Overstory Retention and Stock Type Impact Survival and Growth of Underplanted Shortleaf Pine Beneath a Hardwood Canopy

This study was established to evaluate underplanting as a method of reestablishing a shortleaf pine (Pinus echinata Mill.) component to a dry upland hardwood stand in the Piedmont region of the southeastern United States. Replicated treatment plots were harvested to retain four levels (approximately 0, 3, 7, and 10 m2 of basal area per hectare) of residual overstory density. One-year-old containerized seedlings with both smaller (93.4 cm3) and larger (113.1 cm3) plugs and bareroot seedlings were underplanted beneath the residual overstory treatments. After five growing seasons, seedling survival averaged 61% and was not meaningfully affected by residual overstory density. Seedling height growth ranged from 1.42 m to 2.61 m and was inversely related to residual overstory density. Containerized seedlings with larger plugs had the highest survival (77.4%) and best height growth (2.11 m), followed by containerized seedlings with smaller plugs (64.3%, 1.76 m) and bareroot seedlings (40.2%, 1.85 m). The results of this study indicated that underplanting containerized seedlings, particularly those with higher plug volume and greater plug depth, was a suitable option for reestablishing shortleaf pine on drier, hardwood dominated upland sites in the Piedmont. However, even low levels of overstory retention suppressed seedling height growth after a few years. Study Implications The study was conducted on a dry upland site typical of the North Carolina Piedmont. Retaining up to 10 m2 ha–1 of oak and hickory overstory basal area did not strongly affect survival among underplanted shortleaf pine seedlings after five growing seasons. However, overstory cover as low as 3 m2 ha–1 had negative effects on height growth of underplanted seedlings over the same time period. Height growth declined as overstory density increased. Containerized seedlings had better survival than bareroot seedlings. Further improvements in survival and height growth were realized by planting containerized seedlings with higher plug volume and greater plug depth.

Practice on growing of forest containerized seedlings applicable to the greenhouse complexes of the Arkhangelsk region

The need to develop and implement innovative forms of reforestation to obtain highly productive tree stands actualize the topic of the article. The purpose of the work is to study and analyze foreign experience and research on the production of softwood containerized planting stock for reforestation and compare it with the practice of greenhouse complexes in the Arkhangelsk region. We used the international bibliographic and abstract database «Scopus», which indexes scientific journals, materials from conferences and publications to search for information. A review of publications has been completed over more than a 20-year period (1999-2019). The world experience study and the results of studies on the cultivation of forest containerized seedlings, in particular, Finland, Sweden, Norway, countries similar in terms of the growth of woody vegetation and the range of tree species to the conditions of the European north of Russia made it possible to highlight current research directions. The treatment of seedlings with a short or long light day; frost resistance of the seedlings; influence of drought, excessive moisture; issues of seedling storage; diseases, pests of seedlings and control of them, as well as problems of selection and seed production; seed quality and their impact on plant growth; influence of cultivation technology and types of planting stock on the effectiveness of planting refers to them. The use of foreign plants for growing ball-rooted planting stock implies a similar technology for the production of forest seedlings in our region. However, climatic features and the availability of various consumables, such as peat, fertilizers, pesticides, etc., necessitate the adaptation of Scandinavian technologies to local conditions and the development of additional techniques. One of the main production tasks is the achievement of standard indicators by seedlings. It is not always possible to achieve the desired results in harsh taiga conditions, therefore it is necessary to use foreign experience in growing ball-rooted planting stock, which allows to increase the production of standard seedlings without compromising their quality. This is a whole range of measures, including work on breeding and seed production, the formation of a plant substrate, lighting, moisture, observing the temperature regime, storage of seedlings, combating diseases and pests, etc., which ultimately are the components of the success of artificial reforestation

Alternative Substrates and Fertilization Doses in the Production of Pinus cembroides Zucc. in Nursery

Rooting substrate and fertilization are key components in the production of containerized seedlings, as they can influence the morphological and physiological characteristics of the plants, which in turn can impact outplanting performance. The objective of the study was to evaluate the effect of four substrates based on mixtures of peat moss (PM), composted bark (CB) and raw pine sawdust (PS), combined with two doses of controlled release fertilizer (CRF) and one non-fertilized control, on the growth of Pinus cembroides Zucc. in the nursery. The treatments were: M1: 50+25+25, M2: 25+25+50, M3: 25+50+25 and M4: 50+50+0 of PM+ CB+ PS (% by volume), respectively. Fertilizer treatments used a controlled release fertilizer (Multicote®): F1: 3 kg m−3 and F2: 6 kg m−3 and a control (WF: with no added fertilizer). The treatments were distributed in a randomized complete block design, with a factorial arrangement of 4 × 3 and six replications. The variables evaluated were: height, seedling diameter, dry biomass, Dickson Quality Index, N, P and K content. Regardless of the substrate, the high fertilizer dose (6 kg m−3) improved most morphological variables. In addition, the high fertilizer dose resulted in foliar N, P and K concentrations within recommended ranges for all substrates. The substrate containing only peat moss and composted bark (M4 + F1 and M4 + F2) had the best growth response. However, the substrate composed of 25% peat moss, 50% composted bark and 25% raw pine sawdust with the high fertilizer dose (M3 + F2) resulted in acceptable seedling growth, and may be preferred if the cost of the substrate is a concern to nursery manager.

Influence of Root System Characteristics on Black Spruce Seedling Responses to Limiting Conditions

Roots directly affect planted seedling adaptation to new growing conditions at reforestation sites. To test the influence of root characteristics on the short-term response of seedlings to limiting resources (water, nutrient, or oxygen), we conducted two experiments. We compared (1) the growth and physiology of three types of four-year-old black spruce (Picea mariana (Mill.) BSP) seedlings (Containerized, highly developed initial roots restricted to a plug; bareroot, less developed but unrestricted initial roots; deeply-planted containerized, restricted initial and adventitious roots) to different combinations of irrigation and fertilization. We also investigated (2) the cellular plasticity of adventitious and initial roots to three irrigation regimes including flooding. Bareroot seedlings had better relative growth rates in height than containerized seedlings, probably due to their larger initial size. On the other hand, containerized seedlings took better advantage of fertilization, as shown by a higher relative growth rate in diameter compared to bareroot seedlings and were less affected by water limitation, possibly due to the root plug acting as an additional water reserve capacity. For containerized seedlings, the presence of adventitious roots was beneficial to height growth and physiological performances compared to seedlings with initial roots only. Adventitious roots showed great cell plasticity, particularly under flooding conditions.

The effect of planting stock and soil scarification on forest regeneration

The present research is a comparative analysis of how the main quality indices of containerized and barerooted coniferous (Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.)) planting stock conform to the existing standards in Estonia, how the plantation development depends on planting stock and natural regeneration on soil scarification. The height of Scots pine containerized seedlings exceeded that of barerooted seedlings by 20%. The height of barerooted Norway spruce transplants exceeded that of containerized seedlings by 19%. The root-collar diameter of containerized pine stock formed 70% and the corresponding index of containerized spruce stock formed 48% of the diameter of the barerooted plants of the same species. Typically, containerized plants had better initial growth increment during the first two to three years after planting but this difference disappeared during the latter years. The growth of Scots pine barerooted and containerized seedlings was similar, while the growth of Norway spruce containerized seedlings was slightly inferior compared to barerooted plants. Survival of both test species was independent of planting stock used. After clear-cutting, certain areas of peatland and mineral areas were disc-trenched and inventoried at the end of the first growing season. The number of all woody plants was determined by microsites – untreated area, furrow, slope, and ridge. The same inventory was repeated 11 growing seasons later. After 11 growth years, a large number of Scots pine trees was found in Rhodococcum, Oxalis and Vaccinium myrtillus site types and drained peatlands. The number of pine plants on microsites on mineral soil was the greatest in furrows and on slopes (34% and 30%), and on peat soil on furrows and in untreated areas (47% and 53%). The number of naturally regenerated Norway spruce trees was the largest in Vaccinium myrtillus, Oxalis-Rhodococcum and Oxalis site types. With regard to microsites, spruce plants were the most abundant in furrows and ridges on mineral soil (31% and 24%) and in untreated areas and on slopes on peat soil (46% and 42%).

Sowing qualities of Hevea brasiliensis seeds

Для создания каучуконосных плантаций гевеи бразильской (Hevea brasiliensis Müll. Arg.) во Вьетнаме обычно используют однолетние саженцы с закрытой корневой системой, выращенные из сеянцев. Потребность в посадочном материале гевеи бразильской все возрастает, особенно если учесть, что применяются все более продуктивные сорта и клоны. Поэтому разработка методов оценки посевных качеств семян гевеи бразильской во всем мире очень востребова- на. Целью нашего исследования было определение влияния массы семян на их всхожесть и биометрические параметры сеянцев. Семена гевеи бразильской были собраны в августе 2015 г. во Вьетнаме на лесосеменной плантации 18–20-летнего возраста в провинции Донгнай. Поскольку для определения посевных качеств семян гевеи бразильской во Вьетнаме ГОСТ не разработан. авторы определяли всхожесть и энергию прорастания на торфяном субстрате в пластиковых кассетах, что позволило не только рекомендовать этот метод для определения посевных качеств семян, но и провести апробацию технологии выращивания контейнеризированных сеянцев. Как показали наблюдения, первые всходы гевеи бразильской появились на девятый день после посева семян. Всхожесть семян определяли на 20-й день после посева. Максимальная всхожесть семян достигает 58,0%. Минимальная составляет всего 16,4%. Всхожесть семян гевеи бразильской зависит от исходной массы семян. Семена с массой до 3,1 г имеют низкую всхожесть до 2,5%. Семена гевеи бразильской с массой более 4,5 г также имею низкую всхожесть до 1,4%. Лучшее показатели всхожести семян гевеи бразильской мы имеем во фракции средних по массе семян от 3,2 до 4,8 г. Всхожесть семян этой фракции может достигать 54%. Таким образом определение посевных качеств семян гевеи бразильской можно проводить методом проращивания семян в кассетах, заполненных питательным торфяным субстратом. Определение биометрических показателей сеянцев гевеи бразильской проводили на 55-й день после посева. Достоверной разницы по высоте и диаметру корневой шейки сеянцев, выращенных из семян различных групп по массе семян не обнаружено. Масса семян гевеи бра- зильской в основном определяет их всхожесть. В теплице летнего типа в ботани- ческом саду Санкт-Петербургского лесотехнического университета в кассетах Plantek-81, заполненных стандартным торфяным субстратом, сеянцы достигли высоты 21–25 см, диаметра корневой шейки 1,7–2,3 мм за 55 дней после посева. Поэтому способ выращивания контейнеризированных сеянцев гевеи бразильской может быть рекомендован и для условий Вьетнама. Plantations of Para rubber trees (Hevea brasiliensis Müll. Arg.) in Vietnam are usually established with one-year-old containerized transplants grown from seedlings. The need for planting material of Hevea brasiliensis is increasing, and so is the demand for more productive kinds of this species and clones. This being so, the development of methods for assessing the sowing quality of Hevea brasiliensis seeds is of significant importance in many countries. The purpose of our research was to determine the influence of the seed mass on their germination and the biometric parameters of seedlings. Seeds of Hevea brasiliensis were collected in August 2015 in Vietnam on an 18–20 year-old seed-growing plantation in the province of Dongnai. Since there is no standard for determining the sowing quality of Hevea brasiliensis seeds in Vietnam, we determined the germination capacity and energy on peat substrate in plastic cassettes, which allowed us not only to recommend the proposed method for determining the sowing quality of seeds, but also to test the technology of growing containerized seedlings. The observations have shown that the first shoots of Hevea brasiliensis appeared on the ninth day after sowing the seeds. Germination of seeds was determined on the 20th day after sowing. The maximum seed germination was 58.0%, whereas the minimum was only 16.4%. The germination capacity of Hevea brasiliensis seeds depends on the initial mass of the seeds. Seeds with mass below 3.1 g have a low germination rate of about 2.5%. Seeds with mass of more than 4.5 g also have a low germination rate of about 1.4%. The best germination of Hevea brasiliensis seeds was recorded in the fraction of medium-sized seeds from 3.2 to 4.5 g. The seed germination of this fraction can reach 54%. Thus, the sowing qualities of Hevea brasiliensis seeds can be determined by seed germination in cassettes filled with a nutrient peat substrate. The biometric parameters of the Hevea brasiliensis seedlings were determined on the 55th day after sowing. There was no significant difference in the height and diameter of the root collar of seedlings grown from seeds of different groups by the mass of the seeds. The mass of Hevea brasiliensis seeds mainly determines their germination. The seedlings that were grown in a summer greenhouse in the botanical garden of the St. Petersburg Forestry University in Plantek-81 cassettes filled with a standard peat substrate reached a height of 21–25 cm and the root collar diameter of 1.7–2.3 mm 55 days after sowing. The proposed method of growing containerized seedlings of Hevea brasiliensis can be recommended for the conditions of Vietnam as well.