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FAPEAM - Funda????o de Amparo ?? Pesquisa do Estado do Amazonas

Urbanization, as well as environmental changes related to it, creates both new restrictions and opportunities for plants that remain in forest patches segregated by the urban matrix. In order to shed some light on the resulting effects of this process, this study explored the impact of antropogenic disturbance on the floristic and phenology of tree communities in the fragmented landscape of Manaus city, Amazonas state, Brazilian Amazonia. Four areas were selected for floristic survey and phenological monitoring: Adolpho Ducke forest reserve (RFAD), Acariquara and Coroado forests, both located in the campus of the Federal University of Amazonas, and the forest fragmented owned by the Brazilian Industry Social Service (SESI). These areas reflect a gradient of rising antropic disturbance: RFAD ??? Acariquara ??? Coroado ??? SESI. Floristic surveys were carried out on 10 x 250m plots, totalizing one hectare for each study area, and all plants with DBH >= 5cm were marked. Phenological observations were made or seven years, and the occurrence of phenophases (i.e. flowering, fruiting, leaf flushing and leaf fall) in each marked plant were recorded throughout that time. Climate data from Manaus (i.e. cumulative rainfall, air relative humidity and average temperature) were obtained monthly, their relations to community-level phonological patterns were investigated by means of generalized linear models (GLM). Direct gradient analysis revealed that floristic composition strongly varies between areas. RFAD, Acariquara and Coroado have family assemblages progressively less inclusive, in this order; SESI has a predominantly dissimilar flora in relation to the others. Pair-wise comparisons between areas with Jaccard???s dissimilarity indices confirmed this result at the level of species. Besides, species number declined as a function of greater antropization. In all study areas, the greatest number of flowering individuals occurred between the end of the dry season and the beginning of the wet season; the greatest number of fruiting individuals coincided with the wet season. Peaks of leaf flushing and leaf fall occurred during the dry season in all areas. Environmental variables explained relatively little of the observed variation in each of the phenophases. In general, phenological correspondence between areas was greater for vegetative phenophases; association between reproductive phenophases in different areas was highly variable. Both positive and negative relations were found between cumulative rainfall and the number of trees in each phenophase, whereas only positive relations were observed with the number of fruiting trees. In general, average temperature had positive effects on the expression of all phenophases, but air relative humidity has both positive and negative effects on the number of trees with new leaves, flowers and fruits; only positive effects were found on leaf fall. Besides, fruiting was mainly determined by flowering in earlier months. These discrepant results are accord with previous suggestions that adaptive mechanisms of tropical trees should render them weakly responsive to climate. Factors such as genetic constitution, physiological state, demography and ecological interactions may take part in the remaining, unexplained phonological variation. It is suggested that future studies should integrate the contributions of both abiotic and biotic factors to the regulation of tree community phenology. The understanding of plant phenology in tropical environments under rising antropization in fundamental for the adequate conservation and management of ecological functions in urban forest remnants.

O fen??meno da urbaniza????o, bem como as modifica????es ambientais a ele associadas, criam novas restri????es e oportunidades para as plantas que permanecem em remanescentes florestais segregados pela matriz urbana. A fim de clarificar os efeitos resultantes deste processo, este estudo explorou o impacto da perturba????o antropog??nica sobre a flor??stica e a fenologia de comunidades arb??reas na paisagem fragmentada da cidade de Manaus, AM. Quatro ??reas foram selecionadas para levantamentos flor??sticos e monitoramento fenol??gicos: a Reserva Florestal Adolpho Ducke (RFAD), as florestas do Acariquara e do Coroado, situadas no Campus da Universidade Federal do Amazonas, e o fragmento florestal do Clube dos Trabalhadores do Servi??o Social da Ind??stria (SESI). Estas ??reas refletem um gradiente crescente de perturba????o antr??pica, no sentido RFAD ??? Acariquara ??? Coroado ??? SESI. Os levantamentos flor??sticos abrangeram parcelas de 10 x 250 m, incluindo plantas com DAP >= 5 cm, num total de um hectare para cada ??rea de estudo. Os monitoramentos fenol??gicos abrangeram seis anos de observa????es sobre a ocorr??ncia de diferentes fenofases (i.e. flora????o, frutifica????o, produ????o de folhas, perda de folhas) em cada planta incluinda no levantamento flor??stico. Dados climatol??gicos da cidade de Manaus incluindo precipita????o acumulada, umidade relativa do ar e temperatura m??dia foram obtidos em uma base mensal, e suas poss??veis rela????es com o comportamento fenol??gico das comunidades foram investigadas atrav??s de modelos lineares generalizados (GLMs). Uma an??lise de gradiente direta revelou que a composi????o flor??stica em n??vel de fam??lia varia fortemente entre as ??reas. RFAD, Acariquara e Coroado possuem conjuntos taxon??micos progressivamente menos inclusivos, nesta ordem; SESI apresenta uma flora predominantemente distinta das demais ??reas. ??ndices de dissimilaridade de Jaccard calculados entre cada par de locais corroboraram este mesmo resultado em n??vel de esp??cie. Al??m disto, o n??mero de esp??cies declinou em fun????o da maior antropiza????o. Nas quatro ??reas de estudo, o maior n??mero de indiv??duos em flora????o ocorreu no fim da esta????o seca e no in??cio da esta????o chuvosa, e o maior n??mero de indiv??duos com frutos, durante a esta????o chuvosa. Todas as ??reas apresentaram picos de emiss??o de folhas e de perda de folhas na esta????o seca. As tr??s vari??veis ambientais tratadas neste estudo explicaram, independentemente, por????es relativamente pequenas da varia????o no n??mero de indiv??duos em cada uma das fenofases. Em geral, a correspond??ncia fenol??gica entre as s??ries de observa????es fenol??gicas tendeu a ser maior no caso das fenofases vegetativas, enquanto que entre as fenofases reprodutivas, a correspond??ncia variou amplamente. Foram detectadas associa????es tanto negativas quanto positivas entre precipita????o acumulada e o n??mero de ??rvores florindo, emitindo e perdendo folhas, enquanto que apenas rela????es positivas foram observadas com n??mero de ??rvores frutificando. A temperatura m??dia teve efeitos geralmente positivos sobre a express??o das fenofases. J?? a umidade relativa do ar apresentou efeitos tanto positivos quanto negativos sobre o n??mero de ??rvores com folhas, flores e frutos, e positivo sobre o n??mero de ??rvores perdendo folhas. Al??m disto, a frutifica????o foi principalmente determinada pela flora????o em meses anteriores nas quatro ??reas de estudo. Em geral, estes resultados discrepantes est??o de acordo com sugest??es anteriores de que os mecanismos adaptativos de ??rvores tropicais deveriam se refletir em fracas associa????es da fenologia com o clima. Fatores como as constitui????es gen??tica e fisiol??gica das plantas, a demografia das popula????es nas comunidades e intera????es ecol??gicas a como poliniza????o podem tomar parte na varia????o fenol??gica n??o explicada pelos modelos. Sugere-se que, em estudos futuros, tente-se integrar as contribui????es relativas de fatores tanto abi??ticos quanto bi??ticos na regula????o da fenologia de comunidades arb??reas. A compreens??o da fenologia vegetal em ambientes tropicais sob antropiza????o crescente ?? fundamental para a conserva????o e manejo racional das fun????es ecol??gicas de remanescentes florestais urbanos.