Changes in hydrologic components from a mid-sized plots induced by rill erosion due to cyanobacterization

Atefeh Jfrpoor ,Seyed Hmidrez Sdeghi ,Behrouz Zrei Drki ,Mehdi Homee

a Department of Watershed Management Engineering,Faculty of Natural Resources,Tarbiat Modares University,Noor,Iran

b Department of Watershed Management Engineering,Faculty of Natural Resources,Tarbiat Modares University,Noor,46417-76489,Iran

c Department of Marine Biology,Faculty of Marine Science,Tarbiat Modares University,Noor,Iran

d Agrohydrology Research Group,College of Agriculture,Tarbiat Modares University,Tehran 14115-336,Iran

Keywords:Soil bio-crust Soil infiltration Water balance Water management

A B S T R A C T Runoff components are the most important factors in explaining the hydrological behaviour of a system.So that the proper understanding of the runoff processes may effectively help managers and decisionmakers adopt appropriate measures.In this regard,there are variety of approaches to handle runoff generation,but the application of environmentally friendly,biologic-based and cost-effective approaches such as soil microorganisms has been seldom reported.The study has therefore tried to investigate the role of inoculation of cyanobacteria on runoff components under rain simulation conditions at the midsized(i.e.,6×1m)plots installed at≈30 % slope steepness.The treated plots were subjected to a simulated rainfall with an intensity of 50 mm h-1 and an initial duration of 30 min with three replications.A simulated runoff of 2.18±0.32 Lmin-1 was also performed simultaneously on the onset of starting surface runoff.The results showed significant differences(P＜0.021)in hydrological behaviours in control and treated plots.So that no surface runoff was produced in treated plots up to the end of the initial duration of 30 min of simulated rainfall.The results revealed that cyanobacterization by secretion of exopolysaccharides not only postponed runoff generation but also effectively inhibited runoff components even if the rainfall incident extended for longer periods.The positive effect of cyanobacterization on increasing infiltration and potential storage of water beneath the soil was also verified in the present study,which suggests the profitable application of cyanobacteria for regulating hydrologic components.

1.Introduction

Hydrological behaviour is a key point to effective water management,policy-making,and sustainable development.Runoff and infiltration are important components of the hydrological cycle that the knowledge of how runoff generation and infiltration rate is necessary for planning and management of water balance,nutrient cycling,and soil erosion(Du et al.,2016;Shawul et al.,2019;Vivoni et al.,2007).Indeed,the modification of the hydrological process by changing infiltration properties and thereby generating runoff ultimately determines the quality of many of the aforementioned functions such as soil hydrological services,soil loss,and land degradation.Although there are different approaches to study hydrological behaviour,the use of microorganisms-based biological methods has rarely been used(Chamizo et al.,2012;Felde et al.,2014;Miyata et al.,2019).

To date,the use of biological soil crusts as a biologically,economically,and environmentally friendly method(Kheirfam et al.,2017;Zhou et al.,2020)in controlling surface runoff,infiltration rate,and hydrological processes have been used and approved by former scholars(i.e.,Belnap et al.,2013;Zhao et al.,2013;Chamizo et al.,2015;Kidron,2015;Chamizo et al.,2017;Kheirfam,Sadeghi,Homaee,& Zarei-Darki,2017,b;Sadeghi et al.,2017;Chamizo et al.,2020;Gao,Bowker,et al.,2020,b;Kheirfam,Sadeghi,& Darki,2020;Sadeghi,Kheirfam,& Zarei-Darki,2020,b;Sadeghi et al.,2021).Generally,the positive effects of application of biological soil crusts(BSCs)as a biological method of soil and water conservation on infiltration rate(Chamizo et al.,2012;Sadeghi et al.,2017;Gao,Bowker,et al.,2020,b),soil organic matter content(Griffiths et al.,1998;Chamizo et al.,2012;Cant′on et al.,2014;Zhang et al.,2018;Zhou et al.,2020),soil stability and structure(Cosentino et al.,2006;Lehmann et al.,2017;Lynch&Bragg,1985;Sepehr et al.,2019),shear strength(Canakci et al.,2015;DeJong et al.,2006;Martin et al.,1996)have been ascertained.

By and large,cyanobacteria are one of the components of BSCs dominated in many ecosystems(Pen-Mouratov et al.,2011;Roncero-Ramos et al.,2019;Deng et al.,2020;Conton et al.,2020).Indeed,cyanobacteria are the first colonizers of terrestrial ecosystems and capable to survive under extreme temperatures(Chamizo et al.,2018;Rodríguez-Caballero et al.,2019),high saline environments(Rodríguez-Caballero et al.,2019),and high levels of UV radiation(Castenholz et al.,2012;Rodríguez-Caballero et al.,2019).In addition,cyanobacteria through increasing the secretion of polysaccharide adhesives increase the roughness coefficient(Chamizo et al.,2016;Bullard et al.,2018;Sadeghi et al.,2020),soil stability,and structure(Sadeghi et al.,2017;Chamizo et al.,2018;Felde et al.,2018;Concostrina-Zubiri et al.,2019;Kheirfam,Sadeghi,& Darki,2020),shear strength of the soil particle threshold(Martin et al.,1996;DeJong et al.,2006;Canakci et al.,2015),soil organic matter(Jung et al.,2018;García-Carmona et al.,2020),and carbon sequestration and nitrogen fixation(Chamizo et al.,2018;Jung et al.,2018;Roncero-Ramos et al.,2019;Kheirfam,2020;Rom′an et al.,2021)ultimately leading to reduce runoff and soil loss(Kheirfam,Sadeghi,Homaee,& Zarei-Darki,2017,b;Sadeghi et al.,2017;Xiao et al.,2019;Chamizo et al.,2020;Kheirfam,Sadeghi,&Darki,2020;Sadeghi,Kheirfam,& Zarei-Darki,2020,b;Cant′on et al.,2020;Sadeghi et al.,2021).Despite many studies conducted in the field of cyanobacteria inoculation for soil and water conservation purposes,no understanding of complex and heterogeneous hydrological behaviours of marl soil due to cyanobacterization and subject to rilling phenomenon has been achieved yet.Therefore,the present study aimed to investigate changes in hydrologic components from inoculation of soil cyanobacteria in marl soil.The results of the present study can be used as an effective and biological solution to conserve soil and water resources in the watersheds with inherent susceptible and fragile formations.

2.Material and methods

2.1.Site description and sampling

The study area has high susceptibility to erosion resulting in high sediment yield.The easy accessibility,sensitivity of soil formations,high erodibility and sediment yield as well as existing benchmark studies were the main reason behind selecting the study region.The studied soil was collected from a sub-watershed of the Chalus Watershed(Marzanabad-Kandelous Region)with an area of 86.34 km2located in the west of Mazandaran Province,northern Iran.The mean annual precipitation and temperature based on the Kojour and Nowshahr stations from 1978 to 2010 were 432 mm and 12°C,respectively,the soil texture was silty clay loam with a bulk density of 1.16 g cm-3(Kheirfam et al.,2017 ab;Sadeghi et al.,2017;Sadeghi et al.,2020b).

2.2.Isolation,purification,and proliferation of soil cyanobacteria

In the present study,the Bold Basal Medium(BBM)medium was used in order to extract the various genera of cyanobacteria in soil microorganisms'banks(Lavens et al.,1996).Thus,for isolating and identifying the cyanobacteria,5 g of soil samples was crashed to the size of＜2 mm(Chamizo et al.,2012)and was transferred into an 8-cm diameter Petri-dish soaked by 5 ml BBM with three replications(Sadeghi et al.,2021).In addition,7 lamellae were placed on the surface of the Petri-dishes.Then,for a period of one month,a sample was taken every 4 days on average and the growth of cyanobacteria was monitored,the number was counted and the species were identified(Zarei-Darki,2011)by using a high-resolution optical microscope.Finally,three species of cyanobacteriaNostocsp.,Oscillatoriasp.,andLyngbya,sp.were selected and cultured to reach a suspension with a frequency of cyanobacteria at a tune of 1012CFU.The solution was then prepared for inoculation on the soil surface(Vieira&Nahas,2005;Kheirfam,Sadeghi,Homaee,&Zarei-Darki,2017,b;Sadeghi,Kheirfam,& Zarei-Darki,2020,b;Sadeghi et al.,2021).

2.3.Preparation of experimental treatments

The present study was conducted in mid-sized plots(i.e.,6×1 m)at the Rainfall and Erosion Simulation Laboratory of Tarbiat Modares University,Iran.An experimental setup with rainfall height of 6 m,the intensity of 50 mm h-1and initial duration of 30 min,and a 3-replication plots at a slope of some 30%and similar to the main conditions governing the soil origin was employed for the current study(Khaledi Darvishan et al.,2014;Kiani-Harchegani et al.,2018,2019).The experiment was designed in two treatments of control and cyanobacteria inoculated with three replications.In order to investigate the effect of soil cyanobacteria on hydrologic components,the prepared cyanobacteria solution was inoculated on the soil surface via spraying and left for 40 days for the better establishment and effectiveness of cyanobactrization(Kheirfam,Sadeghi,Homaee,& Zarei-Darki,2017,b;Sadeghi et al.,2017;Sadeghi et al.,2020;Sadeghi et al.,2021).The treated and control plots were then subjected to rainfall simulation.Furthermore,on the onset of arriving surface runoff to the outlet of the plot,runoff simulations at the rate of 2.18±0.32 was simultaneously performed from the upper part of the plot while the rainfall was continuing to facilitate mimicking longer slope length and rilling conditions(Niu et al.,2020;Strohmeier et al.,2014).

2.4.Data collection and analyses

To compare the hydrologic components in the study control(i.e.,without cyanobacterial inoculation)and treated plots(i.e.,with cyanobacterial inoculation),the runoff samples were taken at the onset of runoff commencement reached the plot outlet.For each rainfall event,the runoff was measured volumetrically at 2-min intervals(Zhang et al.,2018).Different components viz.start time of surface runoff,time to peak,volume and runoff coefficient,water storage in the soil column,and seepage from the bottom of the experimental plots were then precisely measured.In this regard,the runoff coefficient was calculated by dividing the runoff volume by the rainfall volume entered into the experimental plots(Niu et al.,2020;Shen et al.,2016).Eventually,the database prepared in Microsoft Excel 2016 and in IBM SPSS 21 software package was used to carry out the comparative statistical analyses applying paired samplest-Test.The prerequisite normality assumption for all data was also evaluated using the Shapiro-Wilk test.The step-bystep view of the simulation experimental procedure is shown in Fig.1.

3.Results and discussion

Fig.1.A microscopic view of soil particles aggregation by cyanobacterial secretion(a),stocks of cyanobacteria for inoculation(b),soil experimental plots(c),measurement of output runoff at the end of the experimental plot(d),measurement of seepage water volume under plot(e)and a treated plot after completion of experiment and a rill under developmental stage(f).

The study was conducted to show the different hydrologic behaviours of mid-sized plots treated by cyanobacteria in comparison with the control plots whose corresponding results have been depicted in Figs.2 and 3.The results of the statistical comparisons have also been epitomized in Table 1.The statistical analysis showed that the inoculation of cyanobacteria significantly(P＜0.021)delayed the start time of surface runoff and time to peak,reduced the runoff volume and coefficient,and increased seepage and infiltrated water content.According to Figs.2 and 3,there was no surface runoff in the treated plot with cyanobacteria for the design rainfall of 30 min.Accordingly,the rainfall simulation was prolonged for more than 30 min and therefore associated runoff was commenced at 32.07±3.63 min.Likewise,the peak runoff occurred at 14.21±4.69 min in control plots,while,it was 52.74±3.61 min in cyanobacteria treated plots.In addition,the results showed the volume and coefficient of runoff in control and cyanobacteria treated plots were respectively 109.10 L and 42.61%,and 63.09±14.11 L and 15.17±4.15 %.Similarly,the respective amount of seepage and infiltrated water in control plots were 0.00 L and 130.90±21.91 L.Whilst,the respective amount of seepage and infiltrated water in the cyanobacteria treated plots were 228.15±12.38 L and 98.75±5.65 L.

Table 1Results of the paired-samples t-Test for comparing start time of surface runoff,time to peak,runoff volume,runoff coefficient,seepage,and infiltrated water in the control and cyanobacteria-treated plots.

Our results showed that the cyanobacteria by producing secreted polysaccharide,exopolysaccharide and bio-films caused improving soil structure and soil aggregate stability and increased the amount of infiltration,and change hydrological behaviour as reported in previous studies(i.e.,Sadeghi et al.,2017;Chamizo et al.,2018;Felde et al.,2018;Concostrina-Zubiri et al.,2019;Kheirfam,Sadeghi,& Darki,2020).The results showed that the secretion of exopolysaccharide materials,forming micro-networks,raising porosity,and expanding water retention by cyanobacteria positively enhanced hydrological characteristics of the soil system under consideration.In this regard,the variation of the runoff generation model from type 1 of Horton's model under the control condition to type 2 of Horton's model in plots treated by cyanobacteria would be the main reason behind changing hydrological behaviours as reported by Kozlov and Ghebrehiwot(2019)and Varade et al.(2019).Previous research has shown that cyanobacteria reduce runoff in fine-textured soils by secreting exopolysaccharides that increase soil porosity and water absorption,while they increase runoff in coarse-textured soils by decreasing soil pore spaces(Sadeghi et al.,2017).In the treated plots,cyanobacteria enhanced the infiltration rate so that no runoff is generated until the maximum storage content of the soil mantle was fulfilled.Later,the excess runoff and deep seepage were then started.As a result of the continued rainfall simulation phase,the surface runoff began in 32.0±73.63 min,almost immediately after the experiment's initial design duration was completed.Cyanobacteria inoculation nearly doubled the time it took for runoff to start.The research treatment reduced runoff volume and coefficient by 42.17 % and 78.44 %,respectively.These findings were consistent with those reported by formers scholars(i.e.,Kheirfam,Sadeghi,Homaee,& Zarei-Darki,2017,b;Sadeghi et al.,2017;Kheirfam,Sadeghi,& Darki,2020;Sadeghi,Kheirfam,& Zarei-Darki,2020,b;Cant′on et al.,2020;Sadeghi et al.,2021).The results,on the other hand,showed that cyanobacterial inoculation improved soil infiltration and seepage water.According to the findings,approximately 25%of the rainfall seeped and 59 % of the excess rainfall was infiltrated into the cyanobacterial treated soil,and just 15% was surface runoff,which agreed with Kheirfam,Sadeghi,Homaee,and Zarei-Darki(2017),Sadeghi et al.(2017),Chamizo et al.(2020)and Sadeghi et al.(2020a,b).

Fig.2.Comparison of means of the time to surface runoff(a),time to peak(b),runoff volume(c),runoff coefficient as runoff-rainfall ratio(d),seepage water(e),and infiltration water(f)in the study treatments.

Fig.3.Temporal variation of runoff volume in the study treatments.

4.Conclusions

Balancing water components in terrestrial ecosystems is vital for proper planning and sustainable management of soil and water resources.In this regard,different hydrologic processes,with a focus on surface runoff,need a deeper understanding.The current study confirmed that inoculation of soil endemic cyanobacteria is an efficient,cost-effective,and environmentally safe strategy for regulating various components of runoff and hydrological processes,building on previous studies.As a result,using soil microorganisms to improve the hydrological elements,security,and balance of soil and water resources would be a viable option.Given the role of hydrologic components in sediment transport and soil erosion,the findings of this study may be a useful step toward soil and water resources conservation,particularly in areas where other soil and water conservation initiatives are restricted.While further research and time are required to draw detailed conclusions,a focus on environmental factors necessitates a deeper understanding and long-term investigations.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

The Agrohydrology Research Group of Tarbiat Modares University contributed to this analysis in part(Grant No.IG-39713).Later,the Iran National Science Foundation(Project No.98014330)provided partial funding for this study,which is highly appreciated.