Perennial Species Richness Research Articles

Plant Diversity and Conservation Role of Three Indigenous Agroforestry Systems of Southeastern Rift-Valley Landscapes, Ethiopia

Woody and non-woody plant species conservation is one of the ecosystem services provided by agroforestry (AF) systems across the agricultural landscapes. Little attention has been paid to assessing the conservation of plant diversity in AF systems. This study was, thus, aimed at investigating plant species diversity, structure, and composition of three AF systems in Gedeo zone of south-eastern rift–valley agricultural landscape of Ethiopia. The study was conducted in three agroforestry systems, namely, enset based, coffee–enset based (C–E based AF), and coffee–fruit trees–enset based (C–Ft–E based AF) agroforestry systems. Twenty farms representative of each AF system were randomly selected, and inventory of the floristic diversity was employed in a 10 m × 10 m sample plot per farm. A total of 52 perennial woody and non-woody plant species belonging to 30 families were recorded. Of all species identified, 33 (63.5%) were native, of which two species, namely Millettia ferruginea (Hochst.) Baker and Erythrina brucei Schweinf., were registered as endemic. The highest proportion of native species was recorded in enset based AF (93.3%), and the least were in C–Ft–E based AF (59%). According to the IUCN Red List and local criteria, 13 species were recorded as being of interest for conservation in all AF systems. The woody species Prunus africana was identified as both vulnerable by IUCN Red List and rare for 25% of species that least occur. The Shannon diversity index and richness showed that C–Ft–E based AF systems were significantly different from the two remaining AF systems. However, the species abundance and evenness did not show significant differences between the three AF systems. In general, retaining such numbers of woody and non-woody perennial plant species richness under the AF systems of the present study underlines their potential for biodiversity conservation.

Disturbance legacy of a 100-year flood event: large wood accelerates plant diversity resilience on gravel-bed rivers.

Understanding biodiversity resilience after a major disturbance is a key issue in basic and applied science. Plant diversity in gravel-bed rivers is affected by flood events, which are one of the most effective disturbance agents in the flow regime, affecting species distribution, and ecosystem dynamics. Although disturbance plays a critical role in community assembly mechanisms, how plant diversity recovers after a severe disturbance, such as a 100-year flood event remains unknown. The present study examined how the disturbance legacy of large wood in gravel-bed river ecosystems contributes to the resilience of plant diversity. The present study demonstrated that the resilience of plant species in disturbance legacy sites, namely deposited large wood sites, was higher than that in open habitat sites. Indicator species analysis revealed that perennial plants were the most important indicator species of disturbance legacy sites. These results suggest that perennial species richness contributes to the resilience of high plant diversity across the disturbance legacy sites in this region. After major flood events, land managers often remove large wood and debris jams to avoid secondary disasters, such as embankment collapse. However, we suggest that large wood should be retained on the gravel beds to aid the recovery of biodiversity and ecosystems. Furthermore, understanding the relationships between disturbance legacies and ecosystem resilience can contribute to the formulation of strategies for sustainable ecosystem management and biodiversity conservation in the future.

Vegetation Change in a Sand Prairie over Ten Years Following a Gas Pipeline Installation

Sand prairies experience relatively high rates of small-scale disturbance, feature a high complement of annual plant species, and are fairly dynamic in terms of year-to-year micro-scale species composition. In summer 2011, an underground natural gas pipeline was installed across Sand Prairie Natural History Reservation 19 km west of North Newton, KS. The resulting excavation left a strip 560 m long and 24 m wide devoid of aboveground vegetation. From August 2012 to 2021, I monitored vegetation composition in 60 0.75 × 0.75 m2 quadrats along six parallel transect lines: three lines along the center of the excavated area and three placed 20 m away in prairie unaffected by earth-moving vehicles. Quadrat species richness was higher in the undisturbed reference area in the first year, but higher in the pipeline area in four later years. There were no consistent area differences in species evenness. Annual species richness was higher within the pipeline area every year. In contrast, perennial species richness was higher in the reference area during the first seven years. Coverage by annuals was higher every year within the pipeline area, whereas coverage by perennials was consistently higher in the reference area. Bray-Curtis Similarity for the two areas ranged from 29.2 to 55.8% across years, but was not trending upward with time. Twenty-one species were restricted to the pipeline area; several other species were beginning to move from the reference area to the pipeline area. Both Floristic Quality Index and modified FQI were consistently higher for the reference area than for the pipeline area. It is too early to project the time frame for the pipeline area to recover a species composition indistinguishable from the undisturbed reference site, but clearly a period longer than ten years will be required.

Vegetation, water infiltration, and soil carbon response to Adaptive Multi-Paddock and Conventional grazing in Southeastern USA ranches

We examine Adaptive Multi-Paddock (AMP) grazed with short grazing events and planned recovery periods and paired ranches using Conventional Continuous Grazing (CG) at low stock density on vegetation, water infiltration, and soil carbon across SE USA. Increased vegetation standing biomass and plant species dominance-diversity were measured in AMP grazed ranches. Invasive perennial plant species richness and abundance increased with AMP grazing in the south, while in the north they increased on CG grazed ranches. Percent bare ground was significantly greater in CG at the Alabama and Mississippi sites, no different at the Kentucky and mid-Alabama sites, and greater on AMP at the Tennessee pair. On average, surface water infiltration was higher on AMP than paired CG ranches. Averaged over all locations, soil organic carbon stocks to a depth of 1 m were over 13% greater on AMP than CG ranches, and standing crop biomass was >300% higher on AMP ranches. AMP grazing supported substantially higher livestock stocking levels while providing significant improvements in vegetation, soil carbon, and water infiltration functions. AMP grazing also significantly increased available forage nutrition for key constituents, and increased soil carbon to provide significant resource and economic benefits for improving ecological health, resilience, and durability of the family ranch.

Above- and belowground biomass and biomass carbon stocks in homegarden agroforestry systems of different age groups at three sites of southern and southwestern Ethiopia

As the loss of forests over time results in a net flux of carbon (C) into the atmosphere, the practice of agroforestry can combat this and serve as a long-term sink for CO2. Based on the inventory of 93 homegarden agroforestry systems (AFS) in three study sites and using a non-destructive method involving allometric equations, the research assessed aboveground (AG) and belowground (BG) biomass and biomass C stocks across sites and along age groups in homegarden AFS in southern and southwestern Ethiopia. Plant diversity parameters were also gathered on perennial plant species. Results indicate that the mean perennial plant species richness per homegarden agroforestry, and other diversity parameters varied strongly among sites (p < 0.05). Biomass C stocks range from 18.11 at Malo Ezo to 32.86 Mg C ha−1 at Saja Laften for AG, 3.97 to 7.10 Mg C ha−1 for BG, and 22.02 to 39.96 Mg C ha−1, for each respective sites, for the overall biomass C stocks were recorded within the homegarden agroforestry systems. In terms of age groups, the mean total biomass C stock did show numerical change from the initial, ≤10 years (22.49 Mg C ha−1) to the middle age group, >10 and ≤20 years (39.96 Mg C ha−1), but it was stagnant 20 years onward (28.49 Mg C ha−1). The homegarden agroforestry systems had the potential to store up to 80.81–112.30 Mg·ha−1 of CO2 equivalents across sites, and 82.53–104.55 Mg·ha−1 of CO2 equivalents along age groups. A positive relationship was noted between AG woody biomass C stocks and attributes such as woody species richness, and woody plant density. Considering the involvement of large numbers of homegardeners, future improvements and expansion of homegarden agroforestry to larger areas can enhance to a great extent the potential to sequester C and thereby mitigate climate change.

Impact of climate change on plant species richness across drylands in China: From past to present and into the future

It is commonly believed that climate plays an important role in shaping the patterns of plant species richness. However, it remains unclear how climate may affect plant richness across large spatial scales and also over long-terms, for example across massive arid regions during the Quaternary and into the future. To fill this knowledge gap, we examined the long-term trends in plant species richness across vast drylands in China based on our newly developed climate-species richness models. We first generated optimal random forest models based on the relationships between the current (CUR, 1970–2000) annual, perennial, woody and total species richness and climatic variables. We subsequently hindcasted and forecasted plant species richness in five other periods: last interglacial (LIG, 120,000–140,000 years BP), last glacial maximum (LGM, about 22,000 years BP), mid-Holocene (MH, about 6000 years BP), 2041–2060 (2050), and 2061–2080 (2070). Our results showed that total and herbaceous species richness exhibited similar patterns that were driven by temperature and precipitation. Both groups of species formed a transition zone between arid and semi-arid regions in all periods except LIG. In contrast, woody species richness did not form any transition zone because it was regulated mainly by temperature. Furthermore, the mean richness of herbaceous, woody and all species exhibited gradually increasing trends from LIG to 2070 across drylands in China. On the one hand, herbaceous species were much more sensitive to climate change than woody species. On the other hand, plant species richness in mountain-basin systems and Taklamakan Desert regions were more sensitive to climate change than in meadows and steppes. These results shed new insights into the past and future changes in plant species richness over vast drylands and provide valuable information for future conservation efforts under global warming.

Soil carbon and plant richness relationships differ among grassland types, disturbance history and plant functional groups

Understanding the relationship of soil carbon storage and species diversity in grasslands can provide insights into managing these ecosystems. We studied relationships among soil C and plant species richness within ~ 9700 ha of grasslands in Colorado, US. Using 141 grassland transects, we tested how soil C was related to plant species richness, grassland type, soil texture, and prairie dog presence. Soil C was significantly, positively related to plant species richness, while native perennial graminoid species richness exhibited an even stronger positive relationship. However, the relationship of soil C and plant richness was not found in all three grassland types studied, but instead was unique to the most common grassland type, mixed grass prairie, and absent from both xeric tallgrass and mesic tallgrass prairie. The presence of a single indicator species, Andropogon gerardii, showed a significant, positive relationship with soil carbon. Our best possible model explained 45% of the variance in soil C using species richness, grassland type, and their interaction. Surprisingly, soil C was negatively related to soil clay, suggesting that surface clays amplify evaporation and water runoff rather than protecting soil organic matter from decomposition. Soil C was negatively related to prairie dog presence, suggesting that prairie dogs do not enhance soil carbon sequestration; in fact, prairie dog occupied sites had significantly lower soil C, likely related to loss of topsoil from prairie dog colonies. Our results suggest that management for species richness provides the co-benefit of soil C storage, and high clay and prairie dog disturbance compromises both.

Ecological indicators and bioindicator plant species for biomonitoring industrial pollution: Eco-based environmental assessment

Industrial pollution remains a driving force to ecosystem alteration. Pollutants are released in the atmosphere interacting in turn with other components of earth system such as plant species. Despite the long-term exposition of vegetation cover to pollution is drastically devastating, less is known about the contribution of ecological indicators for its monitoring. The aims of this study are (i) to introduce the ecological indicators in assessing the cement dust impact on plant species and its biomonitoring and (ii) to screen new indicator species for phytoremediation studies. Floristic surveys were conducted in the cement plant closeness following quadrat method. Vegetation indicators such as total plant cover, perennial and annual species densities and diversity were assessed. Bioindicator species were identified using the bioaccumulation factor (BF) and translocation factor (TF). A decrease of perennial species richness and a decline of total vegetation cover by 7 times as well as a diversity decrease ranging from 2.99 to 2.31 were found pertinent indicators of land degradation in the industrial area. Annual species densities were significantly affected by cement pollution. Species like Lygeum spartum, Atractylis serratuloides and Gymnocarpos decander arise as indicators of heavy metals pollution. Pollution in the cement plant vicinity excluded sensitive species like Helianthemum kahiricum, Stipa tenassissima, Plantago coronopus. This study allowed the identification of indicator species of potential use in phytoremediation applications and emphasized the possibility of relaying on the vegetation indicators to assess the impact of cement pollution.

Resilience and alternative stable states after desert wildfires

AbstractImproving models of community change is a fundamental goal in ecology and has renewed importance during global change and increasing human disturbance of the biosphere. Using the Mojave Desert (southwestern United States) as a model system, invaded by nonnative plants and subject to wildfire disturbances, we examined models of resilience, alternative stable states, and convergent‐divergent trajectories for 36 yr of plant community change after 31 wildfires in communities dominated by the native shrubs Larrea tridentata or Coleogyne ramosissima. Perennial species richness on average was fully resilient within 23 yr after disturbance in both community types. Perennial cover was fully resilient within 25 yr in the Larrea community, but recovery was projected to require 52 yr in the Coleogyne community. Species composition shifts were persistent, and in the Coleogyne community, the projected compositional recovery time of 550 yr and increasing resembled a deflected trajectory toward potential alternative states. Disturbed sites contained a perennial species composition of predominately short‐statured forbs, subshrubs, and grasses, contrasting with the larger‐statured shrub and tree structure of undisturbed sites. Auxiliary data sets characterizing species recruitment, annual plants including nonnative grasses, biocrust communities, and soils showed persistent differences between disturbed and undisturbed sites consistent with positive feedbacks potentially contributing to alternative stable states. Resprouting produced limited resilience for the large shrubs L. tridentata and Yucca spp. important to population persistence but did not forestall long‐term reduced abundance of the species. The nonnative annual grass Bromus rubens increased on disturbed sites over time, suggesting persistently abundant nonnative plant fuels and reburn potential. Biocrust cover on disturbed sites was half and species richness a third of amounts on undisturbed sites. Soil nitrogen was 30% greater on disturbed sites and no significant trend was evident for it to decline on even the oldest burns. Disturbed desert plant communities simultaneously supported all three models of resilience, alternative stable states, and convergent‐divergent trajectories among community measures (e.g., species richness, composition), timeframes since disturbance, and spatial resolutions. Accommodating expression within ecosystems of multiple models, including those opposing each other, may help broaden theoretical models of ecosystem change.

Effects of perennial aromatic grass species richness and microbial consortium on soil properties of marginal lands and on biomass production

AbstractThis study investigates the effects of perennial grass species richness levels and consortium of three bacteria on properties of a slightly alkaline soil and on biomass production of grasses. Four species of perennial aromatic grasses namely: vetiver (Vetiveria zizanioides), lemongrass (Cymbopogon citratus), palmarosa (Cymbopogon martinii), and citronella (Cymbopogon winterianus) were planted in all possible combinations at one, two, three, and four species richness levels in a randomized block design with three replications and two treatments, these were PGPR+ (with plant growth promoting rhizobacteria) and without (PGPR−). Species and richness level specific changes in soil physicochemical properties: electrical conductivity (EC); bulk density (BD); total soil organic carbon (TOC); available nitrogen (Nav), microbial colony forming unit (CFU); microbial biomass carbon (MBC), and enzymatic alkaline phosphatase (ALKP) and dehydrogenase activity (DHA) were observed. The highest reduction in soil pH and EC and increase in soil TOC, CFU, Nav, MBC, and enzymes activities were found at two species richness levels of vetiver and lemongrass in both PGPR+ and PGPR− plots followed by monoculture of vetiver. The highest annual total dry biomass 22.8 and 27.5 Mg ha−1 was produced by monoculture of vetiver in PGPR− and PGPR+ plots, respectively, with similar values at two species richness levels of vetiver and lemongrass in PGPR− and PGPR+ plots. The highest plant carbon was found in vetiver monoculture and two species richness levels of vetiver and lemongrass. The soil carbon sequestration potential was highest at two species mixtures of vetiver–lemongrass and lemongrass–palmarosa as well.

The biggest bang for the buck: cost-effective vegetation treatment outcomes across drylands of the western United States.

Restoration and rehabilitation are globally implemented to improve ecosystem condition but often without tracking treatment expenditures relative to ecological outcomes. We evaluated the cost-effectiveness of widely conducted woody plant and herbaceous invasive plant removals and seeding treatments in drylands of the western United States from 2004 to 2018 to determine how land managers can optimize efforts. Woody plant cover decreased at a similar rate per dollar spent regardless of vegetation removal type, and the dominant invasive species was reduced by herbicide application. Relatively inexpensive herbicide application also had a large positive effect on seeded perennial grass cover that was enhanced by additional cost; while expensive woody mastication treatments had little effect regardless of additional cost. High seed cost was driven by including a large proportion of native species in seed mixes, and combined with high seeding cost, promoted a short-term (2-3yr) gain in perennial forb cover and species richness. In contrast, seeding and seed mix cost had no bearing on seeded perennial grass cover, in part, because relatively cheap nonnative seeded species rapidly increased in cover. Our results suggest the differential benefits of commonly implemented treatments aimed at reducing wildfire risk, improving wildlife habitat and forage, and reducing erosion. Given the growing need and cost of restoration and rehabilitation, we raise the importance of specifying treatment budgets and objectives, coupled with effectiveness monitoring, to improve future outcomes.

Perennial plant patches are sinks for seeds in semi‐arid woodlands in varying condition

AbstractQuestionsUnderstanding the processes that influence resilience in semi‐arid woodland communities is of critical importance in landscapes where livestock grazing is the dominant land use and an important driver of site condition. Seed banks are a critical component of site resilience as their persistence can be crucial for recovering from disturbances. We predicted that site condition and landscape structural elements (perennial plant patches) would strongly influence the richness and density of the soil seed bank.LocationNew South Wales, Australia.MethodsWe conducted a seedling emergence study to investigate the germinable seed bank in semi‐arid woodland. Soil samples were collected from three woodland communities (Cypress pine, Black box, Red gum) from sites in three levels of site condition (poor, average, good) and from four patch types (tree, shrub, grass, open). Seed bank species were assigned to three plant trait groups based on: (a) origin; (b) lifespan; and (c) palatability. We used linear models to assess the effects of community, site condition and patch type on the richness and seed density of the germinable seed bank.ResultsSite condition did not affect the seed bank density or richness, except for a lower density of highly palatable species at poor‐condition sites. Across all communities the importance of patch type on the soil seed bank density and richness varied with plant traits. The seed bank of perennial plant patches had a greater density of perennial species, a lower density of low palatability plants, and a greater richness of native and perennial species than interspaces.ConclusionsOur results demonstrate that the germinable soil seed bank in semi‐arid woodlands can be relatively resilient to degradation. This suggests that disturbed sites where perennial patches remain, may still have the ability to recover, because these patches act as important seed reservoirs.

Nitrogen addition decreases seed germination in a temperate steppe.

Seed germination and seedling establishment play an important role in driving the responses of plant community structure and function to global change. Nitrogen (N) deposition is one of the driving factors of global change, which often leads to a loss in species richness in grassland ecosystems. However, how seed germination responds to N addition remains unclear. A pot incubation test was conducted in a semi‐arid grassland in the Mongolian Plateau, Northern China, to investigate the effect of N addition (0, 5, 10, 20, 40, and 80 g N/m2) on seed germination from May to October 2016. Twenty species germinated under all treatments; however, the responses of the 20 species to N addition were different. The densities of Stipa krylovii, Leymus chinensis, and Artemisia frigida, which are the dominant species in this temperate steppe, decreased significantly as the amount of N addition. Moreover, N addition significantly suppressed seedling densities of the community, perennial forbs, perennial grasses, and annuals and biennials. Furthermore, species richness of the community, perennial forbs, and annuals and biennials decreased sharply with increasing N addition level, but perennial grass species richness did not change. The Shannon–Wiener diversity index also decreased as the amount of N addition increased. Our results suggest that N enrichment plays an important role in the seed germination stage and decreases supplements of seedlings to adult plants. These findings may help explain the causes of species loss by atmospheric N deposition in grassland ecosystems.

Effect of indaziflam on native species in natural areas and rangeland

AbstractMinimizing the negative ecological impacts of exotic plant invasions is one goal of land management. Using selective herbicides is one strategy to achieve this goal; however, the unintended consequences of this strategy are not always fully understood. The recently introduced herbicide indaziflam has a mode of action not previously used in non-crop weed management. Thus, there is limited information about the impacts of this active ingredient when applied alone or in combination with other non-crop herbicides. The objective of this research was to evaluate native species tolerance to indaziflam and imazapic applied alone and with other broadleaf herbicides. Replicated field plots were established at two locations in Colorado with a diverse mix of native forbs and grasses. Species richness and abundance were compared between the nontreated control plots and plots where indaziflam and imazapic were applied alone and in combination with picloram and aminocyclopyrachlor. Species richness and abundance did not decrease when indaziflam or imazapic were applied alone; however, species abundance was reduced by treatments containing picloram and aminocyclopyrachlor. Species richness was only impacted at one site 1 yr after treatment (YAT) by these broadleaf herbicides. Decreases in abundance were mainly due to reductions in forbs that resulted in a corresponding increase in grass cover. Our data suggest that indaziflam will control downy brome (Bromus tectorumL.) for multiple years without reduction in perennial species richness or abundance. IfB. tectorumis present with perennial broadleaf weeds requiring the addition of herbicides like picloram or aminocyclopyrachlor, forb abundance could be reduced, and in some cases there could be a temporary reduction in perennial species richness.

Assessing the impact of anthropogenic activities on the ecological quality of arid Mediterranean ecosystems (case study from the northwestern coast of Egypt)

Northwestern coastal desert of Egypt is under pressure of human-induced changes due urban sprawl and agricultural practices leading to negative impacts on existing natural habitats. Assessing the impact of land-use changes on the ecological integrity is crucial for management and conservation efforts in the region. Floristic quality (FQ) assessment indices are important bioassessment tools that can be used to evaluate how anthropogenic changes may influence vegetation quality, species composition and environmental integrity. The approach is primarily stationed on floristic composition and disturbance tolerance at study sites. The objectives of this study were to: 1) study how anthropogenic disturbances due to land use/cover changes in the northwestern coastal desert affected its ecological quality as indicated by FQ indices; and 2) to evaluate the use of FQ indices as tools for characterizing anthropogenic disturbance among the habitats of Mediterranean desert ecosystem. Stands representing the main habitats were surveyed during 2011 through 2015 and data were compared to historic data collected before the developmental activities. The study revealed a trend of decline with time in the floristic quality of the study area as was indicated by floristic quality measures used (mean coefficient of conservatism, FQAI, and adjusted FQAI). Similar trend of decline in native and perennial species richness, and increase in non-native and annual species richness was observed for the period investigated from 1980s to time. At the habitat level, similar trend of decline in the floristic quality was observed, with the current time attaining the least values of FQ indices for all the habitats. The anthropogenic disturbance index (ADI) was developed in the current study as a quantitative measure of the level of disturbance and as an indicator to evaluate site’s ecological condition. The ADI exhibited significant negative relationship with the FQ indices, revealing that it can be recognized as useful index of anthropogenic disturbance that would complement the use of FQ indices in evaluating site ecological condition. The high association between ADI and the adjusted FQAI compared to the FQAI, confirms that the former signals the level of disturbance better than later. Although the adjusted FQAI has been developed and used in assessing vegetation quality of wetland, the current study revealed that it can be employed successfully for assessing and monitoring changes in vegetation quality and ecological integrity of deserts and arid ecosystems. For full and comprehensive evaluation of site’s ecological condition, the use of multiple bioindicators is recommended.

Facilitation influences patterns of perennial species abundance and richness in a subtropical dune system.

Positive interactions in plant communities are under-reported in subtropical systems most likely because they are not identified as stressful environments. However, environmental factors or disturbance can limit plant growth in any system and lead to stressful conditions. For instance, salinity and low nutrient and water availability generate a gradient of stressful conditions in coastal systems depending on distance to shore. In a tropical coastal system in SE Brazil, we aimed to assess whether Guapira opposita, a shrub common in restinga environments, acted as nurse involved in ecological succession and which factors influenced its facilitation process. We sampled perennial species above 10 cm in height under the canopy of 35 G. opposita individuals and in neighbouring open areas. Shrub height, canopy area and distance to freshwater bodies were measured in the field, and distance to the ocean was obtained from aerial images. In addition, we measured the distance to the closest forest patch as a potential source of seeds. Plant abundance and species richness were higher under the canopy of G. opposita than in open areas. Facilitation by G. opposita was mainly determined by shrub height, which had a positive relationship with woody and bromeliads abundance and species richness while there was no relationship with the other factors. Overall, our data evidence that tropical environments may be highly stressful for plants and that nurse species play a key role in the regeneration of restinga environments, where their presence is critical to maintain ecosystem diversity and function.

Seed bank of seasonally flooded grassland: experimental simulation of flood and post-flood

Wetland seed banks comprise the propagules of plant species that have species-specific germination requirements for germination in either flooded or dry conditions. At the community level, wetland structure and succession during and after a seasonal flooding event depends upon the early life-history requirements of species, including germination under flooded and dry conditions. We examined the effects of simulated flood and post-flood scenarios on seedling emergence from a seed bank of seasonally flooded grassland in the Pantanal, Brazil. Field samplings were conducted in both wet and dry seasons, both of which were subject to flood and post-flood conditions. A total of 70 species emerged from the seed bank, dominated by Poaceae and Cyperaceae. Sixteen species were exclusive to the wet and one exclusive to the dry season. The richness of perennial species was higher under flood conditions, while the richness of annuals was greater post-flood. In general, the aquatic and amphibious species exhibited a significant germination response to flooding. Terrestrial species only germinated in post-flood conditions, with higher richness in the dry season. Four species had high seedling abundance in both treatments. The capacity of regeneration by seeds is high in these grasslands and can be increased by seasonal flooding and drawdown. In these seasonally flooded grasslands, we observed three main germination strategies: under flooded conditions, aquatic and amphibious species; post-flood conditions, an explosion of annual amphibious and terrestrial species; and in moist soil, perennial terrestrial species. The differential responses to flooding versus post-flood conditions help to maintain the structure and species richness in the community over time.

The underappreciated role of life history in mediating the functional consequences of biodiversity change

Biodiversity is changing on both global and local scales, motivating research to understand the consequences of these changes for how communities and ecosystems function. Here, we explore the role of life history strategies in mediating biodiversity and ecosystem functioning. In particular, we evaluate how the composition, biomass (% cover), and richness of perennial (persistence ≥ 1 year) and ephemeral (persistence &lt; 1 year) species change along a gradient of increasing seaweed species richness on a rocky shoreline. We show that the majority of biomass is comprised of perennial species, especially where overall richness is low, whereas the majority of species are ephemeral, especially where overall richness is high. We then present and discuss the results of an 18‐month field manipulation quantifying the factorial effects of tidal elevation, wave exposure, herbivore removals, thermal and desiccation stress amelioration, and nutrient additions on perennial versus ephemeral species. In particular, the diversity of ephemeral species was strongly affected, relative to perennial species, by tidal elevation, wave exposure, and herbivory; herbivores reduced diversity of ephemeral species relative to perennials. Relative to perennial cover, ephemeral cover was greater higher on the shore, in more wave‐exposed habitats, and where herbivores were removed, plots were unscreened, and/or nutrients were added. Thus, perennials and ephemerals responded differently to environmental context and experimental manipulation. We compared nitrate uptake and photosynthesis rates of ephemeral and perennial species and found that maximum nitrate uptake and photosynthesis rates of ephemerals were twice as high as those of perennials. These results highlight the disproportionate roles that ephemeral species play in mediating ecosystem‐level processes. In combination with our comparisons of the diversity and cover of perennial and ephemeral species along a biodiversity gradient, these results demonstrate the utility of incorporating life history traits into our efforts to understand the functional consequences of biodiversity change.

Impacts of invasive alien trees on threatened lowland vegetation types in the Cape Floristic Region, South Africa

This study investigated the autogenic recovery potential of native vegetation after clearing of dense stands of invasive alien trees in two critically endangered vegetation types in South Africa's Cape Floristic Region: Cape Flats Lowland Fynbos and Swartland Alluvium Fynbos. Sampling was done in areas previously occupied by the invasive tree Acacia saligna and plantations of Pinus radiata and in a fynbos reference site. Treatments varied in terms of the length of invasion and management histories.Plots previously under pines recovered well in terms of indigenous perennial species richness, but indigenous species cover decreased with increasing number of planting rotations. Areas cleared of acacia recovered poorly in terms of indigenous species cover (after one cycle of invasion), and indigenous species richness exhibited a declining trend with increasing cycles of invasion. Proteoid overstorey was lost in all previously invaded/planted plots and this element will need to be re-introduced to areas after one cycle of invasion regardless of the invasive species. Acacias changed some abiotic variables after two cycles of invasion.Follow-up clearing generally promoted better vegetation recovery in terms of overall species richness and structure but care should be taken not to damage indigenous ericoid shrubs. Overall, acacia invasion caused a greater change in biodiversity and vegetation structure than pine plantations.

Vegetation damage caused by high densities of burrowing bettongs (Bettongia lesueur) at Arid Recovery

Burrowing bettongs (Bettongia lesueur) reached high densities within the fenced Arid Recovery reserve. Grazing pressure was assessed by comparing the vegetation inside and outside the reserve during April in 2012, 2013 and 2014. Mean numbers of bettong tracks crossing small 10 m × 1 m plots overnight in the main exclosure were 20 in 2012, decreasing to 4 in 2013 and 3 in 2014. Similar declines were present in the second expansion, where tracks decreased from 7 in 2012 to 3 in 2013 and 2 in 2014. Perennial plant species richness decreased significantly over the study period. Acacia aneura, Acacia ligulata, Atriplex vesicaria, Crotalaria eremaea, Dodonaea viscosa, Enchylaena tomentosa, Maireana astrotricha and Sida ammophila were the most heavily grazed species within the reserve. Overall, more than 25% of plants showed some form of conspicuous grazing. C. eremaea and E. tomentosa showed little damage outside the reserve. Inside the reserve many C. eremaea were dead and heavily browsed and few E. tomentosa remained. Recent recruitment of A. ligulata and D. viscosa was also much higher outside the reserve. High densities of burrowing bettongs were associated with declines in vegetation condition potentially impacting other species and the ecosystem as a whole.