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 Long-Term historical and Projected Herbivore Population Dynamics in Ngorongoro Crater, Tanzania

2019 ◽  
Author(s):  
Joseph O. Ogutu ◽  
Patricia D Moehlman ◽  
Hans-Peter Piepho ◽  
Victor A Runyoro ◽  
Michael B Coughenour ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Population Size ◽  
Dry Season ◽  
Climate Change Scenarios ◽  
Wet Season ◽  
Large Herbivore ◽  
Herbivore Species ◽  
Dry Seasons ◽  
Wet And Dry Seasons

The Ngorongoro Crater is an intact caldera with an area of approximately 310 km2. Long term records on herbivore populations, vegetation and rainfall made it possible to analyze historic and project future herbivore population dynamics. In 1974 there was a perturbation in that resident Maasai and their livestock were removed from the Crater. Vegetation structure changed in 1967 from predominately short grassland to mid and tall grasses dominating in 1995. Even with a change in grassland structure, total herbivore biomass remained relatively stable from 1963 to 2012, implying that the crater has a stable multi-herbivore community. However, in 1974, Maasai pastoralists were removed from the Ngorongoro Crater and there were significant changes in population trends for some herbivore species. Buffalo, elephant and ostrich numbers increased significantly during 1974-2012. The zebra population was stable from 1963 to 2012 whereas numbers of other eight species declined substantially between 1974 and 2012 relative to their peak numbers during 1974-1976. Numbers of Grant’s and Thomson’s gazelles, eland, kongoni, waterbuck (wet season only) declined significantly in the Crater in both seasons after 1974. Wildebeest numbers decreased in the Crater between 1974 and 2012 but this decrease was not statistically significant. In addition, some herbivore species were consistently more abundant inside the Crater during the wet than the dry season. This pattern was most evident for the large herbivore species requiring bulk forage, comprising buffalo, eland, and elephant. Analyses of rainfall indicated that there was a persistent annual cycle of 4.83 years. Herbivore population size was correlated with rainfall in both the wet and dry seasons. The relationships established between the time series of historic animal counts in the wet and dry seasons and lagged wet and dry season rainfall series were used to forecast the likely future trajectories of the wet and dry season population size for each species under three alternative climate change scenarios.

scholarly journals Ground data confirm warming and drying are at a critical level for forest survival in western equatorial Africa

2019 ◽  
Author(s):  
Emma R Bush ◽  
Kathryn Jeffery ◽  
Nils Bunnefeld ◽  
Caroline Tutin ◽  
Ruth Musgrave ◽  
...  
Keyword(s):  
Tropical Forests ◽  
Meteorological Data ◽  
Climatic Variability ◽  
Central Africa ◽  
Dry Season ◽  
Annual Rainfall ◽  
Evergreen Forests ◽  
Total Annual Rainfall ◽  
Equatorial Africa

Background.The humid tropical forests of Central Africa influence weather worldwide and play a major role in the global carbon cycle. However they are also an ecological anomaly, with evergreen forests dominating the western equatorial region despite less than 2000mm total annual rainfall. Meteorological data for Central Africa are notoriously sparse and incomplete and there are substantial issues with satellite-derived data because of inability to ground-truth estimates and persistent cloudiness. Long-term climate observations are urgently needed to verify regional climate and vegetation models, shed light on the mechanisms that drive climatic variability and assess the viability of evergreen forests in equatorial Africa under future climate scenarios. Methods. We have the rare opportunity to analyse a 34-year dataset of rainfall and temperature (and shorter periods of absolute humidity, wind speed, solar radiation and aerosol optical depth) from Lopé National Park, a long-term ecological research site in western equatorial Africa. We used linear mixed models and spectral analyses to assess seasonal and inter-annual variation, long-term trends and oceanic influences on local weather patterns. Results. Lopé’s weather is characterised by a light-deficient, cool, long dry season. Long-term climatic means have changed significantly over the last three decades, with warming occurring at a rate of 0.23°C per decade (minimum daily temperature) and drying at a rate of 50mm per decade (total annual rainfall). Inter-annual variability is highly influenced by sea surface temperatures of the major oceans. In El Niño years Lopé experiences both higher temperatures and less rainfall with increased contrast between wet and dry seasons. Lopé rainfall observations lend support for the role of the Atlantic cold tongue in “dry” models of climate change in the region. Conclusions. Dry season cloud in western equatorial Africa plays a key role in reducing evaporative demand during seasonal drought and maintaining evergreen tropical forests despite relatively low annual rainfall. In the context of a rapidly warming and drying climate, urgent research is needed into the sensitivity of clouds to ocean temperatures and the viability of humid forests in this dry region should the clouds disappear.

scholarly journals Rare ground data confirm significant warming and drying in western equatorial Africa

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e8732 ◽  
Author(s):  
Emma R. Bush ◽  
Kathryn Jeffery ◽  
Nils Bunnefeld ◽  
Caroline Tutin ◽  
Ruth Musgrave ◽  
...  
Keyword(s):  
Rainfall Variability ◽  
Climatic Variability ◽  
Central Africa ◽  
Dry Season ◽  
Annual Rainfall ◽  
Weather Patterns ◽  
Evergreen Forests ◽  
Total Annual Rainfall ◽  
Equatorial Africa

Background The humid tropical forests of Central Africa influence weather worldwide and play a major role in the global carbon cycle. However, they are also an ecological anomaly, with evergreen forests dominating the western equatorial region despite less than 2,000 mm total annual rainfall. Meteorological data for Central Africa are notoriously sparse and incomplete and there are substantial issues with satellite-derived data because of persistent cloudiness and inability to ground-truth estimates. Long-term climate observations are urgently needed to verify regional climate and vegetation models, shed light on the mechanisms that drive climatic variability and assess the viability of evergreen forests under future climate scenarios. Methods We have the rare opportunity to analyse a 34 year dataset of rainfall and temperature (and shorter periods of absolute humidity, wind speed, solar radiation and aerosol optical depth) from Lopé National Park, a long-term ecological research site in Gabon, western equatorial Africa. We used (generalized) linear mixed models and spectral analyses to assess seasonal and inter-annual variation, long-term trends and oceanic influences on local weather patterns. Results Lopé’s weather is characterised by a cool, light-deficient, long dry season. Long-term climatic means have changed significantly over the last 34 years, with warming occurring at a rate of +0.25 °C per decade (minimum daily temperature) and drying at a rate of −75 mm per decade (total annual rainfall). Inter-annual climatic variability at Lopé is highly influenced by global weather patterns. Sea surface temperatures of the Pacific and Atlantic oceans have strong coherence with Lopé temperature and rainfall on multi-annual scales. Conclusions The Lopé long-term weather record has not previously been made public and is of high value in such a data poor region. Our results support regional analyses of climatic seasonality, long-term warming and the influences of the oceans on temperature and rainfall variability. However, warming has occurred more rapidly than the regional products suggest and while there remains much uncertainty in the wider region, rainfall has declined over the last three decades at Lopé. The association between rainfall and the Atlantic cold tongue at Lopé lends some support for the ‘dry’ models of climate change for the region. In the context of a rapidly warming and drying climate, urgent research is needed into the sensitivity of dry season clouds to ocean temperatures and the viability of humid evergreen forests in this dry region should the clouds disappear.

scholarly journals Ground data confirm warming and drying are at a critical level for forest survival in western equatorial Africa

2019 ◽  
Author(s):  
Emma R Bush ◽  
Kathryn Jeffery ◽  
Nils Bunnefeld ◽  
Caroline Tutin ◽  
Ruth Musgrave ◽  
...  
Keyword(s):  
Tropical Forests ◽  
Meteorological Data ◽  
Climatic Variability ◽  
Central Africa ◽  
Dry Season ◽  
Annual Rainfall ◽  
Evergreen Forests ◽  
Total Annual Rainfall ◽  
Equatorial Africa

Background.The humid tropical forests of Central Africa influence weather worldwide and play a major role in the global carbon cycle. However they are also an ecological anomaly, with evergreen forests dominating the western equatorial region despite less than 2000mm total annual rainfall. Meteorological data for Central Africa are notoriously sparse and incomplete and there are substantial issues with satellite-derived data because of inability to ground-truth estimates and persistent cloudiness. Long-term climate observations are urgently needed to verify regional climate and vegetation models, shed light on the mechanisms that drive climatic variability and assess the viability of evergreen forests in equatorial Africa under future climate scenarios. Methods. We have the rare opportunity to analyse a 34-year dataset of rainfall and temperature (and shorter periods of absolute humidity, wind speed, solar radiation and aerosol optical depth) from Lopé National Park, a long-term ecological research site in western equatorial Africa. We used linear mixed models and spectral analyses to assess seasonal and inter-annual variation, long-term trends and oceanic influences on local weather patterns. Results. Lopé’s weather is characterised by a light-deficient, cool, long dry season. Long-term climatic means have changed significantly over the last three decades, with warming occurring at a rate of 0.23°C per decade (minimum daily temperature) and drying at a rate of 50mm per decade (total annual rainfall). Inter-annual variability is highly influenced by sea surface temperatures of the major oceans. In El Niño years Lopé experiences both higher temperatures and less rainfall with increased contrast between wet and dry seasons. Lopé rainfall observations lend support for the role of the Atlantic cold tongue in “dry” models of climate change in the region. Conclusions. Dry season cloud in western equatorial Africa plays a key role in reducing evaporative demand during seasonal drought and maintaining evergreen tropical forests despite relatively low annual rainfall. In the context of a rapidly warming and drying climate, urgent research is needed into the sensitivity of clouds to ocean temperatures and the viability of humid forests in this dry region should the clouds disappear.

Temporal variations of CH4/CO2/CO fluxes in the central Amazon rainforest

2020 ◽  
Author(s):  
Shujiro Komiya ◽  
Jost Lavric ◽  
David Walter ◽  
Santiago Botia ◽  
Alessandro Araujo ◽  
...  
Keyword(s):  
Amazon Basin ◽  
Temporal Variations ◽  
Dry Season ◽  
Amazon Rainforest ◽  
Eddy Covariance Method ◽  
Co Concentration ◽  
Dry Seasons ◽  
Co Concentrations ◽  
Wet And Dry Seasons

&lt;p&gt;Amazon rainforests and soils contain large amounts of carbon, which is under pressure from ongoing climate and land use change in the Amazon basin. It is estimated that methane (CH&lt;sub&gt;4&lt;/sub&gt;), an important greenhouse gas, is largely released from the flooded wetlands of the Amazon, but the trends and balances of CH&lt;sub&gt;4 &lt;/sub&gt;in the Amazon rainforest are not yet well understood. In addition, the change in atmospheric CH&lt;sub&gt;4&lt;/sub&gt; concentration is strongly associated with a change in carbon monoxide (CO) concentration, often caused by the human-induced combustion of biomass that usually peaks during dry season. Understanding the long-term fluctuations in the fluxes of greenhouse gases in the Amazon rainforest is essential for improving our understanding of the carbon balance of the Amazon rainforest.&lt;/p&gt;&lt;p&gt;Since March 2012, we have continuously measured atmospheric CO&lt;sub&gt;2&lt;/sub&gt;/CH&lt;sub&gt;4&lt;/sub&gt;/CO concentrations at five levels (79, 53, 38, 24, and 4 m a.g.l.) using two wavelength-scanned cavity ring-down spectroscopy analyzers (G1301 and G1302, Picarro Inc., USA), which are automatically calibrated on site every day. In addition, we measured the CO&lt;sub&gt;2&lt;/sub&gt; flux by the eddy covariance method at the same tower. We estimated the CO&lt;sub&gt;2&lt;/sub&gt;/CH&lt;sub&gt;4&lt;/sub&gt;/CO fluxes by combining the vertical profile of the CO&lt;sub&gt;2&lt;/sub&gt;/CH&lt;sub&gt;4&lt;/sub&gt;/CO concentrations with the flux gradient method. Our results generally show no major difference in CO&lt;sub&gt;2&lt;/sub&gt; flux between the wet and dry seasons except for year 2017, when an elevated CO&lt;sub&gt;2&lt;/sub&gt; uptake was documented during the dry season despite the lowest precipitation between 2014 and 2018. The CH&lt;sub&gt;4&lt;/sub&gt; flux showed the largest CH&lt;sub&gt;4&lt;/sub&gt; emission during the dry season in year 2016. Further results will be analyzed and discussed in the presentation.&lt;/p&gt;

Attachment of oral bacteria to titanium surfaces: An SEM study

1994 ◽  
Vol 52 ◽  
pp. 468-469
Author(s):  
J. E. Laffoon ◽  
R. L. Anderson ◽  
J. C. Keller ◽  
C. D. Wu-Yuan
Keyword(s):  
Technical Problem ◽  
Titanium Implant ◽  
Oral Bacteria ◽  
Bacterial Cells ◽  
Thin Sections ◽  
Surface Ultrastructure ◽  
Sem Study ◽  
Key Factor ◽  
Titanium Surfaces

Titanium (Ti) dental implants have been used widely for many years. Long term implant failures are related, in part, to the development of peri-implantitis frequently associated with bacteria. Bacterial adherence and colonization have been considered a key factor in the pathogenesis of many biomaterial based infections. Without the initial attachment of oral bacteria to Ti-implant surfaces, subsequent polymicrobial accumulation and colonization leading to peri-implant disease cannot occur. The overall goal of this study is to examine the implant-oral bacterial interfaces and gain a greater understanding of their attachment characteristics and mechanisms. Since the detailed cell surface ultrastructure involved in attachment is only discernible at the electron microscopy level, the study is complicated by the technical problem of obtaining titanium implant and attached bacterial cells in the same ultra-thin sections. In this study, a technique was developed to facilitate the study of Ti implant-bacteria interface.Discs of polymerized Spurr’s resin (12 mm x 5 mm) were formed to a thickness of approximately 3 mm using an EM block holder (Fig. 1). Titanium was then deposited by vacuum deposition to a film thickness of 300Å (Fig. 2).

Designing a CRM Framework for online & offline sports footwear retailers

2015 ◽  
Vol 3 (1) ◽  
Author(s):  
Rodrigo Cueva ◽  
Guillem Rufian ◽  
Maria Gabriela Valdes
Keyword(s):  
Environmental Changes ◽  
Customer Relationship ◽  
Business Strategies ◽  
Economic Sectors ◽  
Running Shoes ◽  
Brick And Mortar ◽  
Key Factor ◽  
On Line ◽  
The Impact

The use of Customer Relationship Managers to foster customers loyalty has become one of the most common business strategies in the past years.  However, CRM solutions do not fill the abundance of happily ever-after relationships that business needs, and each client’s perception is different in the buying process.  Therefore, the experience must be precise, in order to extend the loyalty period of a customer as much as possible. One of the economic sectors in which CRM’s have improved this experience is retailing, where the personalized attention to the customer is a key factor.  However, brick and mortar experiences are not enough to be aware in how environmental changes could affect the industry trends in the long term.  A base unified theoretical framework must be taken into consideration, in order to develop an adaptable model for constructing or implementing CRMs into companies. Thanks to this approximation, the information is complemented, and the outcome will increment the quality in any Marketing/Sales initiative. The goal of this article is to explore the different factors grouped by three main domains within the impact of service quality, from a consumer’s perspective, in both on-line and off-line retailing sector.  Secondly, we plan to go a step further and extract base guidelines about previous analysis for designing CRM’s solutions focused on the loyalty of the customers for a specific retailing sector and its product: Sports Running Shoes.

scholarly journals Effect of ecological and conventional managements on soil enzymatic activities in coffee agroecosystems

2018 ◽  
Vol 48 (4) ◽  
pp. 420-428
Author(s):  
Johana Juliet Caballero Vanegas ◽  
Karen Bibiana Mejía Zambrano ◽  
Lizeth Manuela Avellaneda-Torres
Keyword(s):  
Sustainable Management ◽  
Climatic Variability ◽  
Agricultural Practices ◽  
Enzymatic Activities ◽  
Acid And Alkaline Phosphatase ◽  
Dry Seasons ◽  
Synthetic Fertilizers ◽  
Coffee Agroecosystems ◽  
Alkaline And Acid Phosphatase

ABSTRACT Understanding the impacts of agricultural practices on soil quality indicators, such as enzymatic activities, is of great importance, in order to advance in their diagnosis and sustainable management. This study aimed to evaluate the effect of ecological and conventional agricultural managements on enzymatic activities of a soil under coffee agroecosystems. The enzymatic activities were associated with the biogeochemical cycles of nitrogen (urease and protease), phosphorus (acid and alkaline phosphatase) and carbon (β-glucosidase), during the rainy and dry seasons. Physical-chemical soil proprieties were also assessed and related to resilience scores linked to the climatic variability reported for the areas under study. The activities of urease, alkaline and acid phosphatase and ß-glucosidase were statistically higher in ecological agroecosystems than in conventional ones. This may be attributed to the greater application of organic waste in the ecological environment, as well as to the absence of pesticides and synthetic fertilizers, which allow better conditions for the microbial activity. The resilience scores to the climate variability that showed the highest correlations with the assessed enzymatic activities were: the farmers' knowledge on soil microorganisms, non-use of pesticides and synthetic fertilizers and non-dependence on external supplies. It was concluded that the enzymatic activities are modified by the management systems, being specifically favored by the ecological management. This agroecosystem, in the long term, ensures an efficient use of the soil resources, with a lower degradation and contamination.

scholarly journals Confronting ethical challenges in long-term research programs in the tropics

2021 ◽  
Vol 255 ◽  
pp. 108933
Author(s):  
Reinmar Seidler ◽  
Richard B. Primack ◽  
Varun R. Goswami ◽  
Sarala Khaling ◽  
M. Soubadra Devy ◽  
...  
Keyword(s):  
Ethical Challenges ◽  
Research Programs ◽  
The Tropics
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