Effects of fire regimes on herbaceous biomass and nutrient dynamics in the Brazilian savanna

2013 ◽  
Vol 22 (3) ◽  
pp. 368 ◽  
Author(s):  
Immaculada Oliveras ◽  
Sergio T. Meirelles ◽  
Valter L. Hirakuri ◽  
Cenira R. Freitas ◽  
Heloisa S. Miranda ◽  
...  
Keyword(s):  
Aboveground Biomass ◽  
Nutrient Dynamics ◽  
Community Dynamics ◽  
Fire Regime ◽  
Dry Season ◽  
Brazilian Savanna ◽  
Nutrient Concentrations ◽  
Total Biomass ◽  
Long Term Effects ◽  
Wet Season

This study explores the long-term effects of fire treatments on biomass and nutrient pools in an open savanna from Central Brazil. Treatments included early, middle and late dry season burns every 2 years, a middle dry season burn every 4 years, and protection from fire on five 4-ha plots. We quantified aboveground biomass of graminoids and forbs/sub-shurbs, and their nutrient concentrations and stocks in both dry and wet seasons, and below-ground biomass down to 30-cm depth. We found strong differences between wet and dry season, with biomass and nutrient concentrations being highest in the wet season, across all fire treatments. Fire treatments had significant effects on plant nutrient stocks and root distribution, although total biomass was not affected. Concentrations of the most volatile nutrients (N, S, K and P) were higher in the herbaceous aboveground biomass of the quadrennial and the unburnt plots, suggesting that increases in fire frequency would reduce the amount of nutrients in aboveground biomass and increase the concentration of fine roots at the soil surface. Results highlight the role of fire in maintaining community dynamics in the Brazilian savanna. Overall, the quadrennial burn appears to be the optimal fire regime in open Cerrado vegetation.

scholarly journals Seasonal changes in water quality and macrophytes and the impact of cattle on tropical floodplain waterholes

2012 ◽  
Vol 63 (9) ◽  
pp. 788 ◽  
Author(s):  
N. E. Pettit ◽  
T. D. Jardine ◽  
S. K. Hamilton ◽  
V. Sinnamon ◽  
D. Valdez ◽  
...  
Keyword(s):  
Water Quality ◽  
Seasonal Changes ◽  
Aquatic Macrophyte ◽  
Plant Cover ◽  
Critical Role ◽  
Dry Season ◽  
Nutrient Concentrations ◽  
Wet Season ◽  
Dry Tropics ◽  
The Impact

The present study indicates the critical role of hydrologic connectivity in floodplain waterholes in the wet–dry tropics of northern Australia. These waterbodies provide dry-season refugia for plants and animals, are a hotspot of productivity, and are a critical part in the subsistence economy of many remote Aboriginal communities. We examined seasonal changes in water quality and aquatic plant cover of floodplain waterholes, and related changes to variation of waterhole depth and visitation by livestock. The waterholes showed declining water quality through the dry season, which was exacerbated by more frequent cattle usage as conditions became progressively drier, which also increased turbidity and nutrient concentrations. Aquatic macrophyte biomass was highest in the early dry season, and declined as the dry season progressed. Remaining macrophytes were flushed out by the first wet-season flows, although they quickly re-establish later during the wet season. Waterholes of greater depth were more resistant to the effects of cattle disturbance, and seasonal flushing of the waterholes with wet-season flooding homogenised the water quality and increased plant cover of previously disparate waterholes. Therefore, maintaining high levels of connectivity between the river and its floodplain is vital for the persistence of these waterholes.

Nutrient cycling differs between cropped soils with century-old and recently pyrolyzed biochar

2021 ◽  
Author(s):  
Victor Burgeon ◽  
Julien Fouché ◽  
Sarah Garré ◽  
Ramin Heidarian-Dehkordi ◽  
Gilles Colinet ◽  
...  
Keyword(s):  
Nutrient Cycling ◽  
Soil Solution ◽  
Nutrient Dynamics ◽  
Chemical Properties ◽  
Crop Productivity ◽  
Nutrient Concentrations ◽  
Soil Productivity ◽  
Long Term Effects ◽  
Mitigation And Adaptation

<p>The amendment of biochar to soils is often considered for its potential as a climate change mitigation and adaptation tool through agriculture. Its presence in tropical agroecosystems has been reported to positively impact soil productivity whilst successfully storing C on the short and long-term. In temperate systems, recent research showed limited to no effect on productivity following recent biochar addition to soils. Its long-term effects on productivity and nutrient cycling have, however, been overlooked yet are essential before the use of biochar can be generalized.</p><p>Our study was set up in a conventionally cropped field, containing relict charcoal kiln sites used as a model for century old biochar (CoBC, ~220 years old). These sites were compared to soils amended with recently pyrolyzed biochar (YBC) and biochar free soils (REF) to study nutrient dynamics in the soil-water-plant system. Our research focused on soil chemical properties, crop nutrient uptake and soil solution nutrient concentrations. Crop plant samples were collected over three consecutive land occupations (chicory, winter wheat and a cover crop) and soil solutions gathered through the use of suctions cups inserted in different horizons of the studied Luvisol throughout the field.</p><p>Our results showed that YBC mainly influenced the soil solution composition whereas CoBC mainly impacted the total and plant available soil nutrient content. In soils with YBC, our results showed lower nitrate and potassium concentrations in subsoil horizons, suggesting a decreased leaching, and higher phosphate concentrations in topsoil horizons. With time and the oxidation of biochar particles, our results reported higher total soil N, available K and Ca in the topsoil horizon when compared to REF, whereas available P was significantly smaller. Although significant changes occurred in terms of plant available nutrient contents and soil solution nutrient concentrations, this did not transcend in variations in crop productivity between soils for neither of the studied crops. Overall, our study highlights that young or aged biochar behave as two distinct products in terms of nutrient cycling in soils. As such the sustainability of these soils differ and their management must therefore evolve with time.</p>

Different nutrient use strategies of expansive grasses Calamagrostis epigejos and Arrhenatherum elatius

Biologia ◽  
2012 ◽  
Vol 67 (4) ◽  
Author(s):  
Petr Holub ◽  
Ivan Tůma ◽  
Jaroslav Záhora ◽  
Karel Fiala
Keyword(s):  
Aboveground Biomass ◽  
Nutrient Release ◽  
Control Treatment ◽  
Grass Species ◽  
Nutrient Concentrations ◽  
Total Biomass ◽  
Growing Seasons ◽  
Nutrient Use ◽  
Calamagrostis Epigejos ◽  
Arrhenatherum Elatius

AbstractEnhanced nitrogen (N) levels accelerate expansion of Calamagrostis epigejos and Arrhenatherum elatius, highly aggressive expanders displacing original dry acidophilous grassland vegetation in the Podyjí National Park (Czech Republic). We compared the capability of Calamagrostis and Arrhenatherum under control and N enhanced treatments to (i) accumulate N and phosphorus (P) in plant tissues, (ii) remove N and P from above-ground biomass during senescence and (iii) release N and P from plant material during decomposition of fresh formed litter. In control treatment, significantly higher amounts of total biomass and fresh aboveground litter were observed in Calamagrostis than in Arrhenatherum. Contrariwise, nutrient concentrations were significantly higher (11.6–14.3 mg N g−1 and 2.3 mg P g−1) in Arrhenatherum peak aboveground biomass than in Calamagrostis (8.4–10.3 mg N g−1 and 1.6–1.7 mg P g−1). Substantial differences between species were found in resorption of nutrients, mainly P, at the ends of growing seasons. While P concentrations in Arrhenatherum fresh litter were twice and three times higher (1.6–2.5 mg P g−1) than in Calamagrostis (0.7–0.8 mg P g−1), N concentrations were nearly doubled in Arrhenatherum (13.1–15.6 mg N g−1) in comparison with Calamagrostis (7.4–8.7 mg N g−1). Thus, the nutrients (N and mainly P) were retranslocated from the aboveground biomass of Calamagrostis probably more effectively in comparison with Arrhenatherum at the end of the growing season. On the other hand, Arrhenatherum litter was decomposed faster and consequently nutrient release (mainly N and P) was higher in comparison with Calamagrostis which pointed to different growth and nutrient use strategies of studied grass species.

Agronomic studies on soybean (Glycine max (L.) Merrill) in the dry season of the tropics. II. Interaction of sowing date and sowing density

1991 ◽  
Vol 42 (7) ◽  
pp. 1093 ◽  
Author(s):  
JD Mayers ◽  
RJ Lawn ◽  
DE Byth
Keyword(s):  
Biomass Production ◽  
Seed Yield ◽  
Management Practices ◽  
Interaction Analysis ◽  
Sowing Date ◽  
Dry Season ◽  
High Yield ◽  
Total Biomass ◽  
Wet Season ◽  
Precocious Flowering

An analysis was undertaken of the development, growth and seed yield of irrigated soybean crops grown during the dry season in the semi-arid tropics of north-western Australia, to establish whether constraints to seed yield induced by precocious flowering could be overcome agronomically by manipulating sowing date and/or sowing density. Three agronomically improved cultivars and a later-flowering landrace cultivar were tested using irrigation, fertility and pest management practices designed to minimize constraints to yield. Maximum seed yields were 3.5-4.0 t ha-1, with large genotype x sowing date x sowing density interaction. Analysis of vegetative growth showed that higher sowing densities stimulated more rapid leaf area development and earlier canopy closure, and enhanced total biomass production. However, very high sowing densities were needed to maximize yields of most genotypes, while lodging precluded high yield being realized from the greater biomass production of high density sowings of the landrace genotype. Delaying sowing from April to June delayed flowering, increased biomass production and marginally enhanced yields, but not sufficiently to offset potential problems caused by maturation into hot dry conditions prior to the wet season. It was concluded that agronomic strategies alone were insufficient to overcome the constraints to yield of present soybean genotypes in the dry season.

Seasonal variations in the water quality of six tropical micro- and mesotidal estuaries along the central west coast of India

2018 ◽  
Vol 69 (9) ◽  
pp. 1418 ◽  
Author(s):  
Lina L. Fernandes ◽  
Pratima M. Kessarkar ◽  
Suresh Suja ◽  
Durbar Ray ◽  
Mithila Bhat
Keyword(s):  
West Coast ◽  
Nutrient Dynamics ◽  
Nutrient Concentrations ◽  
Wet Season ◽  
Salinity Stratification ◽  
West Coast Of India ◽  
Estuarine Mixing ◽  
Run Off ◽  
Water Columns ◽  
Mixing Diagrams

Seasonal nutrient dynamics were investigated in four rivers with a microtidal range (Terekhol, Chapora, Sal and Talpona rivers) and were compared with those of two rivers with a mesotidal range (Zuari and Mandovi rivers) along the central west coast of India. Rainfall and freshwater discharge during the wet season led to salinity stratification of the water columns at the mouths of these rivers. Nutrient concentrations in all rivers were higher during the wet season than in the dry season due to considerable land run-off. Based on the estuarine mixing diagrams of the nutrients with regard to salinity, the mesotidal rivers showed greater flushing capacity and acted as corridors for the passage of nutrients between the estuary and open ocean. Conversely, of the microtidal rivers, the Terekhol and Chapora seemed to retain nutrients, whereas there was no indication of the presence of a nutrient sink or source in the Talpona River. The Sal River was eutrophic with high nutrient levels and acted as a source of phosphorus and nitrogen. Thus, the present study clearly illustrates the important role played by minor river estuaries in modifying nutrient concentrations during their transport from rivers to coastal waters and vice versa.

scholarly journals The Influence of Seasonal Water Level Fluctuations on the Soil Nutrients in a Typical Wetland Reserve in Poyang Lake, China

2021 ◽  
Vol 13 (7) ◽  
pp. 3846
Author(s):  
Shuangshuang Zhang ◽  
Jin Wei ◽  
Yiping Li ◽  
Maoqing Duan ◽  
Amechi S. Nwankwegu ◽  
...  
Keyword(s):  
Soil Fertility ◽  
Soil Nutrients ◽  
Anthropogenic Activities ◽  
Close Association ◽  
Dry Season ◽  
Water Level Fluctuations ◽  
Nutrient Concentrations ◽  
Wet Season ◽  
Index Method ◽  
Spatio Temporal

To comprehend the distribution characteristics of the nutrients and the variations in the soil fertility, a total of 23 samples were collected from Nanjishan wetland reserve in the dry season, wet season, and water-recession season. The study area was divided into four areas (A1, A2, A3, and A4) based on the local hydrological conditions, geographical locations, and nutrient load characteristics. The findings showed that the highest concentration of nutrients appeared in A1, followed by A2 due to anthropogenic activities and the sewage discharge along Ganjiang River. Except for the total amounts of nutrients (the total nitrogen (TN), total phosphorus (TP), and total potassium (TK)), the nutrient concentrations dropped in the wet season and recovered in the water-recession season. A close association between microorganisms and the soil nutrients was observed. The Integrated Fertility Index (IFI) indicated a significant spatio-temporal variability in the soil fertility. The soil quality was higher in the dry season. The values of the IFI displayed a decreasing trend during the growing season (wet season). The single factor standard index method (SFSI) suggested that the whole area had a potential risk of eutrophication, to which the TN could be considered a main contributor.

Importance of predation and viral lysis for bacterial mortality in a tropical western Indian coral-reef ecosystem (Toliara, Madagascar)

2015 ◽  
Vol 66 (11) ◽  
pp. 1009 ◽  
Author(s):  
M. Bouvy ◽  
P. Got ◽  
Y. Bettarel ◽  
T. Bouvier ◽  
C. Carré ◽  
...  
Keyword(s):  
Bacterial Growth ◽  
Growth Rates ◽  
Free Water ◽  
Dry Season ◽  
Nutrient Concentrations ◽  
Wet Season ◽  
Viral Lysis ◽  
Bacterial Mortality ◽  
Heterotrophic Nanoflagellate ◽  
Bacterial Growth Rates

Size fractionation was performed using water from the Great Reef of Toliara (Madagascar) taken from two different habitats (ocean and lagoon) during the dry and wet seasons, to study the growth and mortality rates of bacterioplankton. Experiments were conducted with 1 and 100% of heterotrophic nanoflagellate (HNF) concentrations and virus-free water was obtained by tangential filtration (10kDa). During the dry season, in both environments, bacterial abundance and production were significantly lower than values recorded during the wet season. Bacterial growth rates without grazers were 0.88 day–1 in the lagoon and 0.58 day–1 in the ocean. However, growth rates were statistically higher without grazers and viruses (1.58 day–1 and 1.27 day–1). An estimate of virus-induced bacterial mortality revealed the important role played by viruses in the lagoon (0.70 day–1) and the ocean (0.69 day–1). During the wet season, bacterial growth rates without grazers were significantly higher in both environments than were values obtained in the dry season. However, the bacterial growth rates were paradoxally lower in the absence of viruses than with viruses in both environments. Our results suggest that changes in nutrient concentrations can play an important role in the balance between viral lysis and HNF grazing in the bacterial mortality. However, virus-mediated bacterial mortality is likely to act simultaneously with nanoflagellates pressure in their effects on bacterial communities.

scholarly journals Seasonal dynamics of carbon and nutrients from two contrasting tropical floodplain systems in the Zambezi River basin

2015 ◽  
Vol 12 (24) ◽  
pp. 7535-7547 ◽  
Author(s):  
A. L. Zuijdgeest ◽  
R. Zurbrügg ◽  
N. Blank ◽  
R. Fulcri ◽  
D. B. Senn ◽  
...  
Keyword(s):  
Organic Matter ◽  
Primary Production ◽  
River Basin ◽  
Particulate Organic Matter ◽  
Dry Season ◽  
Nutrient Concentrations ◽  
Wet Season ◽  
Carbon And Nitrogen ◽  
Zambezi River Basin ◽  
Zambezi River

Abstract. Floodplains are important biogeochemical reactors during fluvial transport of carbon and nutrient species towards the oceans. In the tropics and subtropics, pronounced rainfall seasonality results in highly dynamic floodplain biogeochemistry. The massive construction of dams, however, has significantly altered the hydrography and chemical characteristics of many (sub)tropical rivers. In this study, we compare organic-matter and nutrient biogeochemistry of two large, contrasting floodplains in the Zambezi River basin in southern Africa: the Barotse Plains and the Kafue Flats. Both systems are of comparable size but differ in anthropogenic influence: while the Barotse Plains are still in large parts pristine, the Kafue Flats are bordered by two hydropower dams. The two systems exhibit different flooding dynamics, with a larger contribution of floodplain-derived water in the Kafue Flats and a stronger peak flow in the Barotse Plains. Distinct seasonal differences have been observed in carbon and nutrient concentrations, loads, and export and retention behavior in both systems. The simultaneous retention of particulate carbon and nitrogen and the net export of dissolved organic and inorganic carbon and nitrogen suggested that degradation of particulate organic matter was the dominant process influencing the river biogeochemistry during the wet season in the Barotse Plains and during the dry season in the Kafue Flats. Reverse trends during the dry season indicated that primary production was important in the Barotse Plains, whereas the Kafue Flats seemed to have both primary production and respiration occurring during the wet season, potentially occurring spatially separated in the main channel and on the floodplain. Carbon-to-nitrogen ratios of particulate organic matter showed that soil-derived material was dominant year-round in the Barotse Plains, whereas the Kafue Flats transported particulate organic matter that had been produced in the upstream reservoir during the wet season. Stable carbon isotopes suggested that inputs from the inundated floodplain to the particulate organic-matter pool were important during the wet season, whereas permanent vegetation contributed to the material transported during the dry season. This study revealed effects of dam construction on organic-matter and nutrient dynamics on the downstream floodplain that only become visible after longer periods, and it highlights how floodplains act as large biogeochemical reactors that can behave distinctly differently from the entire catchment.

Nutrient response to soil and litter metabolic activity in a transect across a seasonal wetland

2003 ◽  
Vol 54 (3) ◽  
pp. 243 ◽  
Author(s):  
S. Qiu ◽  
A. J. McComb ◽  
R. W. Bell ◽  
J. A. Davis
Keyword(s):  
Microbial Biomass ◽  
Microbial Activity ◽  
Nutrient Dynamics ◽  
Sand Dunes ◽  
Co2 Production ◽  
Nutrient Concentrations ◽  
Co2 Efflux ◽  
Wet Season ◽  
Surface Soils ◽  
Substrate Induced Respiration

Many wetlands in the interdunal depression of coastal sand dunes of the Swan Coastal Plain are surrounded by partially vegetated catchments. Although litter can be an important source of nutrients, little is known about litter related microbial activity in these catchments, especially its role in regulating nutrient concentrations in soils during the wet season. Heterotrophic microbial activity and phosphorus (P) dynamics were monitored before and after the onset of the wet season along transects from a vegetated catchment to the lakebed in Thomsons Lake, south-western Australia. Microbial activity was measured in the field as CO2 efflux (range from 47 to 176 mg CO2 m–2 h–1) and in the laboratory as substrate-induced-respiration (SIR; range from 11 to 133 μg g–1 h–1). Substrate-induced-respiration was positively correlated with soil organic content, and was concentrated in surface soils. In contrast, in the exposed lakebed most microbial biomass was below the surface, in the 10–30 cm depth zone. There were significant changes in nutrient dynamics in response to soil microbial activity. Before rain, P extracted by anion exchange membrane (PAEM) was well correlated with site litter and plant debris (r2 = 0.90, P�<�0.001), suggesting that PAEM in soils was litter-sourced. This relationship was modified during the wet season: there was an overall increase in microbial biomass P (PMB; from average 7.5 μg g–1 to 21.6 μg g–1), and a decrease in PAEM : PMB in surface soils. Along the study transect, the assimilation index PAEM : PMB declined towards the wetland, where soils were more silty and organic, and CO2 production was significantly higher. Our data suggest that heterotrophic microbial activity has a significant role in regulating P flux from catchment litter during the wet season, which would affect the mobility of litter-sourced P from catchment to the wetland.

scholarly journals ĐÁNH GIÁ ĐẶC ĐIỂM THỦY HÓA TRONG MÔ HÌNH TÔM SINH THÁI TẠI XÃ TAM GIANG, HUYỆN NĂM CĂN, TỈNH CÀ MAU

2018 ◽  
Vol 18 (2) ◽  
pp. 205-213
Author(s):  
Nguyen Tho ◽  
Dang Nguyen Nha Khanh
Keyword(s):  
Water Depth ◽  
Pond Water ◽  
Dry Season ◽  
Total Alkalinity ◽  
Nutrient Concentrations ◽  
Total Hardness ◽  
Wet Season ◽  
Hydrochemical Parameters ◽  
Low Concentrations ◽  
Sampling Times

This paper clarifies the hydrochemical characteristics of the organic shrimp model certified by Naturland at Tam Giang commune, Nam Can district, Ca Mau province. Pond water was sampled in 8 ponds at 3 points of time of distinct precipitation fluctuations during the year (March, July and November 2015) and hydrochemical parameters related to shrimp were analysed. Results show that salinity, total alkalinity and total hardness are largely dependent on the seasonal precipitation and evapotranspiration, highest in the middle of the dry season (March) and gradually reduced until the wet season-dry season transition (November). Most of the parameters fluctuate within the sampling times but still remain suitable for shrimp. The major constraints include oxygen supersaturation during daylight hours (7.48 ± 0.45 mg/l), low concentrations of soluble nutrients (NH4-N 0.21 ± 0.05 mg/l, NO3-N 0.06 ± 0.02 mg/l, PO4-P 0.02 ± 0.01 mg/l), and high iron contents (Fe2+ 0.08 ± 0.01 mg/l, Fe3+ 0.64 ± 0.14 mg/l) as compared to limits for shrimp aquaculture. The total shrimp yields are very low (355.4 kg/ha water surface/year in which wild shrimp species have accounted for 55%), positively correlated with water depth and temperature but negatively correlated with Fe2+. To improve pond water quality and shrimp yield, it is recommended to increase water depth, nutrient concentrations and restrict the effects of runoff at the beginning of the wet season.

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