Effect of cattle breeding on habitat use of Pampas deer Ozotoceros bezoarticus celer in semiarid grasslands of San Luis, Argentina

The largest population of the Argentinean Pampas deer Ozotoceros bezoarticus celer is found in the semiarid grasslands of the San Luis province. Despite relatively high deer numbers in the region, there has been concern that expansion of farming practices could displace the species. Since the 1990’s, cattle breeding has intensified especially as a result of the replacement of natural grassland with South African digit grass (Digitaria eriantha) and African lovegrass (Eragrostis curvula). In this study, we studied how deer in “El Centenario” ranch used available habitat types, especially to assess whether it preferentially used natural over exotic pastures. We employed 8 fixed line transects to record deer numbers and habitat use during the dry season, early rainy and late rainy seasons. We estimated a mean population size of 731 ± 121 individuals, a density of 1.95 ± 0.25 deer/km². Our results also showed that deer did not appear to select natural pastures over exotic ones, though D. eriantha grasslands with cattle were used less during the late rainy season. Grazed pastures with D. eriantha without cattle were used significantly more during all time periods. Our results therefore suggest that Pampas deer are not shifted by exotic pastures but we caution that it is important to manage these habitats sustainably (e.g. cattle load adjusted to grassland nutritional supply, rotational crops with parcel rest period), to ensure the conservation of the species within agricultural areas.     

Seed germination of five mountain steppe species of Central Asia

This paper presents data on the germination traits of five perennials (Allium polyrrhizum, Agropyron cristatum, Arenaria meyeri, Artemisia frigida and Artemisia santolinifolia) widespread in the mountain steppes of southern Mongolia. Germination and seed viability were assessed at three alternate temperatures (8/4 °C, 20/10 °C, 32/20 °C), three levels of osmotic stress (deionized water; −0.5 MPa, −1 MPa Mannitol solution), and under conditions of alternate light/darkness versus complete darkness. The results of a factorial ANOVA with treatments and species as main effects showed that all five species germinated best at higher temperatures, with only Agropyron cristatum showing some seed mortality. Osmotic stress reduced seed viability and total germination in all five species. Darkness had no influence on viability, but positively affected seed germination of Allium polyrrhizum and Agropyron cristatum. We therefore conclude that, in the field, germination of all five species is mainly controlled by ambient temperatures and water availability, both of which drop towards the end of summer when dispersal takes place and effectively delay seedling recruitment until the next vegetation period.     

The food habits of goats on rangelands with different amounts of fourwing saltbush (Atriplex canescens) cover

Esophageally fistulated goats were released in a microphyll desert scrub habitat with 14.6% or 46.2% aerial cover of Atriplex canescens (induced by removal of all shrubs except A. canescens, with livestock grazing exclusion for 10 years) to determine the seasonal forage species selected by the goats. The shrub removal strongly influenced the goats’ feeding habits. The goats grazing the Atriplex-dominated site consumed 4.5 times more A. canescens than the goats on the untreated (control) pasture during all seasons. Shrubs were used heavily during all seasons by goats in both pastures, with higher percentages (75.5–82.8%) in the diets of goats grazing the control pasture than in the diets of goats grazing the Atriplex-dominated area (62.5–68.5%). No differences were found between seasons. The goats in the Atriplex-dominated pasture ate more grass than the goats grazing the control area and used more perennial graminoids during the summer (15.0%) and spring (18.3%) than the goats on the control area (6.0–7.0%). Forbs were an important component of diets. It was concluded that the successful revegetation of the treated pasture affected the goats’ feeding strategy, with an increase in the use of A. canescens, forbs and grasses in all seasons.     

Disentangling Fabiana imbricata (Solanaceae) regeneration: The importance of disturbance and rainfall

In Mediterranean ecosystems, fire influences plant population dynamics and changes plant community structure by affecting germination and establishment of seeder shrubs. Fabiana imbricata is a long-lived seeder shrub with a broad distribution in South America. In Northwestern Patagonia grasslands there are many records of F. imbricata recruitment after fires. We hypothesized that recruitment is promoted by: 1) soil erosion that exposes deeply buried seeds; 2) direct fire effects such as heat that could break seed dormancy; 3) indirect fire effects (i.e. increase of light availability and elimination of allelopathic substances) and 4) water availability in spring. In field conditions, we tested the effects of shading and soil disturbance on F. imbricata recruitment and seed availability and distribution in the soil profile. Under controlled conditions, we investigated the influence of leaf leachate, light, heat and water on seed germination and seedling emergence. Seed germination was inhibited by leachate, and seedling emergence was inhibited by seed heated to 80 °C and 120° for 5 min. F. imbricata seedlings only emerged in germination treatments that simulated wet and very wet spring conditions. Fire and postfire wind that favor seed exposure, combined with high precipitation early in the growing season, would be necessary for successful shrub recruitment. When F. imbricata shrubland colonizes the grassland, it strongly modifies local vegetation structure, reduces species richness and increases fuel loads. F. imbricata is a key species in the ecosystem specially related to fire regime. Information on the postfire regeneration of this species would provide valuable knowledge of the changes in biomass accumulation in a fire-prone Mediterranean ecosystem.     

Plant communities of central Tibetan pastures in the Alpine Steppe/Kobresia pygmaea ecotone

Eleven plant communities of the central Tibetan ecotone (31°20′-33°00′N/89°00′-92°10′E) between the Kobresia pygmaea grazing pastures of the eastern highlands and the open short grass steppe with cushion plants (“Alpine Steppe”) of the north-western highlands have been described on the basis of 189 plot-based floristically complete vegetation records. In parallel, remote sensing techniques distinguish four main land-use cover types. Our hypotheses are: (1) The plant communities of the central Tibetan highlands are grazing-adapted and resilient to degradation. (2) In contrast to grazing resilient plant functional types, the turf cover of the K. pygmaea pastures and the Kobresia schoenoides wetlands is degradable through desiccation, periglacial processes, soil-dwelling small mammals and livestock. Five grazing-related plant functional traits are introduced. Grazing tolerance is the prevalent functional type. Species with no specific protection against grazing make up not more than 6% of the total cover. Unpalatable plants cover up to 8%. Only the azonal K. schoenoides swamps - the indispensable winter grazing reserve - have been widely degraded and depleted by 75%, being replaced by Carex sagaensis grazing pastures. It can be foreseen that governmental policy of sedentarisation of nomads will lead to reduced grazing mobility and degradation of winter grazing reserves.     

Environmental control of seed dormancy and germination in the short-lived Olimarabidopsis pumila (Brassicaceae)

The purpose of our study was to better understand seed germination ecology of the spring annual short-lived Olimarabidopsis pumila, which grows in the Gurbantonggut Desert, China. Seeds underwent after-ripening at 4, 20 ± 2 (room temperature) and 30 °C. After dormancy was broken, germination capacity was a function of temperature and presence of light. For the temperature range studied (4–30 °C), germination capacity was significantly higher between 15 and 25 °C than at temperatures above or below them. Alternating temperatures of 20/10, 25/10 and 25/15 °C were favorable for germination. Although GA₃ did promote dark germination of seeds, GA₃ did not replace light for germination. Seeds germinated to >75% if light exposure time was over 8 h and temperature and moisture conditions were favorable. Seeds were able to germinate at relatively low water potentials (83% at ?0.41 MPa), but decreasing water potentials produced detrimental effects on germination percentage and rate. Thus, dormancy characteristics and germination behavior of O. pumila seeds ensure that germination occurs in the desert only when soil moisture conditions are favorable for seedling establishment and survival.     

Effects of grazing and climate change on sandy grassland ecosystems in Inner Mongolia

To understand the effects of grazing activities and climate change on sandy grassland ecosystems in northern China, a livestock field grazing and enclosure experiment was conducted from 1992 to 2006 in Horqin Sand Land, Inner Mongolia. The results showed that sustained heavy grazing resulted in serious degradation of the vegetation; moderate grazing can maintain vegetation stabilization; and light grazing can promote rapid restoration of degraded vegetation. The livestock productivity was the highest in the moderate grazing grassland, and sustained heavy grazing resulted in rapid decrease of the livestock productivity. Heavy grazing can cause a retrogressive succession of grassland vegetation, whereas moderate and light grazing may promote progressive succession of plant species. The effects of changing climate on succession processes were not significant in the short term; a warm-humid climate is favorable to restoration of degraded vegetation, whereas a sustained warm-drought climate may result in degradation of grassland vegetation. Heavy livestock grazing should be stopped for the sustainable use of grassland; the proper grazing intensity for sandy grassland is two to three sheep or sheep equivalents per hectare in Inner Mongolia.     

Grazing itineraries and forage selection of goats in the Al Jabal al Akhdar mountain range of northern Oman

In view of the repeatedly reported overstocking of the high-altitude pastures on Al Jabal al Akhdar, northern Oman, plant species abundance, cover and frequency, and herbaceous mass yield were studied in ungrazed versus heavily grazed areas of this mountain range. In addition, plant species selection by goats along a gradient of 1000–2000 m and spatial extent of pasture areas were investigated after abundant rainfall and a subsequent 6-months dry spell by means of manual observation and GPS/GIS tools.The substantially higher species diversity and herbaceous mass yield in the ungrazed area illustrate the production potential of these mountain pastures or, respectively, the biodiversity and productivity loss resulting from continuous grazing. The concentration of goats' selection on only a dozen herbaceous and ligneous species favours pasture encroachment with poisonous shrubs such as Nerium mascatense in the lower and Dodonaea viscosa in the higher altitudes. Given the spatially limited extent of pasture areas, these are exposed to high stocking rates. Therefore, grazing and feeding schemes need to be developed which reduce livestock pressure on the pastures, taking into account local property rights, herding skills and the recovery potential of the vegetation, which heavily depends on unpredictable rainfall events.     

Effects of land conversion on the regeneration of Pachycereus pecten-aboriginum and its consequences on the population dynamics in northwestern Mexico

Pachycereus pecten-aboriginum is a columnar cactus currently threatened by the conversion of natural vegetation to buffelgrass pasture (Pennisetum ciliare) in Sonora, Mexico. However, knowledge about its population dynamics is extremely poor, particularly in response to disturbance caused by pasture conversion. We set up experiments to evaluate seed removal, germination, seedling survival and compared demographic patterns on permanent plots from natural vegetation and pasture. Our experiments on regeneration show that seedlings were unable to establish in pasture because of high levels of mortality due to soil drying and cattle trampling. The population growth rate (λ) was 1.060 and 1.086 for the 2006–2007 and 2007–2008 periods, respectively, in the native thornscrub vegetation. The slight increase in λ in 2007–2008 was a result of increased fecundity and seedling survival. The highest elasticity values correspond to the survival of large/old individuals. Using the average of both matrices, we obtained a mean matrix to perform numerical analyses simulating demographic variation to project the population behavior under buffelgrass pasture conditions. The numerical simulations suggest a decreasing population only when adult survival probabilities were affected. Given these limitations for population growth, our data suggest that adult populations that persist on pastures will be driven into local extinction.     

Modeling the optimal grazing regime of Acacia victoriae silvopasture in the Northern Negev,Israel

Silvopasture, the planting of suitable tree species in pastures, can improve the sustainability and productivity especially in dry rangelands. While recent studies provide information on the effects of different tree compositions on biological productivity, water and soil protection, additional parameters such as fodder production by the trees or the impact of silvopasture on the grazing potential themselves have rarely been addressed. We determined fodder production in Acacia victoriae woodland and savanna by measuring annual vegetation and tree biomass growth. We developed mathematical models for calculating the vegetative biomass available for grazing. In order to get accurate estimation for the grazing capacity, we differentiated between the grazing and the browsing fodder availability, and adapted the model to the most abundant grazers in the Negev, goats and sheep. Grazing capacity for sheep and goats was twice bigger in A. victoriae woodland than in the adjacent sustainably managed shrubland and four times higher than in degraded shrubland. The mathematical model presented in this paper can be applied in order to plan and realize high yielding and sustainable silvopasture in arid environments resistant to degradation and desertification while providing adequate fodder reserves during drought years.     

Morphological and reproductive response of Caragana microphylla to different stocking rates

Understanding the effect on host plants of defending against herbivores is important in grazing ecology and grassland management. In this study, the morphological and reproductive responses of Caragana microphylla Lam. to grazing sheep were investigated using a 15-year grazing experiment with six stocking rates in the Inner Mongolia steppe of China. Plant height, rachis length, leaflet size, and number of pods decreased significantly, whereas spine density and length increased significantly with increased stocking rate. Significant negative correlations were observed between production of vegetative and reproductive organs and defensive organs, indicating that it is costly for C. microphylla to defend against herbivores and that morphological miniaturization and a tradeoff between production and defense were main responses of C. microphylla to herbivores.     

Seed biology of Australian arid zone species: Germination of 18 species used for rehabilitation

Revegetation of disturbed land, particularly in arid environments, is often hindered by low seedling establishment. Information on seed biology and germination cues of keystone species is lacking, particularly in arid Australia; a major zone for mining developments. This study investigated seed characteristics and germination of 18 common species required for rehabilitation of disturbed areas at Shark Bay Salt in the Shark Bay World Heritage Area, Western Australia. Untreated seeds of seven species (Aphanopetalum clematideum, Atriplex bunburyana, Austrostipa elegantissima, Melaleuca cardiophylla, Pembertonia latisquamea, Rhagodia baccata, Salsola tragus) exhibited high germination percentages. Seeds of two species (Acacia tetragonophylla, Stylobasium spathulatum) had low imbibition, which increased with hot-water treatment, hence require scarification for germination. Gibberellic acid, smoke water and karrikinolide (a butenolide isolated from smoke) substantially increased germination percentages of three species (Anthocercis littorea, Diplolaena grandiflora, Solanum orbiculatum). Seeds of the remaining six species (Dioscorea hastifolia, Eremophila oldfieldii, Nitraria billardierei, Ptilotus exaltatus, Thryptomene baeckeacea, Zygophyllum fruticulosum) had low germination percentages regardless of treatment. Most species germinated equally well at 26/13 °C and 33/18 °C, however seven species had improved performance at 26/13 °C. This study is significant to land managers and conservation agencies with an interest in optimising germination of arid zone seeds for restoration.     

Effects of grazing intensity on soil organic carbon of rangelands in Xilin Gol League,Inner Mongolia,China

Changes in soil organic carbon (SOC) in rangelands has been extensively investigated. Grazing in outlying rangeland areas has caused severe impacts on ecosystem functions. To reveal the effects of grazing on SOC, we evaluated the grassland in Xilin Gol League, Inner Mongolia, China. Grazing intensity was determined by using two image sets of vegetation index with normalized differences in grazing periods (July 12th and 28th). The range of variation in vegetation index was then used to measure the grazing intensity. The SOC storage and density were obtained by conducting experiments on field soil samples. Results showed that 1) the grazing intensity in Xilin Gol League declined gradually from west to east; by contrast, the spatial distribution of SOC density increased gradually. 2) As grazing intensity increased, the carbon storage of rangeland decreased evidently. Minimum carbon storage was observed in grasslands classified under extreme overgrazing; by comparison, maximum values were found in areas classified under light overgrazing to moderate grazing. 3) The estimated soil carbon storage was 8.48 × 10¹¹ kg, and the average carbon density was 4.08 kg/m². Our research demonstrated that grazing intensity likely affects soil carbon. Moderate grazing is an optimum strategy to maintain carbon storage and ensure sustainable grassland utilization.     

Effects of Grazing on the Grassland Vegetation Community Characteristics in Inner Mongolia

The continuous increase of livestock production in Inner Mongolia has caused severe degradation of the grassland ecosystems in recent years. Previous grazing experiments have shown a wide range of vegetation responses between the biome types on a global scale, but there is still a lack of sufficient studies to discern the relative responses of a given biome type. We conducted a meta-analysis of vegetation coverage (VC), plant density (PD), total biomass (TB), above-ground biomass (AGB), under-ground biomass (UGB) and Shannon-Weaver Index (SI) in different grassland types in Inner Mongolia obtained under conditions of different grazing intensities and durations. The results showed that grazing decreased VC, TB, AGB, UGB, and PD significantly. Compared to the global and national average values, the negative effects of grazing to steppe biomass in Inner Mongolia were higher than that on the global scale, while less pronounced than that in China. TB of the meadow steppe in Inner Mongolia increased by 40% under moderate grazing intensity and duration because of compensatory growth. SI of the desert and meadow steppe showed negative linear relationships with the grazing intensity in Inner Mongolia. The percentage changes in AGB, PD, and SI to grazing showed quadratic relationships with the mean annual temperature of the experimental year. With increasing mean annual precipitation, the negative effects of grazing on UGB and SI first decreased and then increased, with that of VC and grazing showing a cubic relationship.     

Moderate water supply and partial sand burial increase relative growth rate of two Artemisia species in an inland sandy land

Artemisia ordosica and Artemisia sphaerocephala seedlings were buried in sand to depths of 0, 0.25, 0.5, 0.75, 1 and 1.25 times the seedling height (H) and supplied with 2.5, 5.0, 7.5 and 10.0 mm of water every three days. For A. ordosica, the highest relative growth rate (RGR) and seedling height were achieved with 75 mm/month water supply and 0.5 H burial at 50 days, and the RGR decreased with 100 mm/month water supply. For A. sphaerocephala, the highest RGR was reached with 50 mm/month water supply and 0.5 H burial, but plants from this species had the greatest seedling height with 25 mm/month water supply and 0.75 H burial. A. ordosica and A. sphaerocephala have different proportions of their biomass in roots and shoots and thus are adapted to sandy environments in different ways. Partial sand burial significantly increased the RGR and growth height of the two Artemisia species, but complete burial lead to seedling death. Differences in the growth response to burial and moisture levels help explain why A. sphaerocephala is primarily found on drifting dunes and A. ordosica on semi-fixed and fixed dunes.     

Heliotropium europaeum only germinates following sufficient rainfall to allow reproduction

Regions with Mediterranean climates are seasonally arid and provide a niche for ephemeral species which germinate following discrete and variable rainfall during summer. These species must be able to detect when conditions are suitable for completion of their life cycle. Common heliotrope (Heliotropium europaeum) is one such species. It is considered a weed in its naturalised habitat in southern Australia as it uses resources that could be used by ensuing crops, and is toxic to livestock.We examined common heliotrope's germination responses to temperature and water potential, the effect of simulated rainfall on seedling emergence and plant growth in lysimeters.Fresh seeds of common heliotrope have relatively high optimum temperatures and water potentials for germination (around 35 °C and 0 MPa). Germination percentage of seeds extracted from the soil seed bank varies seasonally. In the soil types and climate of the study area, 24.2 mm is the minimum amount of rainfall resulting in emergence. Evapotranspiration required to reach minimal reproductive output was 19.4 mm.Common heliotrope's germination requirements have been selected to ensure that it will only germinate after sufficient rainfall to allow reproductive output. This is the mechanism through which common heliotrope detects its temporal niche.     

蒙古高原草地利用特征及其国别差异

内蒙古草原是蒙古高原草原带的南部组成部分,是我国北方重要的生态屏障,草原生态修复任务重、压力大。本文以蒙古高原典型草原乌珠穆沁—温都尔汗样带为例,以1988—2016年5期TM数据为信息源,获取2016年样带草地利用信息基础上,按国别和年限对样带草地利用特征进行分析,揭示草地主要干扰因素,探寻有效的修复途径和可借鉴的国际经验。研究发现：① 草地面积占样带95.05%,均匀覆盖于整个样带;其他用地类型占比均不大,但分布相对集中,其中耕地集中于样带西北部蒙古国段,工矿用地、沙地、盐碱地集中于样带东南部内蒙古段。② 1988—2016年样带耕地面积减幅最大,为35.71%,集中位于蒙古国段;草地、水域面积逐年减少,在中国境内、境外变化趋势相同,但内蒙古段草地减幅大于蒙古国段且多转为未利用地;工矿用地面积增幅最大,为初期的近367倍,集中分布于内蒙古段;盐碱地、沙地面积逐年增加,在中国境内、境外的变化幅度相当。③ 草地是高原主要土地利用类型,放牧是草地主要利用方式,开矿是除放牧以外中国草地的主要干扰因子,蒙古国则为垦殖,内蒙古的草地干扰远大于蒙古国。草地退化与干旱化是蒙古高原面临的主要生态环境问题,在中国境内尤为突出。     

Seed germination of wild,in situ-managed,and cultivated populations of columnar cacti in the Tehuacán-Cuicatlán Valley,Mexico

Seed germination was compared among wild, in situ-managed (wild plants let standing in areas cleared for agriculture), and cultivated populations of the columnar cacti Stenocereus pruinosus, Polaskia chichipe, Myrtillocactus schenckii, and Polaskia chende, species representing a gradient from higher to lower management intensity, respectively. We hypothesized that seeds from cultivated populations have higher water requirements to germinate than seeds of other populations, and that such difference is stronger in species more intensely managed. Germination was evaluated under water potential treatments at 0.0, ?0.2, and ?0.4 MPa. Interspecific differences were identified; germination rates markedly decreased in S. pruinosus and P. chichipe as water potential reduced. M. schenckii seeds germinated better at ?0.2 MPa, and seeds of P. chende in all treatments. Seed germination of wild and cultivated populations was similar in all cases and, therefore, at the population level domestication does not appear to have influenced variations in germination of the studied cacti species. However, experiments to test whether germination of seeds from plants with clear signs of domestication differs with seeds from other plants and their differential germination and seedling survival in wild, in situ-managed and cultivated environments could help to precise the influence of domestication on these plants.     

An assessment of revegetation treatments following removal of invasive Pennisetum ciliare (buffelgrass)

In semi-arid regions of North America and Australia, Pennisetum ciliare (L.) Link (syn. Cenchrus ciliaris; buffelgrass) is highly invasive and has the potential to introduce fire to fire-intolerant ecosystems. Major efforts to remove P. ciliare continue and it is essential that P. ciliare be prevented from recolonizing. This study investigated potential methods to revegetate with native herbaceous plants: sowing seeds; sowing seeds and mulching; sowing seeds and transplanting seedlings; and relying on natural revegetation from the seedbank. The treatments were applied in 2009 and 2010 at sites in the Sonoran Desert which had undergone P. ciliare removal. Monsoon precipitation was below average each year and seedling emergence and establishment rates were low. There are indications that soil disturbance associated with planting seedlings promoted P. ciliare emergence and increased mortality of brittlebush (Encelia farinosa A. Gray ex Torr.), a common native perennial forb. Addition of mulch may have promoted P. ciliare over native grasses, and seeding had no effect. We did not find competition between herbaceous seedlings. Rather, native and exotic grass seedling densities were positively correlated across sites. Under prevailing conditions, low precipitation appeared to limit herbaceous plant establishment and none of the treatments reduced P. ciliare abundance.     

Effects of seasonal grazing,drought, fire,and carbon enrichment on soil microarthropods in a desert grassland

This study was designed to test hypotheses about the combined effects of short-term, seasonal grazing with seasonal drought, fire, and carbon enrichment on soil microarthropod communities in a Chihuahuan Desert grassland. The study was conducted in eighteen 0.5 ha plots following three consecutive years of treatment: six plots intensively grazed in summer, six in winter, and six not grazed. There was no difference in perennial grass cover on the summer-grazed and winter-grazed plots. Intensive seasonal grazing had no effect on the abundance and community composition of soil microarthropods. Within each plot there were six subplots: summer rain-out, winter rain-out, burned, glucose amendment, rain-out control and burn-glucose control. Fire and carbon enrichment had no significant effect on soil microarthropod abundance or community composition. The average number of microarthropods ranged from 8915 ± 1422 m⁻² in the ungrazed, unburned plots to 7175 ± 1232 m⁻² in the winter-grazed, unburned plots. Microarthropod densities in the glucose-amended plots were 8917 ± 4902 m⁻² in the winter-grazed plots and 10,731 ± 863 m⁻² in the glucose-amended, summer-grazed subplots.The prostigamatid mite, Tydeus sp., was the most abundant microarthropod taxon in all treatment plots.