Survival and growth of two oak species, live oak (Quercus virginiana) and Nuttall oak (Quercus texana), and three planting stocks: 1-0 bareroot, conventional containerized, and Root Production Method (RPM™) seedlings were compared. Conventional containerized live oak and bareroot Nuttall oak seedlings exhibited greatest survival. RPM™ seedlings exhibited the lowest survival in both species. Conventional containerized seedlings exhibited greater groundline diameter (GLD) growth and twice as much height growth as bareroot seedlings during the first year. During the second year, conventional containerized seedlings exhibited greater GLD growth than bareroot seedlings in live oak, but in Nuttall oak, bareroot seedlings exhibited greater GLD growth. RPM™ seedlings exhibited similar GLD growth compared to bareroot seedlings during both years but the least height growth of all planting stocks, regardless of species. Height growth of bareroot and conventional containerized seedlings was similar after two years.

No description available.

No description available.

No description available.

No description available.

No description available.

Problem: How to mechanise tree planting in North American logged sites? Trees are presently hand planted. Preliminary exploration identified the following collection of sub-problems. Vehicle: How to carry tools reliably and cost effectively over rough obstacle strewn ground? Results: U.S.A. - patent granted European Patent Office - patent granted Canada - patent granted The patents cover the main form and mode of operation of a simple but unconventional vehicle. Silvicultural/mechanical: How to mechanise the handling and placement of trees? Results: Two International Patents allowed. They cover a magazine/feed mechanism and a placement mechanism. They form a planting tool. One man guides the vehicle/tool system. An array of planting tools is carried. Two problems arise from the need to make guidance manageable and the planting rate fast enough. Spacing: How to cause the members of a collection of simultaneously operating tools to space themselves appropriately the spacing being driven by machine perceived cues? Choice: How to cause a tool to move to and halt over a plan table spot, tool action being driven by machine perceived cues? Results: One International Patent allowed. Spacing: A conceptual solution is described. Choice: A semi-automatic solution is described. It involves a system of tool guidance and a system of tool set-up, both light guided. Two methods for the detection of light signals in the presence of sunlight have been investigated. Choice-automatic; two solutions have been explored. One uses standard data processing, the other "parallel" processing. Here an idealised device is described which will compare for likeness two two-dimensional patterns.

Abstract The aims were to examine the importance of regeneration by seeds, the influence of plant traits and disturbances, and the role of seed-seedling conflicts in regeneration and in the determination of vegetation structure. The study was carried out at in a subarctic alpine area (Kilpisjärvi 69°01'N 20°50E', Finland). Seed bank and seedling densities were high in many plant communities (ranges 99 -1109 viable seeds/m2 and 0.2-227 seedlings/m2, respectively). Effective seedling recruitment is reflected in vegetation as a high proportion of plants with poor or no vegetative reproduction ability. This development may take place in meadows and snowbeds where herbs (e.g. Gnaphalium supinum, Sibbaldia procumbens, Veronica alpina and Viola biflora) are abundant. On the other hand, the low proportion of these plants in heath vegetation reflects ineffective seedling recruitment. Floristic similarities between the consecutive phases in the regeneration pathway may be low despite effective seedling recruitment. Clonality, large and small seed sizes and appendaged diaspores limit the movement of species from phase to phase. Generally, disturbances facilitate effective regeneration by seeds. Grazing promotes species with large seed banks and is therefore one reason for high seed bank densities. Freezing and melting processes negate a negative influence of altitude on seed bank densities in the phase of seedlings. However, if disturbances are severe and continuous and the soil is compact, unstable or dry, disturbances are not beneficial. The same is true if there is a shift in the species composition of seedlings from gaps to closed vegetation. This phenomenon occurred in a rich meadow. Seed-seedling conflicts limit regeneration by seeds in low-herb snowbeds and Ranunculus glacialis-Gymnomitrion snowbeds. Vegetative reproduction and infrequent pulses of seedling recruitment negate an influence of short-term seedling recruitment on the spatial structure of vegetation. Extreme conditions, such as low temperatures, instability of the soil and late snowmelt modify the influence of factors that are important in more moderate conditions. To conclude, all transitions limit regeneration by seeds. However, favourable conditions (e.g. moist conditions in a meadow) partly eliminate the obstacles against seedling emergence. Regeneration by seeds therefore has a major impact on the dynamics and structure of vegetation. In heath vegetation, where bare soils are dry and the moss cover is thick, large seed banks and seed rains do not guarantee effective seedling recruitment. The regeneration process is reduced in the early phases, and plants that reproduce primarily by seeds have a minor role in vegetation. The accumulation of seed banks is effective in these circumstances.

No description available.

No description available.