The Dynamics of Elements in Soil and Plants in Grasslands

Chukwudi Nwaogu

Doctoral thesis

Abstract:

Thesis Summary:In grasslands, elements in the soil and plants vary due to either human or environmental factors. The anthropogenic factors included different management (cutting, mulching, grazing, waste dumps) while, the environmental factors involved climate, soil characterization and bio-geochemical processes. This work concentrated mainly on the human factor. Whether in the temperate or tropical grasslands, based on the scope of this thesis, the effects of management could either enhance the soil minerals or increase the trace elements which consequently supported or harm the plants. This work could be considered as being vast because it covered five case studies with the first two studies focusing in the tropical environment (Nigeria), while the last three case studies were based in the temperate (Czech Republic) region. The primary goal of this work is to appraise the dynamics of elements in soil and plants in grasslands under different management (such as gazing, cutting, mulching, and waste disposal). In consistent with individual case study, the key goal of this thesis was realized through the following five structured hypotheses: (i) in addition to the significant effects in soil and in plant chemical properties, the municipal solid waste (MSW) dumps affect the species composition and richness; (ii) the concentrations and stocks of SOC and STN were significantly affected by slope position, soil bulk density (BD), and depth; (iii) different grassland management methods (mulching, cutting and abandonment) affect long-term successional changes in plant species composition, main plant functional groups, and species richness; (iv) the presence of faeces, deposited by heifers, on tall sward-height patches would significantly affect the amount of nutrients in the soil and consequently in the herbage of A. capillaris grassland; and (v) chicken grazing (CG) caused increase in soil N while, preferential grazing by the chickens led to changes in botanical composition.The first study aimed at assessing the responses of the elements in soil and plants in grasslands under solid waste dumps. Data was analyzed from five dump sites and five control sites. The result revealed that, the effects of the heavy metals (HM) caused by MSW were significantly higher at the dump sites where their concentrations were far above the permissible limits for agricultural soils and plants. The second case study aimed at quantifying the dynamics in soil properties under different land uses including grasslands. Six land uses [arable land (AL), forest land (FL), grassland (GL), shrubland hills (SL), urban built-up green (UL), and the freshwater swamp and mangrove wetland (WL)] were classified. Soil samples were collected and analyzed from each land use under different soil depths and slope positions. The result indicated that land use types (including grasslands), slope position, soil depth and BD, significantly affected SOC and STN contents. The third case study compared three different mulching frequencies (one, two and three times per year) with an unmanaged treatment and traditional management of two cuts per year on a previously improved upland grassland. After experiment, it was observed that (a) traditional management of two-cuts with biomass removal was the most suitable method for maintaining plant species richness and diversity, (b) mulching (especially once per year) recorded high weeds and low species richness like unmanaged treatment, hence is a preferred option for the abatement of shrubs and trees encroachment. In the fourth case study, three types of tall sward-height patches were identified: patches with faeces under intensive grazing; patches with faeces under extensive management; and patches with no faeces under extensive management. They were compared with frequently grazed swards under intensive and extensive grazing management. It was observed that no significant effect of different types of patch on soil available nutrients. On t

Abstract:

he other hand, herbage from the different types of patches differed significantly in concentrations of N, P, K, Ca and Mg. The fifth study was focused on the effects of CG on soil nutrient concentration under five years field study in sown improved grassland. Data covering soil chemical properties and plants species were collected and analyzed. Total N and plant available Mg were the only nutrients which significantly increased during the study under CG. However, the study observed a reduction of sown high productive species, except Festulolium and increasing cover of weedy Taraxacum officinale. This study showed that though, CG can increase nutrients concentrations in the soil, it can as well degrade the botanical composition of grasslands.On this note, from the five case studies it was concluded that: •the MSW significantly increased HM concentrations which consequently affected the chemical properties of soil and plant as well as the species composition and richness;•SOC and STN concentrations and stocks were significantly affected by slope position, soil bulk density and depth;•repeated mulching cannot completely be an alternative for traditional two-cut management in improved upland meadows without decreasing plant species richness and diversity, as well as changing the sward structure;•the presence of faeces increased the P and K concentrations in the herbage in tall sward-height patches in intensively grazed pasture only, whereas no effect of faeces was found in extensively grazed pasture., which is likely due to a “dilution effect”. • though, chicken grazing caused increase in soil N yet, their preference in forage grazing induced changes in botanical composition. Summarily, whether in the tropics or temperate region, management regimes have substantial influence on both the soil and floristic compositions in grasslands. Thus, understanding the dynamics of elements in the soil and plants in grasslands will help in applying the most sustainable management systems for this ecosystem.Thesis Objectives:This main goal of this study is to appraise the dynamics of elements in the soil and plants in grasslands under different management (such as gazing, cutting, mulching, and waste disposal/dump). To achieve this main goal, specific objectives based on individual case study were structured such as to:(i) investigate the responses of the soil and plant chemical properties to heavy metals (HM) induced by solid wastes in grasslands.(ii) quantify and evaluate the dynamics in soil properties under different land use in Imo watershed where there is no knowledge about the effects of land use on SOC and STN pool.(iii) examine how different meadow management methods (mulching, cutting and abandonment) affect long-term successional changes in plant species composition, the main plant functional groups, and species richness.(iv) assess the effects of grazing intensity on nutrient concentrations in herbage and soil under sward-height of patches in upland grassland.(v) analyze the effects of chicken grazing on soil nutrient and plants composition under five years field study in sown grassland.Study areas: The studies were performed in two different ecological regions: (1) temperate and (2) tropical climates. (1) temperate region (Czech Republic)The studies in the Czech Republic were performed in two different areas; in the village of Oldřichov v Hájích, and in the Netluky village. Case studies three and four are located in the Jizerské hory Mountains (Jizera Mountains) with 420 m altitude a.s.l., in the northern Czech Republic, which is 10 km north of Liberec (50°50.34′ N, 15°05.36′ E) in the village of Oldřichov in Hájích. The experimental site was established in 1998 and has a mean annual temperature of 7.2 °C and an average annual precipitation of 803 mm (Liberec Meteorological Station). The site has a medium deep brown soil (Cambisol) with 10-15 cm and is underlain by granite bedrock (Gaisler et al. 2019). The case study six (chicken grazing experiment) was conducted on 0.7 ha of experimental grassland at Netluky village (150°2'21.344''N, 14°36'51.075''E). The altitude of the study site was 284 m a.s.l., the average annual precipitation was 591 mm and the mean annual temperature was 8°C with loamy clay soil texture.(2) tropical region (Nigeria)The case studies one and two experimental sites are located in Nigeria. The case study one (soil and plants responses to MSW) cut across Nigeria (40N -140N, 30E -150E). It covered selected grasslands along the major roads linking the sub-urbans and the cities. The area has an annual temperature ranging from 23 0C to 40 0C (from the South to Northern part), and annual rainfall ranging from 500 mm -3000 mm (from the North to the South). The soils are of loamy-sand properties and primarily of Luvisols, Vertisols, Lithosols, and Ferralsols taxonomical groups (FAO, 2001). The dump sites were between 15-20 years old, and 3-8 hectares in area. The dumpsites are located in relatively plain land with about 60-90 meters above sea level (Nwaogu et al. 2017). The case study two (on the differences in SOC and STN stocks) is found in Imo watershed located in the south-east and south-south regions of Nigeria with geographical extends between 4° 50' 00"N to 6° 02' 00"N latitude and 6° 04'10"E to 7°34' 15"E longitude. It has an area of 4321.4 km2, and an elevation ranging from about 52 m - 340 m a.s.l. (Nwaogu et al. 2018) The watershed is in a humid tropical climate having a mean annual temperature of 28.5° C, and a mean annual rainfall of 2400 mm with over 70% falling between the months of May and October (FORMECU, 1998). It has a sand, loamy-sand textural characterization (Udom and Ogunwole, 2015). Methodology:The differences in the study locations prompted the use of several materials and methods to achieve the main goal of this work. Rising plate meter was used to measure the plants height; Cutlasses, hoes, and rakes were used to clear vegetative cover from the experimental sites before soil sampling. Terrax and terra-scoop in combination of a Dutch soil auger and a spatula was used to collect soil samples from the dump sites; Inductively coupled plasma–optical emission spectrometry-ICP–OES (720 Series, Agilent Technologies) was employed in the laboratory by the help of the lab-attendants for determining the plant available nutrients after extraction by Mehlich III (Mehlich, 1984). ArcGIS 10.1, NigSat and USGS Landsat images were for land use types identification/classification. Hand-held GPS (Garmin GPSMAP 64ST, USA) was used to locate/identify sampling points. Shuttle Radar Topography Mission (SRTM) for DEM at 30 m resolution was used for slope/altitude validation process. A tractor-driven mulching machine (Uni Maher UM 19, Gerhard Dücker GmbH & Co. KG) was used for the mulching treatments. Plant biomass was crushed into pieces 5–10 cm long, spread on the sward surface and pressed by the roller. Others are softwares such as the statistical packages namely; STATISTICA 13.1 (Dell Inc 2016), CANOCO 5 program (ter Braak & Šmilauer, 2012), and IBM SPSS 20.0 (IBM, 2011) which were used for the statistical analysis. These have programs such as ANOVA and RDA which were applied to determine the mean differences and significance level between treatments and sites in time. They were also used in testing the relationships such as regressions and correlations among measured variables. In terms of the experimental design, because of the diversity in the ecological settings of the work, diverse methods were applied as appropriate to each case study in order to achieve the main objective(s).References:1. Dell Inc. 2016. Dell Statistica (data analysis software system), version 13.1 software. dell.com.2. FAO (Food and Agriculture Organization of the United Nations). 2001. Pastoralism in the new millennium. FAO Animal Production and Health Paper No. 150. FAO, Rome, Italy. goo.gl/EtwC3W3. Forestry Management, Evaluation and Coordinating Unit – FORMECU.1998. An Assessment of Vegetation and Landuse Changes in Nigeria. Formecu, Abuja, Nigeria, p. 44.4. Gaisler J, Pavlů L, Nwaogu C, Pavlů K, Hejcman M, Pavlů V. 2019. Long-term effects of mulching, traditional cutting and no management on plant species composition of improved upland grassland in the Czech Republic. Grass Forage Sci. 1–13. DOI: 10.1111/gfs.12408.5. IBM Corporation. 2011. IBM SPSS Statistics for Windows, Version 20.0. Armonk, NY: IBM Corp. IBM Corp. Available online at: www.ibm-spss-statistics.soft32.com.6. Mehlich A. 1984. Mehlich III soil test extractant: a modification of Mehlich 2 extractant. Commun. Soil. Sci. Plant Anal. 15: 1409–1416.7. Nwaogu C, Ogbuagu HD, Abrakasa S, Olawoyin M.A, Pavlů V. 2017. Assessment of the impacts of municipal solid waste dumps on soils and plants, Chem Ecol. 33:7, 589-606, DOI: 10.1080/02757540.2017.13371018. Nwaogu C, Okeke JO, Fashae O, Nwankwoala H. 2018. Soil organic carbon and total nitrogen stocks as affected by different land use in an Ultisol in Imo Watershed, southern Nigeria. Chemistry and Ecology, 34:9, 854-870. http://dx.doi.org/10.1080/02757540.2018.15084619. ter Braak CJF, Šmilauer P. 2012. Canoco 5, Windows release (5.00). [Software for canonical community ordination]. Microcomputer Power, Ithaca, NY, US.10. Udom BE, Ogunwole JO. 2015. Soil organic carbon, nitrogen, and phosphorus distribution in stable aggregates of an Ultisol under contrasting land use and management history. J Plant Nutr Soil Sci. 178: 460-467. 10.1002/jpln.201400535

Keywords

grassland management, soil elements, plant nutrients, plant compositions, species richness and diversity

Language used: English

Date on which the thesis was submitted / produced: 19. 3. 2019

Thesis defence

• Supervisor: prof. Dr. Ing. Vilém Pavlů
• Reader: Josef Hakl, Ph.D., doc. Ing., Stanislav Hejduk, externi, Zygmunt Kącki, externi

Czech University of Life Sciences Prague

Faculty of Environmental Sciences

Doctoral programme / field:
Ecology / Ecology