warming decreased ANPP via reduction in grass stems and biomass but had no effect on the plant community. Contrary to expectations, across all measured variables, precipitation and warming treatments had no interactive effects. While treatment interactions did not occur, each treatment did individually impact a different component of the ecosystem (i.e., community vs. function). Thus, different aspects of the ecosystem may be sensitive to different global change drivers in mesic grassland ecosystems.

Effects of simulated precipitation changes on plant community characteristics of wetland in the Yellow River Delta, China

Under the changing climate scenario, changes in precipitation regimes are expected to alter soil water and salinity conditions, with consequences on the characteristics of plant community in estuarine wetland. Here, we used a six-year (2015-2020) precipitation manipulation experiment to examine how plant community characteristics responded to precipitation changes in the Yellow River Delta. The results showed that soil electrical conductivity significantly decreased, while soil moisture significantly increased with increasing precipitation. Precipitation changes altered plant community composition. Increased precipitation reduced the absolute dominance of Suaeda glauca and Suaeda salsa, but increased that of Triarrhena sacchariflora and Imperata cylindrica. Shannon index and Margalef richness index of plant community significantly increased with increasing precipitation. Compared with the control, both decreased and increased precipitation decreased the plant community abundance, frequency and coverage. The treatment of 60% increased precipitation significantly decreased plant community frequency by 54.9%, while the 60% decreased precipitation, 40% decreased precipitation, 40% increased precipitation and 60% increased precipitation treatment significantly decreased plant abundance by 38.9%, 33.8%, 35.8% and 45.7%, respectively. The aboveground biomass significantly increased with increasing precipitation, but aboveground plant biomass under 60% increased precipitation treatment being lower than that reducing under 40% increased precipitation treatment, probably due to the negative effects of flooding stress. In addition, Margalef richness index had a significantly positive relationship with aboveground biomass. Aboveground biomass, Shannon diversity index, Margalef richness index, and Simpson diversity index were negatively related to soil electrical conductivity, and aboveground plant biomass was positively related to soil moisture. Our results revealed that precipitation changes regulate growth characteristics, species composition, and diversity of plant community by altering soil water and salinity conditions in a coastal wetland.

Role of soil biotic and abiotic properties in plant community composition in response to nitrogen addition

AbstractNutrient addition can alter plant–soil‐microbe interactions. However, knowledge remains limited about how the soil biotic and abiotic properties drive changes in plant community composition and diversity after nitrogen (N) addition. In this study, four N addition rates (N0, N3, N6, and N9: 0, 3, 6, and 9 g N m −2 yr−1) were applied to a grassland community on the Loess Plateau (China) to evaluate the response of plant community biomass, evenness, and composition to N addition. Overall, N addition significantly increased plant shoot and root biomass by 27.75%–31.37% and 39.60%–65.42% compared with N0, but no significant difference was observed among N3, N6, and N9. N addition significantly decreased shoot/root biomass ratio by 7.17%–21.84%, and plant community evenness by 3.80%–8.80% compared with N0, particularly under N3 and N6 treatments. Furthermore, N addition enhanced the abundance of bacteria and fungi, but their composition was not altered. Responses of plant biomass and evenness to N addition were correlated to changes in NO3−‐N, soil total phosphorus, and the abundance of bacteria and fungi; additionally, the composition was primarily affected by the microbial abundance. Our research indicates that N addition can significantly alter plant community composition, particularly at low addition rates, and such alteration may be more affected by the soil microbial abundance. The findings of this study have important implications for the sustainable management of grassland ecosystems.

Grassland management strategies influence soil C, N, and P sequestration through shifting plant community composition in a semi-arid grasslands of northern China

Current studies regarding the effects of grassland management strategies on the soil nutrient cycle have mostly focused on soil organic carbon (SOC). Less is known about the responses of SOC, total nitrogen (TN), and total phosphorous (TP) stocks to grassland management strategies at different soil depths. We therefore quantified vertical variations in SOC, TN, and TP stocks as well as controlling factors under three grassland management strategies (i.e., enclosure control, grazing twice a year, grazing combined with mowing) in 2014 and 2017 in a semi-arid grassland of northern China. We found that grazing twice a year and grazing combined with mowing led to an increase in plant production as well as soil C and N sequestration during 2014 to 2017. Changes in plant aboveground biomass (AGB), belowground biomass (BGB), and root-to-shoot ratio (R:S) all exerted significant positive effects on changes in soil C and N sequestration in the surface soil layer (0–30 cm), while changes in AGB and plant community composition played a more important role in mediating soil C, N, and P sequestration in response to grassland management strategies in the subsoil layer (30–100 cm). Specifically, grassland management strategies influence soil C, N, and P sequestration capacity by altering plant community composition. The results of this study provide new insights into the response mechanisms of plants and soils to grassland management practices and offer a range of new possible strategies that might be applied to the effective management of semi-arid grasslands.

When Water Availability Is Low, Two Mediterranean Salvia Species Rely on Root Hydraulics.

Increase in severity and frequency of drought events is altering plant community composition, exposing biomes to a higher risk of biodiversity losses. This is exacerbated in the most fragile areas as Mediterranean biome. Thus, identifying plant traits for forecasting species with a high risk of drought-driven mortality is particularly urgent. In the present study, we investigated the drought resistance strategy of two Mediterranean native species: Salvia ceratophylloides Ard. (Sc) and Salvia officinalis L. (So) by considering the impact of drought-driven water content decline on plant hydraulics. Well-watered samples of Sc displayed higher leaf and stemsaturated water content and lower shoot biomass than So samples, but similar root biomass. In response to drought, Sc showed a conservative water use strategy, as the prompt stomatal closure and leaves shedding suggested. A drought-tolerant mechanism was confirmed in So samples. Nevertheless, Sc and So showed similar drought-driven plant hydraulic conductance (Kplant) recover ability. Root hydraulic traits played a key role to reach this goal. Relative water content as well as loss of cell rehydration capability and membrane damages, especially of stem and root, were good proxies of drought-driven Kplant decline.

Inter‐annual precipitation variability alters the effects of soil resource enrichment and mycorrhizal suppression on plant communities in desert steppe

AbstractQuestionsIn desert steppes, plant community productivity and species composition are primarily co‐limited by soil water and nitrogen availability. However, how the addition of resources and arbuscular mycorrhizal fungi (AMF) interactively influence plant community performance has not been investigated in detail.LocationDesert steppe, China.MethodsWe performed a field study to examine the effects of levels of increased water, nitrogen and AMF suppression on plant communities in two years with contrasting inter‐annual precipitation variability in desert steppe.ResultsWe found that inter‐annual precipitation variability altered plant community composition and their productivity in response to water and nitrogen addition and mycorrhizal suppression. AM fungal suppression had few effects on above‐ground plant productivity, whereas the primary effects of water and nitrogen addition were significant across both years. The addition of water and nitrogen altered plant community composition and productivity primarily by increasing the abundance and biomass of annual species only in the normal year (2019), but decreasing the abundance of perennial grasses regardless of the presence of AM fungi across two years with contrasting precipitation conditions. Moreover, the addition of water alone slightly increased the species richness and Shannon diversity compared with the control.ConclusionsOur findings highlight the importance of inter‐annual precipitation variability rather than that of soil resource enrichment and interactions of plants and AM fungi in plant community composition within the desert steppe.

Forty Years of Increasing Precipitation is Correlated with Loss of Forbs in a Tallgrass Prairie

The effects of climate change on plant communities are already observable in many regions. In the tallgrass region of the Northern Great Plains, plant community composition may have shifted in response to increases in both annual precipitation and temperature. We compared community composition of a tallgrass prairie among three sampling periods (1978–1979, 1998, and 2014), spanning more than three decades, in order to better understand (1) temporal shifts in plant cover and (2) which environmental variables were correlated with these changes. Basal cover of Poa pratensis increased and basal cover of forbs declined over time. The shift from a forb-rich to grass-dominated prairie was positively correlated with higher levels of precipitation and soil moisture. Our study suggests that increased precipitation due to climate change has already altered plant community composition in the Great Plains.

Short-term nitrogen and phosphorus additions rather than mycorrhizal suppression determine plant community composition and productivity in desert steppe

Anthropogenic enrichment of soil nitrogen (N) and phosphorous (P) has dramatically altered ecosystem structures and functions. However, our understanding of the interactions between soil nutrient enrichment and arbuscular mycorrhizal (AM) fungi with plant community performance remains elusive. We examined the impacts of soil N and P enrichment and mycorrhizal suppression on plant community composition and productivity in desert steppe. Our results showed that short-term addition of P alone and combined N and P had stronger influence on plant community composition and productivity, but the addition of N alone had a minimal effect. Individual and combined addition of N and P mainly altered plant community productivity by increasing the biomass of annual forbs, but decreasing that of perennial forbs and C3 grasses, regardless of AM fungi. AM fungal suppression did not alter plant community composition and productivity. Addition of P alone and combined N and P slightly increased plant species richness and diversity. Our findings highlight that the short-term N and P enrichments, rather than the presence of AM fungi, change plant community dynamics in desert steppe.

Permafrost condition determines plant community composition and community-level foliar functional traits in a boreal peatland.

Boreal peatlands are critical ecosystems globally because they house 30%–40% of terrestrial carbon (C), much of which is stored in permafrost soil vulnerable to climate warming‐induced thaw. Permafrost thaw leads to thickening of the active (seasonally thawed) layer and alters nutrient and light availability. These physical changes may influence community‐level plant functional traits through intraspecific trait variation and/or species turnover. As permafrost thaw is expected to cause an efflux of carbon dioxide (CO2) and methane (CH4) from the soil to the atmosphere, it is important to understand thaw‐induced changes in plant community productivity to evaluate whether these changes may offset some of the anticipated increases in C emissions. To this end, we collected vascular plant community composition and foliar functional trait data along gradients in aboveground tree biomass and active layer thickness (ALT) in a rapidly thawing boreal peatland, with the expectation that changes in above‐ and belowground conditions are indicative of altered resource availability. We aimed to determine whether community‐level traits vary across these gradients, and whether these changes are dominated by intraspecific trait variation, species turnover, or both. Our results highlight that variability in community‐level traits was largely attributable to species turnover and that both community composition and traits were predominantly driven by ALT. Specifically, thicker active layers associated with permafrost‐free peatlands (i.e., bogs and fens) shifted community composition from slower‐growing evergreen shrubs to faster‐growing graminoids and forbs with a corresponding shift toward more productive trait values. The results from this rapidly thawing peatland suggest that continued warming‐induced permafrost thaw and thermokarst development alter plant community composition and community‐level traits and thus ecosystem productivity. Increased productivity may help to mitigate anticipated CO2 efflux from thawing permafrost, at least in the short term, though this response may be swamped by increase CH4 release.

Plant diversity and litter accumulation mediate the loss of foliar endophyte fungal richness following nutrient addition.

Foliar fungal endophytes are ubiquitous plant symbionts that can affect plant growth and reproduction via their roles in pathogen and stress tolerance, as well as plant hormonal signaling. Despite their importance, we have a limited understanding of how foliar fungal endophytes respond to varying environmental conditions such as nutrient inputs. The responses of foliar fungal endophyte communities to increased nutrient deposition may be mediated by the simultaneous effects on within-host competition as well as the indirect impacts of altered host population size, plant productivity, and plant community diversity and composition. Here, we leveraged a 7-yr experiment manipulating nitrogen, phosphorus, potassium, and micronutrients to investigate how nutrient-induced changes to plant diversity, plant productivity, and plant community composition relate to changes in foliar fungal endophyte diversity and richness in a focal native grass host, Andropogon gerardii. We found limited evidence of direct effects of nutrients on endophyte diversity. Instead, the effects of nutrients on endophyte diversity appeared to be mediated by accumulation of plant litter and plant diversity loss. Specifically, nitrogen addition is associated with a 40% decrease in plant diversity and an 11% decrease in endophyte richness. Although nitrogen, phosphorus, and potassium addition increased aboveground live biomass and decreased relative Andropogon cover, endophyte diversity did not covary with live plant biomass or Andropogon cover. Our results suggest that fungal endophyte diversity within this focal host is determined in part by the diversity of the surrounding plant community and its potential impact on immigrant propagules and dispersal dynamics. Our results suggest that elemental nutrients reduce endophyte diversity indirectly via impacts on the local plant community, not direct response to nutrient addition. Thus, the effects of global change drivers, such as nutrient deposition, on characteristics of host populations and the diversity of their local communities are important for predicting the response of symbiont communities in a changing global environment.

Arbuscular mycorrhizal fungi promote plant growth of Leymus chinensis (Trin.) Tzvelev by increasing the metabolomics activity under nitrogen addition

AbstractNitrogen (N) deposition has been influencing ecological process, for instance N addition can affect plant growth and then alter plant community composition. Arbuscular mycorrhizal fungi (AMF) is one of the important soil microbiota, which play a key role in plant growth, especially under harsh environmental conditions. However, the effects of AMF on plant growth under N addition are still not well understood. To investigate the mechanism how AMF affect plant growth under N addition, a microcosm experiment was conducted with four N addition levels. The results showed that AMF increased aboveground biomass of Leymus chinensis by 21.5% and 4.8% under with and without N addition, respectively. AMF expressively improved the net photosynthetic rate by 44% and 29%, soluble protein by 65% and 40% under with and without N additions, respectively. The chlorophyll a, chlorophyll b, chlorophyll a + b and carotenoids content in leaves treated by AMF were greater than those without AMF treatment. AMF also significantly increased the metabolomics enzymes glutamate dehydrogenase, glutamine oxoglutarate aminotransferase, alanine transaminase and nitrogen reductase activity under N addition. However, the level of glutamine synthetase and soluble carbohydrates increased significantly under N addition in non‐inoculated AMF plants. The result showed that the response of AMF to L. chinensis was stronger than nitrogen deposition, which indicates that AMF could increase plant growth by improving photosynthetic characters and affecting metabolomics enzymes of L. chinensis under N addition.

Simulated climate warming increases plant community heterogeneity in two types of boreal peatlands in north–central Canada

AbstractQuestionsClimate warming has been demonstrated to shift peatland plant community composition from Sphagnum mosses to vascular plants in Sphagnum‐dominated peatlands. However, fewer studies have determined how increasing temperature affects vegetation patterns in Carex‐dominated peatlands. As plants are important determinants of carbon storage potential in peatlands, we aim to determine how climate warming alters plant community composition in peatlands of two different vegetation types.LocationBoreal peatlands in north–central Ontario, Canada.MethodsIn a Sphagnum‐ and a Carex‐dominated peatland over two growing seasons, we instigated passive warming using clear open‐topped chambers, providing a modest increase (1–2°C) in temperature. In replicated plots we examined shifts in plant community composition using the point intercept method, and total above‐ground biomass using Leaf Area Index (LAI) against non‐warmed control plots.ResultsWhile there was no difference in species diversity between control and warmed plots in either fen site, warming significantly increased above‐ground biomass in the Carex‐dominated fen and decreased moss abundance in the Sphagnum‐dominated fen. Both fens also displayed significantly different plant community composition between warming and control plots, and increased heterogeneity under warming.ConclusionPeatlands are important global carbon stores and the plant community contributes to their carbon storage; Sphagnum mosses, in particular, are linked to high peatland carbon storage potential. Previous studies in Sphagnum‐dominated peatlands have shown concomitant declines in Sphagnum biomass and increases in vascular plant biomass, and in the short term, we show only a decline in Sphagnum. At both sites the increase in plant community heterogeneity suggests that climate warming effects on plant community composition in boreal peatlands may be more unpredictable than the literature suggests. Furthermore, this study demonstrates that plant community shifts occur even under modest warming scenarios.