High Tree Diversity Research Articles

Spacing Dynamics of a Tropical Rain Forest Tree: Evaluation of the Janzen-Connell Model

As a partial explanation for the maintenance of high tree diversity in wet tropical forests, Janzen (1970) and Connell (1971) independently hypothesized that natural enemies act to increase spacing within these tree populations through disproportionately high attack on progeny near adults. Both authors also hypothesized a minimum critical distance effect, because of 100% progeny mortality within a given distance of adults. We describe the necessary and sufficient conditions for testing these hypotheses, and show that attempts to evaluate them have been hampered by use of the inappropriate standard of regular spacing. Data describing the spacing dynamics of Dipteryx panamensis, a rain forest canopy tree, support both hypotheses. From 7 mo to 2 yr postgermination, seedling survival was positively correlated with distance to adult and negatively correlated with local conspecific seedling density. Partial correlation was used to separate the effects of density and distance, and it was shown that seedling density was the only significant factor in this case. Older juveniles and saplings occurred at greater distances from the nearest conspecific adult than did 1980 seedlings. No seedlings or juveniles survived within 8 m of an adult bole. A review of 24 data sets on tropical woody plants showed that most evidence indicates either density-dependence or distance-dependence in progeny mortality, as hypothesized by Janzen and Connell. Some positive evidence also exists for the minimum critical distance effect for tropical trees. In most of the cases involving seedling mortality, however, alternative causal factors such as intracohort competition or allelopathy were not ruled out. Before generalizations can be made about this process in tropical forests, carefully designed studies are needed on more populations of tropical trees.

Diversity in Tropical Rain Forests and Coral Reefs

The commonly observed high diversity of trees in tropical rain forests and corals on tropical reefs is a nonequilibrium state which, if not disturbed further, will progress toward a low-diversity equilibrium community. This may not happen if gradual changes in climate favor different species. If equilibrium is reached, a lesser degree of diversity may be sustained by niche diversification or by a compensatory mortality that favors inferior competitors. However, tropical forests and reefs are subject to severe disturbances often enough that equilibrium may never be attained.

The roles of community fruit garden (tembawang) on maintaining forest structure, diversity and standing biomass allocation: an alternative effort on reducing carbon emission

Astiani D, Ripin. 2016. The roles of community fruit garden (tembawang) on maintaining forest structure, diversity and standing biomass allocation: an alternative effort on reducing carbon emission. Biodiversitas 17: 359-365. Fruit garden (tembawang) Cempedak Village in Sanggau West Kalimantan has been established by local community for their family mixed garden ~ >100 years. The families of 3rd generation were utilizing the tembawang for their needs of building materials, fire woods, rattan, vegetables, fruits, and traditionals medicine. It is important to study how this tembawang play their roles in maintaing forest structure, species diversity and stocking biomass. In 2014, we studied this area for exploring the vegetation composition and their ability to stock biomass of the tembawang. Stratified Random Sampling was applied to the 6.69 ha tembawang area, which devided into three major land cover patches (Mixed fruit garden, mixed rubber plants, and fruit garden mixed with apik-Arenga undulatifolia Becc palm). We surveyed and sampled vegetation using transect methods purposively chosen on each landcover patch, with sampling area consecutively for mixed fruit garden, mixed rubber plants, and mixed of fruit garden and apik were 1.52, 0.6, and 0.72 hectars. Results demonstrated that mixed fruit garden carried out higher tree diversity, density, basal area, and maintained the largest above ground biomass per hectar compared to the two other patches. From 97 vegetation spesies registered, it maintained 49 tree species of diameter >20cm and 51 tree species in the lower strature in the forest structure. Interestingly, Durio zibethinus Murr. was a dominant species on all landcover patches types and sinked the largest above ground living biomass. The choice of fruit species on tembawang determined the capability of the embawang land to sequester and stock carbon in trees, because the trees were standing in tembawang for longer time compared to the one in production forest. This results show that, beside its multiple role for people community, tembawang provide other benefits to the nature in maintaining forest structure, diversity, and stocking large carbon in standing biomass.

Nutrients Leaching From Soils with Different Functional Diversity Fertilized With Straw and Manure: An Experimental Approach

Nutrients leaching from the agricultural soils is a major environmental concern worldwide. The risk of nutrients leaching in soils fertilized with straw and manure was tested in mesocosms experiments during seven months. The biotic community of the mesocosms was controlled to assure a different functional diversity for each kind of fertilizer. After rainy periods, mesocosms collected leacheate was chemically analyzed in order to determine the amount of NO3-, NH4+, PO43-, K+. The outcomes have underlined the great leaching capacity of the nitrate (NO3-). The highest NO3- total amount recorded was of 1170 ppm while the smallest was of 641 ppm. Leaching capacity of the other nutrients, is more reduced compared with nitrate. The levigation capacity inreased in order K+> PO43-> NH4+. The results indicated also that the nutrients leaching is significantly greater for manure treatments than that of straw treatments. The greatest loss of nutrients was observed in high biological diversity treatments.