The present study investigated the growth and survival of seedlings of Rhizophora , Avicennia , and Laguncularia raised in three different substrates: mangrove soil, latosol, and sand. The study was based on an entirely random factorial design (3 × 3) × 3, with three tree species, three substrates, and three replicates. The experiment was conducted in a nursery installed in the municipality of Braganca, in the northern Brazilian state of Pará. The seedlings were grown in 17 cm × 27 cm polyethylene containers. Survival was calculated based on the percentage of germinated propagules surviving after 270 days. Seedling heights were evaluated using an analysis of variance (ANOVA) and morphological parameters were compared using Tukey’s test. All three species were ready for replanting after 270 days. The R. mangle and A. germinans seedlings presented better rates of survival and growth on the substrates tested. All three species grew well in the substrates tested, and the production of seedlings in yellow latosol would appear to be t he most effective approach.
Worldwide, mangrove forests cover a total area of approximately 152,000 km2 [
A number of authors believe that unmanaged logging in mangrove forests may cause considerable alterations to the composition of these ecosystems or even their total elimination from some areas [
Despite these impacts, there have been a number of initiatives for the recuperation of mangrove forests in many areas around the Brazilian coast [
The development of adequate technologies for the production of the seedlings of native plants, including seed germination, seedling management, and the type of substrate used, is essential for the recuperation of degraded ecosystems [
One other important consideration for the production of seedlings is the cost of production, which is considerable when compared with direct sowing. In conclusion, nurseries are only necessary when regeneration is unsuccessful by direct sowing, or when a certain degree of seedling development is necessary to guarantee recruitment [
The region’s growing human population has been the primary factor determining the ongoing degradation of the mangrove forests of the Brazilian Amazon region [
The present study was developed in the village of Taperaçu-Campo (00˚56'55.07''S, 46˚46'00.82''W), on the Ajuruteua Peninsula, 12 km north of the town of Bragança, in the northern Brazilian state of Pará (
Four of the seven mangrove tree species found in the Neotropical region are present on the Ajuruteua Peninsula, although only three of these species―R. mangle, A. germinans, and L. racemosa―dominate the landscape, while Avicennia schaueriana Stapf and Leechman ex Moldenke is more sparsely distributed. It is important to note that the construction in the 1970s of the PA-458 state highway, which connects Bragança to the village of Ajuruteua, bisected 26 km of the local mangrove forest [
The nursery was established near a tidal creek, where a small ditch was dug to provide a water source, imitating a daily regime of inundation by tidal waters. The nursery occupied a total area of 32 m2 (8 m × 4 m, with a depth of 40 cm), and was placed in the intertidal zone, where they have access to brackish water [
Peak fruiting in the mangrove tree species of the Amazon region corresponds to the rainy season [
The A. germinans propagules were immersed in water for 24 hours in order to facilitate the removal of the tegument, while those of L. racemosa were immersed for approximately seven days, until the radicle emerged. The R. mangle propagules were not treated in any way.
The propagules were planted in 17 cm × 27 cm polyethylene containers filled with one of three types of substrate―(i) mangrove soil, (ii) latosol, and (iii) sand. An average of four propagules were planted directly into the substrate of each container in order to compensate for losses, and guarantee the production of at least one seedling per container. Surplus seedlings were removed after 30 days, leaving only the best-developed seedling in each container.
The seedlings selected for the three mangrove species were tested in relation to the effects of substrates on their survival and growth. The experimental design adopted for the present study was completely randomized, based on a 3 × 3 factorial (3 species × 3 types of substrate). Each treatment included three replicates, each composed of 80 seedlings (total = 240), and nine treatments were evaluated. Each of the different substrates tested in the present study were analyzed chemically in the EMBRAPA (Brazilian Agricultural Research Corporation for eastern Amazonia) soils laboratory in Belém, Brazil. For this, samples of 1 kg were obtained from a depth of 20 cm and stored in plastic bags labeled according to their origin.
Seedling survival rates were calculated based on the percentage of containers with seedlings 270 days after planting. For the assessment of growth, the height (cm) of the seedlings was first measured 30 days after planting, and then every month over the nine months of the study period.
The data were analyzed using standard statistical tests [
A good quality substrate, in both chemical and physical terms, is essential for the production of healthy seedlings of native forest species [
In the mangrove soil, the survival rates recorded for A. germinans (98%) and R. mangle (90%) were higher than those observed for the sandy substrate (85% for both species). These findings contrast with those of Abrahão [
With the exception of Al and Zn, the highest values for the different nutrients analyzed were recorded in the mangrove soil (
In mangrove soil (
In the sandy substrate (
In the latosol (
Component | Quantity found in: | ||
---|---|---|---|
Mangrove soil | Sand | Latosol | |
Coarse sand (g/kg) | 8 | 1 | 17 |
Fine sand (g/kg) | 571 | 979 | 762 |
Silt (g/kg) | 182 | 0 | 121 |
Total Clay (g/kg) | 240 | 20 | 100 |
pH | 6.0 | 4.7 | 5.0 |
P (mg/dm3) | 16.0 | 8.0 | 3.0 |
K (mg/dm3) | 583 | 57 | 24 |
Na (mg/dm3) | 388 | 609 | 12 |
Ca (cmol/dm3) | 1.9 | 0.9 | 0.4 |
Ca + Mg (cmol/dm3) | 8.2 | 1.6 | 0.7 |
Al (cmol/dm3) | 0.1 | 0.1 | 1.4 |
Cu (mg/kg) | 7.1 | 4.3 | 5.2 |
Mn (mg/kg) | 14.8 | 12.8 | 14.6 |
Fe (mg/kg) | 136.0 | 555.0 | 135.6 |
Extractor method. EMBRAPA-Belém.
Source of variation | (Rh ± SD) × (Av ± SD) × (La ± SD) | MS | F | p |
---|---|---|---|---|
spp. × mangrove soil | (69.1 ± 05.99) × (77.7 ± 01.77) × (54.9 ± 08.76) | 0.13 | 30.75 | 0.001 |
spp. × sand | (67.1 ± 06.61) × (70.2 ± 03.58) × (35.5 ± 14.86) | 0.36 | 35.79 | 0.001 |
spp. × latosol | (66.6 ± 06.96) × (44.4 ± 12.08) × (41.2 ± 13.14) | 0.19 | 13.73 | 0.01 |
rates observed in plots established within the forest. While a marked difference was recorded for R. mangle―93% in the nursery versus only 10% in the forest―similar survival rates were recorded for C. erectus and A. germinans in the two environments.
The survival of mangrove trees depends on a range of environmental factors. In a mangrove forest in Espírito Santo, Brazil, for example, mortality rates in R. mangle seedlings were determined by a combination of environmental factors and inter-individual competition, whereas in L. racemosa was affected only by competition. In this case, while the population density of L. racemosa was lower, this species appeared to be better adapted to the local abiotic conditions [
A number of biological processes may also affect the survival strategies of seedlings in mangrove forests, however. Unlike R. mangle and A. germinans, for example, L. racemosa is not viviparous, and germination often occurs during the dispersal process [
It is important to note that the production of seedlings for the recuperation of degraded mangroves may result in increased survival and better development of the plants than those already present in the natural environment. Similar results were obtained in a more arid region [
The results of the ANOVA for seeding growth (
Overall, then, the results of the present study indicated that an adequate chemical and physical composition of the substrate is essential for the rapid growth and development of the seedling of mangrove tree species (R. mangle, A. germinans, and L. racemosa). It is important to remember, however, that the propagules of these species are able to develop independently of the substrate tested. In fact, the propagules of these species retain sufficient reserves of nutrients in order to guarantee the establishment of their cotelydons, even after nine months. During the initial growth period, the cotelydons are fundamentally important for the absorption of resources prior to germination, and even after this process, when they emerge from the tegument of the seed to initiate photosynthesis [
The results of the present study indicate that the seedlings of R. mangle and A. germinans survived at higher
Source of variation | (Rh ± SD) × (Av ± SD) × (La ± SD) | MS | F | p |
---|---|---|---|---|
spp. × mangrove soil | (36.32 ± 16.85) × (39.35 ± 11.74) × (35.82 ± 16.45) | 41.23 | 0.17 | 0.83 |
spp. × sand | (36.10 ± 16.67) × (34.04 ± 10.33) × (32.82 ± 16.45) | 34.89 | 0.15 | 0.85 |
spp. × latosol | (36.06 ± 16.63) × (32.29 ± 12.24) × (32.62 ± 14.62) | 27.37 | 0.11 | 0.89 |
rates on the substrates tested in the nursery than L. racemosa. However, all three species grew well in the substrates tested, and the production of seedlings in yellow latosol would appear to be the most effective approach, considering the availability of this material on the Amazon coast and its ease of use, as well as the potential avoidance of further intervention into the mangrove ecosystem.
Rejane Silva Costa,Erneida Coelho de Araujo,Elaine Cristina Lopes de Aguiar,Marcus Emanuel Barroncas Fernandes,Rogerio Figueiredo Daher, (2016) Survival and Growth of Mangrove Tree Seedlings in Different Types of Substrate on the Ajuruteua Peninsula on the Amazon Coast of Brazil. Open Access Library Journal,03,1-9. doi: 10.4236/oalib.1102777