Effects Of Land Management Change Research Articles

Exploring the effects of land management change on productivity, carbon and nutrient balance: Application of an Ensemble Modelling Approach to the upper River Taw observatory, UK

Agriculture is challenged to produce healthy food and to contribute to cleaner energy whilst mitigating climate change and protecting ecosystems. To achieve this, policy-driven scenarios need to be evaluated with available data and models to explore trade-offs with robust accounting for the uncertainty in predictions. We developed a novel model ensemble using four complementary state-of-the-art agroecosystems models to explore the impacts of land management change. The ensemble was used to simulate key agricultural and environmental outputs under various scenarios for the upper River Taw observatory, UK. Scenarios assumed (i) reducing livestock production whilst simultaneously increasing the area of arable where it is feasible to cultivate (PG2A), (ii) reducing livestock production whilst simultaneously increasing bioenergy production in areas of the catchment that are amenable to growing bioenergy crops (PG2BE) and (iii) increasing both arable and bioenergy production (PG2A + BE). Our ensemble approach combined model uncertainty using the tower property of expectation and the law of total variance. Results show considerable uncertainty for predicted nutrient losses with different models partitioning the uncertainty into different pathways. Bioenergy crops were predicted to produce greatest yields from Miscanthus in lowland and from SRC-willow (cv. Endurance) in uplands. Each choice of management is associated with trade-offs; e.g. PG2A results in a significant increase of edible calories (6736 Mcal ha−1) but reduced soil C (−4.32 t C ha−1). Model ensembles in the agroecosystem context are difficult to implement due to challenges of model availability and input and output alignment. Despite these challenges, we show that ensemble modelling is a powerful approach for applications such as ours, offering benefits such as capturing structural as well as data uncertainty and allowing greater combinations of variables to be explored. Furthermore, the ensemble provides a robust means for combining uncertainty at different scales and enables us to identify weaknesses in system understanding.

Exploring the Effects of Land Management Change on Productivity, Carbon and Nutrient Balance: Application of a Hierarchical Modelling Approach to the Upper River Taw Observatory, UK

Exploring the Effects of Land Management Change on Productivity, Carbon and Nutrient Balance: Application of a Hierarchical Modelling Approach to the Upper River Taw Observatory, UK

Effects of land management change on soil aggregates and organic carbon in Mediterranean olive groves

Carbon sequestration in agricultural soils has been defined as a positive strategy in the mitigation of global warming. The selection of the appropriate soil management system to achieve this goal is fundamental. In this study the effect of two tillage treatments, conventional tillage (CT) and no tillage with bare soil (NT) was analyzed in the complete soil profile (by horizons) in a rainfed olive grove under Mediterranean conditions. The objective was to determine the influence of treatments on soil aggregation and organic carbon (OC) distribution within aggregate fractions both in the surface horizon (0–32.7 cm in CT and 0–21 cm in NT) and in depth (32.7–119.7 cm in CT and 21.7–110 cm in NT) (Bw, BC and C horizons). Soil samples from all horizons were separated into four aggregate-size fractions: large macroaggregates (>2000 μm), small macroaggregates (250–2000 μm), microaggregates (53–250 μm), and silt + clay (<53 μm) by wet-sieving method. Aggregate stability results showed that mean weight diameter of aggregates (MWD) increased in depth in both treatments and the A horizon contained 47.6% (CT) and 55.8 (NT) more percentage of microaggregates. NT obtained greater MWD values (0.76 vs. 0.61 mm) and more proportion of water stable large macroaggregates (15.9% vs. 6.6%) than CT only in the A horizon. Conversely, CT achieved higher MWD values than NT in the depth and more proportion of macroaggregates (large macroaggregates + small macroaggregates) were found in CT in all depths. In addition, CT had larger contribution to SOC stock within aggregate fractions (24.9 Mg ha−1) than NT (22.4 Mg ha−1). This study indicates that the adoption of NT with bare soil did not increase the OC pool in aggregate fractions and therefore it is not always the best option management change to increase SOC in Mediterranean areas.

Short-term effects of land management change linked to cover crop on soil organic carbon in Mediterranean olive grove hillsides

The spatial distribution of soil organic carbon (SOC) is essential to estimate the SOC reserves. Therefore, the soils ability to store organic carbon is a key factor for climate regulation and for other soil functions. The soil management and the topographic position play an important role in SOC variation, especially when the landscape is not uniform (Mediterranean areas). Many researches have explored the SOC distribution according to topographic position in hillsides for long-term, but very few studies have focused on the short term. Therefore, it is necessary to know, the changes that taking place in the soil due to land management change (LMC) in these irregular surfaces for sustainable agricultural production and its implications on climate change regulation.This study aims to assess the influence of topographic position and LMC on SOC stock (SOC-S) in Mediterranean olive groves (OG) soils in short term (2 years). In this line, three experimental plots were selected in three topographical position (summit - S, backslope - B and toeslope - T). In these plots, the land management was modified from conventional tillage (CT) to no tillage (NT) with application of pruned olive branch chippings branches and vegetation cover (spontaneous vegetation) in the OG streets.The studied soils did not show important changes due to LMC in their physical properties for short term, in addition, these soils were characterized by low organic matter content (<1.2%). LMC caused a SOC reduction in surface, and a SOC increase in the Bw horizon. The N concentrations showed a similar trend to SOC and the C:N ratios were highly variable (4.37: C horizon-NT-S; 13.45 Bw/C horizon -CT-B). Normally, the SOC-S concentrations decreasing in depth. LMC for two years showed soil carbonization (S and T position) and decarbonization (B position) processes. The SOC-S increased 1.88 Mg ha−1 y−1 and 0.47 Mg ha−1 y−1 for S and T topographic position respectively, however the SOC-S decreased in B position 5.27 Mg ha−1 y−1. Therefore, LMC has a positive effect on soil carbon reserves in S and T position, conversely in B position, this effect was negative.

Modelling the Effect of Land Management Changes on Soil Organic Carbon Stocks in a Mediterranean Cultivated Field

AbstractLand management in agricultural lands has important effects on soil organic carbon (SOC) dynamics. These effects are particularly relevant in the Mediterranean region, where soils are fragile and prone to erosion. Increasing interest of modelling to simulate SOC dynamics and the significance of soil erosion on SOC redistribution have been linked to the development of some recent models. In this study, the SPEROS‐C model was implemented in a 1.6‐ha cereal field for a 150‐year period covering 100 years of minimum tillage by animal traction, 35 years of conventional tillage followed by 15 years of reduced tillage by chisel to evaluate the effects of changes in land management on SOC stocks and lateral carbon fluxes in a Mediterranean agroecosystem. The spatial patterns of measured and simulated SOC stocks were in good agreement, and their spatial variability appeared to be closely linked to soil redistribution. Changes in the magnitude of lateral SOC fluxes differed between land management showing that during the conventional tillage period the carbon losses is slightly higher (0.06 g C m−2 yr−1) compared to the period of reduced till using chisel (0.04 g C m−2 yr−1).Although the results showed that the SPEROS‐C model is a potential tool to evaluate erosion induced carbon fluxes and assess the relative contribution of different land management on SOC stocks in Mediterranean agroecosystems, the model was not able to fully represent the observed SOC stocks. Further research (e.g. input parameters) and model development will be needed to achieve more accurate results. Copyright © 2016 John Wiley &amp; Sons, Ltd.

A new LandscapeDNDC biogeochemical module to predict CH4 and N2O emissions from lowland rice and upland cropping systems

Replacing paddy rice by upland systems such as maize cultivation is an on-going trend in SE Asia caused by increasing water scarcity and higher demand for meat. How such land management changes will feedback on soil C and N cycles and soil greenhouse gas emissions is not well understood at present. A new LandscapeDNDC biogeochemical module was developed that allows the effect of land management changes on soil C and N cycle to be simulated. The new module is applied in combination with further modules simulating microclimate and crop growth and evaluated against observations from field experiments. The model simulations agree well with observed dynamics of CH 4 emissions in paddy rice depending on changes in climatic conditions and agricultural management. Magnitude and peak emission periods of N 2 O from maize cultivation are simulated correctly, though there are still deficits in reproducing day-to-day dynamics. These shortcomings are most likely related to simulated soil hydrology and may only be resolved if LandscapeDNDC is coupled to more complex hydrological models. LandscapeDNDC allows for simulation of changing land management practices in SE Asia. The possibility to couple LandscapeDNDC to more complex hydrological models is a feature needed to better understand related effects on soil-atmosphere-hydrosphere interactions.

Impact of Sampling Depth on Differences in Soil Carbon Stocks in Long‐Term Agroecosystem Experiments

The depth of sampling has recently been highlighted as critical to making accurate measurements of changes in SOC stocks. This paper aimed to determine the effects of land management changes (LMC) on soil organic carbon (SOC) by re‐sampling long‐term agoecosystem experiments (LTAEs) across Canada using identical sampling and laboratory protocols. The impact of sampling depth on the monitoring of LMC‐induced differences in SOC stock in LTAEs in Canada, and the implications on statistical power and sampling design, were assessed. In most cases, four cores would be suitable for detecting a significant difference in SOC stock of 5 Mg ha−1 at 95% confidence for LMCs in western Canada. The impact of eliminating fallow on SOC stocks was typically restricted to the surface 15 cm. The impact of perennial forages on the average cumulative SOC was sufficiently large to be detectable at all sampling depths (to 60 cm). In three of the six LTAEs sampled in western Canada comparing conventional tillage to no‐till, there was a significantly greater SOC storage in the 0‐ to 30‐depth than the 0‐ to 15‐cm depth, suggesting that sampling below 15 cm could be necessary. The same comparisons in eastern Canada suggested that sampling often must exceed the 30‐cm depth to account for any changes in SOC due to moldboard plow tillage. Nonetheless, there was little evidence to suggest that increasing sampling intensity or sampling deeper would improve the ability to detect a difference in SOC stocks for this LMC.

Soil organic carbon stocks on long-term agroecosystem experiments in Canada

Several long-term agroecosystem experiments (LTAEs) across Canada have been maintained for periods of up to a century. Much scientific knowledge of changes in soil properties through time has been learned from these few, highly productive LTAEs. We determined the effects of land management changes (LMC) on soil organic carbon (SOC) by re-sampling 27 LTAEs across Canada using identical sampling and laboratory protocols. Seven LTAEs were sampled comparing perennial to annual cropping and it was found that SOC stocks (0-30 cm) were 9.0 ± 1.5 Mg C ha-1 higher under perennial cropping after an average of 16.9 ± 2.1 yr. This yielded a SOC stock change factor of 0.6 Mg C ha-1 yr-1, comparing favourably to a modelling assessment and the Intergovernmental Panel on Climate Change (IPCC) default factor. In six LTAEs in western Canada, no-tillage increased SOC storage by 3.2 ± 1.3 Mg C ha-1 in the top 15 cm over a period of 23.3 ± 2.7 yr relative to conventional tillage, a rate of SOC storage of 0.14 Mg C ha-1 yr-1. This rate was also similar to that derived by simulation modelling and was slightly lower than the default IPCC rate for subhumid and semi-arid regions. In eastern Canada, where tillage is much deeper than western Canada, SOC storage was not significant differently between the two tillage systems. In six LTAEs in western Canada, removing fallow periods every second or third year in favour of continuous cropping increased SOC storage by 5.2 ± 1.1 Mg C ha-1 yr-1 over 21.8 ± 4.0 yr or an average SOC stock change factor of 0.23 Mg C ha-1 yr-1 to 15 cm depth. This was slightly higher than two independent meta-analyses and rates derived from simulation modelling. The results determined from a re-sampling of LTAEs across Canada provided an invaluable method of validating rates of SOC change concluded by other means.

Modelling the effect of land use and climate change on the water balance and nitrate leaching in eastern Denmark

This article examines the effect of land use and climate change on the water balance and nitrate leaching in the eastern part of Denmark. The evaluation and scenario analysis is carried out using the dynamic agroecosystem model ‘Daisy’ set up for a number of representative soil types and land management scenarios providing the basis for an average regional assessment of nitrate leaching. It is found that evapotranspiration will increase while changes in percolation and drainage depend on soil type and land management. Average weighted nitrate leaching rates are increased by 24% if management practices are kept constant, whereas a status quo is expected when management options are changed. However, Daisy is sensitive to inputs in the soil organic N pool and a better understanding of how this pool develops in a climate change situation is required if reliable predictions should be obtained together with an assessment of the effect of land management changes.

Modeling a Small, Northeastern Watershed with Detailed, Field-Level Data

Time, resource, and replication constraints limit the practicality of conducting agricultural experimental studies at scales larger than plot-level. Thus, watershed-level models such as the Soil and Water Assessment Tool (SWAT) are increasingly used to forecast effects of land management changes on downstream water quality. With the generalization in scale, the question of effect of generalization in input data arises. That is, to what extent does having field-level, daily input data for a watershed model aid in the ability to predict watershed-scale, water quality impacts. The study site, FD-36, is a 39.5 ha agricultural subwatershed of a long-term USDA-ARS study watershed in south central Pennsylvania. FD-36 is characterized by loamy soils with a substantial near-stream fragipan. Fifty percent of FD-36 includes 24 row-cropped fields from three independently managed farms. Two SWAT scenarios were simulated on FD-36 and compared with each other as well as with measured data over two 4-year periods (1997-2000 and 2001-2004). The high-resolution scenario modeled seasonal crop, fertilizer, and tillage events of each row-cropped field continuously over the 8-year period. The low-resolution scenario treated all row-cropped fields as the same generic crop (AGRR in SWAT). Flow depth predictions at the outlet were similar for the two SWAT scenarios. While both scenarios showed higher levels of soil water in the fragipan soils than the surrounding soils, the high-resolution scenario was able to identify field-to-field distinctions due to the increased detail in input data. In general, model results were more defined at the field-level under the high-resolution scenario and followed patterns expected from knowledge about soil science, hydrology, P transport, and the characteristics of the study watershed. However, the time spent collecting, understanding, entering, and error-checking input data required for the high-resolution scenario was on the order of months, while full data collection for the low-resolution scenario took several days. Results suggest that while detailed input data can enable the model to provide valuable water quality information, research efficiency during exploratory and initial problem-solving efforts might be maximized by using more easily obtained, although more general, data.

Effects of Land Management Change on Spatial Variability of Organic Matter and Nutrients in Paddy Field: A Case Study of Pinghu, China

The Household Responsibility System initiated in the late 1970s in China has brought a profound change to its rural economy. The shift from the collective farming system to individual family farms has changed land management. The change, including fertilization and crop systems, may have significant effects on soil quality and agro-environmental sustainability. However, very little research is being carried out on the impact of reformed land tenure systems on the spatial variability of soil nutrients. In this study, geostatistics was applied to analyze changes in the spatial variability of soil organic matter and nutrients in paddy fields in Pinghu County, China after 20 years of land management change. In 1984 and 2002, 617 and 131 locations were selected, respectively, for collecting surface soil samples to analyze soil organic matter (SOM), total nitrogen (TN), available phosphorus (AP), and available potassium (AK). From 1984 to 2002, variability of the SOM and TN changed from strongly to moderately spatial-dependent, and the variability of AP remained weakly dependent on space, but that of the AK changed from moderately to weakly spatial-dependent. That the trend of the variability of four soil properties in 2002 became weaker than that in 1984 showed that the extrinsic factors (soil management practices, such as fertilization) weakened the effect by intrinsic factors (soil formation factors, such as soil parent materials) owing to a long period of land management change. The temporal geographic maps of the SOM and nutrients spatial distributions suggested that the concentrations of the SOM and nutrients had been changed to different extents during the period. Significant increase in AP and decrease in AK were noted. The changes were likely due to the imbalance between N, P, and K fertilizers and increased grain yield.

Including trace gas fluxes in estimates of the carbon mitigation potential of UK agricultural land

Abstract. A number of changes in agricultural land‐management show some potential as carbon mitigation options. However, research has focused on CO2‐carbon mitigation and has largely ignored potential effects of land management change on trace gas fluxes. In this paper, we attempt for the first time, to assess the impact of these changes on fluxes of the important agricultural greenhouse gases, methane and nitrous oxide, in the UK.The estimates presented here are based on limited evidence and have a great (unquantifiable) uncertainty associated with them, but they show that the relative importance of trace gas fluxes varies enormously among the scenarlos. In some, such as the application of sewage sludge, woodland regeneration and bioenergy production scenarios, the inclusion of estimates for trace gas fluxes makes only a small (&lt;10%) difference to the CO2‐C mitigation potential. In the animal manure and agricultural extensification scenarios, including estimates of trace gas fluxes has a large impact, increasing the CO2‐C mitigation potential by up to 50%. In the no‐till scenario, the carbon mitigation potential decreases significantly due to a sharp increase in N2O emissions under no‐till.When these land‐management options are combined for the whole agricultural land area of the UK, including trace gases has an impact on estimated mitigation potentials, and depending upon assumptions for the animal manure scenario, the total mitigation potential either decreases by about 10% or increases by about 30%, potentially shifting the mitigation potential of the scenario closer to the EU's 8% Kyoto target for reduction of CO2‐carbon emissions (12.52 Tg C yr−1 for the UK).