Flooding, topography, and successional age as determinants of species diversity in old-field vegetation

1996 ◽  
Vol 74 (4) ◽  
pp. 582-588 ◽  
Author(s):  
Hernán J. Trebino ◽  
Enrique J. Chaneton ◽  
Rolando J. C. León
Keyword(s):  
Species Richness ◽  
Species Diversity ◽  
Early Stage ◽  
Biotic Interactions ◽  
First Year ◽  
Spatial And Temporal Patterns ◽  
Old Field ◽  
Flood Disturbance ◽  
Topographic Positions ◽  
Topographic Gradients

We studied the spatial pattern of plant richness and diversity along topographic gradients in two pairs of plots with 3 and 4 versus 9 and 10 years of abandonment from cultivation, in the Inland Pampa of Argentina. Vegetation in each plot was sampled for species cover every 10 m along a transect running parallel to the maximum local slope. Observations began after 2 years of unusually severe floods and continued for over 6 years. Community richness and diversity both increased with topographic height only the first year after flooding, in young and old successional plots. Richness and diversity decreased over time in upper and intermediate topographic positions, converging toward lesser values observed in lower positions. A transient peak in diversity occurred in lower topographic positions several years after flood disturbance. Species richness was similarly constrained by flooding stress and successional development. Thus, maximum diversity occurred at an early stage of succession in upper, infrequently flooded sites. Spatial and temporal patterns of plant diversity in this successional system did not generally conform with predictions from intermediate disturbance models. We propose that control of species diversity in old-field vegetation changed with time since flooding from physical stress to strong biotic interactions. Keywords: pampean grasslands, secondary succession, disturbance and stress gradients, species richness, vegetation structure.

scholarly journals Plant community diversity and composition provide little resistance to Juniperus encroachment

Botany ◽  
2008 ◽  
Vol 86 (12) ◽  
pp. 1416-1426 ◽  
Author(s):  
Amy C. Ganguli ◽  
David M. Engle ◽  
Paul M. Mayer ◽  
Eric C. Hellgren
Keyword(s):  
Species Richness ◽  
Species Diversity ◽  
Species Composition ◽  
Plant Species ◽  
Plant Community ◽  
Tallgrass Prairie ◽  
Abiotic Factors ◽  
Community Diversity ◽  
Oak Forest ◽  
Old Field

Widespread encroachment of the fire-intolerant species Juniperus virginiana  L. into North American grasslands and savannahs where fire has largely been removed has prompted the need to identify mechanisms driving J. virginiana encroachment. We tested whether encroachment success of J. virginiana is related to plant species diversity and composition across three plant communities. We predicted J. virginiana encroachment success would (i) decrease with increasing diversity, and (ii) J. virginiana encroachment success would be unrelated to species composition. We simulated encroachment by planting J. virginiana seedlings in tallgrass prairie, old-field grassland, and upland oak forest. We used J. virginiana survival and growth as an index of encroachment success and evaluated success as a function of plant community traits (i.e., species richness, species diversity, and species composition). Our results indicated that J. virginiana encroachment success increased with increasing plant richness and diversity. Moreover, growth and survival of J. virginiana seedlings was associated with plant species composition only in the old-field grassland and upland oak forest. These results suggest that greater plant species richness and diversity provide little resistance to J. virginiana encroachment, and the results suggest resource availability and other biotic or abiotic factors are determinants of J. virginiana encroachment success.

scholarly journals Effects of Herbaceous Competition Control on Wildlife Habitat Quality in Piedmont Pine Plantations

2003 ◽  
Vol 27 (1) ◽  
pp. 55-60 ◽  
Author(s):  
P.D. Keyser ◽  
V.L. Ford ◽  
D.C. Guynn
Keyword(s):  
Species Richness ◽  
Species Diversity ◽  
Habitat Quality ◽  
Block Design ◽  
Site Preparation ◽  
Wildlife Habitat ◽  
Pine Plantations ◽  
First Year ◽  
Preparation Methods ◽  
Competition Control

Abstract Wildlife biologists have become increasingly concerned about the effects of herbaceous competition control in pine plantations on wildlife habitats. Data from a study designed to test the effectiveness of herbaceous weed control with different site preparation methods were re-analyzed to assess effects on various measures of wildlife habitat quality. Three rates of Oust® (0, 2, and 4 oz/ac) were applied in mid-April the first year to planted loblolly pine seedlings at seven locations (each a complete randomized block design) in the Virginia Piedmont. Site preparation methods used were pile only (two locations), burn only, chop and burn, pile and disk, and Velpar® and burn (two locations). Results were re-analyzed to assess effects of these methods on total herbaceous vegetation coverage, forage coverage, the ratio of forage/cover, species richness, and species diversity. Although total herbaceous coverage and species richness declined in the first year after application on many locations, vegetation rebounded in the second and/or third year. Few significant differences were observed in forage coverage, the ratio of forage to cover, or species diversity. By the third year, few differences remained among treatment levels. Mechanical site preparation appeared to have less impact on all measures than chemical site preparation. South. J. Appl. For. 27(1):55–60.

Experimental removal of a dominant species at two levels of soil fertility

1989 ◽  
Vol 67 (12) ◽  
pp. 3470-3477 ◽  
Author(s):  
Jessica Gurevitch ◽  
Robert S. Unnasch
Keyword(s):  
Species Richness ◽  
Species Diversity ◽  
Soil Fertility ◽  
Dominant Species ◽  
Dactylis Glomerata ◽  
Common Species ◽  
Herbaceous Plant ◽  
Old Field ◽  
Steep Decline ◽  
Dactylis Glomerata L

Fertilization of the soil in herbaceous plant communities has been observed to lead to an increase in productivity but a decline in species richness and diversity. We tested the hypothesis that the decline in diversity is due to increased competition from a dominant species by removing the dominant species, Dactylis glomerata L., from an old field community with and without fertilization. Fertilization without the removal of Dactylis resulted in a steep decline in species numbers and in species diversity. The removal of Dactylis when fertilizer was added prevented the decline in species richness. Removal of this dominant species led to an increase in species diversity, an increase in either the frequency or the abundance of almost half of the common species in the system, and an increase in the combined biomass of uncommon species. The response to the removal of Dactylis was greater at higher than at low soil fertility for most but not all variables. Key words: old-field, fertilization, competition, species diversity, community structure, Dactylis glomerata.

A FIRST-YEAR STUDENTS’ ADAPTATION TO DIFFICULTIES AT HIGH EDUCATIONAL ESTABLISHMENTS

2021 ◽  
pp. 97-113
Author(s):  
Nailya R. Salikhova ◽  
◽  
Aida R. Fakhrutdinova ◽  
Keyword(s):  
Higher Education ◽  
Personal Growth ◽  
Personal Development ◽  
Early Stage ◽  
Educational Process ◽  
First Year ◽  
First Year Students ◽  
Social Community ◽  
Transition To Higher Education ◽  
Study Participants

Data from an empirical study aimed at identifying the difficulties faced by students in their transition to higher education, the overcoming of which is important for personal development, are presented in the article. The study participants (n=179) were asked to describe the difficulties of transition from school to University in the 1st year based on analysis of their autobiographical memory. The content analysis of texts allowed identifying the main themes and compiling a list of challenges, and then the frequency of occurrence of each of them was determined. According to the results, the most actual difficulties are the different aspects of integrating into the new social community due to sharp changes in the social environment during the transition from school to University. A big challenge is the need for self-organization in educational and everyday matters, planning and organizing your time. The third most frequently mentioned is learning difficulties, especially those related to mastering the material in the new educational environment. Problematic areas of adaptation to higher education that have not been previously reflected in the sources are the establishment of a common life in the dormitory, pressure from parents, the manifestation of their individuality, the increase in the length of classes and the pace of learning, romantic relationships and language barriers. The difficulties of the first examination session are much less frequently mentioned, and are more frequently mentioned when examining the current adaptation process. The results of the study can be used for the development and subsequent implementation of a system of practical measures aimed at helping students to adapt to the new environment and conditions. Such assistance to students in building a new way of life at a university, especially at an early stage of study, is necessary not only to improve the effectiveness of the educational process, but also to facilitate the processes of personal growth and development of students

scholarly journals What Does Productivity Really Mean? Towards an Integrative Paradigm in the Search for Biodiversity-Productivity Relationships

2013 ◽  
Vol 41 (1) ◽  
pp. 36 ◽  
Author(s):  
Liangjun HU ◽  
Qinfeng GUO
Keyword(s):  
Species Richness ◽  
Species Diversity ◽  
Biomass Production ◽  
Real Root ◽  
Spatial Scaling ◽  
Ecological Processes ◽  
The Real ◽  
Community Or ◽  
Per Se ◽  
Underlying Mechanisms

How species diversity relates to productivity remains a major debate. To date, however, the underlying mechanisms that regulate the ecological processes involved are still poorly understood. Three major issues persist in early efforts at resolution. First, in the context that productivity drives species diversity, how the pathways operate is poorly-explained. Second, productivity  per se varies with community or ecosystem maturity. If diversity indeed drives productivity, the criterion of choosing appropriate measures for productivity is not available. Third, spatial scaling suggests that sampling based on small-plots may not be suitable for formulating species richness-productivity relationships (SRPRs). Thus, the long-standing assumption simply linking diversity with productivity and pursuing a generalizing pattern may not be robust. We argue that productivity, though defined as ‘the rate of biomass production’, has been measured in two ways environmental surrogates and biomass production leading to misinterpretations and difficulty in the pursuit of generalizable SRPRs. To tackle these issues, we developed an integrative theoretical paradigm encompassing richer biological and physical contexts and clearly reconciling the major processes of the systems, using proper productivity measures and sampling units. We conclude that loose interpretation and confounding measures of productivity may be the real root of current SRPR inconsistencies and debate.

scholarly journals Composition and diversity of anurans in the Restinga of the Conde municipality, northern coast of the state of Bahia, northeastern Brazil

2016 ◽  
Vol 16 (3) ◽  
Author(s):  
Felipe Augusto Trindade Gondim-Silva ◽  
Alessandra Rodrigues Santos Andrade ◽  
Rafael Oliveira Abreu ◽  
Jamile Santos Nascimento ◽  
Geovane Paixão Corrêa ◽  
...  
Keyword(s):  
Species Richness ◽  
Species Diversity ◽  
Species Composition ◽  
Rainy Season ◽  
Dominant Species ◽  
The State ◽  
Northeastern Brazil ◽  
Freshwater Wetland ◽  
Northern Coast ◽  
Anuran Species

Abstract The Conde municipality is located in the northern coast of the state of Bahia (NC), northeastern Brazil, and is part of the Atlantic Tropical domain. The anuran fauna of the northern portion of the NC is still poorly known if compared to the southern portion. The Restinga is one of the predominant environments of the coastal plains of the NC and it is characterized essentially by presenting sandy soil covered by herbaceous and shrubby vegetation. The objective of this study was to determine the anuran species composition and diversity for the Restinga of the Conde municipality. Sampling was carried out at night by active search over four periods of five consecutive days each, two over the 'main rainy season' and two in a 'lesser rainy season', using 14 sample units (SUs) and five extra sample plots (EPs). We calculated dominance and species diversity using the Berger-Parker and Shannon-Wiener H' indices, respectively. We used accumulation curves and the Jackknife 1 estimator to estimate anuran species richness, considering only the data obtained from the SUs. We recorded 713 anuran specimens distributed within 33 species, 13 genera and five families (Bufonidae, Craugastoridae, Hylidae, Leptodactylidae and Microhylidae). The Hylidae and Leptodactylidae families had the highest species richness. Considering only the SUs (Jackknife 1 estimator in brackets), we recorded 28 species in the study area (33.9 ± 2.3), 13 in Shrubby Vegetation Zones - SVZ (20.8 ± 2.9) and 25 in Freshwater Wetland Zones - FWZ (28.9 ± 1.9). The abundance and species diversity of the FWZ (n = 638 specimens; H'= 2.4) were higher than those recorded for the SVZ (n = 52 specimens; H' = 1.9). The SVZ and FWZ showed distinct dominant species, wherein Pristimantis paulodutrai was the dominant species in SVZ and Scinax fuscomarginatus in FWZ. The Restinga of the Conde municipality stands out as the one with the highest anuran species richness already recorded considering only SVZ and FWZ. Moreover, its anuran species composition represented 55% of the anuran species known for the NC and included taxa common to three different morphoclimatic domains (Tropical Atlantic, Cerrado and Caatinga).

scholarly journals Fish species diversity in headwaters streams of Paraguay and Paraná Basins

2007 ◽  
Vol 50 (6) ◽  
pp. 1033-1042 ◽  
Author(s):  
Yzel Rondon Súarez ◽  
Sabrina Bigatão Valério ◽  
Karina Keyla Tondado ◽  
Alexandro Cezar Florentino ◽  
Thiago Rota Alves Felipe ◽  
...  
Keyword(s):  
Species Richness ◽  
Species Diversity ◽  
Environmental Factors ◽  
Fish Species ◽  
Total Species Richness ◽  
Paraná Basin ◽  
Parana Basin ◽  
Number Of Individuals ◽  
Total Species ◽  
Fish Species Diversity

The influence of spatial, temporal and environmental factors on fish species diversity in headwater streams in Paraguay and Paraná basins, Brazil was examined. A total of 4,605 individuals were sampled, distributed in 60 species. The sampled streams in Paraná basin presented a larger total species richness (42) than Paraguay streams (40). However the estimated richness was larger in Paraguay basin (53) than Paraná streams (50). The streams of Paraná basin had a greater mean species richness and evenness, while more individuals per sample were found in the Paraguay basin. Difference between the sub-basins were found in the Paraguay basin, while for the basin of Paraná, richness and evenness vary significantly between the sub-basins, but the number of individuals varied seasonally. The most important environmental factors to species diversity and abundance were altitude, water temperature, stream width and stream depth for both the basins.

Diverse perennial crop mixtures sustain higher productivity over time based on ecological complementarity

2011 ◽  
Vol 26 (4) ◽  
pp. 317-327 ◽  
Author(s):  
Valentín D. Picasso ◽  
E. Charles Brummer ◽  
Matt Liebman ◽  
Philip M. Dixon ◽  
Brian J. Wilsey
Keyword(s):  
Species Richness ◽  
Species Diversity ◽  
Biomass Production ◽  
Cropping Systems ◽  
Individual Species ◽  
Selection Effects ◽  
Complementarity Effect ◽  
Change Over Time ◽  
Diversity Effects ◽  
Over Time

AbstractCropping systems that rely on renewable energy and resources and are based on ecological principles could be more stable and productive into the future than current monoculture systems with serious unintended environmental consequences such as soil erosion and water pollution. In nonagricultural systems, communities with higher species diversity have higher productivity and provide other ecosystem services. However, communities of well-adapted crop species selected for biomass production may respond differently to increasing diversity. Diversity effects may be due to complementarity among species (complementary resource use and facilitative interactions) or positive selection effects (e.g., species with higher productivity dominate the mixture), and these effects may change over time or across environments. Our goal was to identify the ecological mechanisms causing diversity effects in a biodiversity experiment using agriculturally relevant species, and evaluate the implications for the design of sustainable cropping systems. We seeded seven perennial forage species in a replicated field experiment at two locations in Iowa, USA, and evaluated biomass productivity of monocultures and two- to six-species mixtures over 3 years after the establishment year under management systems of contrasting intensity: one or three harvests per year. Productivity increased with seeded species richness in all environments, and the positive relationship did not change over time. Polyculture overyielding was due to complementarity among species in the community rather than to selection effects of individual species. Complementarity increased as a log-linear function of species richness in all environments, and this trend was consistent across years. Legume–grass facilitation may explain much of this complementarity effect. Although individual species with high biomass production had a major effect on productivity of mixtures, the species producing the highest biomass in monoculture changed over the years in most environments. Furthermore, transgressive overyielding was observed and was more prevalent in later years, in some environments. We conclude that choosing a single well-adapted species for maximizing productivity may not be the best alternative over the long term and that high levels of species diversity should be included in the design of productive and ecologically sound agricultural systems.

Competitive Effects and Responses Between Plant Species in a First-Year Old-Field Community

Ecology ◽  
1987 ◽  
Vol 68 (5) ◽  
pp. 1201-1210 ◽  
Author(s):  
T. E. Miller ◽  
P. A. Werner
Keyword(s):  
Plant Species ◽  
First Year ◽  
Old Field ◽  
Competitive Effects
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