The adaptive significance of differences of root morphology, anatomy and physiology from three ecotypes of reed (Phragmites communis Trin.)

Reeds are widely distributed in drought and high salt conditions of northwestern China.Leaf epidermal micromorphology,anatomy,chloroplast ultrastructure and physio-chemical characteristics due to long-term adaptation in the natural habitats of common reed (Phragmites communis Trin.) contrasted considerably among three different ecotypes:dune reed (DR),Gobi salt reed (GSR) and swamp reed (SR).The main objective of the present study is to determine the adapting characteristics of morphology,anatomy and physiological responses of thin roots in DR,GSR and SR.The results show that root length density was higher in SR and few root hairs were observed in DR.Cross-section anatomical features show that each ecotype has an endodermis and exodermis,while cortex thickness and proportion of root cortical aerenchyma and stele in root structure varied among the three ecotypes.The stele and xylem share a larger area in DR compared to GSR and SR.GSR has a large proportion of the cortex with radialized distribution of aerenchyma cells spacing,and the cortex has a peripheral,mechanically stiff ring in the exodermis.SEM and TEM microscope images show that GSR has a sclerenchyma ring with high lignification in the exodermis.The physio-chemical parameters show that GSR had a higher level of stress tolerance than DR.These findings indicate that developed water-absorbing tissues were largely distributed in the root structure of DR,and a main framework with supporting function spacing with aerenchyma was dominant in GSR in the long term adaptation to their natural habitats,respectively.     

Amelioration of soil fertility by woody perennials in cropping fields: evaluation of three tree species in the semi-arid zone of Nigeria

Soil was sampled from cropping fields in radial patterns from beneathAcacia albida, Parkia bigloboza(Jacq.) Benth. andEucalyptus camaldulensisDehnh. near Zaria, Nigeria. Results of analysis show a significant coarsening of soil texture and a decrease in organic matter and cation exchange capacity with increasing distance from all three tree species at a depth of 0–15 cm. Concentrations of nitrogen and some exchangeable cations decreased significantly with increasing distance from beneath acacia and parkia, and soil pH decreased with increasing distance from eucalyptus. The implication of the results for land management are discussed in relation to increasing productivity and soil use sustainability.     

Root tensile strength relationships and their slope stability implications of three shrub species in the Northern Apennines (Italy)

The role of root strength is important in stabilising steep hillslopes which are seasonally affected by storm-induced shallow landslides. In the Italian Apennines, steep (25–40°) slopes underlain by mudstone are generally stable if they are covered by shrubs whose roots anchor into the soil mantle. To quantify the mechanical reinforcement of roots to soil, the root tensile breaking force and the root tensile strength of three autochthonous shrub species commonly growing on stiff clay soils of the Northern Italian Apennines, Rosa canina (L.), Inula viscosa (L.) and Spartium junceum (L.), were measured by means of field and laboratory tests. For each test approximately 150 root specimens were used. The tensile force increases with increasing root diameter following a second-order polynomial regression curve. The tensile strength decreases with increasing root diameter following a power law curve. The field in situ tensile force required to break a root is always smaller than that obtained from laboratory tests for the same root diameter, although their difference becomes negligible if the root diameter is smaller than 5 mm. The influence of root tensile strength on soil shear strength was verified based on the infinite slope stability model. The root reinforcement was calculated using the number and mean diameter of roots. The factor of safety was calculated for three different soil thickness values (0.1, 0.3, and 0.6 m) and topographic slopes between 10° and 45°. The factor of safety for the combination of 0.6 m soil thickness, slopes smaller than 30°, and vegetation of I. viscosa (L.) or S. junceum (L.) is always larger than 1. If a slope is steeper, the factor of safety may be smaller than 1 for I. viscosa (L.), although it is still larger than 1 for S. junceum (L.). In the stiff clayey areas of the Northern Italian Apennines, I. viscosa (L.) mainly colonizes fan/cone/taluses and stabilises these zones up to a topographic gradient < 30° for a soil 0.6 m thick. S. junceum (L.) colonizes not only fan/cone/taluses but also headwalls and cliffs and, for a 0.6 m thick soil, it stabilises these areas up to 45°. The effectiveness of this reinforcement, however, depends strongly on the frequency of soil and seasonal grass vegetation removal due to shallow landsliding before the entrance of the shrub species.     

Proline and soluble sugars accumulation in three pepper species (Capsicum spp) in response to water stress imposed at different stages of growth

Drought is a major production constraint for major fruits and vegetable crops in the tropics.This study was conducted to investigate the effect of limited water supply at three growth stages (vegetative,flowering and fruiting) on the accumulation of proline and soluble sugars in three pepper species.Seeds of the three pepper species,Capsicum chinense Jacq.,C.annuum L.and C.frutescens L.were raised in a nursery and the seedlings were transplanted into seventy two plastic pots arranged in a randomized complete block design with three replicates,25 days after planting.Four water treatments,200 mL of water supplied twice daily (W₁),once in every three days (W₂),once in every five days (W₃),and zero water supplied throughout growing period (W₀) were imposed at three vegetative,flowering,and fruiting growth stages.Data were collected on relative water content,free proline and total soluble sugar.Data collected were subjected to analysis of variance and means were separated using Duncan''s multiple range test.Results show that the concentration of proline and soluble sugar in leaves of the three pepper species were found to be remarkable at the different stages of growth in the stressed plants.     

Killing Carp (Cyprinus carpio) as a Volunteer Practice: implications for community involvement in invasive species management and policy

Community engagement is understood to be one of the keys to successful environmental programs—‘the social pillar’ of management. In this paper we examine community engagement where volunteers participate by killing invasive animals. Most research to date focuses on the biological or management implications of volunteer efforts for the invasive species, with little attention to the people involved or the social acceptability of killing animals in this context. Here, we report on a survey and participant observations of community fishing events in south-eastern Australia, where volunteers fish for and kill carp (Cyprinus carpio). We examine who takes part in these events, their motivations for being involved and the implications for ongoing community engagement. Survey respondents were predominantly well-educated Australian-born men, motivated to fish by a desire to spend time in nature. However, we also noted a strong response from overseas-born men with different motivations. Our survey elicited complex responses regarding killing, illustrating contradictory, sometimes conflicted experiences, which jar with personal motivations. The implications are that questions of ethics must extend to the human volunteers, and that more direct communication of program outcomes and the proposed benefits for volunteers be more rigorously assessed. We argue that invasive species management must contend with the experiences of volunteers, otherwise meaningful dialogue and program objectives risk being undermined.     

Spatial and temporal distribution of tenebrionid species (Coleoptera) in the Negev Highlands, Israel

Tenebrionid species composition and activity level were studied, using pitfall traps, in two sandy (dune and stabilized sand field) and four compact soil (wadi, north- and south-facing slopes, and loess plain) habitats in the Negev Desert Highlands, Israel. Each soil type had a distinctive species composition but habitats within soft types were similar both in species composition and phenologies. The number of species was not correlated with habitat primary production; it was low in sandy habitats (19 spp.) and high in compact soil (33 spp.) habitats. Within the compact soil habitats, large-size species were abundant only in the high plant-cover wadi, and the low plant-cover slopes and plain were dominated by smaller species. We suggest that low plant cover on the slopes and plain exposes large tenebrionids to predation by birds and limits them to the wadi where they are concealed and find refuge in the plant cover.     

The recent expansion of an avian invasive species (the Cattle Egret Ardea ibis) in Algeria

This study identifies new information on the recent distribution of an invasive bird species, the Cattle Egret Ardea ibis, in Algeria. Breeding and wintering distributions as well as breeding numbers were obtained from large-scale surveys in 1999 and 2007, and from historical data. Between 1999 and 2007, the total number of colonies found increased from 51 to 87, and most were located in the northern part of the country. The breeding distribution area, confined to the coastal areas in the 1970s, has shifted further south, and reached the northern part of the Sahara since the 2000s. Most colonies were established during the period 1980-1995. The oldest colonies were generally larger than the recent ones. The number of colonies increased by 83% between 1999 and 2007 in the 12 administrative units (wilayas) surveyed. The number of breeding pairs increased from 7765 in 1999 to 28544 in 2007, corresponding to an annual population growth rate of 17.7%. The changes in distribution and population dynamics since the 1970s and the potential factors affecting these changes are discussed.     

Body size and leg length variation in several species of darkling beetles (Coleoptera: Tenebrionidae) along a rainfall and altitudinal gradient in the Negev Desert (Israel)

We studied body size (elytra length) and leg length variation in seven tenebrionid species along a rainfall and environmental gradient from the Ramon erosion cirque (Israel). Body size was not correlated with altitude in three species, while four species demonstrated changes in body size with altitude. Three species decreased their body size along the altitudinal gradient, whereasSepidium dathandemonstrated the opposite trend. The pattern of variation of body size along the altitudinal gradient inAdesmia metallica, Erodius edomitusandZophosis complanatamay be explained by ambient temperature rather than productivity variation. Neither elevation nor species abundance affected variance in body size of any species. Femur length changed significantly along the altitudinal gradient inA. metallicaonly. Both males and females had relatively longer legs in low elevations and relatively shorter legs in high elevations. Individuals with the longest legs were recorded on soils with low clay and high rock and gravel content. The texture of the soil had no noticeable effect on the leg length of all other beetle species.     

德国汉堡城市转型的产业-空间-制度协同演化研究

世界上著名的港口城市大多都经历过因港而兴又因港而衰,但再次因港而兴的城市并不多,汉堡则是港口城市成功转型的典范。本文构建了德国汉堡城市转型的产业-空间-制度协同演化分析框架,研究揭示:汉堡城市转型紧紧围绕着港口功能和港口区域展开;城市产业转型过程中需要空间载体支撑和政策与协调机制保障;继承性地升级传统优势产业、实行可持续的空间开发计划、注重政策的系统性与协调性是城市转型成功的重要途径。在此基础上,本文得出了服务于我国大城市转型发展的经验和启示。     

The effect of radiation on seedling growth and physiology in four species of Prosopis L. (Mimosaceae)

Domestication of wild plants needs efforts focused particularly on the development of the theoretical basis of plant responses to environmental conditions. The objective of this study was to assess the effect of radiation on seedling growth and physiology of Prosopis alba, P. chilensis, P. flexuosa and P. glandulosa. Seedlings were grown in a greenhouse and randomly assigned to three light environments: full-sun, 52% sun, and 38% sun. No significant differences were found in the rate of leaf appearance and plant height 60 days after the light treatments began. Instantaneous CO₂uptake was not affected by the light environment during leaf development and did not differ among species. Variations in radiation availability resulted in significant differences in biomass accumulation, shoot/root ratio, protein and total non-structural carbohydrates contents. The practice of shading seedlings reduces the chances of survival ofProsopis due to an increase of the shoot/root ratio and a reduction of total biomass, stored carbohydrates, and the C:N balance.     

Assessing regional differences in predation of endangered species: Implications from Texas populations of the endangered star cactus (Astrophytum asterias)

Understanding threats to endangered species is one of the most critical components of implementing a successful recovery plan. For the endangered star cactus Astrophytum asterias, both mammalian and insect herbivory have been documented as a major threat to populations in Mexico. Herein, we focus on populations of A. asterias in Texas, examining how mortality threats differ from populations found in Mexico as well as among sites within Texas. Our study supports insect and mammalian herbivory as a major threat to A. asterias in Texas, with reductions in population sizes ranging between 16 and 54%. However, our study highlights that both regional and local differences can influence rates of mortality even in a range-restricted species such as A. asterias and highlights the need to assess threats at both of these levels for effective development and implementation of endangered species recovery plans.     

Differences in production and mortality of reproductive structures in two Prosopis L. (Mimosaceae) shrub species from Patagonia, Argentina

Prosopis L. pods have been proposed as a source of gum (galactomannans), with potential applications as a thickening agent in the food industry. The objective of this work was to compare, under field conditions, the production and mortality of reproductive structures in two sympatric shrub species of Prosopis: P. alpataco Phillipi and P. denudans Bentham. Our results indicate that fruit production in Prosopis denudans and P. alpataco is very low and erratic in non-irrigated lands. Although large quantities of flowers (15,000–25,000 flowers*0.40 m⁻²) can be found in one flowering season, 70–80% are shed before they reach anthesis and 20–28% are aborted between anthesis and fruit set. We conclude that the utilization of native populations of Prosopis denudans and P. alpataco for fruit production in Patagonian steppe, could not guarantee a consistent supply for the food industry.     

Competition as a barrier to establishment of a native perennial grass (Elymus elymoides) in alien annual grass (Bromus tectorum) communities

The alien grass Bromus tectorum dominates stable annual-plant communities that have replaced native shrub-perennial grass communities over much of the semi-arid western United States. We conducted field competition experiments between B. tectorum and a native grass, Elymus elymoides, on two sites to determine the effects of B. tectorum competition on perennial grasses, and the role of B. tectorum competition in the stability of B. tectorum-dominated communities. B. tectorum competition acting on seedling-stage E. elymoides plants greatly reduced first-year relative growth rates and biomass which, in turn, reduced second-year survival, biomass, and flowering. However, B. tectorum competition acting on older E. elymoides plants had much less effect, which may help to explain why intact perennial-plant communities are resistant to B. tectorum invasion. At the drier site, direct effects of B. tectorum competition were less, but competition and drier habitat combined to produce greater E. elymoides mortality.     

Curvature analysis as a tool for subsidence-related risk zones identification in the city of Tuzla (BiH)

Shallow Miocene salt deposits located below the city of Tuzla (BiH) have been exploited during the last 60 years by means of wells extracting salt-saturated groundwater brines. The massive extraction activities have led to severe subsidence accommodated by collapse and strain localization. Surface topography and geomorphology have been influenced and modified by several faults and fractures.A series of sequential topographical survey data collected during the last 50 years have been used to obtain the total subsidence envelope surface. In order to analyze the salt dissolution-related morphological development of the Tuzla topography and to identify the location of faults and fractures in the deformed area, we applied curvature analysis to the subsidence surface by means of two different analytical methods: the directional, two-dimensional curvature and the analytic Gaussian curvature. The comparison of the curvature maps with those of surface fractures visible in the area shows a good spatial agreement between the directional curvature and fracture intensity, whereas the subsurface normal faults are more evident in the Gaussian curvature maps.     

Incremental Growth of Plains-Type (Compactional) Folds in a Cratonic Environment as Revealed by the Sedimentary Sequence

The enigma of the origin and development of plains-type folds, as they were christened in the early 20th Century, essentially has been solved. The folds, a considerable distance from the tectonic disturbance, were formed by draping of sediments over differentially displaced Precambrian basement fault blocks. These Precambrian basement fault blocks controlled the location, size, and shape of the folds. Forces were transmitted through the rigid basement causing readjustment along the indigenous fracture/fault pattern formed much earlier. In the U.S. Midcontinent, the crystalline basement is overlain by a thin veneer of sediments, and once the structures were formed, they continued to develop as evidenced by features in the overlying sediments. As the stress was transmitted through the basement and then relaxed, the fault blocks moved differentially in concert to these outside forces. Sediment compaction and nondeposition over structural topographic highs reacted accordingly to form the features as seen today. To determine the structural history, structural closure on different horizons on the anticline is plotted in their appropriate stratigraphic position at depth. This gives a compaction line for each tectonically coherent segment. Similar segments show a relatively straightline with offsets at major unconformities indicating breaks in the continuum. It is at these breaks that the section can be stretched until the compaction line matches as a continuum with the resulting gap giving the approximate amount of missing section for that part of the rock column. Conversely, the amount of closure on a structure at depth for each line segment can be estimated by extrapolating downward in that segment. This technique to determine depth of burial and thus the amount of missing stratigraphic section from well data at numerous locations has been compared with estimates made by other methods and the results are similar. Where no other data are available or for quick estimates, then, it is proposed that this approach will give reasonable results and that the values can be used as a constraint in basin modeling.     

Changes in plant species composition and diversity of alpine Kobresia (Kobresia pygmaea) steppe meadow at different stages of desertification in the North Tibetan plateau

The impacts of desertification on the vegetation composition, structure, and species diversity of alpine Kobresia steppe meadow were evaluated in an area of severe desertification in Anduo County, Tibet Autonomous Region, northern China. We investigated and analyzed the floristic features of communities at four different stages of desertification (slight desertification [SLD], moderate desertification [MD], severe desertification [SD], and very severe desertification [VSD]). The composition and structure of the alpine Kobresia steppe meadow at the SLD site differed significantly from that at the MD, SD, and VSD sites. Species that were more drought resistant and inedible by livestock were the dominant species at the SD site. No plants were found in the shifting dunes of the VSD site. Species diversity also decreased with increasing desertification. The SLD site had the largest mean number of species and individuals and the largest richness index; the MD grassland had the largest Shannon-Wiener index and evenness index, but the smallest Simpson’s index. The vegetation cover declined from 91.8% to 34.8% as desertification increased from SLD to SD, and reached 0% in VSD areas with shifting dunes.     

Influence of cattle grazing on population density and species richness of granivorous birds (Emberizidae) in the arid plain of the Monte, Argentina

Cattle grazing is an important disturbance in the Monte plain, reducing grass biomass and rates of fruit setting. Grass seeds are the most important food for granivorous birds (Emberizidae) during winter. The objective of this study was to test whether granivorous bird populations (Emberizidae), grass seed production, and vegetation structure differed at sites with different intensities of grazing. Emberizid density and species richness were higher in the ungrazed site than in the two grazed paddocks. Seed abundance was also higher in ungrazed vs. grazed sites. Woody vegetation, that serve as safe nest sites, did not differ among treatments. Granivorous bird populations seemed to be affected by cattle grazing; however, the main mechanisms of this process remain unknown.