A Comparative Study of Two Tropical Pioneer Species with Different Lifespan under Different Light and Nutrient Conditions

We compared the contents of nitrogen,phosphorus and carbohydrates in seedlings of a short-lived pioneer species,Trema tomentosa,and a long-lived pioneer species,Macaranga denticulata,by an experiment of two light levels(4% and 20% of full sunlight) and two nutrient levels(low and high).Some morphological traits and biomass allocation patterns of the two species were also examined.The results showed that:(1) The nutrient concentrations of the two species increased with the increasing of light and nutrient availabilities,T.tomentosa exhibited higher concentrations of nitrogen and phosphorus in leaves and fine roots than M.denticulata.(2) The concentrations of starch and total non-structure carbohydrate(TNC) in seedlings of T.tomentosa were lower than in those of M.denticulata when grown in high light while the opposite was true when in low light treatments.(3) For two species,most soluble sugar stored in leaves while most starch and TNC stored in roots and starch is the most major component of non-structure carbohydrates.(4) The seedlings of T.tomentosa had higher root mass ratio,root crown mass ratio,fine root mass ratio,leaf area ratio,specific leaf area,specific fine root length,specific fine root surface area and thinner fine root diameter than M.denticulata.In conclusion,compared with the long-loved pioneer M.denticulata,the short-lived pioneer,T.tomentosa,had higher tissue nutrient contents,lower tissue non-structure carbohydrate concentrations,favorable allocation patterns and morphological traits,which facilitate the resource capture and consequently contribute to the dominance in the early stage of secondary succession.