Influence of rainfall and grazing on belowground biomass dynamics in a dry tropical savanna

1992 ◽  
Vol 70 (9) ◽  
pp. 1885-1890 ◽  
Author(s):  
C. B. Pandey ◽  
J. S. Singh
Keyword(s):  
Rainy Season ◽  
Soil Depth ◽  
Rainfall Variability ◽  
Grazing Intensity ◽  
Belowground Biomass ◽  
Tropical Savanna ◽  
Rainfall Events ◽  
Seasonally Dry ◽  
Belowground Component

Root biomass and its variation with time and soil depth were studied in ungrazed and grazed treatments, in a seasonally dry tropical savanna. A greater proportion of belowground biomass was located in the 0 – 10 cm soil depth in the rainy season compared with the summer season. In contrast, in the 10 – 50 cm soil profile, belowground biomass was greater in summer than in the rainy season. Peak belowground biomass in ungrazed savanna was not correlated to the rainfall in the early part of the rainy season, but it was correlated to total rainfall received in the later part of rainy season. Apparently the belowground component responds quickly to the rainfall events and generates growth pulses in the aboveground vegetation. Peak canopy biomass increased rapidly with the increase in peak belowground biomass and then plateaued, indicating a greater potential for accumulation of biomass belowground than aboveground. Grazing reduced belowground biomass by 41 – 55%. Maximum reduction occurred in the heavily grazed savanna. Peak belowground biomass was inversely related to grazing intensity. Key words: belowground biomass, grazing intensity, phased root growth, rainfall variability, tropical savanna.

Fate of urea-nitrogen from cattle urine in a pasture-crop sequence in a seasonally dry tropical environment

1985 ◽  
Vol 36 (6) ◽  
pp. 809 ◽  
Author(s):  
I Vallis ◽  
DCI Peake ◽  
RK Jones ◽  
RL McCown
Keyword(s):  
Soil Depth ◽  
Soil Surface ◽  
Dry Season ◽  
Wet Season ◽  
Mineral N ◽  
Seasonally Dry ◽  
15N Urea ◽  
Almost All ◽  
Crop Sequence

The fate of urea-N in cattle urine applied during the dry season (in August) to the pasture phase of a pasture-crop sequence at Katherine, N.T., was investigated. Cattle urine labelled with 15N-urea was applied to three sets of microplots to measure the following parameters: (a) amount and distribution of 15N remaining in the microplots during the remainder of the dry season with 0, 0.5, 1.0 and 5.0 t ha-1 of pasture residues present initially; (b) the effect of placing the urine 5 cm below the soil surface on the amount of 15N remaining during the dry season; (c) uptake of 15N by the pasture during the early part of the wet season (October to December) and uptake by sorghum sown directly into the killed pasture in January. Residual 15N in the surface soil (0-15 cm) after the sorghum crop was also measured. Of the applied 15N, 26% was lost after 1 day, 32% after 7 days and 46% after 63 days. Losses were not affected by the amount of pasture residues on the microplots when the urine was applied. Almost all of the I5N remaining in the microplots was in the 0-7.5-cm layer of soil, and 65-75% of this was mineral N. The dry-season losses of 15N were presumably through volatilization of ammonia, because leaching was absent and no loss of 15N occurred when the urine was placed 5 cm below the soil surface. Pasture growth killed at the end of December contained 6.2% of the applied 15N, the sorghum crop recovered only a further 2.1%, and after harvest of the sorghum crop the 0-15.0-cm layer of soil contained 23%. Thus about half of the 15N remaining in the soil-plant system to the 15.0 cm soil depth at the end of the dry season disappeared during the following wet season, either as a gaseous loss or by leaching deeper into the soil.

scholarly journals Watershed-Based Rainfall variability and trends of extreme rainfall events in South East Awash Basin, Ethiopia

2019 ◽  
Vol 6 (6) ◽  
pp. 5524-5530
Author(s):  
Yonas Tadesse Alemu
Keyword(s):  
Coefficient Of Variation ◽  
Rainy Season ◽  
Rainfall Variability ◽  
Extreme Rainfall ◽  
Annual Rainfall ◽  
Extreme Rainfall Events ◽  
Rainfall Events ◽  
Precipitation Distribution ◽  
Precipitation Concentration ◽  
Dire Dawa

This study presents analysis of Rainfall variability and trends of extreme rainfall events in the Oda Gunufeta -Cherecha -Dechatu watershed, Awash Drainage Basin, Eastern Ethiopia. The study employed the coefficient of variation and the Precipitation Concentration Index (PCI) as statistical descriptors of rainfall variability. The indices at the five stations were subjected to non-parametric Mann-Kendall test to detect the trend over the period between 1985 to 2014. The results of the study revealed that, the watershed experiences moderate inter-annual rainfall variability. The Belg rainfall shows high variability than Kiremt rainfall. Highest Belg & Kiremt rainfall variability is observed in Dire Dawa with coefficient of variation of 46% and 40% respectively. The annual PCI for the watershed in all the stations under investigation during the record periods showed that 100% of the years for which the annual PCI was estimated fell within the irregular precipitation distribution range or high precipitation concentration. The irregular precipitation distribution also extended to all the stations in short rainy season (Belg rainfall) and in two stations in the main rainy season (Kiremt season). With regard to the rainfall trend, the annual rainfall has showed a negative trend in most of the stations for the period 1985-2014. The Mann–Kendall trend test during the Kiremt season shows a positive trend in Dengego, Dire Dawa, Combolcha and Haramaya and the increasing tendency is significant at p<0.1 in Degego, p<0.05 in Dire Dawa, p <0.05 in Combolcha and p <0.01 in Haramaya. The heavy rainfall events, the 90th & 95th percentiles, in all the five stations showed an increasing pattern but except in Combolcha the trends are not statistically significant. This implies that the watershed has been under increased rainfall intensity and this in turn has the potential cause for high risk of flood occurrences.

scholarly journals Foliar analysis in experimentally grown Lacatan bananas in relation to leaf production and bunch weight.

1962 ◽  
Vol 10 (2) ◽  
pp. 118-126 ◽  
Author(s):  
W.J. Brezowsky ◽  
J. Van Biesen
Keyword(s):  
Rainy Season ◽  
Foliar Analysis ◽  
Depressing Effect ◽  
Leaf Production ◽  
Positive Effect ◽  
Leaf N

Foliar analyses from October to April (the drier part of the year) showed a positive effect of an increased potash application on leaf K, and a depressing effect on leaf Mg. Both these effects were statistically insignificant just before and during the period when most of the plants started to shoot. There was no significant effect of increased N applications on leaf N, except in the early part of the rainy season. Increased K also had a significant effect on bunch weight, hand weight and the number of hands per stem.-Cameroons Develop. Corp. (Abstract retrieved from CAB Abstracts by CABI’s permission)

Culturable autotrophic ammonia-oxidizing bacteria population and nitrification potential in a sheep grazing intensity gradient in a grassland on the Loess Plateau of Northwest China

2011 ◽  
Vol 91 (6) ◽  
pp. 925-934 ◽  
Author(s):  
Tianzeng Liu ◽  
Zhibiao Nan ◽  
Fujiang Hou
Keyword(s):  
Loess Plateau ◽  
Soil Depth ◽  
Grazing Intensity ◽  
Northwest China ◽  
Ammonia Oxidizing Bacteria ◽  
Stocking Rate ◽  
The Loess Plateau ◽  
Soil Microbial ◽  
Nitrification Potential ◽  
Dry Soil

Liu, T., Nan, Z. and Hou, F. 2011. Culturable autotrophic ammonia-oxidizing bacteria population and nitrification potential in a sheep grazing intensity gradient in a grassland on the Loess Plateau of Northwest China. Can. J. Soil Sci. 91: 925–934. Grazing is known to enhance the activity of soil microbial communities in many types of grasslands; however, the potential impacts of rotational grazing activity on soil microbial functional groups remain poorly understood. We investigated the effects of 9 yr of rotational grazing by livestock on culturable autotrophic ammonia-oxidizing bacteria (AOB) population size, nitrification potential and soil properties in a semi-arid grassland of the Loess Plateau in Northwest China. Three stocking rate treatments of 2.7, 5.3 and 8.7 wether lambs ha−1were evaluated in geographically separated paddocks. Grazing increased nitrification potential and culturable AOB populations compared with ungrazed treatments. Ammonia-oxidizing bacteria populations increased from 155 bacteria g−1dry soil with 0 sheep ha−1to 16 218 bacteria g−1dry soil with 8.7 sheep ha−1. Grazing led to an increase in population of AOB at 0–10 cm soil depth, but had no effect on AOB at 10–20 cm soil depth. Nitrification potential increased from 1.21 mg NO3-N kg−1soil d−1in ungrazed treatments to 2.86 mg NO3-N kg−1soil d−1at the highest stocking rate. Soil ammonium and nitrate concentrations increased; however, total soil nitrogen and soil moisture content decreased with increased stocking rate for both sampling depths (0–10 cm and 10–20 cm). Soil organic matter was not affected by grazing treatments. Soil nitrification potential and the size of culturable AOB populations were dependent on grazing intensity, soil depth and season. This information is potentially important for the optimal selection of stocking rate for grazed ecosystems.

Soil macrofauna diversity and population dynamics in Indian Himalayan agroecosystems

Soil Research ◽  
2020 ◽  
Vol 58 (7) ◽  
pp. 636
Author(s):  
Madhuri Pant ◽  
G. C. S. Negi ◽  
Pramod Kumar
Keyword(s):  
Soil Fertility ◽  
Rainy Season ◽  
Soil Depth ◽  
Soil Macrofauna ◽  
Crop Fields ◽  
Β Diversity ◽  
Top Soil ◽  
Himalayan Mountain ◽  
Irrigated Wheat ◽  
Taxonomic Groups

Soil macrofauna diversity in Himalayan mountain agroecosystems has received negligible attention despite people’s dependence on soil fertility that determines crop yield for their sustenance. This study was carried out with the objective to determine differences in soil macrofauna taxonomic groups and abundance with soil depth (0–30 cm) in irrigated and non-irrigated wheat and rice crops of two dominant Himalayan mountain agroecosystems. At both the sites, a total of 11 macrofauna groups and 23 families were recorded. Macrofauna population across both crop seasons for non-irrigated fields was significantly greater (P &lt; 0.05) than in irrigated fields. Macrofauna population significantly differed (P &lt; 0.001) with soil depth and significantly declined with increasing soil depth (P &lt; 0.001). The top soil (0–10 cm depth) contributed over 80% of the total macrofauna population. Macrofauna diversity in non-irrigated fields (H′ = 2.10) was greater than in irrigated fields (H′ = 1.86), but β diversity was greater in irrigated fields (1.67 vs 1.76). The two agroecosystem types significantly differed (P &lt; 0.05) with soil depth and crop season. On the basis of presence or absence, the macrofauna groups were categorised as (i) present in soil year-round but exhibiting high density during warm and wet rainy season and (ii) present in soil only during the warm and wet rainy season. The non-irrigated fields had greater abundance of Coleoptera, Dermaptera, Hemiptera and Isoptera than the irrigated fields. This study highlights that the Himalayan mountain crop fields host a rather diverse and abundant macro-invertebrate community that should be efficiently used to promote soil fertility.

scholarly journals The 2018 Long Rainy Season in Kenya: Hydrological Changes and Correlated Land Subsidence

2020 ◽  
Vol 12 (9) ◽  
pp. 1390 ◽  
Author(s):  
Ashraf Rateb ◽  
ElSayed Hermas
Keyword(s):  
Land Subsidence ◽  
Rainy Season ◽  
Active Faults ◽  
Wet Season ◽  
Rainfall Events ◽  
Environmental Disasters ◽  
Hydrological Changes ◽  
The Stability ◽  
Sbas Insar ◽  
Scientific Attention

The wettest 2018 long rainy season (March to May (MAM)) resulted in daily intensive rainfall events in East Africa that have seriously affected the environment and economy in many countries. Land subsidence is one of the environmental disasters that has occurred due to the long rainy season in Kenya for many years. However, it has received limited scientific attention. In this paper, we incorporate hydrological (soil moisture active–passive (SMAP) and loading models) and geodetic data (global positioning system (GPS) and interferometric synthetic aperture radar (InSAR)) to study hydrological changes and their associated subsidence potential in Kenya. Results show that widespread subsidence of more than 20 mm was associated with the MAM season in Kenya during 2018, based on SBAS InSAR measurements. The high values of land subsidence were well correlated with the areas of intense flooding during the MAM season. The widespread subsidence during the wet season has implications for the stability of the earth’s surface during the season rather than creating the possibility of potential stresses along active faults. These stresses may trigger seismicity that is expected to pose risks to urban features. The results of the current study can help governmental authorities to adopt proper urban planning that avoids or minimizes the risks of land subsidence in the areas of sinkholes.

scholarly journals Investigation of dominant hydrological processes in a tropical catchment in a monsoonal climate via the downward approach

2006 ◽  
Vol 10 (5) ◽  
pp. 769-782 ◽  
Author(s):  
L. Montanari ◽  
M. Sivapalan ◽  
A. Montanari
Keyword(s):  
Overland Flow ◽  
Soil Depth ◽  
Rainfall Variability ◽  
Sensitivity Analyses ◽  
Wet Season ◽  
Ungauged Catchments ◽  
Progressive Development ◽  
Total Runoff ◽  
High Storage Capacity ◽  
Streamflow Response

Abstract. This study explores the dominant processes that may be responsible for the observed streamflow response in Seventeen Mile Creek, a tropical catchment located in a monsoonal climate in Northern Territory, Australia. The hydrology of this vast region of Australia is poorly understood due to the low level of information and gauging that are available. Any insights that can be gained from the few well gauged catchments that do exist can be valuable for predictions and water resource assessments in other poorly gauged or ungauged catchments in the region. To this end, the available rainfall and runoff data from Seventeen Mile Creek catchment are analyzed through the systematic and progressive development and testing of rainfall-runoff models of increasing complexity, by following the "downward" or "top-down" approach. This procedure resulted in a multiple bucket model (4 buckets in parallel). Modelling results suggest that the catchment's soils and the landscape in general have a high storage capacity, generating a significant fraction of delayed runoff, whereas saturation excess overland flow occurs only after heavy rainfall events. The sensitivity analyses carried out with the model with regard to soil depth and temporal rainfall variability revealed that total runoff from the catchment is more sensitive to rainfall variations than to soil depth variations, whereas the partitioning into individual components of runoff appears to be more influenced by soil depth variations. The catchment exhibits considerable inter-annual variability in runoff volumes and the greatest determinant of this variability turns out to be the seasonality of the climate, the timing of the wet season, and temporal patterns of the rainfall. The water balance is also affected by the underlying geology, nature of the soils and the landforms, and the type, density and dynamics of vegetation, although information pertaining to these is lacking.

scholarly journals Comparative Study on Soil Microbial Biomass in Tarai and Hill Sal (Shorearobusta Gaertn.) Forests of Tropical Region in Eastern Nepal

2020 ◽  
Vol 19 (1) ◽  
pp. 16-25
Author(s):  
Krishna Prasad Bhattarai ◽  
Tej Narayan Mandal
Keyword(s):  
Microbial Biomass ◽  
Comparative Study ◽  
Rainy Season ◽  
Turnover Rate ◽  
Soil Microbial Biomass ◽  
Soil Depth ◽  
Soil Samples ◽  
Tropical Region ◽  
Soil Microbial ◽  
Sal Forest

A comparative study was conducted to investigate the effect of altitudinal variation and seasonality on soil microbial biomass carbon (MB-C), nitrogen (MB-N), and phosphorus (MB-P) between Tarai Sal forest (TSF) and Hill Sal forest (HSF) of the tropical region in eastern Nepal. Soil microbial biomass was estimated by chloroform fumigation - extraction method in summer, rainy and winter seasons in the upper (0-15 cm) soil depth in both forests. Pre-conditioned soil samples were saturated with purified liquid chloroform, represented fumigated sample. Another set of soil samples without using chloroform, represented unfumigated samples and soil biomass was estimated from these samples. MB-C, MB-N, and MB-P were higher by 66%, 31%, and 9%, respectively, in HSF than TSF. Distinct seasonality was observed in soil microbial biomass. It was maximum in summer and minimum in rainy season in both the forest stands. The value decreased from summer to rainy season by 46 to 67% in HSF and by 32 to 80% in TSF. Higher soil microbial biomass in the summer season may be due to its accumulation in soil when the plant growth and nutrient demand are minimal. Analysis of variance suggested that MB-C, MB-N, and MB-P were significantly different for both sites and seasons (P < 0.001). Soil organic carbon, TN, and TP were positively correlated with MB-C, MB-N, and MB-P in both the forests. In conclusion, the higher value of soil microbial biomass in HSF may be due to the higher concentration of soil organic matter and decreasing turnover rate of microbial biomass due to higher altitude. On the other hand, the lower value of microbial biomass at TSF may indicate its fast turnover rate due to lowland tropics to enhance the nutrient cycling process.

scholarly journals Climate change effects on early stages of Quercus ariifolia (Fagaceae), an endemic oak from seasonally dry forests of Mexico

2019 ◽  
Author(s):  
Ernesto I. Badano ◽  
Francisco A. Guerra-Coss ◽  
Erik J. Sánchez-Montes de Oca ◽  
Carlos I. Briones-Herrera ◽  
Sandra M. Gelviz-Gelvez
Keyword(s):  
Climate Change ◽  
Functional Traits ◽  
Rainy Season ◽  
Extinction Risk ◽  
Seedling Emergence ◽  
Dry Forest ◽  
Tree Seedlings ◽  
Dry Forests ◽  
Tree Recruitment ◽  
Seasonally Dry

Background and Aims: Tree recruitment in seasonally dry forests occurs during the rainy season. However, higher temperatures and reduced rainfalls are expected in these ecosystems because of climate change. These changes could induce drought conditions during the rainy season and affect tree recruitment. Plants subjected to thermal or water stress often display morphological and physiological shifts addressed to prioritize their survival. If recently emerged tree seedlings display these responses, this could improve their development during the rainy season and increase their survival chances. Our aim was to test whether recently emerged oak seedlings display these responses.Methods: We performed a field experiment with Quercus ariifolia, an oak species endemic to seasonally dry forests of central Mexico. At the beginning of the rainy season (September 2016), we sowed acorns of this species in control plots under the current climate and plots in which climate change was simulated by increasing temperature and reducing rainfall (CCS plots). Seedling emergence and survival were monitored every seven days during the rainy season (until January 2017). At the end of the experiment, we measured several functional traits on surviving seedlings and compared them between controls and CCS plots.Key results: Higher temperature and lower rainfall generated water shortage conditions in CCS plots. This did not affect emergence of seedlings but reduced their survival. Seedlings that survived in CCS plots displayed shifts in their functional traits, which matched with those of plants subjected to thermal and water stress.Conclusions: Our results suggest that climate change can increase the extinction risk of Q. ariifolia in seasonally dry forest of Mexico by reducing the survival of its offspring. Nevertheless, the results also suggest that seedlings developed under climate change conditions can display functional shifts that could confer them tolerance to increased drought.

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