Adjacent Cropland Research Articles

Reduced ligninase‐cellulase ratio enhances soil carbon sequestration following afforestation of agricultural land

AbstractIntroductionAfforestation of agricultural land is one of the most essential approaches to mitigate climate change by enhancing the sequestration of atmospheric carbon (C) into the soil. C‐degrading extracellular enzymes produced by soil microbes regulated the decomposition and fate of sequestrated soil organic carbon (SOC), with potential divergent variations following afforestation across different ecosystem scales. However, the feedbacks of different C‐degrading enzymes and their relationships with SOC following afforestation of agricultural land remain unclear.Materials and MethodsWe investigated the changes in enzyme activity and their relationships with SOC in soil aggregates across two typical climatic vegetation restoration regions in China, and explored the mechanisms through which changes in enzyme activity contribute to SOC sequestration following afforestation of agricultural land.ResultsAfforestation of agricultural land generally decreased ligninase activity and increased cellulase activity across various aggregate fractions, compared to the adjacent croplands in both subtropic (Danjiangkou Reservoir, DJK) and temperate (Maoershan, MES) region. Additionally, the ratio of ligninase to cellulase (L:C) was lower in afforested lands than in the croplands, with L:C as the major factor explaining the variations of SOC sequestration following afforestation. Specifically, ligninase and L:C were negatively correlated with SOC, whereas cellulase showed positive correlations with SOC. Further analyses suggested that microbial biomass C and nitrogen (MBC and MBN) and the ratio of SOC and total nitrogen (SOC:TN) were important factors influencing L:C and subsequently regulating SOC. These results suggest that shifts in microbial enzyme production from ligninase to cellulase following afforestation, reduced the decomposition of recalcitrant C, thus contributing to SOC sequestration.ConclusionOur work underscores the critical role of reduced L:C in enhancing SOC sequestration following the restoration of croplands to afforested lands. These findings advance the understanding of the influence of microbial community physiological adaptations on C sequestration across different land use types.

Soil Quality Variation under Different Land Use Types and Its Driving Factors in Beijing

With the advancement of urbanization, land resources are becoming increasingly strained, particularly for urban greening purposes. In this context, a large number of newly cultivated lands dominated by construction waste and backfill soil are emerging in cities. Assessing the soil quality of these newly cultivated lands and achieving their rational utilization accurately and quantitatively has become an urgent issue. In this study, soil samples of five land use types, namely newly cultivated land (NCL, control), adjacent cropland (CL), arbor–shrub mixed forest (ASF), arbor forest (AF), and shrubland (SL) were selected around Beijing, China. ASF, AF, and SL are also newly cultivated lands composed of construction waste and backfill before greening. Based on principal component analysis (PCA), a total data set (TDS) and a minimum data set (MDS) were used to construct the soil quality index (SQI) model. Soil quality indicators covering the physical and chemical characteristics of the soil and their relationships with land use types were studied with the Partial Least Squares Path Model (PLS-PM). The results were summarized as follows: (1) The soil quality index under different land use types in the Beijing plain area were in the order of arbor–shrub mixed forest (ASF) > arbor forest (AF) > shrubland (SL) > cropland (CL) > newly cultivated land (NCL). (2) Soil organic carbon (SOC), soil water content (SWC), maximum water-holding capacity (MWHC), capillary water-holding capacity (CWHC), Pb, and Cd were identified as the MDS. The MDS of the soil quality assessment model showed a linear relationship with the TDS (y = 0.946x + 0.050, R2 = 0.51). (3) Land use types have an indirect impact on soil quality by changing the content of Pb. The chemical indicators’ coefficient (0.602) contributed more to the SQI than did the physical indicators’ (0.259) and heavy metal elements’ (−0.234). In general, afforestation and agricultural production could improve the newly cultivated lands’ soil quality, but afforestation is much better than agricultural production. These results will help to evaluate the SQI in the Beijing plain area objectively and accurately, and they have significant implications for soil restoration and management.

Contour prairie strips alter microbial communities and functioning both below and in adjacent cropland soils

Prairie strips are narrow strips of native, perennial vegetation (10–40 m width) integrated within cropped fields to provide benefits for water quality and biodiversity. However, the impact of prairie strips on soil microbial communities and function, both underneath the prairie strips and in the adjacent cropland, is not known. We assessed the effect of restoring native perennial vegetation on soil C and N, potential enzyme activities (PEA), and microbial community composition in the soil directly underneath and cropland adjacent (0.1 to 9 m) to 12-year-old prairie strips integrated within row crop fields. We found that prairie strips consistently increased soil microbial biomass carbon (>56 %) and altered PEA in complex ways. Generally, prairie strips increased hydrolase and decreased oxidoreductase PEA. Prairie strips also changed the soil microbial community directly under prairie vegetation, and, contrary to the expectation that greater plant diversity leads to greater soil microbial diversity, prairie strips reduced bacterial and fungal diversity. The prairie strip's effect on adjacent cropland soils depended on year, but it was strong when it occurred and was typically independent of distance from the prairie strip. Prairie strips increased PEA in adjacent soils (<9 m) by as much as 38 % and shifted bacterial and fungal beta diversity, but neither showed patterns with distance from the prairie strip, indicating that prairie strips cause field-scale shifts in soil biota and functioning, and these effects are not mediated by proximity to the prairie strip. Understanding the mechanisms underlying prairie strips' impact on soil biota, both underneath and adjacent to the prairie, is key to optimize their agroecosystem benefits.

The cooling and warming effects of potential forest transition on local land surface temperature in Northeast China

Forest cover change directly affects the surface energy balance by altering the radiative and non-radiative properties of the surface. These competing processes may yield considerable biophysical impacts on local and regional climate that depend on background climate and specific forest type. Here we compared the differences in land surface temperature (LST) between temperate forests and adjacent croplands/grasslands to quantify the potential biophysical effects of transitions from croplands/grasslands to forests in Northeast China, based on multiple satellite observation products from 2001 to 2016. Forests were found to show a slight lower daytime LST and strong higher nighttime LST than adjacent croplands or grasslands. As a result, the daily LST of forests was 0.15 ± 0.06 ℃ and 0.32 ± 0.04 ℃ higher than that of croplands and grasslands, respectively. On the seasonal scale, the warming effect of cropland/grassland-to-forest transition during non-growing season outweighed the cooling effect during growing season, and dominated the annual positive LST response. Moreover, the cooling effect of cropland-to-forest transition during growing season was stronger in the early growth stage than late growth stage (−1.65 ± 0.9 ℃ in May to June, −0.39 ± 0.5 ℃ in July to September). The net cooling effect of warm temperate broadleaved forests was found to shift toward net warming effect of cold temperate coniferous forests with increasing latitude. The daytime cooling effect of forests was mainly driven by increased non-radiative evapotranspiration. Overall, the radiative process related to the solar energy dominated the net warming effect of forest transitions over Northeast China. Estimating the climate feedback potential of forests could be useful to provide theoretical references for the adaptation and mitigation strategies for climate change.

Cropland compensation in mountainous areas in China aggravates non-grain production: evidence from Fujian Province

The large-scale non-grain production (NGP) on cropland poses a potential threat to national food security, which has attracted the attention of the Chinese government. As a hotspot of NGP, mountainous cropland has undergone dramatic changes in its distribution pattern, influenced by China's cropland requisition-compensation balance system. Consequently, the NGP on compensated cropland (CCL) has become an unstable factor in grain production in mountainous areas. This paper analyzes the distribution pattern of CCL in Fujian Province, a typical mountainous area in China, identifies and compares the NGP characteristics between original cropland (OCL) and CCL, and explores its driving mechanism based on the physico-geographical environment, the socio-locational environment, and the resource endowment attributes, using the boosted regression trees (BRT) model. Results show that from 2009 to 2019, CCL tended to shift towards higher elevation and steeper terrain in the vertical zone and towards inland agricultural districts and counties in the western and northern horizontal zones. The NGP rate of CCL reached 16%, about twice that of OCL, and the proportion of instable cropland was also higher. Travel distance to adjacent cropland and slope were the main driving factors for NGP of CCL, followed by patch area, agricultural population density, and suitability of machine tillage. These factors exhibited differentiated marginal effects in their different threshold intervals and did not follow a simple one-way action mechanism. Furthermore, the analysis of pairwise interaction effects between variables identified the four most powerful combinations, which were slope-elevation, travel distance to adjacent cropland-elevation, slope-travel distance to adjacent residential area, and travel distance to adjacent cropland–aspect; within their specific value ranges, NGP is highly likely. Finally, we optimized the current evaluation system for reserved cropland resources based on these value ranges and selected Jianyang County, Dehua County, Zhao’an County, across the Fujian Province, as the area to adjust the reclamation strategy of future reserved cropland resources.

Seasonal dynamics of agricultural land use impacts on earthworm communities: Insights into diversity, abundance, and functional composition

Earthworms play a key role as soil bioengineers, but livestock farming and croplands can impact on the composition, structure, and functioning of earthworm communities. This study aimed to quantify the effects of replacing natural grasslands with crop rotations on the seasonal dynamics of key attributes of earthworm communities and explore soil physicochemical properties as mechanisms behind these effects. We conducted paired samplings on seven sites across Uruguay, comparing earthworm communities in soils under grazed natural grasslands and adjacent croplands, considering earthworm species composition, richness, diversity, and evenness, biomass, density, and mean body weight, over five consecutive seasons. Results revealed a clear negative impact of croplands on earthworm communities, showing substantial reductions in all considered attributes. Observed changes were attributed to environmental filters limiting the occurrence of larger exotic earthworm species in croplands, and variations in soil physicochemical properties were identified as potentially mediating some of these effects, including soil water regime (particularly affecting juvenile individuals) and soil organic matter content. These impacts resulted in a shift to dominance of r strategists (smaller, surface-feeding species such as Microscolex spp. in croplands compared to larger deeper-burrowing species in grasslands) and reduced functional composition of earthworm communities. Furthermore, seasonal dynamics revealed that differences between land uses were more pronounced during wetter periods, underscoring the relevance of seasonal variations when evaluating land use impacts on earthworm communities. Earthworms mean body weight resulted a useful attribute to be included in earthworm's assessments, allowing to identify impacts in community functional composition and suggesting size dependent mechanisms. Additional research is required to comprehensively understand the mechanisms behind these patterns and to develop more sustainable agricultural practices by considering soil fauna.

Tritium and trees: A bomb peak perspective on soil water dynamics in semi-arid apple orchards

Understanding the relationship between agroforest age and soil water dynamics is crucial for effective land and water resources management. However, the complexities of these dynamics, such as soil water recharge and depletion, hamper in-depth understanding, particularly in water-scarce regions. In this study, we examined soil water recharge and depletion in relation to the stand age of apple trees, a widely planted and representative deep-rooted agroforest, over four years in a semi-arid region on China’s Loess Plateau (CLP). We collected soil cores to >20 m depth from four apple orchards (referred to as ‘agroforests’) with variable stand ages (established in 2008, 2005, 1998, and 1994). For comparison, we selected adjacent cropland as land use prior to agroforestry practices (‘control’). We measured soil water content and tritium distributions to model soil water dynamics and estimate water ages across different soil profiles. Our results show that recharge amounts (and depths) in shallow soils were 298.4 mm (7 m), 303.4 mm (6.6 m), 300.6 mm (5.4 m), and 483.1 mm (7.6 m), whereas deep soils had net depletions of 111.1 mm, 391.9 mm, 192.8 mm, and 108.9 mm for AP2008, AP2005, AP1998, and AP1994, respectively. The tritium peak depths, which indicate the 1963 bomb peak depth, significantly differed between agroforested and non-agroforested plots. In particular, agroforestation reduced the seepage velocity of soil water over 20 years. Furthermore, our tritium tracer water age model suggests that the age of transpired deep soil water exceeded 200 years in the oldest orchard. These findings highlight a complex interaction between newly infiltrated water and existing water, possibly due to variations in soil pore size distributions. The results of this study offer valuable insights into the ecohydrological impacts of agroforestation on the CLP and in similar climatic regions.

Spatial patterns in pollution discharges from livestock and poultry farm and the linkage between manure nutrients load and the carrying capacity of croplands in China

The rapid development of livestock and poultry farming in China has resulted in an increasing threat of water pollution. In particular, mitigating livestock-related pollutant discharges is a key issue for environmental sustainability, especially for inland surface water bodies. In order to ensure the effective control of pollution and the efficient utilization management of livestock manure, spatially explicit surveys of pollutant generation and discharge from the livestock sector must be performed. In the present study, we estimated the grid cell-level distributions in the generation and discharge of four typical pollutants (chemical oxygen demand, ammonium nitrogen, total nitrogen and total phosphorus) from the livestock sector across the country with a spatial resolution of 30 arc-seconds. The distributions were estimated using the most recent pollution source census data and multi-sourced ancillary materials by a dasymetric mapping approach. We further investigated the feasibility of the resource utilization of livestock manure by comparing manure-source nutrients with the carrying capacity of adjacent croplands. Our results show that low-intensive farming generated and discharged the majority of livestock farming pollution, with other cattle and pigs breeding identified as the two major sources of pollution from the livestock sector. Southwest, Central and East China suffered the highly densified pollutants generation and discharges. Furthermore, cropland exceeding its carrying capacity was concentrated in these regions. Our findings provide additional insights into livestock and poultry farming in the context of relocation, strengthening regulation, transforming breeding operations, and rationalizing the resource use of manure, all of which are important measures for the sustainable development of both agriculture and the environment.

Apple trees can extract soil water from both deep layers and neighboring cropland in the tableland region of Chinese Loess Plateau

It is of great significance to explore soil water distribution and consumptions of the agroforestry systems in water-deficient areas. In recent decades, continuous development of apple orchards in the southern Chinese Loess Plateau has formed the orchard-cropland mosaic vegetation pattern. In this study, soil water content (SWC) in two series were measured, (1) 0–21 m soil profiles of five apple orchards with different stand ages (5, 10, 15, 20 and 24 years) and one cropland; (2) 0–6 m soil profiles at different sites within the orchard-cropland border zone (with apple orchard aged 10 and 24 years old, denoted as AC10 and AC24, respectively). Results showed that (1) the water consumption depth of apple orchards increased in an “S”-shaped pattern with stand age and reached 20 m after 20 years, while the average SWC within 3–21 m layer decreased and the soil water deficits increased at a rate of 5.8 mm m−1 yr−1; and (2) the average SWC in 3–10 m layer of 15, 20 and 24-year-old orchards accounted for 69.3%, 64.2% and 57.9% of the field capacity, respectively, these proportions came to 71.2%, 67.4% and 61.1% in the 3–21 m layer, respectively; and (3) AC24 had greater influence on SWC of adjacent cropland than AC10. The soil water storage of 2–6 m layer in AC24 ranged from 713 mm to 879 mm within 7 m away from the orchard, which were significantly lower than those of 7–15 m away from the orchard (933–1042 mm). Overall, the apple tree root system can absorb soil water from a depth of 20 m in the vertical direction and up to 7 m from the adjacent cropland in the horizontal direction. Therefore, a reasonable orchard-cropland mosaic pattern should be arranged in regional agricultural planning, so as to promote the optimized utilization of regional soil water resources, and to coordinate the development of fruit industry and food security, in which the width of a cropland can’t be < 14 m.

Afforestation Alters the Molecular Composition of Soil Organic Matter in the Central Loess Plateau of China

Many studies have been conducted on organic carbon changes under different land use patterns, but studies and data concerning changes in the molecular composition of soil organic matter (SOM) during land use conversion are scarce. In this work, we studied the chemical composition of SOM on two Robinia pseudoacacia L. plantations and their adjacent croplands in the Loess Plateau using biomarker and nuclear magnetic resonance (NMR) techniques. Experimental data on the molecular composition of SOM showed that the soil microbial biomass carbon content initially decreased and then returned to the original level gradually after afforestation, while the SOM content and stocks increased over time. At the initial stage of afforestation, the content of total solvent extracts did not change significantly but changed slowly over time in the plantations without artificial disturbance. With an increase in restoration time, the concentrations of both the microbial- and plant-derived solvent extracts increased. Moreover, the concentrations of plant-derived solvent extracts were consistently lower than those of microbial-derived solvent extracts. Afforestation also significantly increased the lignin-derived phenol content in the surface soil layer (0–10 cm). However, no obvious change was observed in the lignin-derived phenols of the two adjacent croplands. These results indicate that the accumulation of aboveground litter and underground roots has the strongest effects on the lignin-derived phenol content. In contrast to cropland, the two plantations exhibited a high degree of degradation of lignin-derived phenols in the surface soil, but this remained almost unchanged over time. Moreover, in contrast to 20 years after the establishment of the R. pseudoacacia plantation, the low alkyl/O-alkyl carbon ratio of the 8-year R. pseudoacacia plantation indicated that more easily degradable components accumulated during the initial stage of afforestation. Therefore, the proportion of the unstable carbon pool was relatively high and the SOM content may decline in the early stage of afforestation. These results provide evidence illustrating the detailed changes in the chemical composition of SOM during the ecological restoration process.

Characterization of soils under different periods of eucalyptus cultivation and restoration in Malur and Hoskotetaluks of Karnataka, India

Considerable area under eucalyptus plantation in the form of farm forestry exists in Malur and Hoskotetaluks of Karnataka, India. But in the recent years, Government of Karnataka has checked the spread of eucalyptus and farmers are gradually converting their eucalyptus plantations into agricultural lands. This study was aimed to evaluate soils of eucalyptus during growing and after restoration and its adjacent croplands having no history of eucalyptus cultivation in Taluks of Malur and Hosakote, Karnataka for physico-chemical properties and evaluated during the year 2019-2020 at College of Horticulture, Kolar. The results revealed that soils under 12, 24 and 48 years of eucalyptus cultivation when compared to soils after two, six and ten years of restoration and adjacent soils, showed significantly high bulk density (1.28 to 1.51 Mg/m3) and low water holding capacity (30.30 to 45.61%). These soils were more acidic in reaction (pH: 6.21 to 6.65) and contained significantly lower amounts of total soluble salts (EC: 0.04 to 0.07 dS/m), organic carbon (OC: 0.24 to 0.59%), available N, P2O5 and K2O (163.07 to 235.42, 26.03 to 47.23 and 112.89 to 168.55 Kg/ha, respectively), exchangeable Ca and Mg (1.70 to 2.75 and 0.80 to 1.32 cmol (p+)/Kg, respectively) and available S (5.60 to 7.09 ppm) but contained significantly high amounts of available Fe, Mn, Zn and Cu (13.52 to 29.74, 14.06 to 20.14, 1.44 to 2.06 and 1.16 to 1.74 ppm, respectively). Further, bulk density, acidity and available micronutrient cations of soils tends to increase with prolonging the cultivation period of eucalyptus while, reverse trend was observed with respect to water holding capacity, organic carbon and available macronutrients contents. On the other hand, restored plots showed significantly decreased acidity, bulk density and available micronutrient cations and increased water holding capacity and macronutrients contents with increasing the restoration period.

Afforestation inhibited soil microbial activities along the riparian zone of the upper Yangtze River of China

Afforestation strongly influences soil microbial traits, especially microbial biomass and enzyme activity. However, the magnitude and direction of soil microbial traits and their controls following afforestation remain unclear. Here, we examined microbial carbon (C), nitrogen (N), and phosphorus (P) biomass and activities of the most common enzymes involved in C (α-1,4-glucosidase, β-1,4-glucosidase, β-D-1,4-cellobiohydrolase, and β-1,4-xylosidase), N (β-1,4-N-acetyl-glucosaminidase and l-leucine aminopeptidase), and P (alkaline phosphatase) cycling under a 15-year-old forest stands (Morus alba, Salix bablyonica, and a mix of the two species) and adjacent croplands along the riparian zone of the upper Yangtze River of China. Unexpectedly, we found that the 15-year afforestation significantly lowered the contents of total C and N, available P, and NO3– compared to the adjacent cropland soils. The microbial biomass C, N, and P contents were also approximately 14–60%, 34–88%, and 9–89% lower, respectively, in the afforested soils than in the adjacent cropland soils across afforestation types and soil depths. Correspondingly, enzymatic C and N activities were 71–90% and 54–75% lower, respectively, under the S. bablyonica stands across soil depths, whereas enzymatic P activity was 39–72% lower in the afforested soils than in the adjacent cropland soils across afforestation types and depths. Reduced microbial biomass and enzymatic activities after afforestation were attributed to the decreased total C and nutrients in the afforested soils than in the adjacent cropland soils, likely due to high plant uptake nutrients and low soil organic matter inputs during the early stages of forest development. Overall, afforestation with plantations of Morus alba or Salix bablyonica species may reduce soil functions such as C storage and N fertility, suggesting that large-scale afforestation using these species should not be prioritized to restore soil functions within a short period.

Dynamic responses of soil aggregate-associated organic carbon and nitrogen to different vegetation restoration patterns in an agro-pastoral ecotone in northern China

Soil aggregates are the basic soil structure units and they have important effects on the accumulation and stability of soil organic carbon (OC) and nitrogen (N). However, the responses of OC and N in bulk soils and aggregates to the restoration plant type and time in ecologically fragile regions with low clay contents require elucidation. Thus, to determine the dynamics and distributions of soil OC and N under different vegetation restoration processes, we investigated four revegetation patterns (Caragana microphylla, grassland, apricot trees, and Chinese pines) within different recovery times (5–25 years) in an agro-pastoral ecotone in northern China, with adjacent cropland as the control. The OC and N contents were measured in the bulk soils and aggregate fractions, and the geometric mean diameter (GMD) and mean weight diameter (MWD) were calculated. The results indicated that the mass of the soil was dominated by microaggregates when averaged across the four revegetation patterns, followed by silt plus clay, and macroaggregates comprised the lowest mass. Microaggregates contributed significantly more OC and N to the bulk soil due to their large mass. Revegetation significantly increased the mass percentage of macroaggregates, MWD, and GMD (P < 0.005). The increases in the OC and N concentrations in bulk soil and aggregates induced by revegetation were related to the soil depth and vegetation type, where the highest increases occurred in each aggregate fraction with Caragana microphylla and grassland at a soil depth of 0–10 cm. These results demonstrate that revegetation of abandoned cropland has great potential for sequestering OC and N in the bulk soil and each aggregate fraction, especially with C. microphylla and grassland.

Spatiotemporal distribution patterns and ecological risk of multi-pesticide residues in the surface water of a typical agriculture area in China

This study systematically investigated the occurrence, spatiotemporal distribution, and ecological risk of 106 pesticides in the surface water of the Jiaodong Peninsula in China. The results show that 52 pesticides, including 21 insecticides, 10 fungicides, and 21 herbicides, were detectable in the surface water. The concentrations of target pesticides in water samples ranged from 0.42 (tebuconazole in the wet season) to 645.31 ng/L (thiamethoxam in the normal season). The two most polluting and widespread pesticides were quintozene (maximum concentration of 481.46 ng/L and detection rate of 94 %) and atrazine (maximum concentration of 465.73 ng/L and detection rate of 100 %). The total pesticide concentrations in surface water in different seasons revealed the order of dry season > wet season > normal season. Based on aquatic pesticide concentrations, their frequency of occurrence, and effect concentrations, insecticides posed higher risks to aquatic organisms and human health than either fungicides or herbicides. Total pesticide concentrations were significantly positively correlated with suspended particulate matter, dissolved organic carbon, soil pH, normalized difference vegetation index, adjacent cropland area; and were negatively associated with adjacent grassland area. The cropland area largely influences pesticide distribution in the surface water of the Jiaodong Peninsula.

Decades of reforestation significantly change microbial necromass, glomalin, and their contributions to soil organic carbon

Microbial necromass carbon (MNC) and glomalin-related soil protein (GRSP) are stable microbe-derived sources of carbon (C) in soils. MNC constitutes a considerable portion of soil organic carbon (SOC). GRSP is beneficial for soil aggregation, quality improvement, and C storage. However, the impact of land use transitions from croplands to forests on MNC, GRSP, and their contributions to SOC are not fully understood. To illuminate these unclear dynamics, soil was collected at depths of 0–10 cm from 30 pairs of adjacent corn fields and woodlands in southwest China. These woodlands, mainly consisting of fir, pine, and rubber, were converted from croplands approximately two decades ago. Soil properties, SOC, MNC, and GRSP content were determined. We found that SOC content increased significantly by 23.24% following reforestation. Additionally, the MNC and total GRSP contents were 46.01% and 20.48% higher, respectively, in woodland soils than in adjacent cropland soils. The contribution of MNC to the SOC pools also significantly increased and their quantities were proportional to the increasing contribution of GRSP to SOC. In woodlands, soil NH4+-N content is the major factor regulating the accumulation of MNC. For cropland systems, the easily extractable GRSP showed a strong positive correlation with MNC accumulation. Overall, our findings show that reforestation from croplands is conducive to soil C sequestration. The positive relationship between the contributions of GRSP and MNC to SOC provides valuable information in terms of enhancing our understanding of mechanisms underlying the maintenance of soil C stocks through microbe-derived C.

Growing season water and salt migration between abandoned lands and adjacent croplands in arid and semi-arid irrigation areas in shallow water table environments

In arid and semi-arid irrigation areas with shallow water tables and fragmented arrangement of croplands and abandoned lands, dry drainage could be an optional management practice mitigating soil salinization. A dry drainage system lets non-irrigated abandoned lands serve as evaporative salt sinks receiving water and salt fluxes from adjacent irrigated croplands. Therefore, this research takes a typical dry drainage unit in the Hetao Irrigation District—one abandoned land and its adjacent croplands—as an example to directly reveal the field scale water and salt migration between abandoned lands and adjacent croplands. It was found that during the growing season, the water input, i.e. field irrigation and precipitation, raised the water table of the croplands and drove water and salt migration from croplands to the abandoned lands. However, the evapotranspiration in the croplands was also larger than that in the abandoned lands. Thus, during the intervals of irrigation (the “phreatic evaporation periods”), in some circumstances, evapotranspiration could drive water and salt flux from the abandoned lands to the croplands, which would influence the groundwater salinity of the croplands. Therefore, it is recommended to plant halophytes on the abandoned lands to enhance its evapotranspiration and hinder the water and salt flux from the abandoned lands to the croplands during intervals of irrigation. This management practice could help form more effective dry drainage systems between abandoned lands and adjacent croplands, and help better control the root zone salinity of the croplands.

Tree-based land uses enhance the provision of ecosystem services in agricultural landscapes of the Peruvian highlands

Trees can have important impacts on multiple ecosystem services and biodiversity in agricultural landscapes. The influence of trees can extend beyond forested areas and into adjacent land uses, however, this is rarely accounted for in the ecological literature. To better understand the influence of trees in Andean agroecosystems, we examined alternative landscape scenarios in the community of Quilcas (Junín, Peru), where we explored the potential impact of replacing tree-based land uses (with crops and pasture) on landscape carbon (C) storage and soil biodiversity (soil macrofauna and ground vegetation). Additionally, we estimated the influence of tree-based land uses on soil C storage (0–20 cm depth) and macrofauna diversity in adjacent croplands and pastures. Tree-based land uses were dispersed across the landscape and occupied 26 % of the area, including a mix of forest patches, plantations, and hedgerows. Given that above- and belowground C stocks were generally higher in land uses with trees versus those without, the inclusion of trees in this landscape is estimated to increase the total landscape C storage by 153 %. Macrofauna diversity also varied across different land uses, being highest in alder (Alnus acuminata) forests and hedgerows, such that the inclusion of trees enhances overall macrofauna diversity (Shannon Index) by 25 % but appears to have a slightly negative effect (−6 %) on ground vegetation diversity. When accounting for the influence of trees on adjacent land uses, estimates for overall soil C storage at the landscape scale increased by 1.4 %, while macrofauna diversity increased by approximately 5 %. Our findings indicate that the addition of trees can greatly enhance overall C stocks and soil macrofauna diversity in agricultural landscapes, and that it is important to consider spatial interactions between land uses to fully quantify and optimize these interactions.

Review on the role of soil and water conservation practices on soil properties improvement in Ethiopia

Soil erosion is one of several major deterioration processes which result in soil degradation and declining agricultural productivity in Ethiopia due to the dense population, high livestock density, and intensive crop production in the area. Soil and water conservation practices are one of the mechanisms used to reduce erosion and associated nutrient loss, reducing the risk of production. Therefore, the review focuses on the importance of soil and water conservation practices on soil properties in Ethiopia. Several studies conducted in various parts of the country showed that the implemented soil bund reduced annual runoff and soil loss at different rates. Soil and water conservation have improved the soil Physico-chemical properties on conserved cropland (BD, SMC, pH, CEC, av. K, av. P, SOC, and TN) compared to the adjacent cropland without soil and water conservation measures. Soil and water conservation, reduce the removal of fertile topsoil and improves soil moisture, which favors crop growth as a result grain yield of the crops was increased. In general, the use of soil and water conservation strategies had clearly shown a positive impact on soil physico-chemical properties and crop yields. Therefore, to reduce soil erosion sustainably, different soil and water conservation options should be introduced and used considering agroecology, socio-economic profile, and climatic condition of the intervention area.

Soil CO2 emissions in cropland with fodder maize (Zea mays L.) with and without riparian buffer strips of differing vegetation

Vegetated land areas play a significant role in determining the fate of carbon (C) in the global C cycle. Riparian buffer vegetation is primarily implemented for water quality purposes as they attenuate pollutants from immediately adjacent croplands before reaching freashwater systems. However, their prevailing conditions may sometimes promote the production and subsequent emissions of soil carbon dioxide (CO2). Despite this, the understanding of soil CO2 emissions from riparian buffer vegetation and a direct comparison with adjacent croplands they serve remain elusive. In order to quantify the extent of CO2 emissions in such an agro system, we measured CO2 emissions simultaneously with soil and environmental variables for six months in a replicated plot-scale facility comprising of maize cropping served by three vegetated riparian buffers, namely: (i) a novel grass riparian buffer; (ii) a willow riparian buffer, and; (iii) a woodland riparian buffer. These buffered treatments were compared with a no-buffer control. The woodland (322.9 ± 3.1 kg ha− 1) and grass (285 ± 2.7 kg ha− 1) riparian buffer treatments (not significant to each other) generated significantly (p = < 0.0001) the largest CO2 compared to the remainder of the treatments. Our results suggest that during maize production in general, the woodland and grass riparian buffers serving a maize crop pose a CO2 threat. The results of the current study point to the need to consider the benefits for gaseous emissions of mitigation measures conventionally implemented for improving the sustainability of water resources.

Agroforestry perennials reduce nitrous oxide emissions and their live and dead trees increase ecosystem carbon storage.

Agroforestry systems (AFS) contribute to carbon (C) sequestration and reduction in greenhouse gas emissions from agricultural lands. However, previously understudied differences among AFS may underestimate their climate change mitigation potential. In this 3-year field study, we assessed various C stocks and greenhouse gas emissions across two common AFS (hedgerows and shelterbelts) and their component land uses: perennial vegetated areas with and without trees (woodland and grassland, respectively), newly planted saplings in grassland, and adjacent annual cropland in central Alberta, Canada. Between 2018 and 2020 (~April-October), nitrous oxide emissions were 89% lower under perennial vegetation relative to the cropland (0.02 and 0.18gN m-2 year-1 , respectively). In 2020, heterotrophic respiration in the woodland was 53% lower in shelterbelts relative to hedgerows (279 and 600 g C m-2 year-1 , respectively). Within the woodland, deadwood C stock was particularly important in hedgerows (35 MgC ha-1 or 7% of ecosystem C) relative to shelterbelts (2Mg C ha-1 or <1% of ecosystem C), and likely affected C cycling differences between the woodland types by enhancing soil labile C and microbial biomass in hedgerows. Deadwood C stock was positively correlated with annual heterotrophic respiration and total (to ~100 cm depth) soil organic C, water-soluble organic C, and microbial biomass C. Total ecosystem C was 1.90-2.55 times greater within the woodland than all other land uses, with 176, 234, 237, and 449 Mg C ha-1 found in the cropland, grassland, planted saplings treatment, and woodland, respectively. Shelterbelt and hedgerow woodlands contained 2.09 and 3.03 times more C, respectively, than adjacent cropland. Our findings emphasize the importance of AFS for fostering C sequestration and reducing greenhouse gas emissions and, in particular, retaining hedgerows (legacy woodland) and their associated deadwood across temperate agroecosystems will help mitigate climate change.