Celtis Pallida Research Articles

Estudio de la comunidad de oribátidos (Acari: Oribatida) en dos parches de tala (Celtis ehrenbergiana) del sudeste bonaerense

Study of the oribatid mite (Acari: Oribatida) community from two patches of tala (Celtis ehrenbergiana) from the southern of Buenos Aires. “Talares” are xeric forests located along the coast of Buenos Aires province, Argentina. Since >400 years ago, they have been subject of a severe degradation, resulting in a fragmentary landscape of forest patches surrounded by a grassland matrix. The aims of this study were: a) to enhance the knowledge of oribatid mites in the talares, and b) to analyze the effect of habitat fragmentation on diversity, richness, abundance and structure of the oribatid mite community. I analyzed oribatids in three sites: two different-size close forest patches (big: Gr, small: Ch) and the surrounded grassland matrix (Ma) in Laguna de los Padres reserve, Mar del Plata. A total of 51 species of oribatids were identified, with similar values of richness in all sites. Oppiidae y Scheloribatidae were the families with more species. Diversity (H’) was greater in the forest patches (Gr=1.58; Ch=1.59) than in the matrix (Ma=0.91). Density of oribatid mites was higher in Gr (36500 individuals/m2); in Ch and Ma, densities were 50% and 75% lower. This global difference is a consequence of reduced population sizes in most species. According to seasonal variations, in Gr there were more “ubiquitous” species (20) than in Ch y Ma (10). Summarizing, the community of oribatid mites were primarily conditioned by the type of environment (grassland vs. forest), with similar distribution patterns of species but with a marked seasonality in the grassland matrix. Among forest patches, area did affect oribatid mites density through a reduction in most population sizes. The evaluation of the fragility of these populations could be a starting point to undertake conservation programs.

Does Supplemental Feeding of White-tailed Deer Alter Response of Palatable Shrubs to Browsing?

The impact on palatable shrubs when herbivores have access to high-quality food is unclear. We determined if providing high-quality food and increasing white-tailed deer (Odocoileus virginianus) density reduced growth and altered nutritional quality of two palatable shrub species. We maintained target densities of 13, 31, or 50 deer km−2 in six 81-ha−1 enclosures on each of two ranches. We provided nutritious, dry feed ad libitum in one of each pair of enclosures with similar densities on each ranch. We measured height and width of Texas kidneywood (Eysenhardtia texana Scheele) and spiny hackberry (Celtis ehrenbergiana [Klotzsch] Liebm), measured hackberry thorns, and estimated crude protein. Plants were protected from browsing with wire exclosures in 2005; a similar-sized unprotected plant was paired with each protected plant. We estimated density of shrub species using twenty 3 × 50 m belt transects/enclosure June 2005, 2007−2012. Growth of protected and unprotected kidneywood was similar (P ≥ 0.88) at 13 deer km−2, but growth was reduced (P ≤ 0.05) by higher deer densities. Protection from browsing and increasing deer density did not influence (P ≥ 0.25) size of spiny hackberry. Browsed kidneywood plants had a 34% lower crude protein (P ≤ 0.01) compared with protected plants when deer did not have access to feed. Spiny hackberry protein was greater (P ≤ 0.05) in unprotected plants compared with protected plants at 50 deer km−2. Response of Texas kidneywood density at > 1.5-m tall to deer density depended on year (P = 0.04), with no effect of deer density (P ≥ 0.10) on spiny hackberry density. Density of both shrubs was similar (P > 0.14) with and without supplement. Access to feed does not alter effects of browsing on these sympatric shrubs; however, responses to increasing herbivore density contrast. Texas kidneywood is less tolerant of herbivory than spiny hackberry.

Plantación de Celtis ehrenbergiana como técnica de recuperación de bosques invadidos por Ligustrum lucidum en los talares del NE de Buenos Aires

The establishment of alien plants in native ecosystems promotes biodiversity loss and impacts on ecological processes. Reverting that situation may require the remotion of alien species and the plantation of native species. Ligustrum lucidum is a common invasive tree in temperate and subtropical forests in Argentina. This species causes a high increase in the mortality of native trees in forests dominated by Celtis ehrenbergiana (talares). Native trees regeneration is almost null and then, there is no forest recovery. We carried out an experimental adult L. lucidum removal in two 500 m2 and two 200 m2 clearcuts. We planted C. ehrenbergiana produced in a greenhouse inside them, and in a peripheral area under the L. lucidum canopy. We observed higher mean height in the central area (68±3.3) of the clearcuts than in the edge (52.6±1.7) or the peripheral areas under the forest canopy (54.3±2.6). Plants in 500 m2 clearcuts exhibited lower height (53.9±3 and 66.5±4.9 cm) than those in 200 m2 clearcuts (82.6±9.9 and 91.3±8.5 cm). Probably plants in the central area of the clearcuts were subjected to a weak competition, for light and underground resources, in comparison with plants in edges or peripheral areas. It is possible that in the larger clearcuts a higher competitive effect from herbaceous plants combined with higher radiation and lesser wind protection determined a poorer performance of planted C. ehrenbergiana than in the smaller ones. We conclude that the establishment of C. ehrenbergiana in forest invaded by L. lucidum is possible using the applied techniques. The use of the wood of the harvested L. lucidum, which has good properties for different applications, might make more viable the implementation of the techniques evaluated.

Seasonal water relations in four co-existing native shrub species from Northeastern Mexico

ABSTRACTSeasonal xylem water potentials (Ψ, MPa) and their relationship to soil water content and evaporative demand components were studied in the shrub species Acacia amentacea, Celtis ehrenbergiana, Forestiera angustifolia, and Parkinsonia texana var. macra. Predawn (Ψpd) and midday (Ψmd) water potentials were estimated at 15 days intervals, between January 15 and October 30, 2009 using a Scholander pressure bomb at 06:00 h (predawn) and 14:00 h (midday), respectively. During the humid period, Ψpd ranged from −0.30 MPa (C. ehrenbergiana), to −0.90 MPa (P. texana). In contrast, over the driest period, Ψpd varied between −2.18 (P. texana) and −3.94 MPa (F. angustifolia). At midday, P. texana and F. angustifolia showed the highest (−1.14 MPa) and lowest (−3.38 MPa) Ψ values, respectively. Average soil water content accounted for 35 to 70% of the variation in predawn Ψ. Furthermore, both Ψ reflected the environmental conditions, as indicated by typical correlations observed. The studied shrub species exhibited what seem to be different strategies to avoid damage caused by drought. Thus, P. texana behaved rather as an isohydric plant able to deal well with severe, but short periods of drought. Under exceptionally dry environmental conditions, Ψpd undercut Ψmd values. Similar observations have been made by researchers studying plants in dry ecosystems. All studied native species are recommended for reforestation of the Tamaulipan shrublands, although C. ehrenbergiana and F. angustifolia seem to have limited tolerances for extreme water stress.

Fruiting phenology as a “triggering attribute” of invasion process: Do invasive species take advantage of seed dispersal service provided by native birds?

Mechanisms underlying biological invasion of highly disturbed ecosystems are well known, yet mechanisms responsible for biological invasion of undisturbed or weakly disturbed ecosystems are less understood. The triggering attribute (TA) approach, proposed as a mechanism that explains plant invasion success in undisturbed or weakly disturbed systems, considers that the spread of alien species depends on specific vegetative or regenerative traits in invasive species, discontinuously distributed in comparison to the resident community. In mountain Chaco woodland, fruiting phenology of ornithocorous invasive plants has been proposed as a TA, because it would allow invasive species to benefit from seed dispersal service, which is unused by native plants during a specific period of the year (winter). Under the seed dispersal ecology framework, we evaluated if fruiting phenology (fructification largely uncoupled with native species) of the fleshy-fruited invasive Pyracantha angustifolia affects bird fruit consumption, and allows the invasive to take advantage of the unused seed dispersal service during winter. If uncoupled fructification phenology represents a TA, seed disperser, seed predator, and pulp consumer diversity, abundance, and fruit consumption on P. angustifolia (which fructifies in winter), will be higher than on its exotic congeneric P. coccinea during summer, when fructification overlaps with native Celtis ehrenbergiana and many other native species. We found that: (1) disperser bird abundance and fruit consumption did not differ between P. angustifolia and P. coccinea; (2) the most diverse frugivorous assemblage was observed on C. ehrenbergiana, yet it had the lowest proportion of seed dispersers and the highest fruit consumption by seed predators and, (3) we also observed higher proportion of seed predators on P. angustifolia (uncoupled fructification scenario) than on P. coccinea (coupled fructification scenario). Our results suggest that invasive uncoupled fructification phenology does not represent a true TA which facilitates plant invasion processes in undisturbed or weakly disturbed ecosystem.

Use of Anthropogenic Nest Substrates by Crested Caracaras

Caracara cheriway (Crested Caracara) typically nest in Sabal palmetto (Cabbage Palms) in Florida and isolated thorny shrubs (e.g., Celtis pallida [Granjeno]) in Texas. The species has not previously been reported to use anthropogenic nest substrates. We found Crested Caracara nests in an electrical substation, on a radio tower, and on a billboard near Clewiston, FL, and in an electrical substation and on a lattice electrical-transmission tower near Houston, TX. Our observations of nesting on anthropogenic substrates may support 3 distinctly different inferences. First, the behavior could be ongoing but not previously reported. Second, because individual Crested Caracaras in breeding plumage persist for years as floaters, novel use of anthropogenic nest substrates may indicate adult Caracaras seeking any possible nesting opportunity, even if nest success is low. Third, Crested Caracaras may be modifying their breeding behavior to capitalize on high-quality resources in areas that lack traditional nest substrates. Comparison of productivity between nests on anthropogenic and natural substrates would resolve the latter 2 competing hypotheses. Because management focuses primarily on nest sites, novel nesting-behavior could have important management implications. Future research should quantify productivity on anthropogenic substrates and document whether individuals produced at these sites tend to return to anthropogenic substrates to breed.

Effect of increasing levels of seven tree species extracts added to a high concentrate diet on in vitro rumen gas output.

This study was conducted to investigate the effects of increasing levels of extracts of Byrsonima crassifolia, Celtis pallida, Enterolobium cyclocarpum, Fraxinus excelsior, Ficus trigonata, Phoradendrom brevifolium and Prunus domestica on in vitro gas production (GP) and ruminal fermentation of a high concentrate diet. Plant extracts were prepared at 1 g dry matter (DM)/8 mL of solvent mixture (methanol : ethanol : water, 1:1:8) and added at levels of 0, 0.6, 1.2 and 1.8 mL/g DM of a high concentrate diet. In vitro GP was recorded at 2, 4, 6, 8, 10, 12, 24, 48 and 72 h of incubation. Increasing addition of extracts linearly increased (P < 0.001), the GP24 , GP48 and GP72 (mL/g DM), and linearly decreased (P < 0.001), the discrete GP lag time. Moreover, increasing extract doses linearly increased (P < 0.001) the asymptotic GP and decreased (P < 0.001) the rate of GP. GP6 was not impacted by treatments and GP12 increased linearly (P = 0.01) with increasing addition of extracts. Rumen pH declined linearly (P < 0.05) with increasing doses of extracts added. As no interactions (P > 0.05) occurred between the extracts and doses, it could be conclude that all extracts positively modified rumen fermentation at doses of 1.2 to 1.8 mL extract/g diet DM.

Plant water use characteristics of five dominant shrub species of the Lower Rio Grande Valley, Texas, USA: implications for shrubland restoration and conservation.

The biogeographic distribution of plant species is inherently associated with the plasticity of physiological adaptations to environmental variation. For semi-arid shrublands with a legacy of saline soils, characterization of soil water-tolerant shrub species is necessary for habitat restoration given future projection of increased drought magnitude and persistence in these ecosystems. Five dominant native shrub species commonly found in the Lower Rio Grande Valley, TX, USA, were studied, namely Acacia farnesiana, Celtis ehrenbergiana, Forestiera angustifolia, Parkinsonia aculeata and Prosopis glandulosa. To simulate drought conditions, we suspended watering of healthy, greenhouse-grown plants for 4 weeks. Effects of soil salinity were also studied by dosing plants with 10% NaCl solution with suspended watering. For soil water deficit treatment, the soil water potential of P. glandulosa was the highest (-1.20 MPa), followed by A. farnesiana (-4.69 MPa), P. aculeata (-5.39 MPa), F. angustifolia (-6.20 MPa) and C. ehrenbergiana (-10.02 MPa). For the soil salinity treatment, P. glandulosa also had the highest soil water potential value (-1.60 MPa), followed by C. ehrenbergiana (-1.70 MPa), A. farnesiana (-1.84 MPa), P. aculeata (-2.04 MPa) and F. angustifolia (-6.99 MPa). Within the species, only C. ehrenbergiana and F. angustifolia for soil water deficit treatment and A. farnesiana for the salinity treatment had significantly lower soil water potential after 4 weeks of treatment (P < 0.05). We found that soil water potential, stomatal conductance and net photosynthesis of the species significantly reduced over time for both treatments (P < 0.05). We conclude that while all species exhibited capacities to withstand current water availability, some species demonstrated limited tolerance for extreme water stress that may be important for management of future shrub diversity in Lower Rio Grande Valley.

Annual activity density of groundbeetles (Coleoptera: Carabidae) of a Celtis ehrenbergiana (Rosales: Celtidaceae) forest of Buenos Aires province, Argentina.

The aim of this study was to describe the annual activity cycle, the sex ratio, and the relationship between the weather variables and activity density of the 16 most abundant carabid species of a typical southeastern region of Pampasia, Argentina. The study focused on the southernmost Celtis ehrenbergiana (Klotzsch) Liebmann ( = C. tala Guillies ex Planch) native forest of the region, from March 2008 to March 2009, a period during which there was a marked draught associated with the La Niña phenomenon. Forty-five pitfall traps were emptied once every 2 wk, and the occurrence of larvae, tenerals, and subtenerals was recorded. Photoperiod, temperature, and precipitations explained 35% of the total variation in the catch. Total carabid activity was high in early autumn and late spring. Eight species reached their maximum activity in spring, five in winter, two in summer, and one in autumn. Possible reproductive strategies, the influence of different variables involved in the life cycles of the species, and the sex ratio and their limitations are discussed. RESUMEN El objetivo de este trabajo fue describir la proporción de sexos, el ciclo de actividad annual, la relación entre las variables meteorológicas y la actividad de las 16 especies más frecuentes de carábidos de una región típica del sudeste de la Pampasia, Argentina. El trabajo se enfocó en el talar, C. ehrenbergiana (Klotzsch) Liebmann ( = C. tala Guillies ex Planch), más austral de la región, durante marzo 2008-marzo 2009, período marcado por una sequía asociada con el fenómeno La Niña. Se utilizaron 45 trampas “pitfall” recambiadas quincenalmente. Se registró la presencia de larvas, tenerales y subtenerales. El fotoperíodo, la temperatura y las precipitaciones explicaron el 35% de la variación en el número de total de individuos. La actividad total de los carábidos fue alta en otoño temprano y primavera tardía. Ocho especies alcanzaron el pico de máxima actividad en primavera; cinco en invierno; dos en verano y una en otoño. Se discuten posibles estrategias reproductivas, la influencia de las variables involucradas en los ciclos de vida de las especies y la proporción de sexos y sus limitaciones.

Directness and tempo of avian seed dispersal increases emergence of wild chiltepins in desert grasslands

Summary Seed dispersal is thought to be unpredictable and outside a plant's control. But directed seed dispersal by mutualistic birds can increase probabilities of germination and survival by the non‐random deposition of seeds in suitable microhabitats. In the Sonoran Desert grasslands of southern Arizona (USA), bird‐dispersed wild chiltepin peppers (Capscium annuum var. glabriusculum) grow in non‐random association under bird‐dispersed nurse trees and shrubs that serve as perches. We tested the hypothesis that the pattern is maintained by directional avian seed‐dispersal patterns. Alternatively, post‐dispersal processes, such as differential seed predation and seedling mortality, could create the associations. For 3 years, we sampled the bird‐generated seed rain under desert trees in four chiltepin subpopulations, comparing seed dispersal into microhabitats of fleshy‐fruited trees and non‐fleshy‐fruited trees. Celtis pallida (fleshy‐fruited) and Prosopis vellutina (non‐fleshy‐fruited) trees accounted for &gt; 90% of the cover available for chiltepin recruitment. We tracked seedling emergence and survival in the two microhabitats and conducted a controlled seed‐addition experiment to measure the effects of microhabitat, seed‐addition density and temporal seed deposition on chiltepin emergence, growth and survival. Approximately twice as many bird‐dispersed seeds arrived at fleshy‐fruited microhabitats compared with non‐fleshy microhabitats. The numbers of seeds arriving and the number of seedlings emerging in microhabitats the following year were positively correlated. Survival of naturally emerged seedlings was similar at both microhabitats, but the seed‐addition experiment revealed that more seeds are able to emerge under the denser foliage of fleshy‐fruited microhabitats. The experiment also shows a significant effect of temporal deposition: when seeds were added gradually in a microhabitat (emulating repeated avian seed deposition under perches) instead of all at once, seedling emergence increased twofold on average. Synthesis: Birds dispersed disproportionally high quantities of chiltepin seeds into favourable recruitment microhabitats, showing a case of directed dispersal. Birds also increase seedling emergence through the temporal deposition of seeds under fleshy‐fruited trees, most likely as a result of reducing the odds of seed predation. A coupling between directed seed dispersal with classic facilitative plant–plant interactions leads to the formation of pattern and self‐organization in a plant community.

Trace elements in native shrubs consumed by white-tailed deer (Odocoileus virginianus) in northeastern Mexico

The contents of Cu, Fe, Mn, and Zn were seasonally determined in the leaves of the native shrubs – Castela erecta, Celtis pallida, Forestiera angustifolia, Lantana macropoda, and Zanthoxylum fagara – that are browsed by the white-tailed deer (Odocoileus virginianus). The study was conducted at the Tamaulipan thornscrub region, northeastern Mexico, between summer 2004 and spring 2006. Leaf tissues were collected from three county sites (China, Linares, and Los Ramones). Mineral contents were measured using an atomic absorption spectrophotometer. All minerals, in all plants, were significantly different among sites, seasons, and years, as well as the double and triple interactions. In general, plants at the Linares site, that had the highest rainfall, had higher trace element content. Moreover, during the second year, all plant species were higher in micromineral content. Furthermore, during summer were also higher. Regardless of spatiotemporal variations, all plants had suitable levels of Fe and Mn to satisfy the adult range of white-tailed deer requirements. The Cu and Zn presented marginal deficiency in some plants especially during dry seasons (winter and spring). Seasonal variations in minerals could be associated to soil water deficits, excessive irradiance during summer, and extreme low temperatures during winter and spring that could have affected leaf development and micromineral concentrations.

Morfo-anatomía de las hojas de Celtis ehrenbergiana (Celtidaceae) desarrolladas bajo condiciones naturales de sol y sombra

El objetivo del presente trabajo fue establecer las características de las hojas de Celtis ehrenbergiana (Klotzsch) Liebm. (Celtidaceae), desarrolladas bajo condiciones naturales de sol y de sombra. Se estudiaron hojas maduras tomadas de ramas ubicadas en la parte media de la copa del árboly entre la quinta y séptima hoja desde el ápice. Las hojas de sombra son herbáceas, con lámina delgada de color verde claro; la estructura es bifacial, la epidermis presenta células con paredes anticlinales ondulado-sinuosas, el mesófilo está formado por parénquima en empalizada adaxial y esponjoso abaxial y el colénquima es angular-lagunar. Las hojas de sol son coriáceas, con lámina gruesa de color verde oscuro; la estructura es equifacial, la epidermis presenta células con paredes anticlinales rectas, el mesófilo es homogéneo en empalizada y el colénquima angular-masivo. En las hojas de sombra en la cara adaxial, no hay estomas o éstos son escasos, mientras que en las hojas de sol son numerosos. La variación de los caracteres morfo-anatómicos de la hoja evidenció la plasticidad fenotípica de esta especie.

Chemical composition, antioxidant activity and bioactive compounds of vegetation species ingested by goats on semiarid rangelands

The first goal of this study was to evaluate the chemical com- position of vegetation consumed by goats on semiarid rangelands. Secondly, antioxidant activity and identified bioactive compounds of this vegetation were estimated. Twenty-five samples were analysed, including leaves, stems, fruits, or a combination of them. Chemical composition demonstrated large differenc- es among species and smaller differences within species. Some species had high protein contents, e.g. Acacia schaffneri, Celtis pallida and Prosopis lae- vigata. Methanol:water was the best solution to extract bioactive compounds, which we found in larger amounts in complete plants and stems than in fruits and leaves. A. farnesiana pods had the largest polyphenol contents, whereas A. farnesiana, A. schaffneri, Leptochloa dubia and others showed the best an- tioxidant activity. A positive correlation was observed between antioxidant ac- tivity and polyphenol-flavonoid concentration. Based on these results, it seems necessary to study in more detail some species, e.g. the fruits of Acacia far- nesiana and A. schaffneri, to better understand their implications for ruminant feeding and nutrition.

Shrub biomass estimation in the semiarid Chaco forest: a contribution to the quantification of an underrated carbon stock

The quantification of biomass of woody plants is at the basis of calculations of forest biomass and carbon stocks. Although there are well-developed allometric models for trees, they do not apply well to shrubs, and shrub-specific allometric models are scarce. There is therefore a need for a standardized methodology to quantify biomass and carbon stocks in open forests and woodlands. To develop species-specific biomass estimation models for common shrubs, as well as a multispecies shrub model, for the subtropical semiarid Chaco forest of central Argentina. Eight shrub species (Acacia aroma, Acacia gilliesii, Aloysia gratissima, Capparis atamisquea, Celtis ehrenbergiana, Larrea divaricata, Mimozyganthus carinatus, and Moya spinosa) were selected, and, on average, 30 individuals per species were harvested. Their total individual dry biomass was related with morphometric variables using regression analysis. Crown area as well as crown-shaped variables proved to be the variables with the best performance for both species-specific and multispecies shrub models. These allometric variables are thus recommended for standardized shrub biomass assessments. By accounting for the shrub component of the vegetation, our models provide a way to improve the quantification of biomass and carbon in semiarid open forest and woodlands.

Chemical composition and digestion of shurbs browsed by white-tailed deer (odocoileus virginianus texanus)

The aim of the study was to determine, seasonally, the nutritional value of the native shrubs: Acacia amentacea, Castela erecta, Celtis pallida, Croton cortesianus, Forestiera angustifolia, Karwinskia humboldtiana, Lantana macropoda, Leucophyllum frutescens, Prosopis laevigata, Syderoxylon celastrinum and Zanthoxylum fagara. Leave samples were collected seasonally during 2 years from Summer 2004 to Spring 2006 in three county sites: China, Linares and Los Ramones in the state Nuevo Leon, Mexico and evaluated for the content of their Crude Protein (CP), Neutral Detergent Fiber (NDF) and Acid Detergent Lignin (ADL). Dry Matter Digestibility (DMD) was also estimated. The CP content (range of total means = 13-22% dry matter) in most plants significantly varied among sites and seasons and between years. The same pattern occurred for NDF (40-55), ADL (8-22) and DMD (48-73). Celtis pallida had the highest nutritional value. However, due to their high CP and DMD and low NDF and ADL all studied plants in all sites, most seasons and years may be considered as good food sources for white-tailed deer.

Oral administration of leaf extracts to rumen liquid donor lambs modifies in vitro gas production of other tree leaves

This study was conducted to determine if adaptation of lambs to ingestion of tree leaf extracts of Salix babylonica and Leucaena leucocephala can modify in vitro gas production of Celtis ehrenbergiana, Ficus trigonata, Fraxinus excelsior and Prunus domestica. Samples of leaves were collected in triplicate (i.e., three individual samples of each tree leaf). Rumen inoculum was collected from 8 growing lambs fed a total mixed ration ad libitum (control; RC). Incubations were repeated with the rumen fluid collected from another 8 growing lambs of the same breed fed the same ration, but fed a daily dose of 30ml/d of S. babylonica and L. leucocephala extracts in a 1:1 (v:v) mixture (treatment; RX). Leaf samples were incubated with each rumen fluid (i.e., RC and RX inoculums) in 3 runs on different weeks. Data of each of the three runs within sample replicate were averaged and used as the mean value of each individual sample within tree species for statistical analysis in a 4 (tree species)×2 (rumen inoculum) factorial design. In vitro gas production was recorded at 2, 4, 6, 8, 10, 12, 24, 48 and 72h of incubation. After 72h, the incubation was stopped and supernatant pH was determined, and then filtered to determine apparent degraded substrate (ADS). Fermentation parameters, such as the 72h partitioning factor (PF72), 24h gas yield (GY24), in vitro organic matter digestibility (IVOMD), metabolizable energy (ME), short chain fatty acids concentration (SCFA), and microbial protein production (MP) were estimated. The crude protein content of the leaves ranged from 147 (F. trigonata) to 241 (C. ehrenbergiana) g/kg dry matter. The lowest fiber fraction values was in P. domestica, while F. excelsior had the highest, and C. ehrenbergiana and F. trigonata were intermediate. Secondary metabolites (i.e., total phenolics, saponins, aqueous fraction) were lowest in P. domestica and highest in F. trigonata. Accumulated gas production was highest (P<0.05) in F. excelsior during the first 24h of incubation. All fermentation parameters (i.e., ADS, SCFA, GY24, PF72, IVOMD, ME, MP) varied (P<0.01) among tree leaves. The ADS, SCFA and MP were highest (P<0.01) in F. excelsior, lowest (P<0.01) in F. trigonata, and intermediate in P. domestica and C. ehrenbergiana. Incubation of tree leaves with RX inoculum did not affect gas production in the first 6h, but it was lower (P<0.05) at 24–72h, except for F. trigonata. C. ehrenbergiana had the highest (P<0.05) potential gas production, but rate of gas production and the discrete lag time did not differ among leaves. As incubation of tree leaves with RX inoculum lowered (P<0.05) all fermentation parameters, oral administrated extracts of S. babylonica and L. leucocephala did not seem to adapt the rumen microbial population to better utilize these tree leaves.

Mineral content in range forages from north Mexico

Native forages such as trees Quercus eduardii and Quercus grisea; shrubs such as Atriplex canescens, Acacia constricta, Acacia shaffneri, Cassia wislizeni, Celtis pallida, Condalia lycioides, Cordia parvifolia, Flourencia cernua, Larrea tridentata, Mimosa biuncifera and Prosopis leavigata; forbs such as Coldenia greggii, Dalea bicolor, Jatropha dioica and Parthenium incanum; cacti such as Opuntia imbricata, Opuntia leptocaulis and Opuntia leucotricha; red and white fruits from O. leucotricha; fruits from O. leptocaulis, O. imbricata and A. canescens; pods from P. leavigata; pods from A. shaffneri and flowers from Yucca spp. were collected to estimate and compare the mineral content. Plant samples were collected during the dry and wet seasons of two consecutive years (2006–2007) at seven locations situated in four counties of the state of Durango, Mexico. All macrominerals and trace elements were significantly different among plants within each group of plants. The Ca, Mg, K, Fe and Mn content of most plants were in sufficient amounts to satisfy adult range requirements; however, P, Na, Cu and Zn resulted with marginal deficiencies.

POTENCIAL HÍDRICO XILEMÁTICO EN CUATRO ESPECIES ARBUSTIVAS NATIVAS DEL NORESTE DE MÉXICO

Since water stress is the most limiting factor in this region, the aim of the current study was to establish how the xylem water potential (Ψ) in native shrubs such as Celtis pallida (Ulmaceae), Acacia amentacea (Leguminosae) Forestiera angustifolia (Oleaceae), and Parkinsonia texana (Leguminosae) is influenced by soil water content, air temperature, relative humidity, and rainfall. The study was carried out in an area located the municipality of China, state of Nuevo Leon. Using a Scholander pressure bomb the Ψ were estimated at 15 days intervals between January 15 and September 28, 2009 in five different plants per species at 06:00 h (predawn) and 14:00 h (midday). At the wettest period, Ψ oscillated from -0.30 (C. pallida) to -0.90 MPa (P. texana) at predawn, in contrast, at the driest period, Ψ oscillated from -2.18 (P. texana) to -3.94 MPa (F. angustifolia) at predawn. At midday, P. texana and F. angustifolia achieved the highest (-1.14 MPa) and lowest (-3.38 MPa) Ψ values, respectively. Average soil water content at depth profile 0-50cm showed between 82 and 33 % of the variation of Ψ at predawn. Soil water content at different soil depths, and relative humidity were significantly and positively correlated with Ψ at predawn; whereas air temperature and vapor pressure deficit was negatively correlated. A. amentacea and P. texana maintainedhigh values in Ψ at predawn and midday under water stress conditions, so these species may be considered as drought tolerant species.

Composição florística e estrutura da regeneração natural do Parque Estadual do Espinilho, RS

O presente estudo teve como objetivo avaliar a composição florística, diversidade, padrões de distribuição espacial e estrutura da regeneração natural das espécies arbóreas em Savana Estépica Parque, localizada no Parque Estadual do Espinilho, extremo sudoeste do Estado do Rio Grande do Sul, Brasil. Essa tipologia abriga uma vegetação peculiar, não ocorrendo em outras áreas do país, com presença de espécies endêmicas e vulneráveis. Para a análise, foi instalada uma unidade amostral permanente de 4ha (200x200m) subdividida em 400 subunidades de 100m² (10x10m) cada. Dessas, foram sorteadas 60 subunidades, em que todos os indivíduos com altura superior a 30cm e diâmetro ao nível do solo (DNS) tomado a ±03cm de altura, inferior a 9,5cm foram amostrados. Foram encontrados 174 indivíduos, distribuídos em cinco famílias botânicas, seis gêneros e seis espécies. A regeneração natural apresentou Índice de Diversidade de Shannon estimado em 0,82, indicando resultados baixos para a diversidade de espécies. As espécies com maiores valores de importância foram Vachellia caven (Molina) Molina (63,96%) e Celtis ehrenbergiana (Klotzsch) Liebm. (30%). Essas duas espécies apresentaram comportamento agregado, enquanto Prosopis affinis Spreng., espécie característica do parque, obteve comportamento não agregado segundo o Índice de Payandeh. A regeneração natural da área não se encontra balanceada, entretanto segue o modelo "J invertido", apresentando déficit de indivíduos na classe inicial de diâmetro, possivelmente devido ao pastoreio atualmente realizado no local.

Xylem water potentials of native shrubs from northeastern Mexico

Xylem water potentials (Ψ) were evaluated in browse plants such as Forestiera angustifolia (Oleaceae), Celtis pallida (Ulmaceae), Zanthoxylum fagara (Rutaceae), and Eysenhardtia texana (Fabaceae). Collections were carried out at Linares County, a semi-arid region of northeastern Mexico. Ψ (MPa) were estimated at 10-day intervals between July 10 and September 30, 2008 by using a Scholander pressure bomb, and were monitored in five different plants per species at 06:00 h (predawn) and 14:00 h (midday). Air temperature, relative humidity, precipitation, and soil water content were registered throughout. Data were subjected to one-way ANOVA and linear correlation analysis. At the wettest period, Ψ at predawn varied from − 0.29 (C. pallida and E. texana) to − 0.37 (F. angustifolia and Z. fagara); in contrast, at the driest period, predawn Ψ ranged from − 3.28 (F. angustifolia) to − 4.50 (Z. fagara). At midday E. texana achieved the highest (−1.14) and lowest (−4.20) values at wettest and driest sampling dates, respectively. It seems that air temperature and vapor pressure deficit negatively influenced Ψ values in all species; conversely, Ψ values augmented as relative humidity increased. Since F. angustifolia and C. pallida maintained higher predawn and midday Ψ values under water stress, these species may be considered as drought-adapted species while, Z. fagara and E. texana that acquired lower values, may be less adapted to drought and in physiological disadvantage under limited water conditions.