去叶时间对半干旱草原植物养分回收和干草生产的影响

去叶时间对半干旱草原植物养分回收和干草生产的影响 养分回收是植物养分保存的重要策略,其对环境和管理变化的响应关系到生态系统的养分循环和生产。去叶(刈割)是影响草地植物养分回收和生产的重要途径,而去叶时间的影响尚不清楚。本研究以内蒙古典型草原生态系统为对象,设置早期去叶(生物量高峰期之前)、峰期去叶(生物量高峰期)、晚期去叶(养分回收开始后)和不去叶(对照)四个处理,探讨了去叶时间对植物养分回收和生产的影响。通过测定植物物种和群落水平氮(N)和磷(P)回收特征,量化了植物N、P回收通量以及凋落物归还通量和干草输出通量,并评估了不同去叶时间处理下割草草地系统干草产量和质量。研究结果显示,峰期和晚期去叶降低植物群落N、P回收度,而早期去叶则对二者无影响;不同去叶时间处理下植物N、P回收效率相对稳定,仅晚期去叶降低N回收效率。峰期和晚期去叶降低植物群落N、P回收通量和凋落物N、P归还通量,而早期去叶并不影响这些参数。去叶时间降低植物群落养分回收通量,但未改变植物根系养分储存,说明根系养分吸收增加可补偿养分回收通量的降低。草地干草产量和质量在峰期去叶处理下最高,晚期去叶处理下最低。本研究结果为割草草地生态系统养分循环提供了新见解,通过调整刈割时间可以平衡草原的保护与生产,在植物生物量高峰期之前割草可实现保护和可持续生产的双重目标。     

Response to mowing of coastal brackish meadow plant communities along an elevational gradient

Over a six year period, 1979–1985, eight stands of till then ungrazed and unmown brackish meadow plant communities were treated by mowing once a year (August), in order to detect the response of the vegetation. The stands were distributed along a local elevation gradient, which was found to influence the composition of the vegetation through a complex-gradient, composed by unidirectional gradients in inundation, in ground water level and in Na as per cent of Ca+Mg+Na+K.
The mowing was carried out within 5 ×5 m treatment plots and the effect was indicated by quantitative analysis of the vegetation. A natural succession progressing at the locality, most distinctly manifested by expansion of Phragmites australis , was traced during the study period by means of unmown control plots.
The mowing caused increase in species diversity in all stands, mainly due to increase in evenness among the species.
The resistance of the stands to the mowing was found to differ in relation to elevation and to the initial composition of the vegetation. In upper geolittoral Festuca rubra stands the resistance was high and the mowing did not affect presence or colonisation of Phragmites . In upper-middle Festuca rubra stands resistance was lower, mainly indicated by suppression of Phragmites . Low elevation Scirpus maritimus reed beds on waterlogged soil was rather resistant, but four additional years of mowing led to a change into Agrostis stolonifera-Puccinellia maritima meadow. The resistance of low elevation Phragmites reed bed was low, as the mowing within a few years changed the reed bed into Agrostis stolonifera meadow.
The results were discussed in relation to the use of mowing as a nature conservation management tool in salt meadows.     

不同互花米草治理措施对植物与大型底栖动物的影响

治理外来入侵植物互花米草（Spartina alterniflora）对保护河口湿地鸟类栖息地及生物多样性具有重要意义。研究在崇明东滩比较了淹水刈割、反复刈割及化学除草三种措施对大面积互花米草的治理效果及其对大型底栖动物与土著植物芦苇（Phragmites australis）的影响。结果表明,反复刈割措施对互花米草生长具有一定的控制作用,对底栖动物群落的影响较小;使用化学除草剂清除互花米草的效果不明显,对底栖动物群落的影响亦不明显;淹水刈割措施能长期有效地清除互花米草,但长期淹水对底栖动物群落的影响较大,同时亦对芦苇生长造成一定负面影响。因此,淹水刈割可能是在河口生态系统治理大面积互花米草最有效的方法,但是在后续管理中需要采取一定的措施来减小对底栖动物及土著植物的影响。       

Evaluating alternative mowing regimes for conservation management of Central European mesic hay meadows: A field experiment

Conservation status of hay meadows highly depends on their management. The main goal of this study was to assess the efficiency of different mowing regimes in maintenance of plant species richness and diversity of mesic hay meadows. The field experiment was carried out on a species rich, mesic hay meadow in Western Hungary. We evaluated the effects of four alternative types of management on the plant community after 7 years of continuous treatment: (1) mowing twice a year, typical traditional management, (2) mowing once a year in May, most practised currently by local farmers, (3) mowing once a year in September, often proposed for conservation management and (4) abandonment of mowing. Traditional mowing resulted in significantly higher number and higher diversity of vascular plant species than other mowing regimes. Mowing twice a year was the only efficient way to control the spread of the invasive Solidago gigantea, and mowing in September was more successful in it than mowing in May. We conclude that the traditional mowing regime is the most suitable to maintain botanical diversity of mesic hay meadows; however, other regimes should also be considered if certain priority species are targeted by conservation.     

The biodiversity cost of reducing management intensity in species-rich grasslands: Mowing annually vs. every third year

Mowing is an important management method for species-rich semi-natural grasslands in Europe. Since mowing is costly, it is important to find a balance between mowing frequency and conservation benefits. We compared vegetation data from eleven field trials situated in southern Sweden that involved two mowing regimes, annually and every third year, as well as a no-management control. After approximately 14 years, mowing every third year showed (i) a drop in species richness and Shannon and Gini–Simpson diversity indices, (ii) an increase in woody species, and (iii) increases in tall-grown species. However, there were no apparent changes in (iv) species that were indicative of poor management, nor (v) those indicating good management. For one of the trials, data after 38 years were also evaluated. Compared with annual mowing, there were strong negative changes in the number of species in the untreated control, while the results were conflicting for mowing every third year. In conclusion, the expected loss of conservation values from reduced mowing intensity was 50–60% of the loss after abandonment. The outcomes, however, varied among the eleven sites.     

Effects of grassland intensification on Whinchats Saxicola rubetra and implications for conservation in upland habitats

Modern, intensive grassland management has led to strong declines in ground‐nesting grassland birds, and is now increasingly threatening the last remaining strongholds of the Whinchat Saxicola rubetra in the Central European uplands. In this study, we assess key threats to Whinchat populations in these uplands in order to suggest appropriate conservation measures. We compared the direct threat of early mowing as well as the indirect threat resulting from a deteriorating arthropod food source in an inner‐alpine valley. Five of our seven study sites were mown too early with respect to the chicks' fledging date. Such early mowing was particularly evident on the more intensively farmed, earlier mown valley bottoms than on the valley slopes. Arthropod abundance and biomass did not differ between valley bottoms and slopes. However, valley bottoms had a greater amount of unprofitable prey items such as flies. Breeding bird density was mainly determined by the degree of overlap between the mowing schedule and breeding phenology. These findings suggest that in upland grasslands at an early stage of intensification, early mowing is of greater importance for populations than possible negative effects of a reduced food source. We suggest that mowing is delayed until a sufficient proportion of nestlings are safely fledged.     

An agro-environmental mowing regime favors the number of inflorescences and flower-visiting insects but not ground beetles of herbaceous boundaries of arable fields

Herbaceous boundaries adjacent to arable fields can deliver ecosystem services not sufficiently provided at the field scale, as well as disservices such as increased weed pressure. The levels of services and disservices depend on the management regime implemented in these boundaries. Our study was conducted in Western France, where herbaceous boundaries of many arable fields constitute the road verge, and various mowing regimes were tested for conservation purposes. Until now, most studies of the influence of mowing regimes focused on one taxonomic group and documented contrasting results depending on the environmental context. This study aimed to compare the influence of two mowing regimes on road verges by evaluating different taxonomic groups that could potentially deliver services or disservices to adjacent arable fields. The mowing regimes used were a standard and an agro-environmental regime, the latter being characterized by one late mowing, a high mowing height and biomass removal. We monitored, during two consecutive years, seven road verges and their adjacent arable fields. Each road verge was divided into two zones of equal length, characterized by a different mowing regime. Communities of plants, flower-visiting insects and ground beetles were sampled in herbaceous boundaries and/or arable fields in the period between the mass-flowering of oilseed rape and sunflower crops. In zones where the agro-environmental mowing regime had been implemented, the average number of inflorescences and flower-visiting insects within boundaries were higher than under the standard mowing regime. However, between the two mowing regimes, no differences in weed cover within arable fields and the average number of ground beetles within boundaries and arable fields were observed. To conclude, our study suggests that in our particular environmental context, an agro-environmental mowing regime could promote pollination in adjacent arable fields without increasing weed pressure within the field.     

Rotational fallows as overwintering habitat for grassland arthropods: the case of spiders in fen meadows

Regular mowing of grassland is often necessary for plant conservation, but uncut vegetation is needed by many arthropods for overwintering. This may lead to conflicting management strategies for plant and arthropod conservation. Rotational fallows are a possible solution. They provide a spatio-temporal mosaic of mown and unmown areas that may combine benefits to both plants and arthropods. We tested if rotational fallows enhance spider overwintering in fen meadows. Rotational fallows consisted of three adjoining strips 10 m wide and 35–50 m long. Each year, one of these strips was left unmown (fallow) in an alternating manner so that each strip was mown two out of three years. Spiders were sampled during spring with emergence traps in nine pairs of currently unmown fallow strips and completely mown reference plots. Fallows significantly enhanced orb-weavers (Araneidae), sac spiders (Clubionidae) and ground spiders (Gnaphosidae). However, only 4.7% of the total variation in community composition was attributable to fallows. Community variation was larger between landscapes (34.5%) and sites (38.2%). Also β diversity was much higher between landscapes (45 species) and sites (22 species) than between fallows and mown reference plots (10 species). We conclude that the first priority for spider conservation is to preserve as many fen meadows in different landscapes as possible. Locally, rotational fallows enhance overwintering of the above-mentioned spider families, which are sensitive to mowing in other grassland types as well. Thus, rotational fallows would probably foster spider conservation in a wide range of situations. However, stronger effects can be expected from larger and/or older fallow areas.     

Living on the edge: population ecology of <Emphasis Type="Italic">Phengaris teleius</Emphasis> in Serbia

Due to their complex and interesting life cycle and alarming conservation status the Large Blue butterflies have become one of the most studied group of insects in Europe. In Serbia, however, Phengaris teleius has recently been discovered (in the far north of the country) and, since this initial finding, significant efforts have been made to map the local distribution of this species and to implement conservation measures. A mark-release-recapture study was initiated to obtain a more detailed report about population size and structure in Serbia. Results have shown that localities and patches within these localities are well connected by migration of butterflies and gave some evidence for metapopulation organisation. The total number of individuals was estimated at 15,000, which makes it one of the largest known metapopulations in Europe. Unusual for populations at the edge of the distribution range, these are characterized with large population estimates and relative stability. Compared to other areas in Europe, butterflies in Serbia start to fly 2 weeks later in the summer, probably a consequence of a late mowing regime initiated during July. Some evidence of a negative relationship between the survival of P. teleius adults and local population density was also found. With favourable management, these populations could remain stable for the foreseeable future. The preservation of large, healthy populations of P. teleius supported by a favourable management and monitoring programme along with the sustainability of individual dispersal translocation between patches should be a prime aim.     

Lawns have vertical stratification

Abstract. Vertical stratification was examined in a closely-mown lawn, at both the beginning and end of the mowing/regrowth cycle. Two treatments were examined: Undisturbed, which had been maintained as lawn for 30 yr, and Mechanically Perturbed, on which succession was occurring, after complete removal of vegetation 9.5 months previously. There was significant vertical stratification at both stages of the mowing/regrowth cycle, i.e. even immediately after mowing to a height of 3 cm, and in both treatments. There was general consistency of the vertical role of species during the cycle and between treatments. Relative vertical positions were not closely correlated with absolute leaf heights. However, in no case was the vertical position of a pair of species significantly reversed during the cycle or between treatments. No mutually cyclic vertical relations between species were seen. It is concluded that vertical stratification occurs in even the shortest communities, it starts to develop quite early in succession, and it is dependent largely on the intrinsic properties of the species, their height and (at least in lawns) their recovery from defoliation.     

Soil feedback does not explain mowing effects on vegetation structure in a semi-natural grassland

Due to its ability to create aboveground conditions that favour plant diversity, mowing is often used to preserve the high conservation value of semi-natural species-rich grasslands. However, mowing can also affect belowground conditions. By decreasing plant carbon supply to soil, mowing can suppress the activity of soil decomposers, diminish plant nutrient availability and thus create a feedback on plant growth. In this study, we first documented the effects of three-year mowing on plant community structure in a species-rich grassland. We found that mowing decreased the total areal cover of woody plants and increased the total cover of leguminous forbs. At the species level, mowing further increased the cover of two non-leguminous forbs, Prunella vulgaris and Sagina procumbens. Mowing did not affect the species number, diversity or evenness of the plant community. To study whether any of these effects could be explained by mowing-induced changes in the soil, and particularly by reduced nutrient availability, we then collected soil from different treatment plots and monitored the growth of nine plant species in these soils in a greenhouse. Plant growth did not differ between soils collected from mowed and unmowed plots, suggesting that our mowing regimes did not impose such changes in soil decomposer activity and nutrient supply that would feedback on plant growth. Moreover, each of the nine species responded equally to the different nutrient availability in different parts of the grassland, which indicates that even if mowing had reduced plant nutrient supply, this would not have led to changes in plant community structure. It appears that those changes in aboveground vegetation that we recorded after three years of mowing were purely due to the aboveground effects, such as frequent cutting of woody plants and enhanced light availability for low-growing forbs.     

High within‐winter and annual survival rates in a declining Afro‐Palaearctic migratory bird suggest that wintering conditions do not limit populations

For migratory birds, it is necessary to estimate annual and overwinter survival rates, identify factors that influence survival, and assess whether survival varies with age and sex if we are to understand population dynamics and thus inform conservation. This study is one of the first to document overwinter and annual survival from the wintering grounds of a declining Afro‐Palaearctic migrant bird, the Whinchat Saxicola rubetra. We monitored a population of marked individuals for which dispersal was low and detectability was high, allowing accurate estimates of survival. Annual survival was at least 52% and did not differ significantly across demographic groups or with habitat characteristics or residency time in the previous winter. Overwinter survival was very high and monthly survival at least 98% at some sites. Although winter residency varied spatially and with age, lower residency did not correlate with reduced annual survival, suggesting occupancy of multiple wintering sites rather than higher winter mortality of individuals with shorter residency. Our results suggest that mortality occurs primarily outside the wintering period, probably during migration, and that wintering conditions have minimal influence on survival. The similarity between survival rates for all age and sex classes when measured on the wintering grounds implies that any difference in survival with age or sex occurs only during the first migration or during the post‐fledging stage, and that selection of wintering habitat, or territory quality, makes little difference to survival in Whinchats. Our findings suggest that the wintering grounds do not limit populations as much as the migratory and breeding stages, with implications for the conservation of declining Afro‐Palaearctic migrants more widely.     

The effects of mowing and agricultural landscape management on population movements of the common quail

Aim Information on the movements of bird populations in extensive landscapes is needed to assess environmental effects and conservation strategies over appropriate temporal and spatial scales. The common quail (Coturnix coturnix) is a game bird that breeds mainly in dense cereal crops. These crops cover huge areas of the Iberian Peninsula. The aim of this work is to relate cereal mowing, which causes rapid and massive habitat loss for the common quail, to population movements of the species during its breeding season. Location Spain, southern Europe. Methods We used ring recoveries to analyse, using circular statistics, the orientation of movements by male common quails in the northern half of Spain. Forward stepwise multiple regressions were applied to correlate (1) the Julian day of cereal harvesting at 770 locations with the respective latitude, longitude and elevation, and (2) the number of hunted birds with hunting pressure, breeding densities and mean mowing date by province. Finally, data concerning the number of quails hunted at the end of the breeding season were compared by province and year using two‐way ANOVA. Results Our results show that during the breeding season in the northern half of Spain, male quails orient their movements towards higher areas, and mainly to the northern Castilian Plateau. These are the areas of Spain where cereals are harvested latest. Moreover, records show that the number of quails hunted is significantly higher in these areas than in other areas of the country, independently of hunting pressure and breeding densities, and it is extremely high in the northern Castilian Plateau. Main conclusions Cereal mowing combined with some Spanish geographical characteristics acts as a funnel, forcing quail populations to concentrate in certain areas of Spain at the end of the breeding season. This implies that the number of quails hunted in these areas may be high, and that they therefore constitute priority conservation areas.     

Banding data reveal bias in age‐class sampling of songbirds during spring migration

Population age structure and vital statistics are important for understanding songbird demography and for developing conservation strategies. Field‐based estimates of survival rates based on mark–recapture methods are conservative because they are constrained by problems associated with detection probabilities and emigration. However, data collected at bird‐banding stations during spring and fall migration can potentially provide useful demographic information. I used banding data collected over a 6‐yr period (2005–2010) at Long Point Bird Observatory on the north shore of Lake Erie in Ontario, Canada, and Powdermill Avian Research Center in southeastern Pennsylvania, U.S.A., to determine if banding records could be used to estimate vital statistics for several species of songbirds. As reported in previous studies, I found the proportion of juveniles captured during fall migration to be unrealistically high to be representative of true proportions, especially at Long Point. The proportion of juvenile songbirds captured remained implausibly high during spring migration, with related estimates of longevity and generation time implausibly low and of fecundity implausibly high. Based on apparent adult survival estimates from the literature that suggest an average age structure for songbirds of >55% adults and <45% juveniles, I found that capture rates for juveniles during spring migration were at least twice as high as that for adults. A slower pace of spring migration by juveniles likely accounts for some of this bias. Because the data cannot be assumed to represent unbiased samples with respect to the age structure of populations, my results indicate that banding data collected at bird‐banding stations during migration are not suitable for use in demographic studies.     

Old and unmowed saltmarsh patches provide attractive habitats for breeding passerines

Although the conservation stakes of saltmarshes are widely documented, these areas are still subjected to strong anthropic pressures, including land reclamation, leading to their conversion into arable lands, and agricultural exploitation (mainly cattle grazing and mowing), which modifies their floral and faunal composition. Through the example of one of the largest French saltmarshes, we first assessed how the age of the saltmarsh patches and the mowing intensity determined the spatial distribution of the different saltmarsh habitats. We then tested how the five commonest breeding passerines were distributed in accordance with the mowing activity and the distribution of these habitats. We found that the oldest and the unmowed patches promote the development of habitats dominated by Elymus pungens and Atriplex portulacoides, and also host the highest abundance of four of the five bird species studied. In the current context of an intense artificialization of the littoral area, this study highlights the importance of maintaining the oldest and the least human-impacted patches of natural habitats to conserve their associated biodiversity.     

Controlling invasive Arrhenatherum elatius and promoting native prairie grasses through mowing

Abstract. Control of invasive plants is a key element of conservation and restoration efforts. We report results from a five‐year field experiment in western Oregon, USA that evaluates the effects of different mowing regimes on the non‐native and invasive perennial grass Arrhenatherum elatius, the native perennial prairie grasses Danthonia californica and Festuca roemeri, and groups of other native and non‐native grasses and forbs. Eight treatments were designed to test hypotheses about the role of mowing height and time of application on the plant community. Differences among treatments emerged only after two or three years of treatment. This delay in response reinforces the need for long‐term studies. Annual mowing was most effective at reducing Arrhenatherum cover and flowering when applied in late spring or early summer, the time of Arrhenatherum flowering and expected maximum above‐ground allocation. Double mowing and mowing at 15 cm were more effective in reducing Arrhenatherum cover than were single mowing and mowing at 50 cm. All treatments increased the cover and flowering of Danthonia. Statistical model analysis showed that increases in cover and flowering of the native grass Danthonia were caused by its release from suppression by Arrhenatherum. Fouryears of the most effective treatment, mowing at 15 cm in late spring, converted an Arrhenatherum‐dominated site to a prairie dominated by native grasses. This is one of the few documented cases of pest plant control causing an increase in native plant abundance. These results show that mowing, properly applied, can be an effective tool for restoring degraded, Arrhenatherum‐dormnated prairies.     

Mowing management and density dependence in meadow passerine hatching success

Capsule Improving habitat quality through late or intermittent mowing may increase passerine population density without reducing reproductive success.

Aim To describe the relationship between passerine territory density (TD) and Whinchat Saxicola rubetra and Yellow Wagtail Motacilla flava hatching success, under different management regimes.

Methods TD was defined by the Territory Mapping method in nine sites selected in five French flood plains, in four intermittently mown meadows in Russia and in four additional French sites where mowing was partially postponed. Hatching success was assessed by the observation of prey carrying. Generalized Linear Mixed Models were used to analyse the influence on hatching rates of mowing management, early mowing and TD. Linear Mixed Models were used to study the effect of mowing management on TD.

Results In French early mown meadows, TD affected reproductive success. Higher hatching rates and TD were observed in Russia. Similar results in French study sites with postponed mowing confirmed the influence of mowing management on carrying capacity.

Conclusion In west-European grassland systems, late or intermittently mown patches within or at the edge of meadow areas, with potentially improved invertebrate-prey availability, should help to sustain bird demography and improve the efficiency of current conservation programmes.     

Frequent mowing is better than grazing for the conservation value of lowland tussock grasssland at Pontville,Tasmania

Abstract The effects of an unusual high frequency mowing regime, which involved the removal of slash, were compared to moderate grazing through the method of paired quadrats across a fenceline, which was orthogonal to a weak environmental gradient. The mown plots proved superior in their conservation characteristics to the moderately grazed plots. The mowing regime produced greater cover of rare or threatened species, greater native cover and lesser exotic grass cover. It thus presents an opportunity for maintaining or improving the condition of previously grazed remnants in reserves without resorting to the use of stock or fire for biomass reduction.     

Plant community assembly in suburban vacant lots depends on earthmoving legacy,habitat connectivity,and current mowing frequency

In suburban regions, vacant lots potentially offer significant opportunities for biodiversity conservation. Recently, in Japan, due to an economic recession, some previously developed lands have become vacant. Little is known, however, about the legacy of earlier earthmoving, which involves topsoil removal and ground leveling before residential construction, on plant community composition in such vacant lots. To understand (dis)assembly processes in vacant lots, we studied 24 grasslands in a suburban region in Japan: 12 grasslands that had experienced earthmoving and 12 that had not. We surveyed plant community composition and species richness, and clarified compositional turnover (replacement of species) and nestedness (nonrandom species loss) by distance‐based β‐diversities, which were summarized by PCoA analysis. We used piecewise structural equation modeling to examine the effects of soil properties, mowing frequency, past and present habitat connectivities on compositional changes. As a result, past earthmoving, mowing frequency, soil properties, and past habitat connectivity were found to be the drivers of compositional turnover. In particular, we found legacy effects of earthmoving: earthmoving promoted turnover from native grassland species to weeds in arable lands or roadside by altering soil properties. Mowing frequency also promoted the same turnover, implying that extensive rather than intensive mowing can modify the negative legacy effects and maintain grassland species. Decrease in present habitat connectivity marginally enhanced nonrandom loss of native grassland species (nestedness). Present habitat connectivity had a positive effect on species richness, highlighting the important roles of contemporary dispersal. Our study demonstrates that community assembly is a result of multiple processes differing in spatial and temporal scales. We suggest that extensive mowing at local scale, as well as giving a high conservation priority to grasslands with high habitat connectivity at regional scale, is the promising actions to maintain endangered native grassland species in suburban landscapes with negative legacy effects of earthmoving.     

刈割制度对呼伦贝尔草原群落特征及牧草质量的影响

为确定呼伦贝尔草原高效生产和可持续利用的最佳刈割制度,于2019—2021年在呼伦贝尔草原开展刈割时间(7月31日、8月10日、8月20日、8月30日、9月9日)、留茬高度(3、9、15 cm)及两者交互作用对草原群落特征、牧草产量和品质影响的研究。结果表明: 较晚时间刈割和低留茬刈割会降低翌年群落高度和盖度;低留茬刈割降低翌年地上部分生物量,但刈割时间对其影响不显著。禾草、莎草相对生物量随刈割时间的延迟表现出先增加后减少的趋势,杂类草则与之相反,而豆科植物无明显变化。低留茬刈割在当年能够获得高的干草产量,但翌年的干草产量显著下降;8月30日,留茬3 cm刈割时干草产量达到最高值(469 g·m^-2),高于最低值361.5%。牧草品质中粗蛋白含量在8月30日刈割时亦达到峰值,高于最低值约6.5%,且在高留茬刈割下含量更高;酸、中性洗涤纤维含量随刈割时间延迟逐渐升高,9月9日刈割高于7月31日8.0%、5.9%,并且随留茬高度增加而降低。呼伦贝尔草原刈割制度设置为留茬高度9 cm左右、8月20—30日刈割为最佳,但需更长期的刈割试验观测才能得到更可靠、更客观的结论。