Abundance Of Plant Species Research Articles

Effects of interactions between anthropogenic stressors and recurring perturbations on ecosystem resilience and collapse.

Insights into declines in ecosystem resilience and their causes and effects can inform preemptive action to avoid ecosystem collapse and loss of biodiversity, ecosystem services, and human well-being. Empirical studies of ecosystem collapse are rare and hampered by ecosystem complexity, nonlinear and lagged responses, and interactions across scales. We investigated how an anthropogenic stressor could diminish ecosystem resilience to a recurring perturbation by altering a critical ecosystem driver. We studied groundwater-dependent, peat-accumulating, fire-prone wetlands known as upland swamps in southeastern Australia. We hypothesized that underground mining (stressor) reduces resilience of these wetlands to landscape fires (perturbation) by diminishing groundwater, a key ecosystem driver. We monitored soil moisture as an indicator of ecosystem resilience during and after underground mining. After landscape fire, we compared responses of multiple state variables representing ecosystem structure, composition, and function in swamps within the mining footprint with unmined reference swamps. Soil moisture declined without recovery in swamps with mine subsidence (i.e., undermined), but was maintained in reference swamps over 8years (effect size 1.8). Relative to burned reference swamps, burned undermined swamps showed greater loss of peat via substrate combustion; reduced cover, height, and biomass of regenerating vegetation; reduced postfire plant species richness and abundance; altered plant species composition; increased mortality rates of woody plants; reduced postfire seedling recruitment; and extirpation of a hydrophilic animal. Undermined swamps therefore showed strong symptoms of postfire ecosystem collapse, whereas reference swamps regenerated vigorously. We found that an anthropogenic stressor diminished the resilience of an ecosystem to recurring perturbations, predisposing it to collapse. Avoidance of ecosystem collapse hinges on early diagnosis of mechanisms and preventative risk reduction. It may be possible to delay or ameliorate symptoms of collapse or to restore resilience, but the latter appears unlikely in our study system due to fundamental alteration of a critical ecosystem driver. Efectos de las interacciones entre los estresantes antropogénicos y las perturbaciones recurrentes sobre la resiliencia y el colapso de los ecosistemas.

Essential Oils from Vietnamese Asteraceae for Environmentally Friendly Control of Aedes Mosquitoes.

Mosquitoes, in addition to being a biting nuisance, are vectors of several pathogenic viruses and parasites. As a continuation of our work identifying abundant and/or invasive plant species in Vietnam for use as ecologically friendly pesticidal agents, we obtained the essential oils of Blumea lacera, Blumea sinuata, Emilia sonchifolia, Parthenium hysterophorus, and Sphaeranthus africanus; analyzed the essential oils using gas chromatographic techniques; and screened the essential oils for mosquito larvicidal activity against Aedes aegypti and Aedes albopictus. The most active larvicidal essential oils were B. sinuata, which was rich in thymohydroquinone dimethyl ether (29.4%), (E)-β-caryophyllene (19.7%), α-pinene (8.8%), germacrene D (7.8%), and α-humulene (4.3%), (24-h LC50 23.4 and 29.1 μg/mL) on Ae. aegypti and Ae. albopictus, respectively, and Emilia sonchifolia, dominated by 1-undecene (41.9%) and germacrene D (11.0%), (24-h LC50 30.1 and 29.6 μg/mL) on the two mosquito species. The essential oils of P. hysterophorus and S. africanus were also active against mosquito larvae. Notably, B. sinuata, P. hysterophorus, and S. africanus essential oils were not toxic to the non-target water bug, Diplonychus rusticus. However, E. sonchifolia essential oil showed insecticidal activity (24-h LC50 48.1 μg/mL) on D. rusticus. Based on these results, B. sinuata, P. hysterophorus, and S. africanus essential oils appear promising for further investigations.

Impacts of Livestock Grazing on Vegetation and Soil in Lowland Grassland Ecosystem of Nepal

Livestock grazing is one of the largest sectors for land use globally, and contrasting impacts (negative, neutral, and positive) of livestock grazing on vegetation and soil have been observed. In Koshi Tappu Wildlife Reserve (KTWR), livestock grazing is one of the major problems but has been feebly addressed in previous research. This study, therefore, aims to determine the impacts of livestock grazing on vegetation and soil quality in grasslands of core and buffer zones of KTWR. Less grazing intensity was observed at the core zone compared to the buffer zone. Livestock grazing was observed with negative impacts on the richness and diversity of the plant species causing changes in the community assemblages. Invasive plant species richness, however, was found higher in the low grazed areas. Differences in soil pH, phosphorus, and potassium content between high and low grazed areas were not observed. In contrast, soil electrical conductivity, bulk density, and nitrogen content were significantly higher in the high grazed areas. Controlled grazing is recommended at buffer zone grasslands of KTWR to enhance plant diversity and nutrient availability. The core areas of the reserve should be managed for reducing the abundance and distribution of invasive alien plant species.

Drought‐driven shifts in relationships between plant biodiversity and productivity in temperate steppes

Abstract Drought events induced by global climate change strongly modify ecosystem structure and function in grasslands. Higher plant biodiversity can enhance ecosystem resistance to drought; however, the potential effects of drought on the relationships between above‐ground productivity (ANPP) and biodiversity along a natural aridity gradient remain poorly understood. Here, we studied the effects of experimental drought on plant community structure and ANPP during the two different dry years (2015 and 2017) spanning three temperate steppe sites with low‐, medium‐ and high‐aridity levels. We also examined the effects of drought and aridity on the associations of plant species (richness and abundance), functional (community‐weighted trait means and functional dispersion) and phylogenetic diversity (evolutionary lineages) with ANPP. A structural equation modelling (SEM) was used to elucidate how the drought affected ANPP by altering biodiversity attributes. We found that experimental drought shaped the biodiversity–ANPP relationships, and the biodiversity–ANPP relationships differed among three sites. At the low‐aridity site, ANPP was correlated with plant functional traits, whereas ANPP was correlated with functional dispersion, species and phylogenetic diversity at the medium‐aridity site. At the high‐aridity site, ANPP was correlated with species richness, functional traits and phylogenetic diversity. Compared with 2015, natural drought in 2017 strengthened the associations of species diversity, functional dispersion, leaf dry matter content and leaf nitrogen content with ANPP across three sites. SEM further showed that both experimental and natural drought directly decreased ANPP and indirectly decreased ANPP by reducing community‐weighted mean of plant height. Synthesis. These results suggest that the aridity increase or drought occurrence is likely to induce the shifts in the associations of ANPP with species and functional diversity, highlighting the important role of water availability or precipitation conditions in regulating the biodiversity–ANPP relationships in temperate steppes. Overall, functional traits related to plant size play a crucial role in modulating the response of productivity to drought across three steppe sites. Thus, to buffer the negative effects of drought on steppe ANPP should pay attention to protect the species with large plant size. Read the free Plain Language Summary for this article on the Journal blog.

Which regionalization scheme is the best to predict wetland plant distribution in Western Patagonia?

AbstractQuestionsGiven the current multiplicity of threats to pond biodiversity, there is a clear need to examine which environmental drivers determine the composition and distribution of species. Using wetland plants as pond biodiversity surrogates, two questions led to this work: How do wetland plant species assemblages and abundance vary across local‐ and regional‐scale classification schemes in wetlands? How does wetland plant beta‐diversity vary within these wetland classification schemes?LocationWestern Patagonia, Argentina, from 36°S to 56°S and from 73°W to 65°W.MethodsWetland plant distribution constrained by water and climatic factors was analyzed using canonical correspondence analysis. Variance partitioning analysis was performed to assess which classification scheme (phytogeographical units, wetland regions, wetland genesis and hydrogeomorphological types) better explained variation in plant composition. An IndVal analysis was also carried out to detect taxa with the highest association values (indicator taxa) for the different categories of wetland classification. Beta‐diversity was calculated to evaluate variation patterns within classification schemes.ResultsPlant distribution was mainly related to site location across the latitudinal gradient, following a decreasing pattern of air temperature from northern to southern wetlands. Variance partitioning analysis confirmed the effectiveness of a regional‐scale classification (wetland regions) in predicting plant associations, and the IndVal analysis also highlighted this classification scheme above the remainder, sustaining the highest number of indicator taxa. Wetland plant beta‐diversity patterns were explained by relatively high species turnover, with species composition showing low nestedness values.ConclusionClimate factors rather than local characteristics were the main drivers of plant distribution at the wide regional scale analyzed. Wetland region (classification based on climatic criteria) was the most effective scheme in predicting plant associations and sustaining the highest number of indicator taxa. Also, ponds located in the Patagonian Andes and those with a glacigenic origin contribute most to the regional wetland plant diversity. Therefore, these aspects should be taken directly into account in the future delineation of protected areas to increase the resilience of Patagonian wetland habitats and their associated biota, and to maintain the ecosystem services that they provide.

Habitat selection and foraging preference of the endangered addax (Addax nasomaculatus) in a fenced wildlife reserve within its historic range: insights for supporting effective reintroduction

Reintroduction of species should be based on ecological knowledge, which is fundamental to enhancing the probability of success, but also in predicting the response to future changing landscapes. The addax (Addax nasomaculatus), an endangered antelope whose ecology is mostly unknown, was released in a fenced area of the Jbil National Park, Tunisia. Considering the extreme desert conditions of the area, seasonal changes should affect both habitat and diet selection. Addax occurrence, habitat selection and diet were assessed using an integrative approach, and analysed with multivariate statistics. During the wet season, preferred and avoided plant species abundance were highly correlated with addax occurrence; while in the dry season, preferred plant species abundance were positively correlated with addax presence. Micro-histological analysis of faecal samples indicated differences in diet between seasons. The integrative approach proposed represents a useful contribution for decision-making in the scope of reintroduction programmes and habitat restoration measures, by facilitating the assessment of habitat suitability for endangered antelopes in arid environments.

Deciphering the interactions between plant species and their main fungal root pathogens in mixed grassland communities

Abstract Plant diversity can reduce the risk of plant disease, but positive, and neutral effects have also been reported. These contrasting relationships suggest that plant community composition, rather than diversity per se, affects disease risk. Here, we investigated how the diversity and composition of plant communities drive root‐associated pathogen accumulation belowground. In a temperate grassland biodiversity experiment, containing 16 plant species (forbs and grasses), we determined the abundance of root‐associated fungal pathogens in individual plant species growing in monocultures and in four‐species mixtures through Illumina MiSeq amplicon sequencing. In the plant monocultures, we identified three major fungal pathogens that differed in host range: Paraphoma chrysanthemicola, associated with roots of forb species of the Asteraceae family, Slopeiomyces cylindrosporus, associated with grass species, and Rhizoctonia solani, associated with multiple forb and grass species. In mixtures, there was no significant reduction in relative abundance of these pathogens in their host species as compared to monocultures. However, in mixtures, there was a significant increase in relative abundance of each pathogen in several non‐host and host plant species. Across mixtures, plant community composition affected pathogen relative abundance in individual plant species. This effect was driven by the presence of a particular neighbouring plant species (depending on the pathogen), rather than functional group composition (i.e. grass/forb ratio) or averaged pathogen pressure (based on monocultures) of all neighbours. Specifically, the presence of neighbour host species Achillea millefolium significantly increased P. chrysanthemicola, but decreased R. solani relative abundance in several host and non‐host plant species in mixtures. Synthesis. Our results indicate that interactions between different plant species—both host and non‐hosts—and fungal pathogens underlie the effects of plant diversity on root pathogen abundance. Non‐host species may act as pathogen reservoirs in diverse plant communities, as they harboured certain pathogens in mixtures, but not in monocultures. Additionally, particular host species can strongly affect pathogen abundance in other (host and non‐host) plant species in plant mixtures, suggesting clear effects of species identity in the diversity–disease relationship. Below‐ground disease risk thus depends on plant community composition rather than diversity per se, via specific interactions between plant species and their root‐associated pathogens.

Waterbodies in the Floodplain of the Drava River Host Species-Rich Macrophyte Communities despite Elodea Invasions

The contribution discusses macrophyte communities in natural and man-made waterbodies located on the active floodplain along the Drava river (Slovenia). We presumed that these different types of wetlands host a great number of macrophyte species, but this diversity may be affected by the presence of alien invasive species Elodea canadensis and E. nuttallii. Presence, relative abundance, and growth forms of plant species along with selected environmental parameters were monitored. Correlation analyses and direct gradient analyses were performed to reveal the possible relations between the structure of macrophyte community and environmental parameters. Number of macrophytes in surveyed water bodies varied from 1 to 23. Besides numerous native species we also recorded Elodea canadensis and E. nuttallii, which were present in 19 out of 32 sample sites, with E. nuttallii prevailing. The less invasive E. canadensis was absent from ponds and oxbow lakes but relatively abundant in side-channels, while E. nuttallii was present in all types but dominant in ponds. The most abundant native species were Myriophyllum spicatum and M. verticillatum, Ceratophyllum demersum and Potamogeton natans. Correlation analyses showed no negative effect of the invasive alien Elodea species to the species richness and diversity of native flora. Positive correlation between the abundance of E. nuttallii and temperature of the water was obtained.

Fire shifts the soil fertility and the vegetation composition in a natural high-altitude grassland in Brazil

The Serra da Calçada Mountain (Minas Gerais State, Brazil) hosts a natural grassland with high biodiversity and endemism, locally known as campo rupestre, which grows over hematite and quartzite outcrops, protecting several headwaters. However, this mountain has been severely threatened by anthropogenic fires and its restoration has been challenged by the lack of knowledge on the effect of fire on plant species and soil fertility. Thus, this study aimed to assess a burned campo rupestre site after 1 year concerning plant biodiversity and soil properties as compared to a preserved site. Aside from the high plant biodiversity, the preserved site (with no fire history) showed a high natural soil fertility, particularly regarding soil organic matter (SOM): ∼3.48%, Cationic Exchange Capacity (CEC): ∼8.4 meq/100g, soil ammonium (NH4+-N): ∼11 ppm and soil phosphorus (P): ∼6.9 mg/Kg. However, the fire reduced not only the plant species composition, abundance, richness and biodiversity, but also disrupted the natural soil fertility. There was a change in N chemical species from ammonium to nitrate as well as an increase in sodium (Na) content, in addition to a depletion of SOM and CEC. The variations of nitrogen chemical species, sodium, SOM, CEC and soil moisture explained 79% of the changes in plant composition as revealed by the Mantel matrix permutation test. Increased soil nitrate and sodium were considered the main factors determining changes in vegetation composition after fire. Therefore, fires should be strictly avoided for the management of the campo rupestre grassland, and for the rehabilitation purposes, the improvement of SOM and ammonium in detriment of nitrate is recommended.

Traditional human practices protect diversity of open forests threatened by ticking nutrient time bomb

Open forests are among the world's most species-rich ecosystems but these are now suffering from strong environmental pressure. With the increasing frequency of drought events accompanying climate change, open forests are now at high risk of canopy openness, an associated increase in nutrient load, and a consequent reordering of the plant community. Based on an 11-year field manipulative experiment, we examined whether the reintroduction of traditional forest uses, in particular the regular removal of litter which has been practiced for many centuries in Europe, may mitigate eutrophication and protect the ancient plant diversity of open forests. We examined vascular plant composition in 64, 3 × 3 m plots in 32 randomized blocks, each consisted of one litter-removal and one control plot in a subcontinental thermophilous oak forest dominated by Quercus petraea (Czech Republic, Central Europe). We analyzed how regular litter removal influenced the changes in topsoil nutrients and diversity and abundances of perennial, short-lived monocarpic and open oak forest plant species after eleven years of the annual application of this management. The regular litter removal significantly mitigated eutrophication by a reducing total nitrogen, and significantly decreased the amounts of base cations Ca2+ and Mg2+ in the topsoil. The studied plant species groups responded differently. Perennial and open oak forest species significantly increased their richness and abundances in the litter-removal plots and at the same time their diversity did not change significantly depending on inter-annual weather conditions. In contrast, litter removal negatively affected abundances of short-lived monocarpic species, whose richness was also considerably influenced by weather conditions (decreased the most in years with spring droughts). Moreover, we have found a protective effect of regular litter removal on drought-sensitive open oak forest species that survived in the litter-removal plots, whereas some completely disappeared from control sites during the period of repeated drought events. Our study thus demonstrates that litter removal is a tool with high potential in maintaining biodiversity in open forests affected by climate change.

Phytoremediation potential of Schumannianthus dichotomus in vertical subsurface flow constructed wetland

Schumannianthus dichotomus (Murta) is a naturally abundant wetland plant species in Bangladesh that has significant economic and aesthetic values. This species is perennial, and fast-growing in the nutrient-abundant swamp and marshes, moreover, it can thrive in a shaded and semi-shaded environment. Although it has all the potential to be a prominent Constructed Wetlands (CW) plant, no considerable study has yet been reported on the phytoremediation potential of the plant. The study was conducted to scrutinize the contaminants removal efficiency of the Murta plant in a lab-scale vertical subsurface flow constructed wetland (VSSFCW). Two CW columns were installed for the experiment: one kept planted (experimental) with the Murta plants and the another remained unplanted (control). Afterward a two months stabilization period, water samples were analyzed from the influent storage tank and both the experimental and control systems effluent at 24 h hydraulic retention time (HRT) for one month study period. The CWs were operated in the batch mode, for completing one cycle it run for one day, in keeping the flow 0.012m3/d and the hydraulic loading rate (HLR) 0.13 m3/d/m2. The results indicated higher reduction capability in the planted CW: 61.60 ± 2.85% Biochemical oxygen demand (BOD5), 53.98 ± 11.84% Chemical oxygen demand (COD), 70.25 ± 15.33% Nitrate (NO3-N), and 39.36 ± 30.85% Nitrite (NO2-N) reduction occurred in the column. Conversely, the unplanted CW reduced 43.31 ± 9.37% BOD5, 45.34 ± 8.88% COD, 9.92 ± 5.32 % NO3-N, and 15.87 ± 25.07% NO2-N. The study reports the reduction efficacy of the biochemical pollutants enhanced with the increase of the influent concentration. The average concentration of physical parameters of the influent, planted and unplanted CW was, respectively: 7.62±0.28, 6.8±0.16, 6.94±0.14 pH; 1107±140.50, 1199.03±57.48, 1050.75±96.18 μS/cm electrical conductivity (EC); 545.67±72.26, 533.51±84.12, 596.34±33.13 mg/L total dissolved solids (TDS); 0.55±0.07, 0.59±0.03, 0.52±0.02% salinity; 919.06±111.64, 835.27±39.53, 952.20±66.01 Ώ-cm resistivity; and 3.20±1.77, 5.15±1.00, 5.03±0.96 mg/L dissolved oxygen (DO). Therefore, 62% dissolved oxygen (DO) increased in the planted CW column than the influent sample water, whereas 59% DO enhance in the control. After all, the study suggests that S. dichotomus has significant organic reduction efficacy in the VSSFCW system, and could be regarded as an efficient CW plant.

Increased diversity of the species pool via seeding augments establishment of native species in experimental vacant‐lot restorations

AbstractQuestionThe harsh geophysical template characterized by the urban environment combined with people's choices has led ecologists to invoke environmental filtering as the main ecological phenomenon explaining urban biodiversity patterns. Yet, dispersal is often overlooked as a driving factor, especially on expanding vacant land. Does overcoming dispersal limitation by seeding native species in urban environments and increasing the functional or phylogenetic diversity of the seeding pool increase native plant species diversity and abundance in urban vacant land?LocationBaltimore, Maryland, USA.MethodsWe took an experimental approach to learn how different dimensions of plant biodiversity within a regional species pool augmented via seed additions, can explain variation in community structure over a three‐year period. Vacant lots were cleared and manipulated with seeding treatments of high or low phylogenetic and functional diversities from a pool of 28 native species. Establishment success, total native cover and native‐species richness were followed and compared to cleared, unseeded control lots as well as unmanipulated lots.ResultsSeeding increased native plant abundance and richness over uncleared plots, as well as cleared and unseeded control plots. Phylogenetically diverse seed mixtures had greater establishment success than mixtures composed of closely related species. Diversifying seed mixtures increased the likelihood of including species that are better able to establish on vacant land. However, there were no differences in varying levels of either functional or phylogenetic diversity.ConclusionsAugmenting the regional species pool via diverse seed mixtures can enhance native plant cover and richness under the harsh environmental conditions conferred by land abandonment.

Distribution patterns of macrophytes in shallow lakes of the lower Paraná River floodplain: Associations with environmental conditions

Abstract Macrophytes play key functional and structural roles in floodplain shallow lakes (SL), determining the maintenance of ecosystem functions and sustaining several productive activities. We assessed the relationship between macrophyte community structure (composition, species abundance, and plant diversity) and environmental features (SL dynamics, connectivity, morphometry, flood frequency, and water and sediment physical and chemical variables) in the Lower Paraná River floodplain. Our main hypothesis was that SL macrophyte distribution depends on direct and indirect environmental controls operating at multiple scales. The SL dynamics during the April–November 2017 Paraná River pulse were described according to their coverage changes (vegetation, and turbid or clear open water), which were assessed with supervised classifications on Landsat 8‐OLI scenes. Twenty‐five SL of the Lower Paraná River floodplain were selected to represent all the SL dynamics identified. Ten SL were permanently connected and 15 were disconnected from watercourses. Water and sediment physical and chemical characteristics, macrophyte assemblage composition, and plant species abundance were surveyed at each site in the 2018 summer. Also, SL morphometric parameters and flood frequency were estimated from ancillary geographic data. The direct controlling factors of macrophyte assemblages were water ammonium and water nitrate concentrations, turbidity, and flood frequency. No clear effects of environmental conditions on macrophyte diversity were found. The connectivity of SL with watercourses affected their water and sediment physical and chemical features. Also, SL dynamics during the 2017 pulse were related to flood frequency. As connectivity to watercourses affects SL chemical and physical variables, and SL dynamics were associated with flood frequency, connectivity and SL dynamics indirectly influenced macrophyte assemblage composition. This study improved our understanding of macrophyte distribution patterns in the study area, which was related to several environmental variables operating at different scales. Our results highlight the importance of the variability of hydrological connectivity in promoting environmental heterogeneity in river floodplain systems, which is central to their functioning, and the high biodiversity that characterises these environments.

Species-Level Versus Community-Level Responses to Microhabitat Type and Diversity in an Experimental Plant Community

Soil heterogeneity has been theoretically predicted to promote plant performance, but empirical evidence is often mixed. By focusing on a gradient of microhabitats (single, three and six types of microhabitats), we tested the hypothesis that increasing the number of microhabitats promotes the diversity and productivity of plant communities. We created different types of microhabitats by adding different forms of nitrogen (NH4+, NO3− and glycine) or combinations of these nitrogen in an even or patchy way. Community biomass, but not evenness, differed in different types of single-microhabitat. Increasing the number of microhabitat types did not alter community growth or evenness, but it increased the difference in the relative abundance of plant species within the community. These results suggest that microhabitat diversity can influence plant competitive hierarchies, and that this effect can lead to changed community growth, but may not be decisive for plant evenness.

PSXII-12 Heritage Raramuri Criollo Cattle Production as a Potential Strategy for Conservation of Black Grama in the Chihuahuan Desert

Abstract The Chihuahuan desert ecosystem has experienced a decrease in black grama (Bouteloua eriopoda), a perennial grass species with high ecological value, alongside a subsequent increase in mesquite (Prosopis glandulosa). This trend is thought to be due to several management- and environment-related factors. We compared diet selection of a heritage Raramuri Criollo (RC) vs. Angus-X-Hereford (AH) cattle, typical of the region, using fecal DNA metabarcoding conducted by a commercial laboratory to determine the proportion of black grama and mesquite in samples. RC and AH cows grazed two adjacent pastures (~1,100 ha) separately, switched at the mid-point of each period. Rectal fecal samples were collected from 10 cows/ breed/ pasture/ period. The study was replicated across seasons (growing and dormant) for three consecutive years (240 total fecal samples) in a completely randomized design. Relative abundance of plant species was ranked over the entire study and by season. The MIXED procedure of SAS 9.4 was used to analyze the proportions of black grama and mesquite in fecal samples by breed, season, year, and all interactions. Black grama was a more important forage resource than mesquite (ranked 8 vs. 11), particularly during dormancy (ranked 3 vs. 7). When examined by breed, AH fecal samples had twice the percentage of black grama vs. RC (P< 0.05) and even more so during the dormant season (P< 0.05). In contrast, RC fecal samples tended to contain a greater percentage of mesquite (P=0.05). Adjustments for BW differences between breeds (545 vs. 350 kg mean BW for AH vs. RC respectively) suggest that AH consumed 3.09-fold more black grama while RC consumed 1.59 times more mesquite. Differences in diet composition appear to support the hypothesis that RC cattle could impose a lighter grazing pressure on black grama populations, potentially serving as a conservation management tool on Chihuahuan Desert rangelands.

Effect of Irrigation, Nitrogen Sources, and Metribuzin on Performance of Maize and Its Weeds

ABSTRACT Exploiting water and nutrients by crop plants is limiting by abundance of undesirable plant species viz weeds due to their competitiveness ability, affecting crop productivity and quality. Thus, over two seasons of 2017 and 2018, field experiment was carried out at the Experimental Farm of Faculty of Agriculture, Ain Shams University, Egypt to study the response of maize grain yield and its nutrient constituents and associated weeds to two irrigation intervals (every 15 and 22 days), three weed control treatments (hoeing twice, metribuzin, and unweeded) as well as three nitrogen forms (ammonium nitrate, ammonium sulfate, and urea). The tested factors distributed in a strip plots design with four replications. The results showed that dry weight of grasses (56.1 g m−2) and total weeds (67.2 g m−2) were lower with irrigation every 15 day. Irrigation every 15 day gave the maximum increase in plant height (233 cm), ear length (18.4 cm), ear diameter (4.7 cm), 100 grain weight (28.0 g), grain yield (7.58 ton ha−1) and leaf P (0.29%) and K (2.07%) contents. Hoeing gave the lowest biomass of grasses, total weeds and weeds potassium content, while metribuzin was the superior in diminishing broadleaf weed biomass. Hoeing was as similar as metribuzin as in enhancing plant height, ear length, 100 grain weight and grain yield ton ha–1. Nitrogen (N) form had no significant effect on weed biomass. However, ammonium nitrate was the most effective form at promoting 100 grain weight, ear length, grain yield ton ha–1 and maize leaf potassium content. Results exhibited that irrigating maize fields every 15 day × hoeing or metribuzin × ammonium sulfate–N could be a combatable and integrative pattern for diminishing weed growth and keeping crop productivity.

Using superpixel- or pixel-based segmentation for efficient green roof digital image classification and rapid estimation of plant species cover

Green roofs are “nature-based solutions” that provide numerous ecosystem services in the context of urban green infrastructures. Plant species diversity and the associated vegetation communities, in strong interactions with green roof substrate, play a central role in the green infrastructure functioning. In order to better understand the influence of vegetation in relation with the co-benefits provided by green roofs as well as to select suitable species for these usually harsh environments, it is essential to be able to achieve accurate and long-term monitoring of plant communities. In this short communication, two free plugins recently developed for the open-source image analysis software Fiji (a distribution of the freely available ImageJ platform, initially dedicated to biological image analysis) were investigated for their capacity to rapidly and efficiently perform supervised machine-learning for the classification of green roof vegetation photographs, with the aim of estimating individual plant species abundance. Two simple methods are thus described using the Trainable Weka Pixel Segmentation (Arganda-Carreras et al., 2017) or the Trainable Superpixel Segmentation (Salinas Colina et al., 2018), which allowed for rapid, efficient and reproducible classification and estimation of multispecies colonized green roof regardless the color or shape similarities among species or ground cover materials. Finally, recommendations are made for the use of the Trainable Superpixel Segmentation which is particularly convenient for quick and efficient green roof image analysis.

Impacts of Parthenium hysterophorus L. on Plant Species Diversity in Ginir District, Southeastern Ethiopia

Invasive alien species are considered the second greatest global threat to biodiversity. This study is aimed at determining the impacts of Parthenium hysterophorus on herbaceous and woody plant species diversity in the Ginir district, southeast Ethiopia. Data on vegetation were collected from the three study sites’ four land use types, with each land use type having invaded and non-invaded land units. A systematic random sampling method was used for establishing sampling plots. To examine the impacts of the invasive on native plant diversity, a total of 160 plots (120 plots of 1 m2 on grazing lands, roadsides, and abandoned agricultural lands and 40 plots of 20 m2 for sampling herbaceous and tree (shrub) species, respectively) were established. The number of plots was equally distributed in both invaded and adjacent non-invaded areas. Plant species from each plot were recorded and identified. In each plot, all the individuals of P. hysterophorus were counted, the heights of the five tallest individuals were measured, and the mean height was calculated. The percentage cover of P. hysterophorus was visually estimated. The data were analyzed using both descriptive and inferential statistics. A total of 105 plant species (45 trees/shrubs and 60 herbaceous) belonging to 84 genera and 42 families were documented in the study area. The result showed a strong negative relationship between the density of P. hysterophorus and other plant species richness (r = −0.82, p = 0.013) and species abundance (r = −0.917, p = 0.001) per study site of the invaded community. Species richness in the non-invaded site was higher (105 species) than in the invaded area (63 species), demonstrating the negative impact of P. hysterophorus on local biodiversity. Furthermore, the number of plant families was 42 in the non-invaded area, in contrast to only 32 in the invaded areas, a 23.8% decline. Of the plant communities, similarity indices between non-invaded and invaded sites among different land use types were >50%. It was concluded that P. hysterophorus was one of the most dominant invasive alien species in the study area that reduced the species diversity of various plant species. Putting in place a strategy and effective planning for the control and management of this invasive alien species is strongly recommended.

DIVERSIDAD Y ABUNDANCIA DE VEGETACIÓN NATIVA E INTRODUCIDA EN PASTIZALES DE TANTOYUCA, VERACRUZ, MÉXICO

<p><strong>Background</strong>.<strong> </strong>Tantoyuca, Veracruz presents a great diversity of vegetation in the grasslands and its main economic activity is cattle ranching, in which two production systems are managed (dairy and meat). <strong>Objective</strong>.<strong> </strong>The objective was to assess the diversity and abundance of native and introduced vegetation present in the dairy and meat production systems of the grasslands of Tantoyuca, Veracruz, Mexico. <strong>Methodology</strong>. The floristic composition, structure, diversity, richness and conservation value were estimated from the inventory and abundance of plant species obtained by sampling by linear transects in ten dairy or meat grasslands. The Shannon and Simpson true diversity indices were generated and the relative abundances of the vegetation diversity were obtained. The relationship between species diversity and grasslands was performed with the ꭕ2 test. An inventory of pastures used in grasslands was represented on a vector map with the information obtained from 76 surveyed ranchers. <strong>Results</strong>.<strong> </strong>In the grasslands, 130 species, 107 genera and 50 families were identified, distributed in 68.5% herbs, 29.5% shrubs and 2% vines, and the similarity of plant diversity in both systems (dairy and meat) was evidenced. The most commonly used grasses are <em>Urochloa decumbens</em> Stapf and <em>Cynodon nlemfuensis</em> Vanderyst. The pastures were characterized by the low presence of introduced species (10) and a high diversity of native plants (120) used by livestock. In both systems there are high incidences of native legumes and species that indicate poor grazing management such as: <em>Desmodium incanum</em> (Sw.) DC. and <em>Achyranthes aspera</em> L. <strong>Implications</strong>. The information presented in this research is useful in the design of restoration plans with herbaceous and shrub vegetation, as well as serving as a basis for making management decisions for grazing with cattle in the grasslands of the Tantoyuca, Veracruz. <strong>Conclusion</strong>. Based on the sampling of herbaceous, shrub and vine vegetation, the high presence of native and naturalized species that can be used in the grasslands was highlighted. In the meat pastures of Tantoyuca, Veracruz, with the average biological value index and low species richness, it would be advisable to carry out repopulation practices with legumes and native and naturalized grasses.</p>

Pollen Preference Patterns by Tetragonisca angustula (Apidae: Meliponini) in a Boliviano-Tucumano Forest.

Native bees are important pollinators in neotropical forests. Tetragonisca angustula (Latreille) (Apidae: Meliponini) is a stingless bee widely distributed from the south of Mexico to Argentina. We characterized the patterns of preference of T. angustula for pollen in relation to the richness and abundance of plant species in the Tucumano-Boliviano Forest. During two field campaigns in different seasons (winter and spring), six colonies of T. angustula were studied. Pollen from flowers of plant species in the study area (pollen offer) and pot-pollen in each hive (pollen demand) were collected and their plant family of origin identified. Pollen from Asteraceae was more abundant in the winter than in the spring. Pollen of Solanaceae in the winter and Bignoniaceae in the spring were the most selected by the worker bees. Pollen from plants outside the sampling area was also found in the pots; it was mainly from Asteraceae. Tetragonisca angustula workers showed a polylectic foraging behavior, being able to use in a dynamic way the resources that are present in their environment at different times of the year; occasionally, it selected less abundant specific resources likely based on their nutritional value. More studies are needed to evaluate aspects of pollen quality consumed by this bee.