Seedling survival

Wetlands dominated by Swamp Paperbarks (Melaleuca spp., Myrtaceae) are common in coastal regions across Australia. Many of these wetlands have been filled in for coastal development or otherwise degraded as a consequence of altered water regimes and increased salinity. Substantial resources, often involving community groups, are now being allocated to revegetating the remaining wetland sites, yet only rarely is the effectiveness of the rehabilitation strategies or on-ground procedures robustly assessed. As part of a larger project investigating the condition and rehabilitation of brackish-water wetlands of the Gippsland Lakes, we overlaid a scientifically informed experimental design on a set of community-based planting trials to test the effects of water depth, microtopography, plant age and planting method on the survival and growth of seedlings of Melaleuca ericifolia Sm. in Dowd Morass, a degraded, Ramsar-listed wetland in south-eastern Australia. Although previous laboratory and greenhouse studies have shown M. ericifolia seedlings to be salt tolerant, the strongly interactive effects of waterlogging and salinity resulted in high seedling mortality (>90%) in the field-based revegetation trials. Seedlings survived best if planted on naturally raised hummocks vegetated with Paspalum distichum L. (Gramineae), but their height was reduced compared with seedlings planted in shallowly flooded environments. Age of plants and depth of water were important factors in the survival and growth of M. ericifolia seedlings, whereas planting method seemed to have little effect on survival. Improved testing of revegetation methods and reporting of success or otherwise of revegetation trials will improve the effectiveness and accountability of projects aiming to rehabilitate degraded coastal wetlands.

Ceratocystis canker, which is caused by the fungus Ceratocystis fimbriata Ellis et Halsted, is one of the most severe diseases of the common fig (Ficus carica L.). In contrast, the wild fig species F. erecta Thunb. is resistant to this fungus. We performed interspecific hybridization between the common fig (seed parent) and F. erecta (pollen parent) through artificial pollination. Even though hybrid seeds showed high germination rates, the seedling survival rates were low. All of the seedlings contained the expected simple sequence repeat (SSR) alleles from both common fig and F. erecta at each of the three loci tested, thus confirming the parent–offspring relationships of the interspecific hybrids. The leaf morphological characters of hybrid seedlings were intermediate between those of the parents. Cuttings of cultivars of common fig, F. erecta, and hybrid seedlings were inoculated with C. fimbriata by direct wounding of the shoot. All of the common fig cultivars tested withered and died within 10 weeks. Leaves and shoots of the hybrids and F. erecta were healthy 100 days after inoculation. Our results suggest that interspecific hybridization between the common fig and the wild species F. erecta is a breakthrough in the breeding of a new fig rootstock source with resistance to Ceratocystis canker.

Although natural regeneration is often the best method for establishing new oak (Quercus spp.) stands, there are increasingly more situations in which high potential for oak regeneration failure dictates the use of artificial regeneration including direct seeding and planting seedlings. Additionally, afforestation planting programs frequently incorporate oak species. Artificial regeneration of oak stands is challenging for numerous reasons. In this article we synthesize the current state of knowledge regarding growing and planting the major oak species in the eastern United States, point out critical research gaps, and provide some general growing, planting, and stand tending guidelines and recommendations. Adequate site preparation, careful planting of healthy, genetically adapted seed or seedlings of high morphological and physiological quality, and subsequent control of competing vegetation and browse damage are necessary actions to assure regeneration success. Oak seedling survi...

In Madagascar, the gallery forests of the south are among the most endangered. Tamarind trees (Tamarindus indica) dominate these riverine forests and are a keystone food resource for ring-tailed lemurs (Lemur catta). At Berenty Reserve, the presence of tamarind trees is declining, and there is little recruitment of young trees. Because mature tamarinds inhibit growth under their crowns, seeds must be dispersed away from adult trees if tree recruitment is to occur. Ring-tailed lemurs are likely seed dispersers; however, because they spend much of their feeding, siesta, and sleeping time in tamarinds, they may defecate a majority of the tamarind seeds under tamarind trees. To determine whether they disperse tamarind seeds away from overhanging tamarind tree crowns, we observed two troops for 10 days each, noted the locations of feeding and defecation, and collected seeds from feces and fruit for germination. We also collected additional data on tamarind seedling recruitment under natural conditions, in which seedling germination was abundant after extensive rain, including under the canopy. However, seedling survival to 1 year was lower when growing under mature tamarind tree crowns than when growing away from an overhanging crown. Despite low fruit abundance averaging two fruits/m3 in tamarind crowns, lemurs fed on tamarind fruit for 32% of their feeding samples. Daily path lengths averaged 1,266 m, and lemurs deposited seeds throughout their ranges. Fifty-eight percent of the 417 recorded lemur defecations were on the ground away from overhanging tamarind tree crowns. Tamarind seeds collected from both fruit and feces germinated. Because lemurs deposited viable seeds on the ground away from overhanging mature tamarind tree crowns, we conclude that ring-tailed lemurs provide tamarind tree seed dispersal services.

The Frankincense tree Boswellia papyrifera is an important resource in the semiarid lower highlands of eastern Africa but its populations are declining due to human pressure and environmental degradation. To assess the perspectives of (assisted) natural regeneration for Boswellia woodland restoration, we examined Boswellia stand structure and seedling densities in a grazed woodland and in a livestock grazing exclosure. We also tested topsoil scarification as a means to increase seedling survival.Boswellia populations lacked small diameters, indicating recruitment limitation. During the rainy season, seedling densities were 8331 ha−1 in the exclosure and 3325 ha−1 in the grazed woodland. Respectively, 19% and 11% of these seedlings survived the first dry season. However, the lack of saplings suggests a lack of surviving seedlings over successive dry seasons and thus a cumulative seedling mortality approximating 100% within each generation. Topsoil scarification had an adverse effect on seedling survival.Dry season seedling mortality seriously limits the potential of natural Boswellia woodland recovery. To restore a healthy population structure in exclosures, additional management interventions such as shading to support early seedling survival or planting of large rooted cuttings need to be tested.

Terminalia oblonga (Ruiz et Pav.) Steud. is a common timber tree in lowland Latin America which is widely utilized and economically and ecologically valuable. The species suffers from reduced natural recruitment but the control of regeneration by environmental factors is incompletely understood. In the forest management plots of the BOLFOR project (La Chonta, Bolivia) we investigated the effects of soil disturbance, litter layer and canopy openness on seedling emergence and survival. Soil disturbance and a thin litter layer favoured seedling emergence, disturbance had also a positive effect on seedling survival, whereas canopy openness had no significant effect on emergence but influenced survival positively. The results are discussed with respect to the life history traits of T. oblonga and forest regeneration, which need to be considered for implementation of sustainable logging strategies and forest conservation. It is concluded that the regeneration of T. oblonga is favoured by moderate logging although the long-term effects need further research.

High-density herbivore species often play an important role in forest regeneration. Native sika deer (Cervus nippon yakushimae) inhabit a high density (51.5–63.8 head/km2, estimated by a pellet count method) area in the western part of a lowland natural forest on Yakushima Island, Japan. To test experimentally the impact of sika deer on the mortality and the survivability of current-year seedlings, which are at a more vulnerable stage than the later stages, we constructed fenced exclosures, planted seeds of nine sapfruit tree species and compared the mortality and the survivability of current-year seedlings between fenced and unfenced quadrats. Large seeded species had significantly greater survivability in fenced quadrats than in unfenced quadrats. However, the survivability disagreed with feeding preferences. Sika deer activity increased seedling mortality of large-seeded species more than that of small-seeded species, and did not decrease much seedling survivability of not-preferred species. We found that the physical disturbance by the high density of sika deer resulted in mortality for both preferred and not-preferred species, and that deer herbivory was important for preferred species.