07_MadagascarRevisions_R4 3/7/08 3:38 PM Page 119 Chapter 3.3 Analyses of Seed Germination of Littoral Forest Native Species in Southeastern Madagascar Faly Randriatafika, Johny Rabenantoandro and Rivo A. Rajoharison Abstract reproductive ecology and propagation of numerous members of the local flora. Studying germination is Here we present data on the properties of seeds rele- an essential part of planning species rehabilitation vant to restoration activities. Seeds from pioneer and conservation work because it enhances propaga- species were most abundant from May to September. tion techniques. With this in mind, a nursery system Most seeds from non-pioneer species ripened during was established in 1999 to study the propagation of the hot wet season. More than half of the species numerous native plant species. The results of this have germination rates below 50%, but once germi- research are presented here. nated, no species had mortality rates higher than 30%. It is important to intensify studies to under- Methodology stand the causes of dormancy as this might help improve storage conditions and increase germination Seed collection rates for species with long dormancies. Seeds are defined as part of the organs that plants Résumé develop to ensure reproduction (Côme 1975). In the angiosperm spermatophyte, adult individuals often Analyse de la germination des semences des carry out this function. For propagation, seeds or espèces autochtones de la forêt littorale du sud- fruits should generally be collected between ripeness est de Madagascar. Nous présentons ici les données and the commencement of natural dissemination sur les propriétés des semences qui sont adaptées à la (Morandini 1962). Phenological results were used restauration écologique. Les semences des espèces for monitoring biodiversity and to assist in planning pionnières sont plus abondantes entre les mois de future ecological rehabilitation work. mai et de septembre. Les semences des espèces non The seeds were generally collected during the pionnières arrivent généralement à maturité au cours fruit maturation period, which was identified before- de la saison chaude et humide. Plus de 50% des hand based on a detailed phenological dataset of the espèces ont des taux de germination inférieurs à Tolagnaro region littoral forest plants (Bollen 2003). 50%. Après germination, aucune espèce ne montre The collection methodology is based on norms and un taux de mortalité supérieur à 30%. Les graines standards established by Kew Garden, Millennium restent dormantes à divers degrés. Il est important Seed Bank (2001). The seeds were either gathered d’intensifier les études pour comprendre les causes off the ground or collected directly from the plant. de la dormance dans la mesure où cela permettrait The following information was recorded for each d’améliorer les conditions de stockage et d’aug- collection: date, scientific name (genus and species), menter les taux de germination pour les espèces sampling method, plant description, characteristics présentant des semences à dormance prolongée. (pioneering, intermediate, or climax species), habi- tat, and uses. A collection sheet was filled-out for Introduction QIT Madagascar Minerals, BP 225, Tolagnaro 614, Madagascar. Email: [email protected], Following the initial plant inventories of the littoral [email protected], and forests of the Tolagnaro region conducted by the [email protected] Missouri Botanical Garden (Lowry and Faber- Langendoen 1991), a major gap still remained in the SI/MAB Series 11 ■ 119 07_MadagascarRevisions_R4 3/7/08 3:38 PM Page 120 each specimen and each seed lot was given an indi- Germination vidual number, which was used for all nursery oper- ations (from collection to stock to germination). The nursery was designed for seed germination analysis and, above all, to produce plants for ecolog- Seed treatment and conservation ical rehabilitation. The technique consists of sowing previously treated and sorted seeds directly in plastic According to Ewart (1908), seeds are classified into pots filled with topsoil. Several parameters were one of three different groups based on their viability considered and monitored during the experiments, or longevity: macrobiotic seeds that remain viable the most important are: 1) Emergence (E), which is for more than 15 years, mesobiotic seeds that remain defined as the number of days between the seeding viable between 3 and 15 years, and microbiotic seeds date and the initial germination emergence; 2) that are only viable up to 3 years. The classification Germination rate (GR), using the formula GR = n/N most often used to describe seed types was formulat- x 100 (where n = number of germinated seeds and N ed by Roberts (1973) and includes orthodox seeds, = Number of seeds planted); and 3) Mortality rate which can withstand natural or artificial desiccation (MR), using the formula MR = m/N x 100 (where m (water content of 4 - 6%) or consistently low temper- = number of dead seeds). atures over an extended period, and recalcitrant seeds that are difficult to keep over the long term, but which can be conserved if their specific characteris- tics are known. In order to categorize littoral forest species behavior, we consulted the scientific literature including numerous works published by the Kew Garden. However, certain aspects of the germina- tion ecology of several plant species occurring in the Tolagnaro littoral forests were still unknown. In Number of Species order to advance in understanding the different seed types of the local flora, a series of tests were Month conducted. These employed a progressive desicca- tion method which placed the seeds in a hermeti- cally sealed container with silica gel until the rela- tive humidity (RH) was under 15%. The species that managed to germinate at this level of humidi- ty were defined as being orthodox and those that did not as recalcitrant. Treatment of seeds consisted of separating the seed from the fruit or from other parts, and cleaning Number of Species the seed. The seeds were treated based on their type of fruit: fleshy stone or bay fruits were pulped and cleaned using different-sized screens, and the dried Month fruits were cleaned and sorted. The previously cleaned seeds were then spread out on a grass mat, Figure 1. Monthly variation in seed collection of sheltered from the sun, and divided into two lots: 1) non-pioneering (A) and pioneering (B) species. planted directly at the Mandena nursery to analyze germination and produce plants, and 2) used for the Results behavior test (i.e. orthodox or recalcitrant character) and for long-term conservation in a seed bank. The Seed collection orthodox seeds obtained from the analysis were sent to the KEW Millennium Seed Bank (MSB) and to the Between 1998 and 2004, 119 species were studied Antananarivo Silo National des Graines Forestières (Table 1). Figure 1a illustrates the monthly variation in (SNGF) for long-term ex-situ conservation. seed availability of non-pioneer species. It shows that 120 ■ Biodiversity, Ecology and Conservation of Littoral Ecosystems in Southeastern Madagascar, Tolagnaro 07_MadagascarRevisions_R4 3/7/08 3:38 PM Page 121 stocks of seeds are available year round in the forest. to the general fructification trend of seeds from non- However, most seed-producing species are much more pioneering species. abundant in January and February, and then decrease The presence of seeds is positively correlated to until September when they flower. Moreover, Figure monthly rainfall (Spearman correlation: rs = 0.88, p < 1b shows the monthly variation in seed collection for 0.001, n = 12). The presence of seeds from pioneering pioneering species. The trend in the fructification peri- species is negatively correlated to the mean ambient ods of most pioneering species is inversely correlated temperatures (rs = 0.88, p < 0.001, n = 12; Figs. 2a, b). Number of Species Number of Species Figure 2. Correlation between non-pioneer species and monthly rainfall (A) and between pioneer species and mean, monthly temperatures (B). Number of Species Number of Species Number of Species Figure 3. Germination tests showing (A) species distribution by germination rate, (B) relation between germination rate and type of fruit, (C) species distribution by emergence in days, and (D) percent of species distribution by mortality rate. SI/MAB Series 11 ■ 121 07_MadagascarRevisions_R4 3/7/08 3:38 PM Page 122 Conservation test the seed production of non-pioneering species and monthly temperature. Among the 114 plants tested and documented, 50 • Dormant or inhibited species require more species are presumed orthodox, 19 recalcitrant, and in-depth research to determine the type of 45 intermediate. dormancy or inhibition (embryonic dormancy or tegument inhibition). Germination • There may be many causes for the low germination rates. These include external factors For all plants treated at the nursery, we were able to such as high relative humidity and temperatures in distinguish between the easily germinating species the study area. These factors may influence seed and those requiring special treatment. These analyses quality and viability. are presented separately for germination rate and types of fruits (Figs. 3a, b), germination emergence In our collection of seeds from the littoral forests (Fig. 3c), and mortality rate (Fig. 3d). Over 50% of of southeastern Madagascar and studies of their species have an average germination rate below development, we found considerable variation in 50%. Stone fruits have a higher germination rate their life-history traits with regard to germination (Fig. 3b). Delayed germination may be due to seed ecology. There is a need to identify other aspects of dormancy and inhibition phenomena. Nevertheless, the germination of these plants, for example dor- over 72% of seeds were able to germinate in less mancy phenomena, to help further advance ecologi- than two months. Over 60% of species have mortal- cal restoration and plantations. These studies are also ity rates below 5%, and no species mortality exceeds an effective means for advancing ex-situ conserva- 30% (Fig.