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| 1 | Demographic variation and habitat specialization of tree species in a diverse tropical forest of Cameroon显示文摘Background: Many tree species in tropical forests have distributions tracking local ridge-slope-valley topography.Previous work in a 50-ha plot in Korup National Park, Cameroon, demonstrated that 272 species, or 63% of those tested, were significantly associated with topography.Methods: We used two censuses of 329,000 trees ≥1 cm dbh to examine demographic variation at this site that would account for those observed habitat preferences. We tested two predictions. First, within a given topographic habitat, species specializing on that habitat(‘residents') should outperform species that are specialists of other habitats(‘foreigners'). Second, across different topographic habitats, species should perform best in the habitat on which they specialize(‘home') compared to other habitats(‘away'). Species' performance was estimated using growth and mortality rates.Results: In hierarchical models with species identity as a random effect, we found no evidence of a demographic advantage to resident species. Indeed, growth rates were most often higher for foreign species. Similarly, comparisons of species on their home vs. away habitats revealed no sign of a performance advantage on the home habitat.Conclusions: We reject the hypothesis that species distributions along a ridge-valley catena at Korup are caused by species differences in trees ≥1 cm dbh. Since there must be a demographic cause for habitat specialization, we offer three alternatives. First, the demographic advantage specialists have at home occurs at the reproductive or seedling stage, in sizes smaller than we census in the forest plot. Second, species may have higher performance on their preferred habitat when density is low, but when population builds up, there are negative density-dependent feedbacks that reduce performance. Third, demographic filtering may be produced by extreme environmental conditions that we did not observe during the census interval. | David Kenfack George B Chuyong Richard Condit Sabrina E Russo Duncan W Thomas | 2014 | Forest Ecosystems2014，1，4： | 1 |
| 2 | Contribution of GIS to Hydromorphometric Characterization of the Nkoup Watershed(Nun Plain-Cameroon)显示文摘The Nkoup watershed(10°35’-10°47’E and 5°27’-5°42’N)is a volcanic zone situated in Nun Plain West Cameroon.The high fertility of the soils makes it a strategic agropastoral area where water resources are heavily exploited and used for several purposes.Due to human activities,soils and water resources are deteriorating,giving birth to water pollution and hydromorphological hazards.This work aims to determine the hydromorphometric parameters of the Nkoup watershed so that the data obtained help in the sustainable management of water resources and conservation of soil.To achieve this aim,various data were collected from DEM dataset derived from SRTM and processed in specialized software(QGIS and ArGIS).The simplified hydrological balance was calculated using the upstream approach.The Nkoup watershed has:Axial length L_(ax)=25.8 km,Axial Width W_(ax)=11.1 km,Perimeter P=132.6 km,Area A=173.7 km^(2),Average Altitude Ha=1726.3 m,Compactness Index Icomp=2.8,Relief ratio Rr=3.9 m/km,Circularity ratio Rc=0.1,Elongation ratio R=0.1,Drainage texture ratio Rt=0.6,Drainage density Dd=0.5 km/km^(2).Stream Frequency Fs=0.4,Channel Sinuosity Index CSI=0.8,Stream gradient Sg=0.6 and global slope Index Ig=6.8 m/km.The specific height Difference Ds=89.4 m shows moderate relief.The precipitation and evapotranspiration are unevenly distributed.With P=187.7 mm/an,ETP=953.4 mm/an,Q=4.2 m3/s,R=762.5 mm/an,ETR=832.3 mm/an and I=282.9 mm/an.The Nkoup,36.9 km long,has a sinuous aspect due to the low slope and the high CSI.The piezometric levels vary according to the seasons and the groundwater flow follows the N-S direction as surface flow. | Paul Bertrand Tsopkeng Josiane Feugue Kenfack David Guimolaire Nkouathio Charles Antoine Basseka Leonel Koudjou Tsague | 2023 | Advances in Geological and Geotechnical Engineering Research2023，5，3： | 0 |
| 3 | Lineament characteristics using gravity data in the Garoua Zone,North Cameroon: Natural risks implications显示文摘The Garoua Zone in North Cameroon, the subject of this study, is known to have undergone tectonic movements during the Cretaceous, but the zone's structural data remain poorly known.This study exploits the Bouguer anomaly to improve knowledge of Garoua tectonics structures.In order to characterize these structures, two methods are used: Euler's deconvolution method and the method of the horizontal gradient of the vertical derivative.Superposition of the Euler's solutions map for index N=1 with the map from the horizontal gradient of the vertical derivative method allows determination of gravimetric lineaments, interpreted as faults or as linear contacts, from which we deduce a structural map of the study area.Based on this map, we identify sixteen lineaments, of which we count eight as linear contacts and eight as faults.Among the faults, we denote one of depth between 4 and 8 km, five faults of depth ranging between 8 and 13 km, and two faults of depths between 13 and 36 km.Analysis of these faults shows that the seven deepest faults might present a natural risk in our study area.For purposes of civil protection, such deep faults should be monitored and taken into consideration in the implementation of large public works.The structural map, established herein from data on the in-depth extension of each fault, thus increases scientific knowledge in the area that can be used to site public works in ways that reduce risk. | Kokea Ariane Darolle Fofie Fidèle Koumetio Jean Victor Kenfack David Yemele | 2019 | Earth and Planetary Physics2019，3，1： | 0 |
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