The Landscape Cycle under Semi-Arid Conditions

1939 ◽  
Vol 76 (9) ◽  
pp. 402-407
Author(s):  
C. A. Cotton
Keyword(s):  
Mediterranean Region ◽  
Arid Regions ◽  
Seasonal Distribution ◽  
Rainfall Regime ◽  
Vegetative Cover ◽  
Wet Season ◽  
Arid Conditions ◽  
The Mediterranean ◽  
Semi Arid

It is difficult to draw the line between aridity and semi-aridity, just as it-is difficult to differentiate between humid and semi-arid climates as they affect the development of landscape forms. No hard and fast divisions based on rainfall figures can be adopted. Evaporation, in part controlled by temperature, and the seasonal distribution of rainfall are also important factors. “The rainfall regime is divisible”, according to. Bryan, “into the episodic and the periodic. In the episodic type rain falls in storms that are highly variable in intensity and are scattered through the year; in the periodic type precipitation is concentrated in one season, either summer or winter. In areas having the periodic type vegetation is adjusted to the wet season, and a relatively greater vegetative cover is possible with low rainfall. The Mediterranean region and California have the periodic type of rainfall, with winter maximum and mild temperatures. Thus in many sub-areas the land forms under mean annual rainfalls of 15 to 20 inches are very similar to those of humid regions, although the soils … are quite like those of other arid regions. The episodic rainfall, because of its variability in time throughout the year, is less effective in promoting growth, and the vegetative cover may be so scant with rainfalls of 5 to 7 inches that geomorphologically the region is essentially a desert. Episodic rainfall as high as 15 to 20 inches may produce steppe conditions. … In general the warmer areas have a relatively scantier vegetation with the same rainfall regime. Including this relation all varieties of hot and cold deserts or semi-arid climates are possible (2).”

Typification of the Mediterranean endemic conifer Juniperus turbinata (Cupressaceae)

Phytotaxa ◽  
2017 ◽  
Vol 302 (2) ◽  
pp. 165 ◽  
Author(s):  
PEDRO PABLO FERRER-GALLEGO ◽  
ROBERTO NAZZARO ◽  
INMACULADA FERRANDO ◽  
EMILIO LAGUNA
Keyword(s):  
North America ◽  
East Asia ◽  
Northern Hemisphere ◽  
Canary Islands ◽  
Mediterranean Region ◽  
The Mediterranean ◽  
Semi Arid

The genus Juniperus Linnaeus (1753: 1038) (Cupressaceae Gray, nom. cons.) is a major component of arid and semi-arid tree/shrub ecosystems throughout the Northern Hemisphere (Thorne 1972, Adams 2004, 2008, 2014, Farjon 2005). The genus is monophyletic (Adams 2004, 2008, 2014, Little 2006, Mao et al. 2010), and three monophyletic sections are currently recognized: J. sect. Caryocedrus Endlicher (1847: 2), with one species in the Mediterranean; J. sect. Juniperus, with nine species in East Asia and the Mediterranean plus the circumboreal J. communis Linnaeus (1753: 1040); and J. sect. Sabina Spach (1841: 291), with 56 species distributed in southwestern North America, Asia and the Mediterranean region, with outliers in Africa and the Canary Islands.

scholarly journals Indicadores Hídricos do Núcleo de Desertificação da Microrregião do Seridó Ocidental da Paraíba (Water Indicators of Desertification Nucleus in the Seridó Microregion of Paraíba State)

2015 ◽  
Vol 7 (5) ◽  
pp. 784 ◽  
Author(s):  
Hermes Alves de Almeida ◽  
Danilo Barbosa Aguiar ◽  
José Nivaldo Silva ◽  
João Damaseceno
Keyword(s):  
Water Balance ◽  
Environmental Degradation ◽  
Degradation Process ◽  
Rainfall Anomaly ◽  
Rainfall Regime ◽  
Arid Conditions ◽  
Short Rainy Season ◽  
De Se ◽  
Rainfall Patterns ◽  
Semi Arid

As condições áridas ou semiáridas são sempre associadas com a susceptibilidade ao processo de degradação de terras. Assim sendo, houve a necessidade de se estabelecer indicadores hídricos das localidades de Santa Luzia, São José do Sabugi e Várzea, pertencentes ao núcleo de desertificação da microrregião do Seridó Ocidental da Paraíba, utilizando-se índices de seca meteorológica e do balanço hídrico climatológico, sendo essas determinações os objetivos principais deste trabalho. As séries pluviais dos referidos locais foram agrupadas e analisadas usando-se critérios da estatística climatológica, sendo estabelecido o regime pluvial, o índice de anomalia de chuva (IAC), o balanço hídrico climatológico e os índices de aridez, hídrico e de umidade efetiva. Os principais resultados mostraram que o regime pluvial do referido núcleo de desertificação é extremamente irregular, assimétrico e a curta estação chuvosa, perdura por cerca de três meses (fevereiro a abril), e chove o equivalente a 65 % do total anual. O IAC mostrou ser um bom indicador da variabilidade do regime pluvial, além de detectar períodos secos ou chuvosos e estabelecer as categorias de seca meteorológica. O predomínio significativo da deficiência hídrica, em quase todos os meses do ano, contribui para a susceptibilidade ao processo de degradação ambiental na microrregião do Seridó Ocidental da Paraíba.    ABSTRACT Arid or semi-arid conditions are always associated with susceptibility to land degradation process. Therefore, it was necessary to establish indicators of water localities of Santa Luzia, São José do Sabugi and Várzea, belonging to the nucleus of desertification of micro region western of the Paraíba, using indices of dry weather and water balance these determinations are the main objectives of this work. The rainfall series from such locations were contained and analyzed being used criteria of the climatologically statistics, rainfall patterns being established, the rainfall anomaly index (IAC), the water balance and the index of aridity, water and effective moisture. The principal results showed that rainfall regime of the referred nucleus desertification is extremely irregular, asymmetric and short rainy season lasts for about three months (February-April), and it rains the equivalent of 65% of the annual. The IAC has proved to be a good indicator of the variability of rainfall patterns and to detect dry or rainy periods and establish categories of dry weather. The significant prevalence of water deficit in almost every month of the year, contributes to susceptibility to environmental degradation in the micro region of Western Seridó of Paraíba. Key-words: climate, environmental degradation, droughts indexes, aridity  

scholarly journals Impacts of the seasonal distribution of rainfall on vegetation productivity across the Sahel

2017 ◽  
Author(s):  
Wenmin Zhang ◽  
Martin Brandt ◽  
Xiaoye Tong ◽  
Qingjiu Tian ◽  
Rasmus Fensholt
Keyword(s):  
Rainfall Intensity ◽  
Arid Zone ◽  
Growing Season ◽  
Seasonal Distribution ◽  
Seasonal Rainfall ◽  
Wet Season ◽  
Rainfall Events ◽  
Heavy Rainfall Events ◽  
Semi Arid ◽  
Rainy Days

Abstract. Climate change in drylands has caused alterations in the seasonal distribution of rainfall including increased heavy rainfall events, longer dry spells, and a shifted timing of the wet season. Yet, the aboveground net primary productivity (ANPP) in drylands is usually explained by annual rainfall sums, disregarding the influence of the seasonal distribution of rainfall. This study tests the importance of seasonal rainfall metrics (onset and cessation of the wet season, number of rainy days, rainfall intensity, number of consecutive dry days and heavy rainfall events) on growing season ANPP. We focus on the Sahel and north-Sudanian region (100–800 mm year−1) and apply daily satellite based rainfall estimates (RFE-2.0) and growing season integrated NDVI (MODIS) as a proxy for ANNP over the study period 2001–2015. Growing season ANPP in the arid zone (100–300 mm year−1) was found to be rather insensitive to variations in the seasonal rainfall metrics, whereas vegetation in the semi-arid zone (300–700 mm year−1) was significantly impacted by most metrics, especially by the number of rainy days and timing (start and cessation) of the wet season. We analyzed critical breakpoints for all metrics, showing that growing season ANPP is particularly negatively impacted after > 10 consecutive dry days and that a rainfall intensity of 7 mm day−1 is detected for optimum growing season ANPP. We conclude that number of rainy days and the timing of the wet season are seasonal rainfall metrics being decisive for favorable vegetation growth in semi-arid Sahel which needs to be considered when modelling primary productivity from rainfall in the dryland's of Sahel and elsewhere.

Observational analysis of Mediterranean decadal hydroclimate variability: role of Atlantic-Mediterranean sea surface temperatures

2020 ◽  
Author(s):  
Roberto Suarez-Moreno ◽  
Richard Seager ◽  
Yochanan Kushnir
Keyword(s):  
Climate Change ◽  
North Atlantic ◽  
Mediterranean Region ◽  
Sea Surface ◽  
Wet Season ◽  
The North ◽  
Hydroclimate Variability ◽  
The North Atlantic ◽  
The Mediterranean

<p>The Mediterranean region is a semi-arid climate zone, subject to droughts, where water resources are scarce and observational data and climate models suggest a tendency towards greater aridification. Moreover, the Mediterranean region is an area of social and political instability and, in the Middle East, open warfare, which might be further stressed by climate change. The North Atlantic Oscillation (NAO) is the dominant mode of winter climate variability in the North Atlantic sector, playing the leading role in driving Mediterranean hydroclimate variability from seasonal to multidecadal timescales, whereas the influence of sea surface temperatures (SSTs) remains unclear. Nevertheless, the mechanism underlying the NAO is still under debate, and the possibility for coupled ocean-atmosphere decadal interactions, for which several mechanisms have been proposed, would support the role of SST. Based on observations and reanalysis, we conduct a statistical-observational analysis to explore the decadal drivers of Mediterranean hydroclimate variability for the winter half-year (October-to-March) wet season. Our results put forward the uneven intraseasonal influence of the decadal NAO, being the leading driver during the winter peak season (December-to-March), while decadal Atlantic-Mediterranean SST variability exhibit a consistent link for the first months of the wet season (October-to-January). These results emphasize the need to further explore the ocean-atmosphere feedback mechanisms and their possible modulations under climate change. Understanding these mechanisms is essential to improve predictability of hydroclimate in the Mediterranean region, leading to adaptation strategies that mitigate the effect of climate change on the vulnerable population.</p>

Discussion: The Significance of Terraces due to Climatic Oscillation

1945 ◽  
Vol 82 (1) ◽  
pp. 16-18 ◽  
Author(s):  
H. L. Richardson
Keyword(s):  
Arid Regions ◽  
Ice Age ◽  
Vegetative Cover ◽  
West China ◽  
Human Interference ◽  
Streams And Rivers ◽  
Climatic Oscillation ◽  
Stream Beds ◽  
Semi Arid

With regard to the relation between climatic oscillation and terrace formation, some ideas that I have collected in the course of studying accelerated (man-made) erosion, may be useful in a geo-morphological setting. Huntington’s principle and the idea I used in my paper “The Ice Age in West China” are not necessarily opposed, if one limits the application of Huntington’s principle to semi-arid regions which are just on the margin of being able to support a vegetative cover. In such regions a further decrease in precipitation, leading to serious reduction in the protection afforded by vegetation, would accelerate erosion on hillsides and steep valley floors, and this in turn would lead to deposition of spoil on more gently sloping valley floors lower down. A further oscillation of the climate, in the direction of increasing rainfall, would restore the vegetative cover, reduce erosion, reduce the load in the rivers, and allow downcutting to continue. But a still further increase in precipitation might be expected to increase erosion of the type associated with landslips and flooded streams and rivers; once more increased load will be swept down from the steeper hills and stream-beds to the lower and gentler slopes of the rivers, where it will be deposited. In other words, one may say that there is a level of precipitation, probably a moderately low one, at which (apart from human interference) there is a close vegetative cover and geological erosion is at a minimum; any appreciable departure from this level of precipitation in either direction will cause increased geological erosion in the upper courses of streams, and hence increased deposition in their lower courses.

scholarly journals Morphophysiological aspects of ornamental sunflowers cultivated in different growing seasons under semi-arid conditions

2022 ◽  
Vol 26 (4) ◽  
pp. 299-305
Author(s):  
Sheila D. P. da Silva ◽  
Gracielle P. de Souza ◽  
Agnaldo R. de M. Chaves ◽  
Marcelle A. da Silva ◽  
Rafaela R. de Souza ◽  
...  
Keyword(s):  
Gas Exchange ◽  
Arid Regions ◽  
Block Design ◽  
Growing Season ◽  
Climatic Conditions ◽  
Growing Seasons ◽  
Arid Conditions ◽  
Randomized Block Design ◽  
Leaf Surface Area ◽  
Semi Arid

ABSTRACT Knowledge of how climatic conditions affect plant morphophysiology is essential for understanding how to manage the growth cycles of different crops. The aim of this study was to evaluate the effects of the growing seasons in a semi-arid area on the morphophysiological variables of ornamental sunflower plants. The experiment was carried out in a randomized block design in a split-plot arrangement with four replicates. Six cultivars (‘Bonito de Outono Sortido’, ‘Sol Noturno’, ‘Sol Vermelho’, ‘Jardim Amarelo Alto’, ‘Girassol F1 Sunbright Supreme’ and ‘Girassol F1 Vincents Choice’) were evaluated in the main plots and two different growing seasons (GS) in the subplots (GS1 - warm climate and GS2 - mild climate). Evaluations of gas exchange, chlorophyll indices, and leaf surface area were carried out at the reproductive stage (R5.5). The cultivation of ornamental sunflowers in semi-arid regions was significantly affected by the growing season. Changes in gas exchange variables and the morphophysiology of ornamental sunflower plants in the two growing seasons reflected the high phenotypic plasticity characteristic of this species. The cultivation of ornamental sunflowers under semi-arid conditions in the growing season, when air temperature and solar radiation are high, could be limited due to elevated transpiration rates. Therefore, it is recommended that they are grown mainly during the moderate climatic season in semi-arid regions.

Stimulation of Soybean (Glycine max) growth and yield using Bradyrhizobium inoculants in the semi-arid environment of Botswana

2021 ◽  
Author(s):  
M. Mosupiemang ◽  
K. Bareeleng ◽  
M.S. Chiduwa and O.O. Molosiwa
Keyword(s):  
Arid Regions ◽  
Crop Yields ◽  
Dry Weight ◽  
Arid Environment ◽  
Growth And Yield ◽  
Arid Conditions ◽  
Inoculant Strain ◽  
Uninoculated Control ◽  
Bradyrhizobium Spp ◽  
Semi Arid

Background: Crop yields in the semi-arid regions are low due to climatic and soil related constraints.Soybean as one of the most important legume crops grown worldwide, has a role to contribute nitrogen to improve nutrient poor soils in Africa. A study was conducted to examine the effects of Bradyrhizobium spp inoculations on the growth and yield of soybean varieties in a glasshouse.Method: The study was arranged in a randomized complete block factorial design, with factor A being two soybean varieties (Bimha and Status) while factor B was inoculation using four Bradyrhizobium strains and the uninoculated control. Results: Bradyrhizobium inoculation significantly (P less than 0.001)affected days to 50% flowering, days to emergence, nodule number, root dry weight and grain yield and yield traits. Parameters that were affected by both inoculant strain and variety included days to 50% flowering, days to emergence, number of pods per plant, pod weight and number of seeds per pod. The interaction effect of variety and Bradyrhizobium inoculant strain was observed only on number of pods per plants. Our study shows that soybean grows well when inoculated with Bradyrhizobium inoculants, in semi-arid conditions of Botswana.

scholarly journals Diversity of endophytic fungal community associated to the roots of Argania spinosa (L.) Skeels growing in the arid and semi-arid regions of Algeria

2019 ◽  
Vol 114 (1) ◽  
pp. 103
Author(s):  
Abdallah NOUI ◽  
Abdelkader SAADI ◽  
Abdul SHAKOOR ◽  
Abdelaziz MEROUANE ◽  
Nassima MOSTEFA DELLA ◽  
...  
Keyword(s):  
Arid Regions ◽  
Haplotype Diversity ◽  
Molecular Study ◽  
Harsh Environments ◽  
Argania Spinosa ◽  
Operational Taxonomic Units ◽  
Arid Conditions ◽  
Argan Tree ◽  
Z Scores ◽  
Semi Arid

<p>Current study identified endophytic fungi<em> </em>associated<em> </em>to<em> Argania spinosa</em> (argan) roots and revealed diverse haplotype diversity by the sequencing of internal transcribed spacer (ITS). 586 operational taxonomic units were identified and these operational taxonomic units (OTUs) could be assigned to fungal functional diversity such as endophytes, ectomycorrhiza and putative pathogens. Ascomycota phylum was abundant. Beside Ascomycota phylum, Basidiomycota members were also found in argan roots. <em>Geopora, Sebacina, Knufia, Tomentella, Penicillim</em> had high relative abundance. Our results highlighted a non-nested assemblage of fungi. Current non-nested findings also confirm that fungi have similar pattern found in other habitats. Pairwise analysis mirrored segregation pattern between same and different functional fungal group. Fungi in semi-arid conditions are non-randomly structured. Members of Ascomycota phylum had high Z-scores. This is the first molecular study conducted in arid and semi-arid habitats of Algeria aiming to identify fungi associated with roots in argan tree. Given the fact that deserts are among harsh environments and fungi associated to desert plants may have implications for biodiversity and ecosystem functioning.</p>

scholarly journals Economic indicators of nitrogen fertilization in sunflower cultivars

2020 ◽  
Vol 36 (6) ◽  
Author(s):  
Almir Rogerio Evangelista de Souza ◽  
Ênio Gomes Flôr Souza ◽  
Francilene de Lima Tartaglia ◽  
Allysson Pereira dos Santos ◽  
Aurélio Paes Barros Júnior ◽  
...  
Keyword(s):  
Arid Regions ◽  
Production Costs ◽  
Economic Indicators ◽  
Agricultural Crops ◽  
Arid Conditions ◽  
The World ◽  
Effective Decision ◽  
Net Margin ◽  
Effective Decision Making ◽  
Semi Arid

Sunflower is one of the most important oilseeds in the world. However, cultivation in semi-arid regions requires analysis of production costs and profitability, ensuring effective decision-making, focused on farming procedures and techniques. In two agricultural crops, 2016 and 2017, experiments were conducted to evaluate the economic indicators of sunflower cultivars (‘Aguará 06’, ‘Altis 99’, ‘Multissol’ and ‘BRS 122’) submitted to nitrogen (N) doses (0; 30; 60; 90 and 120 kg ha-1) via fertirrigation under semi-arid conditions. The net margin corresponded to the increase of N doses, reaching a maximum net margin in the 2016 harvest of R$ 366.89 ha-1 at the dose of 81 kg ha-1 of N for ‘BRS 122’; R$ 577.41 ha-1 with 118 kg ha-1 of N for ‘Multissol’; and for ‘Aguará 06’ (R$ 2,124.00 ha-1) and ‘Altis 99’ (R$ 976.66 ha-1) at the dose of 120 kg ha-1 of N. In the 2017 harvest, ‘BRS 122’ obtained R$ 190.90 ha-1 in the dose of 83 kg ha-1 of N and ‘Multissol’ reached R$ 657.50 in the dose of 85 kg ha-1 of N; the cultivars ‘Aguará 06’ (R$ 1,078.00 ha-1) and ‘Altis 99’ (R$ 957.14 ha-1) in the dose of 120 kg ha-1 of N. The rate of return and the profitability index were positive for all cultivars in both crops.

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