Prostrate Species Research Articles

Dunal plants as sink for anthropogenic marine litter: The entrapping role of Salsola kali L. (1753) in a Mediterranean remote beach (Sardinia, Italy)

The ability to retain anthropogenic marine litter by a halo-psammophilous plant formation dominated by a single prostrate species (Salsola kali) on a Sardinian beach was measured. We hypothesized that the anthropogenic litter (i) is trapped by plants to a greater extent than in control areas, and (ii) has more elongated size, mimicking the organic Posidonia wrack, largely occurring locally as ‘banquettes’. Salsola kali patches show an apparently higher anthropogenic litter density than control sites without vegetation. Salsola kali plants trap litter items significantly longer and a larger number of size length categories than control plots. These effects may be due to the prostrate structure of the plant with small thorns at the apex. Also, litter entrapped by plants can interfere with the mechanisms of dune deposition and structuration, in turn affecting food chains by decreasing the availability of organic material for pedofauna.

An alternative key for identifying three prostrate species of the genus Euphorbia

Plants are a valuable source of different folk and modern medicines. Therefore, correctly identifying the plant species is a prerequisite for using them in the health care system. Euphorbia species are of great medicinal importance but are difficult to distinguish due to the occurrence of ecotypes and a high degree of polymorphism within the species. Therefore, the present study was planned to explore the extent of variations in morphological characters among three Euphorbia species, namely, Euphorbia prostrata Aiton, Euphorbia serpens Kunth and Euphorbia thymifolia L. The edaphic ecotypes red and green forms of Euphorbia prostrata growing separately or adjacent to each other were reported during field surveys. To ensure identification accuracy, illustrated online key was prepared as a supportive tool for the traditional key.

Deferment associated to contrasting grazing intensities affects root/shoot biomass allocation in natural grasslands

AbstractQuestions(i) How does a strategic deferment influence both shoot and root biomass in South American Campos natural grassland after a long time of contrasting livestock grazing intensities? (ii) How do functional strategies of plants to tolerate or avoid grazing affect patterns of aboveground and belowground biomass?LocationA natural Campos grassland in the Central Depression of Rio Grande do Sul State, Southern Brazil (latitude 30°05′27″ S, longitude 51°40′18″ W, and altitude 46 m).MethodsWe studied the effects of deferments (spring or autumn) at moderate and severe livestock grazing intensities (maintained by adjusting contrasting forage allowances during 25 years) on the cover of dominant species, and aboveground and belowground biomass. The experiment was arranged in a completely randomized design with three replications of grazing exclusions, applied simultaneously at moderate and severe grazing intensities. Measurements of above‐ and belowground biomass and the coverage of the five dominant species were performed before and after grazing exclusion periods.ResultsUnder severe grazing intensity, erect‐growing grasses were replaced by prostrate species, which were able at least to maintain the belowground biomass found at moderate grazing intensity. In response to deferments, severe grazing intensity changed toward a significant increase in aboveground biomass and in the coverage of plants with erect growing habit. However, total belowground biomass remained unaffected by exclusions in both grazing intensities. The relation of root:shoot biomass was lower under moderate grazing intensity, and showed a negative response to deferment treatments at severe grazing intensity.ConclusionLong‐term contrasting grazing intensities applied in South American Campos grasslands determine several changes in above‐ and belowground relationships. Prevalence of prostrate plants under severe grazing is associated with a high partitioning capacity of assimilates toward the subterranean biomass, higher than in the tall species predominant under moderate grazing. The fast recovery of aboveground biomass, the maintenance of the underground biomass and the increase of tall grasses in response to deferments reveals the high resilience capacity of this ecosystem after a long‐term period of overgrazing.

Seasonal dynamics of the photosynthetic apparatus parameters of upright and prostrate pine species using the example of Pinus sibirica and P. pumila

The seed progeny photosynthesis intensity and the photosynthetic apparatus state of genus Pinus species of different life forms were studied in seasonal dynamics: P. sibirica is an upright tree, P. pumila is a prostrate species. The seed progeny age was twelve years old. The photosynthesis intensity of both species increased from May to July, was maximum in July and amounted to 9.2 mg CO2 mg-1 fr. m. h-1 in Siberian stone pine and 7.8 mg CO2 mg-1 fr. m. h-1 in Siberian dwarf pine, in August the assimilation activity began to decrease in both species. Studies have shown that in summer P sibirica had photosynthesis values 15-20 % higher than those of P pumila. In the winter months, the chlorophyll content did not differ significantly between the species; at the same time, during the growing season, Siberian stone pine contained more photosynthetic pigments than Siberian dwarf pine. An assessment of the photosynthetic apparatus functional activity showed that the seasonal dynamics of the maximum quantum yield photochemistry (Fv/Fm) of photosystem II (PSII), the real quantum yield of PS II ^psII) in both species had a similar character: Fv/ Fm sharply decreased from November to February, increased from March to June, reached its maximum values and practically did not change in June-Septem-ber and decreased in October. The electron transport rate (ETR) was minimal from November to April, increased sharply in May, and had maximum values in May, June, and July. In August, a significant decrease in ETR was observed. The rate of electron transport significantly differed between species in May-September and was significantly higher in Siberian stone pine. The shown differences between the P sibirica - upright species, compared to P. pumila - prostrate species, indicate species specific physiological parameters.

Lepidagathis mahakassapae sp. nov. (Acanthaceae: Barlerieae) from the high elevated Lateritic Plateau of northern Western Ghats of Maharashtra, India

Lepidagathis mahakassapae sp. nov., a monocarpic and endemic species of Acanthaceae, is described from Western Maharashtra, India. The new species is allied to L. sabui from Konkan, Maharashtra, but differs by having oblanceolate acuminate leaves, pubescent terminal elongated spikes, large floral but small sterile bracts and lanceolate broader segment of the bracteole. The stems of L. mahakassapae grows up to 250 cm in length while a few other prostrate species grows up to this length. Illustrations and colour photographs are provided for ease of identification.

Long-term ecological research in southern Brazil grasslands: Effects of grazing exclusion and deferred grazing on plant and arthropod communities.

Grazing exclusion may lead to biodiversity loss and homogenization of naturally heterogeneous and species-rich grassland ecosystems, and these effects may cascade to higher trophic levels and ecosystem properties. Although grazing exclusion has been studied elsewhere, the consequences of alleviating the disturbance regime in grassland ecosystems remain unclear. In this paper, we present results of the first five years of an experiment in native grasslands of southern Brazil. Using a randomized block experimental design, we examined the effects of three grazing treatments on plant and arthropod communities: (i) deferred grazing (i.e., intermittent grazing), (ii) grazing exclusion and (iii) a control under traditional continuous grazing, which were applied to 70 x 70 m experimental plots, in six regionally distributed blocks. We evaluated plant community responses regarding taxonomic and functional diversity (life-forms) in separate spatial components: alpha (1 x 1 m subplots), beta, and gamma (70 x 70 m plots), as well as the cascading effects on arthropod high-taxa. By estimating effect sizes (treatments vs. control) by bootstrap resampling, both deferred grazing and grazing exclusion mostly increased vegetation height, plant biomass and standing dead biomass. The effect of grazing exclusion on plant taxonomic diversity was negative. Conversely, deferred grazing increased plant taxonomic diversity, but both treatments reduced plant functional diversity. Reduced grazing pressure in both treatments promoted the break of dominance by prostrate species, followed by fast homogenization of vegetation structure towards dominance of ligneous and erect species. These changes in the plant community led to increases in high-taxa richness and abundance of vegetation-dwelling arthropod groups under both treatments, but had no detectable effects on epigeic arthropods. Our results indicate that decision-making regarding the conservation of southern Brazil grasslands should include both intensive and alleviated levels of grazing management, but not complete grazing exclusion, to maximize conservation results when considering plant and arthropod communities.

Potential grazing indicator forbs for two mesic grasslands in South Africa

Abstract Mesic grasslands in South Africa harbour a diverse community of herbaceous perennial forb species that outnumber grass species by up to 5–6:1, provide various ecosystem services as well as forage for livestock, and are sensitive to overgrazing. However, despite their prevalence and ecological importance, the potential of forb species as grazing indicators has not been evaluated nor are they routinely included in grassland condition assessments. We aimed, therefore, to identify a subset of potential grazing indicator forb species that had a consistent response to a range of grazing intensities historically applied at sites in two mesic grasslands, Midlands Mistbelt grassland (n = 123) and KwaZulu-Natal Sandstone Sourveld grassland (n = 55). Canonical correspondence analysis was used to assess forb composition changes in response to an ordinal index of grazing intensity to identify the most responsive abundant forbs in each grassland. Most (88–92%) forbs had a neutral or inconsistent response to grazing but 24 and 32 species in Mistbelt and Sandstone grassland, respectively, were sufficiently abundant and responsive to be considered potential key grazing indicators. Alternative, somewhat less reliable indicator species were also identified. Grazing-sensitive indicator forbs that declined under grazing (Decreaser species) mostly were erect with elevated growing points whereas grazing-resistant species (Increasers) were predominantly prostrate species. A weighted sum of the abundance of indicators and their grazing sensitivity weights based on the relative position of their centroids along the grazing gradient provides an index (1–100), the forb condition score (FCS), of the overall impact of grazing on the forbs at a site, with high FCS indicating minimal impact. The FCS adequately predicts overall indigenous forb species richness (square-root transformed) in both Mistbelt (r2 = 0.657) and Sandstone grassland (r2 = 0.795). The key grazing indicator forbs identified in our study could be used together with other assessment methods of grass condition and cover for rapid and cost-effective assessment and monitoring of the impact of grazing on the integrity of mesic grassland. Further testing and refinement of the proposed grazing indicator forbs and the FCS index is, however, required.

Deverra rapaletsa (Apiaceae), a new limestone endemic species from the Ghaap Plateau, Northern Cape, South Africa

We describe a new prostrate species of Deverra (Apiaceae), D. rapaletsa Magee & Zietsman, from the Ghaap Plateau in the Griqualand West Centre of endemism, South Africa. This is the third species of Deverra in southern Africa and brings the total number of species in the genus to 10. The three southern African species are separated from the rest of the species in northern African and Arabia by an arid disjunction. The new species is distinguished by the prostrate habit, densely warty ovaries and slender branches with short internodes. Deverra rapaletsa is known from two populations and favours limestone outcrops.

Differential responses of three grasses to defoliation, water and light availability

Grazing not only modifies the structure and functioning of grasslands, it also changes micro-environmental conditions that alter the availability of resources. The aim of this study was to analyze the response of grasses with different photosynthetic pathways (C3/C4), growth forms (prostrate/erect), and grazing responses (increaser/decreaser) to defoliation and resource availability. In a greenhouse, we performed a factorial experiment with three factors: defoliation, light, and water and three species: Axonopus affinis (C4 prostrate, increaser), Coelorachis selloana (C4 erect, decreaser), and Bromus auleticus (C3 erect, decreaser). We measured the relative growth rate (RGR), biomass assignment, and specific leaf area. The RGR of both C4 species was affected by light availability, while the decreaser C3 did not respond to any factor. Biomass allocation to leaves and stolons changed with the interaction between light and water in the C4 prostrate species (increaser). In the C4 erect grass (decreaser), biomass allocation was more affected by defoliation under low levels of light and water. Low light availability and defoliation reduced the assignment to leaves, while the allocation to rhizomes increased. Species-specific responses to resources availability that are modified by grazing were related to photosynthetic pathway, growth form, and grazing responses. Biomass allocation was related to strategies to avoid and/or tolerate grazing. The investment to leaves was limited by light and water availability in prostrate species, while in erect grasses it was controlled by defoliation and water availability. Our results highlight the importance of species responses to changes in resource availability associated to grazing regimes.

Restoring lost ecological function: ecological surrogates facilitate maintenance of coastal turf communities

ABSTRACTLost or extinct ecosystem function presents challenges for managers of natural ecosystems for conservation. One solution is to use ecological surrogates to replace these processes but the settings under which this often controversial approach succeeds are unclear. We tested whether mammalian grazing could be used as a surrogate for grazing by an extinct avian herbivore guild in two threatened coastal turf communities that are structured by an exposure and salt gradient, and vulnerable to non-native encroachment and invasion. Prostrate species had higher cover and species density relative to erect taxa when grazed, with the effect greater for native than non-native taxa. Prostrate species, dominated by native taxa, were most abundant closest to the ocean, with a secondary peak in abundance 25–35 m inland. A positive nutrient feedback mechanism consistent with a grazing lawn was not observed suggesting a primary role for the salinity gradient, augmented by opportunistic grazing of taller species, in structuring these communities. Synthesis and application: mammalian grazers can replace the likely functional role of extinct avian herbivores in turf communities under certain environmental settings.

Impact of stocking rate on species diversity and composition of a subtropical grassland in Argentina

AbstractQuestionsWhat is the effect of a range of controlled stocking rates on plant species richness and diversity?LocationSubtropical grasslands of Corrientes, Argentina, South America.MethodsWe studied the effect of three controlled stocking rates (0.6, 0.8 and 1.0 cow equivalents·ha−1) on species diversity and composition during 8 yr. We calculated species diversity using the antilog of the Shannon‐Wiener index, and considered its two components, richness and evenness. We also assessed the proportion of prostrate and erect species. Species abundance was based on biomass estimations.ResultsSpecies diversity under high stocking rates gradually decreased throughout the experiment and became nearly 50% lower than under low stocking rate. This decline was largely accounted for by changes of evenness because species richness was not affected by stocking rates. Species composition clearly diverged among the three treatments over time. Low stocking rate maintained a fairly constant relative cover of erect and prostrate grasses throughout the experiment, whereas intermediate and high stocking rate treatments were gradually and consistently enriched in prostrate grasses and forbs. These effects occurred simultaneously with drastic inter‐annual changes likely driven by annual precipitation.ConclusionsThe range of stocking rates had no effect on species richness, but reduced diversity through the effect on evenness. High stocking rate progressively increased the proportion of prostrate species in the biomass.

Higher photosynthetic capacity and different functional trait scaling relationships in erect bryophytes compared with prostrate species

Ecophysiological studies of bryophytes have generally been conducted at the shoot or canopy scale. However, their growth forms are diverse, and knowledge of whether bryophytes with different shoot structures have different functional trait levels and scaling relationships is limited. We collected 27 bryophyte species and categorised them into two groups based on their growth forms: erect and prostrate species. Twenty-one morphological, nutrient and photosynthetic traits were quantified. Trait levels and bivariate trait scaling relationships across species were compared between the two groups. The two groups had similar mean values for shoot mass per area (SMA), light saturation point and mass-based nitrogen (N(mass)) and phosphorus concentrations. Erect bryophytes possessed higher values for mass-based chlorophyll concentration (Chl(mass)), light-saturated assimilation rate (A(mass)) and photosynthetic nitrogen/phosphorus use efficiency. N(mass), Chl(mass) and A(mass) were positively related, and these traits were negatively associated with SMA. Furthermore, the slope of the regression of N(mass) versus Chl(mass) was steeper for erect bryophytes than that for prostrate bryophytes, whereas this pattern was reversed for the relationship between Chl(mass) and A(mass). In conclusion, erect bryophytes possess higher photosynthetic capacities than prostrate species. Furthermore, erect bryophytes invest more nitrogen in chloroplast pigments to improve their light-harvesting ability, while the structure of prostrate species permits more efficient light capture. This study confirms the effect of growth form on the functional trait levels and scaling relationships of bryophytes. It also suggests that bryophytes could be good models for investigating the carbon economy and nutrient allocation of plants at the shoot rather than the leaf scale.

Is sexual reproduction of high-mountain plants endangered by heat?

Strong solar irradiation in combination with still air and dry soil can cause prostrate high-mountain plants to heat up considerably and ultimately suffer heat damage. Such heat damage has been repeatedly shown for vegetative structures, but not for reproductive structures, which we expected to be particularly vulnerable to heat. Heat effects on cold-adapted plants may increase with rising global temperatures and the predicted increase in heat waves. We have tested the heat tolerance of reproductive versus vegetative shoots at different reproductive stages, comparing ten common plant species from different elevation belts in the European Alps. Plant samples were exposed to temperatures in 2-K steps of 30 min each between 42 and 56 °C. Heat damage was assessed by visual rating and vital staining. Reproductive shoots were on average 2.5 K less heat tolerant (LT50, i.e. the mean temperature causing 50 % heat damage, 47.2 °C) than vegetative shoots (mean LT50 49.7 °C). Initial heat injuries (mean LT10) were observed at 43–45 °C in heat-susceptible species and at 45–47 °C in more heat-tolerant species, in at least one reproductive stage. Generally, heat tolerance was significantly higher during fruiting than during the bud stages and anthesis. Prostrate species with acaulescent buds and flowers tolerated heat better than those with caulescent buds and flowers. Petals were the most heat-susceptible plant structure and mature pollen the most heat tolerant. Based on these data, heat tolerance of reproductive structures appears to be adapted to the prevailing maximum temperatures which the plants experience during different reproductive stages in their environment. During hot spells, however, heat tolerance thresholds may be exceeded. More frequent heat waves would decrease the reproductive output and, consequently, the competitiveness of heat-susceptible species.Electronic supplementary materialThe online version of this article (doi:10.1007/s00442-015-3247-0) contains supplementary material, which is available to authorized users.

Flood disturbance effects on benthic diatom assemblage structure in a semiarid river network

Disturbances such as floods and droughts play a central role in determining the structure of riverine benthic biological assemblages. Extreme disturbances from flash floods are often restricted to part of the river network and the magnitude of the flood disturbance may lessen as floods propagate downstream. The present study aimed to characterize the impact of summer monsoonal floods on the resistance and resilience of the benthic diatom assemblage structure in nine river reaches of increasing drainage size within the Gila River in the southwestern United States. Monsoonal floods had a profound effect on the diatom assemblage in the Gila River, but the effects were not related to drainage size except for the response of algal biomass. During monsoons, algal biomass was effectively reduced in smaller and larger systems, but minor changes were observed in medium systems. Resistance and resilience of the diatom assemblage to floods were related to specific species traits, mainly to growth forms. Tightly adhered, adnate and prostrate species (Achnanthidium spp., Cocconeis spp.) exhibited high resistance to repeated scour disturbance. Loosely attached diatoms, such as Nitzschia spp. and Navicula spp., were most susceptible to drift and scour. However, recovery of the diatom assemblage was very quick indicating a high resilience, especially in terms of biomass and diversity. Regional hydroclimatic models predict greater precipitation variability, which will select for diatoms resilient to bed-mobilizing disturbances. The results of this study may help anticipate future benthic diatom assemblage patterns in the southwestern United States resulting from a more variable climate.

Differential bud activation by a net positive root signal explains branching phenotype in prostrate clonal herbs: a model

Regulation of branching within perennial prostrate clonal herbs differs from the annual orthotropic species, Arabidopsis and pea, as the dominant signal transported from roots is a branching promoter, not an inhibitor. Trifolium repens, an exemplar of such prostrate species, was used to investigate the interaction between roots and branch development. This study tests whether or not current knowledge when synthesized into a predictive model is sufficient to simulate the branching pattern developing on the shoot distal to a basal root. The major concepts underpinning the model are: (i) bud outgrowth (activation) is stimulated in a dose-dependent manner by branching promoter signals from roots, (ii) the distribution of this net root stimulus (NRS) is uniform throughout the shoot system distal to the basal root but declines geometrically in intensity upon continued enlargement of this shoot system, and (iii) each bud has an outgrowth potential, equal to the activation level of the apical bud in which it forms, that moderates its response to NRS. The validity of these concepts was further tested by running simulations of the branching of a phylogenetically-distanced prostrate perennial monocotyledonous species, Tradescantia fluminensis. For both species the model reasonably accounted for the observed pattern of branching. The outgrowth potential of buds plays an important role in limiting the number of hierarchies of branching that can develop on a plant. In conclusion, for both species, the model accounted for the major factors involved in the correlative regulation of branching and is possibly also pertinent for all prostrate clonal species.

Divergent responses to long-term grazing exclusion among three plant communities in a flood pulsing wetland in eastern Australia.

We examined the effects of grazing exclusion over a period of 14 years on the species richness and community composition of three plant communities with different dominant species and water regimes in the Gwydir Wetlands in eastern Australia. Responses to grazing exclusion varied among the three plant communities, and were most likely to be evident during dry periods rather than during periods of inundation. In frequently flooded plant communities, there was an increase in phytomass following exclusion of domestic livestock, but changes in plant community composition and species richness due to livestock exclusion varied depending on the morphological attributes of the dominant plant species. In a plant community where tall sedge species were dominant, livestock exclusion further increased their dominance and overall species richness declined. In contrast, where a prostrate grass species such as Paspalum distichum was dominant, species richness increased following livestock exclusion, due to an increase in the abundance of taller dicotyledon species. However, livestock exclusion in a community where flooding was less frequent and native grass species have been largely replaced with the introduced species Phyla canescens, resulted in no significant changes to phytomass, species richness or community composition among the grazing exclusion treatments over time. Our results indicate responses to exclusion of domestic livestock are dependent upon the dominant species within the plant community and will likely vary over time with the extent of wetland inundation. Grazing exclusion alone, without increased flooding, is unlikely to restore floristically degraded floodplain plant communities.

Effects of microhabitat and growth form on bryophyte mortality associated with leaf litter burial in a boreal spruce forest

AbstractQuestionsDo mortality rates of boreal bryophytes associated with leaf litter burial vary with degree of shelter on forest floor microsites in spruce‐dominated forests? Do erect and prostrate species respond similarly? What is the relative importance of deciduous leaves (from aspen and birch) vs conifer needles as bryophyte mortality agents?LocationBoreal spruce forests of central Sweden.MethodsA transplant study examining mortality was set up with four different bryophyte species: two creeping, prostrate liverworts (Calypogeia integristipula and Lepidozia reptans) and two more erect mosses (Rhytidiadelphus triquetrus and Hylocomiastrum umbratum). We tested for differences in mortality rates associated with leaf litter burial in three microhabitats differing in degree of shelter on the forest floor, i.e. sheltered (large boulders, tree bases of spruce) and unsheltered (open forest floor).ResultsAfter two growing seasons, 12.7% of the bryophyte transplants (40 out of 316, of which 37 transplants were prostrate liverworts) were dead, presumably due to litter burial. These two prostrate liverworts displayed significantly higher mortality rates close to boulders and at tree bases compared to unsheltered forest floors. Furthermore, although only comprising a small portion of the canopy (<10%), deciduous litter accounted for 53% of all transplants that were buried by litter, compared to 47% for conifer needle litter.ConclusionWe find fine‐scale spatial patchiness in the responses of bryophytes to litter fall. Mortality of prostrate liverworts associated with litter burial varies among microhabitats on the forest floor, with significantly higher mortality at sheltered microsites (here exemplified by boulders and tree bases) compared to erect moss species. Bryophytes close to microtopographic structures (e.g. boulders and trees) are more strongly exposed to litter burial, but such structures can also function as refuges under disturbance events such as clear‐cuts and windthrows. In addition, they may contain convex surfaces that accumulate less litter than flat or convex forest floor surfaces. The observed large effect of litter burial associated with bryophyte mortality, and the variation among microhabitats and species growth forms, suggest that incorporation of litter fall is of vital importance for our understanding of the dynamics of forest bryophyte communities.

Floristic and vegetation structure of a grassland plant community on shallow basalt in southern Brazil

Few studies have adequately described the floristic and structural features of natural grasslands associated with shallow basalt soils in southern Brazil. This study was carried out on natural grazing land used for livestock production in the municipality of Santana do Livramento, in the Campanha region of the state of Rio Grande do Sul, Brazil. The aim of the study was to describe the floristic and structural diversity of the area. The floristic list obtained comprises 229 plant taxa from 40 botanical families, with a predominance of the families Poaceae (62), Asteraceae (28), Fabaceae (16) and Cyperaceae (12). The estimated diversity and evenness in the community were 3.00 and 0.874, respectively. Bare soil and rock outcrops accounted for 19.3% of the area, resulting in limited forage availability. Multivariate analysis revealed two well-defined groups among the sampling units. One group showed a high degree of internal aggregation, associated with deep soils, and was characterized by the presence of tussocks, whereas the other was less aggregate and was characterized by prostrate species growing on shallow soil. Ordination analysis indicated a gradient of moisture and of soil depth in the study area, resulting in different vegetation patterns. These patterns were analogous to the vegetation physiognomies described for Uruguayan grasslands. Overall, the grassland community studied is similar to others found throughout southern Brazil, although it harbors more winter forage species. In addition, the rare grass Paspalum indecorum Mez is locally dominant in some patches, behaving similarly to P. notatum Fl., a widespread grass that dominates extensive grassland areas in southern Brazil.

Morphogenesis of native grasses of Pampa Biome under nitrogen fertilization

Morphogenetic and structural characteristics of the native grasses of the Pampa Biome Andropogon lateralis, Aristida laevis, Axonopus affinis, Erianthus angustifolius, Paspalum notatum, Paspalum plicatulum, Piptochaetium montevidense and Sorghastrum pellitum were evaluated as to the effect of nitrogen (N) fertilization (zero and 100 kg N/ha). The experimental design was of randomized blocks with three replicates in a 8 × 2 (native grasses × N) factorial arrangement. Accumulated thermal sums of 350 and 700 degree days determined the interval between cuts for prostrate and caespitose growth habit species, respectively. Species considered of resource conservation (A. laevis, E. angustifolius, P. plicatulum and S. pellitum) had the highest leaf elongation rate when they received N. For leaf appearance rate, phyllochron, leaf senescence rate, leaf lifespan, number of green leaves and final length of leaf blades, there was difference between the evaluated species.

Disturbance and recovery in semi‐arid Mediterranean grasslands

AbstractAims(1) To investigate the temporal response of semi‐arid Mediterranean grasslands to multiple disturbances as well as P fertilization and irrigation; and (2) to determine the reaction of single species or groups of species as well as the extent of recovery of the grassland community following cessation of the above interventions.LocationNorth Greece.MethodsIn a fenced area, six treatments (burning, irrigation, digging, cutting, P fertilization and control) were applied, for three growing seasons, in a completely randomized block design with four blocks. Biomass was sampled in five (0.5 × 0.5 m) quadrats per plot at the end of the growing season and sorted into the following functional groups: annual grasses, perennial grasses, annual legumes and forbs (that included all the other species). Measurements were repeated 1 and 7 yr after cessation of the treatments.ResultsAnnual grasses and legumes were positively favoured by cutting, burning and digging, which produced changes in vegetation composition over time. P fertilization had a positive influence on total legume biomass. Effects on individual species were not uniform. Plant composition after cessation of the disturbance treatments was quite different. Total legume biomass remained high 1 yr after the cessation of P fertilization but declined thereafter. Annual grasses and legumes constituted the largest portion of the total biomass in the first year of the experiment. Disturbance (burning, cutting and digging) gradually reduced their biomass in favour of forbs. Seven years after cessation of the treatments, the tall annual, as well as perennial grasses constituted more than 80% of the total biomass. Under conditions of disturbance, short annual species had an advantage over perennials, while cessation of disturbance enables perennial grasses to dominate.ConclusionsDisturbance promotes the dominance of annuals, especially species with a persistent seed bank. Repeated disturbance encourages an increase of small or prostrate species. Cessation of disturbance leads to the rapid recovery of biomass production. Tall annuals are promoted. P fertilization clearly favours legumes in the short term.