Artificial Seedling Research Articles

Growth, artificial seedling raising and cultivation of Sargassum confusum (Fucales, Phaeophyceae) inhabiting the coast of Shandong Peninsula, China

The seasonal growth, seedling raising and artificial cultivation of Sargassum confusum were studied along the coast of Dong Chudao at the mouth of Sanggou Bay (37°02′12″N, 122°33′51″E). We also compared the growth of juveniles at different temperatures (15, 18, 21, and 24 °C) and irradiances (60, 95, and 130 μmol photons m−2 s−1) when seedlings were raised in a greenhouse. Sargassum confusum in Sanggou Bay began to develop receptacles in early April when the seawater temperature reached 10.8 °C. The receptacles matured in July and released the eggs when the seawater temperature reached 21 °C. The S. confusum thallus grew to maximum mean length (126.6 ± 19.8 cm) and reached the highest mean biomass yield (192.2 ± 40 g dwt thallus−1) in July and then rapidly decayed. Both temperature and irradiance significantly affected the growth of S. confusum seedlings (p < 0.05). The seedlings reached 1005 ± 47.6 μm at 21 °C and under 95 μmol photons m−2 s−1 in 2 weeks. The seedlings grew to approximately 0.5 cm in length in the seedling raising pools in approximately 5 weeks and reached 6 cm in the open sea nursery after an additional 4 months. The seedlings were then separated and inserted between the strands of vinylon ropes and cultivated in the open sea until early July when the seawater temperature reached approximately 21 °C and the maximum thalli length reached 116.4 cm on average. The dry weight of S. confusum harvested from a 4-m cultivation rope was 1.48 kg on average, and the dry weight yield was approximately 8.9 t ha−1.

A pantropical assessment of vertebrate physical damage to forest seedlings and the effects of defaunation

Many of the forces that shape tropical forest plant communities are facilitated by interactions with animals, which can either promote or inhibit plant reproduction and survival across ontogenetic stages. Hunting-induced defaunation can disrupt these interactions, altering tree recruitment, forest structure, and carbon storage, with strong effects at the seed and seedling stages. Research to date has largely focused on how changes to prominent interactions (especially seed dispersal) affect plant species and communities, while concurrent disruptions to less-studied processes may have opposing effects. With a particularly limited understanding of non-trophic interactions – such as physical damage to seedlings by vertebrate trampling, rooting, and digging – it remains difficult to predict the outcomes of defaunation for tropical forest plant communities. We established 1800 artificial seedlings in 18 intact and disturbed sites across the three main tropical forest regions – the Neotropics (Peru), the Afrotropics (Gabon) and the Indo-Malayan tropics (Malaysian Borneo) – to isolate non-trophic vertebrate physical damage from other causes of seedling mortality (herbivory, pathogens, abiotic desiccation, etc.), and to understand its effects in intact and anthropogenically-disturbed forests. We found that vertebrate physical damage is a consistent force in forests across the tropics, and that hunting significantly alters its strength, with a ∼70% decrease in damage in hunted vs. intact sites that resulted in a ∼3.5-fold (350%) increase in artificial seedling survival. Our results reveal an understudied mechanism that may contribute to changes in seedling survival, stem density, and plant community composition in tropical forests subjected to hunting.

Ⅱ-4. ニホンウナギの種苗生産過程で発現する様々な形態異常

Ⅱ-4. ニホンウナギの種苗生産過程で発現する様々な形態異常

Improvement of the zygote utilization and reduction of the seedling loss in the early stage of seedling production of Sargassum thunbergii (Fucales, Phaeophyta)

Artificial seedling production of Sargassum thunbergii is an effective way to relieve pressure on natural resources. In order to improve the utilization of zygotes and reduce the loss of seedlings, studies on the characteristic of the zygotes release, the development of rhizoids, the attachment of germlings, and the influence of jet washing were conducted. Results show that the percent of zygotes released was increased with time in the first 60 h. The capacity of germlings attached to the substratum was significantly increased, especially coincident with the time of the new rhizoids emerged and elongated. The detachment rate of germlings significantly decreased with the delay of starting time of jet washing or the reduction of jet washing velocity. However, the jet washing at any level applied in the experiment could cause considerable loss of germlings within the 20 days after the attachment. Our study provided some parameters to optimize the operation in the early stage of seedling production.

An orthogonal design to optimize seed production, out-planting, and cultivation of the industrially overexploited red alga Gracilaria edulis (Rhodophyta)

Marine algal resources are of significant importance due to their renewable nature and plentiful availability; however, they also are subjected to indiscriminate harvesting. Despite multi-organizational efforts under the Bay of Bengal Program implemented by the Food and Agriculture Organization (FAO) of the United Nations, the Indian agar industry still heavily relies on the natural harvest of Gracilaria edulis from the southeastern coast of the Gulf of Mannar. Experimental cultivation of this species has been successful, but lack of a year-round supply of quality seed material has hampered the prospects of undertaking commercial farming. To maximize the efficiency of artificial seedling production, we used a Taguchi orthogonal array design to determine the optimal temperature, salinity, and pH for seedling production from primary, secondary, and tertiary fragments. The maximum growth was obtained at 25 °C, 20 ppt salinity, and pH 7.5, where the highest daily growth rate (DGR) of 4.88 ± 1.04 % day−1 (K 3 = 3.194) was recorded in tertiary fragments. The DGR of seedlings grown with shaking as well as static cultures ranged from 8.33 ± 1.50 to 10.26 ± 0.01 % day−1 after 10 days. Analysis of variance (ANOVA) showed that water motion did not significantly affect growth. The out-planting was successful for seedlings derived from laboratory culture. Among the two harvesting methods examined, namely complete and clipping harvest, the former resulted in the highest biomass yield (7.21 ± 0.83 kg fresh wt m−2) and DGR (5.93 ± 0.11 % day−1). A statistically significant difference (F = 16.976; p < 0.001 and F = 3.359; p < 0.02) was observed for yield and DGR, respectively, between the methods. It is thus imperative to augment the algal stock for year-round mariculture thereby negating the consequences of overexploitation.

Progression in artificial seedling production of Japanese eel Anguilla japonica

Eel aquaculture, though thriving nowadays, is totally dependent on the successful capture of wild eel fry and glass eels for its seedlings. The declination of eel resources in recent years has resulted in an urgent need for technology development in artificial seedlings production on an aquaculture basis, in order to protect natural resources and to stabilize the eel supply in the farming industry. Since the life history of the eel holds many mysteries, artificial hatching and rearing of larvae has long been regarded as an extremely difficult task. However, in recent years, the spawning ground of the Japanese eel has finally been located after continuous effort with intensive marine surveys, in which wild parental eels were captured, followed by the collection of fertilized eggs and the harvest of newly hatched preleptocephali. Meanwhile, through the collaborative efforts of many researchers, progress has also been made in improving technologies for artificial maturation of parental eels, which do not mature naturally in captivity, as well as in the technology for artificial hatching. Moreover, a technology for producing feed-rearing eel hatchlings, the most challenging process of all, has advanced rapidly after suitable feed was developed in the 1990s. Then, in 2002, for the first time in the world, larvae were successfully reared up to the glass eel stage, and second generation artificial hatchlings were born in 2010. In this way, eel farming technology that is not reliant on natural resources has been developed. There are strong hopes now for a technology for stable mass production of glass eels to be developed in the near future.

Effects of starvation on survival, growth and development ofExopalaemon carinicaudalarvae

This study aimed at evaluating the effects of two starvation modes (fasting-feeding mode and feeding-fasting mode) on survival, growth and development of mysis larvae of Exopalaemon carinicauda. It showed that food restriction significantly affected the survival, growth and development in both starvation modes. With the extension of initial starvation period, a significantly reduced survival rate during metamorphosis was observed. In the fasting-feeding mode, the duration of metamorphosis was extended and the body lengths of the individuals, which experienced successful metamorphosis to the post-larval stage 1, were much shorter. In the feeding-fasting mode, the extension of initial feeding period led to dramatically increased survival rate and body lengths, while there was no significant difference in duration of metamorphosis of those groups that reached to post-larval stage. The 50% point-of-no-return and the 50% point-of-reserve-saturation were 3.85 days and 4.81 days respectively. The results of this study indicate that E. carinicauda mysis have the ability to withstand or recover from relatively extended starvation, but to ensure the success of commercial seedling, timely and adequate feeding is necessary. The information obtained from this study could provide a basis to optimize the feeding schedule of artificial seedling of E. carinicauda.

말백합 Meretrix petechialis (Lamarck) 인공종묘의 대량생산

ABSTRACT Mass production method on artificial seedling production of hard clam Meretrix petechialis was developed indoor culture system. Spawning of adult clam (SL 65.8 ± 8.4 mm) was induced using the combined method of air exposure and water temperature raising. The fertilized eggs were developed to D-shaped larvae after 17.7 hours at 27℃ and hatching rate was 6.1%. Shell length (SL) of D-shaped larvae was measured to be 131.4 ± 2.6 μm and thereafter the larvae grew to the settled spats with SL 190.2 ± 7.5 μm in 4 days. Estimated survival rate of settled spats was 48.1%. Spat collection on 130,000 spats with SL 0.19 ± 0.01 mm performed conducted by sand bottom circulation filtering method. Collected spats grew up to 3.1 ± 0.8 mm in 46 days, 6.6 ± 1.8 mm in 87 days, and 10.5 ± 0.9 mm in 114 days. The relative growth between SL and shell height (SH) was calculated to be SH = 0.8501SL + 0.0196 (R 2 = 0.9987) during the whole spat period. During spats rearing, they were suffered from one time of mass mortality at SL 3.1 mm, but 51,000 spats were finally survived with the rate of 39.2% at 114 days of spat rearing in indoor tank system.

Storage, Cutting and Culture Conditions of Filamentous Roots of Hiziki Sargassum fusiforme

To develop an artificial seedling production method of Hiziki, Sargassum fusiforme, the effect of storage, cutting and culture conditions on the formation of erect stem from filamentous roots separated from holdfasts were examined. After the Hiziki harvest in end of April 2007, holdfasts remaining on cultivation ropes were collected, loosened to separate the filamentous roots and washed with the culture medium. Optimum storage irradiance of the filamentous roots, temperature and irradiance for erect stem formation and growth, and the width of cut filamentous roots were examined. Optimum temperature and irradiance to store filamentous roots were 12degC and 25micromol/square m/s at 12L:12D cycle. A temperature of 23degC and irradiances ranging 120-230micromol/square m/s at 12L:12D cycle were more suitable for erect stem formation and growth. Forty culture days after cutting, 85% of the filamentous roots formed erect stems and the mean total length of young thalli reached about 5mm. Filamentous roots cut finely to less than 2.5 mm width resulted in 3 times more erect stems than those cut to larger than 5mm. Above results suggest the possibility of artificial seedling production from cut filamentous roots.

Early development of grateloupia turuturu (Halymeniaceae, Rhodophyta)

Grateloupia turuturu is a commercial red alga with potential value in nutraceuticals and pharmaceuticals. To supplement information on its life history and verify whether carpospores can be used for seedling culture, early development of G. turuturu was investigated under culture conditions (27°C, 10–13 μol/(m2·s) in irradiance, photoperiod 10:14 h L:D). Three physiological stages were recognized by continuous microscopic observation: division stage, discoid crust stage, and juvenile seedling stage. At the beginning of the division stage, the carpospores developed germ tubes into which the carpospore protoplasm was evacuated, and then the carpospore protoplasm in the germ tubes began to divide continuously until discoid crusts formed. Finally, upright thalli appeared on the discoid crusts and developed into juvenile seedlings. It took about 60 days for carpospores to develop into juvenile seedlings. The growth parameters, including germination rate for carpospores and discoid crust diameter, were recorded. These results contribute more information on the life cycle, and at the same time are of great significance in the scaling-up of artificial seedling cultures of G. turuturu.

BIOCHEMICAL MARKERS: A USEFUL TOOL FOR ASSESSING GENETIC DIVERSITY IN JACKFRUIT (ARTOCARPUS HETEROPHYLLUS LAM.)

Using polyacrylamide gel electrophoresis, peroxidase and esterase isozymes were investigated from leaf tissue samples of 44 selected (superior) jackfruit genotypes. These selected genotypes were collected following jackfruit descriptor 2000, after surveying 1500 trees in the districts of Nadia, 24 Parganas (N) and Coochbehar in West Bengal. The selected genotypes were analyzed for isozyme variation for peroxidase and esterase. Polymorphism was observed in both the enzyme systems studied, where several bands were found showing similarities and dissimilarities among the selected types. In the peroxidase assay, 7 loci were identified among the 44 genotypes. The relative mobility (R m ) values of the loci ranged between 0.29 and 0.50. Whereas in the esterase assay, 6 loci were identified and the relative mobility (R m ) values of the loci ranged between 0.22 and 0.65. Moreover, it was observed that genotypes collected from nearby locations did not show similar banding patterns, indicating that forces other than geographical origin, such as exchange of genetic stocks, genetic drift, spontaneous variation, natural and artificial selection, cross pollination and seedling origin of the plant are responsible for the genetic diversity.

Are biotic and abiotic factors and seedling mechanical damage in forest-edge fragments always different from the interior?

The regeneration of fragments and adjacent landscape depends on, among others factors, seedling establishment, both in the interior and at the edge. This work considers differences between the edge and fragment interior in (1) environmental descriptors (canopy openness, temperature, soil moisture, bamboo and liana coverage and litterfall), (2) the total number of seedlings damaged and (3) the type of seedling damage. The present study was carried out in four Atlantic forest fragments in south-eastern Brazil. Environmental descriptors and artificial seedling damage were measured in 10 plots, 10 × 10 m each, in each forest fragment, i.e. five at the edges and five in the interior. Litterfall was the main cause of seedling damage in the present study. Bamboo and liana coverage, litterfall, soil moisture, canopy openness, minimal and maximal temperature and temperature amplitude, as well as the type and quantity of damage did not differ between the edge and the fragment interior. Temperature, however, was higher in the interior than in the edge fragments. The lack of difference between the edge and interior fragments was probably due to the reduced size of the remnants of the Atlantic forest studied, resulting from an intense internal anthropogenic impact on them and the early onset of this landscape fragmentation, which is quite old (~200 years).

Microsite heterogeneity in litterfall risk to seedlings

Abstract Litterfall is an important cause of damage and mortality to seedlings in many forest ecosystems. This study is the first to investigate the contribution of variable risk of litterfall damage to microsite heterogeneity. Two hundred artificial seedlings were ‘planted’ in the ground at 2‐m intervals along transects in each of two New Zealand forests, and all plant species with foliage directly above each artificial seedling were recorded. Additional artificial seedlings were planted on the ground underneath treeferns and on their trunks (epiphytically). The artificial seedlings were monitored monthly for damage over 2 years. Three overtopping species that cause litterfall damage, along with one species that impedes litterfall, produced different microsites with a hierarchy of litterfall damage risk to seedlings (2–30% per year). This risk differed significantly among microsites (P &lt; 0.0005). Seedlings differ in resilience to litterfall and, therefore, microsites with different litterfall risks provided the potential for regeneration niche differentiation. More seedlings were damaged beneath Cyathea dealbata (Cyatheaceae), which drops whole fronds, than on its trunks. The reverse was found for Dicksonia fibrosa (Dicksoniaceae), which retains dead fronds as a ‘skirt’. We suggest that shedding whole fronds, or producing a skirt of fronds, are alternative ‘strategies’ that can reduce competition from terrestrial and epiphytic seedlings, respectively.

Use of artificial seedlings to estimate damage of forest seedlings due to litterfall and animals

Abstract. The artificial seedling assay method has been used in several tropical and temperate forests to estimate seedling damage and subsequent mortality due to non‐trophic micro‐disturbances such as litterfall and trampling. However, there has been no evidence presented to support the assumption that artificial seedling damage correlates with natural seedling mortality. In this study we evaluated the use of artificial seedlings in five New Zealand forests by comparing damage rates of artificial seedlings with damage and mortality rates of an equal number of selected natural seedlings. A total of 1200 artificial, and 1200 natural seedlings were monitored monthly for two years.Litterfall damage rates of natural seedlings were correlated with those of artificial seedlings. However, there was no relationship found between artificial and natural seedling damage due to animals, or between artificial seedling damage and natural seedling mortality for either cause. Artificial seedlings should not therefore be used to estimate seedling mortality due to non‐trophic microdisturbance. Monitoring natural seedlings enabled non‐trophic animal damage to be readily detected and provided additional information on animal‐plant interactions.The value of using artificial seedlings is that they provide a measure of the litterfall disturbance potential that is independent of the patchy distribution of natural seedlings within safe sites, and independent of species specific resistance to damage. They therefore provide an indication of the selective pressure on seedlings due to litterfall and are useful for comparing the relative ‘safety’ of different forests and microsites. Monitoring natural seedlings provides a measure of the damage and mortality due to litterfall for a specific seedling size class. Concurrently monitoring artificial and natural seedlings for litterfall disturbance provides more information than the same effort expended on either method alone.

Use of artificial seedlings to estimate damage of forest seedlings due to litterfall and animals

Abstract. The artificial seedling assay method has been used in several tropical and temperate forests to estimate seedling damage and subsequent mortality due to non-trophic micro-disturbances such as litterfall and trampling. However, there has been no evidence presented to support the assumption that artificial seedling damage correlates with natural seedling mortality. In this study we evaluated the use of artificial seedlings in five New Zealand forests by comparing damage rates of artificial seedlings with damage and mortality rates of an equal number of selected natural seedlings. A total of 1200 artificial, and 1200 natural seedlings were monitored monthly for two years. Litterfall damage rates of natural seedlings were correlated with those of artificial seedlings. However, there was no relationship found between artificial and natural seedling damage due to animals, or between artificial seedling damage and natural seedling mortality for either cause. Artificial seedlings should not therefore be used to estimate seedling mortality due to non-trophic microdisturbance. Monitoring natural seedlings enabled non-trophic animal damage to be readily detected and provided additional information on animal-plant interactions. The value of using artificial seedlings is that they provide a measure of the litterfall disturbance potential that is independent of the patchy distribution of natural seedlings within safe sites, and independent of species specific resistance to damage. They therefore provide an indication of the selective pressure on seedlings due to litterfall and are useful for comparing the relative ‘safety’ of different forests and microsites. Monitoring natural seedlings provides a measure of the damage and mortality due to litterfall for a specific seedling size class. Concurrently monitoring artificial and natural seedlings for litterfall disturbance provides more information than the same effort expended on either method alone.

Seedling Mortality by Litterfall in Amazonian Forest Fragments1

ABSTRACTPhysical damage caused by litterfall is a source of seedling mortality that can be influenced by environmental disturbances, such as the isolation of forest fragments due to habitat destruction. The impact of physical damage in seedling mortality was evaluated in forest fragments and continuous forests in central Amazonia using artificial seedlings. A total of 11 reserves distributed among three sites were studied: three 1–ha, three 10–ha, two 100–ha, and three continuous forest reserves. In each reserve, ten transects each comprised of ten artificial seedlings were monitored for one year at four–week intervals. Survival curves were compared using failure time analysis, and the effect of reserve size on artificial seedling mortality after one year was analyzed with a categorical model. In the analysis of survival curves, artificial seedling survival was significantly greater in the continuous forest than in the 10–ha reserve at one site only, a result that may have occurred by chance. After one year, artificial seedlings suffered similar mortality due to litterfall among the reserves sampled. Physical damage by litterfall varied from 28 to 35 percent annually in the 1–and 10–ha forest fragments compared to 20 to 24 percent in the continuous forest. Mortality of artificial seedlings in the continuous forest was similar to other tropical sites in which the same method has been used, and may indicate that litterfall plays an important role in seedling mortality in the terra firme tropical forests of central Amazonia.

Seedling-aided cache detection by heteromyid rodents.

Heteromyid rodents are granivores which frequently cache seeds in numerous scattered locations and use olfaction to relocate these caches. However, seedlings which emerge from these caches may also serve as cues to cache location. We conducted an experiment in the western Great Basin to determine whether heteromyids perceive emerging seedlings of Indian ricegrass, Achnatherum hymenoides, as beacons to cache locations. Specifically, we compared frequencies with which heteromyids searched for seeds among locations differing in the presence or absence of buried seeds and above-ground seedling treatments, which included either a single Indian ricegrass seedling or an artificial seedling proxy. The olfactory cue related to seeds was clearly important in relocating caches, as digging by heteromyids near artificial seedlings and at control locations lacking seedlings was significantly more likely if seeds were present. However, rodents dug for seeds near natural seedlings at similar frequencies regardless of whether a seed cache was actually present at the base of the seedling. Moreover, seeds had no effect on the frequency at which rodents exhibited investigative, superficial digging behavior near artificial seedlings. The latter results indicate that heteromyids do associate emerging seedlings with cache locations, and that this association may primarily be a beacon to potential cache locations. Seedling-aided cache detection is important because it could improve the effectiveness of cache-searching behavior during a period when recovery of caches is critical for survival.

Seedling Mortality by Litterfall in Amazonian Forest Fragments1

Abstract Physical damage caused by litterfall is a source of seedling mortality that can be influenced by environmental disturbances, such as the isolation of forest fragments due to habitat destruction. The impact of physical damage in seedling mortality was evaluated in forest fragments and continuous forests in central Amazonia using artificial seedlings. A total of 11 reserves distributed among three sites were studied: three 1-ha, three 10-ha, two 100-ha, and three continuous forest reserves. In each reserve, ten transects each comprised of ten artificial seedlings were monitored for one year at four-week intervals. Survival curves were compared using failure time analysis, and the effect of reserve size on artificial seedling mortality after one year was analyzed with a categorical model. In the analysis of survival curves, artificial seedling survival was significantly greater in the continuous forest than in the 10-ha reserve at one site only, a result that may have occurred by chance. After one y...

Impact of Alternative Regeneration Methods on Genetic Diversity in Coastal Douglas-Fir

Abstract Genetic implications of natural and artificial regeneration following three regeneration methods (group selection, shelterwood, and clearcut) were investigated in coastal Douglas-fir (Pseudotsuga menziesii var. menziesii [Mirb.] Franco) using genetic markers (17 allozyme loci). In general, harvesting followed by either natural or artificial regeneration resulted in offspring populations little altered from those in the previous generation. Cutting the smallest trees to form shelterwoods, however, resulted in the removal of rare, presumably deleterious, alleles, such that slightly fewer alleles per locus were observed among residual trees (2.76) and natural regeneration (2.75) than found in uncut (control) stands (2.86). Thus, although the shelterwood regime appears quite compatible with gene conservation, it would be best to leave parent trees of a range of sizes in shelterwoods designated as gene conservation reserves, in order to maximize the number of alleles (regardless of current adaptive value) in naturally regenerated offspring. Seedling stocks used for artificial regeneration in clearcut, shelterwood, and group selection stands (7 total) had significantly greater levels of genetic diversity, on average, than found in natural regeneration. This is probably because the seeds used in artificial seedling stocks came from many wild stands and thus, sampled more diversity than found in single populations. For. Sci. 44(3): 390-396.

Special Feature: Recent problems in oak decline Preface

Occurrence of severe dieback, decline, and mortality in oak (Quercus spp.) stands have been reported frequently during the last 20 years in various parts of the world. As a result, numerous research activities have been initiated. 'Recent Problems in Oak Decline' was also the topic of a meeting of the International Union of Forestry Research Organizations (IUFRO) units Sl.06.00, S2.06.00 and S2.07.00 at the IUFRO XX World Congress held in Tampere, Finland during August 1995. A selection of five papers presented during this meeting is published in this issue in which symptoms of oak damage are characterized and potential causal factors as well as factor combinations (insects and fungi, climatic factors, site-related aspects, genetics) are described. DONAUBAUER, Austria, summarizes the macroscopic symptoms of oak decline and reports on the regional role of parasites as predisposing and as contributing factors. S!WECKI and UFNALSKI, Poland, give a review of oak stand decline in Poland with special reference to the role of climatic factors. They found that climatic conditions had a decisive influence on the vigour of Quercus robur. Increased frequency of dry years resulted in the complex phenomenon of oak decline. STEINER, USA, observes oak decline in the context of genetic management. In order to minimi ze susceptibility to oak decline he suggests forest practices which favour the maintenance of high levels of genetic variation and the use of local provenances in artificial regeneration and large seedling populations. Prediction models for estimating mortality of oak due to gypsy moth (Lymantria dispar), based on a new analysis using defoliation intensity classes as a variable along with species, crown position, and crown condition, are presented by GOTTSCHALK et al. USA. STANDOVAR and SOMOGYI, Hungary, stress the importance of site characteristics and tree growth. Oaks seem more susceptible to decline outside of their natural range. Most presentations stressed the necessity for further investigations because the results are still preliminary and there is a wide variation in responses . The various methodological approaches used in these papers are of special interest. We hope that this collection of papers contributes to the progress on the long path to a better understanding of oak ecosystems and of improving the health of the world's oak forests.