I hypothesized that vegetation and physical environmental characteristics would differ between the upper and lower extents of the annually flooded riparian zone on the John Day River, and that relationships between species and environmental variables would display differences between these two zones. Vegetation, environmental variables, and relationships between them were assessed for the entire annually flooded riparian zone, and for the proposed upper and lower zones. Data were collected from 60 one-square-meter quadrats: 30 in each the upper and lower zones. Sites were randomly selected and located so that flood duration was roughly equal at all sites within each zone. 34 plant species were encountered: 25 in the upper zone, 27 in the lower zone. Wetland obligate and facultative wetland species groups and eight individual species accounted for statistically different percentages ofquadrat cover between zones. ANOSIM analysis identified two statistically distinct vegetation communities between the two zones. Soil texture averaged 75.85% sand and 20.81% fines. Sand ranged between 36.69% and 95.55%. Fines ranged between 2.54% and 58.84%. A horizon depths and fine soil particle concentrations were greater in the upper zone. Coarser soils with more sand and gravel dominated the lower zone. All enviromnental variables studied, except pH, were highly variable throughout the study area. ANOSIM analysis results suggest that the upper and lower zones have distinct, statistically different physical environments from each other. Regression analyses relating species quadrat cover to physical environmental variables were performed for the total, upper, and lower riparian zones. Numerous differences were identified between the upper and lower riparian zones that the riparian scale analyses did not represent accurately. There were ten instances in which the zone scale analyses identified a relationship in either the upper or lower zone, while the corresponding riparian scale analysis failed to identify any relationship. The results of this study indicate that vegetation and the physical environment are statistically different between the upper and lower zones on this river, and that relationships between a given plant species and environmental variable can vary between zones. Future research and management efforts should consider and address the potential for such between-zone variation.

No description available.

No description available.

Angola is a tropical country with many biogeographical units and, therefore, has a high floristic diversity. Although an increasing number of floristic studies has been carried out in Angola in recent years, the country is still considered to be underinvestigated as many species being collected were previously unknown there. Several scientific groups working in different parts of Angola contributed to this paper their data from biodiversity assessments. With this we can add 67 species newly recorded for Angola, including two new generic records and five alien species, to the almost 7,300 vascular plant taxa known so far for Angola. Most of the new records for Angola are also present in different neighbouring countries, but they are little known, and their IUCN threat status has not been assessed yet. However, ongoing fieldwork and exploration are needed to complete the floristic knowledge of the understudied country.

Thesis (MSc (Conservation Ecology and Entomology)--University of Stellenbosch, 2006. / Swartland Shale Renosterveld is restricted to fertile fine-grained soils in the winter rainfall region of the Western Cape. Between 91% and 97% of this vegetation type is transformed, mostly due to agriculture. Remaining fragments have an irreplaceable conservation value due to a high richness of endemic geophytes. Information on renosterveld vegetation composition and response to disturbance is sparse. Research occurred at three sites near Wellington: Voëlvlei Provincial Nature Reserve (CapeNature), Elandsberg Private Nature Reserve (Elandsberg Farms (Pty.) Ltd.), and Krantzkop munitions factory (Armscor/Somchem) forming a contiguous fragment in the Agter- Groeneberg Conservancy. The primary research aim was to identify or ascertain patterns of plant succession in Swartland Shale Renosterveld and associated different-aged old fields (previously ploughed), with the interaction of grazing. The key research questions are: (1) What are the plant communities of unploughed renosterveld and different-aged old fields which originated in habitats of ploughed renosterveld? (2) What are the most characteristic features of the floristic and ecological relationship between the described plant communities in terms of ecological factors operating within the studied system? (3) Does total species and life-form group richness differ between natural vegetation and old fields? (4) Is life-form richness influenced by ploughing and grazing or the interaction between these disturbances? (5) Is life-form cover-abundance influenced by ploughing and grazing or the interaction between these disturbances? (6) Does alien plant species richness differ amongst seres, and with different levels of grazing intensity? A comparison of life-form richness and cover-abundance of old field vegetation was made with adjacent natural unploughed “controls”. The effects of ploughing on community structure, with the inclusion of grazing was established. These life-form richness comparisons also occur across a gradient of increasing large mammalian herbivore grazing intensity. Sampling was conducted in winter and spring using nested 1000m2 relevés. A hierarchical classification, description and floristic interpretation of renosterveld and old field vegetation were made using TWINSPAN, SYN-TAX 2000 and CANOCO. The samples were classified with TWINSPAN and two communities were described at the association level, namely: Ursinia anthemoides–Cynodon dactylon Grassland Community (with two variants) and the Pterygodio catholici–Elytropappetum rhinocerotis Shrubland Community (with two subassociations), respectively. The vegetation data were further hierachically classified using SYNTAX 2000 which revealed similar clustering of sample objects to that resulting from classification and ordination. Following ordination of sample objects with CANOCO, select groups of species were used to depict their response curves in relation to seral development. Briefly it was found that the effects of grazing vs. non-grazing was more pronounced on old fields than in unploughed vegetation. Overall total species and life-form richness was reduced by ploughing with old fields requiring a recovery period of 30 years to resemble unploughed vegetation. Keywords: Swartland Shale Renosterveld, phytosociology, vegetation patterns, life-forms, succession, disturbance, ploughing, grazing, old fields.

The project was initiated by Eastern Cape Parks (ECP) as a request for the construction of inventories of priority species and their population levels inside three nature reserves on the Eastern Cape Wild Coast, South Africa, and to develop a strategic management plan to manage these natural resources in each reserve. Thirty key species were identified by local communities in and around Dwesa-Cwebe, Silaka and Mkambati Nature Reserves through community workshops. For forested areas belt transects of 100 m x 6 m where used. The basal circumference of key tree species within the belt transect was measured as well as the height of saplings (height < 150 m). Tree species were categorized based on densities, size class distribution (SCD) curves and values, and spatial grain. For grassland areas straight transects of 200 m long were used, along which ten 3 m x 3 m quadrates were placed at 20 m intervals. Within each grassland transect the height of herbs or tuft diameter of grasses was recorded and percentage cover estimated. Grassland species were categorized based on density, SCD curves and percentage cover. All species were placed into harvesting categories based on analysed ecological data that was collected in the field. Category 1 species were very rare or not found in the reserve and it was recommended that species be conserved and monitored. Category 2 species had low densities in the reserve indicating declining populations and was suggested that these be monitored and not harvested. Category 3 species had high densities and have potential for harvesting with strict limitations. Category 4 species were most abundant with very high densities and can be harvested within management guidelines. These categories were grouped further using social and ecological data such as harvesting risk, frequency of collection, use value and number of uses. This highlighted which species have conservation priority within each category and a decision can be made as to how intense or limited extraction should be. By incorporating GIS the distribution of each species was looked at and harvesting and non-harvesting zones established to determine where species can be extracted. Monitoring plans must consider the quantity of plant material collected, fire regimes, optimal harvesting rates and harvesting zones, and be able to pick up changes in populations. Also, it is important that the community be involved in conserving and monitoring these species. Adaptive monitoring and management must be used to steer harvesting practices in the Wild Coast reserves. This allows for the development of harvesting practices through ‘learning by doing’, and the evolution of good questions to guide monitoring decisions

This study examined the current plant diversity status and the impact of drivers of change on the peat basins of the Kromme River peatland. It was conducted at six sites over sixty one years in the Eastern Cape Province of South Africa. I reviewed the rapid habitat and biodiversity loss of wetlands globally and discussed the distribution of wetlands and specifically peatlands in South Africa. Plant species diversity was assessed using Modified- Whittaker plots. The influence of environmental variables on floristic composition and distribution was investigated using ordination techniques (DCA and CCA). Land use dynamics were assessed by applying GIS techniques on orthorectified aerial images. Six different peat basins were subjectively classified into good, medium and poor condition peat basins. The good condition peat basin (Krugersland) was the most diverse in plant species (4.1 Shannon-Weiner’s index) (p> 0.20; F = 11.04; df = 2), with the highest mean number of plant species (32.5 ± 3.4). This was followed by the medium condition class (Kammiesbos) (26.5 ± 9.0) and poor condition class (Companjesdrift) (22.5 ± 8.9). On average, species composition was not evenly distributed across the peat basins (p> 0.21; F = 0.94; df = 2), since 77.8% of the Shannon-Weiner evenness index obtained were less than one. However, there were variations in plant species richness across six peat basins as confirmed by Oneway ANOVA test (p= 0.0008, F = 1241.6, df = 4). Key environmental variables that influenced plant species distribution and structure were erosion and grazing intensity, potassium, phosphorus, soil pH and calcium. Total species variance accounted for in the first two axes for ground cover and plant height were 40.7% and 56.4% respectively. Alien species (e.g. Acacia mearnsii and Conyza scabrida) were common in degraded peat basins, whereas good condition peat basins supported indigenous species (e.g., Cyperus denudatus, Chrysanthemoides monolifera and Digitaria eriantha). Analysis of aerial images revealed a general progressive decrease in the peatland area between 1942 and 1969 in the good (Krugersland) and poor (Companjesdrift) condition class, with a marginal increase from 1969 to 2003. Peatland area in the good and poor condition class decreased by 5.3% and 8.3% respectively between 1942 and 1969, with a marginal increase of 1.5% and 4.1% respectively from 1969 to 2003. Annual net rate of change in peatland area over the 61 year period was -0.32% (good condition class) and - 0.79% (poor condition class). Transformed lands were impacted by drivers of change such as alien invasives, agricultural activities, erosion and sediment transport. The area under alien invasives increased by 50% between 1942 and 2003, with an annual net rate of change of +0.82 (good condition class) and +1.63% (poor condition class).

Abstract Boreal and arctic plant communities are responding to anthropogenic climate change that has been exceptionally rapid during the recent decades. General responses include increased productivity, range expansions and biodiversity changes, all of which affect ecosystem functions. Vegetation dynamics are however controlled by multiple drivers, and the outcomes under the changing climate are not yet fully clear. As high latitude areas often lack long-term monitoring of vegetation, alternative methods are required to observe and understand vegetation changes and dynamics. Recently, resurveying historical vegetation data has become a valuable method of studying vegetation changes over the past few decades. In this thesis, I studied multidecadal (23–60 years) vegetation changes in forest and treeless heath and tundra plant communities along a latitudinal gradient in northern Fennoscandia using both vegetation resurveys and long-term experimental data. In addition to examining climate-driven vegetation changes, I related changes in plant communities to key local drivers of each context including mesotopography, grazing, soil moisture and soil fertility. General trends among the resurveyed treeless heath sites were the pronounced increase of the dwarf shrub Empetrum nigrum ssp. hermaphroditum in snow-protected habitats and the decrease of lichens throughout. Southernmost heath communities showed strong responses to multidriver effects and had shifted towards new community states. The long-term experiment in the tundra confirmed that depending on driver combinations, tundra communities evolve towards divergent alternative states, highlighting the importance of local drivers in modifying tundra vegetation over time. Communities in fertile forest sites experienced greater temporal turnover compared to infertile forest sites, suggesting that the soil fertility level is a key predictor of vegetation changes under climate change. This particularly important finding previously relied mainly on experimental evidence. Despite these generalities, changes in diversity, plant groups and species varied under a rather uniform climatic warming trend and were often habitat- or region-specific. Thus, the results of my thesis highly motivate continued monitoring and resurveying of vegetation under rapid environmental change and also form baseline time-series data for future studies. / Tiivistelmä Poikkeuksellisen nopea ilmastonmuutos on johtanut viime vuosikymmenten aikana muutoksiin boreaalisissa ja arktisissa kasviyhteisöissä. Muutoksiin lukeutuvat tuottavuuden lisääntyminen, levinneisyysrajojen siirtyminen sekä muutokset biodiversiteetissä, mitkä kaikki muuttavat ekosysteemien toimintaa. Kasvillisuuden dynamiikkaa säätelevät kuitenkin useat paikallistason tekijät, minkä seurauksena ei ole täysin selvää, miten kasvillisuus on eri alueilla ja habitaateissa muuttunut. Koska kasvillisuuden jatkuva monitorointi on harvinaista pohjoisilla alueilla, vanhojen kasvillisuusaineistojen uudelleenkartoituksista on tullut tärkeä menetelmä muutosten havaitsemiseksi. Tutkin väitöskirjassani vuosikymmenten kuluessa tapahtuneita (23–60 vuotta) kasvillisuusmuutoksia Pohjois-Fennoskandian metsissä, puuttomilla kankailla ja tundralla uudelleenkartoitusten ja kokeellisen tutkimuksen avulla, ja kytkin ne ilmastonmuutokseen sekä tärkeimpiin paikallisiin tekijöihin. Yleisiä trendejä uudelleenkartoitetuilla puuttomilla kankailla olivat variksenmarjan (Empetrum nigrum ssp. hermaphroditum) voimakas lisääntyminen lumensuojaisissa habitaateissa sekä jäkälien väheneminen kaikkialla. Yhteisöjen kokonaismuutos oli voimakkainta eteläisillä puuttomilla kankailla, jossa se korreloi yhtä aikaa lisääntyneiden lämpötilojen ja laidunpaineen kanssa. Kokeellinen tutkimus tundralla osoitti, että kasviyhteisöt kehittyvät hyvin erilaisiksi paikallisten tekijöiden voimakkuussuhteista riippuen, jotka voivat joko hidastaa tai nopeuttaa ympäristömuutoksista johtuvia kasvillisuusmuutoksia. Metsien uudelleenkartoitus osoitti yhteisöjen kokonaismuutoksen olevan pitkällä aikavälillä suurempaa tuottavilla maaperillä lehtometsissä verrattuna karumpiin kangasmetsiin. Tutkimuksen mukaan maaperän tuottavuus on avaintekijä, joka ennustaa kasvillisuusmuutosten voimakkuutta ilmastonmuutoksen aikana. Tästä tärkeästä löydöstä oli aiemmin pääasiassa vain kokeellista tutkimustietoa. Yleisistä trendeistä huolimatta, muutokset diversiteetissä, kasviryhmissä ja yksittäisissä lajeissa olivat kuitenkin vaihtelevia ja usein habitaatti- tai aluesidonnaisia. Väitöskirjani tulokset, jotka muodostavat myös aikasarjan tuleville tutkimuksille, osoittavat kasvillisuuden monitoroinnin ja uudelleenkartoitusten olevan ensisijaisen tärkeitä, jotta kasvillisuuden dynamiikkaa voidaan ymmärtää paremmin nopeasti muuttuvissa olosuhteissa.

Dans cette étude, les relations entre la structure forestière à l’échelle du paysage d’une part, la composition et le fonctionnement des forêts d’autre part, ont été analysées dans un écosystème de transition forêt-savane (Département de Tanda, Est Côte d’Ivoire). L’objectif principal de cette thèse était de tester l’hypothèse centrale de l’écologie du paysage, connue sous le vocable pattern-process paradigm, selon laquelle les trois composantes du système écologiques à savoir la structure, la composition et le fonctionnement, sont interdépendantes, et qu’en analysant l’une d’elle, des déductions utiles peuvent être faites sur les autres. <p>Nos résultats ont montré que l’équilibre écologique des forêts de la zone d’étude était fortement perturbé. L’agriculture itinérante sur brûlis, l’exploitation forestière et les feux de végétation ont été identifiés comme étant les principaux agents de ces dynamiques. La matrice du paysage, qui était initialement constituée d’une couverture continue de forêt dense, a été substituée par une mosaïque de savanes, de champs et de forêts exploitées, présentant des niveaux variables de dégradations anthropiques. L’utilisation de données multi-spectrales a permis de quantifier ces dégradations. Premièrement, sur base de l’information spectrale, nous avons distingué deux sous-types de forêts, différents entre eux en termes de densité, de composition, de stratégie dominante et de niveau de dégradation. Deuxièmement, une corrélation significative a été obtenue entre la dégradation et le degré de fragmentation des forêts, quantifiable à partir d’indices structuraux basés sur le nombre de taches, la proportion de forêts et le périmètre des taches forestières dans le paysage. La fragmentation semble avoir produit deux effets distincts sur la composition forestière ;elle détermine la taille et l’isolation des fragments aussi bien que les lisières forestières. Les dynamiques temporelles de la structure et de la composition du paysage forestier dans notre région d’étude a montré que la déforestation était plus sensible dans la partie Sud de la zone d’étude, en dépit du climat favorable, alors que dans la partie Nord, proche des savanes Guinéennes, la simulation des dynamiques à partir de la chaine de Markov a montré une tendance à la reprise forestière.<p>En définitive, notre étude a mis en évidence que la zone de transition forêt-savane étudiée était fortement dynamique. Dans une région où aucune réserve forestière n’existe réellement et où le front forestier régresse ou se dégrade rapidement, notre approche permet de poser les bases d’une politique rationnelle de protection des forêts, en établissant des seuils structuraux minimaux des fragments nécessaires à la préservation du biotope originel.<p>/<p><p> / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Arable plant species diversity has been on a decline, with many species dependent on arable land becoming threatened. At the same time, attempts at defining the drivers of arable plant diversity have proven difficult and results are often contradictory. Much of the available data come from surveys that are small-scale and with great variability in methodology, leading to difficulties comparing them. In this study, I have used survey data from Gotland to examine how arable plant diversity is influenced by management, field size, soil texture and standing crop. I found a negative trend of diversity with increasing field size, and a suggested effect of management and soil texture on the presence of red listed arable plants. This study also evaluates the use of small datasets when examining plant diversity, and the limitations associated with it. It shows that while a small dataset cannot be analysed to the extent a more comprehensive one can, it is possible to identify trends and patterns with it, which may inform further studies.