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.     

Water requirements for germination and early seedling establishment in four African savanna woody plant species

The aim of this study was to determine the water requirements for germination and early seedling establishment of four African savanna tree species, namelyAcacia karroo, A. nilotica, A. tortilisandMundulea sericea. The acacias are characteristic of nutrient-rich, andM. sericeaof nutrient-poor savannas. Imbibition times of scarified seeds ofA. karroo(4 h),M. sericea(6 h) andA. tortilis(8 h) were rapid relative toA. nilotica(28 h) and were inversely correlated with seed size. Imbibed water is lost in about 2 h after drying at 25°C for all species exceptA. nilotica(only 70% moisture loss). Seeds ofA. karrooandM. sericeakept at 40°C dried to below their original moisture contents within 2 h. Seeds ofA. niloticaandA. tortilisdried at 40°C lost viability relative to (undried) control seeds, while there was no significant loss of viability forA. karrooandM. sericea. For fully imbibed seeds to germinate in sandy savanna soils, all four species required at least the equivalent of 3 mm rainfall every 2 days under mild greenhouse conditions. However, most ungerminated seeds were still viable despite drying-out from a fully imbibed state. Maintenance of soil at 50% field capacity (FC), or watering to FC every 9th day is the maintenance requirements for 2-week-old seedlings ofA. niloticaandM. sericeato continue growth for a further 5 weeks under greenhouse conditions, althoughA. niloticamostly survived 25% FC with one seedling surviving 12·5% FC. Root penetration was rapid in sandy soils, withA. niloticaandM. sericeaattaining a depth of 40 cm within 15 days. Frequent, but not necessarily high, rainfall appears to be essential for germination and seedling survival over the first 7 weeks.     

Nutritive value of twoTamarixspecies in Egypt

Shoots ofTamarix niloticaandT. aphyllawere collected from north Sinai, the Nile Delta and North Western Desert of Egypt and analysed forin vitrototal digestible nutrients, nutritive value, gross energy and element contents. Pronounced differences were recorded between the two species for all the estimated variables. Variation in gross energy in the tissues of both species in relation to different locations was insignificant. The two evaluated species have relatively low contents of N, K, Ca and crude protein and high contents of P, Mg and Na. There was a moderate positive correlation between the N–NDF, K–CF and EE–NDF ofTamarix aphylla. The present study evaluated the nutrient status of both species as poor forage.     

Phenology ofMedicago minimaandErodium cicutariumin semi-arid Argentina

The phenology ofMedicago minimavar.minimaandErodium cicutariumwas studied at two different field sites in the Calden District (approx. 10 million ha), a temperate semi-arid phytogeographical region in central Argentina. One site had been protected from wild and domestic herbivores for the 6 previous years. The other adjacent site had been exposed to continuous grazing by cattle for several decades. A phenological key was made for each species in 1988, and this key was improved during the 1989 growing season when phenological observations were made every 1–3 weeks.The growth cycle ofM. minimaandE. cicutariumwas similar at the two studied sites. Initiation of the cycle occurred in autumn and appeared to be associated with soil water availability. Phenological patterns were very dynamic at the reproductive stage in both species. This stage started earlier and was faster inE. cicutariumthan inM. minima. The end of the growing season occurred during late spring, concomitant with high maximum air temperatures. Our results suggest that these species hasten their development when air temperature increases and soil water availability decreases. This could be an important strategy in these species which allows them to persist as seeds, and produce a new generation under favourable environmental conditions.     

Gender-related differences of shrubs in stands of Atriplex canescens with different histories of grazing by cattle

Atriplex canescens is a relatively common dioecious shrub in western North America. It is considered a valuable forage resource for both wild and domestic herbivores. Sex ratios and shrub dimensions were recorded in stands of tetraploid A. canescens that had been either protected from cattle grazing or summer- or winter-grazed by cattle for at least 20 years. Stem diameter and crown shape were used as surrogates for shrub age which could not be estimated by counting growth rings. Shrub sex ratios in exclosures were significantly more female biased than the empirically derived ratio for tetraploid A. canescens (55 female:35 male: 10 monecious). Conversely, shrub sex ratios in grazed pastures were not significantly different from the empirical ratio. Proportion of female shrubs in exclosures was significantly higher than in grazed pastures. Proportion of male shrubs, on the other hand, was similar in exclosures and grazed pastures. Winter-grazed shrub stands were apparently younger than both summer-grazed and protected shrubs. Protected shrubs appeared to be the oldest. Grazed female shrubs were apparently younger than grazed males, however, shrub ages of protected male and female shrubs were apparently not different. Cattle-grazing may have affected female shrubs more negatively at this site, causing gender-based differential mortality, and/or sex-shifting. Such processes could account for the differences in sex ratios, and for the apparent gender-related differences in shrub age that were observed.     

Hydrobiology of some solar salt works in India

The hydrobiology of two Indian solar salt works was investigated. A salient feature was variability in physico-chemical and biological characteristics. The filamentous cyanophyceansLyngbya majuscula andOscillatoria salina and the chlorophyceanXenococcus aceervatus were the major primary producers. Significant fauna were protozoans, rotifers and copepods.Artemia was present in only one set of solar salt pans, where it was dominant. The study illustrates the importance ofArtemia in the biological management of solar salt works. This paper is dedicated to Thiru. K. Ayyaru Vandayar, Member, Governing body, A.V.V.M. Sri Pshpam College (Autonomous), Poondi, on his sixtieth birthday     

Two field and greenhouse diseases ofProsopis(mesquite)

Canker and tip-dieback diseases have been found in field and greenhouse plantings ofProsopisbeing examined in agroforestry trials in South Texas. Several fungal species were associated with the field cankers, most notably aLasiodiplodiaand aPestalotiopsis. In the greenhouse, a tip-dieback as well as a canker disease that began at pruning cuts on the stock plants was seen.Pestalotiopsiswas most commonly isolated from these plants. Isolated cultures of theLasiodiplodiaand thePestalotiopsistogether with several other often associated fungi, (includingAlternariaFusarium) were tested for pathogenicity on young mesquite plants. OnlyLasiodiplodiaandPestalotiopsisproduced cankers under the conditions tested when spores were applied using wound inoculation techniques.Pestalotiopsisrequired high wound inoculation techniques.Pestalotiopsisrequired high humidity and proved much less damaging compared toLasiodiplodia, which closely mimicked the field symptoms. Benlate was found to give the greatest growth inhibition of these fungal pathogens inin vitrofungicide tests.     

A natural hybrid population betweenNeobuxbaumia tetetzoandCephalocereus columna-trajani(Cactaceae)

A supposed hybrid population betweenNeobuxbaumia tetetzoandCephalocereus columna-trajani(Cactaceae) in a semi-arid ecosystem at Zapotitlán de La Salinas, in the Mexican State of Puebla, was investigated by analysing number of ribs, number of areoles per cm and number of branches. Tests for equality of means using the Games and Howell method and Stepwise Discriminant Analysis, indicated that the number of ribs and number of areoles per cm supported our hypothesis for the existence of these naturally occurring hybrids, which are intermediate and distinct from the parental species. Other qualitative characteristics which distinguished hybrids and parental species are highlighted, and the possible meaning of the phenomenon is discussed.     

Diet selection in captivity by a generalist herbivorous rodent (Octodon degus) from the Chilean coastal desert

Five captive adult female degus (Octodon degus) were offered leaves and twigs to eat from three woody (Adesmia bedwellii,Porlieria chilensisandProustia pungens) and two suffruticose (Baccharis paniculataandChenopodium petiolase) shrubs that provide cover in their natural habitat. The degus discriminated among the plant species, consuming lower amounts ofP. chilensis. Daily body mass losses of degus were significantly higher when they were fed uponP. pungensandP. chilensis. The nutritional value of plants, concomitant with degu nutritional requirements, may explain changes in shrub cover previously found to follow removal of degus from experimental plots.     

On the spatial distribution of nests of the antsMessor arenariusandMessor ebeninus

Ants of the speciesMessor arenariusandM. ebeninusare known as common granivores in the deserts of the Middle East and North Africa. The relationship between the spatial distribution of nests of these ant species and the distribution of vegetation was examined in the Negev highlands. Using the method of nearest neighbour analysis, it was found that nests ofM. arenariusare evenly dispersed while the dispersion of nests ofM. ebeninusdoes not differ from a random distribution. It is suggested that in desert surroundings there is a connection between the distribution pattern of nests of harvester ants and their foraging type. It seems that nests of individually foraging ants are usually evenly dispersed while nests of trunk-trail foraging ants are usually distributed in a random or aggregated dispersion.     

Identification of Kalidium species (Chenopodiaceae) by DNA barcoding

DNA barcoding is an increasingly prevalent molecular biological technology which uses a short and conserved DNA fragment to facilitate rapid and accurate species identification. Kalidium species are distributed in saline soil habitat throughout Southeast Europe and Northwest Asia, and used mainly as forage grass in China. The discrimination of Kalidium species was based only on morphology-based identification systems and limited to recognized species. Here, we tested four DNA candidate loci, one nuclear locus (ITS, internal transcribed spacer) and three plastid loci (rbcL, matK and ycf1b), to select potential DNA barcodes for identifying different Kalidium species. Results showed that the best DNA barcode was ITS locus, which displayed the highest species discrimination rate (100%), followed by matK (33.3%), ycf1b (16.7%), and rbcL (16.7%). Meanwhile, four loci clearly identified the variant species, Kalidium cuspidatum (Ung.-Sternb.) Grub.var. sinicum A. J. Li, as a single species in Kalidium.     

Catastrophic drought-induced die-off of perennial chenopod shrubs in arid Australia following intensive cattle browsing

Cover and survivorship of perennial chenopods, Atriplex vesicaria and Maireana astrotricha, declined markedly during a prolonged dry period at Roxby Downs in arid South Australia. Despite their resilience to browsing in favourable seasons, only 2% of the A. vesicaria shrubs browsed heavily by cattle survived the drought. M. astrotricha exhibited greater drought survivorship, although the post-drought cover retention in browsed shrubs was only half that of unbrowsed controls. Survivorship was highest for unbrowsed chenopods growing in moisture-enhanced run-on or dune-base environments. Maintenance of these patchy areas with reduced water-stress is hence important for the persistence of browsed chenopod shrublands. Light browsing by either European Rabbits (Oryctolagus cuniculus) or Greater Stick-nest Rats (Leporillus conditor) had no measurable impact upon chenopod survivorship.     

Neighbor competition modifies demographic responses of desert dune annuals to gradients in sand stability

A field experiment was conducted to test the hypothesis that competitive interactions affect demographic responses of desert dune annuals to gradients in sand stability. The experiment was based on a three-way factorial design with two types of neighbor treatments (complete neighbor removalvs. control), two types of habitats (stablevs. unstable sands) and two species which characterize sandy areas of the western Negev Desert (Neurada procumbensandBromus fasciculatus). Each of the eight treatment/habitat/species combinations was characterized by three demographic variables: seedling survival to reproduction, fruit number per reproductive plant and fruit number per seedling. All of these variables exhibited significant interactions between the effects of neighbor removal and habitat type, indicating that neighbor conditions were important in determining the observed patterns of demographic variation. Moreover, while plants ofNeurada procumbensgrowing without neighbors suffered more mortality on unstable sands, conspecific plants growing at natural density conditions suffered more mortality on stable sands. In the case ofBromus fasciculatus, individuals growing in the absence of competitive effects produced more fruits on stable sands, but conspecific plants growing at natural density conditions exhibited higher fruit production on unstable sands. These findings indicate that competitive effects not only modify, but may even reverse demographic responses of desert dune annuals to gradients in sand stability. Based on these results and evidence from two other studies it is suggested that seed dispersal from abiotically favorable into less favorable habitats may increase fitness of desert annuals by reducing the average effect of competition.     

Predispersal reproductive ecology of an arid land crucifer,Moricandia moricandioides: effect of mammal herbivory on seed production

In this paper the effect of herbivory on the seed production ofMoricandia moricandioides(Cruciferae), an annual species living in arid habitats of south-eastern Spain, is analysed. Firstly, the flowering and fruiting phenology and the composition and structure of the pollinator guild is described, in order to compare the overall effect of mutualistic speciesvs. that of antagonistic species onM. moricandioidesseed production. The loss of female reproductive success due to each herbivore species attacking the plant is then quantified, in an attempt to differentiate the effects on plant seed production of each herbivorous species. The results indicate that only antagonistic organisms interacting withM. moricandioidesinfluenced the female fitness of this plant species. In fact, pollinator abundance or activity did not correlate with the number of seeds dispersed by the plants. In addition, of all the herbivore species, only sheep activity significantly influenced seed production ofM. moricandioidesindividuals, the effect of the remaining crucivorous herbivores being cancelled by the stronger herbivory of sheep. The results of this study suggest that herbivory by sheep, in addition to decreasing the seed production ofM. moricandioides, could be an important determinant of the current distribution pattern of this crucifer species on the ramblas of the Baza basin.     

Short-term effects of shrub control on two different plant communities in Argentina

The aim of this work was to study the effect of controlling jarilla (Larreaspp.), nonforage shrubs for livestock, on two plant communities with different forage production in the arid mid-west of Argentina. Total vegetation cover, forage species cover and carrying capacity were determined during three growing seasons, for cleared and uncleared plots. At the end of the study, significant differences were found in theLarrea cuneifoliacommunity, where average forage species cover increased by 156% over the control, and greater carrying capacity (129%) was also obtained from the cleared treatment. No significant differences were found in theLarrea divaricatacommunity. Data lead us to recommend shrub control as an improvement practice only in areas with low forage species cover and poor carrying capacity.     

Distribution analysis ofAlliumL. species of the Dzhungarian Alatau

In the Dzhungarian Alatau, a large Asian mountain range, 33 species from the polymorphic genusAlliumL. have been found. They belong to the subgeneraRhizirideum,AlliumandMelanocrommyumand are distributed from the foothills to alpine belts. The geographical and genesis analysis of these species is given. Five species can be ascribed to the category of autochtonous of the region, among them one being endemic to the Dzhungarian Alatau.     

Germination ofAcacia origena,A. pilispinaandPterolobium stellatumin response to different pre-sowing seed treatments, temperature and light

Seeds ofAcacia origena,A. pilispinaandPterolobium stellatumhave a hard seed coat that hampers imbibition of water and prevents maximum, uniform and rapid germination. Therefore, the seeds were subjected to different treatments involving mechanical scarification, concentrated sulphuric acid and boiling water to break the dormancy imposed by the hard seed coat. To determine the effects of different constant temperature regimes on germination, scarified seeds were incubated on a thermogradient at 10, 15, 20, 25 and 30°C. Germination of scarified seeds was also tested in light and dark. Mechanical scarification resulted in 100% germination for theAcaciaspecies and 94% forP. stellatum. ForA. origena, sulphuric acid treatments for 60, 90 and 120 min resulted in significantly higher per cent germination (>95%) than all the other treatments. ForA. pilispina, sulphuric acid treatments for 45 and 60 min, as well as immersing seeds for 1 min in hot water, gave significantly higher per cent germination (97%) than all the other treatments. ForP. stellatum, mechanical scarification and all the acid treatments applied resulted in significantly higher per cent germination (>85%) than the control and all hot water treatments. All seeds ofP. stellatumimmersed in hot water, even for 1 min, rotted soon after sowing, indicating that they are sensitive to high temperatures. Scarified seeds of the twoAcaciaspecies germinated to a higher degree (≥90%) between 10 and 30°C, while germination of scarified seeds ofP. stellatumranged from 48 to 82% between 10 and 30°C. Scarified seeds of the three species germinated to a large extent (>70%) both in light and dark, indicating that seeds do not require light for germination.     

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.     

Resting spores of the freshwater diatomsAcanthoceras andUrosolenia

Diatom resting spores are a widespread, but sometimes misconstrued component of siliceous microfossil assemblages. We illustrate and discuss resting spore morphology found in populations ofAcanthoceras andUrosolenia, two widely distributed freshwater genera. Taxonomic status of these genera and the potential paleolimnologic interpretation of resting spores are discussed.     

Holocene pollen record from a peatland in the West Caucasus,Abkhasia, Black Sea region

A pollen sequence spanning over 4000 years was recovered from a small (0.1 ha)Sphagnum-dominated peatland in the mountains near Sukhumi, Abkhasia, West Georgia. The peatland lies atc. 1650 m a.s.l. in denseFagus-Abies forest. The pollen record reveals totally forested surroundings throughout since at least 4000 years BP (90–95% AP). It begins with a complex forest dominated byFagus with large proportions ofCastanea, Acer andUlmus. ThenCastanea became dominant whileFagus was still prominent. This might indicate a warmer climate. Later development shows a dramatic decline ofCastanea. Its pollen drops down to 3–5%. RecentlyAbies has been experiencing an exponential growth. Now it comprises over 50% of the forest composition around the peatland. These changes have possibly been caused by human influence together with climatic change. The basin started as aPotamogeton-dominated shallow lake with ferns andAlisma along the margins. Later it developed into a sedge fen and finally aSphagnum andMenyanthes poor fen with scatteredCarex limosa. The record indicates a progression towards oligotrophy.This publication is the fifth paper in a series of papers presented at the session on Past Climatic Change and the Development of Peatlands at the ASLO and SWS Meetings in Edmonton, Canada, May 30–June 3, 1993. Dr. P. Kuhry and Dr S. C. Zoltai are serving as Guest Editors.