Validation of MODIS Vegetation Continuous Fields for monitoring deforestation and forest degradation: two cases in Mexico     

Yan Gao  Adrian Ghilardi  Jaime Paneque-Galvez  Margaret Skutsch  Jean François Mas 《国际地球制图》2016,31(9):1019-1031

This study assesses whether MODIS Vegetation Continuous Fields percent tree cover (PTC) data can detect deforestation and forest degradation. To assess the usefulness of PTC for detecting deforestation, we used a data set consisting of eight forest and seven non-forest categories. To evaluate forest degradation, we used data from two temperate forest types in three conservation states: primary (dense), secondary (moderately degraded) and open (heavily degraded) forest. Our results show that PTC can differentiate temperate forest from non-forest categories (p = 0.05) and thus suggests PTC can adequately detect deforestation in temperate forests. In contrast, single-date PTC data does not appear to be adequate to detect forest degradation in temperate forests. As for tropical forest, PTC can partially discriminate between forest and non-forest categories.  相似文献   

Inter‐laboratory Characterisation of Apatite Reference Materials for Chlorine Isotope Analysis     

Alicja Wudarska  Ewa S&#x;aby  Michael Wiedenbeck  Jaime D. Barnes  Magali Bonifacie  Neil C. Sturchio  Grard Bardoux  Frdric Couffignal  Johannes Glodny  Linnea Heraty  Timm John  Christof Kusebauch  Sathish Mayanna  Franziska D. H. Wilke  Ewa Deput 《Geostandards and Geoanalytical Research》2021,45(1):121-142

Here we report on a set of six apatite reference materials (chlorapatites MGMH#133648, TUBAF#38 and fluorapatites MGMH#128441A, TUBAF#37, 40, 50) which we have characterised for their chlorine isotope ratios; these RMs span a range of Cl mass fractions within the apatite Ca₁₀(PO₄)₆(F,Cl,OH)₂ solid solution series. Numerous apatite specimens, obtained from mineralogical collections, were initially screened for ³⁷Cl/³⁵Cl homogeneity using SIMS followed by δ³⁷Cl characterisation by gas source mass spectrometry using both dual‐inlet and continuous‐flow modes. We also report major and key trace element compositions as determined by EPMA. The repeatability of our SIMS results was better than ± 0.10‰ (1s) for the five samples with > 0.5 % m/m Cl and ± 0.19‰ (1s) for the low Cl abundance material (0.27% m/m). We also observed a small, but significant crystal orientation effect of 0.38‰ between the mean ³⁷Cl/³⁵Cl ratios measured on three oriented apatite fragments. Furthermore, the results of GS‐IRMS analyses show small but systematic offset of δ³⁷Cl_SMOC values between the three laboratories. Nonetheless, all studied samples have comparable chlorine isotope compositions, with mean 10³δ³⁷Cl_SMOC values between +0.09 and +0.42 and in all cases with 1s ≤ ± 0.25.  相似文献   

Relationships between land-use and forced-pool characteristics in the Colorado Front Range     

Jaime R. Goode  Ellen Wohl   《Geomorphology》2007,83(3-4):249

Land use practices in Colorado during the last two centuries altered the supply of sediment and water to many channels in the upper South Platte Basin. As a result of increased supply of sediment and mobility and reduced peak flows, the characteristics of pools associated with channel constrictions, referred to as forced pools, may have been altered. Increased supply of sediment and reduced transport capacity of high flows could lead to aggradation in forced pools. Channel confined by road corridors could lead to high velocities at normal flows, increased energy dissipation from riprap, or even increased pool frequency resulting from failed riprap. To assess potential alterations, four hypotheses were tested: (1) impacted streams will show significantly different mean volume of pools than a control stream; (2) mean volume of pools on streams where land-use activities increased the supply of sediment will be significantly different from streams solely affected by flow regulation; (3) the strongest change in characteristics of pools of impacted streams will be a reduced volume of pools; (4) streams affected by road corridors will show statistically lower spacing of pools than streams unaffected by roads. The downstream spacing and residual volume of twenty consecutive forced pools were surveyed on five streams in the Colorado Front Range that varied from no contemporary impact to multiple historical and contemporary impacts. ANCOVA with stepwise model selection indicated that degree of land-use (categorical), bankfull spacing of pools, upstream riffle slope and expansion ratio were all significant (α = 0.1) predictors of volume of pools (R² = 0.73). Simple linear regression of mean volume of pools and stream specific variables (gradient, drainage area and discharge) and least square means comparison of mean volume of pools indicated a need to standardize volumes of pools by slope and discharge so that the volumes of pools could be compared among different levels of land-use. Significant correlations between drainage area and volume of pools allowed volume of pools to be standardized by drainage area and thereby discharge. This dimensionless variable was also significantly correlated with channel slope, which permitted the construction of a new variable, PV_QS (volume of pools standardized by discharge and slope). Least square means comparison of mean PV_QS revealed that the control reach was significantly different from road-impacted reaches. Mean volume of pools was significantly larger in the control reach compared to all but one road-impacted stream. This was likely a function of higher wood loading in the control reach and the competence of high flows in the road-impacted reach. Streams affected by road corridors did not have significantly different bankfull spacing of pools from streams not impacted by roads. The multiple interactions among control and response variables explored in this study indicate the need to identify the most constrained and sensitive response variables when attempting to assess channel response to land use.  相似文献   

Physico-chemical seasonal variability of a tropical estuary: major and minor elements in water and air     

L.?Rosales HozEmail author  A.?Carranza Edwards  P.?Carvajal Romero  C.?Mendez Jaime  M.?E.?Ruiz Santoyo 《Environmental Geology》2003,44(7):790-798

The lower reaches of the Coatzacoalcos River in southeast Mexico is an area of intense industrial development. The physico-chemical characteristics of the area have exhibited differences over the years. Apparently from the associated outcroppings of limestone in the Uxpanapa River Basin, the major elements that are dissolved show higher concentrations of Ca, Mg and HCO₃^– in the waters supplied by this river. The water in the Calzadas River contains high concentrations of Ca, SO₄ and HCO₃^– that are associated with the saline domes crossed by this river. Due to industrial discharges, the sulfate concentration is very high in the water and air during April. Nitrate concentration diminishes with salinity. Higher nitrate as well as nitrite and ammonia levels are present during flood season. Phosphate concentration, associated with high oxygen levels, is higher in January. Zn, Cu and Cr are higher during the dry season (April) when dilution is minimal and low levels of TOC are present. The smaller concentrations of Zn and Cu observed in January are associated with high TOC values in water. The lower levels of Cr present in August are associated with high amounts of suspended matter. Pajaritos Lagoon and Teapa-L, with large industrial discharges, have the highest nutrient and dissolved metal concentrations in the area. Air particles smaller than 2.5 m contain Fe, V, Ti, Cu, Zn, and high amounts of S. These anomalous concentrations of sulfates and metals are attributed to anthropogenic sources.  相似文献   

Coupled climate impacts of the Drake Passage and the Panama Seaway     

Simon Yang  Eric Galbraith  Jaime Palter 《Climate Dynamics》2014,43(1-2):37-52

Tectonically-active gateways between ocean basins have modified ocean circulation over Earth history. Today, the Atlantic and Pacific are directly connected via the Drake Passage, which forms a barrier to the time-mean geostrophic transport between the subtropics and Antarctica. In contrast, during the warm early Cenozoic era, when Antarctica was ice-free, the Drake Passage was closed. Instead, at that time, the separation of North and South America provided a tropical seaway between the Atlantic and Pacific that remained open until the Isthmus of Panama formed in the relatively recent geological past. Ocean circulation models have previously been used to explore the individual impacts of the Drake Passage and the Panama Seaway, but rarely have the two gateways been considered together, and most explorations have used very simple atmospheric models. Here we use a coupled ocean–ice–atmosphere model (GFDL’s CM2Mc), to simulate the impacts of a closed Drake Passage both with and without a Panama Seaway. We find that the climate response to a closed Drake Passage is relatively small when the Panama Seaway is absent, similar to prior studies, although the coupling to a dynamical atmosphere does increase the temperature change. However, with a Panama Seaway, closing Drake Passage has a much larger effect, due to the cessation of deep water formation in the northern hemisphere. Both gateways alter the transport of salt by ocean circulation, with the Panama Seaway allowing fresh Pacific water to be imported to the North Atlantic, and the Drake Passage preventing the flow of saline subtropical water to the circum-Antarctic, a flow that is particularly strong when the Panama Seaway is open. Thus, with a Panama Seaway and a closed Drake Passage, the Southern Ocean tends to be relatively salty, while the North Atlantic tends to be relatively fresh, such that the deep ocean is ventilated from the circum-Antarctic. Ensuing changes in the ocean heat transport drive a bi-polar shift of surface ocean temperatures, and the Intertropical Convergence Zone migrates toward the warmer southern hemisphere. The response of clouds to changes in surface ocean temperatures amplifies the climate response, resulting in temperature changes of up to 9 °C over Antarctica, even in the absence of land-ice feedbacks. These results emphasize the importance of tectonic gateways to the climate history of the Cenozoic, and support a role for ocean circulation changes in the glaciation of Antarctica.  相似文献   

Mercury colonial footprint in Darién Gulf sediments,Colombia     

Alex Rúa  Gerd Liebezeit  Jaime Palacio-Baena 《Environmental Earth Sciences》2014,71(4):1781-1789

The mercury (Hg) deposition history in the Darién Gulf is reconstructed from three sediment cores spanning up to 1,000 years. Knowledge on the contribution to global Hg budget from the Caribbean is limited. Patterns of water circulation, sediment deposition rates, cataclysmic atmospheric inputs, and post-depositional migration have been considered in Hg trapping in the seabed. The sediment delivery rates to the coastal zone over the Late Holocene have increased from 0.2 to 1 cm year^?1 owing to anthropogenic influence. This alteration took the form of geological effects, like coastal morphology change, that played a major role in Hg downcore signal preservation. Natural background Hg levels in Southern Caribbean sediments (77.0 μg kg^?1) are up to three times higher than preindustrial signals at other latitudes, because of volcanic contributions from the Pacific ring of fire. Enrichment factors rose from 0.9 to 1.5 (70.1–113.5 μg kg^?1) within profiles related to Hg usage since Spanish colonial times between the calendar years 1550 and 1811.  相似文献   

High-resolution seismic stratigraphy of the late Neogene of the central sector of the Colombian Pacific continental shelf: A seismic expression of an active continental margin     

Jaime Orlando Martínez  Eduardo López Ramos 《Journal of South American Earth Sciences》2011,31(1):28-44

The sedimentary prism of the central Pacific continental shelf of Colombia was affected by regional folding and faulting, and probably later mud diapirism, from the Late Miocene to the Holocene. Interpretation of high-resolution seismic lines (2 s/dt) revealed that the prism consists of 13 high-resolution seismic units, that can be separated into 5 seismic groups.Deposition of the prism and the associated stacking pattern, are probably the response to variable uplift and subsidence in a fore-arc basin that underwent important tectonic events by the end of the Miocene. Throughout the Pliocene, the continental shelf sedimentation was affected by the growing of a dome structure probable due to mud diapirism. This fact caused peripheral faults both normal and reverse that controlled the distribution of some of the seismic units. During the Late Pleistocene (Wisconsin stage?) a eustatic sea level fall caused the shoreline to advance about 50 km westward of its present position. Because of this eustatic sea level change, a strong fluvial dissection took place and is interpreted as the probable extension of the San Juan River to the south of the present day river mouth. Within this framework it is believed that the Malaga and Buenaventura Bays were the passageways of branches of the old drainage system of the San Juan River. The inner branch circulated through the present Buenaventura Bay and runs southward leaving the mark of an apparent valley identified in the seismic information in the eastern sector of the study area. This old fluvial valley and its filling material located in the present day inner continental shelf front of Buenaventura are postulated as important targets to find placer minerals such as gold and platinum.  相似文献   

From desert to Mediterranean rangelands: will increasing drought and inter-annual rainfall variability affect herbaceous annual primary productivity?     

Carly Golodets  Marcelo Sternberg  Jaime Kigel  Bertrand Boeken  Zalmen Henkin  No’am G. Seligman  Eugene David Ungar 《Climatic change》2013,119(3-4):785-798

Climate change is predicted to alter the rainfall regime in the Eastern Mediterranean Basin: total annual rainfall will decrease, while seasonal and inter-annual variation in rainfall will increase. Such changes in the rainfall regime could potentially lead to large-scale changes in aboveground net primary productivity (ANPP) in the region. We conducted a data-driven evaluation of herbaceous ANPP along an entire regional rainfall gradient, from desert (90 mm MAR [Mean Annual Rainfall]) to Mesic-Mediterranean (780 mm MAR) ecosystems, using the largest database ever collated for herbaceous ANPP in Israel, with the aim of predicting consequences of climate change for rangeland productivity. This research revealed that herbaceous ANPP increases with increasing rainfall along the gradient, but strong dependence on rainfall was only apparent within dry sites. Rain Use Efficiency peaks at mid-gradient in Mediterranean sites without woody vegetation (560 and 610 mm MAR). Inter-annual coefficients of variation in rainfall and herbaceous ANPP decrease along the rainfall gradient up to ca. 500 mm MAR. Climate change is more likely to affect herbaceous ANPP of rangelands in the arid end of the rainfall gradient, requiring adaptation of rangeland management, while ANPP of rangelands in more mesic ecosystems is less responsive to variation in rainfall. We conclude that herbaceous ANPP in most Mediterranean rangelands is less vulnerable to climate change than generally predicted.  相似文献   

The Chicxulub Scientific Drilling Project (CSDP)     

Jaime Urrutia‐Fucugauchi  Joanna Morgan  Dieter Stffler  Philippe Claeys 《Meteoritics & planetary science》2004,39(6):787-790

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Parametric analysis of gravity offshore structures: Part 2     

Jaime Dominguez  Enrique Alarcon 《Applied Ocean Research》1981,3(3):101-104

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