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Magistro darbe nustatyta pušynų atvejinių kirtimų įtaka pomiškio formavimuisi Švenčionėlių miškų urėdijoje. Darbo objektas: Pomiškis atsikuriantis po atvejinių kirtimų Švenčionėlių miškų urėdijos pušynuose. Darbo tikslas: Nustatyti pušynų atvejinių kirtimų įtaką pomiškio formavimuisi. Darbo metodai: Nustatant pomiškio kiekį, išsilaikymą, kirtaviečių žolinės dangos poveikį pomiškiui, tyrimai atlikti septyniolikoje skirtingų metų supaprastintų atvejinių kirtimų (B. Labanausko) kirtavietėse, kur visos augavietės buvo Nbl (normalaus drėgnumo nederlingi dirvožemiai). Tyrimai vykdyti 2010 metais Švenčionėlių miškų urėdijos, Januliškio, Labanoro, Lakajų, Pasiaurės, Prūdiškės girininkijų miškuose. Patvirtinta metodika atlikti lauko tyrimai. Kiekviename sklype buvo parinktos 2 x 20 m juostos (40 m2), tolygiai išdėstytos sklype (vienodais atstumais sklypo įstrižainių kryptimis). Apskaitos juostoje aprašytas ir įvertintas pomiškis bei žolinė danga. Pomiškio medelių rūšys buvo registruojamos nurodant jų skaičių vienetais, o žolinės dangos rūšys – nurodant projekcinį padengimą procentais. Gauti duomenys užrašyti į iš anksto paruoštus duomenų rinkimo lapus. Darbo rezultatai: Tirtuose sklypuose, pušies savaiminukai gerai atžėlė 53 % visų sklypų. Patenkinamai atžėlė 35 % tirtų sklypų. 12 % tirtų sklypų neatitinka nuostatų, nes pušies savaiminukų skaičius hektare yra nepakankamas reikiamam pušies atžėlimui. Atvejinėse kirtavietėse nepageidaujamos medžių rūšys turi įtakos projektuojamų medžių... [toliau žr. visą tekstą] / In this master thesis was determined pine forest shelter wood cutting influence to understory formation in Švenčionėlių State forest Enterprice. The object of work: Understory, regenerating after shelter wood cutting in Švenčionėlių State forest Enterprice. The aim of work: To determine shelter wood cutting influence to understroy formation in pine forest. Methodology: By evaluating quantity of understory, survival, herbal plants influence to forest understory in cutting areas, the reasearch was performed in seventeen simplified shelter wood cutting areas with different cutting age, (B. Labanausko) where all sites were Nbl (regular moisture not fertile soils). The research was performed in 2010 year, in Švenčionėlių State forest enterprise, Januliškio, Labanoro, Lakajų, Pasiaurės, Prūdiškės forest districts. According to methodology, outdoor investigations were made. In each sample plot were chosen 2 x 20 m stripes (40 m2), gradualy located in a plot (by equal distances to plot diagonal directions). In sample plots understory and herbal cover were evaluated and described. Understory tree species were registered apiece, and herbal cover species were registered by indentifying projective cover of land in percentage. Data were recorded to prepared blanks. Results: Pine seedlings regenerated well in 53 % sample plots. Sufficiant regeneration (35 %) was found in 3 plots. 12 % of investigated plots had inadequate conditions, because amount of pine seedlings in one hektare... [to full text]

This thesis examines factors limiting understory herb presence and flowering in young second-growth Douglas-fir (Pseudotsuga menziesii) forests on the west side of the Cascade Mountains, Oregon, USA. I studied the belowground effects of canopy trees on understory herbs and shrubs in old-growth forests using trenched plots from which tree roots were excluded. Effects of tree density and stand age were tested by comparing the understory community composition of old-growth stands and pre-commercially thinned and unthinned young second-growth stands. I also examined the effect of conifer basal area on understory herb presence and flowering within one young second-growth watershed. In young stands, I focused on three groups of understory herb species: disturbance-responsive (release), forest generalist and old-growth associated. The effects of root trenching on vegetation and soil moisture were tested in closed-canopy and gap locations in two old-growth Douglas-fir (Pseudotsuga menziesii) forests. Ten years after installation, trenched plots averaged 92% total understory cover while untrenched plots averaged 47% cover. Trenched plots under closed canopies were moister than control plots throughout the growing season; the trenching effect on soil moisture became apparent in the generally wetter gaps only at the end of the growing season. Vegetation responses to trenching were concomitantly larger under closed canopies than in gaps. Stands that had been pre-commercially thinned 20 years earlier exhibited understory composition more similar to old growth than did unthinned stands. Thinned stands exhibited higher frequencies, abundances and density of flowering of old-growth associated herbs than did unthinned stands, but lower than did old-growth stands. Forest generalist and release species showed mixed responses to thinning. I used both general linear models and classification and regression tree models to explore the association of herb species presence and flowering with conifer basal area and abiotic variables. Both modeling approaches yielded similar biological insights. Flowering was more sensitive than presence to current stand basal area. Flowering of old-growth associated and release species was negatively correlated with conifer basal area. Linear models allowed clearer hypothesis tests, while tree-based models had greater explanatory power and provided information about interactions between variables. / Graduation date: 2004

Graduation date: 2006 / Canopy gap formation is a major factor contributing to maintenance of overstory species diversity and stand structure in forests and may be integral to development of understory shrub and herb layers as well. Acknowledgement of gap formation as a fundamental feature of natural forests has led to consideration of gaps as an option in forest management regimes. This study examined understory vegetation communities across canopy gaps created as a part of the Density Management Study (DMS), which investigates the effectiveness of a thinning regime in promoting late-successional habitat development in young Douglas-fir forests of western Oregon. Patterns in understory vegetation community composition in and around 0.1 and 0.4ha gaps created as a part of the DMS treatment were investigated. The primary goal of this research was to investigate the potential role of canopy gap creation in fostering heterogeneity in understory vegetation communities, and to examine the extent of gap influence on the surrounding thinned forest matrix. Tree species distributions have been shown to partition across gaps in tropical forest systems through differential responses of species to gradients in resource availability, a pattern known as gap partitioning. In temperate forests, understory vegetation communities are much more diverse than the overstories, and display a greater array of habitat requirements. Therefore, understory communities may be more likely than overstories to exhibit gap partitioning in these forests. Patterns in understory community composition across gaps suggest that gap partitioning has occurred. The strength of this partitioning effect appears to differ between gap sizes, as smaller gaps showed a less powerful effect. Abundance of ruderal species was strongly related to gap partitioning in larger gaps, while smaller gaps were dominated by competitor species. Partitioning may be related to an interactive relationship between harvest-related ground disturbance and resource gradients. Therefore, considerations of gap partitioning processes should take into account intensity and spatial distribution of ground disturbance in relation to resource gradients. In addition, conditions necessary for the expression of gap partitioning in understory vegetation communities may be rare in natural gaps in this region. The influence of gaps on understory vegetation communities in the surrounding forest appears to be relatively small. This small influence extent may help explain the lack of a stand level response to gap formation in these stands. Larger gaps exhibit a slight influence on the understory plant community in the surrounding forest to the north of the gap. In small gaps, there seemed to be an influence of the surrounding forest on gap interiors, resulting in an area of influence smaller than the physical gap area. This relationship may indicate that the area of gap influence on understory vegetation may not scale linearly with physical gap size. Species diversity was higher in gap interiors than in surrounding thinned forests. However this effect was partially due to the presence of exotic species, which showed an affinity for gap interiors. Late successional associated species were negatively related to gap interiors, but only in the larger gap size. Gap creation appears to be promoting small scale species diversity in these stands, but creation of large gaps may also promote the establishment of exotic species and may have a negative effect on late successional associated species. However, any and all of these effects may be transient, as understory communities will be strongly affected by overstory re-establishment, and related changes in resource availability. In general, gap formation may influence small-scale stand heterogeneity as evidenced by understory plant communities, but this effect may rely strongly on the nature of gap formation and intensity of disturbance related to this formation.

Thesis (M. En.)--Miami University, Institute of Environmental Sciences, 2008. / Title from first page of PDF document. Includes bibliographical references (p. 16-21-Xx).

A three dimensional sampling technique was used to compare field understory conditions in Southeastern Louisiana using a laser range finder at three height levels (0.5m, 1.0m, and 1.5m) to LiDAR generated understory conditions to determine if a relationship existed. A similar comparison was made between densitometer crown closure measurements and understory LiDAR vegetation counts. A comparison between overstory LiDAR counts and understory LiDAR counts was also performed. LiDAR and understory counts exhibited a significant linear relationship but were poorly correlated at each sample level (Level-1 R2 = 0.34 ? 0.38, Level-2 R2 = 0.36 ? 0.43). The Level-3 LiDAR slope coefficient was non-significant. The crown closure versus understory linear model did not produce any significant results. The overstory LiDAR versus understory LiDAR model produced a moderate correlation (R2 = 0.5226) and was significant. The process of relating LiDAR points to understory conditions was not repeatable, even in the same geographic region.

Wild leek (Allium tricoccum) is a spring ephemeral of northeastern North America. In the Canadian province of Quebec, it is listed as threatened due to human harvesting, and in Gatineau Park its presence is used as an indicator of human impact. Wild leek grows in patches on the forest floor, and before the tree canopy develops its green leaves are clearly visible through the bare branches of deciduous forests, allowing it to be observed with optical remote sensing. This study developed and tested a new method for monitoring wild leek across large geographic areas by integrating field observations, UAV video, and satellite imagery. Three-cm resolution orthomosaics were generated for five <0.1 km2 sites from the UAV video using Structure-from-Motion, segmented, and classified into wild leek (WL) or other (OT) surface types using a simple greenness threshold. The resulting maps, validated using the field observations, had a high overall accuracy (F1-scores between 0.64 to 0.94). These maps were then used to calibrate a linear model predicting the per-pixel percentage cover of wild leek (%WL) from NDVI in the satellite imagery. The linear model calibrated for a Sentinel-2 image from 2018, covering all of Gatineau Park (~361 km2), allowed %WL to be predicted with an RMSE of 10.32. A similar model calibrated for a WorldView-2 image from 2018 was noisy (RMSE = 37.64), though much improved by resampling this image to match the spatial resolution of Sentinel-2, due to MAUP scale effect (RMSE = 13.06). Testing the potential for satellite-based monitoring of wild leek, the %WL prediction errors were similar when a new linear model was developed using the Sentinel-2 image from 2017 (RMSE = 12.84) and when the model calibrated with the 2018 Sentinel-2 image was applied to the 2017 satellite data (RMSE = 16.97). The linear models developed for the Sentinel-2 and WorldView-2 images from 2018 were used to map wild leek cover for Gatineau Park. Both images allowed production of similar wild leek maps that, based on field experience and visual inspection of the imagery, provide good descriptions of the actual distribution of wild leek at Gatineau Park.

The West has lost up to 60% of its historic aspen stands over the last century, probably as a result of the successional tendency of aspen to be replaced by coniferous species in the absence of periodic fires. One of several major impacts of this change is the loss of understory forage as conifer canopy cover increases. I measured understory biomass in aspen stands ranging from 0% to 81 % absolute conifer cover in the canopy Ill and found that understory production declines exponentially as conifers replace aspen. I also did an economic analysis to determine the value of the forage that is not being produced by aspen sites due to a presence of coniferous species within the tree canopy. Study results indicate significant losses in forage, marketable through the sale of livestock, and losses in revenue generated through grazing fees for the USDA Forest Service.

Effects of climatic factors on the plant distribution were examined by means of direct gradient analysis, and the relationship of forest flora, life form and phytogeographical distribution was examined. Subsequently, leaf phenology of forest plants were analyzed to evaluate the adaptive significance in relation to the environments in forest understory. In the boreo-nemoral forest ecotone, Hokkaido Island, northern Japan, co-ccurrence of northern and southern plants in a certain forest site is more notable in the understory than in the crown, and this dates back to the late-uaternary period, where the decrease in temperature associated with the glacial period forced the understory flora to adapt their life form or leaf habits to snowcover and light conditions of the interior forests. / Hokkaido University (北海道大学) / 博士 / 環境科学

Since the late 1880's western juniper has expanded in range and increased in density in sagebrush-bunchgrass, riparian, and forested plant communities of the Pacific Northwest. Succession to western juniper woodland has been shown to reduce the productivity and diversity of the understory component, result in concentration of soil nutrients beneath juniper canopies, and reduces soil moisture storage. This study assessed understory plant succession, soil nitrogen (N) cycling, litter decomposition, and soil moisture availability following cutting of a western juniper woodland on Steens Mountain, Oregon. Cutting of western juniper reduced below-ground competition for water and N, increasing soil moisture storage and N availability for understory species. Leaf water potentials were less negative, and N concentration and biomass in understory plants were greater in the cut treatment. Understory species responded to improved growth conditions with increased cover, biomass, density, and diversity. In 1993, total understory biomass and canopy cover were 870% and 300% greater, respectively, in the cut treatment than the uncut woodland. Understory succession was dominated by plants present on the site prior to cutting. Results indicated initial that bunchgrass densities of 2 plants/m2 were sufficient for perennial grasses to dominate following juniper cutting. Juniper cutting is an effective method for restoring the understory component in sagebrush rangelands that are currently dominated by western juniper woodland. Nitrogen availability was greatest in cut-interspace locations the first year following treatment and in cut-duff locations in the second year. Nitrification was lowest in cut-slash and woodland-duff locations, areas receiving fresh litter inputs and experiencing lower temperatures than interspace (cut and woodland treatments) and cut-duff locations. Decomposition of juniper litter was two times faster in the cut treatment, however the release of litter N occurred earlier in the woodland. Large inputs of N poor litter from cut juniper slash were hypothesized to have increased microbial demand for N, resulting in immobilization of litter N. Immobilization of litter N may be important in conserving N on sites following cutting. / Graduation date: 1997