Lawn Species Research Articles

Divergence in diversity-area relationships between lawn and non-lawn plants in residential landscapes

ContextIn residential landscapes, people acknowledge and manage larger, conventionally attractive plants differently than smaller, less conspicuous ones, possibly leading to a divergence in basic ecological patterns such as diversity-area relationships.ObjectivesWe tested for divergences between lawn and non-lawn plants, and compared perceived and actual species richness in residential yards. We hypothesized that: (1) homeowner perception of plant species richness is more related to the actual species richness of non-lawn plants than lawn plants, and (2) alpha diversity will increase more rapidly, and beta diversity will decrease less rapidly for non-lawn plants than lawn plants with increasing spatial scale.MethodsWe recorded all plant species in four 5 × 5 m plots in the front and back yards of 30 residences within four neighborhoods of Gainesville, Florida, United States (N = 238 plots). We also surveyed residents regarding perceived plant species richness in their yards.ResultsWe detected 386 non-lawn and 140 lawn species. Perceived plant species richness was positively related to non-lawn species richness and negatively related to lawn species richness, suggesting perception of species richness largely reflected that of non-lawn plants. Alpha diversity increased more rapidly, while beta diversity decreased less rapidly, for non-lawn plants than lawn plants with increasing spatial scale, although lawns had more species within individual yards.ConclusionsFindings revealed a divergence in diversity-area relationships between different plant groups in residential landscapes. We should consider the ecological implications of unrecognized plant diversity, particularly in residential lawns, where management often strives to limit plant species richness.

Preemergence herbicide effects on St. Augustinegrass establishment

AbstractSt. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] is one of the most common turfgrass lawn species of warm‐season climates. Like many turfgrasses, it is produced as sod. Weed control during sod production is problematic, due in part to intolerance of St. Augustinegrass to a range of useful turfgrass herbicides, and because the open canopy and growth‐conducive conditions of sod production favor certain difficult‐to‐control weeds. Although those weeds are best preventatively controlled using preemergence herbicides, many preemergence herbicides also adversely affect vegetative propagation of turfgrasses. Field research was conducted at the Mississippi State University, near Starkville, Mississippi, USA, to evaluate the effects of dithiopyr, pendimethalin, prodiamine, liquid‐ and granular‐applied oxadiazon, atrazine, S‐metolachlor, atrazine + S‐metolachlor, and indaziflam on St. Augustinegrass establishment from plugs. Plots (2.25 m2) were planted with 10 plugs (225 cm2 apiece), and preemergence herbicides were applied at standard use rates 1 day after planting. Visual estimates of percentage cover were collected weekly, and aerial imagery was collected weekly to biweekly. Visual cover and vegetation index data were regressed to estimate days to reach 50% maximum nontreated response. Liquid‐applied oxadiazon and atrazine were the only treatments that did not increase days to reach 50% cover in both replication years. Dithiopyr, prodiamine, S‐metolachlor, and indaziflam increased days to reach 50% cover in both replication years. The normalized difference vegetation index, ratio vegetation index, and chlorophyll index‐red edge derived from an aerial sensor, detected similar, but fewer, treatment differences compared to estimated visual cover.

Getting Into the “weeds”: An Introduction to Common Lawn Plants and Their Ecological Benefits in North Central Florida

Maintaining monoculture lawns is resource intensive and can have environmental impacts on arthropod and aquatic communities. Here we introduce the reader to some of the many native plants that establish in lawns and if left to grow can provide ecological benefits to urban landscapes. Most resources and marketing regarding these plants focus on killing them rather than on their ecological benefits. This publication introduces the audience to these species and provides information about the biology and benefits of these species, as well as resources to learn more about self-recruiting lawn species.

Evolutionary Dynamics of the Repeatome Explains Contrasting Differences in Genome Sizes and Hybrid and Polyploid Origins of Grass Loliinae Lineages.

The repeatome is composed of diverse families of repetitive DNA that keep signatures on the historical events that shaped the evolution of their hosting species. The cold seasonal Loliinae subtribe includes worldwide distributed taxa, some of which are the most important forage and lawn species (fescues and ray-grasses). The Loliinae are prone to hybridization and polyploidization. It has been observed a striking two-fold difference in genome size between the broad-leaved (BL) and fine-leaved (FL) Loliinae diploids and a general trend of genome reduction of some high polyploids. We have used genome skimming data to uncover the composition, abundance, and potential phylogenetic signal of repetitive elements across 47 representatives of the main Loliinae lineages. Independent and comparative analyses of repetitive sequences and of 5S rDNA loci were performed for all taxa under study and for four evolutionary Loliinae groups [Loliinae, Broad-leaved (BL), Fine-leaved (FL), and Schedonorus lineages]. Our data showed that the proportion of the genome covered by the repeatome in the Loliinae species was relatively high (average ∼ 51.8%), ranging from high percentages in some diploids (68.7%) to low percentages in some high-polyploids (30.7%), and that changes in their genome sizes were likely caused by gains or losses in their repeat elements. Ty3-gypsy Retand and Ty1-copia Angela retrotransposons were the most frequent repeat families in the Loliinae although the relatively more conservative Angela repeats presented the highest correlation of repeat content with genome size variation and the highest phylogenetic signal of the whole repeatome. By contrast, Athila retrotransposons presented evidence of recent proliferations almost exclusively in the Lolium clade. The repeatome evolutionary networks showed an overall topological congruence with the nuclear 35S rDNA phylogeny and a geographic-based structure for some lineages. The evolution of the Loliinae repeatome suggests a plausible scenario of recurrent allopolyploidizations followed by diploidizations that generated the large genome sizes of BL diploids as well as large genomic rearrangements in highly hybridogenous lineages that caused massive repeatome and genome contractions in the Schedonorus and Aulaxyper polyploids. Our study has contributed to disentangling the impact of the repeatome dynamics on the genome diversification and evolution of the Loliinae grasses.

Long-term Performance of Warm-season Turfgrass Species under Municipal Irrigation Frequency Restrictions

Landscape irrigation frequency restrictions are commonly imposed by water purveyors and municipalities to curtail domestic water use and to ensure adequate water supplies for growing populations during times of drought. Currently, published data are lacking concerning irrigation frequency requirements necessary for sustaining acceptable levels of turfgrass quality of commonly used warm-season turfgrass species. The objective of this 3-year field study was to determine comparative turfgrass quality of drought-resistant cultivars of four warm-season lawn species in the south–central United States under irrigation frequency regimes of 0, 1, 2, 4, and 8× monthly. Turfgrasses used in the study were based on previously reported drought resistance and included ‘Riley’s Super Sport’ (Celebration®) bermudagrass [Cynodon dactylon (L.) Pers.], ‘Palisades’ zoysiagrass (Zoysia japonica Steud.), ‘Floratam’ st. augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze], and ‘SeaStar’ seashore paspalum (Paspalum vaginatum Swartz). During each growing season, slightly reduced irrigation volumes and bypassed events resulted from the 8× monthly treatment (34.95 cm, 38.13 cm, and 27.33 cm) compared with the 4× monthly treatment (35.36 cm, 40.84 cm, and 28.70 cm) in years 1, 2, and 3, respectively. For the once weekly treatment, the average fraction of reference evapotranspiration (ETo) supplied by effective rainfall and irrigation during the summer months was 1.22, 0.67, and 0.83 in years 1, 2, and 3, respectively, and was generally adequate to support acceptable turfgrass quality of all warm-season turfgrasses evaluated. Under the less than weekly irrigation frequency, st. augustinegrass and seashore paspalum generally fell to below acceptable quality levels because the average fraction of ETo supplied by effective rainfall and irrigation during the summer months of years 2 and 3 was 0.51, 0.39, and 0.26 for the 2× monthly, 1× monthly, and unirrigated treatments, respectively. Bermudagrass generally outperformed all other species under the most restrictive irrigation frequencies and also did not differ statistically from zoysiagrass. These results show that as irrigation frequency is restricted to less than once per week, species selection becomes an important consideration.

Plant biodiversity in residential yards is influenced by people’s preferences for variety but limited by their income

Residential yards are a unique component of the urban environment and harbor high cultivated plant biodiversity; however, why and how people create yards with so many plant species is not well understood. To investigate this pattern, we studied the relationships between residents’ preferences, income, and yard plant biodiversity in the Salt Lake Valley, Utah, USA where most of the urban vegetation is intentionally cultivated. We conducted in-person interviews, distributed written surveys, and inventoried the biodiversity (i.e., genus and species richness) of ornamental herbaceous flowering plants and lawn plants in residential yards located in neighborhoods across income levels. We found that 95% of surveyed residents valued having ‘plants that create variety in the yard’ (‘variety’ left open to interpretation) and that 47% of interviewed residents expressed an emotional connection to variety. On average, general plant variety was more important to residents than high plant biodiversity (i.e., a specified type of variety), but they also exhibited a preference for neat monoculture lawns lacking in biodiversity and other types of variety. Residents’ preferences for general plant variety, and biodiversity specifically, were not necessarily reflected in their yards. Higher income households had greater flowering plant variety in terms of number of different flower colors, inflorescence types, and genera, but lower lawn species biodiversity due to a reduction in weedy species. Overall, our study shows that most residents in this region prefer plant variety in their yards more than biodiversity specifically, and that people with higher incomes can better achieve these preferences.

Influence of Climate and Management on Patterns of Taxonomic and Functional Diversity of Recreational Park Vegetation

Recreational urban parks support diverse assemblages of plants that through their functions, contribute beneficial services to billions of individuals throughout the world. Drivers of vegetation-derived services in parks are complex, as climate and park management interact with the functioning of multiple species of vegetation types. Yet, informal observations suggest that recreational parks are constructed consistently to specific principles of landscape design. Here we ask: what are the patterns of functional traits and vegetation diversity in cities of varying climate in the United States, and how do these patterns result in a consistent typology of recreational park? We hypothesized that increased aridity would exclude species not adapted to warm, dry climates, thereby reducing local, or alpha, taxonomic diversity and shifting community composition. However, a similar preference of park managers in the United States for suites of service-based functional traits leads to similarity of mean values of services traits in recreational parks among cities, regardless of climate differences. We tested this hypothesis by surveying lawn species, comprised of herbaceous turf and spontaneous plants, and woody species in fifteen recreational parks across Baltimore MD, Riverside CA, and Palm Springs CA, three cities that contain multiple parks but differ in regional climate. With increasing aridity, taxonomic alpha diversity decreased and plant physiology shifted, yet no differences were observed among most service-based functional traits. Among the cities surveyed, no significant differences were observed in functional dispersion of woody and spontaneous species or most service-based traits. Taxonomic composition differed in each city for all vegetation types, while suites of service-based traits differed between Baltimore and the two more arid cities of Riverside and Palm Springs. Our results suggest that across the U.S., service-based functional traits are consistent, even when arising from unique compositions and abundances of species in recreational parks. We interpret these results as an interaction between climate and the preferences of recreation park managers for services, creating a pattern of vegetation diversity where taxonomic alpha and beta diversity vary among regions while specific suites of services remain available.

Time Is Not Money: Income Is More Important Than Lifestage for Explaining Patterns of Residential Yard Plant Community Structure and Diversity in Baltimore

Plant biodiversity is affected by limiting resources such as water, nutrients, and sunlight. In urban settings, such as residential yards, however, limiting resources may also include the social factors of time and money spent on yard care. To examine the role that these precious human resources play in determining plant community structure and diversity, we surveyed homeowners and their yards in 12 neighborhoods across Baltimore City and Baltimore County, Maryland, visiting a total of 96 residential properties. We chose neighborhoods based on residents’ median income (a proxy for money) and lifestage (a proxy for time) as determined by ESRI's Tapestry dataset [older (>65 and most likely retired with more free time) versus younger (<65 and most likely working with less free time)]. At each residential yard, we studied four major plant types: lawn species, flowering herbaceous plants (excluding grasses), trees, and invasive species. For the flowering plants, we documented the number, size, and color of flowers, and calculated total floral area. We found that residential yards harbored high plant diversity with 89 tree species, 82 lawn species, and 80 flowering plant genera. Lawn richness was not related to the neighborhood-level lifestage of the residents or their income,; rather, all lawns were equally weedy. Consistently, we found that yards in higher income neighborhoods and larger yards had greater abundance of plants and greater diversity of flowering herbaceous plants, trees, and invasive species, whereas lifestage was rarely associated with plant diversity. Additionally, we found front yards had greater floral area than back yards, while back yards had greater tree abundance and tree diversity than front yards. Finally, we found that residents who spent more time doing yard work had more flowering plants, flower colors, and floral genera. Overall, yards in highincome neighborhood, and large yards had the greatest plant biodiversity, indicating that money is the more precious human resource for creating and maintaining biodiverse residential yards.

ОСОБЕННОСТИ ЦЕНОФЛОРЫ ГАЗОНОВ ГОРОДА УФЫ (РЕСПУБЛИКА БАШКОРТОСТАН)

Lawns are the most important element of the modern urban landscape. They are made by planting grasses at specially prepared homogeneous plots. The coenoflora of Ufa lawns currently includes 112 species of higher plants from 90 genera and 26 families. The characteristic of coenoflora is given on the basis of the performed geobotanical descriptions. Classical floristical analysis of coenoflora is carried out for various floristic spectra: family-genus, biomorphological, horological, ecological, and phytosociological. An assessment of the economic significance of the species was also given. The adventive component of the coenoflora consisting of 29 species was analyzed individually. It accounts for 25.9 % of the total species composition. It is specified that indexes of adventization of coenoflora are relatively low in Ufa in comparison with many other coenofloras of large cities. It can be connected with nature of habitats (absence of soil cover movement and relatively dense cover of lawn grasses and, consequently, absence of soil areas not occupied by plants. Such conditions prevent growing of adventive species). Particularly aggressive invasive plant species (Erigeron annuus, Hordeum jubatum, Solidago canadensis ) are recorded in the group of adventive species. The research proves that in large cities with great disruption of vegetation cover there is an increasing necessity of arranging high-quality lawn ground covers of different types, based on the correct selection of lawn species, optimal agricultural techniques. Ongoing processes that take place in the lawn plant communities should be considered.

Less is more! Rapid increase in plant species richness after reduced mowing in urban grasslands

Urban lawns provide space for recreation in cities, and they are an important part of urban green infrastructures. However, most lawns are intensively managed. As only few plant species can survive frequent mowing, urban lawns typically harbor only a limited number of plant species. To improve the biodiversity of urban lawns, it is often suggested to reduce the mowing frequency. Here, we studied the plant diversity of urban grasslands that have recently undergone management changes from mowing every few weeks to mowing only once or twice per season and compared them to intensively managed lawns. Within six years after the management changes, the grasslands with reduced mowing frequency hosted 30% more plant species than intensively managed lawns, and they were more heterogeneous both within and between grasslands. Additionally, the species composition of less frequently mown grasslands shifted from common mowing-tolerant lawn species to typical meadow species. Our study thus shows that the reduction of mowing is a simple and effective tool for increasing the biodiversity in urban grasslands.

Climate and lawn management interact to control C4 plant distribution in residential lawns across seven U.S. cities.

In natural grasslands, C4 plant dominance increases with growing season temperatures and reflects distinct differences in plant growth rates and water use efficiencies of C3 vs. C4 photosynthetic pathways. However, in lawns, management decisions influence interactions between planted turfgrass and weed species, leading to some uncertainty about the degree of human vs. climatic controls on lawn species distributions. We measured herbaceous plant carbon isotope ratios (δ13 C, index of C3 /C4 relative abundance) and C4 cover in residential lawns across seven U.S. cities to determine how climate, lawn plant management, or interactions between climate and plant management influenced C4 lawn cover. We also calculated theoretical C4 carbon gain predicted by a plant physiological model as an index of expected C4 cover due to growing season climatic conditions in each city. Contrary to theoretical predictions, plant δ13 C and C4 cover in urban lawns were more strongly related to mean annual temperature than to growing season temperature. Wintertime temperatures influenced the distribution of C4 lawn turf plants, contrary to natural ecosystems where growing season temperatures primarily drive C4 distributions. C4 cover in lawns was greatest in the three warmest cities, due to an interaction between climate and homeowner plant management (e.g., planting C4 turf species) in these cities. The proportion of C4 lawn species was similar to the proportion of C4 species in the regional grass flora. However, the majority of C4 species were nonnative turf grasses, and not of regional origin. While temperature was a strong control on lawn species composition across the United States, cities differed as to whether these patterns were driven by cultivated lawn grasses vs. weedy species. In some cities, biotic interactions with weedy plants appeared to dominate, while in other cities, C4 plants were predominantly imported and cultivated. Elevated CO2 and temperature in cities can influence C3 /C4 competitive outcomes; however, this study provides evidence that climate and plant management dynamics influence biogeography and ecology of C3 /C4 plants in lawns. Their differing water and nutrient use efficiency may have substantial impacts on carbon, water, energy, and nutrient budgets across cities.

Lactic Acid is a Major Contributor to Dog Urine Injury in Cool‐Season Lawn Species

Dog (Canis familiaris L.) urine can cause severe injury to lawns. Despite the circumstantial evidence that salts from urine are responsible, there is no known connection between a particular component of dog urine and the cause of grass injury. The objective of this study was to evaluate cool‐season lawn grasses in response to the major components of dog urine. Urea, uric acid, lactic acid, creatinine, and bilirubin were applied either separately or with auxin or kinetin to Kentucky bluegrass (Poa pratensis L.), tall fescue (Festuca arundinacea Schreb), and perennial ryegrass (Lolium perenne L.). A solution containing 20 g urea L−1 and 10 g ammonium sulfate L−1 was used to simulate the levels of salinity (∼15 dS m−1) and total N in dog urine. This solution caused slight discoloration on leaf tips with phytotoxic levels ranging from 5 to 12%. Lactic acid at 3.5 g L−1 caused significant leaf injury on the three species, with phytotoxic levels ranging from 40 to 87%, and eventually the death of grasses and symptoms similar to dog urine patch. In conclusion, salts in dog urine caused injury, but the severity was not as high as that associated with lactic acid in dog urine.

Continental-scale homogenization of residential lawn plant communities

Residential lawns are highly managed ecosystems that occur in urbanized landscapes across the United States. Because they are ubiquitous, lawns are good systems in which to study the potential homogenizing effects of urban land use and management together with the continental-scale effects of climate on ecosystem structure and functioning. We hypothesized that similar homeowner preferences and management in residential areas across the United States would lead to low plant species diversity in lawns and relatively homogeneous vegetation across broad geographical regions. We also hypothesized that lawn plant species richness would increase with regional temperature and precipitation due to the presence of spontaneous, weedy vegetation, but would decrease with household income and fertilizer use. To test these predictions, we compared plant species composition and richness in residential lawns in seven U.S. metropolitan regions. We also compared species composition in lawns with understory vegetation in minimally-managed reference areas in each city. As expected, the composition of cultivated turfgrasses was more similar among lawns than among reference areas, but this pattern also held among spontaneous species. Plant species richness and diversity varied more among lawns than among reference areas, and more diverse lawns occurred in metropolitan areas with higher precipitation. Native forb diversity increased with precipitation and decreased with income, driving overall lawn diversity trends with these predictors as well. Our results showed that both management and regional climate shaped lawn species composition, but the overall homogeneity of species regardless of regional context strongly suggested that management was a more important driver.

Eкологічний аналіз видового складу газонного культурфітоценозу

The paper presents the results of the ecological analysis of species composition of newly created lawn from plants varieties of Ukrainian breeding on the territory of the National University of Life and Environmental Sciences of Ukraine. It is determinated that habitats of dominant lawn species characterized by conditions of insufficient, uneven moisture rich salt content, neutral pH reaction substrate and sufficient stock of available nitrogen, marked characteristic of northern forest steppe ecotypes, including gray soils of Holosiivskyi district of Kyiv.

Allelopathic Potential of Invasive Plantago virginica on Four Lawn Species.

Plantago virginica L. has invaded many lawn ecosystems in the Eastern part of China. The invasion has incurred an economic cost to remove them. In order to prevent the invasion, it is critical to understand the invasive mechanisms of this species. However, few studies have been conducted on the allelopathic mechanisms of its invasion. In this study, we examined allelopathic effects of P. virginica on germination of seeds and growth of seedlings of four widely used lawn species. We found extensive allelopathic potential of P. virginica on other lawn species, which varied with species and developmental stage. While most effects of the extracts of P. virginica were inhibitory, some variables in some species were promoted by the addition of the extracts. The extracts of P. virginica significantly inhibited seed germination of Agrostis matsumurae. While the overall differences in seed germination rate of Poa annua were significant among treatments, difference between control and any of the treatments was not significant. The height of seedlings of A. matsumurae and Cynodon dactylon was significantly lower under the treatments of adding extracts of P. virginica. In contrast, growth of seedlings of Festuca elata and P. annua did not show significant differences among treatments. The root length of A. matsumurae, C. dactylon and P. annua was suppressed by the extracts of P. virginica whereas root length of F. elata was not affected. Aboveground biomass of A. matsumurae and F. elata was significantly higher than control, except for F. elata at the concentration of 50mg/mL, whereas aboveground biomass of C. dactylon and P. annua was reduced at higher concentrations of the extracts. Except for A. matsumurae, root biomass of the other three lawn species declined under the treatments with the extracts of P. virginica. Our results revealed that P. virginica had allelopathic potential on four lawn species and supported the theory of “novel weapons hypothesis”. Invasion by P. virginica in lawn can be moderated by selecting those species that are not affected or promotionally affected by it.

Assessment of an integrated peat-harvesting and reclamation method: peatland-atmosphere carbon fluxes and vegetation recovery

We document a two-year experimental trial of a recently-developed integrated peat-harvesting and reclamation technique at a poor fen in northern Ontario, Canada. We removed and conserved the uppermost ~0.3 m of peat in blocks while deeper peat was harvested from the resultant pit. We allowed the extraction pit to flood with shallow groundwater, and then reclaimed the conserved surficial peat blocks by transplanting them into the flooded pit where they formed a low, floating mat. In the 2nd year after harvest average Sphagnum cover in our experimental plot was intermediate (~25 %) between hummocks (~100 %) and hollows (~10 %) at an adjacent unharvested reference plot. Mean rates of Sphagnum productivity were greater in the experimental plot (65–86 g m−2 month−1) than in the reference plot (45–55 g m−2 month−1) for both hummock (S. fuscum) and lawn (S. magellanicum) species, although not significantly so, indicating that the transplant had no adverse effects on Sphagnum health. The inundated soil conditions in the trial pit prevented the large carbon dioxide emissions that are characteristic of many harvested peatlands. During the second growing season midday net ecosystem exchange at the experimental plot was similar to that at hollows in the reference plot. However, the anoxic soil conditions in the experimental plot led to highly elevated methane emissions in both years. Our results demonstrate that the method can enable rapid re-establishment of a healthy Sphagnum mat and carbon dioxide sequestration function in harvested peatlands, although the global warming potential of our experimental trial was high due to elevated methane emissions.

Leaf silica concentration in Serengeti grasses increases with watering but not clipping: insights from a common garden study and literature review.

Grasses (Poaceae) lack the complex biochemical pathways and structural defenses employed by other plant families; instead they deposit microscopic silica (SiO2) granules in their leaf blades (i.e., phytoliths) as a putative defense strategy. Silica accumulation in grasses has generally been considered an inducible defense; other research suggests silica accumulation occurs by passive diffusion and should therefore be closely coupled with whole plant transpiration. We tested the hypothesis that grasses increase leaf silica concentration in response to artificial defoliation in a common garden study in the Serengeti ecosystem of East Africa. Additionally, a watering treatment tested the alternative hypothesis that leaf silica was largely driven by plant water status. Leaf silica content of two dominant C4 Serengeti grass species, Themeda triandra and Digitaria macroblephara, was quantified after a 10-month clipping × water experiment in which defoliation occurred approximately every 2 months and supplementary water was added every 2 weeks. Themeda had greater silica content than Digitaria, and Themeda also varied in foliar silica content according to collection site. Clipping had no significant effect on leaf silica in either species and watering significantly increased silica content of the dominant tall grass species, Themeda, but not the lawn species, Digitaria. Our data, and those collected as part of a supplementary literature review, suggest that silicon induction responses are contingent upon a combination of plant identity (i.e., species, genotype, life history limitations) and environmental factors (i.e., precipitation, soil nutrients, grazing intensity). Specifically, we propose that an interaction between plant functional type and water balance plays an especially important role in determining silica uptake and accumulation.

Ecology of grazing lawns in Africa.

Grazing lawns are a distinct grassland community type, characterised by short-stature and with their persistence and spread promoted by grazing. In Africa, they reveal a long co-evolutionary history of grasses and large mammal grazers. The attractiveness to grazers of a low-biomass sward lies in the relatively high quality of forage, largely due to the low proportion of stem material in the sward; this encourages repeat grazing that concomitantly suppresses tall-grass growth forms that would otherwise outcompete lawn species for light. Regular grazing that prevents shading and maintains sward quality is thus the cornerstone of grazing lawn dynamics. The strong interplay between abiotic conditions and disturbance factors, which are central to grazing lawn existence, can also cause these systems to be highly dynamic. Here we identify differences in growth form among grazing lawn grass species, and assess how compositional differences among lawn types, as well as environmental variables, influence their maintenance requirements (i.e. grazing frequency) and vulnerability to degradation. We also make a clear distinction between the processes of lawn establishment and lawn maintenance. Rainfall, soil nutrient status, grazer community composition and fire regime have strong and interactive influences on both processes. However, factors that concentrate grazing pressure (e.g. nutrient hotspots and sodic sites) have more bearing on where lawns establish. Similarly, we discuss the relevance of enhanced rates of nitrogen cycling and of sodium levels to lawn maintenance. Grazer community composition and density has considerable significance to grazing lawn dynamics; not all grazers are adapted to foraging on short-grass swards, and differences in body size and relative mouth dimensions determine which species are able to convert tall-grass swards into grazing lawns under different conditions. Hence, we evaluate the roles of different grazers in lawn dynamics, as well as the benefits that grazer populations derive from having access to grazing lawns. The effects of grazing lawns can extend well beyond their borders, due to their influence on grazer densities, behaviour and movements as well as fire spread, intensity and frequency. Variation in the area and proportion of a landscape that is grazing lawn can thus have a profound impact on system dynamics. We provide a conceptual model that summarises grazing lawn dynamics, and identify a rainfall range where we predict grazing lawns to be most prevalent. We also examine the biodiversity associated with grazing lawn systems, and consider their functional contribution to the conservation of this biodiversity. Finally, we assess the utility of grazing lawns as a resource in a rangeland context.

A novel mechanism for grazing lawn formation: large herbivore‐induced modification of the plant–soil water balance

Summary Large herbivores play a key role in creating spatial heterogeneity through the formation of grazing lawns. Recent research suggests that the currently accepted nutrient‐based theory on the formation of these grazing lawns cannot universally explain their formation in all ecosystems where they are found. We developed and investigated an alternative hypothesis on grazing lawn formation and maintenance based on herbivore effects on the plant–soil water balance. We propose that large herbivores change the soil water balance in grazing lawns through defoliation and soil compaction, causing a shift in vegetation composition towards a drought‐tolerant plant community. Investigating this idea in a tropical savanna, we indeed found profound differences in grazing lawn soil properties and water balance. In particular, defoliation increased soil temperatures and potential evaporation rates while soil compaction increased bulk density and decreased water infiltration rates, especially on fine‐textured soils. Soil moisture was therefore generally much lower in grazing lawns than in adjacent bunch grass areas. Furthermore, we found that grazing lawn species show drought‐tolerant traits, with higher leaf sodium levels, suggesting evolutionary adaptation to these herbivore‐induced dry conditions. However, leaf water potentials did not differ between grazing lawn and bunch grass species. Synthesis. This study shows that large herbivores might form grazing lawns through previously underestimated effects on water balance. Thus, future studies on large herbivore effects on vegetation should increasingly focus on additional pathways of soil compaction and defoliation. While nutrient‐based processes driving grazing lawn formation may operate during the wet season in savannas, we suggest that water balance‐based processes are additionally important during the dry season.

The effect of light availability on leaf area index, biomass production and plant species composition of park grasslands in Warsaw

How light conditions affect development of park grasslands is a question that has not been satisfactory addressed. The aim of this study was therefore determination of the level to which unfavorable light conditions influence grassy parks area and relationships between parameters which determine state of turf grasses. Researches were conducted in two parks in Warsaw, in various light conditions and included measurement of: leaf density, sward height, leaf area index (LAI), and botanical composition of the communities. The leaf density of shaded areas did not exceed 70%. LAI value varied from 0.5 to 0.9-fold lower than in the areas in half-shade and in sun. The participation of basic lawn species at Skaryszewski Park was higher under shade, while at Łazienki Kr&amp;oacute;lewskie was higher in full-sunlight areas. The state of tested grassy areas in limited solar radiation does not satisfy the requirements of recreational and representational functions. The development processes of vegetation coverage were inhibited at the sites of lower solar radiation. LAI was influenced by both leaf coverage and sward height. Agrostis stolonifera and Poa trivialis may be recommended to create grass areas under limited solar radiation.