Search

Made available in DSpace on 2021-06-25T15:01:45Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-04-09 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Deforestation and habitat loss resulting from land use changes are some of the utmost anthropogenic impacts that threaten tropical birds in human-modified landscapes (HMLs). The degree of these impacts on birds' diet, habitat use, and ecological niche can be measured by isotopic analysis. We investigated whether the isotopic niche width, food resources, and habitat use of bird trophic guilds differed between HMLs and natural landscapes (NLs) using stable carbon (delta C-13) and nitrogen isotopes (delta N-15). We analyzed feathers of 851 bird individuals from 28 landscapes in the Brazilian Atlantic Forest. We classified landscapes into two groups according to the percentage of forest cover (HMLs = 47%), and compared the isotopic niche width and mean values of delta C-13 and delta N-15 for each guild between landscape types. The niches of frugivores, insectivores, nectarivores, and omnivores were narrower in HMLs, whereas granivores showed the opposite pattern. In HMLs, nectarivores showed a reduction of 44% in niche width, while granivores presented an expansion of 26%. Individuals in HMLs consumed more resources from agricultural areas (C-4 plants), but almost all guilds showed a preference for forest resources (C-3 plants) in both landscape types, except granivores. Degraded and fragmented landscapes typically present a lower availability of habitat and food resources for many species, which was reflected by the reduction in niche width of birds in HMLs. Therefore, to protect the diversity of guilds in HMLs, landscape management strategies that offer birds more diverse habitats must be implemented in tropical regions. Univ Sao Paulo, Dept Ciencias Florestais, Lab Ecol Manejo & Conservaeao Fauna Silvestre LEM, Escola Super Agr Luiz de Queiroz, Av Padua Dias 11, BR-13418900 Piracicaba, SP, Brazil Univ Sao Paulo, Ctr Energia Nucl Agr, Lab Ecol Isotop, Av Centenario 303, BR-13416903 Piracicaba, SP, Brazil Univ Sao Paulo, Museu Zool, Secao Aves, Av Nazare 481, BR-04263000 Sao Paulo, SP, Brazil Univ Estadual Paulista, Inst Biociencias, Dept Biodiversidade, Av 24-A 1515, BR-13506900 Rio Claro, SP, Brazil Univ Estadual Campinas, Inst Biol, Dept Biol Anim, Lab Interacoes Vertebrados Plantas, Rua Monteiro Lobato 255, BR-13083862 Campinas, SP, Brazil Univ Estadual Paulista, Fac Ciencias, Dept Ciencias Biol, Av Eng Luiz Edmundo Carrijo Coube 14-01, BR-17033360 Bauru, SP, Brazil Univ Fed Sao Carlos, Ctr Ciencias & Tecnol Sustentabilidade, Dept Ciencias Ambientais, Rodovia Joao Leme dos Santos SP-264 Km 110, BR-18052780 Sorocaba, SP, Brazil Inst Chico Mendes Conservacao Biodiversidade, Ctr Nacl Pesquisa & Conservacao Mamiferos Carnivo, Estr Municipal Hisaichi Takebayashi 8600, BR-12952011 Atibaia, SP, Brazil Inst Nacl Mata Atlantica, Av Jose Ruschi 4, BR-29650000 Santa Teresa, ES, Brazil Inst Procarnivoros, Av Horacio Netto 1030,Parque Edmundo Zanoni, BR-12945010 Atibaia, SP, Brazil Univ Estadual Paulista, Inst Biociencias, Dept Biodiversidade, Av 24-A 1515, BR-13506900 Rio Claro, SP, Brazil Univ Estadual Paulista, Fac Ciencias, Dept Ciencias Biol, Av Eng Luiz Edmundo Carrijo Coube 14-01, BR-17033360 Bauru, SP, Brazil FAPESP: 2010/05343-5 FAPESP: 2011/06782-5 FAPESP: 2011/04046-0 FAPESP: 2018-05970-1 FAPESP: 2020/076190 CAPES: 88882.328664/2019-01 CNPq: 300744/2020-0 CAPES: 001-CAPES PNPD 2013/1723 CNPq: 308632/2018-4 CNPq: 302291/2015-6 CNPq: 308337/2019-0 CNPq: 304742/2019-8

Historically, anthropogenic fixed nitrogen has been purposely increased to benefit food production and global development. One consequence of this increase has been to raise concentrations of nitrogen in aquatic ecosystems. To evaluate whether nitrogen pollution promotes changes in the estimates of niche space of fish communities, we examined 16 sites along a Brazilian river basin highly impacted by anthropogenic activities, especially discharge of domestic and industrial sewage from a region with more than 5 million inhabitants. We analysed the carbon (δ13C) and nitrogen (δ15N) isotope ratios of fish species and both autochthonous (periphyton) and allochthonous (course and fine particulate organic matter) basal food resources. To estimate the magnitude of nitrogen pollution, we measured the nitrate and ammonium concentrations at each site. Sampling was conducted in the dry and wet seasons to evaluate the influence of seasonality. Nitrogen pollution generally increased estimates of niche space, and seasonality influenced only the niche estimates of fish communities from polluted sites. In addition, isotopic analyses of nitrogen polluted sites yielded unrealistic estimates of trophic positioning (detritivores at the top of the food web). We conclude that changes in niche space estimates reflect both alterations in baseline isotopic values and differential trophic behaviour among fishes. Our study suggests that under conditions of high pollution, other factors appear to influence isotopic estimates of niche, such as isotopically distinct sources that have not been sampled, and/or differences in δ15N turnover rates between fish tissue and basal resources, creating isotopic baselines that are challenging to interpret.

Deforestation and habitat loss resulting from land use changes are some of the utmost anthropogenic impacts that threaten tropical birds in human-modified landscapes (HMLs). The degree of these impacts on birds' diet, habitat use, and ecological niche can be measured by isotopic analysis. We investigated whether the isotopic niche width, food resources, and habitat use of bird trophic guilds differed between HMLs and natural landscapes (NLs) using stable carbon (δ

Leaves of 208 trees were collected for isotopic analysis together with wood from 36 tree boles and 18 samples of fine litter from a terra-firme forest located at Samuel Ecological Reserve, Rondonia State, in the southwestern Amazon region. The range of δ13C values in leaves was from −28 to −36‰, with an average (±1 SD) of −32.1 ± 1.5‰, which was more negative than the δ13C values of bole samples (−28.4 ± 2.0‰) and fine litter (−28.7 ± 2.0‰). These values are within the range found for tropical and subtropical forests. Pooling the δ13C values for leaf samples from trees of the same height gave averages which were positively correlated with plant height at a highly significant level, with a slope of 0.06 and an intercept of −33.3‰ and a correlation coefficient r2=0.70 (P

Sustainable management for existing Amazonian forests requires an extensive knowledge about the limits of ecosystem nutrient cycles. Therefore, symbiotic nitrogen (N2) fixation of legumes was investigated in a periodically flooded forest of the central Amazon floodplain (Várzea) over two hydrological cycles (20 months) using the 15N natural abundance method. No seasonal variation in 15N abundance (delta 15N values) in trees which would suggest differences in N2 fixation rates between the terrestrial and the aquatic phase was found. Estimations of the percentage of N derived from atmosphere (%Ndfa) for the nodulated legumes with Neptunia oleracea on the one side and Teramnus volubilis on the other resulted in mean %Ndfa values between 9 and 66%, respectively. More than half of the nodulated legume species had %Ndfa values above 45%. These relatively high N gains are important for the nodulated legumes during the whole hydrological cycle. With a %Ndfa of 4-5% for the entire Várzea forest, N2 fixation is important for the ecosystem and therefore, has to be taken into consideration for new sustainable land-use strategies in this area.