The soil seed bank is a major component of plant communities. However, long-term analyses of the dynamics of the seed bank and the ensuing vegetation are rare. Here, we studied the dynamics in plant communities with high dominance of annuals in Mediterranean, semiarid, and arid ecosystems for nine consecutive years. For annuals, we hypothesized that the density of the seed bank would be more stable than the density of the standing herbaceous vegetation. Moreover, we predicted that differences in temporal variability between the seed bank and the vegetation would increase with aridity, where year-to-year rainfall variability is higher. We found that the temporal variability at the population level (assessed as the standard deviation of the loge-transformed density) of the nine dominant annuals in each site did not differ between the seed bank and the ensuing vegetation in any of the sites. For the total density of annuals, patterns depended on aridity. In the Mediterranean site, the temporal variability was similar in the seed bank and the vegetation (0.40 vs. 0.40). Still, in the semiarid and arid sites, variability in the seed bank was lower than in the vegetation (0.49 vs. 1.01 and 0.63 vs. 1.38, respectively). This difference between the population-level patterns and the total density of annuals can be related to the lower population synchrony in their seed bank. In contrast, for the herbaceous perennials (all species combined), the seed bank variability was higher than in the vegetation. Overall, our results highlight the role of the seed bank in buffering the annual vegetation density with increasing climatic uncertainty typical in aridity gradients. This role is crucial under the increasing uncertainty imposed by climatic change in the region.

Abstract Ecological theory predicts that the soil seed bank stabilizes the composition of annual plant communities in the face of environmental variability. However, long-term data on the community dynamics in the seed bank and the standing vegetation are needed to test this prediction. We tested the hypothesis that the composition of the seed bank undergoes lower temporal variability than the standing vegetation in a 9-year study in Mediterranean, semi-arid and arid ecosystems. The composition of the seed bank was estimated by collecting soil cores from the studied sites on an annual basis. Seedling emergence under optimal watering conditions was measured in each soil core for three consecutive years, to account for seed dormancy. In all sites, the composition of the seed bank differed from the vegetation throughout the years. Small-seeded and dormant-seeded species had a higher frequency in the seed bank than in the standing vegetation. In contrast, functional group membership (grasses vs. forbs) did not explain differences in species frequency between the seed bank and the vegetation after controlling for differences between grasses and forbs in seed mass and seed dormancy. Contrary to predictions, the magnitude of year-to-year variability (the mean compositional dissimilarity between consecutive years) was not lower in the seed bank than in the vegetation in all sites. However, long-term compositional trends in the seed bank were weaker than in the vegetation in the Mediterranean and semi-arid sites. In the arid site where year-to-year variability was highest, no long-term trends were observed. Synthesis. The effect of the seed bank on the temporal variability of the vegetation in annual communities depends on site conditions and time-scale. While the year-to-year variability of the seed bank is similar to the vegetation, the soil seed bank can buffer long-term trends.

Traditional sheep grazing in natural and planted forests in the Mediterranean basin is based on night penning in seasonal corrals, where excreta accumulate instead of being returned to the grazed range. Lack of planning and unawareness of the long-term effect of abandoned corrals is negatively affecting the landscape and grazing value of the forests. We studied the dynamics of soil nutrients in a chronosequence of abandoned sheep corrals in planted Eucalyptus forests in two semi-arid sites in Israel. Dung decomposition was a slow process lasting 5–10 years. Soluble-N, P and K in the soil beneath the dung layer decreased gradually. Yet, 15–20 years after corral abandonment K and P were still 2 to 3 times higher than in the surrounding range, while soluble-N decreased within 10–15 years. Biomass production in the abandoned corrals was 2–3 times higher than in the grazed range up to 20 years after abandonment. Corrals act as sinks of soil nutrients that are lost to the grazed range. We propose that a balance between nutrient inputs (i.e. atmospheric deposition, N-fixation) and outputs (i.e. grazing and night penning) is reached in the grazed range at a low level of soil nutrients, which may constrain vegetation productivity. © 2019 Elsevier Ltd

Goat herding is an important tool in the ecologically sound management of Mediterranean shrublands and woodlands, although effective levels of woody biomass removal by the goats is neither guaranteed nor easy to predict. Preliminary observations indicated that one reason for this may be poor understanding of plant-herbivore interactions that operate intraspecifically at the local spatial scale. We asked, whether goats show intraspecific preferences among neighboring plants when foraging a small local population of Pistacia lentiscus, a dominant tall shrub. First, we characterized and quantified the profile of stored and emitted volatile organic compounds (VOCs) and the PEG-binding capacity of tannins (a proxy for protein binding capacity) in the foliage of P. lentiscus shrubs, sampled within an area of 0.9 ha. We then tested goat preference between pairs of these shrubs that differed in chemical composition. Almost all sampled P. lentiscus shrubs were allocated to one of two distinct VOC chemotypes: one dominated by germacrene D and limonene (designated chemotype L) and the other by germacrene D and α-pinene (chemotype P). In contrast, continuous moderate variability was found in the binding capacity of tannins in the foliage. Goats showed preference for shrubs of chemotype L over those of chemotype P, and their preference was negatively correlated with the binding capacity of tannins. Possible influences of VOCs on goat preference that may explain the observed patterns are discussed in the light of possible context-dependent interpretation of plant VOC signals by large mammalian herbivores. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.

Weeds are plant species that adapted to man-made habitats, 1 and are usually innocuous wild plants in their geographical center of origin. 2 They are unintentionally spread and perpetuated by the activities of man and his domesticated animals, including those that have unintentionally become domesticated. Most weeds are herbaceus, but some shrubs and trees, such as Prosopis spp., Acacia spp., and Rubus spp., and cacti, such as Opuntia spp., are extremely noxious weeds in certain habitats. © 1985 by CRC Press, Inc.

Vegetation structure and composition of woodlands in the Mediterranean Basin have experienced extensive land-use change during recent decades. Decline in traditional foraging by goats is leading to more closed and spatially homogeneous woody vegetation, reduced plant diversity, and increased fire risk because of accumulation of inflammable material. We studied the use of cattle foraging as an alternative to goat foraging in Mediterranean oak woodlands. Our main goal was to provide basic information on the responses of woody vegetation to cattle foraging intensity, and on the factors affecting spatial patterns of woodland utilization. We conducted the study in the Western Galilee, Israel, in oak woodland dominated by Palestine oak (Quercus calliprinos Webb.) interspersed with patches of shrubs and herbaceous vegetation. Effects of two animal population densities, moderate (0.33 cow⋅ha−1) and high (0.55 cow⋅ha−1), on the structure, composition, and regeneration potential of dense and of open woody formations were examined. Four consecutive annual seasons of cattle foraging resulted in relatively large amounts of woody vegetation removal, especially under high animal density, but had no negative effects on woody species richness or regeneration potential from saplings. The type of vegetation formation and initial state of the woody vegetation were important factors affecting the degree of change. Woody biomass removal by cattle, as shown in this study, can reduce fire hazards and increase vegetation heterogeneity and plant diversity. These findings support the use of cattle as an efficient alternative tool for multi-purpose, sustainable management of Mediterranean oak woodlands. © 2018 Elsevier B.V.

Amaranthus (Amaranthaceae) is a genus of tropical origin but widely distributed all over the world, including temperate regions. 1,2About 50 species are native to the Americas and another 15 can be found in Europe, Asia, Africa, and Australia. Most amaranth species are pioneer nitrophilous annuals of open habitats and produce many small dormant seeds. This extensive seed production is associated with prolonged seed-dormancy and with prompt germination after soil disturbance and seed exposure to light. This assemblage of reproductive traits enables amaranths to survive by continuous colonization of new disturbed sites with full sunlight and little competition from other plants. With such strategy of reproduction it is not surprising that several species of amaranth were preadapted for invasion of habitats drastically modified by human activities. Thus, today, amaranths are best known as opportunistic weeds, associated with soil cultivation (e.g., A. hybridus L., A. powellii S. Watt., A. retroflexus L., A. spinosus L., etc.). However, other amaranth species have been domesticated in tropical and subtropical regions and are cultivated for their grain (A. hypochondriacus L., A. cruentus L., A. caudatus L. = A. edulis Spegazzini) or for leaf consumption (A. tricolor L. = A. gangeticus L., A. viridis L. = A. gracilis Desf., A. blitum L. = A. lividus L.). © 1994 by CRC Press, Inc.

Amaranthus is a genus of tropical origin that belongs to the Amaranthaceae. Today it is widely distributed all over the world, with species reaching temperate regions even before man converted some of them into cosmopolitan weeds or domesticates (crops or ornamentals).15 About 60 species are native to the Americas, and about 15 others to Europe, Asia, Africa, and Australia. Most of them are pioneer annuals of naturally open habitats, producing abundant seed. They thrive by constant colonization of sites of disturbed soil, with full sun and little competition. Long natural selection for such a way of life preadaptated certain of the species for success in habitats drastically disturbed by man. Thus, today Amaranthus spp. are best known as noxious weeds (e.g., A. hybridus L., A. retroflexus L., A. spinosus L., A. powellii S. Wats.). However, in tropical and subtropical countries, certain species are grown for grain (A. hypocondriacus L., A. cruentus L., A. caudatus L.), whereas the young plants of others are eaten as pot-herbs (A. dubius Mart., A. tricolor L.). Other species are cultivated as ornamentals for their highly colored inflorescence (A. caudatus L.) or leaves (A. tricolor L.). © 1995 by CRC Press, Inc.

Question: What are the controls on biomass production and species diversity in Mediterranean grasslands? Do medium-term (i.e. inter-annual) precipitation legacy effects on biomass production and diversity occur in these grasslands?. Location: Karei Deshe Experimental Range Station, Upper Galilee, northern Israel. Methods: We used a long-term (21-r) cattle-grazing experiment in a Mediterranean grassland to search for evidence of precipitation legacies on herbaceous above-ground biomass production and species diversity. Biomass production was measured in two seasonal late grazing treatments, in the winter and at peak vegetative production in the spring, while species diversity was determined at peak production. We used ANCOVA to test the effects of residual biomass, previous year's stocking density and previous year's biomass on current biomass production. We ran forward selection and ANCOVA to test for precipitation legacies, using precipitation variables relating to both previous and current year's rainfall. In addition we examined linear regressions of biomass and species diversity on current year's precipitation. Results: Biomass production and species diversity showed weak to negligible relationships with current year's precipitation. Biomass production, and to a lesser extent, diversity, were affected by inter-annual fluctuations in growing conditions. However, evidence of inter-annual precipitation legacies were found only for early season biomass production, and not for peak biomass production or species diversity. We found no effect of grazing on biomass production at the onset of the grazing season, regardless of important differences in previous year's stocking density. Additionally, we found no effect of previous year's biomass production or stocking density on the following year's biomass or diversity, but peak biomass production was strongly related to previous year's residual biomass. Conclusions: The lack of an inter-annual precipitation legacy on peak biomass production contributes to a growing body of evidence showing that Mediterranean ecosystems are unique among semi-arid and sub-humid ecosystems, where precipitation legacies play an integral role. Mediterranean ecosystems are unique in their combined long-term high variability in rainfall and long grazing history. This lack of precipitation legacy led to the development of vegetation that is highly resistant to inter-annual fluctuations in growing conditions. We propose that the high resistance contributes to the lack of inter-annual, or medium-term, precipitation legacies on the studied grassland, and may contribute to its persistence under future projected climate change in the region. © 2016 International Association for Vegetation Science

This text is intended for plant physiologists, molecular biologists, biochemists, biotechnologists, geneticists, horticulturalists, agromnomists and botanists, and upper-level undergraduate and graduate students in these disciplines. It integrates advances in the diverse and rapidly-expanding field of seed science, from ecological and demographic aspects of seed production, dispersal and germination, to the molecular biology of seed development. The book offers a broad, multidisciplinary approach that covers both theoretical and applied knowledge. © 1995 by Marcel Dekker. All rights reserved.

Arid and semiarid regions (i.e., deserts) cover about 30% of the world’s continents (except Europe) (Meigs, 1953). Deserts are frequently considered similar ecosystems, with water being the main limiting factor for their biota. This apparent similarity is, however, deceptive. In fact, deserts are extremely varied environments and differ in their climatic and edaphic conditions as well as in their biotic characteristics. Deserts vary in the amount of incident radiation and temperature [e.g., hot (Sahel) vs. cold (Patagonia) deserts], in the amount, frequency, and seasonal distribution of rainfall (e.g., deserts with winter, summer, biseasonal rains, or without seasonal rains), in the composition and geographic origin of their fauna and flora, and so forth. Despite their physical and biological diversification, all deserts are essentially regions of low and irregular rainfall in which évapotranspiration exceeds precipitation. Conditions favorable for plant growth usually occur in specific and rather scattered sites, during relatively short periods of time and sometimes even once in several years. Under such stringent selection, different adaptive strategies have evolved in desert plants, improving their fitness (i.e., individual survival and offspring production) under extreme conditions. These adaptive strategies are combinations of traits from different levels of biological organization and function (e.g., biochemical, physiological, developmental, genetic, demographic). Each of these traits contributes in a balanced and coordinated way to the fitness of the organism (Solbrig, 1993). On the other hand, plants from diverse taxa vary in their adapative potential to xeric conditions due to differences in morphological and physiological characteristics. Moreover, desert species may differ in their life cycle (annuals vs. perennials), life form (shrubs vs. herbaceous forms), timing of flowering, reproductive effort, seed dispersal, germination behavior, and so forth. It is not surprising, therefore, that diverse adaptive strategies are found in different taxa inhabiting deserts with contrasting environments. © 1995 by Marcel Dekker. All rights reserved.

We examined the temporal and spatial variation patterns of the grazing activity of free-ranging cattle in Mediterranean oak woodland in the Western Galilee, Israel, as affected by seasonal and management factors. The vegetation is dominated by scrub-oak woodland (Quercus calliprinos Webb.), interspersed with patches of semi-dwarf shrubs and herbaceous vegetation. High and moderate animal population densities of 0.55 and 0.33 cow ha−1, respectively, were replicated twice. Cattle behavior was monitored with activity sensors on GPS collars, and pedometers, and spatial data were processed with Geographic Information System (GIS) tools. Overall, cattle devoted 9.7 ± 0.7 h/day to grazing, mostly in woodland areas, although they are natural herbaceous grazers. Behavior was associated with seasonal changes in biotic and abiotic factors. Preference for the woody vegetation types was detectable over the annual time scale but large seasonal differences in preference canceled out to a large extent when viewed at that time scale. Cattle under high density spent more time grazing and made more use of woody vegetation and steeper slopes. Thus, relatively high population densities may be required for landscape-oriented management. The present findings should contribute to rational management of cattle grazing in Mediterranean woodlands. © 2016 Elsevier B.V.

Summer dormancy is an evolutionary response that some perennial cool-season grasses adopted as an avoidance strategy to escape summer drought and heat. It is correlated with superior survival after severe summer droughts in many perennial grass species originating from Mediterranean environments. Understanding the genetic mechanism and environmental determinants of summer dormancy is important for interpreting the evolutionary history of seasonal dormancy and for the development of genomic tools to improve the efficiency of genetic selection for this important trait. The objectives of this research are to assess morphological and biochemical attributes that seem to be specific for the characterization of summer dormancy in tall fescue, and to validate the hypothesis that genes underlying stem determinacy might be involved in the mechanism of summer dormancy. Our results suggest that vernalization is an important requirement in the onset of summer dormancy in tall fescue. Non-vernalized tall fescue plants do not exhibit summer dormancy as vernalized plants do and behave more like summer-active types. This is manifested by continuation of shoot growth and high root activity in water uptake during summer months. Therefore, summer dormancy in tall fescue should be tested only in plants that underwent vernalization and are not subjected to water deficit during summer months. Total phenolic concentration in tiller bases (antioxidants) does not seem to be related to vernalization. It is most likely an environmental response to protect meristems from oxidative stress. Sequence analysis of the homolog gene from tall fescue genotypes belonging to summer-dormant and summer-active tall fescue types showed a unique deletion of three nucleotides specific to the dormant genotypes. Higher tiller bud numbers in dormant plants that were not allowed to flower and complete the reproductive cycle, confirmed that stem determinacy is a major component in the mechanism of summer dormancy. The number of variables identified in these studies as potential players in summer dormancy in tall fescue including vernalization, , water status, and protection from oxidative stress are a further confirmation that summer dormancy is a quantitative trait controlled by several genes with varying effects and prone to genotype by environment interactions.

Well-defined productivity-precipitation relationships of ecosystems are needed as benchmarks for the validation of land models used for future projections. The productivity-precipitation relationship may be studied in two ways: the spatial approach relates differences in productivity to those in precipitation among sites along a precipitation gradient (the spatial fit, with a steeper slope); the temporal approach relates interannual productivity changes to variation in precipitation within sites (the temporal fits, with flatter slopes). Precipitation-reduction experiments in natural ecosystems represent a complement to the fits, because they can reduce precipitation below the natural range and are thus well suited to study potential effects of climate drying. Here, we analyse the effects of dry treatments in eleven multiyear precipitation-manipulation experiments, focusing on changes in the temporal fit. We expected that structural changes in the dry treatments would occur in some experiments, thereby reducing the intercept of the temporal fit and displacing the productivity-precipitation relationship downward the spatial fit. The majority of experiments (72%) showed that dry treatments did not alter the temporal fit. This implies that current temporal fits are to be preferred over the spatial fit to benchmark land-model projections of productivity under future climate within the precipitation ranges covered by the experiments. Moreover, in two experiments, the intercept of the temporal fit unexpectedly increased due to mechanisms that reduced either water loss or nutrient loss. The expected decrease of the intercept was observed in only one experiment, and only when distinguishing between the late and the early phases of the experiment. This implies that we currently do not know at which precipitation-reduction level or at which experimental duration structural changes will start to alter ecosystem productivity. Our study highlights the need for experiments with multiple, including more extreme, dry treatments, to identify the precipitation boundaries within which the current temporal fits remain valid. © 2016 John Wiley & Sons Ltd.

Rapid and uniform seed germination and seedling emergence under diverse environmental conditions is a desirable characteristic for crops. Common bean genotypes (Phaseolus vulgaris L.) differ in their low temperature tolerance regarding growth and yield. Cultivars tolerant to low temperature during the germination and emergence stages and carriers of the grain quality standards demanded by consumers are needed for the success of the bean crop. The objectives of this study were (i) to screen the seedling emergence and the phenotypic response of bean germplasm under a range of temperatures in controlled chamber and field conditions to display stress-tolerant genotypes with good agronomic performances and yield potential, and (ii) to compare the emergence of bean seedlings under controlled environment and in open field conditions to assess the efficiency of genebanks standard germination tests for predicting the performance of the seeds in the field. Three trials were conducted with 28 dry bean genotypes in open field and in growth chamber under low, moderate, and warm temperature. Morpho-agronomic data were used to evaluate the phenotypic performance of the different genotypes. Cool temperatures resulted in a reduction of the rate of emergence in the bean genotypes, however, emergence and early growth of bean could be under different genetic control and these processes need further research to be suitably modeled. Nine groups arose from the Principal Component Analysis (PCA) representing variation in emergence time and proportion of emergence in the controlled chamber and in the open field indicating a trend to lower emergence in large and extra-large seeded genotypes. Screening of seedling emergence and phenotypic response of the bean germplasm under a range of temperatures in controlled growth chambers and under field conditions showed several genotypes, as landraces 272, 501, 593, and the cultivar Borlotto, with stress-tolerance at emergence, and high yield potential that could be valuable genetic material for breeding programs. Additionally, the potential genetic erosion in genebanks was assessed. Regarding bean commercial traits, under low temperature at sowing time seed reached larger size, and crop yield was higher compared to warmer temperatures at the sowing time. Therefore, early sowing of bean is strongly recommended. © 2016 De Ron, Rodiño, Santalla, González, Lema, Martín and Kigel.

Nitrophilic thistles such as milk thistle (Sylibum marianum) and Syrian thistle (Notobasis syriaca) encroach rangeland areas where animals gather and defecate, in particular around watering and feeding points. High densities of milk and Syrian thistles (MST) diminish forage yields and detract from the amenity value of these areas. The aims of the present study were: (i) to test the safety of feeding MST to adult goats; (ii) to determine if preconditioning adult goats to MST, by feeding it indoors together with concentrate, enhances preference for MST when they graze MST-rich pastures; and (iii) to test for generational transfer by comparing the propensity to consume MST and the preference for MST over clover hay for weaned kids that previously suckled from does that were, or were not, preconditioned to consume MST fed as green fodder. We found that eating MST was not toxic to adult goats. Over six observation sessions of one hour, preconditioned goats devoted 50% more time to consuming MST than non-conditioned counterparts (30.3% versus 20.6%, respectively; P = 0.0005), and kids that experienced the preconditioning period together with their does tended (P = 0.08) to show a greater preference for MST over clover hay than their counterparts born to non-conditioned adults. Although the efficacy in depleting the seed bank has yet to be verified, from the point of view of the animal, goats may be used in targeted grazing of milk and Syrian thistles. © 2016 Elsevier B.V.