Milton Kanashiro

Impact of selective logging on inbreeding and gene dispersal in an Amazonian tree population of Carapa guianensis Aubl .

Selective logging may impact patterns of genetic diversity within populations of harvested forest tree species by increasing distances separating conspecific trees, and modifying physical and biotic features of the forest habitat. We measured levels of gene diversity, inbreeding, pollen dispersal and spatial genetic structure (SGS) of an Amazonian insect‐pollinated Carapa guianensis population before and after commercial selective logging. Similar levels of gene diversity and allelic richness were found before and after logging in both the adult and the seed generations. Pre‐ and post‐harvest outcrossing rates were high, and not significantly different from one another. We found no significant levels of biparental inbreeding either before or after logging. Low levels of pollen pool differentiation were found, and the pre‐ vs. post‐harvest difference was not significant. Pollen dispersal distance estimates averaged between 75 m and 265 m before logging, and between 76 m and 268 m after logging, depending on the value of tree density and the dispersal model used. There were weak and similar levels of differentiation of allele frequencies in the adults and in the pollen pool, before and after logging occurred, as well as weak and similar pre‐ and post‐harvest levels of SGS among adult trees. The large neighbourhood sizes estimated suggest high historical levels of gene flow. Overall our results indicate that there is no clear short‐term genetic impact of selective logging on this population of C. guianensis.

Response of secondary vegetation in Eastern Amazonia to relaxed nutrient availability constraints

This study evaluated the effect of nutrient application on the regrowth dynamics of secondary fallow vegetation in an intensely exploited shifting cultivation area in the eastern Amazon region of Brazil. The importance of N, P, K, Ca, Mg, S and a mixture of micronutrients was tested in a minus-one-trial by comparison with a full complement of nutrients and unfertilized control plots. Fertilizers were applied three times during the experiment and their effects were monitored over a period of 2 1/2 years. Prior to the second fertilization, one third of each experimental plot was cleared of the vegetation cover and planted in maize, prior to the third fertilizer application these subplots were planted in sorghum. Biomass of maize and sorghum were used to indicate nutrient constraints and fertilizing effects due to the different treatments. Both crops were limited by P- and N-availability, with greater responses to P. The initial fertilization did not affect the biomass accumulation of the secondary vegetation during the first 15 months, but two additional applications significantly increased biomass in the complete fertilizer treatment compared to the unfertilized control. Biomass accumulation was primarily P-limited, N-limitation was apparent but not significant. The remaining nutrients did not affect plant growth. Fertilization favored production of nutrient-rich leaves. Application of readily available nutrients gave grasses a competitive edge over slower reacting woody vegetation. Fertilization also caused significant shifts in the contribution of woody species to biomass accumulation, as could be demonstrated for two prominent pioneer tree species. Growth response to fertilization as well as the primary limiting nutrient varied among seven dominant species monitored in the secondary vegetation. We conclude that growth of tropical secondary vegetation can be nutrient limited and it might respond significantly to additional nutrients by increasing biomass production.

Rapid tree carbon stock recovery in managed Amazonian forests

While around 20% of the Amazonian forest has been cleared for pastures and agriculture, one fourth of the remaining forest is dedicated to wood production. Most of these production forests have been or will be selectively harvested for commercial timber, but recent studies show that even soon after logging, harvested stands retain much of their tree-biomass carbon and biodiversity. Comparing species richness of various animal taxa among logged and unlogged forests across the tropics, Burivalova et al. found that despite some variability among taxa, biodiversity loss was generally explained by logging intensity (the number of trees extracted). Here, we use a network of 79 permanent sample plots (376 ha total) located at 10 sites across the Amazon Basin to assess the main drivers of time-to-recovery of post-logging tree carbon (Table S1). Recovery time is of direct relevance to policies governing management practices (i.e., allowable volumes cut and cutting cycle lengths), and indirectly to forest-based climate change mitigation interventions.While around 20% of the Amazonian forest has been cleared for pastures and agriculture, one fourth of the remaining forest is dedicated to wood production [1] . Most of these production forests have been or will be selectively harvested for commercial timber, but recent studies show that even soon after logging, harvested stands retain much of their tree-biomass carbon and biodiversity [2,3] . Comparing species richness of various animal taxa among logged and unlogged forests across the tropics, Burivalova et al. [4] found that despite some variability among taxa, biodiversity loss was generally explained by logging intensity (the number of trees extracted). Here, we use a network of 79 permanent sample plots (376 ha total) located at 10 sites across the Amazon Basin [5] to assess the main drivers of time-to-recovery of post-logging tree carbon ( Table S1 ). Recovery time is of direct relevance to policies governing management practices (i.e., allowable volumes cut and cutting cycle lengths), and indirectly to forest-based climate change mitigation interventions.

Pollination biology in Jacaranda copaia (Aubl.) D. Don. (Bignoniaceae) at the "Floresta Nacional do Tapajós", Central Amazon, Brazil

Jacaranda copaia (Aubl.) D. Don e uma arvore pioneira distribuida por toda Amazonia brasileira, encontrada colonizando clareiras, areas alteradas e bordas de fragmentos florestais. O presente estudo investigou aspectos da biologia floral, sistema reprodutivo e polinizadores de J. copaia. O florescimento ocorre de agosto a novembro, durante o periodo de menor precipitacao pluviometrica, estendendo-se por ate quatro semanas por individuo e tres ou quatro meses para a populacao, caracterizando um padrao de floracao cornucopia. A frutificacao termina no inicio da estacao chuvosa, com a dispersao anemocorica das sementes aladas. A taxa de frutificacao natural foi de 1,06% (n = 6.932). As flores autopolinizadas manualmente (n = 2.099) nao produziram frutos. A polinizacao cruzada (n = 2.524) resultou em 6,54% frutos, representando seis vezes mais do que a polinizacao natural (1,06%, n = 6.932). As flores protegidas da visita de polinizadores (autopolinizacao espontânea) nao formaram frutos (n = 5.372). O crescimento dos tubos polinicos foi detectado sob microscopia de fluorescencia tanto nos pistilos autopolinizados quanto nos submetidos a polinizacao cruzada. A especie foi considerada alogama obrigatoria, com mecanismo de auto-incompatibilidade de acao tardia. Aproximadamente 40 especies de abelhas nativas visitaram as flores, entretanto os polinizadores legitimos foram principalmente abelhas solitarias de medio porte dos generos Euglossa e Centris, em funcao da compatibilidade entre o tamanho corporal com o tubo da corola, que facilitava o contato direto com as estruturas reprodutivas, e a elevada frequencia de visitas.

Mating system and genetic diversity of progenies before and after logging: a case study of Bagassa guianensis (Moraceae), a low-density dioecious tree of the Amazonian forest

The logging of large trees in tropical forests causes a decrease in the density of reproductive individuals, which likely affects the pattern of pollen dispersal and the mating system of the remaining trees in the population. Here, we investigate the impact of logging on mating system and genetic diversity of the low-density, thrip-pollinated, dioecious tree Bagassa guianensis within a 500-ha plot at Tapajós National Forest, Pará State, Brazil. Mating system parameters of the logged population were estimated using mixed-mating model. Six microsatellite loci were used to genotype 232 seeds from ten remnant female trees over three seasons (2006, 2007, and 2008). The data were compared with the mating system of the unlogged population of B. guianensis (18 female trees, 488 seeds) in the same plot. The overall number of alleles found in the open-pollinated progenies decreased after logging (K = 71 before logging and K = 57 after logging, considering the three after logging seasons pooled), as well as the average number of alleles per locus (A = 11.8 and 9.5, respectively). Similarly, the number of private alleles, which is defined in the context of this study as the number of alleles observed in the population exclusively before or after logging, also decreased after logging (15 and 1, respectively). However, the average number of alleles per locus and the observed and expected heterozygosities were not significantly higher before logging than after logging. Logging also did not affect the inbreeding of progenies in the population. Somewhat unexpectedly, the effective number of pollen donors was consistently higher after (Nep = 14.5 in 2006, 8.1 in 2007, and 6.3 in 2008) than before logging (Nep = 3.4), suggesting that the loss of alleles in the population was compensated by the higher heterogeneity in the pollen pool after the removal of the largest trees by logging. Potential causes explaining the patterns found here include the maintenance of large patches of forest around the logged plot and the species’ ability to perform long-distance pollination by airborne thrips. Maintenance of landscape integrity as logged and unlogged forests around the exploited areas is recommended to enhance pollen migration and to avoid long-term losses in genetic diversity.

Gérer les forêts dégradées, une nouvelle priorité en Amazonie brésilienne

En Amazonie bresilienne, les forets degradees dominent les paysages des fronts pionniers. Un grand defi attend desormais cette region : stopper la degradation et gerer durablement ces forets. Les forets degradees representent aujourd’hui une categorie de foret a part entiere. Elles peuvent neanmoins jouer un role majeur pour lutter contre le changement climatique. Elles peuvent aussi contribuer a un meilleur fonctionnement ecologique des territoires. Developper des politiques publiques visant le double objectif de reduire la degradation et de valoriser ces forets implique un appui fort de la recherche. Dans ce Perspective, nous mettons l’accent sur quatre priorites de recherche : developper des methodes de caracterisation et de suivi des forets degradees, elaborer des plans d’amenagement specifiques, comprendre le role joue par tous les acteurs sociaux et accompagner les politiques a l’echelle territoriale.