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排序方式: 共有87条查询结果,搜索用时 218 毫秒
1.
V. Maquere J. P. Laclau M. Bernoux L. Saint‐Andre J. L. M. Gonçalves C. C. Cerri M. C. Piccolo J. Ranger 《European Journal of Soil Science》2008,59(5):863-877
In Brazil, most Eucalyptus stands have been planted on Cerrado (shrubby savanna) or on Cerrado converted into pasture. Case studies are needed to assess the effect of such land use changes on soil fertility and C sequestration. In this study, the influence of Cerrado land development (pasture and Eucalyptus plantations) on soil organic carbon (SOC) and nitrogen (SON) stocks were quantified in southern Brazil. Two contrasted silvicultural practices were also compared: 60 years of short‐rotation silviculture (EUCSR) versus 60 years of continuous growth (EUCHF). C and N soil concentrations and bulk densities were measured and modelled for each vegetation type, and SOC and SON stocks were calculated down to a depth of 1 m by a continuous function. Changes in SOC and SON stocks mainly occurred in the forest floor (no litter in pasture and up to 0.87 kg C m?2 and 0.01 kg N m?2 in EUCSR) and upper soil horizons. C and N stocks and their confidence intervals were greatly influenced by the methodology used to compute these layers. C/N ratio and 13C analysis showed that down to a depth of 30 cm, the Cerrado organic matter was replaced by organic matter from newly introduced vegetation by as much as 75–100% for pasture and about 50% for EUCHF, poorer in N for Eucalyptus stands (C/N larger than 18 for Eucalyptus stands). Under pasture, 0–30 cm SON stocks (0.25 kg N m?2) were between 10 and 20% greater than those of the Cerrado (0.21 kg N m?2), partly due to soil compaction (limit bulk density at soil surface from 1.23 for the Cerrado to 1.34 for pasture). Land development on the Cerrado increased SOC stocks in the 0–30 cm layer by between 15 and 25% (from 2.99 (Cerrado) to 3.86 (EUCSR) kg C m?2). When including litter layers, total 0–30 cm carbon stocks increased by 35% for EUCHF (4.50 kg C m?2) and 53% for EUCSR (5.08 kg C m?2), compared with the Cerrado (3.28 kg C m?2), independently of soil compaction. 相似文献
2.
Janaina Braga do Carmo Marisa de Cssia Piccolo Cristiano Alberto de Andrade Carlos Eduardo Pellegrino Cerri Brigitte Josefine Feigl Erclito Sousa Neto Carlos Clemente Cerri 《Soil & Tillage Research》2007,96(1-2):250-259
Anthropogenic conversion of primary forest to pasture for cattle production is still frequent in the Amazon Basin. Practices adopted by ranchers to restore productivity to degraded pasture have the potential to alter soil N availability and N gas losses from soils. We examined short-term (35 days) effects of tillage prior to pasture re-establishment on soil N availability, CO2, NO and N2O fluxes and microbial biomass C and N under degraded pasture at Nova Vida ranch, Rondônia, Brazilian Amazon. We collected soil samples and measured gas fluxes in tilled and control (non tilled pasture) 12 times at equally spaced intervals during October 2001 to quantify the effect of tillage. Maximum soil NH4+ and NO3− pools were 13.2 and 6.3 kg N ha−1 respectively after tillage compared to 0.24 and 6.3 kg N ha−1 in the control. Carbon dioxide flux ranged from 118 to 181 mg C–CO2 m2 h−1 in the control (non-tilled) and from 110 to 235 mg C–CO2 m2 h−1 when tilled. Microbial biomass C varied from 365 to 461 μg g−1 in the control and from 248 to 535 μg g−1 when tilled. The values for N2O fluxes ranged from 1.22 to 96.9 μg N m−2 h−1 in the tilled plots with a maximum 3 days after the second tilling. Variability in NO flux in the control and when tilled was consistent with previous measures of NO emissions from pasture at Nova Vida. When tilled, the NO/N2O ratio remained <1 after the first tilling suggesting that denitrification dominated N cycling. The effects of tilling on microbial parameters were less clear, except for a decrease in qCO2 and an increase in microbial biomass C/N immediately after tilling. Our results suggest that restoration of degraded pastures with tillage will lead to less C matter, at least initially. Further long-term research is needed. 相似文献
3.
Serenella Nardi Adele Muscolo Salvatore Baiano Alessandro Piccolo 《Soil biology & biochemistry》2007,39(12):3138-3146
A humic acid (HA) isolated from a volcanic soil was separated in three fractions of decreasing molecular size (I, II and III) by preparative high performance size exclusion chromatography (HPSEC). The molecular content of the bulk soil HA and its size fractions was characterized by pyrolysis-GC-MS (thermochemolysis with tetramethylammonium hydroxide) and NMR spectroscopy. All soil humic materials were used to evaluate their effects on the enzymatic activities involved in glycolytic and respiratory processes of Zea mays (L.) seedlings. The elementary analyses and NMR spectra of the humic fractions indicated that the content of polar carbons (mainly carbohydrates) increased with decreasing molecular size of separated fractions. The products evolved by on-line thermochemolysis showed that the smallest size fraction (Fraction III) with the least rigid molecular conformation among the humic samples had the lowest content of lignin moieties and the largest amount of other non-lignin aromatic compounds. The bulk HA and the three humic fractions affected the enzyme activities related to glycolysis and tricarboxylic acid cycle (TCA) in different ways depending on molecular size, molecular characteristics and concentrations. The overall effectiveness of the four fractions in promoting the metabolic pathways was in the order: III>HA>II>I. The largest effect of Fraction III, either alone or incorporated into the bulk HA, was attributed to a flexible conformational structure that promoted a more efficient diffusion of bioactive humic components to maize cells. A better knowledge of the relationship between molecular structure of soil humic matter and plant activity may be of practical interest in increasing carbon fixation in plants and redirect atmospheric CO2 into bio-fuel resources. 相似文献
4.
Zaffaroni E Teresa Manfredi M Citterio C Sala M Piccolo G Lanfranchi P 《Veterinary parasitology》2000,90(3):221-230
Abomasums from 641 alpine wild ruminants representing five different species (Cervus elaphus, Capreolus capreolus, Rupicapra rupicapra, Capra ibex, Ovis musimon) and from 19 domestic sheep (Ovis aries) from alpine areas were examined in order to investigate the host-specificity of abomasal helminths. Nine out of 20 helminth species were found in at least five different host species. A discriminant analysis was able to significantly discriminate the hosts on the basis of their helminth community composition with the exception of O. musimon and O. aries. Based on the correlation between each variable represented by helminth species with the most explanatory discriminant axis, it was possible to classify helminths into specialists and generalists. Specialists are represented by the dominant species in a community of an host species or family while generalists appear in the communities of many different hosts as intermediate species. Due to the pathogenic potential of some of these generalist species (i.e. Haemonchus contortus, Trichostrongylus axei) and their ability to adapt easily to the conditions found in several different hosts, they appear to be the most important from a sanitary point of view. 相似文献
5.
Stewardship and management of freshwater ecosystems: From Leopold's land ethic to a freshwater ethic
Steven J. Cooke Abigail J. Lynch John J. Piccolo Julian D. Olden Andrea J. Reid Steve J. Ormerod 《水产资源保护:海洋与淡水生态系统》2021,31(6):1499-1511
- In 1949, Aldo Leopold formalized the concept of the ‘land ethic’, in what emerged as a foundational and transformational way of thinking about natural resource management, biodiversity conservation, and stewardship in terrestrial systems. Yet, the land ethic has inherent linkages to aquatic ecosystems; Leopold himself conducted research on rivers and lakes, and freshwater ecosystems figured widely in his writing.
- We reflect on the land ethic and other aspects of Leopold's scholarship to identify key messages that provide insight into the stewardship and management of freshwater ecosystems around the globe. We also frame what we call the ‘freshwater ethic’ around Leopold's legacy. Although Leopold could not have envisaged the stressors affecting modern aquatic ecosystems, his core principles remain salient. These apply not only to ecosystem protection, but also to the ethics of modern conservation economics, sustainability, and the protection of natural capital, in which lakes, rivers, and wetlands now figure prominently.
- We identify key ‘Aldo-inspired’ recommendations for protecting and restoring freshwater ecosystems in the Anthropocene that emanate directly from his writings (e.g. adopt an ecosystem approach, identify win–win–win scenarios, recognize the irreplaceability of wild waters, and strive for freshwater optimism).
- In an epoch where links between people and nature are becoming more explicit in environmental management, policy, and governance, we suggest that Aldo Leopold's work illustrates how inspirational, seminal thinkers have offered leadership in this domain. We contend that today there is still much that can be learned from Leopold, especially by the next generation of environmental practitioners, to ensure the effective stewardship of our aquatic ecosystems.
- We submit that the adoption of a freshwater ethic in parallel with Leopold's land ethic will enhance the stewardship of the world's increasingly threatened fresh waters by raising the profile of the plight of fresh waters and identifying enduring actions that, if embraced, will help conserve and restore biodiversity.
6.
Nino Tavares Amazonas Luiz Antonio MartinelliMarisa de Cássia Piccolo Ricardo Ribeiro Rodrigues 《Forest Ecology and Management》2011,262(8):1551-1557
We considered whether ecological restoration using high diversity of native tree species serves to restore nitrogen dynamics in the Brazilian Atlantic Forest. We measured δ15N and N content in green foliage and soil; vegetation N:P ratio; and soil N mineralization in a preserved natural forest and restored forests of ages 21 and 52 years. Green foliage δ15N values, N content, N:P ratio, inorganic N and net mineralization and nitrification rates were all higher, the older the forest. Our findings indicate that the recuperation of N cycling has not been achieved yet in the restored forests even after 52 years, but show that they are following a trajectory of development that is characterized by their N cycling intensity becoming similar to a natural mature forest of the same original forest formation. This study demonstrated that some young restored forests are more limited by N compared to mature natural forests. We document that the recuperation of N cycling in tropical forests can be achieved through ecological restoration actions. 相似文献
7.
Carbon limitations to nitrous oxide emissions in a humid tropical forest of the Brazilian Amazon 总被引:2,自引:0,他引:2
D.?C.?Garcia-MontielEmail author J.?M.?Melillo P.?A.?Steudler C.?C.?Cerri M.?C.?Piccolo 《Biology and Fertility of Soils》2003,38(5):267-272
The availability of labile organic C for microbial metabolic processes could be an important factor regulating N2O emissions from tropical soils. We explored the effects of labile C on the emissions of N2O from a forest soil in the State of Rondônia in the southwestern quadrant of the Brazilian Amazon. We measured emissions of N2O from a forest soil after amendments with solutions containing glucose, water only or NO3–. Addition of glucose to the forest soil resulted in very large increases in N2O emissions whereas the water only and NO3– additions did not. These results suggest a strong C limitation on N2O production in this forest soil in the southwestern Amazon. 相似文献
8.
Quantitative aspects of solid-state C-NMR spectra of humic substances from soils of volcanic systems
Cross-Polarisation Magic Angle Spinning Carbon-13 Nuclear Magnetic Resonance spectroscopy (CPMAS 13C-NMR) represents one of the most powerful tools to investigate soil organic matter (SOM) mainly because of its inherent capacity to provide a semi-quantitative evaluation of carbon distribution. A critical parameter during acquisition of CPMAS 13C-NMR spectra is the contact time required to obtain the cross-polarisation between proton and carbon nuclei. The procedure to evaluate the best contact time for the acquisition of a quantitative CPMAS 13C-NMR spectrum is to perform Variable Contact Time (VCT) experiments. In this work the structural features of a number of purified humic substances from Italian and Costarican volcanic soils were investigated by CPMAS 13C-NMR spectroscopy after having performed preliminary VCT experiments. The VCT experiments showed that the average contact times vary according to the origin and chemical structure of the humic material. The optimal contact times (OCT) for nine humic samples were between 250 and 800 μs These values were different from the time of 1000 μs that is commonly applied as the best average contact time for humic materials. Moreover, by comparing the NMR data to those obtained by elemental analysis (C/H ratio), it appeared that the efficiency of the cross-polarisation between protons and carbons, and hence the contact time, is affected not only by the number of protons, but also by their distribution over the molecules. The evaluation of errors in quantitative estimation of the different carbons revealed that the use of OCT generally reduced by half the loss of signals occurring when the average contact time of 1000 μs is used in CPMAS 13C-NMR spectra of humic substances. 相似文献
9.
Cordenonsi M Montagner M Adorno M Zacchigna L Martello G Mamidi A Soligo S Dupont S Piccolo S 《Science (New York, N.Y.)》2007,315(5813):840-843
During development and tissue homeostasis, cells must integrate different signals. We investigated how cell behavior is controlled by the combined activity of transforming growth factor-beta (TGF-beta) and receptor tyrosine kinase (RTK) signaling, whose integration mechanism is unknown. We find that RTK/Ras/MAPK (mitogen-activated protein kinase) activity induces p53 N-terminal phosphorylation, enabling the interaction of p53 with the TGF-beta-activated Smads. This mechanism confines mesoderm specification in Xenopus embryos and promotes TGF-beta cytostasis in human cells. These data indicate a mechanism to allow extracellular cues to specify the TGF-beta gene-expression program. 相似文献
10.
Summary Lettuce and tomato seeds were treated in Petri dishes with a humic acid derived from an oxidized coal and with fractions of the same humic acid obtained by ultrafiltration through membranes of known molecular cutoff and by extracting with buffers set at pH 4 and pH 5. The unfractionated humic acid was applied at 40, 100, 1000, and 5000 mg l-1 whereas the humic fractions were applied at 40, 100, and 200 mg l-1. Germination parameters such as the number of total germinated seeds, the velocity of seed germination, the fresh weight and dry weight of total seedlings were measured and related to the chemical and physicochemical properties of the humic material. No increase in the germination percentage or the germination rate was observed for either lettuce or tomato seeds. The fresh weight of total seedlings and per seedling increased in treatments with unfractionated humic acid with increasing concentrations for both lettuce and tomato plants without showing signs of growth inhibition up to 5000 mg l-1. This was attributed to cell elongation and more efficient water uptake. For the lettuce, the fresh weight both of total seedlings and per seedling was enhanced by treating the seeds with fractions of low molecular weight and high content of acidic functions, whereas the dry weight both of total seedlings and per seedling did not change with the humic fraction used. For the tomato seeds in contrast, the dry weight both of total seedlings and per seedling was increased by the use of unfractionated humic acid and by some of the humic fractions. An uptake of humic material by growing tomato seedlings was inferred. 相似文献