Intraspecific variation in the response of Taxodium distichum seedlings to salinity

Seedlings of 15 open-pollinated families of baldcypress (Taxodium distichum) were tested for their tolerance to combined salinity and flooding strees. Ten of the families were from coastal locations in Louisiana or Alabama, USA, that were slightly brackish. The other families were from locations not affected by saltwater intrusion. Five salinity levels were investigated — 0, 2, 4, 6, and 8 g l⁻¹ artificial seawater—all with flooding to approximately 5 cm above the soil surface. Survival, height growth, leaf area and total biomass all declined with increasing salinity. Significant variation was found among salinity levels, families, and salinity×family interactions for leaf area and total biomass. Two tolerance indices were also developed to compare family response with salinity. In generalm families from brackish sources had greater total biomass, leaf area, and tolerance index values than families from freshwater sources at the higher salinity levels. A selection and breeding program designed to develop moderately salt-tolerant baldcypress seedlings for use in wetland restoration projects and other applications appears to be well-justified.     

落羽杉与池杉幼苗对不同土壤水分含量的生理响应(英文)

研究落羽杉与池杉幼苗对常规水分处理(C)、轻度干旱(MD)、土壤潮湿(WS)以及水淹(FL)等不同水分处理的生理响应特性。与对照组相比,2树种幼苗在轻度干旱与水淹处理条件下叶片自由水含量显著提高,而束缚水含量则显著降低。2树种幼苗在潮湿处理组的叶片自由水与束缚水含量均未出现低于对照组的现象。轻度干旱、土壤潮湿与水淹处理均未导致2树种叶片电导率与丙二醛含量的显著变化(池杉水淹条件下叶片的丙二醛含量变化例外)。水淹处理能显著增加2树种幼苗叶片的可溶性糖含量,同时降低其脯氨酸含量。轻度干旱与潮湿处理能显著增加落羽杉而降低池杉幼苗叶片的脯氨酸含量。尽管同属的2树种幼苗表现出较多相似的响应特征,二者对不同水分逆境胁迫条件的响应仍然存在许多差异。     

Salinity effects and differential germination of several half-sib families of baldcypress from different seed sources

Saltwater intrusion is responsible for the destruction of large expanses of baldcypress swamps along the Gulf of Mexico in the southern United States. Recent restoration efforts have focused on the identification, and subsequent planting, of moderately salt-tolerant plant material within these ghost forests. The long-term persistence of cypress swamps in these areas, however, will ultimately depend on the germination of seeds from the improved parent trees. This study investigates the germination capacity of seeds collected from baldcypress parent trees, located in both freshwater and brackish water environments. Seeds were tested at four different salinity levels under controlled conditions for a period of 65 days. Mean germination under the 0, 2, 4, and 6 g l^-1 seawater treatments was 26.3, 22.9, 15.4, and 10.2%, respectively. Although none of the eight families used in this study had a germination greater than 50%, three families demonstrated superiority in their germination capacity under all four salinity treatments. In general, brackish water seed sources had greater germination success than the two families from freshwater sources. Results indicate that families previously identified as moderately salt-tolerant based on physiological and morphological parameters may be equally successful in seed germination capacity under moderately saline conditions.     

Effect of NaCl and high pH on seedling growth of 15 Eucalyptus camaldulensis Dehnh. provenances

Eucalyptus camaldulensis Dehnh. is a moderately salt-tolerant Australian tree species widely used in farm forestry, often in salt-affected landscapes. In a glasshouse experiment, E. camaldulensis seedlings from 15 wide-ranging Australian seed sources (provenances), were cultured in sand-filled pots and treated for 57 days with control (no added NaCl in tap water, neutral pH), saline (150 mol m^–3 NaCl, stepped high pH (pH 7.6 to 9.5) and combined NaCl and high pH solutions. Significant differences were found among provenances in height and shoot dry weight. Differences in provenance response to treatment were found for dry weight but not for height. Reductions in shoot dry weight due to NaCl and high pH ranged from 42.9% to 82.0% and 4.3% to 51.7% respectively. Provenances from Lake Hindmarsh-SE (Victoria) and Lake Albacutya-N (Victoria) had relatively high tolerance to both stresses whereas those from Lake Albacutya-S (Victoria), Lowan Valley (Victoria), Silverton (New South Wales) and Katherine (Northern Territory) had low tolerance to both stresses. Provenances from De Grey River and Fitzroy River (Western Australia) were most tolerant of high pH. The performance of these provenances in this experiment generally accorded well with that in saline field environments.     

Natural regeneration of baldcypress (Taxodium distichum (L.) Rich.) in a Louisiana swamp

Due to large reserves of second-growth cypress (Taxodium distichum and T. distichum var. nutans) in the southeastern United States, logging of cypress is once again becoming attractive. This increased activity has led to the question of whether adequate natural regeneration will be established after logging. Four logged cypress stands in the Barataria Basin region of Louisiana were sampled to determine vegetation characteristics and survival and growth of baldcypress seedlings and stump sprouts. Coppice regeneration was prolific during the first year after cutting, however, most of the sprouts died in the following years. In addition, even though observations were made during a particularly dry year, no seedling establishment occurred.     

Effects of submergence in water on seed germination and vigor of the Copaifera lucens （Fabaceae） seedlings

We analyzed the tolerance of Copaifera lucens seeds to sub- mersion in water to assess the use of this species for direct seeding in riparian forest restoration programs. Seeds were submerged in water for 2, 4, 8, 16 and 32 days or not submerged （control = 0 days of submer- gence）. For the control and at the end of each period of submersion, germination and seedling vigor tests were carried out. For germination tests, seeds were sown in plastic pots containing sand and kept in labora- tory conditions. The percentage of seed germination, the germination rate and the average germination time were analyzed. For seedlings, total biomass, leaf area, leaf mass per area and leaf area ratio were analyzed. Submersion time drastically affected the dissolved oxygen content and seed germination. Between 4 and 8 days of submersion there was a de- crease from 83.8% to 15.6% in the germination percentage. No seed germination occurred after 16 days of submersion. Although there was a significant decrease in the percentage of seed germination between 4 and 8 days of submersion, seedling vigor was not affected. Seeds of this species were partially tolerant to submersion in water, suggesting that C. lucens is a promising species for direct seeding in riparian forest restora- tion projects.     

银杏育苗技术试验研究

为探讨银杏壮苗培育技术,于１９９６年进行了银杏有育苗试验研究,结果表明,选择有胚率高的大粒种子进行播种,易发芽出苗,且苗木粗壮,育苗对宜选择排水好的圃地进行育苗,苗床宜高,沟深应在２５ｃｍ以上,播种后即用地膜覆盖,能提高出苗率,提早出苗,提高生长量,夏季高温时,用塑料遮阳纱遮阳,可防止苗木曝晒,提高苗木保存率,促进苗木生长。     

The soil seed bank of the threatened plant <Emphasis Type="Italic">Magnolia stellata</Emphasis> is subordinate to the emergence of current-year seedlings

We studied seed bank formation of the threatened star magnolia, Magnolia stellata, to examine the early stage of regeneration. Forty-five seedling plots (2 × 2 m), each including a soil-sampling quadrat (40 × 40 cm), were established randomly under or around the crowns of mature M. stellata trees. Seeds of M. stellata were collected from each quadrat to a depth of 5 cm. Only four seeds of M. stellata were found (0.56 seeds/m²) and all were located under mature crowns. Current-year seedlings were abundant in water channels, on moss, or under mature crowns, suggesting that the seeds may require wet soil conditions for germination. Magnolia stellata seeds show considerable germination below the crowns of mature trees in the year following masting, while some seeds remain dormant in the soil. Considering the soil seed bank and the current-year seedling bank of M. stellata, a frequent supply of seed is essential for the regeneration of this species. Thus, it is important to maintain mature trees in addition to promoting seed production.     

国外林木种苗发展概述

文中对林业发达国家林木种苗管理体系、生产体系和保障体系进行了归纳和阐述,并结合我国情况,提出了林木种苗持续发展的建议。     

Underplanting Cherrybark Oak (Quercus pagoda Raf.) Seedlings on a Bottomland Site in the Southern United States

We initiated a study on a bottomland site in the southern United States to examine the effects of Japanese honeysuckle (Lonicera japonica Thunberg) control and seedlings of two root classes on survival and growth of underplanted cherrybark oak (Quercus pagoda Raf.) seedlings. Three honeysuckle control treatments were assigned to nine 0.5-ha plots in a stand harvested to 30% residual stocking. Treatments included a spring 1997 herbicide application (Escort^®, metsulfuron-methyl), a similar application in the late summer of 1997, and a control (no herbicide application). In 1998, half of each treatment plot was planted with seedlings having four or more first-order lateral roots > 1 mm in diameter, while the other half of each plot received seedlings with fewer than four lateral roots. Four years after treatment, the early season application reduced honeysuckle biomass 60% relative to the other treatments, but we did not observe a survival or growth response by underplanted seedlings. Three years after establishment, seedlings that initially had four or more lateral roots were 16% taller and 18% larger in root-collar diameter than seedlings in the other class, but these differences were primarily due to initial size differences maintained through the study period. Over all treatments, oak seedlings averaged 87% survival while showing a 300% increase in height and a 170% increase in root-collar diameter 3 years after planting. Our results suggest that partial stand harvesting followed by underplanting may be a viable approach for establishing cherrybark oak reproduction on bottomland sites of the southern United States.     

Variation in seed and seedling traits among natural populations of <Emphasis Type="Italic">Trigonobalanus doichangensis</Emphasis> (A. Camus) Forman (Fagaceae), a rare and endangered plant in southwest China

The extent of genetic variation in seed and seedling traits of Trigonobalanus doichangensis, a rare and endangered tree in southwest China, was evaluated at the population level. Seeds were collected from four natural populations in the south and southwest Yunnan province, China. Significant differences (P < 0.05) between populations were observed in seed length, seed weight and seedling morphological characters. The analyses revealed that none of the seed and seedling traits had significant correlations with the geo-climatic variables of the populations. Among seed and seedling traits, significant correlations (P < 0.05) were discovered among seed length, seed weight and height of 30-day-old seedlings. Significant correlation (r = 1.00, P < 0.01) occurred also between the height and root collar diameter of 4-year-old seedlings. With the exception of seed width and seed germination percentage, 51–96% of total variation in other seed and seedling related traits was attributed to population effect, as determined by the broad sense heritability. In conclusion, these observations on variation in seed and seedling traits should be a reference point, when considering seed collection of this species for ex situ conservation and species restoration.     

Variation in Seed and Seedling Traits of Celtis australis, a Multipurpose Tree, in Central Himalaya, India

Seeds of Celtis australis were collected from 13 different sources, ranging from 550 to 1980 masl, in Central Himalaya, India. Significant (p = 0.05) variations were observed for seed traits among provenances. However, among various characters, seed weight exhibited maximum variation between seed populations compared to other morphological characters. Between provenances, seed weight ranged from 47.8 to 83.1 g/1000 seed, with mean value of 66.9 ± 10.7 g/1000 seed. Significant (p = 0.01) positive correlation was found between morphological characters of seeds including seed weight and elevational range of seed source. For one year old seedlings, average shoot and root growth was 61.1 ± 13.3 and 30.5 ± 5.4 cm, respectively, irrespective of provenance variation. Inter-comparing biomass yield of the seedlings with altitude, average biomass production was 8.4 ± 2.5, 9.4 ± 3.3 and 12.7 ± 1.7 g/plant, respectively, for low (550–1000 masl), middle (1050–1250 masl) and high (1350–1980 masl) altitudinal populations. Significant (p = 0.01) positive correlation between growth performance of seedlings and altitude of the seed source was recorded. Across the provenances, shoots had the highest proportion of total biomass (42.3%), followed by leaves (32.6%) and roots (24.6%). Among various provenances, Badiyargaon, Agroda, Guptakashi, Jakholi, Gajeli, Srinagar and Palampur populations produced heavier seedlings and grew faster compared to seedlings of other sources.     

Chloroplast DNA variation of northern red oak (Quercus rubra L.) in Indiana

Chloroplast DNA (cpDNA) variation was examined in 48 northern red oaks at 14 sites representing contrasting glacial histories and age structures within the state of Indiana in the United States. PCR-RFLP of three intergenic regions revealed five haplotypes. Haplotype I was common to seven sites and was the most frequent (17 trees). Haplotype II was common to five sites and was nearly as frequent as haplotype I (16 trees). Haplotypes III, IV and V were equally infrequent and did not occur together. Genetic diversity resided among rather than within populations (G_ST = 0.73 ± 0.14). This preliminary survey shows that cpDNA diversity will be a useful tool for the investigation of ancient seed dispersal patterns in northern red oak.     

Fluctuating Fortunes of a Collective Enterprise: The Case of the Agroforestry Tree Seeds Association of Lantapan (ATSAL) in the Philippines

The Agroforestry Tree Seeds Association of Lantapan (ATSAL) in Bukidnon province of Mindanao, Philippines, was organized in 1998, facilitated by the World Agroforestry Centre (ICRAF). Farmers were trained on germplasm collection, processing and marketing of agroforestry tree seeds and seedlings. ATSAL has been marketing various tree seeds and seedlings with apparent success, and has provided training on seed collection and nursery management to farmers, government technicians, and workers from non-government organizations. This paper reports initial results of a continuing study to assess the effectiveness of ATSAL’s marketing strategy, including group dynamics, and the issues and challenges the group faces. It was found that during the first 2 years, ATSAL’s market share of highly demanded timber tree species grew rapidly, thus helping to disseminate widely these important species among farmers. ICRAF’s technical back-up was an advantage, increasing the Association’s market credibility. Subsequently, ATSAL extended its market to the central Philippines, but failed to meet the demand for seeds due to organizational limitations. Market competition exists, where a non-member was able to take a larger market share than was the group. Nonetheless, ATSAL has established its name as a viable community-based seed and seedling producer, maintaining a stronghold in local and regional markets. Collective action is important for smallholders to gain market access, but is unlikely to sustain sales. Facilitating smallholder collective action is essentially an arduous task, requiring the supporting agency to hold a firm grasp of market realities, to invest in the maintenance of collective action, to provide continuous technical back-up, and to ascertain the conditions that make collective action succeed.     

Improving the collection and germination of West African <Emphasis Type="Italic">Garcinia kola</Emphasis> Heckel seeds

Garcinia kola is highly used as chew-stick for dental care in West Africa, but it is nearly commercially extinct in nature. To help find methods to increase rate and percentage of germination, we investigated its seed germination responses by using several collections and pre-treatments. Seeds processed from 6-week old green fruits did not germinate, whilst those of 10-week old partly-mature, at the intermediate stage through full development, germinated 46%. Seeds from orange mature fruits reached maximum 54–62% germination. Radicles emerged 6 weeks after sowing and normal germination with emergence of the primary single shoot growth occurred after 12 weeks. There was no significant difference (P ≥ 0.05) between germination responses of seeds from Ghana and Cote d’Ivoire. Seeds did not germinate when dried to below ca. 30% MC. De-coating seeds or soaking intact seeds in a 70% ethanol solution increased germination to 82–92%, and also increased germination rate; however germination was not uniform. Because difficulties in germinating these seeds stem from the physical presence of the seed coats and the slow growth of the embryos contained therein, we recommend that fresh seeds from mature fruits be de-coated and immediately sown in preferably, an aerated medium (e.g., sawdust) for cultivation.     

Allozyme variation and recent evolutionary history of eastern hemlock (<Emphasis Type="Italic">Tsuga canadensis</Emphasis>) in the southeastern United States

Eastern hemlock (Tsuga canadensis [L.] Carr.) is a widespread and ecologically important conifer species of eastern North America that is threatened by the hemlock woolly adelgid (Adelges tsugae Annand), a pest introduced into the United States from Asia in the 1920s. Information about the genetic composition of eastern hemlock is necessary to guide ex situ conservation efforts in the southeastern United States, where the species is expected to harbor relatively high amounts of genetic variation in areas of Pleistocene glacial refuge. Nineteen allozyme markers were used to quantify the genetic variation present in 20 eastern hemlock populations in the southeastern United States. Results indicate that the species has low levels of genetic diversity in the region compared to most other conifers, but greater population differentiation (F _ST = 0.126). Populations along the eastern periphery and in the Appalachian interior exhibited higher levels of diversity than those along the western periphery of its geographic range. The results suggest that the glacial refuge area for eastern hemlock was likely located east of the southern Appalachian Mountains, and indicate that ex situ conservation seed collections should be concentrated in these areas of higher diversity.     

Influence of environmental conditions on germinant survival and diversity of Scots pine (<Emphasis Type="Italic">Pinus sylvestris</Emphasis> L.) in central Spain

The aim of the study was to investigate dynamics and pattern of natural regeneration and the influence of seedbed and light on germination and initial seedling survival of Scots pine (Pinus sylvestris L.) during three growing seasons. Four 5-m² plots in a natural Scots pine forest in central Spain were randomly established at the beginning of the regeneration process. Germination and seedling survival were recorded in 100 regeneration sampling subplots (0.25 m²) per plot, while seedbed type and the relative light intensity reaching the forest floor was characterised in 1-m² subplots. The spatial correlations between survival, light conditions and organic matter depth were analysed through cross-variograms. Germination and survival were highly variable both within and between plots (ranging from 0 to 89%) and affected by high summer temperatures (33–35°C) in 2003. The spatial pattern characterisation of survival by Ripley’s K function showed a dominant cluster distribution. Occurrence tended to be clumped when abundance was greater than 15 seedlings, whereas for lower densities, seedlings were randomly distributed. Seedlings and herbs occupied the same sites where environmental conditions were appropriate for them to live. Spatial association occurred frequently for light and organic matter depth. Results suggested that the Scots pine seedlings in our study in central Spain preferred moderate light conditions (Global Site Factor <0.40). Thus, if this forest is to be naturally regenerated with Scots pine, the shelterwood system (whereby some mother trees are left to provide shelter for at least 5 years), along with mechanical disturbance of the seedbeds, would promote seed germination, as long as a seed source is present. However, regeneration success is affected by year-to-year conditions.     

Observed dynamics of ponderosa pine (<Emphasis Type="Italic">Pinus ponderosa</Emphasis> var. <Emphasis Type="Italic">ponderosa</Emphasis> Dougl. ex Laws.) seedling recruitment in the Cascade Range,USA

An observational study of early seedling establishment (first 1–2 summers after emergence) was conducted in four ponderosa pine (Pinus ponderosa var. ponderosa Dougl. ex Laws.) stands east of the Cascade Range crest in central Oregon, USA. Newly emerged ponderosa pine seedlings were identified at the start of summer and were monitored through their second summer; a subsequent cohort of seedlings was identified and monitored for one summer. About 3% of the viable seed that was produced resulted in new seedlings. Mortality was substantial immediately following emergence. Most seedlings emerged without shading from understory vegetation, but few survived. Most seedlings alive after one year had emerged beneath live cover; by the end of two summers only shaded seedlings were alive. 63–85% of new seedlings initiated in clusters attributed to rodent caching, and seedlings originating in clusters remained a substantial proportion of the cohort (60%) after two seasons. Results suggest that understory vegetation in these types of stands facilitates the recruitment of ponderosa pine seedlings, most likely by buffering them against environmental stressors during the seedling establishment phase. They also reveal that seed caching rodents are highly active in seed redistribution and can exert a lasting influence on seedling recruitment.     

Obtaining Adequate Light for Planted Bottomland Oak (Quercus spp.) Seedlings: A Case Study Utilizing Midstory Control

Bottomland hardwood forests of the United States have drastically declined since European settlement. Although much of the reported loss has resulted from conversion to agriculture and urban development, thousands of additional hectares have been degraded due to selective harvesting and a lack of effort to establish desirable regeneration prior to harvesting. Research has indicated that seedlings of some oak species perform best with intermediate levels of light, while performing less desirably at both high and low levels. This study demonstrates that controlling undesirable midstory trees through herbicide injection alone can be sufficient to create suitable light conditions for oak regeneration in some circumstances. We were able to increase the average percentage of total available light to 31.5% (SE = 0.029) as compared to only 14.2% (SE = 0.011) in untreated areas (F_1,33 = 46.57, p < .0001). Additionally, oak seedlings planted in areas receiving midstory control exhibited good to excellent survival compared to results of other relevant studies. The present case study supports the belief that performance of oak seedlings can be increased by establishing appropriate light conditions.     

The seed weight did not affect first year's bud‐set in Picea abies

Seeds from each of six full‐sib families of Norway spruce were separated into fractions of light and heavy seeds. The mean difference in 1000 seed weight between the two lots within families was 1.6 g. The terminal bud‐set after the first growth season was assessed in a nursery test. No significant differences between the seedlings from the light and heavy seed lot fraction within full‐sib families were found. No relationships were observed between the 1000 seed weights of the lots and the mean bud‐sets of their seedlings.