Effects of daily changes in environmental factors on the abundance and richness of Odonata

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Influência da estrutura do hábitat sobre a ictiofauna de um riacho em uma micro-bacia de pastagem, São Paulo, Brasil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Probabilidade de ocorrencia de periodos secos e chuvosos em Rio Claro - SP.

Using the daily rainfall data from 1961 through 1980 the frequency of dry and wet periods was determined. The results of the frequency distribution of dry and wet periods indicated that observed data fit very closely an equation of the type Y = aebn. -after English summary

Avaliação da influência do entorno e do Canal de Pereira Barreto na qualidade da água do Baixo São José dos Dourados

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Filogenia molecular e taxonomia do grupo Anolis chrysolepis Duméril & Bibron, 1837 (Squamata, Polychrotidae)

A Amazônia é considerada a maior floresta tropical contínua do mundo e diversos mecanismos têm sido propostos para tentar explicar a sua alta diversidade biológica. Um dos mecanismos mais discutidos desde sua proposição é a hipótese dos Refúgios, que se baseia na retração da floresta em períodos mais secos, isolando a fauna de florestas em refúgios imersos em uma matriz de vegetação aberta. Essas retrações e subseqüentes expansões em períodos mais mésicos provocariam a interrupção do fluxo gênico entre as populações isoladas e poderiam gerar especiação. Contudo, estudos moleculares recentes indicam que a diversificação de espécies de vertebrados de florestas tropicais provavelmente precede o período pleistocênico, originalmente indicado na hipótese dos Refúgios como o período em que esses eventos teriam ocorrido. A espécie politípica Anolis chrysolepis, juntamente com Anolis bombiceps, foi previamente estudada como um típico exemplo de diversificação gerada pelas flutuações climáticas do Pleistoceno, embora estudos posteriores tenham domonstrado a presença de grande divergência molecular entre parte das subespécies, indicando uma separação mais antiga desses táxons e levantando o questionamento sobre seu status taxonômico. Utilizamos o gene mitocondrial ND2 para investigar as relações filogenéticas entre as subespécies de Anolis chrysolepis e os táxons determinados em estudos anteriores como mais próximos a elas. Além disso, a sua morfologia e o seu status taxonômico foram revisados, a fim de verificar a congruência entre os dados morfológicos e moleculares, determinando se os táxons previamente reconhecidos morfologicamente são espécies válidas. Com base nos dois conjuntos de dados, nós elevamos as cinco subespécies do grupo Anolis chrysolepis ao status de espécies, diagnosticamos cada uma delas com comentários sobre as principais diferenças morfológicas entre as espécies irmãs e fornecemos novos dados de distribuição.

Denudação química e implicações na composição das águas superficiais da Bacia do Rio Jaú (SP)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Análise do potencial do sensor OLI (Operational Land Imager) a bordo do Landsat-8 em estimar a concentração de sólidos totais em suspensão no reservatório de Barra Bonita

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Millennial-Scale Climate Variability during the Last Glacial Period in the Tropical Andes

Millennial-scale climate variation during the Last Glacial period is evident in many locations worldwide, but it is unclear if such variation occurred in the interior of tropical South America, and, if so, how the low-latitude variation was related to its high-latitude counterpart. A high-resolution record, derived from the deep drilling of sediments on the floor of Lake Titicaca in the southern tropical Andes, is presented that shows clear evidence of millennial-scale climate variation between ~60 and 20 ka BP. This variation is manifested by alternations of two interbedded sedimentary units. The two units have distinctive sedimentary, geochemical, and paleobiotic properties that are controlled by the relative abundance of terrigenous or nearshore components versus pelagic components. The sediments of more terrigenous or nearshore nature likely were deposited during regionally wetter climates when river transport of water and sediment was higher, whereas the sediments of more pelagic character were deposited during somewhat drier climates regionally. The majority of the wet periods inferred from the Lake Titicaca sediment record are correlated with the cold events in the Greenland ice cores and North Atlantic sediment cores, indicating that increased intensity of the South American summer monsoon was part of near-global scale climate excursions.

Amazon Rainforest Exchange of Carbon and Subcanopy Air Flow: Manaus LBA Site-A Complex Terrain Condition

On the moderately complex terrain covered by dense tropical Amazon Rainforest (Reserva Biologica do Cuieiras-ZF2-02 degrees 36'17.1 '' S, 60 degrees 12'24.4 '' W), subcanopy horizontal and vertical gradients of the air temperature, CO2 concentration and wind field were measured for the dry and wet periods in 2006. We tested the hypothesis that horizontal drainage flow over this study area is significant and can affect the interpretation of the high carbon uptake rates reported by previous works at this site. A similar experimental design as the one by Tota et al. (2008) was used with a network of wind, air temperature, and CO2 sensors above and below the forest canopy. A persistent and systematic subcanopy nighttime upslope (positive buoyancy) and daytime downslope (negative buoyancy) flow pattern on a moderately inclined slope (12%) was observed. The microcirculations observed above the canopy (38 m) over the sloping area during nighttime presents a downward motion indicating vertical convergence and correspondent horizontal divergence toward the valley area. During the daytime an inverse pattern was observed. The microcirculations above the canopy were driven mainly by buoyancy balancing the pressure gradient forces. In the subcanopy space the microcirculations were also driven by the same physical mechanisms but probably with the stress forcing contribution. The results also indicated that the horizontal and vertical scalar gradients (e. g., CO2) were modulated by these micro-circulations above and below the canopy, suggesting that estimates of advection using previous experimental approaches are not appropriate due to the tridimensional nature of the vertical and horizontal transport locally. This work also indicates that carbon budget from tower-based measurement is not enough to close the system, and one needs to include horizontal and vertical advection transport of CO2 into those estimates.

Mineralogy-based quantitative precipitation and temperature reconstructions from annually laminated lake sediments (Swiss Alps) since AD 1580

[1] We present quantitative autumn, summer and annual precipitation and summer temperature reconstructions from proglacial annually laminated Lake Silvaplana, eastern Swiss Alps back to AD 1580. We used X-ray diffraction peak intensity ratios of minerals in the sediment layers (quartz qz, plagioclase pl, amphibole am, mica mi) that are diagnostic for different source areas and hydro-meteorological transport processes in the catchment. XRD data were calibrated with meteorological data (AD 1800/1864–1950) and revealed significant correlations: mi/pl with SON precipitation (r = 0.56, p < 0.05) and MJJAS precipitation (r = 0.66, p < 0.01); qz/mi with MJJAS temperature (r = −0.72, p < 0.01)and qz/am with annual precipitation (r = −0.54, p < 0.05). Geological catchment settings and hydro-meteorological processes provide deterministic explanations for the correlations. Our summer temperature reconstruction reproduces the typical features of past climate variability known from independent data sets. The precipitation reconstructions show a LIA climate moister than today. Exceptionally wet periods in our reconstruction coincide with regional glacier advances.

Precipitation over the past four centuries in the Dieshan Mountains as inferred from tree rings: An introduction to an HHT-based method

To improve our understanding of the Asian monsoon system, we developed a hydroclimate reconstruction in a marginal monsoon shoulder region for the period prior to the industrial era. Here, we present the first moisture sensitive tree-ring chronology, spanning 501 years for the Dieshan Mountain area, a boundary region of the Asian summer monsoon in the northeastern Tibetan Plateau. This reconstruction was derived from 101 cores of 68 old-growth Chinese pine (Pinus tabulaeformis) trees. We introduce a Hilbert–Huang Transform (HHT) based standardization method to develop the tree-ring chronology, which has the advantages of excluding non-climatic disturbances in individual tree-ring series. Based on the reliable portion of the chronology, we reconstructed the annual (prior July to current June) precipitation history since 1637 for the Dieshan Mountain area and were able to explain 41.3% of the variance. The extremely dry years in this reconstruction were also found in historical documents and are also associated with El Niño episodes. Dry periods were reconstructed for 1718–1725, 1766–1770 and 1920–1933, whereas 1782–1788 and 1979–1985 were wet periods. The spatial signatures of these events were supported by data from other marginal regions of the Asian summer monsoon. Over the past four centuries, out-of-phase relationships between hydroclimate variations in the Dieshan Mountain area and far western Mongolia were observed during the 1718–1725 and 1766–1770 dry periods and the 1979–1985 wet period.

(Appendix 1) Age, Ge/Si ratio, aluminium and opal contents in ODP Sites 175-1081 and 175-1084

As a result of both culture and sediment core studies, the ratio of germanium (Ge) to silicon (Si) in diatom shells has been proposed as a proxy for monitoring whole-ocean changes in seawater Ge/Si, a ratio affected by changes in continental weathering. However, because of the difficulties of extracting and cleaning diatom frustules from deep-sea sediments, only samples from highly pure diatom oozes in the Antarctic region have been previously analyzed. Here we present data on diatom Ge/Si ratios, (Ge/Si)opal, for the time interval between 3.1 and 1.9 Ma from a mid-latitude, coastal upwelling area where significant terrigenous sediment input complicated the sample processing and analyses. In general, our (Ge/Si)opal values show the same decreasing trend after 2.6 Ma than previously measured in Antarctic sediments (Shemesh et al., 1989. Paleoceanography 4, 221-231), but with a noisier background that may reflect the local imprint of proximal continental input superimposed upon global changes in the ocean reservoir. The time of initiation of large-scale North Hemisphere glaciation at ~2.6 Ma is characterized by a declining pattern of diatom Ge/Si ratios, which could have resulted from a global increase in the input of riverine Si due to enhanced silica weathering and/or equatorward (northward) intrusions of subantarctic waters enriched in silica. High (Ge/Si)opal ratios are associated with high opal contents from the same sediment samples and with warm climate as indicated by depleted benthic foraminiferal d18O values from the North and Equatorial Atlantic. Cold periods signified by enriched benthic d18O values, on the contrary, are associated with lower (Ge/Si)opal ratios. We interpret diatom Ge/Si values to reflect the prevailing weathering state on the continents, with greater chemical weathering during warm and wet periods of the Pliocene and less during cooler and drier intervals.

Stable hydrogen isotopic composition (dD) and stable carbon isotopic composition (d13C) of sediment core GeoB9508-5 off Senegal

To reconstruct variability of the West African monsoon and associated vegetation changes on precessional and millennial time scales, we analyzed a marine sediment core from the continental slope off Senegal spanning the past 44,000 years (44 ka). We used the stable hydrogen isotopic composition (dD) of individual terrestrial plant wax n-alkanes as a proxy for past rainfall variability. The abundance and stable carbon isotopic composition (d13C) of the same compounds were analyzed to assess changes in vegetation composition (C3/C4 plants) and density. The dD record reveals two wet periods that coincide with local maximum summer insolation from 38 to 28 ka and 15 to 4 ka and that are separated by a less wet period during minimum summer insolation. Our data indicate that rainfall intensity during the rainy season throughout both wet humid periods was similar, whereas the length of the rainy season was presumably shorter during the last glacial than during the Holocene. Additional dry intervals are identified that coincide with North Atlantic Heinrich stadials and the Younger Dryas interval, indicating that the West African monsoon over tropical northwest Africa is linked to both insolation forcing and high-latitude climate variability. The d13C record indicates that vegetation of the western Sahel was consistently dominated by C4 plants during the past 44 ka, whereas C3-type vegetation increased during the Holocene. Moreover, we observe a gradual ending of the Holocene humid period together with unchanging ratio of C3 to C4 plants, indicating that an abrupt aridification due to vegetation feedbacks is not a general characteristic of this time interval.

Age determination and stable isotope records of sediment core M78/1_235-1

Paleoenvironmental studies and climate models demonstrate that fluvial runoff and moisture availability in the Caribbean hinterland react very sensitively to climatic variations. Late Pleistocene and Holocene climate records document pronounced dry and wet periods over tropical South America mainly caused by shifts of the Intertropical Convergence Zone (ITCZ). However, forcing mechanisms for changes in the ITCZ position remain controversial. Here we present high-resolution foraminiferal Ba/Ca and d18Oseawater records from a core located within the Orinoco River outflow documenting abrupt hydrological changes in the Orinoco catchment area during the deglacial and Holocene. Our data, obtained from the surface-dwelling foraminifera Globigerinoides ruber (pink), show an abrupt increase in Ba/Ca ratios in the early Holocene, starting ~600 yr after the end of the Younger Dryas (YD) cold interval at ca. 10.8 ka and suggesting a massive reorganization of moisture sources in northern South America. In contrast, the salinity dependent d18Oseawater from the same samples shows a gradual decrease starting at the end of the YD. The offset of our Ba/Ca peak excludes meltwater release in conjunction with the northern Andean glacier retreat well before the end of the YD as a forcing mechanism. We suggest that the Ba/Ca record documents an abrupt increase in Ba-rich waters of a northern Andean source caused by the insolation-driven shift of the ITCZ and/or enhanced monsoon activity.

Biogeochemical Processes on Tree Islands in the Greater Everglades: Initiating a New Paradigm

Scientists’ understanding of the role of tree islands in the Everglades has evolved from a plant community of minor biogeochemical importance to a plant community recognized as the driving force for localized phosphorus accumulation within the landscape. Results from this review suggest that tree transpiration, nutrient infiltration from the soil surface, and groundwater flow create a soil zone of confluence where nutrients and salts accumulate under the head of a tree island during dry periods. Results also suggest accumulated salts and nutrients are flushed downstream by regional water flows during wet periods. That trees modulate their environment to create biogeochemical hot spots and strong nutrient gradients is a significant ecological paradigm shift in the understanding of the biogeochemical processes in the Everglades. In terms of island sustainability, this new paradigm suggests the need for distinct dry-wet cycles as well as a hydrologic regime that supports tree survival. Restoration of historic tree islands needs further investigation but the creation of functional tree islands is promising.