Evaluation of the Growth and Survival of Mangrove Seedlings Under Different Light Intensities: Simulating the Effect of Mangrove Deforestation

Abstract

Environmental factors, especially light, temperature, and edaphic conditions are of great importance for the establishment of plant communities. In areas degraded by deforestation, these factors can vary greatly, which may affect the recolonization of the typical populations in the altered area. This study evaluated the development of seedlings of pioneer mangrove species under different levels of shading in soil substrate degraded by deforestation, aiming to assess the effect of deforestation on the recolonization of mangrove forests, which may be of help in the production of seedlings and recovery of deforested areas. The study was conducted in the municipality of Acaraú in the state of Ceará, Brazil. The species Avicennia schaueriana Stapf and Leechm. ex Moldenke (1939) and Laguncularia racemosa C. F. Gaertn (1807) were used in the study, and the substrate was collected from an area impacted by deforestation. The propagules and seedlings were exposed to full sun and 30, 50 and 70% shading. The results revealed that the treatment at full sun had the lowest germination rate of 86.66% for L. racemosa. Seedlings of both species showed a significant difference and better quality between shading treatments and full sun. The height of the seedlings showed a correlation above -0.90 with ambient temperature. L. racemosa tested in full sun had a viable seedling reduction of 50% and A. schaueriana was superior. It is concluded that the natural regeneration of a mangrove area can be compromised under the conditions of total deforestation with high sun exposure and degraded soils. Human intervention in providing 50% shading is essential for the development of seedlings and regeneration of the area impacted by deforestation.

EFFECTS OF ALTITUDE ON SEEDS GERMINATION AND LUMINOSITY LEVELS ON THE VEGETATIVE DEVELOPMENT OF Schinus terebinthifolius Raddi

“…Such results support the findings of Souza et al (2013) and Neves et al (2016) regarding the adaptative capacity of S. terebinthifolius to different environments. Nevertheless, Silva & Maia (2019) verified that some pioneer species of the mangrove are not well-developed under full sunlight. The authors report that in deforestation conditions the human intervention is essential for regeneration, providing a 50% shading to obtain stability for seedlings.…”

“…Finally, the discrepancy found between the germination test and the vegetative development of S. terebinthifolius based on seed batches collected in sites with the same altitude reveals that the result might have been influenced by variables not considered in this study, such as seeds' genetic load. In this context, Silva et al (2019) state that intrinsic genetic characteristics may difficult the obtention of forest species' seeds with maximal germination and vigor. Thus, accelerated aging and electrical conductivity tests are recommended to confirm seeds' vigor, identifying if the batch is viable and vigorous (SILVA et al, 2019).…”

“…In this context, Silva et al (2019) state that intrinsic genetic characteristics may difficult the obtention of forest species' seeds with maximal germination and vigor. Thus, accelerated aging and electrical conductivity tests are recommended to confirm seeds' vigor, identifying if the batch is viable and vigorous (SILVA et al, 2019).…”

Multidisciplinary assessment of a restored mangrove ecosystem in Guanabara Bay, Brazil: Linking science and conservation

“…Additionally, the limited number of adult A. schaueriana suggests insu cient propagule production for effective recolonization. Therefore, our results suggest that A. schaueriana populations in the PNMBM will likely require reinforcement through the production and planting of additional seedlings, particularly in areas with denser canopies exceeding 30% light penetration (Silva and Maia 2019). Management strategies to mitigate crab predation should also be considered.…”

Recruitment and mortality of Rhizophora mangle L. seedlings in the Tropical Southwestern Atlantic mangrove

“…Those variables were also evaluated in studies with other mangrove species in controlled conditions (mesocosm experiments) (Balke et al, 2013;Gillis et al, 2019;Silva and Maia, 2019;van Hespen et al, 2022) and in field situations (Ewel and Baldwin, 2022;Sinsin et al, 2022;Sloey et al, 2022). Despite these studies, there are gaps in knowledge about the relationship between recruitment dynamics and seedling mortality.…”