Mowing Treatments Research Articles

호밀 리빙멀치, 토양환원, 예취처리가 유기농 콩밭 잡초 발생에 미치는 영향

ABSTRACT In organic agriculture, cover crops are used for weed control. Cover crops inhibited weed germination or growth by allelopathy or shading effects. In this study, we used rye as cover crop to control weed in organic soybean field. The main treatment was rye using method such as living mulch, incorporating and mowing. Sub-treatment was rye planting density and soybean planting density. One month after soybean sowing, weed emergency and growth had been highly suppressed by rye in all treatments. Living mulch treatment was the best effective way to control the weed about 92%, and mowing treatment was the second about 75% compare to control. The weed control efficiency between rye planting densities was similar during one month. Soybean planting density treatment was same result as rye planting density. As a result of this experiment, we recommend rye as living mulch in one row planting. Key words: cover crop; living mulch; organic agriculture; rye; soybean; weed control. 서 언 피복작물은 토양의 유실과 유거수를 방지하고 수분보전, 투수성 개선, 토양 물리성 개량, 잡초억제 및녹비활용 등 다양한 목적과 효과를 위하여 오랫동안 이용되어 왔다(Andy 2007; Reddy 2003). 여러 종류의 피복작물 중 호밀은 내한성이 높고 건물 생산량이 많아 피복작물로 특히 많이 활용되어 왔

Grassland canopy management and native tallgrass species composition effects on C and N in grass canopies and soil

Grassland canopy management (spring burn, mowing and residue removal in late-summer, or no management) and native tallgrass species composition (cool season mixture, warm season mixture, or combined cool and warm mixture) effects on C and N in aboveground biomass and soil were investigated at Brookings SD on a previously-plowed Barnes clay loam (fine-loamy, superactive, frigid Calcic Hapludoll). During the last 2 yr of the 9-yr experiment, shoot biomass was affected by canopy management with the burn (2,730 kg ha−1) and mow (3,421 kg ha−1) treatments containing less than no management (4,655 kg ha−1). Burn treatment biomass contained 1,189 kg ha−1 and 25 kg ha−1 of C and N, mow contained 1,433 kg ha−1 and 33 kg ha−1 of C and N, while no management contained 2,014 kg ha−1 and 39 kg ha−1 of C and N, respectively. Soil C accumulation was independent of grass species composition. Soil C accumulation rates, which increased in strong linear fashion (r2 of 0.89 to 0.92) after initial grass establishment, were 387 kg C ha−1 yr−1, 503 kg C ha−1 yr−1, and 711 kg C ha−1 yr−1 for burn, mow, and no management treatments, respectively. Thus, grassland management methods used after conversion of cropland to grassland have important effects on grass biomass and soil C accumulation.

Effects of vegetation management by mowing on ground-dwelling arthropods

Species-rich grasslands are rare in the Netherlands and need consistent vegetation management to retain their characteristic biodiversity. Roadside verges are important refuges for grassland plants since the mowing management no longer aims at traffic safety only but also strives for botanical diversity. Although arthropods are highly abundant in roadside verges, the effect of different mowing practices on this group is largely unknown. During 4 years, we studied ground beetles, weevils, ants and ground-dwelling spiders with pitfall traps in experimental plots in roadside verges with five different mowing treatments: (i) no management, (ii) and (iii) mowing once a year with and without hay removal, (iv) and (v) mowing twice a year with and without hay removal. This was done in a plant productivity gradient; the experiment was repeated in low-, medium- and high-productive verges. In the low-productive site, the effect of management on the arthropods only existed in a higher abundance in plots mown twice per year with hay removal. In the medium- and high-productive sites, mowing twice a year with hay removal resulted not only in highest abundances but also in highest arthropod species richness. Mowing twice without hay removal and mowing once with removal showed intermediate values, while mowing once per year without removal and particularly the absence of management resulted in low diversity and low abundance. To promote ground-dwelling arthropods in medium-to-high-productive grassland verges, we recommend a management of mowing twice a year with the removal of hay. It is reasoned that some form of rotational management, aiming at leaving some vegetation refuges intact after mowing events, may further promote arthropod survival. However, caution should be taken that these refuges are not too large, as overall suitability for ground-dwelling arthropod decreases rapidly in such patches. Out of several studied vegetation characteristics, the number of flowering plant species (medium-productive verge) and total flower abundance (high-productive verge) appeared to represent suitable, and easily monitored, proxies that significantly mirror arthropod diversity.

Response of the alien species Panicum acuminatum to disturbance in an Italian lowland heathland

The spread of exotic plants represents a new challenge for conservation management since practices commonly used to maintain semi-natural, open vegetation may promote the establishment of plant invaders. Panicum acuminatum Swartz is a perennial grass native to America that was naturalized in southern European heathlands. The effect of conservation management on the spread of this invasive species was studied in a heathland in NW Italy along an experimental disturbance gradient created by mowing, grazing, prescribed fire or various combinations of these treatments. Across treatments, the abundance of Panicum acuminatum was negatively correlated with the total abundance of the two dominant native species, Calluna vulgaris and Molinia arundinacea. The abundance of P. acuminatum differed significantly among treatments depending on the intensity and frequency of disturbance (phytomass removal). Thus, its abundance was highest in the repeated fire treatments as well as in the combined fire + grazing and fire + mowing treatments. Following these results, low-severity practices (grazing, mowing, occasional fire) seem most suitable to both reduce tree encroachment and control P. acuminatum spread.

Changes in wet meadow vegetation after 20 years of different management in a field experiment (North-West Germany)

Conservation and restoration of semi-natural wet grasslands often suffer from poor knowledge on successional pathways of respective habitats under different mowing treatments to derive profound management concepts. In this study, we present the results of a 20-year experiment in six semi-natural wet grassland sites in NW Germany including mowing with and without fertilizer addition and fallow. Succession was recorded by permanent plots. The studied wet grassland communities responded quite similar under equal management. Fallow resulted in the most significant changes in floristic and functional composition facilitating highly competitive rushes and tall forbs. The changes were more pronounced the more the experimental management treatment differed from the former use. For all mowing treatments without fertilizer application, we still observed directed changes in the floristic composition even after 20 years. In particular mowing twice led to a shift in floristic composition towards stress-tolerant plants with low nutrient demands, which was paralleled by decreasing productivity and strongly diminishing Ellenberg nutrient values. Our results documented that restoration of low-yielding target communities by regular mowing is possible – even in an area with high atmospheric nitrogen inputs. However, our results also show that succession did not come to an end even after 20 years, most obviously due to the continuous but very slow immigration and spread of new species.

Optimizing grassland management for flower-visiting insects in roadside verges

The decline of flower-visiting insects is a threat to ecological processes and to the services these insects provide. Roadside verges in the Netherlands span approximately 80,000 km and are often covered with semi-natural grasslands. As such, they also provide a suitable habitat for many insects, but this has received little attention so far. We investigated the effects of different management treatments on flower-visiting insects. We studied flower visitation in a 3 years old experimental set-up with five mowing treatments each replicated five times. Management types were: no management and mowing once or twice per year with and without the removal of hay, representing common forms of management and neglect. During an entire growing season, both flowers (number of species and inflorescences) as well as insects (total abundance and actual flower visits) were investigated. Mowing twice per year with removal of hay showed highest values for all measured variables and this effect persisted throughout the growing season. The early summer cut proved to be very important for insect feeding opportunities, due to the re-flowering of plants later in the growing season. Flower abundance showed high correlations with both plant species richness and the number of insect visits. Although overall, mowing twice a year with hay removal was the most beneficial treatment for flower-visiting insects, these plots were entirely devoid of flowers for some period right after mowing, indicating that a rotational scheme might further promote insect diversity and abundance.

Black oat cover crop management effects on soil temperature and biological properties on a Mollisol in Texas, USA

Management of a black oat ( Avena strigosa [Schreb.]) cover crop by mowing method (none, flail mowing, or sickle bar mowing) affected soil micro environmental conditions and soil microbial and chemical properties. Soil temperatures at depths of 0, 5, 10 and 20 cm were highest in flail mowed treatment plots (up to near 45 °C at 5 cm depth), followed by sickle bar mowed plots (averaging 10 °C lower at 5 cm depth). Lowest soil temperatures were maintained in plots that were not mowed; averaging 5 °C lower at 5 cm depth than the sickle bar mowed plots. Increasing temperature convergence was observed below 5 cm, with the highest temperature (flail mowed treatment) at 32 °C and the lowest (not mowed) at 27 °C. Microbial biomass increased significantly ( P < 0.05) from < 100 mg C kg − 1 soil in the late spring, to > 150 mg C kg − 1 in the early fall. β-glucosidase and alkaline phosphatase activities decreased slowly throughout the experiment, and were significantly greater ( P < 0.05) only when comparing the not mowed treatment to both mowing treatments. Dissolved organic C (DOC) decreased sharply, perhaps due to rainfall. Similarly, soil inorganic N decreased sharply, from approximately 0.025 mg N kg − 1 soil in the not mowed plots, to approximately 0.005 mg N kg − 1 during a rainy period. Immobilization of N during rapid microbial biomass growth could also explain the decrease in inorganic N. While resin-extractable P was significantly higher in the not mowed treatment, few differences in extractable P were detected between either mowing treatment during the experiment. Standing oat residues maintained higher levels of soil enzyme activities and the lowest microbial biomass, suggesting that controlling contact of crop residues with the soil may introduce a rate limiting factor for residue decomposition. The timing of residue decomposition in this system may be delayed by leaving most of the plant biomass above the ground (i.e. not mowed or sickle bar mowed). These residue management factors may be important in controlling soil nutrient transformations and soil organic matter maintenance in subtropical climates.

Pecan Shell Mulch Impact on ‘Loring’ Peach Tree Establishment and First Harvest

Pecan (Carya illinoinensis) shells are waste products that are occasionally used for mulch in ornamental landscape settings, yet most shell waste is left in piles near the shelling facility or discarded by other methods. If another use for this waste product could be developed, it may add income for pecan producers and provide peach (Prunus persica) growers with another option for weed control. A block of ‘Loring’ peach trees grafted onto ‘Halford’ rootstocks was planted at a spacing of 18 × 22 ft in Feb. 2005 at the Cimarron Valley Research Station near Perkins, OK, to determine the effect of pecan shell mulch on peach trees. Five treatments were imposed: no weed control except mowing (MOW), weed-free 6- × 6-ft area maintained with glyphosate herbicide (SPRAY), 6-ft × 6-ft × 2-inch deep mulch (TWO), 6-ft × 6-ft × 4-inch deep mulch (FOUR), and 6-ft × 6-ft × 6-inch deep mulch (SIX). Yields in 2008 were poorest in the MOW treatment (13.2 kg/tree and 93 fruit/tree). All other treatments did not differ. Soluble solids concentration as a measure of fruit quality and fruit weight was unaffected by treatment. Tree height, pruning weights, and trunk cross-sectional area were similar with the exception that MOW was lower for all three growth measurements beginning in 2007. Pecan mulch appears to have the potential to reduce soil pH. Foliar analysis for nitrogen (N), potassium (K), and zinc (Zn) showed treatment differences in 2006. No treatment differences were evident in 2007 and 2008 for K and Zn, but in 2008, FOUR had greater N than MOW. Tree mortality increased with pecan mulch depth. MOW, SPRAY, and TWO had little tree loss (0%–5%), whereas FOUR and SIX had 15% and 35% mortality, respectively. Tree mortality was attributed to record rains in 2007 coupled with longer soil moisture retention under the deeper mulch.

Pecan Shell Mulch Impact on ‘Loring’ Peach Tree Establishment and First Harvest

Pecan (Carya illinoinensis) shells are waste products that are occasionally used for mulch in ornamental landscape settings, yet most shell waste is left in piles near the shelling facility or discarded by other methods. If another use for this waste product could be developed, it may add income for pecan producers and provide peach (Prunus persica) growers with another option for weed control. A block of ‘Loring’ peach trees grafted onto ‘Halford’ rootstocks was planted at a spacing of 18 × 22 ft in Feb. 2005 at the Cimarron Valley Research Station near Perkins, OK, to determine the effect of pecan shell mulch on peach trees. Five treatments were imposed: no weed control except mowing (MOW), weed-free 6- × 6-ft area maintained with glyphosate herbicide (SPRAY), 6-ft × 6-ft × 2-inch deep mulch (TWO), 6-ft × 6-ft × 4-inch deep mulch (FOUR), and 6-ft × 6-ft × 6-inch deep mulch (SIX). Yields in 2008 were poorest in the MOW treatment (13.2 kg/tree and 93 fruit/tree). All other treatments did not differ. Soluble solids concentration as a measure of fruit quality and fruit weight was unaffected by treatment. Tree height, pruning weights, and trunk cross-sectional area were similar with the exception that MOW was lower for all three growth measurements beginning in 2007. Pecan mulch appears to have the potential to reduce soil pH. Foliar analysis for nitrogen (N), potassium (K), and zinc (Zn) showed treatment differences in 2006. No treatment differences were evident in 2007 and 2008 for K and Zn, but in 2008, FOUR had greater N than MOW. Tree mortality increased with pecan mulch depth. MOW, SPRAY, and TWO had little tree loss (0%–5%), whereas FOUR and SIX had 15% and 35% mortality, respectively. Tree mortality was attributed to record rains in 2007 coupled with longer soil moisture retention under the deeper mulch.

Managing Reed Canarygrass (Phalaris Arundinacea) to Aid in Revegetation of Riparian Buffers

An experiment compared 2 yr of mowing, mulching, spot treatment with glyphosate, or no maintenance for reed canarygrass control and measured their effect on the establishment of red alder and arroyo willow. At one site, pretransplant control of reed canarygrass was poor, and mulching or no maintenance gave 9 and 14% control, respectively, at 5 mo after planting (MAP), but glyphosate spot treatment and mowing resulted in 89% and 72% control, respectively. The highest leafiness percentage by 24 MAP for arroyo willow and red alder at that site occurred in spot-treated plots (59 and 6%, respectively). Tree protection resulted in 30% more arroyo willow saplings with leaves at 24 MAP, at an average height of 68 cm at 17 MAP. Over the 2-yr trial at that site, mowing required far more time (30.6 min/plot) than either mulching or spot spraying (18.6 and 13.5 min/plot, respectively). At a second site, pretransplant weed control was excellent and maintenance programs controlled reed canarygrass from 88 to 98% by 5 MAP. Tree leafiness of red alder was improved 20% at 24 MAP by tree protection, with protected trees being 107 cm tall compared with 64 cm when left bare. Over the 2-yr trial at that site, mulching required 14.8 min/plot, compared with 12.9 and 7.6 min/plot for mowing and spot treatment. Annual spot treatment of reed canarygrass regrowth with glyphosate may be the most cost-effective means of achieving successful reestablishment of native broadleaf trees in northwestern riparian systems.

Mowing-Induced Changes in Soil Seed Banks and Populations of Plumeless Thistle (Carduus acanthoides) and Musk Thistle (Carduus nutans)

Populations of plumeless thistle and musk thistle were mowed at various growth stages at two separate sites in Maryland during a 6-yr period to elucidate relationships among seed rain, soil seed banks, and population recruitment. The majority of seeds (96%) in the soil profile were distributed within 7.6 cm of the surface at both sites. Mowing plumeless thistle when most of the flower heads were at the full bud or postbloom stage did not reduce seed bank or plant densities, unlike mowing at full bloom, which significantly and quickly reduced both. Musk thistle responded differently, with plant density declining only with the postbloom mowing treatment, which occurred after the parent plant had dispersed seeds and died. Seed bank densities were unchanged by this treatment. This indicates that other factors may limit the recruitment and maintenance of musk thistle, such as allelochemical production by parents and interspecific plant competition. Density of musk thistle declined over an 11-yr period at one monitoring site, whereas plumeless thistle remained unchanged. The disproportionate seed-destroying activities of the weed biological control agent Rhinocyllus conicus on musk thistle may explain this difference.Nomenclature: musk thistle, Carduus nutans Wienm. CRUNU, plumeless thistle, Carduus acanthoides L. CARAC

Selective and Non‐Selective Control of Invasive Plants: The Short‐Term Effects of Growing‐Season Prescribed Fire, Herbicide, and Mowing in Two Texas Prairies

Abstract Conservation of North American grasslands is hampered by the impact of invasive herbaceous species. Selective control of these plants, although desirable, is complicated by the shared physiology and phenology of the invader and the native components of the invaded plant community. Fortunately, there is evidence that some management practices, such as prescribed fire, herbicide, and mowing, can cause differential responses in native and invasive grassland species. However, timing of treatment is critical, and fire has been shown to increase rates of invasion when implemented during the dormant season. Bothriochloa ischaemum, an introduced C4 Eurasian grass is an increasing problem in grasslands, particularly in southern and central regions of North America. To date, there has been little success in effective selective control. Two invaded grassland sites representative of Blackland Prairie and Edwards Plateau ecoregions were subjected to two growing‐season prescribed fire treatments, single and double herbicide applications, and single and double mowing treatments. Mowing had no effect on either B. ischaemum or other dominant species at either site one‐year posttreatment. However, growing‐season fire and herbicide were both effective at reducing the abundance of B. ischaemum, with other codominant species responding either negatively to herbicide or neutrally or positively to fire. The vulnerability of B. ischaemum to growing‐season fire may be associated with the ecology of its native range. The negative growth response to growing‐season fire, combined with its lower implementation costs, indicates that this method warrants further investigation as a selective management tool for other problematic species in invaded grasslands.

Thatch and Mat Management in an Established Creeping Bentgrass Golf Green

Thatch is a layer of partially decomposed organic matter between green shoot tissue and the soil surface, and mat is thatch partially intermixed with topsoil. Excessive thatch–mat layering (&gt;2.54 cm) is generally detrimental to turfgrass management, and numerous techniques including various mechanical and topdressing regimes, have been attempted to reduce its severity. This factorial experiment investigated the effectiveness of combining mechanical–biological and topdressing treatments for controlling thatch–mat levels in an established USGA‐specified golf green planted with ‘A‐1’ creeping bentgrass [Agrostis stoloniferous L. var. palustris (Huds.)]. Two levels of topdressing were used, and the mechanical–biological treatments included vertical mowing at two different depths and timings, core cultivation, grooming, a biological granular supplement (Thatch‐X), and combinations of core cultivation with grooming and/or vertical mowing. Differences among the mechanical–biological treatments were detected following 2 consecutive yearly applications. Thatch–mat depth (mm) was 12 to 15% greater for Thatch‐X and topdressing alone compared with other treatments. Organic matter content (g kg−1) increased 32% for the untreated and decreased 19% for core cultivation combined with vertical mowing and grooming, whereas all other treatments maintained pre‐study levels. Compared with the untreated, surface hardness was reduced ∼9% for all treatments using core cultivation, while water infiltration rates increased 127 to 168%. Vertical mowing treatments improved water infiltration rates by 40 to 65%. Turfgrass quality was not greatly impacted by the mechanical–biological treatments as ratings ranged from 8.4 to 10.0. However, mower scalping and dry spots contributed to unacceptable or only marginally acceptable turfgrass quality (6.4–7.2) for the untreated by the end of the study. Compared with topdressing alone, ball roll distance was decreased 6% by vertical mowing 7 days after treatment (DAT) and 5 to 8% by core cultivation up to 14 DAT. Sand topdressing alone was insufficient for managing thatch–mat levels in an established creeping bentgrass golf green.

An experimental study on physical controls of an exotic plant Spartina alterniflora in Shanghai, China

Since Spartina alterniflora was introduced into the Chongming Dongtan Nature Reserve in 1995, there has been rapid expansion of this species, seriously threatening the overall biodiversity. During 2005 and 2006, a field experiment to examine physical controls on S. alterniflora, including digging and tillage, breaking of rhizomes, mowing and biological substitution with Phragmites australis, was conducted to find a means of controlling this invasive plant. The growth parameters of plant density, coverage and above-ground biomass were used to evaluate the efficiency of different treatments. The results showed that for all treatments, the plant density, coverage and above-ground biomass were significantly lower than those of the control in the first growing season. However, in the second season, the differences between the treatment and the control were not significant and there were no significant differences by the end of the second growing season. The breaking of rhizomes treatment inhibited the growth of S. alterniflora significantly in the first growing season and inhibition increased with the depth of the treatment. However, the inhibition of growth disappeared after two growing seasons and there were no significant differences among the treatments and the control. The mowing treatment significantly inhibited the growth of S. alterniflora in the first growing season. By the end of the second growing season, the growth of S. alterniflora had recovered to some extent, and only the treatments of JUN, JUL, AUG and SEP significantly inhibited its growth. The treatment of AUG might be the most suitable time for controlling via mowing. In the biological substitution treatment, the transplanted P. australis survived quite well over both growing seasons and both the plant height and fruiting percent increased considerably in the second growing season. A realistic strategy for controlling and managing the invasion of S. alterniflora in the nature reserve should involve integrating all four control measures on the basis of their intensity, frequency, timing and area. Further work on longer-term field experiments is required in order to test these conclusions further and provide useful information for the wetland management of the nature reserve.

An experimental study of the impacts of cattle on spider communities of artesian springs in South Australia

The artesian springs that are located on the edge of the Great Artesian Basin in arid South Australia support diverse assemblages of spiders. Domestic or feral stock have affected the vegetation and substrate of artesian springs, which are important water sources. The effects of stock on the spider communities of artesian springs were investigated with a descriptive survey, comparing springs with differing grazing histories, and with a field experiment that simulated the impacts of cattle presence with trampling and mowing treatments. In the survey, the abundance of spiders was associated with the dominant vegetation cover and with the history of grazing pressure. In the experiment, the abundance of web-building and ambush-hunting spiders declined following mowing and/or trampling treatments. The use of foraging guilds is likely to be a useful approach in using spider communities as bioindicators of environmental change.

Changing grass height alters foraging site selection by wintering farmland birds

Abstract Grassland is a valuable habitat for many farmland bird species, some of which have declined in Europe. Successful management of this habitat is important to benefit these species. Recent studies have suggested little correlation between food abundance and bird use in grassland; instead providing access to food may be crucial. We tested the importance of manipulating sward height (via mowing) on the distribution of wintering birds in agriculturally managed grass fields using two within-field experimental designs. In experiment 1, we investigated the effect of two treatments (mown once and control). In experiment 2, we investigated the effects of four treatments (mown once early, mown once late, mown early and late, and control). Mown plots supported higher abundances of foraging kestrels, thrushes and starlings. In contrast meadow pipits and grey herons preferred unmown plots with longer grass. These differences are probably explained by differing anti-predation strategies, increased food abundance for species that prefer above-ground invertebrates (e.g. more food for meadow pipits on longer swards) and increased food accessibility on short grass swards (e.g. for starling, thrush spp.). There were limited effects of multiple mowing events on plot use suggesting one early winter mowing treatment may suffice to create favourable conditions for species that prefer shorter swards. Providing grassland heterogeneity should benefit a range of wintering farmland birds. Although we use mowing to change grass sward height, our findings may also apply at other times of year when livestock grazing may be a more practical solution.

Optimal management of the rare Gladiolus imbricatus in Estonian coastal meadows indicated by its population structure

AbstractQuestions: What is the best grassland management regime for the threatened plant species Gladiolus imbricatus; is the stage structure of local populations a feasible indicator of the effect of changed management.Location: Coastal meadow system in southwestern Estonia. Methods: The effect of five management regimes was studied in a long‐term (three‐year) field experiment: (1) mowing in late July, (2) grazing by cattle, (3) grazing by sheep, (4) sheep grazing during the first year and mowing during subsequent years, (5) no management (control).Results: The population density increased significantly in response to the mowing treatment and to the mowing after sheep grazing treatment. The proportion of grazed plant individuals was higher in the sheep‐grazed than in the cattle‐grazed treatment. Generative and vegetative adult individuals of G. imbricatus were significantly more damaged by cattle herbivory than juveniles. All management regimes shifted the population structure towards a dynamic state where juvenile stages dominate, while the not managed control retained a regressive population structure.Conclusions: Population stage structure was a useful indicator of different management conditions, even in the case where population density did not differ. As indicated by population stage structure, the best management regime for G. imbricatus was either mowing in late July only, or alternation of grazing and mowing in different years.

Effects of Frequent Mowing on Survival and Persistence of Forbs Seeded into a Species‐Poor Grassland

Abstract Many early attempts at tallgrass prairie reconstruction failed to achieve the high species diversity of remnant prairies, and instead consist primarily of C4 grasses. We hypothesized that frequent mowing of established prairie grasses could create sufficient gaps in the aboveground and belowground environment to allow for the establishment of native forbs from seed. We studied forb seedling establishment in a 25‐year‐old prairie planting in northern Iowa that was dominated by native warm‐season grasses. In winter 1999, 23 species of native forbs were broadcast into the recently burned sod at a rate of 350 viable seeds/m2. Treatment plots were mowed weekly for either one or two growing seasons, and control plots were unmowed. Mowed plots had greater light availability than controls, especially when warm‐season grasses began to flower. Overwinter seedling mortality was 3% in mowed treatments compared to 29% in the controls. Forbs in mowed plots had significantly greater root and shoot mass than those in control plots in the first and second growing seasons but were not significantly more abundant. By the fourth growing season, however, forbs were twice as abundant in the mowed treatments. No lasting negative impacts of frequent mowing on the grass population were observed. Mowing a second year influenced species composition but did not change total seedling establishment. Experimental evidence is consistent with the idea that mowing reduced competition for light from large established grasses, allowing forb seedlings the opportunity to reach sufficient size to establish, survive, and flower in the second and subsequent years.

Optimal management of the rare Gladiolus imbricatus in Estonian coastal meadows indicated by its population structure

Questions: What is the best grassland management regime for the threatened plant species Gladiolus imbricatus; is the stage structure of local populations a feasible indicator of the effect of changed management. Location: Coastal meadow system in southwestern Estonia. Methods: The effect of five management regimes was studied in a long-term (three-year) field experiment: (1) mowing in late July, (2) grazing by cattle, (3) grazing by sheep, (4) sheep grazing during the first year and mowing during subsequent years, (5) no management (control). Results: The population density increased significantly in response to the mowing treatment and to the mowing after sheep grazing treatment. The proportion of grazed plant individuals was higher in the sheep-grazed than in the cattle grazed treatment. Generative and vegetative adult individuals of G. imbricatus were significantly more damaged by cattle herbivory than juveniles. All management regimes shifted the population structure towards a dynamic state where juvenile stages dominate, while the not managed control retained a regressive population structure. Conclusions: Population stage structure was a useful indicator of different management conditions, even in the case where population density did not differ. As indicated by population stage structure, the best management regime for G. imbricatus was either mowing in late July only, or alternation of grazing and mowing in different years.

Effects ofIrrigation and Mowingon Species Diversity of Grass and Wildflower Mixtures for the Intermountain West

Grass and wildflower mixtures can be aesthetically appealing, water-conserving, low-maintenance alternatives to conventional turfgrass. One problem with these mixtures is loss of species diversity over time. We examined the effects of irrigation and mowing on the species diversity of 3 grass and wildflower mixtures. The nonirrigated and non-mowed treatment combination maintained diversity most effectively whereas the irrigated and mowed treatment combination was least effective. Generally, when the irrigation treatment was significant (P