scholarly journals Taxonomic Results of the BRYOTROP Expedition to Zaire and Rwanda 26. A new checklist of the mosses of Central Africa

1993 ◽  
Vol 8 (1) ◽  
pp. 223-273 ◽  
Author(s):  
S. Born ◽  
J. -P. Frahm ◽  
T. Pócs
Keyword(s):  
Central Africa ◽  
Herbarium Specimens ◽  
The Past ◽  
The Tropics ◽  
Belgian Congo

Central Africa was one of the first regions in the tropics, if not the first, for which a checklist of mosses was compiled. In 1940, Demaret published the “Prodrome des Bryophytes du Congo Belge et du Ruanda-Urundi”, followed by a supplement in 1946. In the 50 years since that time, numerous new contributions to the bryophyte flora of Central Africa have been made. Demaret added seven more publications on Zaire (formerly Belgian Congo). Potier de la Varde studied the bryophyte collections made during the surveys of the flora of the Central African volcanoes by Hedberg. De Sloover published a series of 14 papers dealing with his collections in Rwanda, Burundi and Zaire, combined with revisionary work. Finally, numerous nomenclatural changes, revisions and monographs have been made during the past 20 years. Therefore an update of Demaret’s checklist seemed desirable. For that reason a new list has been compiled, based on the data of Demaret (1940, 1946), with all available additions. This includes publications as well as herbarium specimens distributed by J.L. De Sloover (marked with the herbarium abbreviation NAM) and the collections made during the Bryotrop expedition to Rwanda and Zaire in 1991 (see special contributions in this volume).

Could marine animal conservation laws be responsible for the decline or extirpation of macroalgal populations in Bermuda over the past century?

2017 ◽  
Vol 60 (6) ◽  
Author(s):  
Craig W. Schneider ◽  
Christopher T. Flook
Keyword(s):  
Early 20Th Century ◽  
Past Century ◽  
Herbarium Specimens ◽  
Marine Animal ◽  
Population Abundance ◽  
Protected Species ◽  
Animal Conservation ◽  
Macroalgal Species ◽  
The Past ◽  
The Tropics

AbstractUsing over 10,000 archival herbarium specimens from Bermuda, we compared the presence or absence of seaweeds from a century ago with our more than 5000 collections from the last 30 years. Populations of parrotfish, important herbivores of macroalgae in the tropics, have increased since the 1993 amendment to the Bermuda 1978 Fisheries (Protected Species) Order. A fish pot ban for Bermuda was put into effect in 1990 to protect a variety of fish including parrotfish and several species of grouper, important predators of parrotfish that were rarely seen in island waters at the time. Intertidal grazing West Indian top shells were reintroduced in 1982 to Bermuda, and since then, along with the rise in parrotfish populations, inshore populations of many macroalgae have dramatically changed. We suggest that several large and abundant Bermuda macroalgal species recorded in the early 20th century appear to have been extirpated or are greatly diminished in sizes of individuals as well as population abundance, and propose that marine animal protections over the past 35 years are a possible reason for the changes we are presently observing.

scholarly journals Global climatology and trends in convective environments from ERA5 and rawinsonde data

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Mateusz Taszarek ◽  
John T. Allen ◽  
Mattia Marchio ◽  
Harold E. Brooks
Keyword(s):  
Large Scale ◽  
Climate Models ◽  
Global Climate ◽  
Convective Available Potential Energy ◽  
Global Climate Models ◽  
Convective Precipitation ◽  
The Past ◽  
The Tropics ◽  
Rawinsonde Data

AbstractGlobally, thunderstorms are responsible for a significant fraction of rainfall, and in the mid-latitudes often produce extreme weather, including large hail, tornadoes and damaging winds. Despite this importance, how the global frequency of thunderstorms and their accompanying hazards has changed over the past 4 decades remains unclear. Large-scale diagnostics applied to global climate models have suggested that the frequency of thunderstorms and their intensity is likely to increase in the future. Here, we show that according to ERA5 convective available potential energy (CAPE) and convective precipitation (CP) have decreased over the tropics and subtropics with simultaneous increases in 0–6 km wind shear (BS06). Conversely, rawinsonde observations paint a different picture across the mid-latitudes with increasing CAPE and significant decreases to BS06. Differing trends and disagreement between ERA5 and rawinsondes observed over some regions suggest that results should be interpreted with caution, especially for CAPE and CP across tropics where uncertainty is the highest and reliable long-term rawinsonde observations are missing.

scholarly journals NOTES ON EMBIDOBIINI (SCELIONIDAE: HYMENOPTERA) WITH DESCRIPTION OF A NEW GENUS

1972 ◽  
Vol 104 (4) ◽  
pp. 505-510 ◽  
Author(s):  
Lubomir Masner ◽  
Paul Dessart
Keyword(s):  
New Genus ◽  
Central Africa ◽  
Baltic Amber ◽  
The World ◽  
First Time ◽  
Belgian Congo

AbstractEndecascelio stipitipennis n. gen. and n. sp. is described from Central Africa (former Belgian Congo). The extent and interrelationships of the tribe Embidobiini are discussed. A diagnosis of the tribe and a key to genera of the world is given.The genus Embidobia Ashmead is for the first time reported from the Oligocene of Baltic amber.

Rising ecosystem water demand exacerbates the lengthening of tropical dry seasons

2021 ◽  
Author(s):  
Hao Xu ◽  
Xu Lian ◽  
Ingrid Slette ◽  
Hui Yang ◽  
Yuan Zhang ◽  
...  
Keyword(s):  
Water Demand ◽  
Potential Evapotranspiration ◽  
Central Africa ◽  
Dry Season ◽  
Land Area ◽  
Key Factor ◽  
Dry Seasons ◽  
The Tropics ◽  
Factor Governing

Abstract The timing and length of the dry season is a key factor governing ecosystem productivity and the carbon cycle of the tropics. Mounting evidence has suggested a lengthening of the dry season with ongoing climate change. However, this conclusion is largely based on changes in precipitation (P) compared to its long-term average (P ̅) and lacks consideration of the simultaneous changes in ecosystem water demand (measured by potential evapotranspiration, Ep, or actual evapotranspiration, E). Using several long-term (1979-2018) observational datasets, we compared changes in tropical dry season length (DSL) and timing (dry season arrival, DSA, and dry season end, DSE) among three common metrics used to define the dry season: P < P ̅, P < Ep, and P < E. We found that all three definitions show that dry seasons have lengthened in much of the tropics since 1979. Among the three definitions, P < E estimates the largest fraction (49.0%) of tropical land area likely experiencing longer dry seasons, followed by P < Ep (41.4%) and P < P ̅ (34.4%). The largest differences in multi-year mean DSL (> 120 days) among the three definitions occurred in the most arid and the most humid regions of the tropics. All definitions and datasets consistently showed longer dry seasons in southern Amazon (due to delayed DSE) and central Africa (due to both earlier DSA and delayed DSE). However, definitions that account for changing water demand estimated longer DSL extension over those two regions. These results indicate that warming-enhanced evapotranspiration exacerbates dry season lengthening and ecosystem water deficit. Thus, it is necessity to account for the evolving water demand of tropical ecosystems when characterizing changes in seasonal dry periods and ecosystem water deficits in an increasingly warmer and drier climate.

scholarly journals Three exceptionally strong East-Asian summer monsoon events during glacial conditions in the past 470 kyr

2008 ◽  
Vol 4 (6) ◽  
pp. 1289-1317 ◽  
Author(s):  
D.-D. Rousseau ◽  
N. Wu ◽  
Y. Pei ◽  
F. Li
Keyword(s):  
Summer Monsoon ◽  
Asian Monsoon ◽  
East Asian Monsoon ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Precipitation Regime ◽  
The Past ◽  
Ecological Requirements ◽  
Asian Summer ◽  
The Tropics

Abstract. Chinese loess sequences are interpreted as a reliable record of the past variation of the East Asian monsoon regime through the alternation of loess and paleosols units, dominated by the winter and summer monsoon, respectively. Different proxies have been used to describe this system, mostly geophysical, geochemical or sedimentological. Terrestrial mollusks are also a reliable proxy of past environmental conditions and are often preserved in large numbers in loess deposits. The analysis of the mollusk remains in the Luochuan sequence, comprising L5 loess to S0 soil, i.e. the last 500 ka, shows that for almost all identified species, the abundance is higher at the base of the interval (L5 to L4) than in the younger deposits. Using the present ecological requirements of the identified mollusk species in the Luochuan sequence allows the definition of two main mollusk groups varying during the last 500 kyr. The cold-aridiphilous individuals indicate the so-called Asian winter monsoon regime and predominantly occur during glacials, when dust is deposited. The thermal-humidiphilous mollusks are prevalent during interglacial or interstadial conditions of the Asian summer monsoon, when soil formation takes place. In the sequence, three events with exceptionally high abundance of the Asian summer monsoon indicators are recorded during the L5, L4 and L2 glacial intervals, i.e., at about 470, 360 and 170 kyr, respectively. The L5 and L4 events appear to be the strongest (high counts). Similar variations have also been identified in the Xifeng sequence, distant enough from Luochuan, but also in Lake Baikal further North, to suggest that this phenomenon is regional rather than local. The indicators of the summer monsoon within the glacial intervals imply a strengthened East-Asian monsoon interpreted as corresponding to marine isotope stages 6, 10 and 12, respectively. The L5 and L2 summer monsoons are coeval with Mediterranean sapropels S12 and S6, which characterize a strong African summer monsoon with relatively low surface water salinity in the Indian Ocean. Changes in the precipitation regime could correspond to a response to a particular astronomical configuration (low obliquity, low precession, summer solstice at perihelion) leading to an increased summer insolation gradient between the tropics and the high latitudes and resulting in enhanced atmospheric water transport from the tropics to the African and Asian continents. However, other climate drivers such as reorganization of marine and atmospheric circulations, tectonic, and the extent of the Northern Hemisphere ice sheet are also discussed.

scholarly journals Impact of anthropogenic activities on global land oxygen flux

2019 ◽  
Author(s):  
Xiaoyue Liu ◽  
Jianping Huang ◽  
Jiping Huang ◽  
Changyu Li ◽  
Lei Ding
Keyword(s):  
Fossil Fuel ◽  
Anthropogenic Activities ◽  
Atmospheric Oxygen ◽  
Regional Scale ◽  
Central Africa ◽  
Heterotrophic Soil Respiration ◽  
Habitable Planet ◽  
Higher Temperature ◽  
Dynamic Description ◽  
The Tropics

Abstract. Atmospheric oxygen (O2) is one of the predominant features that enable Earth as a habitable planet for active and diverse biology. However, observations since the late 1980s indicate that O2 content in the atmosphere is falling steadily at part-per-million level. Although a scientific consensus has emerged that the current decline is generally attributed to the combustion of fossil fuel, a quantitative assessment of the anthropogenic impact on the O2 cycle on both global and regional scale is currently lacking. This paper quantifies the anthropogenic and biological O2 flux over land and provides a quantitative and dynamic description of land O2 budget under impacts of human activities on grid scale. It is found that total anthropogenic O2 flux over land has risen from 35.6 Gt/yr in 2000 to 46.0 Gt/yr in 2013, while the compensation from land (11.5 Gt/yr averaged from 2000 to 2013) displays a faint increase during the same period. High anthropogenic fluxes mainly occur in Eastern Asia, India, North America and Europe caused by fossil fuel combustion and in Central Africa caused by wildfire. Due to strong heterotrophic soil respiration under higher temperature conditions, the positive O2 flux in the tropics is not significant. Instead, boreal forest and Tibetan plateau become the most important sources of atmospheric O2 in the Anthropocene. The anthropogenic oxygen consumption data are publicly available online at https://doi.org/10.1594/PANGAEA.899167.

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