Role of seed sowing time and microclimate on germination and seedling establishment of Dodonaea viscosa (Sapindaceae) in a seasonal dry tropical environment - an insight into restoration efforts

Reintroduction of plants in a tropical forest is imperative not only to maintain remnant forests, but also to preserve the extant flora against global warming and other induced effects. The importance of seed sowing time and microclimate on seed germination and seedling establishment of Dodonaea viscosa Jacq. were investigated in Tamil Nadu, India, to provide information to assure the successful reintroduction of this species. A field experiment was conducted by sowing seeds (whose dormancy had been broken by hot water) in a natural environment at a depth of 3 cm in three microsites (artificially shaded, naturally shaded, and open) in February and August 2011. Seedling survival was monitored for 2 years at 6 month intervals under natural conditions. Soil temperature and light availability were measured. Soil temperature was moderate in shaded regions but light availability was low, and the opposite was true for the open site. Rainfall was a major trigger for stimulating germination. Seeds sown in August survived better after 2 years compared with those sown in February (p < 0.0001). Microsite significantly (p < 0.005) affected the total seedling survival with the percentage of successful seedlings established decreasing from the artificially shaded site to the open site. Seedling mortality in both groups mainly occurred during the dry summer season. The wet season benefited germination and seedling growth. We conclude that sowing seeds or planting seedlings of D. viscosa early in the wet season is beneficial to reintroduction success.