Soil Conditioning and Neighbor Identity Influence on Cycas Seedling Performance

Abstract

Translocation of endangered plant species and facilitating in situ regeneration require knowledge of the factors that define suitable habitat characteristics. Four approaches were employed to define how antecedent and contemporary plant identity influenced Cycas seedling growth and survival in Guam, Yap, and the Philippines. Cycas micronesica K.D. Hill or Cycas nitida K.D. Hill & A. Lindstr. seedlings growing beneath the canopy of the maternal parent tree reached 100% mortality in 4 to 8 year. Cycas micronesica seedlings planted beneath a conspecific male adult tree reached 68% mortality in two years while seedlings planted away from a conspecific individual exhibited 100% survival. Cycas micronesica seedlings planted beneath monostands of invasive Leucaena leucocephala (Lam.) de Wit or Vitex parviflora Juss. reached 40% mortality in two years while seedlings planted in adjacent native forest cover exhibited 100% survival. Cycas micronesica seedlings planted in soil conditioned for 9 months by conspecifics, heterospecific native species, Carica papaya L., L. leucocephala, or V. parviflora exhibited the greatest growth in the soils conditioned by heterospecific natives and the least growth in the soils conditioned by the three invasive species. The seedlings growing in soil conditioned by conspecifics exhibited the most coralloid roots and the greatest shoot:root ratio. These studies confirmed that the identity of antecedent and competitive plants strongly influenced the longevity and growth of Cycas seedlings. Conservationists may improve outcomes by avoiding degraded forests that have experienced invasive plant species when positioning translocation projects. Planting Cycas seedlings in biodiverse native forest but away from a conspecific individual may lead to the greatest success in population recovery.