Patterns and implications of Plant-soil δ13C and δ15N values in African savanna ecosystems

2010 ◽  
Vol 73 (1) ◽  
pp. 77-83 ◽  
Author(s):  
Lixin Wang ◽  
Paolo D'Odorico ◽  
Lydia Ries ◽  
Stephen A. Macko
Keyword(s):  
Woody Plants ◽  
Rainfall Regime ◽  
Vegetation Composition ◽  
Wet Season ◽  
Δ13c And Δ15n ◽  
Plant Soil ◽  
Climatic Scenarios ◽  
Use Efficiency ◽  
The Relationship ◽  
Composition Changes

Southern African savannas are mixed plant communities where C3 trees co-exist with C4 grasses. Here foliar δ15N and δ13C were used as indicators of nitrogen uptake and of water use efficiency to investigate the effect of the rainfall regime on the use of nitrogen and water by herbaceous and woody plants in both dry and wet seasons. Foliar δ15N increased as aridity rose for both C3 and C4 plants for both seasons, although the magnitude of the increase was different for C3 and C4 plants and for two seasons. Soil δ15N also significantly increased with aridity. Foliar δ13C increased with aridity for C3 plants in the wet season but not in the dry season, whereas in C4 plants the relationship was more complex and non-linear. The consistently higher foliar δ15N for C3 plants suggests that C4 plants may be a superior competitor for nitrogen. The different foliar δ13C relationships with rainfall may indicate that the C3 plants have an advantage when competing for water resources. The differences in water and nitrogen use likely collectively contribute to the tree–grass coexistence in savannas. Such differences facilitate interpretations of palaeo-vegetation composition variations and help predictions of vegetation composition changes under future climatic scenarios.

scholarly journals Optimizing Grain Yield and Water Use Efficiency Based on the Relationship between Leaf Area Index and Evapotranspiration

Agriculture ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 313
Author(s):  
Guoqiang Zhang ◽  
Bo Ming ◽  
Dongping Shen ◽  
Ruizhi Xie ◽  
Peng Hou ◽  
...  
Keyword(s):  
Grain Yield ◽  
Water Use Efficiency ◽  
Leaf Area Index ◽  
Water Use ◽  
Plant Density ◽  
Maize Yield ◽  
Area Index ◽  
Irrigation Level ◽  
Use Efficiency ◽  
The Relationship

Achieving optimal balance between maize yield and water use efficiency is an important challenge for irrigation maize production in arid areas. In this study, we conducted an experiment in Xinjiang China in 2016 and 2017 to quantify the response of maize yield and water use to plant density and irrigation schedules. The treatments included four irrigation levels: 360 (W1), 480 (W2), 600 (W3), and 720 mm (W4), and five plant densities: 7.5 (D1), 9.0 (D2), 10.5 (D3), 12.0 (D4), and 13.5 plants m−2 (D5). The results showed that increasing the plant density and the irrigation level could both significantly increase the leaf area index (LAI). However, LAI expansion significantly increased evapotranspiration (ETa) under irrigation. The combination of irrigation level 600 mm (W3) and plant density 12.0 plants m−2 (D4) produced the highest maize yield (21.0–21.2 t ha−1), ETa (784.1–797.8 mm), and water use efficiency (WUE) (2.64–2.70 kg m−3), with an LAI of 8.5–8.7 at the silking stage. The relationship between LAI and grain yield and evapotranspiration were quantified, and, based on this, the relationship between water use and maize productivity was analyzed. Moreover, the optimal LAI was established to determine the reasonable irrigation level and coordinate the relationship between the increase in grain yield and the decrease in water use efficiency.

An ecological explanation for hyperallometric scaling of reproduction

2021 ◽  
Author(s):  
Tomos Potter ◽  
Anja Felmy
Keyword(s):  
Body Size ◽  
Reproductive Output ◽  
Resource Competition ◽  
Natural Populations ◽  
Scaling Exponent ◽  
Wild Populations ◽  
Wet Season ◽  
Size Dependent ◽  
In The Wild ◽  
The Relationship

AbstractIn wild populations, large individuals have disproportionately higher reproductive output than smaller individuals. We suggest an ecological explanation for this observation: asymmetry within populations in rates of resource assimilation, where greater assimilation causes both increased reproduction and body size. We assessed how the relationship between size and reproduction differs between wild and lab-reared Trinidadian guppies. We show that (i) reproduction increased disproportionately with body size in the wild but not in the lab, where effects of resource competition were eliminated; (ii) in the wild, the scaling exponent was greatest during the wet season, when resource competition is strongest; and (iii) detection of hyperallometric scaling of reproduction is inevitable if individual differences in assimilation are ignored. We propose that variation among individuals in assimilation – caused by size-dependent resource competition, niche expansion, and chance – can explain patterns of hyperallometric scaling of reproduction in natural populations.

Analyses on salt-marsh vegetation composition changes in the Venice lagoon in the last twenty years

2021 ◽  
Author(s):  
Zhicheng Yang ◽  
Sonia Silvestri ◽  
Marco Marani ◽  
Andrea D'Alpaos
Keyword(s):  
Salt Marsh ◽  
Random Forest ◽  
Sea Level ◽  
Dominant Species ◽  
Venice Lagoon ◽  
Vegetation Composition ◽  
Fractional Abundance ◽  
Soft Classification ◽  
Vegetation Species ◽  
Composition Changes

<p>Coastal salt-marshes are important eco-geomorphic features of coastal landscapes providing valuable ecosystem services, but unfortunately, they are among the most vulnerable ecosystems around the world. Their survival is mainly threatened by sea-level rise, wave erosion and human pressure. Halophytic vegetation distribution and dynamics control salt-marsh erosional and depositional patterns, critically determining marsh survival through complex bio-morphodynamic feedbacks. Although a number of studies have proposed species-classification methods and analyzed halophytic vegetation species distribution, our knowledge of the temporal evolution of species composition remains limited. To fill these gaps and better describe vegetation composition changes in time, we developed a novel classification method which is based on the Random Forest soft classification algorithm, and applied the method to two multi-spectral images of the San Felice marsh in the Venice lagoon (Italy) acquired in 2001 and 2019. The Random Forest soft classification achieves high accuracy (0.60 < <em>R</em><sup>2</sup> < 0.96) in the estimation of the fractional abundance of each species in both images. We also determined the local dominant species, i.e. the species with the highest fractional abundance in each pixel. Our observations on the dominant species in 2001 and 2019 show that: 1) the area dominated by <em>Juncus</em> and <em>Spartina</em> decreased dramatically in such period; 2) the area dominated by <em>Limonium </em>almost maintained constant; 3) a noticeable decrease in the bare-soil area occurred due to the encroachment of <em>Salicornia</em> between 2001 and 2019. We also noticed that the probability distribution of the dominant patch area of each species is consistent with a power-law distribution, with different slopes for different vegetation species at different times. We suggest that vegetation composition changes are related to sea-level rise and to the species-specific inundation tolerance.</p>

scholarly journals ICHTHYOFAUNA IN THE INNER CONTINENTAL SHELF NEXT TO THE PARANAGUÁ ESTUARINE COMPLEX, SOUTHERN BRAZIL

2021 ◽  
Vol 46 (4) ◽  
pp. 1-13
Author(s):  
Cesar SANTOS ◽  
Roberto SCHWARZ JUNIOR ◽  
Helen Audrey PICHLER ◽  
Olímpio Rafael CARDOSO ◽  
Marcelo Renato LAMOUR ◽  
...  
Keyword(s):  
Continental Shelf ◽  
Fish Assemblages ◽  
Fish Fauna ◽  
Temporal Variations ◽  
Otter Trawl ◽  
Rainfall Regime ◽  
Wet Season ◽  
Environmental Characteristics ◽  
The North ◽  
Inner Continental Shelf

The composition and structure of fish assemblages in the inner continental shelf of the Paraná State are affected by cold fronts and the rainfall regime. Data from fishing activities in this region, as well as the analysis of environmental characteristics, are the main tools available for understanding fish dynamics, under influence of increasing human activities. In order to better understand patterns and temporal variations in fish assemblages in the inner continental shelf of the Paraná State, a total of 24 double trawls were performed with an otter trawl between August 2000 and July 2001, in two sampling areas, the North area in front of the northern mouth of the Paranaguá Estuary Complex, and the South area, in front of the Leste beach. A total of 45,277 fish specimens belonging to 35 families and 97 species were caught. Sciaenidae was the most abundant family, with 37.1% of the total number of individuals caught, and with the highest richness (18 species). Statistical analyses evidenced significant differences in environmental characteristics and in fish fauna, and that both areas disturbances were observed in the fish assemblages during the dry and wet season, being more intense in the Southern area, disturbances that would be related to the shrimp fishing present in the two areas sampled in this study.

scholarly journals Water stress coefficient determined by orbital remote sensing techniques

2020 ◽  
Vol 24 (12) ◽  
pp. 847-853
Author(s):  
Élvis da S. Alves ◽  
Roberto Filgueiras ◽  
Lineu N. Rodrigues ◽  
Fernando F. da Cunha ◽  
Catariny C. Aleman
Keyword(s):  
Remote Sensing ◽  
Water Stress ◽  
Irrigation Management ◽  
Simple Algorithm ◽  
Landsat 8 ◽  
Stress Coefficient ◽  
Use Efficiency ◽  
Remote Sensing Techniques ◽  
Water Stress Coefficient ◽  
The Relationship

ABSTRACT In regions where the irrigated area is increasing and water availability is reduced, such as the West of the Bahia state, Brazil, the use of techniques that contribute to improving water use efficiency is paramount. One of the ways to improve irrigation is by improving the calculation of actual evapotranspiration (ETa), which among other factors is influenced by soil drying, so it is important to understand this relationship, which is usually accounted for in irrigation management models through the water stress coefficient (Ks). This study aimed to estimate the water stress coefficient (Ks) through information obtained via remote sensing, combined with field data. For this, a study was carried out in the municipality of São Desidério, an area located in western Bahia, using images of the Landsat-8 satellite. Ks was calculated by the relationship between crop evapotranspiration and ETa, calculated by the Simple Algorithm for Evapotranspiration Retrieving (SAFER). The Ks estimated by remote sensing showed, for the development and medium stages, average errors on the order of 5.50%. In the final stage of maize development, the errors obtained were of 23.2%.

Nitrate pollution in groundwater and strategies to reduce pollution

2002 ◽  
Vol 45 (9) ◽  
pp. 29-35 ◽  
Author(s):  
R.K. Shrestha ◽  
J.K. Ladah
Keyword(s):  
Cropping System ◽  
Sweet Pepper ◽  
World Health ◽  
Wet Season ◽  
Tropical Ecosystem ◽  
Mineral N ◽  
Use Efficiency ◽  
Low Levels ◽  
Indigofera Tinctoria ◽  
N Use

The input-intensive rainfed tropical ecosystem, where wet season (WS) rice (Oriza sativa L.) – dry season (DS) diversified high-value upland crops like vegetables predominate, has resulted in a problem of a large leakage of N into the environment, thereby polluting the water. Excessive use of N fertilizer in high-value crops grown in DS is economically motivated. Out of twenty water sources evaluated in a watershed with a total area of 265 ha located in Magnuang, Ilocos Norte, Philippines, twelve had near or above the World Health Organization’s (WHO) NO3-N limit for drinking water of 10 ppm. Soil mineral N (upper 100 cm) observed in seven rice-sweet pepper (Capsicum annuum L.) farmers’ fields ranged from 111 to 694 kg ha-1 which decreased by 10 to 68% in plots with dry-to-wet (DTW) crops like indigo, indigo+mungo and corn. In fallow plots where mineral N was either maintained or increased, it showed movement to lower soil profiles demonstrating NO3 leaching without a crop. On average, maize (Zea mays L.) captured 176 kg N ha-1 and indigo (Indigofera tinctoria L.) 194 kg N ha-1. In both fallow and planted plots, mineral N declined to low levels at 100% water-filled pore spaces (WFPS) before rice transplanting. A strategy for including indigo plus maize as a N-catch crop is proposed to decrease NO3 leaching and maximize N use efficiency in a rice-sweet pepper cropping system.

Simulation Study about Impact of Building Density on Heat Island Effect

2014 ◽  
Vol 590 ◽  
pp. 353-357
Author(s):  
Xiao Yu Luo ◽  
Jian Ge ◽  
Yun Zhang
Keyword(s):  
Thermal Conductivity ◽  
Rapid Development ◽  
Decision Makers ◽  
Management Decision ◽  
Heat Island ◽  
Building Density ◽  
Land Use Efficiency ◽  
Island Effect ◽  
Use Efficiency ◽  
The Relationship

Along with the rapid development of urbanization, high density city is becoming more and more common. The dense buildings cause the high intensity of heat island effect, resulting in a large amount of energy consumption. In this research the relationship between the heat island effect and the building density has been studied by CFD software with other factors such as the building height and construction shape unchanged. Through a series of simulation and data analysis it is revealed that the effect of building density on the thermal conductivity is obvious. And the study put forward the measure to alleviate the effects of the thermal conductivity by controlling building density in a certain percentage under the premise of maintaining the land use efficiency. This result can provide scientific references for planners, architects, and government management decision makers.

scholarly journals Assessing the relationship between diet and size-at-age in Pacific halibut (Hippoglossus stenolepis) using δ13C and δ15N analysis

2019 ◽  
Vol 76 (12) ◽  
pp. 2326-2331
Author(s):  
Nathan Wolf ◽  
Sarah R. Webster ◽  
Jeffery M. Welker ◽  
Bradley P. Harris
Keyword(s):  
North Pacific Ocean ◽  
Isotope Analysis ◽  
Δ13c And Δ15n ◽  
Pacific Halibut ◽  
Hippoglossus Stenolepis ◽  
Dietary Strategy ◽  
Mean Size ◽  
Intermediate Size ◽  
Size At Age ◽  
The Relationship

The ecological mechanisms driving an observed decline in the mean size-at-age of adult Pacific halibut (Hippoglossus stenolepis) in the eastern North Pacific Ocean have yet to be defined. Here, we present the results of a study designed to investigate the relationship between one potential mechanism — diet — and size-at-age using carbon and nitrogen stable isotope analysis. Our results indicate significant differences in the skeletal muscle δ13C and δ15N values between size-at-age categories for each sex, with larger-size-at-age fish consuming diets with higher δ15N values, indicating higher trophic level feeding. Analysis of Bayesian standard ellipse areas showed that for females, intermediate size-at-age categories have the largest dietary range. For males, the largest dietary range was observed in the largest size-at-age category. Our results suggest a size-based stratification in dietary strategy for Pacific halibut with implications for observed declines in size-at-age.

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