Direct seeding has been considered a forest restoration option for centuries. Over the past half century, the use of this practice has declined in developed countries as forest regeneration programs have advanced with the production of quality seedlings that can successfully establish restoration sites. Direct seeding is being reconsidered as a restoration option as the potential size of the worldwide forest restoration program has grown because of massive deforestation in third-world nations and due to global climate change. This review examines direct seeding from a number of perspectives. First, merits of using this practice in restoration programs are defined. Major merits of this option are that it can be done quickly, over hard to reach and large disturbed areas, and at a relatively low cost. Second, current research findings from restoration programs are discussed. The major finding is that seedling establishment rates are low (i.e. typically around 20% of seeds planted) due to site conditions, seed predation and vegetation competition, and field performance (i.e. survival and growth) is lower than planted seedlings. Third, operational practices for the application in restoration programs are reviewed. To successfully conduct direct seeding programs practitioners need to consider seedbed receptivity, seed distribution and seeding rate. Fourth, potential new practices are presented. Some of these new practices attempt to create a more effective means to disperse seed across the site, minimize seed predation or create a more favorable microsite environment. This review provides a synthesis of what is known about direct seeding, thereby allowing practitioners to make a rational decision of whether to apply this practice towards their forest restoration program.
Relation between genetic diversity and mass production of forest reproductive material is discussed in a holistic manner. In industrial forest plantations, narrow genetic diversity is desirable and reproductive material is produced at clone level. On the other hand, in conservation forestry a wide genetic diversity is imperative. Beside management goals, a desirable level of genetic diversity is related to rotation cycle and ontogeny of tree species. Risks of failure are lower in short rotations of fast growing species. In production of slow growing species, managed in long rotations, the reduction of genetic diversity increases the risk of failure due to causes unknown or unexpected at the time of planting. This risk is additionally increased in cases of seed transfer and in conditions of climate change. Every step in production of forest reproductive material, from collection to nursery production, has an effect on genetic diversity mainly by directional selection and should be considered. This review revealed no consistent decrease of genetic diversity during forest reproductive material production and planting.
(2) , Mirko Škorić (1) This study examined whether the morphological attributes of Austrian pine (Pinus nigra ssp. nigra var. nigra Arnold) seedlings measured in the nursery could be used to forecast subsequent field performance over an extended time frame. Seedlings from three seed sources were produced in two types of containers and in bareroot seedbeds. These seedlings were measured for an array of morphological attributes (height, HT; root collar diameter, RCD; shoot height/diameter ratio, HD; shoot and root dry weight, SDW and RDW, respectively; shoot:root ratio, S:R; number of the first order lateral roots, FOLR; and Dickson quality index, DQI) and then planted at two sample plots with different soil depth. Seedling attributes were tested against field survival and growth in the first three years and growth in the twelfth year for their ability to forecast field performance. Correlations between morphological attributes and field performance were stronger for the plot with shallower soil, having potentially drier conditions. HT, HD, and S:R were the best attributes for forecasting seedling survival. HD was the most reliable attribute to forecast growth during the first three years after planting, defining the largest proportion of variation for growth (r 2 =0.36 to 0.86). Morphological attributes were better able to forecast field performance in the first three years at the shallow soil site, with FOLR the best single morphological variable. HT, DIA, and RDW were the best attributes to forecast growth during the first three years after planting on both sites. Morphological attributes were not able to forecast growth 12 years after planting.
This study compares the relation of initial height and root collar diameter of bareroot hardwoods seedlings to survival and growth in first year after planting. A total of six species used in Serbian reforestation programs were tested (four native: Fagus sylvatica, Ulmus laevis, Fraxinus excelsior, and Acer pseudoplatanus and two exotic: Robinia pseudoacacia, and Quercus rubra), at 6 sites with a wide range of environmental conditions. Initial seedling height and diameter were equally related to field performance and better in forecasting growth than survival. The relation between seedlings initial morphological attributes and survival was species specific, while for all tested species growth was positively correlated to seedling size at planting. Although large seedlings kept their advantage in size, smaller seedlings grew at a higher rate. Both initial H and D should be considered as equally important in operational programs for hardwoods seedling quality testing.
Serbian spruce (Picea omorika (Pančić) Purk.) is a rare and endangered tertiary relict and endemic species, with restricted and fragmented natural range in Serbia and Bosnia and Herzegovina, mainly around the mid-course of the Drina river. Since the middle of the 19th century, its natural range declines constantly, followed by a decline in the number of mature individuals. The decline of this forest species is slow and mainly attributed to poor regeneration and low competing ability. Given the foreseen worsening of the climate in forthcoming decades, this decline can only accelerate. In recent years, dieback related to drought has been observed as response to extreme weather events suggesting that Serbian spruce will face difficulties in adapting to climate change within its natural range. However, successful use of Serbian spruce in Central and Northern Europe indicates potentially large adaptive potential of this species which, along with the high genetic variability, outweigh the limited morphological variation, self-fertilization, and limitations related to the restricted natural range in the first place, and, indicates possible directions of migration in the second place. In this paper, current conservation actions are discussed, and strategies for the species survival in a changing environment are suggested. Since migration and adaptation are the least likely responses of this species to climate change, measures such as assisted migration may be the only strategy which will enable persistence of Serbian spruce. Current conservation programs, limited to in-situ actions, need to be supplemented with ex-situ actions and strategies. In the worst case scenario, i.e. for species such as Serbian spruce which are unable to migrate and/or adapt to changing climate, the most suitable sites should be identified and colonized in order to prevent extinction in the near future.
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