I examined the effects of potential predators in relation to habitat selection in Peromyscus leucopus. I also examined habitat selection in three other sympatric species (Blarina brevicauda, Blarina carolinensis, Sorex longirostris). I utilized data fiom 49 sampling sites on National Park Service land; Petersburg National Battlefield Eastern Front Unit (15), Five-Forks Unit (17), Appomattox Court House National Historical Park (15) and Booker T. Washington National Monument (12). Sites were categorized by location (park unit) and habitat type (i.e. bottom-land hardwood), and the microhabitat within each sampling site was characterized by four variables (% cover of grasses, herbs, shrubs, and volume of downed wood). Importance values of tree species within each sampling site were also measured. Peromyscus leucopus, B. brevicauda, B. carolinensis, and S. longirostris were captured in all habitat types. Low capture rates for shrew species and high variability in the abundance of shrew species among all sampling sites were likely responsible for the lack of differences in abundance among habitats (p > 0.05). Peromyscus leucopus represented 76% of the captures among prey species and was the only species to demonstrate differences in relative abundance among habitat types. The relative abundance of P. leucopus was higher in bottom-land hardwood habitat when compared to pine forest plantation habitat (ANOVA, p P. leucopus among these habitat types may be explained by differences in understory structural diversity. Furthermore, the corresponding increase in the relative abundance of Procyon lotor (the most abundant predator during the study) in structurally heterogeneous habitat (bottom-land hardwood) suggests the importance of anti-predator behaviors within these habitat types. Ultimately, this may suggest that prey cannot escape the presence or calculate the abundance of predators and instead simply avoid dangerous habitats. Although the relative abundance of the most abundant predator (P. lotor) and prey (P. leucopus) species were positively associated within certain habitat types, a negative association between predator and prey species abundance was evident within parks. In the Eastern Front unit the relative abundance of prey (P. leucopus, S. longirostris) was lower in comparison to the Five-Forks unit while the abundance of P. lotor was higher (ANOVA, p P. lotor, Didelphis virginiana, and Urocyon cinereoargenteus were higher in the Eastern Front unit when compared to the Five-Forks unit. It appeared that the lethal effects of predators are evident at larger scales (within parks) despite the anti-predator behaviors of prey at smaller scales (within microhabitats). My results indicate that at larger scales (within parks) the lethal effects (removal of prey) of abundant predators may overwhelm the non-lethal effects (anti-predator behavior) exhibited by prey at smaller scales, especially in areas where structurally heterogenous habitats are lacking.

L’objectif de la thèse est d'évaluer l’apport des données satellites dans le suivi saisonnier de la végétation forestière (sous-bois et strate arborée). L'étude a été conduite sur la forêt landaise. Elle est basée sur une série de sept ans d'observations satellitaires décadaires d’un indice de végétation (PVI) et de mesures in situ de la surface foliaire (LAI) du sous-bois et des arbres. Tout d’abord, les observations in-situ ont été analysées. Elles montrent que le sous-bois est le déterminant majeur de la trajectoire saisonnière du LAI de l’ensemble du couvert végétal. Puis, ces informations ont été comparées aux données satellitaires. Il apparaît que la phénologie printanière du PVI renseigne sur celle du LAI du sous-bois. Enfin, ces résultats été exploités à l’échelle régionale et une carte régionale des types de landes a pu être produite. Cette étude ouvre des perspectives en matière d'intégration et de spatialisation des bilans d'eau et de carbone des écosystèmes forestiers à l'échelle régionale. / The aim of this thesis is to assess the potential of the remote sensing data to monitor the seasonal dynamic of the forest vegetation (understory and tree canopy). The study has been carried out on the maritime pine forest in the Southwest of France. It is based on a 7-year time-series of the 10-day vegetation index PVI composite derived from satellite and on in situ leaf area measurements (LAI) of understory and tree story.At first, the in situ observations have been analysed. It shows that the understory vegetation is the main driver of the seasonal dynamic of the whole forest LAI (understory+tree story). Then, these informations have been compared with the time-series of remote sensed PVI . It appears that the spring phenology of the PVI informs directly about the LAI understory one.Finally, these results have been used at the regional scale and a regional map of the lande types has been produced. This study opens some new prospects about integration and spatialisation of water and carbon balance of forest ecosystems at regional scale.

La fixation symbiotique d'azote par l'ajonc d'Europe (Ulex europaeus) représente une source importante d'azote dans la forêt cultivée de pins maritimes des 'Landes de Gascogne'. Cette thèse a pour objectif la création d'un modèle conceptuel de dynamique de population de l'ajonc dans la région en vue de la prédiction du flux d'azote associé. Pour cela plusieurs étapes du cycle de vie de l'espèce ont été étudiées: la production et la prédation des graines, puis le recrutement de nouveaux individus depuis le stock de graines du sol. Nos résultats suggèrent que le maintien de cette espèce héliophile à l'ombre de la canopée des pins est facilité par la diminution de l'allocation de ressources à la reproduction, lui permettant de maintenir sa croissance, et par la diminution de la prédation des graines. Par ailleurs, le recrutement de nouveaux ajoncs semble influencé par des facteurs écologiques identifiables (e.g. humidité du sol). Mais ces facteurs sont fortement variables dans l'espace et dans le temps, et aucun micro habitat n'apparait comme plus favorable à la régénération de l'espèce. Ces résultats sont intégrés à un modèle conceptuel, représentant les différentes étapes du cycle de vie de l'espèce, et l'impact des opérations sylvicoles sur ces étapes. Les connaissances issues de cette thèse pourraient aussi bénéficier à d'autres problématiques liées à l'espèce (e.g. c'est une espèce invasive dans de nombreuses régions du monde) et à la compréhension de l'écologie de la régénération des espèces ligneuses. En effet, l'allocation des ressources à la reproduction pourrait être plastique et permettre une réponse adaptative à un environnement changeant; et la variabilité spatiotemporelle de la régénération des ligneux pourrait reposer sur l'existence de niches écologiques de régénération définies dans l'espace écologique. / Symbiotic nitrogen fixation by European gorse (Ulex europaeus) is a major source of nitrogen in the 'Landes de Gascogne' cultivated forest of maritime pine. This thesis aims to build a conceptual model of the population dynamic of gorse in the region, with a view to predict the associated flux of nitrogen. To achieve this, several steps of the life cycle of the species were studied: production and predation of seeds, and the recruitment of new plants from the seedbank.The results suggest that the maintenance of this light demanding species in the shade of the canopy of pines is improved by the decrease of reproductive allocation, which enable to maintain its growth, and by the decrease of the predation of seeds. The recruitment of new gorse plants seems controlled by identifiable ecological factors (e.g. soil moisture), however these factors are highly variable in space and time, and no specific micro-habitat appears to be more favourable for the species regeneration.These results are integrated into a conceptual model based on the different steps of the life cycle of the species, and taking into consideration the influence of forestry practices on these steps. Furthermore, the production of knowledge could benefit other subjects related to the species (e.g gorse is a noxious weed in many region in the world) and the understanding of the ecology of woody plants' regeneration. Allocation of resources to reproduction may be plastic and enable an adaptative response to a changing environment; and spatiotemporal variability of the regeneration of woody plants may rely on the existence of ecological regeneration niches defined in the ecological space.

Submitted by Silvana Teresinha Dornelles Studzinski (sstudzinski) on 2015-06-23T15:19:36Z No. of bitstreams: 1 TiagoClossDeMarchi.pdf: 3447572 bytes, checksum: 384491c29d57ca52c59ea0cda6879c8b (MD5) / Made available in DSpace on 2015-06-23T15:19:36Z (GMT). No. of bitstreams: 1 TiagoClossDeMarchi.pdf: 3447572 bytes, checksum: 384491c29d57ca52c59ea0cda6879c8b (MD5) Previous issue date: 2011 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A mudança do uso da terra decorrente de atividades agrícolas provoca uma modificação na paisagem que leva à criação de fragmentos florestais isolados que se mantém imersos em uma matriz que pode apresentar uma maior ou menor agressividade de acordo com o seu uso. Este estudo foi realizado em duas fazendas vizinhas localizadas no município de Eldorado do Sul, RS. A Fazenda Terra Dura, pertence à empresa Celulose Riograndense S/A e a maior parte da área é utilizada para a monocultura de eucalipto (Eucalyptus spp.). Os remanescentes de floresta nativa estão exclusivamente associados aos diversos cursos d’água que cruzam a área e cercados pelo plantio de eucalipto de diversas idades e estágios de produção. A área é utilizada para o plantio de eucalipto há cerca de 30 anos e há 20 foi isolada do gado. A Fazenda Eldorado destina-se à criação extensiva de gado e sua cobertura vegetal é caracterizada por um predomínio de campo com fragmentos de florestas ripárias que o gado utiliza como local de pastejo e desedentação. Em cada uma das dez áreas selecionadas foram alocados dois transectos paralelos ao curso d’água a 20 metros de distância um do outro nos quais foram aleatorizadas cinco unidades amostrais de 10 x 10m para amostragem do componente arbóreo dos fragmentos. Em cada unidade amostral foram registradas a circunferência de todos os indivíduos com diâmetro a altura do peito maior ou igual a 5 cm (DAP ≥ 5cm). O componente juvenil foi amostrado em unidades amostrais de 5 x 5m concêntricas em cada parcela de 10 x 10m, onde foram amostrados todos os indivíduos com mais de um metro de altura e com menos de 5 cm de diâmetro e estimou-se sua altura total e seu diâmetro à altura do solo (DAS). A densidade e composição do estrato herbáceo foi amostrada em parcelas de 1 x 1 m concêntricas às unidades amostrais de 5 x 5 m. Nestas unidades amostrais foi removida toda vegetação de até 1 m de altura e identificadas taxonômicamente as espécies e separadas em formas de vida (árvore, arbusto, erva, gramíneas, pteridófita, trepadeiras, epífitos). Para avaliação do sub-bosque nos plantios de eucalipto foram selecionados quatro talhões onde foram alocados três transectos de 100 m de comprimento em diferentes distâncias da borda (5, 25 e 50 m) e dois transectos (5 e 25 m) para o interior da mata ciliar. Em cada transecto foram sorteadas cinco unidades amostrais de 5 x 5 m e amostrados todos os indivíduos juvenis utilizando os mesmos critérios anteriormente citados para este estrato. Nos fragmentos adjacentes aos plantios de eucalipto, foram encontradas 61 espécies para os adultos e 77 para os juvenis e o estoque de carbono estimado foi de 106 Mg.ha-1 para os indivíduos adultos e de 4,3 Mg.ha-1 para os herbáceos. Nas áreas com presença de gado foram amostradas 62 espécies para os adultos e 48 para juvenis, com um estoque de carbono de 85,5 Mg.ha-1 para adultos e 0,9 Mg.ha-1 para herbáceo. No sub-bosque dos plantios de eucalipto foram amostradas 32 espécies, sendo 16 exclusivas e 71 no interior da floresta ripária, com 55 exclusivas. Os resultados mostraram que florestas em pequenos fragmentos incorporados em plantações de eucalipto parecem ser melhor preservadas do que aqueles expostos à pecuária. Além disso, áreas com presença de gado apresentaram uma redução no estoque de carbono de 23,8% para o estrato arbóreo e de 79,4% no estrato herbáceo em relação às áreas sem a presença de gado. A plantação de eucalipto possui um importante papel, embora restrito devido ao curto período de corte das árvores, para a manutenção da diversidade de espécies de florestas nativas adjacentes em seu sub-bosque e podem atuar como uma catalizadoras da regeneração da vegetação nativa e na manutenção da diversidade local. / The change in land use due to agricultural activities causes a landscape change that leads to the creation of isolated forest fragments that remain embedded in a matrix that may present a greater or lesser aggressiveness according to their use. The environmental quality of this matrix can affect species composition and forest structure through several factors that impact the surrounding environment, but on the other hand, depending on its type, the array can act as an important source of biodiversity conservation. This study was conducted in two neighboring farms located in Eldorado do Sul, RS. Terra Dura Farm, owned by Celulose Riograndense S/A and most of the area is used for the monoculture of eucalyptus (Eucalyptus spp.). The remnants of native forest are exclusively associated with the various streams that cross the area and surrounded by eucalyptus plantations of various ages and stages of production. The area is used for the planting of eucalyptus during 30 years. The cattle was isolated 20 years ago. Eldorado Farm is intended for extensive cattle ranching and its vegetation is characterized by a predominance of field with fragments of riparian forests that livestock use for grazing. We survey ten riparian fragments, five in each farm, were allocated two transects parallel to the stream to 20 m away from each other in which five were randomized plots of 10 x 10 m sampling of the tree component of the fragments. In each sampling unit circumference were recorded for all individuals with diameter at breast height greater than or equal to 5 cm (DBH ≥ 5 cm). The juvenile component was sampled in 5 x 5 m plots concentric in each plot of 10 x 10 m was sampled all individuals with more than one meter in height and less than 5 cm in diameter and estimated its total height, and its diameter at ground level (DAS). The density and composition of the herbaceous layer was sampled in plots of 1 x 1 m plots of concentric to 5 x 5 m. In these sample units of all vegetation was removed up to 1 m high, which were taxonomically identified and separated in life forms (tree, shrub, herb, grass, fern, lianes and epiphytes). To evaluate the understory in the eucalyptus plantations were selected four plots were allocated three transects of 100 m length at different distances from the edge (5, 25 and 50 m) and two transects (5 and 25 m) into the riparian vegetation. In each transect were randomly selected five samples of 5 x 5 m and sampled all juveniles using the same criteria previously cited for this stratum. In fragments adjacent to eucalyptus plantations, 61 species were found for adults and 77 for juveniles and the estimated carbon storage was 106 Mg.ha-1 for adults and 4.3 Mg.ha-1 for the herbs. In areas with presence of cattle were sampled for 62 adults and 48 for juveniles, with a carbon stock of 85.5 Mg.ha-1 for adults and 0.9 Mg.ha-1 for herbaceous. In the understory of the eucalyptus plantations were found 32 species, with 16 exclusive and 71 within the riparian forest, with 55 exclusive. Our results showed that in small forest fragments embedded in eucalypt plantations seem to be better preserved than those exposed to livestock. In addition, areas with the presence of cattle showed a reduction in carbon stock of 23.8% for the upper stratum and 79.4% in the herbaceous layer compared to areas without the presence of livestock and the planting of eucalyptus has an important role, although limited, due to shortcut the trees for the maintenance of species diversity of native forest adjacent to their understory and can act as a catalyst of the regeneration of native vegetation and maintenance of local diversity.

Graduation date: 2006 / Best scan available. Ink on original is smeared.

Old-growth stands are important for management, conservation, wildlife, recreation, and maintaining biological diversity in forested landscapes. However, we are lacking the information needed to adequately identify and characterize old-growth stands. This is especially true for high elevation, interior forests. The characterization of stand structure and regeneration pattern will help in the development of site-specific guidelines for identifying old growth stands and restoring some of the old-growth characteristics in managed stands. This pamphlet presents a synopsis of a study investigating stand structure and regeneration of old-growth stands in the Moist Cold Engelmann Spruce - Subalpine Fir (ESSFmc) Subzone near Smithers, B.C. The three stands selected for the study were located on zonal sites, each in different watersheds, and the stands were established after fire. The criteria used for selection were: i) absence of lodgepole pine, ii) presence of advanced regeneration, and iii) abundant snags and coarse woody debris. These stands were presumed to represent the old-growth stage of stand development or the final (climax) stage of secondary succession.

This research examines the relationship between understory plant diversity and logs in a Pacific Northwest (PNW) Sitka spruce (Picea sitchensis)-western hemlock (Tsuga heterophylla) old-growth, coastal forest. These forests are renowned for their high forest productivity, frequent wind storms, and slow log decomposition rates that produce unmatched accumulations of coarse woody debris (CWD) yet few studies have examined the relationship between CWD and understory vegetation ecology. My research addressed this topic by comparing understory plant census data between paired fallen log and forest floor sites (n=20 pairs). My objectives were to: 1) determine the influence of substrate type on community composition and diversity, and 2) examine successional pathways and species assemblage patterns on CWD in various stages of decomposition. To meet these objectives I employed non-metric multidimensional scaling (NMDS) ordinations and unsupervised cluster analyses to identify and compare community assemblages on both substrates. These methods revealed similar species diversity and evenness between log and forest floor sites with compositional differences within and between substrates corresponding to habitat availability for colonization and light and moisture gradients. My results also suggest understory successional pathways related to decay class and characterized by an initial abundance of bryophytes, forbs, and seedlings followed by woody shrubs. Understory communities developing on logs also experienced increasing diversity, evenness, and divergence from forest floor communities consistent with log decomposition. These results differ from findings for boreal forests that reveal increasing similarity between substrate communities with increasing decay class. Recommendations for future research include the employment of a more robust sample size and direct measurements of environmental variables. Additional comparator studies are also needed to confirm the effects of forest type and decomposition on the relationship between CWD and forest understory communities. This study demonstrates how fine-scale wind disturbance fosters biodiversity through the creation of CWD substrate. My results and future research are essential for the development of silvicultural models designed to promote biodiversity in PNW coastal forests.

Human activities are increasing the occurrence of megafires that have the potential to alter the ecology of forest ecosystems. The objective of this study was to understand the impact of a 610 km2 megafire on patterns of forest regeneration and herbivory of three forest types (aspen/fir, oak/maple, and pinyon/juniper) within the burn scar. Sapling density, meristem removal, and height were measured across a transect network spanning the area of the burn scar over three years from 2019-2021. The network consisted of 17 burned/unburned transect pairs in adjacent burned/unburned forest stands (6 aspen/fir, 5 oak/maple, and 6 pinyon/juniper). Species that regenerated through sprouting generally responded positively to fire while regeneration from seed showed very little post-fire response. Browse pressure was concentrated on deciduous tree species and tended to be greater in burned areas but the effect diminished over time. Meristem removal of sprouting species was below the critical threshold resulting in positive vertical growth across years. Our results indicate that forest regeneration within the megafire scar was generally positive and experienced sustainable levels of ungulate browsing that are likely to result in forest recruitment success. Novel fire regimes are becoming increasingly common and megafires have burned across ecotonal boundaries across multiple forest types. Plant community structure and composition may be critically affected by changing fire regimes. Our objective was to investigate how a megafire that burned across multiple forest types impacted understory plant community assembly and biodiversity. Paired vegetation transects were installed in burned and unburned areas across aspen/fir, oak/maple, and pinyon/juniper forests within the 2018 Pole Creek Megafire burn scar. Percent cover of understory plants was measured in the summer of 2022 and plants were identified to the species level. Richness and diversity indices were then calculated and analyzed using mixed effects models. Fire decreased species richness of the aspen/fir forest understory and increased plant cover in pinyon/juniper forests, while not significantly impacting oak/maple understories. The significant effects of fire were largely driven by changes in forb species. Fire decreased the richness of native plants in aspen/fir forests but increased the richness of non-native plants in oak/maple and pinyon/juniper forests. Non-native plant abundance also increased in post-fire pinyon/juniper forests. Our results suggest that forest understory communities show variable responses to megafires that burn across multiple forest types with important implications for post-fire plant community structure, diversity, and invasibility. Large mammal herbivores (ungulates) are increasing in number and spreading into novel habitats throughout the world. Their impact on forest understory plant communities is strong and varies by herbivore, plant growth form, and season. The objective of this study was to determine the individual and collective herbivory impacts of native versus domestic ungulates on the understory plant community composition of post-fire aspen forests. Four-way fencing treatments were installed in 2012 to separate ungulate species, and Daubenmire frames were used to collect percent cover estimates for each understory plant species. Vegetation data were later used to calculate richness and diversity indices. Total understory plant cover, richness, and diversity were not significantly impacted by the herbivory fencing treatment. However, woody plant species' percent cover was 90% greater in full ungulate exclusion plots than in the fenceless controls. Herbivores likely targeted woody plant species due to their high nutrient levels that last longer into the winter than those of forb or graminoid species. Herbivory treatment did not affect non-native species. Our results indicate that herbivore fencing can protect forest understory plant communities, particularly the woody species. Successful regeneration of woody species can benefit the diversity of the entire understory plant community and preserve forest structure.

Mid-rotation fertilization and vegetation control are some of the most common silvicultural treatments in loblolly pine (Pinus taeda L.) plantations in the southeastern United States. Competing vegetation is commonly thought to sequester fertilizer nitrogen (N) and reduce the potential growth response to a mid-rotation fertilization treatment. This experiment aims to identify what proportion of applied N fertilizer is retained in the crop tree pine foliage, and the degree to which understory vegetation is competing for this resource. Our mid-rotation loblolly pine plantation received an application of 15N fertilization (urea 365 kg/ha, at 46% N by weight, i.e. 168 kg/ha of N) and a portion of plots received an understory vegetation control (basal spray application of triclopyr; 13.6% active ingredient) treatment either before fertilization or not at all. One-year post-fertilization, 15N contents within pine foliage, leaf fall/leaf litter, forest floor, and soil were measured, as was competing vegetation presence. There was significant variation in applied nitrogen acquisition among the different ecosystem components measured, with 0-15 cm soils retaining a majority at 32-37% added 15N. Differences in fertilizer N acquisition in pine foliage between plots with and without understory vegetation control was marginally significant (p = 0.06) with pine foliage in plots without understory vegetation capturing greater 15N (4.3% greater). Red maple (Acer rubrum) and oak species (Quercus spp.) were the most common competitors but neither had a uniquely pronounced effect on pine nitrogen sequestration. My data indicate that increasing competition reduces fertilizer N foliar concentrations in crop pine trees but at a modest rate and equally across species groups. An unrefined threshold determining when fertilizer N capture in crop pine trees was affected was found at 3.1 m2/ha of competing vegetation basal area. This site will continue to be monitored over time to assess fertilizer N retention in loblolly pine each year after fertilization and evaluate the fertilizer N capture within competing vegetation. / Master of Science / Some of the most prevalent management practices for mid-rotation (age 15, i.e., roughly halfway through a crop cycle) loblolly pine (Pinus taeda L.) plantations in the southeastern United States are fertilization and vegetation control. Nitrogen (N) is consistently one of the most limiting factors to productivity. The addition of N via fertilization is therefore a common forestry practice. However, when a stand is fertilized, the added resource is partitioned and cycled throughout the ecosystem. It is presumed that the amount of fertilizer N obtained by crop trees in a plantation is dependent on the level of competing vegetation (i.e., weed-trees and shrubs) present on site. Controlling competing vegetation prior to fertilization may therefore be warranted under certain conditions. To date, the amount of competing vegetation where it begins to impact fertilizer uptake by the crop tree is unknown. This study aims to elucidate this competing vegetation threshold to better inform mid-rotation management of loblolly pine plantations. This study examined applied fertilizer N capture in ecosystem components with varying levels of understory vegetation, and found more fertilizer N in pine foliage when understory vegetation was completely removed prior to fertilization. No single understory hardwood weed species had a uniquely strong influence on crop tree productivity uptake. Plots that ranked in the upper third in competing vegetation presence did have significantly less foliar fertilizer N in the pine crop trees. Additional replication of this study would be necessary to determine a universal threshold of competing vegetation which would trigger the removal of competing vegetation prior to fertilization.

Thesis (MSc(For))--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: Recognizing the biological significance of gaps, the South African Department of Water Affairs and Forestry (DWAF) in 1989 initiated a Gap Dynamics Project in the indigenous forests of Tsitsikamma (Eastern Cape, South Africa). This consists of three sub-projects: Koomansbos (9300 m2), created by a ground fire in 1989; Plaatbos (1600 m2), made by a Podocarpus falcatus (Thunb.) R. Br. ex Mirb. (Podocarpaceae) windfall in 1994; and nine gaps of different sizes, artificially created by selective tree felling in 1995: three small (100-150 m2), three medium (300-500 m2) and three large (800-1000 m2). All the gaps were surveyed after creation and permanent plots were established for subsequent monitoring. The current timber harvesting system practiced in South African indigenous forests attempts to minimize gap size. It has been proposed by Euston-Brown et al. (1996) that this practice is likely to benefit the more shade tolerant species, but may inhibit the regeneration of less shade tolerant plants in the forest. Therefore, the present study aimed to verify two hypotheses: gaps may close in a process that is determined by their size, their origin and the plant species characteristics; soil quality might change inside those gaps. For the purpose of the study, the gaps cited above were re-surveyed between 2002 and 2003. It was found that: 1) there was little clear difference in the community structure of plant species between gaps of different sizes and origins; as expected from the species-area relationship, large gaps had higher species richness, plant diversity and herbaceous percentage cover than medium and small gaps; diversity indices were higher in the large windfall gap than in the large fire and artificial gaps; generally, context and stochastic events were largely more important in determining gap diversity and regeneration than gap sizes and origins; 2) diversity indices in the gaps were higher than recorded previously; 3) soil pH and Electrical Conductivity were respectively lower and higher inside the gaps than adjacent to them; these variations were statistically significant. Present data on the vegetation in the gaps were compared to past measurements, and future vegetation structure has been predicted, as a function of current gap vegetation. Recommendations have been made for sustainable management of the indigenous forest of Tsitsikamma. / AFRIKAANSE OPSOMMING: Voortspruitend uit die erkenning van die biologiese belang van gapings, het die Suid-Afrikaanse Departement van Waterwese en Bosbou (DWB) in 1989 'n projek oor gapingsdinamika in die inheemse woude van Tsitsikamma (Oos-Kaap, Suid-Afrika) geïnisieer. Dit bestaan uit drie subprojekte: die gaping in Koomansbos (9300 m2) wat in 1989 deur 'n grondvuur geskep is; die gaping in Plaatbos (1600 m2) wat veroorsaak is toe bome van die spesie Podocarpus falcatus (Thunb.) R. Br. ex Mirb. (Podocarpaceae) in 1994 omgewaai is; en nege gapings van verskillende groottes wat in 1995 kunsmatig deur geselekteerde boomkappery geskep is: drie is klein (100-150 m2), drie mediumgrootte (300-500 m2) en drie groot (800-1000 m2). Alle gapings is ná hulle ontstaan opgemeet en ondersoek en permanente terreine is vir daaropvolgende monitering gevestig. Die stelsel wat tans vir die oes van hout in Suid-Afrikaanse inheemse woude gebruik word, poog om die grootte van gapings te minimaliseer. Euston Brown et al. (1996) doen aan die hand dat hierdie praktyk spesies wat meer skaduweeverdraagsaam is waarskynlik sal bevoordeel, maar die regenerasie van plante in die woud wat minder skaduweeverdraagsaam is, kan inhibeer. Hierdie studie het dus ten doel gehad om twee hipoteses te verifieer: Gapings kan toegroei in 'n proses wat deur hul grootte, oorsprong en die eienskappe van die plantspesies bepaal word; en die gehalte van die grond binne daardie gapings kan verander. Die gapings waarna hierbo verwys is, is vir die doel van hierdie studie tussen 2002 en 2003 weer gemonitor. Daar is bevind dat: 1) daar min duidelike verskille was tussen die gemeenskapstruktuur van plantspesies tussen gapings van verskillende groottes en oorsprong; soos van die verhouding tussen spesies en area verwag kan word, het groter gapings 'n hoër spesierykheid, plantdiversiteit en persentasie niehoutagtige dekking as medium- en klein gapings gehad; diversiteitsindekse was hoër in die groot Plaatbosgaping as in die groot Koomansbosgaping of die kunsmatige gapings; in die algemeen was konteks en stochastiese gebeure grootliks belangriker in die bepaling van gapingsdiversiteit en -regenerasie as gapingsgrootte of -oorsprong; 2) diversiteitsindekse in die gapings was hoër as wat voorheen aangeteken is; en 3) grond-pH en elektriese geleidingsvermoë was onderskeidelik laer en hoër binne die gapings as neffens hulle; hierdie variasies was statisties beduidend. Huidige data oor die plantegroei in die gapings is met vorige metings vergelyk, en 'n toekomstige plantegroeistruktuur is as 'n funksie van huidige gapingsplantegroei voorspel. Aanbevelings is gemaak rakende die volhoubare bestuur van Tsitsikamma se inheemse woud.