Suchergebnisse

Drought frequency and intensity are projected to increase throughout the southeastern USA, the natural range of loblolly pine (Pinus taeda L.), and are expected to have major ecological and economic implications. We analyzed the carbon and oxygen isotopic compositions in tree ring cellulose of loblolly pine in a factorial drought (similar to 30% throughfall reduction) and fertilization experiment, supplemented with trunk sap flow, allometry and microclimate data. We then simulated leaf temperature and applied a multi-dimensional sensitivity analysis to interpret the changes in the oxygen isotope data. This analysis found that the observed changes in tree ring cellulose could only be accounted for by inferring a change in the isotopic composition of the source water, indicating that the drought treatment increased the uptake of stored moisture from earlier precipitation events. The drought treatment also increased intrinsic water-use efficiency, but had no effect on growth, indicating that photosynthesis remained relatively unaffected despite 19% decrease in canopy conductance. In contrast, fertilization increased growth, but had no effect on the isotopic composition of tree ring cellulose, indicating that the fertilizer gains in biomass were attributable to greater leaf area and not to changes in leaf-level gas exchange. The multi-dimensional sensitivity analysis explored model behavior under different scenarios, highlighting the importance of explicit consideration of leaf temperature in the oxygen isotope discrimination (Delta O-18(c)) simulation and is expected to expand the inference space of the Delta O-18(c) models for plant ecophysiological studies. ; Pine Integrated Network: Education, Mitigation, and Adaptation project (PINEMAP); Coordinated Agricultural Project (USDA National Institute of Food and Agriculture award) [2011-68002-30185]; National Science Foundation (NSF)National Science Foundation (NSF) [EAR-1344703, IOS-1754893]; French Agence Nationale de la rechercheFrench National Research Agency (ANR) [ANR-17-ASIE-0007-02, ANR-18-PRIM-0006-09] ; This research was funded by The Pine Integrated Network: Education, Mitigation, and Adaptation project (PINEMAP), a Coordinated Agricultural Project (USDA National Institute of Food and Agriculture award 2011-68002-30185), the National Science Foundation (NSF-EAR-1344703 and NSF-IOS-1754893 to J.-C.D.) and the French Agence Nationale de la recherche (ANR-17-ASIE-0007-02 and ANR-18-PRIM-0006-09 to J.-C.D.). ; Public domain authored by a U.S. government employee

With continued global change as a result of land use changes, invasive species and changing climatic patterns, it is becoming increasingly important to understand the adaptability of Senegalia senegal provenances to maximize resilience in managed and natural populations of this species. The objective of this study is to investigate Senegalia senegal genotypic differences in water use efficiency (WUE) measured by stable C-13 isotope composition in foliage according to their ploidy levels. Secondary objectives are to discuss inherent adaptive variation related to soil pH, survival, growth indexes, gum arabic yield and WUE within provenance in the climate change context. A Senegalia senegal progeny trial, in Dahra, Senegal was used in this study: 443 adult trees consisting of 60 families nested within 4 provenances were assessed in this study. Results showed significant differences in gum yield among provenances (P = 0.0002) and families (P < 0.0001). Diamenar and Ngane provenances showed overall similar annual gum yield despite a lower tree survival rate of Ngane than Diamenar. Growth traits, especially stem volume index and crown area index were larger on Ngane provenance, which also displayed significantly higher foliar WUE and lower leaf area index (LAI) than the other provenances. WUE was positively correlated with gum yield (P = 0.0302), but the coefficient of determination was only 2%. Foliar delta C-13 varied significantly (P < 0.0001) between diploids (- 27.91 parts per thousand) and polyploids (- 27.12 parts per thousand). However, within each provenance no significant difference was found. Only 15% of isotope compositions could be explained by ploidy level variation. Differences found in growth and gum yield may be attributed to genotype-specific variation. However, a significant correlation between soil pH and tree survival rate was found (P = 0.0051; r = 0.60). This study confirmed a possible improvement of the gum arabic sector through genotype based selection. Ngane and Diamenar seem to be more profitable to grow in Dahra than the other tested provenances. Future research should investigate the effect of soil pH, other soil physical and chemical properties, and management activities to improve site quality on tree survival and gum yields among provenances. Further, more research is needed to clarify inherent traits underlying drought tolerance in the field and gum yield performance. ; United States Agency for International Development (USAID) as part of Feed the FutureUnited States Agency for International Development (USAID); U.S. Government's global hunger and food security initiative [AID-685-A-00-10-00194-00] ; We are grateful to Centre National de Recherche Forestiere for the logistical support provided during the fieldwork. We thank Mrs Momar Wade and Ibra Padane for their support in collecting data, Dr Marieme Fall Ba and Dr Mamadou Ousseynou Ly for their help to conduct soil analysis. A big thank to Mr Andy Laviner for his help on using the LAI 2200, and Mr David Mitchem to conduct isotope analysis of leaves. This article is made possible in part by the generous support of the American people through the United States Agency for International Development (USAID) as part of Feed the Future, the U.S. Government's global hunger and food security initiative, under the terms of Contract No. AID-685-A-00-10-00194-00 (USAID/Education and Research in Agriculture). The contents are the responsibility of the author(s) and do not necessarily reflect the views of USAID or the United States Government.

In natural grasslands, C-4 plant dominance increases with growing season temperatures and reflects distinct differences in plant growth rates and water use efficiencies of C-3 vs. C-4 photosynthetic pathways. However, in lawns, management decisions influence interactions between planted turfgrass and weed species, leading to some uncertainty about the degree of human vs. climatic controls on lawn species distributions. We measured herbaceous plant carbon isotope ratios (delta C-13, index of C-3/C-4 relative abundance) and C-4 cover in residential lawns across seven U.S. cities to determine how climate, lawn plant management, or interactions between climate and plant management influenced C-4 lawn cover. We also calculated theoretical C-4 carbon gain predicted by a plant physiological model as an index of expected C-4 cover due to growing season climatic conditions in each city. Contrary to theoretical predictions, plant delta C-13 and C-4 cover in urban lawns were more strongly related to mean annual temperature than to growing season temperature. Wintertime temperatures influenced the distribution of C-4 lawn turf plants, contrary to natural ecosystems where growing season temperatures primarily drive C-4 distributions. C-4 cover in lawns was greatest in the three warmest cities, due to an interaction between climate and homeowner plant management (e.g., planting C-4 turf species) in these cities. The proportion of C-4 lawn species was similar to the proportion of C-4 species in the regional grass flora. However, the majority of C-4 species were nonnative turf grasses, and not of regional origin. While temperature was a strong control on lawn species composition across the United States, cities differed as to whether these patterns were driven by cultivated lawn grasses vs. weedy species. In some cities, biotic interactions with weedy plants appeared to dominate, while in other cities, C-4 plants were predominantly imported and cultivated. Elevated CO2 and temperature in cities can influence C-3/C-4 competitive outcomes; however, this study provides evidence that climate and plant management dynamics influence biogeography and ecology of C-3/C-4 plants in lawns. Their differing water and nutrient use efficiency may have substantial impacts on carbon, water, energy, and nutrient budgets across cities. ; U.S. National Science Foundation Macrosystems Biology Program [EF-1065548, 1065737, 1065740, 1065741, 1065772, 1065785, 1065831, 121238320] ; This research was funded by a series of collaborative grants from the U.S. National Science Foundation Macrosystems Biology Program (EF-1065548, 1065737, 1065740, 1065741, 1065772, 1065785, 1065831, 121238320). The authors thank La'Shaye Ervin, William Borrowman, Moumita Kundu, and Barbara Uhl for field and laboratory assistance. ; Public domain authored by a U.S. government employee

Selver, Ayça Dogrul (Balikesir Author) ; Mobilisation of terrestrial organic carbon (terrOC) from permafrost environments in eastern Siberia has the potential to deliver significant amounts of carbon to the Arctic Ocean, via both fluvial and coastal erosion. Eroded terrOC can be degraded during offshore transport or deposited across the wide East Siberian Arctic Shelf (ESAS). Most studies of terrOC on the ESAS have concentrated on solvent-extractable organic matter, but this represents only a small proportion of the total terrOC load. In this study we have used pyrolysis-gas chromatography-mass spectrometry (py-GCMS) to study all major groups of macromolecular components of the terrOC; this is the first time that this technique has been applied to the ESAS. This has shown that there is a strong offshore trend from terrestrial phenols, aromatics and cyclopentenones to marine pyridines. There is good agreement between proportion phenols measured using py-GCMS and independent quantification of lignin phenol concentrations (r(2) = 0.67, p < 0.01, n = 24). Furfurals, thought to represent carbohydrates, show no offshore trend and are likely found in both marine and terrestrial organic matter. We have also collected new radiocarbon data for bulk OC (C-14(OC)) which, when coupled with previous measurements, allows us to produce the most comprehensive C-14(OC) map of the ESAS to date. Combining the C-14(OC) and py-GCMS data suggests that the aromatics group of compounds is likely sourced from old, aged terrOC, in contrast to the phenols group, which is likely sourced from modern woody material. We propose that an index of the relative proportions of phenols and pyridines can be used as a novel terrestrial vs. marine proxy measurement for macromolecular organic matter. Principal component analysis found that various terrestrial vs. marine proxies show different patterns across the ESAS, and it shows that multiple river-ocean transects of surface sediments transition from river-dominated to coastalerosion-dominated to marine-dominated signatures. ; NERC research grant - NE/I024798/1 NE/I027967/1 Ministry of National Education - Turkey Government of the Russian Federation - 14.Z50.31.0012 Knut & Alice Wallenberg Foundation Russian Academy of Sciences Swedish Research Council - 621-2004-4039 621-2007-4631 621-2013-5297 US National Oceanic and Atmospheric Administration (OAR Climate Program Office) - NA08OAR4600758 Russian Foundation for Basic Research (RFBR) - 08-05-13572 08-05-00191-a 07-05-00050a Swedish Polar Research Secretariat Nordic Council of Ministers National Science Foundation (NSF) - OPP ARC 0909546 NERC Natural Environment Research Council - NE/I024798/1 NE/I027967/1

In urban areas, anthropogenic drivers of ecosystem structure and function are thought to predominate over larger-scale biophysical drivers. Residential yards are influenced by individual homeowner preferences and actions, and these factors are hypothesized to converge yard structure across broad scales. We examined soil total C and total delta C-13, organic C and organic delta C-13, total N, and delta N-15 in residential yards and corresponding reference ecosystems in six cities across the United States that span major climates and ecological biomes (Baltimore, Maryland; Boston, Massachusetts; Los Angeles, California; Miami, Florida; Minneapolis-St. Paul, Minnesota; and Phoenix, Arizona). Across the cities, we found soil C and N concentrations and soil delta N-15 were less variable in residential yards compared to reference sites supporting the hypothesis that soil C, N, and delta N-15 converge across these cities. Increases in organic soil C, soil N, and soil delta N-15 across urban, suburban, and rural residential yards in several cities supported the hypothesis that soils responded similarly to altered resource inputs across cities, contributing to convergence of soil C and N in yards compared to natural systems. Soil C and N dynamics in residential yards showed evidence of increasing C and N inputs to urban soils or dampened decomposition rates over time that are influenced by climate and/or housing age across the cities. In the warmest cities (Los Angeles, Miami, Phoenix), greater organic soil C and higher soil delta C-13 in yards compared to reference sites reflected the greater proportion of C-4 plants in these yards. In the two warm arid cities (Los Angeles, Phoenix), total soil delta C-13 increased and organic soil delta C-13 decreased with increasing home age indicating greater inorganic C in the yards around newer homes. In general, soil organic C and delta C-13, soil N, and soil delta N-15 increased with increasing home age suggesting increased soil C and N cycling rates and associated C-12 and N-14 losses over time control yard soil C and N dynamics. This study provides evidence that conversion of native reference ecosystems to residential areas results in convergence of soil C and N at a continental scale. The mechanisms underlying these effects are complex and vary spatially and temporally. ; U.S. National Science FoundationNational Science Foundation (NSF) [EF-1065548, 1065737, 1065740, 1065741, 1065772, 1065785, 1065831, 121238320] ; The authors thank La'Shaye Ervin, William Borrowman, Moumita Kundu, and Barbara Uhl for field and laboratory assistance. This research was funded by a series of collaborative grants from the U.S. National Science Foundation (EF-1065548, 1065737, 1065740, 1065741, 1065772, 1065785, 1065831, 121238320). The authors appreciate valuable comments by anonymous reviewers on a previous version of the manuscript. ; Public domain authored by a U.S. government employee

Human activities have profoundly altered the global nutrient cycle through Land Use and Cover Changes (LUCCs) since the industrial revolution and especially during the Great Acceleration (1950 CE). Yet, the impact of such activities on terrestrial and aquatic ecosystems above their ecological baselines are not well known, especially when considering the response of these systems to the intensity of LUCCs on nutrient cycles. Here, we used a multiproxy approach (sedimentological, geochemical and isotopic analyses, historical records, climate data, and satellite images) to evaluate the role that LUCCs have on Nitrogen (N) cycling in a coastal mediterranean watershed system of central Chile over the last two centuries. Despite long-term anthropogenic use (agriculture, cattle grazing) in the Matanzas watershed- lake system, these LUCC appear to have had little impact on nutrient and organic matter transfer since the Spanish Colonial period. In contrast, the largest changes in N dynamics occurred in the mid-1970s, driven by the replacement of native forests and grasslands by government-subsidized tree plantations of introduced Monterey pine (Pinus radiata) and eucalyptus (Eucalyptus globulus). These LUCC had major impacts on the transfer of organic matter (which increased by 9.4%) and nutrients (as revealed by an increase in total N) to Laguna Matanzas. Our study shows that the presence of anthropogenic land use/cover changes do not necessarily alter nutrient supply and N availability per se but rather it is the magnitude and intensity of such changes that produce major impact on these processes in these mediterranean watersheds. ; Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) PIA AFB170008 Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) CONICYT FONDECYT 1191568 Doctoral grant Becas Chile 21150224 MEDLANT (Spanish Ministry of Economy and Competitiveness) CGL2016-76215-R Laboratorio Internacional de Cambio Global (LINCGlobal PUC-CSIC)

The productivity of agriculture in England and the Yangtze Delta are compared c.1620 and c.1820 in order to gauge the performance of the most advanced part of China vis‐à‐vis its counterpart in Europe. The value of real output is compared using purchasing power parity exchange rates. Output per hectare was nine times greater in the Yangtze Delta than in England. More surprisingly, output per day worked was about 90 per cent of the English performance. This put Yangtze farmers slightly behind English and Dutch farmers c.1820, but ahead of most other farmers in Europe—an impressive achievement. There was little change in Yangtze agricultural productivity between 1620 and 1820. In 1820, the real income of a Yangtze peasant family was also about the same as that of an English agricultural labourer. All was not rosy in the Yangtze, however, for incomes there were on a downward trajectory. Agriculture income per family declined between 1620 and 1820, even though income per day worked changed little since population growth led to smaller farms and fewer days worked per year. The real earnings of women in textile production also declined, since the relative price of cotton cloth dropped—possibly also because a larger population led to greater production. The implication is that the Yangtze family, unlike the English family, had a considerably higher real income c.1620, and that period was the Delta's golden age.