Complex Plant Communities Research Articles

Implication of community-level ecophysiological parameterization to modelling ecosystem productivity: a case study across nine contrasting forest sites in eastern China

Parameterization is a critical step in modelling ecosystem dynamics. However, assigning parameter values can be a technical challenge for structurally complex natural plant communities; uncertainties in model simulations often arise from inappropriate model parameterization. Here we compared five methods for defining community-level specific leaf area (SLA) and leaf C:N across nine contrasting forest sites along the North–South Transect of Eastern China, including biomass-weighted average for the entire plant community (AP_BW) and four simplified selective sampling (biomass-weighted average over five dominant tree species [5DT_BW], basal area weighted average over five dominant tree species [5DT_AW], biomass-weighted average over all tree species [AT_BW] and basal area weighted average over all tree species [AT_AW]). We found that the default values for SLA and leaf C:N embedded in the Biome-BGC v4.2 were higher than the five computational methods produced across the nine sites, with deviations ranging from 28.0 to 73.3%. In addition, there were only slight deviations (< 10%) between the whole plant community sampling (AP_BW) predicted NPP and the four simplified selective sampling methods, and no significant difference between the predictions of AT_BW and AP_BW except the Shennongjia site. The findings in this study highlights the critical importance of computational strategies for community-level parameterization in ecosystem process modelling, and will support the choice of parameterization methods.

Effects of long‐term mowing on leaf‐ and root‐associated bacterial community structures are linked to functional traits in 11 plant species from a temperate steppe

Abstract Long‐term mowing can cause morphological stuntedness of plants, thus reducing grassland productivity and exacerbating grassland degradation. Although plant microbiomes can enhance plant resistance against disturbance, considerable uncertainty exists regarding how mowing and mowing‐induced plant trait plasticity affect plant microbiomes in natural grasslands. Here we examined the responses of leaf/root‐associated bacterial (LAB/RAB) communities of 11 dominant herbaceous perennials (six replicates per species) to a 17‐year mowing treatment in a temperate grassland. We also measured leaf/root physiological and morphological traits, and analysed the relationships among mowing practice, bacterial community structures and leaf/root trait parameters. We found that both leaf and root functional traits showed interspecific variations (variations across different plant species), while only the leaf traits exhibited intraspecific variation (treatment‐induced variations within plant species) between the treatments. Similarly, the LAB community structure was more sensitive to mowing but less influenced by host species identity, compared to the RAB community. The RAB community structure was primarily shaped by host species identity, while mowing was a secondary influencing factor. The different patterns of LAB and RAB communities in response to mowing could be specifically explained by the inter/intraspecific variations of the related leaf and root traits. The LAB community was strongly correlated with the leaf traits which exhibited mowing‐induced plasticity (intraspecific variation), with the correlations with nitrogen resorption efficiency and above‐ground dry weight being the greatest. The root traits were important indicators of bacterial community structure in the root compartment across the hosts, rather than between the treatments. Root tissue density showed the strongest interspecific variation, and was identified as an overwhelming driver of the RAB community. The shifts in LAB/RAB communities under mowing were largely attributed to the increased proportions of Actinobacteria. The high mowing sensitivity of the LAB community was associated with the enrichment of soil‐derived Actinobacteria in leaves under mowing. Actinobacteria were also the main keystone taxa in the bacterial community networks under mowing. Our results demonstrate that the magnitude of plant‐associated microbial community response to long‐term mowing is plant compartment and trait variation dependent, and advance our understanding of the leaf/root microbiome‐trait relationships in complex plant communities. Read the free Plain Language Summary for this article on the Journal blog.

Influence of Agricultural Expansion and Human Disturbance on the Encounter Rates of Nocturnal Mammals in Tropical Hill Forests in Bangladesh

Agricultural expansion has had a detrimental effect on tropical forests and the animal communities that depend on them. Agroforestry systems, however, with their more complex tree and plant communities, have been shown to be important habitats for a range of globally threatened species, including nocturnal animals. Here, we present novel data on the encounter rates of seven species of nocturnal mammals in relation to agroforestry systems within four national parks and associated plantations in Bangladesh to examine if encounter rates were influenced by the human population density, presence of plantations, and human access as represented by a Human Influence Index of anthropogenic disturbance. We walked 70.3 km of transects with only semi-natural forest, 26.9 km of transects with semi-natural forest and gardens, and 21.7 km of transects with semi-natural forest and monocultures over 55 nights from 2017–2019. Of the seven species of nocturnal mammals we detected, all were present in Satachari National Park, whereas six occurred in Lawachara National Park, Rajkandi Forest Range, and Rema-Kalenga Wildlife Sanctuary. Within these national parks, three species (Bengal slow loris, large Indian civet, particolored flying squirrel) were more frequently recorded in areas with human disturbance, especially agroforestry plantations. With declining forest cover in Bangladesh, we highlight here the potential of agroforestry systems as emerging important habitats for these species. We encourage long-term studies of these lesser-studied taxa to understand fully the capacity of agroforestry systems in order to support their long-term conservation.

Predicting ecosystem productivity based on plant community traits.

With the rapid accumulation of plant trait data, major opportunities have arisen for the integration of these data into predicting ecosystem primary productivity across a range of spatial extents. Traditionally, traits have been used to explain physiological productivity at cell, organ, or plant scales, but scaling up to the ecosystem scale has remained challenging. Here, we show the need to combine measures of community-level traits and environmental factors to predict ecosystem productivity at landscape or biogeographic scales. We show how theory can extend the production ecology equation to enormous potential for integrating traits into ecological models that estimate productivity-related ecosystem functions across ecological scales and to anticipate the response of terrestrial ecosystems to global change.

Spatial patterns in neighbourhood effects on woody plant selection and bark stripping by deer in a lowland alluvial forest

AbstractQuestionsUngulate herbivory and its impact on one plant species may be driven by other plants in the neighbourhood. Although such neighbourhood effects have long been recognized, there is limited understanding of how spatial variation in these effects relates to local plant density and distances between plants. Our goal was to examine if the density of or distance to conspecific and heterospecific neighbouring woody individuals produces neighbourhood effects on bark stripping by deer, and how these effects differ in spatial scale and type (reduce/increase herbivory).LocationLowland old‐growth forest, Czech Republic.MethodsWoody individuals were assessed for evidence of bark stripping and the level of damage done by deer in a square 4‐ha plot, mapping all woody stems ≥1 cm diameter at breast height. The spatial distribution of stripping was used to examine neighbourhood effects using spatial point pattern methods.ResultsThe density and distance to neighbours and species identity of focal and neighbouring individuals contributed to a large spatial variation in neighbourhood effects (up to distances of 2–30 m from neighbours). Neighbourhood effects arose mainly from the interactions between neighbouring shrub species and all tree species, and interactions between individual species pairs. Neighbourhood effects more often increased than reduced the stripping of focal individuals. The stripping of Ulmus laevis, Acer campestre and Crataegus laevigata increased near conspecifics, while the stripping of all tree species was more likely near Ulmus laevis, Fraxinus angustifolia and shrubs. Heterospecific tree species were less susceptible to stripping near Tilia cordata and especially Carpinus betulus.ConclusionOur study provides new insight into neighbourhood effects by showing how and at which spatial scales woody plant interactions modify deer herbivory. We advocate considering the life stage and relevant plant traits with multivariate spatial methods in order to elucidate the role of neighbourhood effects in complex plant communities.

Nematode community diversity and function across an alpine landscape undergoing plant colonization of previously unvegetated soils

Climate warming is a key factor driving species range shifts. While previous work has focused on shifts of aboveground plant communities, changes in climate and vegetation should affect soil communities and hence ecosystem-level nutrient cycling and ecosystem functioning. High alpine ecosystems are particularly sensitive to climate warming because snow is among the main drivers of ecosystem structure and function. Climate-warming snow cover changes at Niwot Ridge in the Colorado Rocky Mountains have resulted in a consistent plant colonization of previously unvegetated soils generating a natural gradient of soil habitats ranging from unvegetated to increasingly vegetated. We used this gradient of plant communities at different successional stages to determine if nematodes respond to climate-driven changes in this high-alpine landscape and if they play a role in changes in soil C and N. We hypothesized that: 1) there would be clear shifts in nematode communities along the gradient as a function of snow cover, plant richness and density, and water holding capacity but that these shifts would be dependent on nematode feeding habits and their positioning in the soil foodweb and 2) the shifts would be associated with accumulating soil C and N. To test these hypotheses, we measured nematodes, plants, and soil microbes, snow cover, pH, soil water holding capacity, and different forms of soil C and N in 98 plots across the plant successional gradient. As predicted, nematode communities exhibited extensive shifts from a few individuals of a single species in unvegetated soils to hundreds of individuals and tens of species within every feeding group under complex plant communities. Representatives of omnivorous and bacterivorous K-strategists preceded plants and plant parasites and root associates depended on plants most. Linear regression models indicated that plants, microbial communities and soil water holding capacity, but not snow cover, were the most predictive factors of nematode diversity and density across all trophic levels and that all nematode groups were positively related to all measures of soil C and N. Structural equation models confirmed these results, but also indicated that effects of climate warming on nematodes were indirect primarily through shifts in plant and microbial communities and changes of soil water holding capacity. Moreover, nematode trophic group densities, but not their diversity, played a potential role in the accumulation of soil N, and to a lesser degree of soil C. Because nematode communities at Niwot Ridge are largely at their early phases of assembly, with continuing climate warming, we predict their increasing abundance and diversity will likely continue, as will their impact on soil C and N processes.

Intraspecific plant interaction affects arbuscular mycorrhizal fungal species richness

It is well established that mycorrhizal symbiosis can affect plant-plant interactions. On the other hand, how intraspecific plant interactions influence communities of arbuscular mycorrhizal fungi (AMF) is still very poorly understood. We applied 454 pyrosequencing to determine the responses of AMF communities to intraspecific shoot and root interactions using Medicago sativa L. as host plant. We found that intraspecific plant interaction caused significant variation in the structure of the AMF community assessed from roots but not from soil. Intraspecific root system interaction resulted in significantly elevated AMF species richness, greater total mycorrhizal and arbuscular colonization, and a larger root:shoot ratio compared to plants experiencing intraspecific shoot interaction or no interaction. Intraspecific shoot interaction resulted in significantly depressed AMF species richness. Our results support two hypotheses. The first is that increased AMF species richness in plants experiencing intraspecific root interaction originates from competitive release provided by high root density. The second is that shoot interaction leads to reduced allocation to root systems, increasing the stringency with which host plants selectively reward the most cooperative fungi. Because intraspecific interactions among host plants can influence the structure of their AMF community, interactions among species in complex plant communities may influence AMF community structure in addition to a plant diversity effect.

Evaluation of the winter landscape of the plant community of urban park green spaces based on the scenic beauty esitimation method in Yangzhou, China.

Plant landscapes are fundamental components of the green space of urban parks and are often dynamic, changing throughout the year. Winter is a season with poor plant landscape effects in urban park green spaces. However, plant community landscapes in the winter in urban park green spaces could be further optimized. Here, we conducted scenic beauty estimation (SBE) of the landscape factors in 29 winter plant communities in four typical urban parks in Yangzhou, China using partial correlation analysis and multiple linear regression. The standard SBE values of the 29 plant communities ranged from -0.981 to 1.209. Complex plant community landscapes with abundant plant species, beautiful plant community morphology and obvious seasonal changes generally received high scenic beauty scores. Six landscape factors, including the diversity of plant species, the proportion of evergreen tree species, the morphological characteristics of plants, the ground cover rate, the overall sense of harmony and the color composition, greatly influenced the scenic beauty of the plant landscape in the winter. Generally, the results of this study provide insight into how the plant community landscape in urban parks could be improved.

Biochar alters nitrogen and phosphorus dynamics in a western rangeland ecosystem

Application of biochar to soils has been proposed as a novel approach to managing wood residuals, enhancing soil carbon (C) storage and improving soil fertility; however, the majority of biochar studies have been conducted in agricultural systems that rely on tillage and nutrient inputs associated with annual cropping schemes. Few studies have evaluated the influence of biochar on soil processes in semi-natural rangeland ecosystems that feature more complex plant communities, lack deep soil disturbance, and have relatively few external nutrient inputs. In August 2018, biochar produced using wood waste from a lumber mill in Columbia Falls, MT, USA was applied to surface soils in replicated plots at an experimental ranch in western Montana to test the impact of biochar on soil C storage and nutrient management. A series of soil biochemical properties including total soil C and nitrogen (N), microbial N functional genes, available phosphorus (P) and the net accumulation of nutrients below surface soil layer were evaluated over a one-year period following biochar addition with or without a poultry litter based organic fertilizer. Biochar used alone slightly reduced soil NH4+, significantly increased soil nitrification potential, increased the relative abundance of the bacterial amoA gene, and increased the soil nitrate (NO3−) pool size, while having no net effect on soil inorganic N accumulation below surface soil. By contrast, biochar charged with poultry litter (termed “charged biochar”) had no effect on NH4+ availability, but had a positive effect on amoA abundance. Charged biochar significantly reduced NH4+ accumulation below 25 cm depth compared to poultry litter alone. Biochar additions led to a shift towards a more fungal dominated community and a general increase in P availability. However, biochar alone also contributed to a greater amount of soluble P collected below surface soil, an effect slightly attenuated when biochar was applied with poultry litter. Soil pH increased from 5.7 to 6.9 in response to biochar addition and was one of the dominant factors governing the observed changes in soil processes. Charged biochar helped retain soil nutrients and promoted soil C storage in this semi-natural rangeland system over one growing season. Changes in these soil pools and fluxes may influence various trophic groups affecting ecosystem functioning over time.

Recognizing the role of plant species composition in the modification of soil nutrients and water in rubber agroforestry systems

Reliable guidance for crop selection and related management to achieve sustainable soil resource use in rubber agroforestry systems is limited. One important reason for this limited guidance is that our understanding of the effects of different plant functional groups on soil resources is still insufficient. Here, to examine the effects of the species composition of trees, shrubs and herbs on soil nutrients and soil water with increases in the complexity of the plant community structure, we measured the soil nutrient concentrations (i.e., C, N, P, K, Ca and Mg), soil water content and soil water residence time (with stable hydrogen and oxygen isotope tracers) at six soil depths in a monoculture rubber plantation, four multi-species rubber agroforestry systems, and a tropical rainforest. As the plant species composition increased, the soil C and N increased. The soil water content also increased with increases in soil C and N. However, the effects of plant species composition on the soil water content gradually changed from positive to negative, especially under the effects of herb species, which could accelerate soil water drainage and hence shorten the soil water residence time. Therefore, the faster water infiltration and potentially higher flow of soil water in complex plant communities increased the risk and magnitude of mineral nutrient leaching. In addition, as the plant composition increased, plant competition decreased the concentration of soil nutrients, especially soil P, K and Ca. In general, plant interspecific interactions definitively decreased soil mineral nutrients as the plant composition increased, and the effects of tree, shrub and herb species on soil nutrients and soil water differed and sometimes appeared contradictory. However, the effects of plant species composition on soil gradually weakened with increases in soil depth.

Plant–microbial interactions facilitate grassland species coexistence at the community level

Interspecific competition and plant–soil feedbacks are powerful drivers of plant community structure. However, across a range of edaphic conditions the interactive effects of these drivers on complex plant communities remain unclear. For example, plant–soil feedback studies focus on soil trained by a single plant species. We developed a method to assess effects of plant–microbial interactions (PMI) on a complex plant community. We established mesocosms with 13 grassland species, grown individually or together, in overgrazed or restored soil, with or without soil microbial inoculum collected from a productive and diverse native grassland. We assessed biomass production as influenced by edaphic conditions, interspecific competition and PMI. Furthermore, we assessed potential influences of interspecific competition and edaphic conditions on strength and direction of PMI. Our results indicate PMI drives negative growth responses for graminoids while forbs experience positive growth responses. Generally, interspecific competition did not alter the magnitude or direction of PMI‐mediated growth responses. Edaphic conditions altered the influence of soil microbial communities on individual plant growth while PMI facilitated plant evenness. In plant community mesocosms, PMI‐associated benefits were observed in overgrazed soil. However, interspecific competition overwhelmed plant growth benefits associated with soil microbial communities when plant communities were grown in restored soil. In mesocosms containing dominant grass species, interspecific competition had negative effects on species coexistence, but both positive and negative PMI partially counterbalanced this influence on plant species evenness. Understanding these mechanisms may improve our capacity to manage diverse and productive grasslands by enabling prediction of plant community composition following disturbance and subsequent restoration.

Cultivar Differences and Impact of Plant-Plant Competition on Temporal Patterns of Nitrogen and Biomass Accumulation.

Current niche models cannot explain multi-species plant coexistence in complex ecosystems. One overlooked explanatory factor is within-growing season temporal dynamism of resource capture by plants. However, the timing and rate of resource capture are themselves likely to be mediated by plant-plant competition. This study used Barley (Hordeum sp.) as a model species to examine the impacts of intra-specific competition, specifically inter- and intra-cultivar competition on the temporal dynamics of resource capture. Nitrogen and biomass accumulation of an early and late cultivar grown in isolation, inter- or intra- cultivar competition were investigated using sequential harvests. We did not find changes in the temporal dynamics of biomass accumulation in response to competition. However, peak nitrogen accumulation rate was significantly delayed for the late cultivar by 14.5 days and advanced in the early cultivar by 0.5 days when in intra-cultivar competition; there were no significant changes when in inter-cultivar competition. This may suggest a form of kin recognition as the target plants appeared to identify their neighbors and only responded temporally to intra-cultivar competition. The Relative Intensity Index found competition occurred in both the intra- and inter- cultivar mixtures, but a positive Land Equivalence Ratio value indicated complementarity in the inter-cultivar mixtures compared to intra-cultivar mixtures. The reason for this is unclear but may be due to the timing of the final harvest and may not be representative of the relationship between the competing plants. This study demonstrates neighbor-identity-specific changes in temporal dynamism in nutrient uptake. This contributes to our fundamental understanding of plant nutrient dynamics and plant-plant competition whilst having relevance to sustainable agriculture. Improved understanding of within-growing season temporal dynamism would also improve our understanding of coexistence in complex plant communities.

Below‐ground plant traits influence tundra plant acquisition of newly thawed permafrost nitrogen

Abstract The release of permafrost‐derived nitrogen (N) has the potential to fertilize tundra vegetation, which in turn may stimulate productivity and thus offset carbon (C) losses from thawing permafrost. Below‐ground plant traits may mediate ecosystem response to permafrost thaw and associated feedbacks to the atmosphere by differentially conferring access to deep, newly thawed permafrost N. Yet, identifying roots and quantifying root N uptake from deep, cold soils in complex plant communities has proved challenging to date. We investigated plant acquisition of experimentally added 15N isotope tracer applied at the permafrost boundary in graminoid‐ and shrub‐dominated tundra at Eight Mile Lake, Alaska, when the thaw front was close to its maximum depth, simulating the release of newly thawed permafrost N. We used molecular tools to verify species and estimate biomass, nitrogen, and isotope pools. Root biomass depth distributions follow an asymptotic relationship with depth, typical of other ecosystems. Few species had roots occurring close to the thaw front. Rubus chamaemorus, a short‐statured non‐mycorrhizal forb, and Carex bigelowii, a sedge, consistently had the deepest roots. Twenty‐four hours after isotope addition, we observed that deep‐rooted, non‐mycorrhizal species had the highest 15N enrichment values in their fine root tissue indicating that they access deep N late in the growing season when the thaw front is deepest. Deep‐rooted plants are therefore able to immediately take up newly thawed permafrost‐derived N. During the following growing season, herbaceous, non‐mycorrhizal plants allocated tracer above‐ground before woody, mycorrhizal plants. Ectomycorrhizal deciduous and ericoid mycorrhizal evergreen shrubs, by contrast, did not have immediate access to the deep N tracer and assimilated it into new foliar tissue gradually over the following growing season. Synthesis. Graminoids and forbs that have immediate access to deep N represent a modest C sink compared to C emissions from thawing permafrost. However, the effects of deep N fertilization on shrubs over longer time‐scales may stimulate productivity and account for a more considerable N and C sink, thus constraining the permafrost C‐climate feedback.

Tree species could have substantial consequences on topsoil fauna: a feedback of land degradation/restoration

The characteristics of the faunal community in the soil are closely related to soil quality and function. Land degradation, which reduces vegetation cover, may affect the soil surface-active fauna because both the above ground and below ground invertebrates depend on complex plant communities. In this study, we evaluated the effect of land degradation/restoration and factors affecting soil fauna in northern Iran. The studied land uses were virgin natural forest (VNF), Alnus subcordata C.A.M. plantation (ASP), Quercus castaneifolia C.A. Mey plantation (QCP), Cupressus sempervirens var. horizontalis plantation (CSP) and degraded natural forest (DNF). VNF and ASP enhanced soil earthworm density (2.43 and 2.12 ind. m−2) and dry mass (27.44 and 23.39 mg m−2) with more ratio of epigeic. The activities of acarina (91,851.37 and 85,810.43 ind. m−2), collembola (83,009.50 and 74,996.18 ind. m−2) and protozoa [921.25 and 851.81 (× 102 g soil)] were increased under VNF ≈ ASP, respectively. Nematode population (650 in 100 g soil) significantly improved under VNF. In general, good quality forest floor, alkaline soil and accumulation of macro-element nutrients improved biological activities under the VNF and ASP sites, while low-quality forest floor, acidic soil, less macro-elements nutrients decreased biological activities imposed by the QCP, CSP and DNF sites. More activities of the studied soil fauna were found in autumn and spring. The findings of this study support the importance of preserving natural forests. In addition, employing N2-fixing and suitable native broadleaved species have been proposed in a bid to rehabilitate DNFs.

Computational botany: advancing plant science through functional–structural plant modelling

The need to integrate the ever-expanding body of knowledge in the plant sciences has led to the development of sophisticated modelling approaches. This special issue focuses on functional-structural plant (FSP) models, which are the result of cross-fertilization between the domains of plant science, computer science and mathematics. FSP models simulate growth and morphology of individual plants that interact with their environment, from which complex plant community properties emerge. FSP models can be used for a broad range of research questions across disciplines related to plant science. This special issue presents the latest developments in FSP modelling, including the novel incorporation of plant ecophysiological concepts and the application of FSP models to address new scientific questions. Additionally, it illustrates the breadth of model evaluation approaches that are performed. FSP modelling is a very active domain of plant research which brings together a wide range of scientific disciplines. It offers the opportunity to address questions in complex plant systems that cannot be addressed by empirical approaches alone, including questions on fundamental concepts related to plant development such as regulation of morphogenesis, as well as on applied concepts such as the relationship between crop performance and plant competition for resources.

Host Plant Species Differentiation in a Polyphagous Moth: Olfaction is Enough

Polyphagous herbivorous insects need to discriminate suitable from unsuitable host plants in complex plant communities. While studies on the olfactory system of monophagous herbivores have revealed close adaptations to their host plant’s characteristic volatiles, such adaptive fine-tuning is not possible when a large diversity of plants is suitable. Instead, the available literature on polyphagous herbivore preferences suggests a higher level of plasticity, and a bias towards previously experienced plant species. It is therefore necessary to take into account the diversity of plant odors that polyphagous herbivores encounter in the wild in order to unravel the olfactory basis of their host plant choice behaviour. In this study we show that a polyphagous moth, Spodoptera littoralis, has the sensory ability to distinguish five host plant species using olfaction alone, this being a prerequisite to the ability to make a choice. We have used gas chromatography mass spectrometry (GC-MS) and gas chromatography electroantennographic detection (GC-EAD) in order to describe host plant odor profiles as perceived by S. littoralis. We find that each plant emits specific combinations and proportions of GC-EAD active volatiles, leading to statistically distinct profiles. In addition, at least four of these plants show GC-EAD active compound proportions that are conserved across individual plants, a characteristic that enables insects to act upon previous olfactory experiences during host plant choice. By identifying the volatiles involved in olfactory differentiation of alternative host plants by Spodoptera littoralis, we set the groundwork for deeper investigations of how olfactory perceptions translate into behaviour in polyphagous herbivores.

Complex plant community responses to modifications of disturbance and nutrient availability in productive permanent grasslands

AbstractQuestionDo the effects of grazing and fertilization on taxonomic and functional diversity follow the dynamic equilibrium model?LocationLong‐term permanent upland grasslands, Massif‐central, France.MethodsOver 8 yr, we monitored vegetation changes in 24 experimental plots in two productive grasslands after modification of grazing intensity (including abandonment) or fertilization regime (including cessation of fertilization). Botanical surveys and plant trait measurements (LDMC, SLA and reproductive plant height) were performed within each plot. We analysed taxonomic responses using PRC and functional responses from observed temporal changes of CWM traits and Rao index.ResultsGrazing abandonment led to significant reductions in species richness and functional convergence toward taller plants with higher LDMC in both grasslands. Intermediate and high grazing pressure did not differ but showed strong variations in taxonomic diversity between years. Changes in functional vegetation structure were mostly driven by species turnover and weakly influenced by intraspecific trait variability. Community responses to modified fertilization regime were more complex, with strong differences between the two mown grasslands. Species richness did not change significantly although species evenness decreased in the highly fertilized treatments (NPK), particularly in the most productive grassland. Here, functional changes were largely driven by intraspecific trait variability. Both functional divergence and convergence were found for different traits. In NPK, grassland assemblages converged toward taller plants while SLA diverged.ConclusionsIn our upland study system the different components of grassland diversity responded differently, in terms of direction or rate of change and mostly under extreme modifications of management. Following abandonment, the observed patterns suggest a prominent and consistent role of competitive exclusion, as expected under the DEM. However, our findings also suggest the role of additional processes, especially the importance of niche differentiation, for our mown grassland under NPK. Timing and net effects of these combined assembly drivers were sensitive to even slight differences in initial productivity and species composition.

Native seed for restoration: a discussion of key issues using examples from the flora of southern Australia

Land clearing across southern Australia since European settlement has fundamentally changed the amount and distribution of native vegetation; it has also substantially reduced genetic diversity in plant species throughout Australia, especially in agricultural regions. The most recent State of the Environment report indicates that Australian biodiversity continues to decline. Many approaches to restoration are used in Australia including re-establishing plant populations using tube stock or by direct seeding. Native seed for these projects is often assumed to be plentiful and available for the majority of species we wish to restore but these assumptions are rarely true. We also rely on a small number of species for the majority of restoration projects despite the vast number of species required to fully restore complex plant communities. The majority of seed for restoration is still primarily collected from native vegetation despite longstanding concerns regarding the sustainability of this practice and the globally recognised impacts of vegetation fragmentation on seed production and genetic diversity. Climate change is also expected to challenge seed production as temperatures rise and water availability becomes more limited; changes to current planting practices may also be required. Until now native seed collection has relied on market forces to build a strong and efficient industry sector, but in reality the Australian native seed market is primarily driven by Federal, State and Territory funding. In addition, unlike other seed-based agri-businesses native seed collection lacks national industry standards. A new approach is required to support development of the native seed collection and use sector into an innovative industry.

Prefire grazing by cattle increases postfire resistance to exotic annual grass (Bromus tectorum) invasion and dominance for decades.

Fire, herbivory and their interaction influence plant community dynamics. However, little is known about the influence of prefire herbivory on postfire plant community response, particularly long‐term resistance to postfire exotic plant invasion in areas that historically experienced limited large herbivore pressure and infrequent, periodic fires.We investigated the long‐term postfire effects of prefire herbivory by cattle, an exotic herbivore, in Artemisia (sagebrush) plant communities in the northern Great Basin, USA. Study areas were moderately grazed or not grazed by cattle since 1936 and then were burned in 1993. Plant community response was measured the 19th through the 22nd year postfire. Prior to burning exotic annual grass presence was minimal (<0.5% foliar cover) and plant community characteristics were similar between grazed and ungrazed treatments, with the exception of litter biomass being two times greater in the ungrazed treatment.Two decades postfire, Bromus tectorum L., an exotic annual grass, dominated the ungrazed treatment. Native bunchgrasses, species richness, and soil biological crusts were greater in prefire grazed areas compared to ungrazed areas.These results suggest that moderate prefire herbivory by cattle increased the resistance of the plant community to postfire invasion and dominance by B. tectorum. We presume that herbivory reduced mortality of large perennial bunchgrasses during the fire by reducing fine fuel (litter) and subsequently burn temperatures. Synthesis: This research demonstrates that a moderate disturbance (herbivory) may mediate the effects of a subsequent disturbance (fire). The effects of disturbances are not independent; therefore quantifying these interactions is critical to preventing oversimplification of complex plant community dynamics and guiding the conservation of endangered ecosystems.

Social and environmental factors drive variation in plant and bird communities across urban greenspace in Sydney, Australia

We examined whether environmental or social factors alone, or a combination of social–ecological factors were more effective at explaining patterns in plant and bird assemblages across urban greenspaces. Thirty publicly accessible, passive recreation greenspaces provided by municipal councils (i.e. city parks) were surveyed in a highly urbanised city – Sydney, Australia. Plant communities were influenced most by topography and park management approach, and to a lesser extent by land-use history. Greenspaces with greater topographic variation and that were co-managed with local citizen groups hosted higher plant species richness and abundance. Bird species richness within greenspaces increased with increasing distance from the central business district and decreasing distance from freshwater. Bird abundance was best explained by a combination of social–ecological factors, with abundance increasing with increasing site (greenspace) age, increasing percent concrete groundcover of a site and increasing proximity to the central business district. We identified a group of ‘rare city parks’, dissimilar in ecological composition that hosted more complex and species rich plant communities compared to ‘common city parks’. We suggest this difference is likely because rare city parks received management and maintenance input from local citizen groups, whereas common city parks were managed and maintained exclusively by local councils. How different social factors, such as management approach and ongoing maintenance, are linked to the ecology of urban greenspaces are key areas for future investigation to help create sustainable urban landscapes that provide maximum benefits to urban residents.