Effect Of Land Use Conversion Research Articles

Effect of land use conversion on the soil aggregate-associated microbial necromass carbon in estuarine wetland of the Pearl River in China

Microbial necromass carbon (MNC), as an important component of the soil organic carbon (SOC) pool in natural environments, has increasingly gained significant attention in recent years. However, the redistribution pattern of microbial necromass in aggregate fractions of estuarine soils induced by human activity still remain unclear. In this study, we assessed the effect of land use conversion on the redistribution and accumulation patterns of aggregate-associated MNC in estuarine wetland soils on the Pearl River estuary of China. Typical soil samples in 0–30 cm profiles under different land uses [Natural Wetland (NW), Farmland (FL), and Construction Land (CL)] were analyzed. The results showed that the NW conversion to FL and then CL contributed to the continuous losses of SOC, however, the aggregate-associated MNC content was higher in FL and lower in CL compared to NW. The MNC contribution to total SOC in aggregate fractions gradually increased from NW (16.41 % − 23.62 %) to CL (23.87 % − 30.98 %) and then FL (34.62 % − 38.83 %) in profiles. Fungal necromass C was the primary contributor to the total MNC in each aggregate fraction. In NW, the MNC was mainly present in large aggregate size, however, the MNC was gradually enriched into smaller size aggregates, especially for the bacterial necromass C, after the conversion from NW to FL or CL. Microbial biomass carbon had a direct and positive effect on the MNC in soil aggregates under different land uses, except for in silt + clay fraction from NW. Moreover, pH and soil moisture content were two key variables affecting the MNC content and accumulation by mediating the microbial biomass of different land uses, while the dominate factors controlling the MNC accumulation varied with size fractions in aggregates. Our results emphasize the influence of land use conversion on the soil aggregate-associated MNC accumulation in estuarine wetland.

The effect of land-use conversion from agriculture to perennial biomass crops and nitrogen fertilizer on soil organic carbon stock in southern Ontario, Canada

Switchgrass [Panicum virgatum, (SG)] and miscanthus [Miscanthus spp., (Mis)] are perennial biomass crops (PBCs) commonly grown in Ontario, Canada. By the integration of PBCs on marginal/degraded agricultural (Ag) fields, a positive gain in soil organic carbon (SOC) sequestration has been reported in the scientific literature. Therefore, using PBCs to enhance SOC sequestration can potentially contribute to Canada's goal to reach net-zero greenhouse gas emissions by 2050. However, long-term field research (>10 years) to clearly demonstrate this trend in Canada is limited. In the above context, this study compared the current SOC stock (Mg C ha−1) in SG and Mis to that of baseline Ag SOC obtained from three different locations, namely Elora (2008–2019), Guelph (2009–2020) and Burlington (2016–2020), Ontario, Canada. SOC stock at the time of land-use conversion from Ag to SG and Mis was considered as baseline. Woodlots (WLs), undisturbed natural forests, were used as reference SOC (potential maximum SOC stock) to predict the potential SOC sequestration in the future by PBCs at the respective locations. Results showed that SOC stocks in all SG fields, Mis fields and WLs were higher compared to respective baseline Ag fields. SOC stocks (Mg C ha−1) in PBCs were significantly higher in Elora (SG: 96.3 ± 3.44, Mis: 100.0 ± 1.48) and Guelph (SG: 88.5 ± 5.72, Mis: 87.9 ± 6.43) over 11 years, whereas SOC stock in Burlington (SG: 87.5 ± 5.04, Mis: 94.7 ± 4.86), showed no significant difference over 4 years compared to their respective baseline Ag fields (77.6 ± 3.09, 59.3 ± 1.17 and 84.1 ± 3.39). All WLs had significantly higher SOC stock compared to their respective baseline Ag fields, showing the potential for future SOC stock gain by PBCs. SOC stock values in SG, with different nitrogen (N) fertilizer application rates (0, 40, 80 and 160 kg N ha−1), were not significantly different. Conversely, SOC stock at all N rates were significantly higher in SG than baseline Ag SOC stock values. For Mis, only N fertilizer rates 40, 80, 160 kg N ha−1 significantly increased SOC stock. However, within the four N fertilizer rates, SOC significantly increased only at 80 kg N ha−1. Increases in SOC stock suggest that converting marginal lands to PBCs over the long-term (>10 years) could create additional terrestrial C sinks. In Canada, there are close to 10 million ha of degraded Ag lands that can potentially be repurposed for PBCs, therefore the conversion of these unproductive Ag lands to PBCs could significantly contribute to Canada's climate mitigation strategies.

Effect of land use conversion on heavy metals and magnetic minerals on water reservoir riparian soils

Spatial hydrological alterations seem to influence the variability of soil-bound magnetic particles and heavy metals in water reservoir riparian wetlands (RW). To date, applying geochemical analysis with magnetic techniques to assess heavy metal pollution is rarely practiced in RW soils. We studied the magnetic properties and heavy metals, including Cu, Cr, and Zn, of topsoils in RW and the adjacent upland regions (UR, as control) in the Three Gorges Reservoir, China. Potentially elevated low-frequency mass magnetic susceptibility (χLF), anhysteretic remanent magnetization susceptibility (χARM), isothermal remanent magnetism, and all selected heavy metals were found in RW. The grain size of the magnetic minerals was coarser in RW than that in UR. The pollution load index (PLI) of the studied samples was 1.18 ± 0.12 and 1.04 ± 0.21 in RW and UR, respectively. PLI and concentrations of Cu, Cr, and Zn were positively correlated with χLF, χARM, and isothermal remanent magnetism in RW, whereas no clear linkages were observed between PLI and isothermal remanent magnetism in UR. This finding reveals that hydrological alterations increased the magnetic enhancement and heavy metal enrichment in RW. We find that magnetic proxies of soils could trace the concentration of selected anthropogenic heavy metals and their pollution level in RW.

A Review on Soil Carbon Sequestration in Different Land Use and Land Cover

Decomposing organic matter and soil are crucial components of the global carbon cycle in terrestrial environments where carbon is stored in living biomass. Carbon is transferred between these systems and the atmosphere through photosynthesis, respiration, decomposition, and combustion. Human activities alter the carbon stocks in these pools by altering the land use patterns of the region. Hence, soils are both carbon sources and sink with great potential to reduce climate change. In the significant terrestrial carbon sink, soil holds twice as much carbon as the atmosphere and vegetation combined. After being the primary terrestrial carbon storage of the planet, even so, there is strong evidence that over the past several decades, significant amounts of carbon have been lost from soils of natural and agricultural ecosystems due to erosion, leaching, and enhanced soil respiration. Therefore, even a minor change will significantly affect soil carbon sequestration, the global carbon cycle, and climate change. The dynamics of soil organic carbon are strongly influenced by land use management; however, the impact varies depending on the climate, soils, and management techniques. Thus, a thorough understanding of soil organic carbon pool changes and their fractions is required to minimize carbon emissions and implement effective land use planning for sustainable soil management. This paper reviews the literature on carbon sequestration in soil and the effects of land use conversions on soil carbon stocks.

Effects of Land-use Conversion on Soil Nitrification and NO & N2O Emissions in Tropical China Under Different Moisture Conditions

Rain and heat conditions are abundant in tropical areas, and rubber and tea are widely planted in this region; the nitrification process produces nitrate content, which is not conducive to the maintenance of nitrogen nutrients, and has negative environmental effects (nitrogen oxide emissions). The characteristics of soil nitrification rate and nitrogen oxide emission under different land use patterns remain unclear. An incubation experiment was conducted under the 5 a (T5) and 15 a (T15) tea plantation soils and the nearby typical rubber plantation (XJ) soils in Baisha county of Hainan province under two moisture contents (50% WFPS-L and 80% WFPS-H) for 71 d at 25℃. The results showed that:① after the rubber plantation was converted to a tea plantation, the net nitrification and soil NO and N2O emissions were significantly reduced under high moisture content. The overall trend was in the order of XJH>T15H>T5H, and the values of soil net nitrification and NO and N2O emissions were as high as 4.2 mg·(kg·d)-1, 1.4 mg·kg-1, and 14.3 mg·kg-1 in the XJH treatment, respectively. Under the low moisture content, soil NO emissions in tea field soil were significantly reduced relative to those in rubber plantation soil, N2O emissions had no significant difference among different treatments, and net nitrification had no significant difference between the XJ and T15 treatments. There was a significant positive correlation between NO emissions and net nitrification rate (P<0.01). ② The net nitrification of XJH was higher than that of XJL, but the net nitrification values under different moisture contents in tea field soil was in contrast to that in rubber plantation soil. The NO emissions of XJ and T15 under different moisture contents were consistent with the trend of net nitrification, and the high nitrification promoted NO emissions, whereas NO emissions of T5 were not significantly affected by moisture content. The high moisture content treatment significantly promoted N2O emissions relative to those under the low moisture content treatment. The results showed that SOM, TN, pH, and moisture content were the key factors affecting soil net nitrification rate, NO, and N2O emissions. The conversion of the rubber plantation to a tea plantation significantly reduced the net nitrification rate and negative impact on the environment under high moisture content.

THE IMPACT OF MEGA INFRASTRUCTURE ON THE HYDROLOGY OF RUIRU AND KAMITI RIVER CATCHMENTS

Ruiru, a town within the metropolitan area of Nairobi Kenya, has experienced rapid urbanization which has generated a lot of challenges and problems – economically, socially, and environmentally The Purpose of this research was to study the impact of mega infrastructure on the hydrology of Ruiru and Kamiti rivers. The catchment area was defined by River gauging station (RGS) 3BB12 on River Kamiti and delineated using the RGS as the catchment outlet and was based on SRTM void filled Digital Elevation Model (DEM). Data sets utilized in the study were landsat images, google earth images, river flow data obtained from from water resources authorities (WRA), river abstraction records, water production data and rainfall data. Various GIS methods employed to analyze the data included normalized difference built up index (NDBI), hydrological characterization using the threshold method, change detection, and GIS software (ILWIS and Grass GIS). The supervised classification built up index for the study area increased from 2.8% to 51.8% for the period under study. The mean flows over this period decreased from 2.2m3/s to 0.53m3/s. This indicated that there was a definite effect of change in land use to the river flow regime. However, to conclude that mega projects had a separate effect to ‘normal’ urban development would not have been correct. This is because the flow duration curves for the different periods (1958-1987, 1988-2000, 2005-2010, 2011-2016) showed a similar pattern with no abnormal changes seen in the previous 10-15 years. It is therefore recommended that developmental control be enforced. This will assist in mitigating against the negative effects of land use conversion. The present development control authorities need to be strengthened to enforce development control. The zoning guidelines and planning regulations form the basis for developmental control and should be enforced.&#x0D;

Conversion from rice fields to vegetable fields alters product stoichiometry of denitrification and increases N2O emission

Information about effects of conversion from rice fields to vegetable fields on denitrification process is still limited. In this study, denitrification rate and product ratio (i.e., N2O/(N2O + N2) ratio) were investigated by soil-core incubation based N2/Ar technique in one rice paddy field (RP) and two vegetable fields (VF4 and VF7, 4 and 7 years vegetable cultivating after conversion from rice fields, respectively). Genes related to denitrification and bacterial community composition were quantified to investigate the microbial mechanisms behind the effects of land-use conversion. The results showed that conversion of rice fields to vegetable fields did not significantly change denitrification rate although the abundance of denitrification related genes was significantly reduced by 79.22%–99.84% in the vegetable soils. Whereas, compared with the RP soil, N2O emission rate was significantly (P < 0.05) increased by 53.5 and 1.6 times in the VF4 and VF7 soils, respectively. Correspondingly, the N2O/(N2O + N2) ratio increased from 0.18% (RP soil) to 5.65% and 0.65% in the VF4 and VF7 soils, respectively. These changes were mainly attributed to the lower pH, higher nitrate content, and the altered bacterial community composition in the vegetable soils. Overall, our results showed that conversion of rice fields to vegetable fields increased the N2O emission rate and altered the product ratio of denitrification. This may increase the contribution of land-use conversion to global warming and stratospheric ozone depletion.

Effects of Land Use Conversion on the Soil Microbial Community Composition and Functionality in the Urban Wetlands of North-Eastern China

Urban wetlands are undergoing intensive conversion from natural wetlands to farmlands, woodlands, and even alkaline land. This study aimed to determine the effects of land conversion on soil microbial communities of urban wetlands in the hinterland of Songnen Plain, Northeastern China. Soil samples were collected from various sites of Longfeng wetland, including swamp wetland (SW), meadow wetland (MW), woodland (WL), farmland (FL), and alkaline land (AL). High-throughput sequencing followed by bioinformatic analysis was conducted to evaluate the structure, composition, and function of soil bacterial and fungal communities. The most dominant bacterial and fungal phylum among the land-use types were Proteobacteria and Ascomycota, respectively. In addition, the bacterial diversity and functions varied significantly across different land-use types. However, no remarkable differences in fungal communities were observed under various land-use types. Edaphic parameters, including exchange sodium percent (ESP) and total nitrogen (TN), remarkably influenced the abundance and diversity of soil microbial communities. These results show that land-use type shapes various aspects of soil microbial communities, including soil physicochemical properties, microbial taxa structure, potential functional genes, and correlation with environmental factors. This study provides reliable data to guide land use management and supervision by decision-makers in this region.

Fallow Land Enhances Carbon Sequestration in Glomalin and Soil Aggregates Through Regulating Diversity and Network Complexity of Arbuscular Mycorrhizal Fungi Under Climate Change in Relatively High-Latitude Regions.

Soil aggregation and aggregate-associated carbon (C) play an essential function in soil health and C sequestration. Arbuscular mycorrhizal fungi (AMF) are considered to be primary soil aggregators due to the combined effect of extraradical hyphae and glomalin-related soil proteins (GRSPs). However, the effects of diversity and network complexity of AMF community on stability of soil aggregates and their associated C under long-term climate change (CC) and land-use conversion (LUC) in relatively high-latitude regions are largely unexplored. Therefore, an 8-year soil plot (with a 30-year cropping history) transplantation experiment was conducted to simulate CC and LUC from cropland to fallow land. The results showed that Glomus, Paraglomus, and Archaeospora were the most abundant genera. The diversity of AMF community in fallow land was higher than cropland and increased with increasing of mean annual temperature (MAT) and mean annual precipitation (MAP). Fallow land enhanced the network complexity of AMF community. The abundance families (Glomeraceae and Paraglomeraceae) exhibited higher values of topological features and were more often located in central ecological positions. Long-term fallow land had a significantly higher hyphal length density, GRSP, mean weight diameter (MWD), geometric mean diameter (GMD), and C concentration of GRSP (C-GRSP) than the cropland. The soil aggregate associated soil organic carbon (SOC) was 16.8, 18.6, and 13.8% higher under fallow land compared to that under cropland at HLJ, JL, and LN study sites, respectively. The structural equation model and random forest regression revealed that AMF diversity, network complexity, and their secreted GRSP mediate the effects of CC and LUC on C-GRSP and aggregate-associated SOC. This study elucidates the climate sensitivity of C within GRSP and soil aggregates which response symmetry to LUC and highlights the potential importance of AMF in C sequestration and climate change mitigation.

Effects of land use conversion on selected physico-chemical properties of peat in the Leyte Sab-a Basin Peatland, Philippines

Effects of land use conversion on selected physico-chemical properties of peat in the Leyte Sab-a Basin Peatland, Philippines

Forecasting the Cumulative Effects of Multiple Stressors on Breeding Habitat for a Steeply Declining Aerial Insectivorous Songbird, the Olive-sided Flycatcher (Contopus cooperi)

To halt ongoing loss in biodiversity, there is a need for landscape-level management recommendations that address cumulative impacts of anthropogenic and natural disturbances on wildlife habitat. We examined the cumulative effects of logging, roads, land-use change, fire, and bark beetle outbreaks on future habitat for olive-sided flycatcher (Contopus cooperi), a steeply declining aerial insectivorous songbird, in Canada’s western boreal forest. To predict the occurrence of olive-sided flycatcher we developed a suite of habitat suitability models using point count surveys (1997–2011) spatially- and temporally-matched with forest inventory data. Flycatcher occurrence was positively associated with small (∼10 ha) 10- to 20-year-old clearcuts, and with 10–100% tree mortality due to mountain pine beetle (Dendroctonus ponderosae) outbreaks, but we found no association with roads or distance to water. We used the parameter estimates from the best-fit habitat suitability models to inform spatially explicit state-and-transition simulation models to project change in habitat availability from 2020 to 2050 under six alternative scenarios (three management × two fire alternatives). The simulation models projected that the cumulative effects of land use conversion, forest harvesting, and fire will reduce the area of olive-sided flycatcher habitat by 16–18% under Business As Usual management scenarios and by 11–13% under scenarios that include protection of 30% of the land base. Scenarios limiting the size of all clearcuts to ≤10 ha resulted in a median habitat loss of 4–6%, but projections were highly variable. Under all three management alternatives, a 50% increase in fire frequency (expected due to climate change) exacerbated habitat loss. The projected losses of habitat in western boreal forest, even with an increase in protected areas, imply that reversing the ongoing population declines of olive-sided flycatcher and other migratory birds will require attention to forest management beyond protected areas. Further work should examine the effects of multiple stressors on the demographic mechanisms driving change in aerial insectivore populations, including stressors on the wintering grounds in South America, and should aim to adapt the design of protected areas and forest management policies to projected climate-driven increases in the size and frequency of wildfires.

The effect of land use conversion on landslides risk in protected function areas: case study in Samigaluh district, Kulon progo regency, Yogyakarta, Indonesia

Protected areas whose function have been converted became problems in many regions. The cause of landslides is still being studied whether it is natural conditions or human contributions, namely land use changes. Investigation of land use change events play an important role in environmental sustainability. The purpose of this study was to determine the effect of land use change in protected areas against landslides. The method used is a surveillance method. The data is processed using non-parametric statistical tests by comparing the level of landslide hazards in areas where there is no land function conversion with those that have land function conversion. The data description shown that 58% of the protected function area in Samigaluh District had the potential for high landslides. The results obtained shown that there was a significant difference in the level of landslide hazard between areas with and without land function conversion. So that the land conversion that occurred in the protected forest in Samigaluh District had a significant effect on landslides as evidenced by the asymp sig (0.031) <p-value (0.05). This result becomes consideration for the local government in monitoring protected forests for environmental sustainability.

Land use conversion and lithology impacts soil aggregate stability in subtropical China

Soil aggregate stability is one of the most important indicators of soil structure and soil degradation vulnerability, and it is the dominant factor controlling hillslope soil erosion in the subtropical Ultisols region of China. However, few studies have investigated the synergistic effects of land use conversion and lithology on soil aggregate stability, especially in subtropical Ultisols region of China where soil erosion is a serious concern. Soil samples from 0 to 100 cm depth at increments of 20 cm were collected from four typical land use types (natural forest, artificial forest, orchard, and cropland) and two lithologies (granite and slate) to determine soil aggregate stability using the Le Bissonnais' and Yoder' methods on Ultisols from subtropical China. Results indicated that both land use type and lithology significantly influenced the soil aggregate stability. Specifically, in different soil depths of 0–100 cm, land use changes from natural forest to orchard and cropland significantly decreased the aggregate stability, thus increasing soil erodibility. Following the conversion of natural forest to artificial forest generally enhanced soil stability and resistance to flowing water erosion. For lithology, the slate soil was more resistant to erosion than granite soil. The generalized linear model can explain >60% of the total variation in soil aggregate stability, and the effect of land use on aggregate stability was greater than lithology. Compared with the Yoder' wet-sieving method, the Le Bissonnais method was better at characterizing soil aggregate stability among land uses and lithology, and therefore should be considered as a preferred method in future studies in the subtropical Ultisols region of China.

Assessing hydrologic and water quality effects of land use conversion to Brassica carinata as a winter biofuel crop in the southeastern coastal plain of Georgia, USA using the SWAT model

AbstractCarinata (Brassica carinata) is an industrial oilseed feedstock for renewable fuels grown as a winter crop in the southeast US, which may provide a new rotation alternative and benefits for water quality. However, the effects of carinata on water quantity and quality at the watershed and local scales are unknown. In this study, we use the Soil and Water Assessment Tool (SWAT) to assess the potential influence of carinata on water balance components, nutrients and sediment loads under plausible future scenarios of land use change in the upper Suwannee River Basin in the Atlantic Coastal Plain Physiographic Region near Tifton in South‐Central Georgia. Three future scenarios are considered, including planting stand‐alone carinata in winter fallow land every third year, planting stand‐alone winter wheat in winter fallow land every third year, and carinata and winter wheat in rotation, one year of winter carinata followed by two years of winter wheat during simulation periods. The results show that under all three future scenarios, surface runoff, sediment, phosphorus, and nitrogen loadings decrease at both watershed and local scales, with higher average monthly reductions in the stand‐alone carinata scenario versus the stand‐alone winter wheat scenario. When carinata and winter wheat were planted over 36% of the total watershed area, reduction in total sediment, mineral phosphorus, and nitrate loads was ranging from 11.5% to 50.0%. However, when only 12% of the total watershed area was converted to carinata, the simulated reductions ranged from 3.8% to 14.0%. This suggests that the extent of carinata planting is crucial in assessing its hydrologic and water quality benefits. Overall, these results indicate that planting the biofuel carinata as a winter crop can reduce sediment and nutrient loading and provide water quality benefits to downstream waterbodies.

Understanding the effects of human disturbance on scorpion diversity in Brazilian tropical forests

The effects of land use conversion on the maintenance of biodiversity remains a major issue in conservation biology. With this as context, recent studies have successfully evaluated the potential of scorpions as bio-indicators of human disturbance. Here, we explored this assumption to identify the effects of landscape structure on scorpion assemblages distributed in two tropical environments in Brazil, with different levels of human disturbance. Scorpions were collected from 28 sampling localities across the Atlantic Forest (n = 12) and Caatinga dry forest (n = 16), resulting in 3,781 specimens from 13 species, 5 genera, and 2 families. We found that scorpion species composition and abundance were more sensitive to changes in landscape configuration than was species richness. Additionally, scorpion assemblage responses were quite different between the two environments. From this observation we highlighted three main findings: (i) the Atlantic Forest assemblage possesses an abundance-dependent response to landscape; (ii) variation in species composition of Atlantic Forest and Caatinga were affected by landscape diversity and presence of croplands, respectively; (iii) the Atlantic Forest is inhabited by assemblages that are more sensitive to landscape changes than that is Caatinga. We argue that a site-dependent process may explain the effects of human activities on scorpion assemblages at local and regional scale. Moreover, we provide substantial information for decision-makers to support their conservation strategies for neglected ecosystems, such as those present in Caatinga and the Atlantic Forest.

Impacts of land use change on ecosystem services in the intensive agricultural area of North China based on Multi-scenario analysis

Assessing the impacts of future land use scenarios on ecosystem services can provide theoretical basis and reference for sustainable land use management. This study combined scenario analysis and quantitative assessment to monitor land use and ecosystem services in the intensive agricultural area of Qixia city, North China under three different scenarios, i.e. natural development, farmland and orchard to forest and farmland to forest and orchard, by using the GeoSoS-FLUS and the InVEST models. The integrated land use change impact index (ILUCII) and the single land use change impact index (SLUCII) were proposed to quantitatively depict the impact of different land use change scenarios on ecosystem services. The results demonstrated that:(1)Under the three land use scenarios, forest, farmland and orchard show different change patterns. Slope influences the soil and water conservation services, land use in greater than 15° slope section occupied more soil and water conservation services than 12–15° section and less than 12° section. In the same slope section, forest had the most soil and water conservation services compared with orchard and farmland.(2)The effects of different land use conversion on soil conservation services per study grid (90*90 m) in less than 12° slope section showed an order of farmland-forest > orchard-forest > farmland-orchard. In more than 12° slope section, the order is farmland-forest > farmland-orchard > orchard-forest. The effects of land use conversion on water conservation services per grid is farmland - forest > orchard - forest > farmland-orchard.(3)The total ILUCII on ecosystem services found that farmland and orchard to forest scenario (16517.54) > farmland to forest and orchard scenario (13074.12) > natural development scenario (−4975.02). The mean ILUCII on ecosystem services showed that farmland to forest and orchard scenario (0.63) > farmland and orchard to forest scenario (0.53) > natural development scenario (−0.11). The mean SLUCII on ecosystem services found that greater than 15° farmland to forest (0.89) > 12–15°farmland to orchard (0.49) > greater than 15°orchard to forest (0.34).

Assessing the soil quality index as affected by two land use scenarios in Miandoab region

In this research, the physical, chemical and biological properties of 19 soil indicators using 80 samples (0–25 cm) were quantified to measure the soil quality index (SQI) in Miandoab region, Iran, across different land uses. These properties include aggregate stability (AS), bulk density (BD), soil moisture content (θm), saturation percentage (SP), particle size fractions (clay, silt, sand), pH, EC, available P and K, OC, total N, C/N, CaCO3, sequestration of organic carbon (SOC), CEC, microbial respiration (MR) and microbial population (MP). Principal component analysis (PCA) was used as a dimension reduction method to separate farmlands and orchards as two different land uses. The linear SQI and nonlinear SQI were calculated, and the results showed a clear difference in SQI as affected by the aforementioned land uses. The specific contribution of each minimum data set also showed that soil OC, N, MR, MP, silt, CaCO3, AS and BD had the highest importance to SQI. The linear SQI value was more significantly affected by the physical properties than the chemical and biological ones. It varies from the maximum value of 35.17% in the farmland to 37.74% in the orchard. On the other hand, the nonlinear SQI showed the highest contribution of biological SQI in the farmland (73.94%) followed by the orchard (64.15%). Finally, both linear and nonlinear equations may be acceptable for assessing SQI using the aforementioned soil properties. Furthermore, it is the biological properties that have the main role in terms of evaluating the effect of land use conversion on soil quality.

Landscapes and Lives in Transition: Effects of Land Use Conversion on Farmers

Landscapes and Lives in Transition: Effects of Land Use Conversion on Farmers

Unravelling the effects of tropical land use conversion on the soil microbiome

BackgroundThe consequences of deforestation and agricultural treatments are complex and affect all trophic levels. Changes of microbial community structure and composition associated with rainforest conversion to managed systems such as rubber and oil palm plantations have been shown by 16S rRNA gene analysis previously, but functional profile shifts have been rarely addressed. In this study, we analysed the effects of rainforest conversion to different converted land use systems, including agroforestry (“jungle rubber”) and monoculture plantations comprising rubber and oil palm, on soilborne microbial communities by metagenomic shotgun sequencing in Sumatra, Indonesia.ResultsThe diversity of bacteria and archaea decreased whereas diversity of fungi increased in the converted land use systems. The soil microbiome was dominated by bacteria followed by fungi. We detected negative effects of land use conversion on the abundance of Proteobacteria (especially on Rhizobiales and Burkholderiales) and positive effects on the abundance of Acidobacteria and Actinobacteria. These abundance changes were mainly driven by pH, C:N ratio, and Fe, C and N content. With increasing land use intensity, the functional diversity decreased for bacteria, archaea and fungi. Gene abundances of specific metabolisms such as nitrogen metabolism and carbon fixation were affected by land use management practices. The abundance of genes related to denitrification and nitrogen fixation increased in plantations while abundance of genes involved in nitrification and methane oxidation showed no significant difference. Linking taxonomic and functional assignment per read indicated that nitrogen metabolism-related genes were mostly assigned to members of the Rhizobiales and Burkholderiales. Abundances of carbon fixation genes increased also with increasing land use intensity. Motility- and interaction-related genes, especially genes involved in flagellar assembly and chemotaxis genes, decreased towards managed land use systems. This indicated a shift in mobility and interspecific interactions in bacterial communities within these soils.ConclusionsRainforest conversion to managed land use systems drastically affects structure and functional potential of soil microbial communities. The decrease in motility- and interaction-related functions from rainforest to converted land use systems indicated not only a shift in nutrient cycling but also in community dynamics. Fertilizer application and correspondingly higher availability of nutrients in intensively managed plantations lead to an environment in which interspecific interactions are not favoured compared to rainforest soils. We could directly link effects of land management, microbial community structure and functional potential for several metabolic processes. As our study is the first study of this size and detail on soil microbial communities in tropical systems, we provide a basis for further analyses.

Effect of Land Use Conversion on Surface Soil Heavy Metal Contamination in a Typical Karst Plateau Lakeshore Wetland of Southwest China.

Land use conversion could directly or indirectly influence heavy metal geochemistry by changing soil properties. The aim of this study was to explore the effect of land use conversion on surface soil heavy metal contamination in the karst plateau lakeshore wetlands of Southwest China. Based on this, a total of 120 soil samples were collected from 30 sites from different types of land uses (farmlands, grasslands and woodlands) around a lake in Suohuangcang National Wetland Park in August 2017. Contents of As, Cd, Cu, Cr, Hg, Pb and Zn were analyzed, and soil heavy metal contamination was assessed in all three land use types. Results showed that land use transformation from farmland to grassland or woodland was not conducive to the release of soil heavy metal. Surface soil of all three land use types have been moderately polluted by As, Cr, Pb, and Zn, and grassland and woodland also had moderate Cd contamination. The pollution load index (PLI) results revealed low heavy metal contamination in grassland and woodland but no contamination in farmland. Although the integrated contamination in the studied region did not pose a serious potential ecological risk (RI < 150), it might affect human health through the water supply and food chain. Therefore, it is necessary to monitor and control As, Cd, Cr, Pb, and Zn concentrations of surface soil through controlling pollutants, improving waste treatment, as well as strengthening supervision and management in the vicinity of the Suohuangcang National Wetland Park.