Zygophyllum Dumosum Research Articles

Soil Microbial Population in the Vicinity of the Bean Caper ( Zygophyllum dumosum) Root Zone in a Desert System

The aim of the current study was to gain a better understanding of the changes in soil microbial biomass and basal respiration dynamics in the vicinity of the bean caper ( Zygophyllum dumosum) perennial desert shrub and the inter-shrub sites. Microbial biomasses as well as basal respiration were found to be significantly greater in the soil samples taken beneath the Z. dumosum shrubs than from the inter-shrub sampling sites, with no differences between the two sampling layers (0-10 and 10-20 cm) throughout the study period. However, seasonal changes were observed due to autumn dew formation, which significantly affected microbial biomass and basal respiration in the upper-layer inter-shrub locations. The calculated metabolic coeffcient ( qCO 2) revealed significant differences between the two sampling sites as well as between the two soil layers, elucidating the abiotic effect between the sites throughout the study period. The substrate availability index was found to significantly demonstrate the differences between the two sites, elucidating the significant contribution of Z. dumosum in food source availability and in moderating harsh abiotic components. The importance of basal microbial parameters and the derived indices as tools demonstrated the importance and need for basic knowledge in understanding plant-soil interactions determined by an unpredictable and harsh desert environment.

Seasonal Changes in Free-Living Amoeba Species in the Root Canopy of Zygophyllum dumosum in the Negev Desert, Israel

The influence of seasonality and Zygophyllum dumosum root canopy on the species diversity of free-living amoebae at two soil depths (0-10 and 10-20 cm) was studied in a Negev Desert ecosystem in Israel. Free-living amoebae were extracted and identified after cultivation in non-nutritive agar plates. A total of 90 amoeba species were identified in the soil during the study period, with the most common genera present being Hartmannella, Platyamoeba, Vahlkampfia, Acanthamoeba, and Echinamoeba. Differences between the control soil and the soil under Z. dumosum were found mainly during the dry seasons, when 97% similarity was found between the two soil layers, which could be due to the effect of the shrub on the soil microenvironment. The amoeba community exhibited more species diversity in spring (reaching a value of 34 species) than in the winter (18 species) or summer and autumn (20 species), since the community has a time lag for becoming stabilized after the dry summer and autumn. This is one of the first studies on the amoeba population in the Negev Desert and elucidates the importance and the need for taking trophic and functional groups into consideration in order to understand biomineralization processes.

Seasonal dynamics of amoebae in the root canopy of Zygophyllum dumosum in the Negev Desert, Israel

Water availability and nutrient limitation are the most important driving forces in hot desert ecosystems, determining vegetation cover and biological activity. In this study the amoeba population was determined in the upper soil layer (0–10 and 10–20 cm) under and between 4 individual Zygophyllum dumosum shrubs. The soil samples were taken from the different layer beneath the shrub and between the shrubs (control) along four seasons. Total number of amoeba was significantly higher in the Z. dumosum root canopy (2935 individual/g soil) in comparison to control samples (625 individual/g soil). Amoebal density was highest at 10–20 cm during the winter, spring and summer. In autumn, during heavy dewfall amoebal density was greatest in the top 10 cm of soil.

Spatial and temporal dynamics of nematode populations under Zygophyllum dumosum in arid environments

Soil nematode activity in arid ecosystems is determined by well-known limiting factors such as soil moisture and organic matter. The main aim of our investigation was to determine the composition and distribution of the nematode community in response to soil water and organic content in the rhizosphere of the perennial plant Zygophyllum dumosum. The results demonstrated that soil moisture, organic matter, total nematode population and trophic groups differed under the plants and in the control samples. Significant differences in soil moisture, total nematode population and trophic groups were observed. Bacterial-feeders were found to be the dominant nematode trophic group at the research sites. Bacterial- and fungi-feeders were present in the upper 0–10 cm layer during most of the year. A negative correlation was found between nematodes and soil moisture and a positive correlation was found between nematodes and organic matter. Moreover, trophic structure changes and quantity changes in the nematode community were observed within 1 month after quantitative changes occurred in the organic matter. Generally accepted nematode fauna indices such as Wasilewska index (WI), F/B, T, H′, λ, species richness (SR), PPI, maturity index (MI), and modified maturity index (MMI), reflect the temporal changes that occurred in the nematode community during the research period. This study illustrates the integrated effect of soil moisture and organic matter on the activity and structure of the nematode communities existing under plants.

Temporal and spatial dynamics of vesicular-arbuscular mycorrhizal fungi under the canopy of Zygophyllum dumosum Boiss. in the Negev Desert

The temporal and spatial dynamics of vesicular–arbuscular mycorrhizal (VAM) fungi were investigated in a desert ecosystem. Soil samples under the canopy of Zygophyllum dumosum were collected monthly between November 1999 and October 2000 from 0–10 and 10–20 cm depths. VAM fungal colonization and spore density were used to compare the responses of VAM fungi to soil conditions. The mean percent colonization and spore density of VAM fungi reached maximal values in November 1999 and September 2000. Soil moisture was positively correlated with colonization of VAM structure groups. Vesicular and arbuscular colonization were positively correlated with soil organic matter and total soluble N. Spore density was also positively correlated with total soluble N. Our results suggest that spore density and the extent of vesicular and arbuscular colonization are useful indicators for evaluating changes in desert soil ecosystems.

Seasonal variation in the nematode communities associated with two halophytes in a desert ecosystem

Seasonal variation in the soil nematode communities was investigated in a field study at the Avdat Research Farm, Israel. Soil samples from 0-10 cm soil were collected monthly between May 1998 and May 2000, under the canopy of two halophyte shrubs: Hammada scoparia. and Zygophyllum dumosum. Ecological indices such as ratio of fungivores and bacterivores to plant parasites (WI), fungivore to bacterivore ratio (F/B), trophic diversity (TD), Shannon index (W), dominance (X) and richness (SR) were assessed and compared between treatments and between seasons. Twenty nematode families and 26 genera were observed. Acrobeles, Cephalobus, Aphelenchoides and Rhabditidae were found to be the dominant genera/family. Significant differences were found between seasons (P<0.01) in the number of total nematodes, the four trophic groups and the indices, WI, T, H', lambda, and SR. Bacterivores were found to be the most abundant trophic group in four seasons, their mean relative abundance was 60.6 % of the nematode community. Among ecological indices tested, F/B and lambda were effective in distinguishing differences in nematode community structure between treatments during the study period.

Soil Characteristics of Crusted outside and Subcanopy Areas of four Dominant Shrubs in the Negev Desert

It has been proposed that there are functional source-sink relationships between two patch types (microbiotic crusts and shrubs) in drylands. Crust patches supply runoff water and resources which shrub patches accumulate, thereby becoming loci of productivity and diversity. This study compared some soil characteristics under shrubs and outside to determine how these soil parameters relate to the source-sink model. Four shrubs dominant in the area namely: Zygophyllum dumosum, Hammada scoparia, Atriplex leucocladaandThymelea hirsuta were investigated. The results on compaction, salinity, pH, water holding capacity, respiration and organic carbon supported the model. The crust:shrub ratio is crucial for the functioning and sustained productivity of the system. Keywords: Soil characteristics; shrub subcanopy; crust; sink-source, Negev desert [IJARD Vol.3 2002: 162-170]

Spatial Distribution and Colonization of Arbuscular Mycorrhizal Fungi under the Canopies of Desert Halophytes

Despite the evident importance of arbuscular mycorrhizal fungi associated with the root system of plants inhabiting desert regions, the distribution and activity of arbuscular mycorrhizal fungi in desert ecosystems is not well known. In this study, the spatial distribution and colonization of arbuscular mycorrhizal fungi were investigated in a field study in the Negev Desert of Israel. Soil samples from depths of 0-10, 10-20, 20-30, 30-40, and 40-50cm were collected under the canopies of Zygophyllum dumosum, Hammada scoparia, Artemisia herba-alba , and Atriplex halimus . Spore density and association of vesicular root system with arbuscular mycorrhizal structure groups such as vesicles, arbuscules, and hyphae were used to assess and compare the responses of arbuscular mycorrhizal fungi to plant cover and their abiotic environment. Different plant cover significantly affected arbuscular mycorrhizal fungal colonization and spore density. Higher spore density tended to be correlated with higher arbuscular mycorrhizal colonization under A. herba-alba and A. halimus , and vice versa for Z. dumosum and H. scoparia . At the tested soil depths, the highest arbuscular mycorrhizal colonization at the 20-30cm depth did not coincide with higher spore density at the 10-20cm depth. Sampling depth had a significant effect on spore density and the percentage of total arbuscular colonization. Spore density was positively correlated with vesicular colonization and negatively correlated with arbuscular colonization. Soil total soluble N exhibited a negative effect on spore density, while soil water content and organic matter content did not exhibit a significant correlation with arbuscular mycorrhizal fungal colonization and spore density.

GRANIVORY AND PLANT SELECTION BY DESERT GERBILS OF DIFFERENT BODY SIZE

Plant selection, energy intake, and digestibility were studied in nonreproducing Gerbillus henleyi (10 g; n = 9), Gerbillus dasyurus (24 g; n = 6), and Meriones crassus (90 g; n = 9). These gerbils coexist in the Negev Desert Highlands, have similar dietary habits (being primarily granivores), and do not require drinking water, but they differ greatly in body mass. Each species was offered different levels (0% and ∼40% and 80% of maintenance energy requirements) of millet seeds and ad libitum fresh vegetation consisting of Atriplex halimus, Moricandia nitens, Zygophyllum dumosum, Lycium shawii, Anabasis articulata, and Thymelaea hirsuta, the dominant plants in the area inhabited by the rodents. Drinking water was not available. We hypothesized that: (1) smaller animals would be more dependent than larger animals on highly digestible food items such as seeds, and (2) smaller animals would be more selective than larger animals for highly digestible and energy-rich plant parts. The minimum levels of millet seeds needed to maintain body mass were 97%, 94%, and 36% of maintenance energy requirements for G. henleyi, G. dasyurus, and M. crassus, respectively. Therefore, G. henleyi was the most dependent on seeds, and M. crassus the least, supporting hypothesis 1. At similar levels of seeds consumed, apparent digestibilities of dry matter (DMD) and energy of the total diet were highest for G. henleyi. In the absence of seeds, vegetation DMD averaged 88% in G. henleyi and 70% in M. crassus, yet G. henleyi lost body mass, as a percentage, twice as fast as M. crassus. The three rodent species were selective in consuming vegetation and made similar choices. A. halimus and M. nitens were preferred, comprising ∼48%, 64%, and 67% of total plant dry matter consumption in G. henleyi, G. dasyurus, and M. crassus, respectively. Plant species not selected were relatively low in water and protein contents and were high in phenolic compounds and condensed tannins compared to preferred species. Gross energy, ash, and fiber levels did not appear to affect selectivity. Selection of plant parts within each plant species, as indicated by the leaf:stem (L:S) ratio, differed among rodent species. The L:S ratio for A. halimus was 4.8, but the L:S ratios ingested were 1.7, 4.0, and 7.4 in G. henleyi, G. dasyurus, and M. crassus, respectively, indicating selection of stems by G. henleyi, selection of leaves by M. crassus, and basically no selection by G. dasyurus. The ratio of seed:green vegetation (S:G) intake was highest in G. henleyi and lowest in M. crassus. A similar inverse relationship between body mass and S:G ratio within seasons was found in other Old World and New World free-living granivorous desert rodents.

A New Sulfated Flavonoid fromZygophyllum Dumosum

Abstract A new sulfated flavonol glycoside isorhamnetin 3-O-(4″-sulfatyl-rutinoside) (1) was isolated from the aerial parts of Zygophyllum dumosum, and its structure was determined by spectroscopic analysis and comparison with data for isorhamnetin 3-O-rutinoside (2), a compound also obtained from the same plant.

Microbial biomass reflects a nitrogen and phosphorous economy of halophytes grown in salty desert soil

Seasonal variations in soil salinity were recorded under the canopy of two halophyte shrubs typical of the hot, dry Negev desert, Zygophyllum dumosum and Reaumuria negevensis. The effects of the fluctuating soil salinity levels on total soluble N and on microbial biomass N and P were also monitored. The microhabitat of the shrubs showed differences in trend and magnitude of soil mineral N, the NOinf3sup-:NH4+ratio, and microbial N and P. The trends were assumed to be governed by the various mechanisms operating in the shrubs in order to survive salty environments. Data from the current study are discussed in terms of the assumption that the halophyte has developed ecophysiological strategies that force microbial communities coexisting in its microhabitat towards adaptation aimed at withstanding a fluctuating environment, and hence towards a beneficial plant-microorganism relationship.

Decomposition of root litter and related microbial population dynamics of a Negev Desert shrub, Zygophyllum dumosum

Decomposition of root litter was studied using roots of the perennial shrub Zygophyllum dumosum , located at three depths (10, 20 and 30 cm). There were three diameter classes (1–3; 4–8; 9–16 mm) used during two consecutive years in the Negev Highland Desert, Israel. No significant differences in decomposition rates in root mass losses between the two treatments and years were found. In both treatments there was an annual mass loss of 15·5%, calculated kinetics (k) of 0·18 year −1 , with a turnover time of approximately 17 years. Rates of mass losses of root litter in the Negev Desert were found to be different than those reported for two evergreen shrubs from the Chihuahuan Desert but were found to be comparable to the data reported on Scots pine roots from the SECON research site in Sweden. These results suggest that linkage exists between rainfall (events, amount) events, root diameter, lignin and nitrogen concentration, and biotic activity where water availability is one of the most important regulators of decomposition in the Negev Desert.

Gas exchange of a desert shrub (Zygophyllum dumosum Boiss.) under different soil moisture regimes during summer drought

The effects of soil water potential on photosynthesis and transpiration of whole Zygophyllum dumosum Boiss. shrubs were examined with a field IRGA system during a rainless summer. Daily photosynthesis and transpiration activities were not notably different on a unit phyllode area basis among shrubs at naturally differing soil water potentials. Irrigation of shrubs caused phyllodes to increase significantly in water content and new leaflets to appear. Leaflets had three times as many stomata per unit area (23000 stomata cm-2) as phyllodes (7100 stomata cm-2) but photosynthesis and transpiration rates were not measurably different between irrigated and non-irrigated shrubs on a unit area basis. This finding suggests that sufficient soil moisture will lead to increased carbon uptake of the entire shrub simply because the total area of photosynthesizing tissue increases. Gas exchange rates appear to be controlled solely by atmospheric conditions under the stresses of summer.

Microbial biomass response to seasonal fluctuation in soil salinity under the canopy of desert halophytes

The relationships between seasonal changes in soil salinity and the microbial biomass and activity (represented by the quotient for basal respiration—qCO2) were monitored year-round under the canopy of two halophytes; Zygophyllum dumosum and Reaumuria negevensis, typical of the hot, dry Negev Desert. Fluctuations in soil salinity were assumed to be the result of different ecophysiological strategies employed by the halophytes in order to survive in saline environments. The amount of the microbial biomass was not directly affected by the degree of soil salinity, especially in the R. negevensis microhabitat where the highest biomass (245 μg g−1) was observed in high salty soil (12.8 dS m−1) during the summer. A negative relationship was found between the microbial biomass and qCO2 values, indicating the possibility of channeling organic substrates to metabolic activity aimed at overcoming conditions of temporary stress.

Male-Biased Breeding Site Fidelity in a Population of Northern Shrikes

Northern Shrikes (Lanius excubitor) are the most widely distributed of true shrikes (Laniinae) with a circumpolar breeding range. In Israel, it is a permanent resident (Paz 1987). I studied sex-biased, nest site-fidelity of a population of this species during three breeding seasons (mid-January to mid-June, 1987-1989). The study area was on Sede Zin, a loess-covered plateau, near Sede Boqer (30?52'N, 34047'E; 475 m altitude) in the Negev Desert highlands. The region is arid with mild winters and warm summers. The Sede Zin plateau supports a sparse dwarf-shrub community dominated by Hammada scoparia, Zygophyllum dumosum, Raemuria hirtella, Anabasis syriacus, and Artemesia herbaalba. The major woody species are Tamarix nilotica, Atriplex halimus, Retama raetam, and Thymelaea hirsuta (Danin et al. 1975).

LITTER FALL AND NITROGEN REABSORPTION IN ZYGOPHYLLUM DUMOSUM IN THE NEGEV DESERT

ABSTRACT In 1983–1984 plant litter of Zygophyllum dumosum was collected in traps in the Negev Desert of Israel. The litter was handsorted into leaves, stems, flowers, and fruits. The mean total litter production was 433 g per shrub, about 70 kg ha−1 yr−1 of litter. Leaves were generally the largest litter category constituting 65–74% of the total. The total nitrogen content of the leaves was found to be significantly higher (p < 0.005) than the total nitrogen found in litter traps. Unexpectedly, an increase in total leaf nitrogen content was recorded in 1984 in spite of lower rainfall.

Nematode population dynamics and trophic structure in a soil profile under the canopy of the desert shrub Zygophyllum dumosum

Nematode population dynamics and trophic structure in a soil profile under the canopy of the desert shrub Zygophyllum dumosum

Root-microbial population dynamics in a soil profile under the canopy of the desert shrub Zygophyllum dumosum

A study was carried out to follow root-microbial population dynamics in the soil profile under Zygophyllum dumosum. Root area was greater in the lower soil profile (20–30 cm) during the rainy season, except when the soil was drying out after a period of minimal rainfall. Root production was enhanced in the surface layer (0–10 cm) as the soil dried in the wet season, and throughout the soil profile as the soil dried preceding the dry summer period. This suggests two functional root types exist for Z. dumosum , one which exploits a relatively stable water supply, and another which captures less available, and reliable sources. Soil bacteria populations were relatively stable throughout the study period, whereas fungi and actinomycetes appeared to have an inverse relationship, with fungi increasing after the early rains, while actinomycetes declined. Actinomycetes may be a more important component of the microflora during drought periods, since their numbers were relatively high following 2 years of below-normal rainfall, but never recovered after a year of normal rainfall.

The relationship between some perennial desert plants originated in different phytogeographical regions and proline concentration

It is well established that proline accumulates in plants under osmotic stress. The question addressed in this study was whether or not plants from the arid Saharo-Arabian phytogeographical region, contain more proline than those that originated in the more humid Irano-Turanian region. It was based on the assumption that, under drier conditions, overproduction of proline has been selected in some species as a mechanism for osmoregulation. Large differences in proline concentration were found among species originating from different phytogeographical regions. In a comparison between two summer semi-deciduous species that have a Saharo-Arabian (Zygophyllum dumosum Boiss.) or Irano-Turanian (Artemisia herba-alba Asso.) chorotype, it was found that the former had significantly more leaf proline than the latter. Comparison between two summer deciduous half-shrub species, Helianthemum ventosum Boiss. (Saharo-Arabian) and H. vesicarium Boiss. (Irano-Turanian) showed a higher proline concentration in the former. Only Zygophyllum dumosum showed a high proline concentration throughout the year; hence, it is possible that, in this species, proline may play a more important role in osmoregulation than in the others. Proline concentration is reported in a few species which have a Saharo-Arabian-Irano-Turanian chorotype.

Root and microbial biomass dynamics under the canopy of the desert shrub Zygophyllum dumosum.

A study was done to evaluate the influence of soil moisture and rainfall on root and microbial biomass production under the canopy of the desert shrub Zygophyllum dumosum. During the study period the root biomass production increased following the early rains but subsequently declined, remaining fairly constant thoroughout the season. In contrast microbial biomass and soil organic matter increased during the rainy season and declined with the onset of the dry summer period. Based on our results we suggest that the moisture event and not the amount and the organic matter content regulate root and microbial biomass production at the 0 to 10 cm soil layer.