The impact of contracts on organic honey producers' incomes in southwestern Ethiopia
Girma, J. ; Gardebroek, C. - \ 2015
Forest Policy and Economics 50 (2015). - ISSN 1389-9341 - p. 259 - 268.
propensity score - countries - schemes - program - africa - bias
In southwestern Ethiopia honey is a non-timber forest product that provides income for many smallholders. Some of these beekeepers supply their honey under contract to a company that markets their organic honey internationally allowing them to access premium markets. Since both production and marketing depend crucially on the forest, both smallholders and the company have an interest in preserving the forest. An important question is whether smallholders also benefit economically from supplying under contract. The objective of this study is to examine the contribution of participation in contract supply of organic honey to beekeepers' income levels in the Sheka zone in southwestern Ethiopia. Results indicate that contract supply improved quality of honey delivered, the prices beekeepers received, and total honey income per household. The findings illustrate the potential of contract supply of forest product for sustainable management of forests.
Sticks and carrots for the design of international climate agreements with renegotiations
Weikard, H.P. ; Dellink, R.B. - \ 2014
Annals of Operations Research 220 (2014). - ISSN 0254-5330 - p. 49 - 68.
klimaatverandering - internationale verdragen - milieubeleid - climatic change - international agreements - environmental policy - environmental agreements - stability - cooperation - schemes
This paper examines renegotiations of international climate agreements for carbon abatement. We explore coalition stability under ‘optimal transfers’ that have been suggested to stabilise international environmental agreements (e.g. McGinty in Oxford Economic Papers 59, 45–62, 2007). Such transfer schemes need to be refined when agreements are renegotiated. We determine the requirements that transfers between signatories of an international climate agreement must satisfy in order to stabilise the sequence of agreements that performs best in terms of provision of the public good ‘carbon abatement’. If these requirements are met, no country wants to change its membership status at any stage. In order to demonstrate the applicability of our result we use the STACO model, a 12-regions global model, to assess the impact of well-designed transfer rules on the stability of an international climate agreement. Although there are strong free-rider incentives, we find a stable grand coalition in the first commitment period in a game with one round of renegotiations if renegotations take place sufficiently early.
Optimizing the design of small-sized nucleus breeding programs for dairy cattle with minimal performance recording
Kariuki, C.M. ; Komen, J. ; Kahi, A.K. ; Arendonk, J.A.M. van - \ 2014
Journal of Dairy Science 97 (2014)12. - ISSN 0022-0302 - p. 7963 - 7974.
genome-wide selection - overlapping generations - predefined rate - prediction - schemes - kenya - improvement - efficiency
Dairy cattle breeding programs in developing countries are constrained by minimal and erratic pedigree and performance recording on cows on commercial farms. Small-sized nucleus breeding programs offer a viable alternative. Deterministic simulations using selection index theory were performed to determine the optimum design for small-sized nucleus schemes for dairy cattle. The nucleus was made up of 197 bulls and 243 cows distributed in 8 non-overlapping age classes. Each year 10 sires and 100 dams were selected to produce the next generation of male and female selection candidates. Conception rates and sex ratio were fixed at 0.90 and 0.50, respectively, translating to 45 male and 45 female candidates joining the nucleus per year. Commercial recorded dams provided information for genetic evaluation of selection candidates (bulls) in the nucleus. Five strategies were defined: nucleus records only [within-nucleus dam performance (DP)], progeny records in addition to nucleus records [progeny testing (PT)], genomic information only [genomic selection (GS)], dam performance records in addition to genomic information (GS+DP), and progeny records in addition to genomic information (GS+PT). Alternative PT, GS, GS+DP, and GS+PT schemes differed in the number of progeny per sire and size of reference population. The maximum number of progeny records per sire was 30, and the maximum size of the reference population was 5,000. Results show that GS schemes had higher responses and lower accuracies compared with other strategies, with the higher response being due to shorter generation intervals. Compared with similar sized progeny-testing schemes, genomic-selection schemes would have lower accuracies but these are offset by higher responses per year, which might provide additional incentive for farmers to participate in recording.
Rethinking commons management in Sub-Saharan West Africa: public authority and participation in the agricultural water sector
Venot, J.P.J.N. - \ 2014
Water International 39 (2014)4. - ISSN 0250-8060 - p. 534 - 548.
upper east region - ghana - productivity - institutions - property - panaceas - schemes
Promoted for over three decades, participatory irrigation management (PIM) and its organizational upshot the water user association (WUA) have been framed as a solution to the irrigation sector problems. Based on a case study of small reservoirs in two countries of West Africa, Burkina Faso and Ghana, this article shows that the PIM/WUA model is based on narrow visions of the commons and participation and does not account for the de facto pluralism and institutional bricolage that characterize natural resources management. Attempts at institutional intervention should be based on better understanding social relationships and existing processes of decision making.
Comparing two sensitivity analysis approaches for two scenarios with a spatially explicit rural agent-based model
Schouten, M.A.H. ; Verwaart, T. ; Heijman, W.J.M. - \ 2014
Environmental Modelling & Software 54 (2014)April. - ISSN 1364-8152 - p. 196 - 210.
land-use - environmental-models - agricultural policies - simulation - biodiversity - schemes - uncertainty - landscapes - management - protocol
In this paper two sensitivity analysis approaches are applied for scenario analysis in a spatially explicit rural agent-based simulation. The simulation aims to assess the socioeconomic and ecological impacts of agricultural policy interventions, market dynamics and environmental change on a regional scale. Two different methods of sensitivity analysis are investigated: i) a one-at-a-time approach where each parameter is varied one after the other, while all other parameters are kept at their nominal values; and ii) a procedure based on Monte Carlo sampling where random sets of input parameter values are related to outputs of the simulation. The complementarity of both approaches and their contribution to the overall interpretation of the model is shown in two scenarios simulating alternative European policy instruments for biodiversity conservation. Results show that a mixed approach of sensitivity analysis leads to a better understanding of the model’s behaviour, and further enhances the description of the simulation’s response to changes in inputs and parameter settings.
Pirates or pioneers? unplanned irrigation around small reservoirs in Burkina Faso
Fraiture, C.M.S. de; Kouali, G.N. ; Sally, H. ; Kabre, P. - \ 2014
Agricultural Water Management 131 (2014). - ISSN 0378-3774 - p. 212 - 220.
upper east region - resources - ghana - productivity - institutions - management - schemes - systems
Small reservoirs in Burkina Faso are constructed for many purposes such as domestic water uses, livestock watering and irrigated rice production downstream of the dam. Increasingly farmers use individually owned motorized pumps to draw water directly from the reservoir and irrigate vegetables upstream of the dam. This practice, while tolerated, is unauthorized and referred to as ‘irrigation pirate’ in French. Upstream vegetable cultivation is successful because it is more profitable than downstream rice cultivation. Often, the ‘unofficial’ irrigated area around the reservoir is much larger than the official command area below the dam. However, in the absence of an overarching authority to manage the water source, this may lead to conflicts and resource degradation. We take the example of the Korsimoro reservoir in Burkina Faso to illustrate the positive and negative impacts of spontaneous individual irrigation around communally managed water bodies
Seasonal dependence of the urban heat island on the street canyon aspect ratio
Theeuwes, N.E. ; Steeneveld, G.J. ; Ronda, R.J. ; Heusinkveld, B.G. ; Hove, L.W.A. van; Holtslag, A.A.M. - \ 2014
Quarterly Journal of the Royal Meteorological Society 140 (2014)684. - ISSN 0035-9009 - p. 2197 - 2210.
warmte - steden - stedelijke planning - warmtebalans - seizoenvariatie - meteorologie - nederland - heat - towns - urban planning - heat balance - seasonal variation - meteorology - netherlands - boundary-layer - energy-balance - climate zones - model - temperature - parameterization - simulation - schemes - cabauw - field
In this paper we study the relation between the urban heat island (UHI) in the urban canyon and street geometry, in particular the aspect ratio. Model results and observations show that two counteracting processes govern the relation between the nocturnal UHI and the building aspect ratio: i.e. trapping of longwave radiation and shadowing effects. In general, trapping of longwave radiation supports the UHI, whereas shadowing effects reduce the UHI. The net effect depends on the UHI definition and the amount of available shortwave radiation penetrating the canyon. In summer, autumn and spring the shadowing effects can already reduce the UHI starting at an aspect ratio between 0.5 and 1. The analysis is carried out using several methods. Firstly, the single-column model version of the Weather Research and Forecasting model (WRF) is used extensively. Two separate runs, one rural and one urban, are used to estimate the UHI. Secondly, the urban canyon temperature at the two meter level is introduced, which allows for direct comparison between modelled and observed air temperatures within the urban canyon. Finally, the model is evaluated for all four seasons. The results of this research provide important insights for urban planning on how to use the aspect ratio to mitigate the UHI in the urban canyon
Investigation of Lattice Boltzmann wetting boundary conditions for capillaries with irregular polygonal cross-section
Sman, R.G.M. van der - \ 2013
Computer Physics Communications 184 (2013)12. - ISSN 0010-4655 - p. 2751 - 2760.
binary fluids - porous-media - simulations - flows - model - equation - configurations - dynamics - schemes
We have investigated the performance of an alternative wetting boundary condition for complex geometries in a phase field Lattice Boltzmann scheme, which is an alternative to the commonly used formulation by Yeomans and coworkers. Though our boundary condition is much simpler in its implementation, all investigated schemes show proper droplet spreading behaviour following the Cox-Voinov law. Still, numerical artefacts like spurious velocities or chequer board effects in the pressure field can be significantly reduced by the use of a two-relaxation-time (TRT) scheme, likewise recent studies by the Yeomans group. The outstanding property of our implementation is the presence of an (artificial) thin wetting layer, which influences the relation between the saturation (S-w) and capillary pressure p(cap) in channels with irregular polygonal cross section. The p(cap) (S-w) relation from our simulation follows the shifted-Young-Laplace (sYL) law, showing that the physics of this wetting layer is similar to precursor films due to Van der Waals forces. With the knowledge of the thickness of the wetting layer, simulation results can be translated back to realistic pore configurations with thinner wetting layers. (C) 2013 Elsevier B.V. All rights reserved.
Participation of Italian farmers in rural development policy
Pascucci, S. ; Magistris, T. de; Dries, L.K.E. - \ 2013
European Review of Agricultural Economics 40 (2013)4. - ISSN 0165-1587 - p. 605 - 631.
agri-environmental contracts - transaction costs - european-union - design - conservation - perspective - information - services - schemes - choice
The aim of this paper is to study farmers' participation in rural development policy (RDP) measures. We investigate to what extent regional RDP priorities are driven by regional characteristics and moreover, whether regional-level policy priorities help to explain farmers' participation in RDP measures. We estimate a multilevel binary choice model that includes both farm-level and regional-level explanatory variables. We conclude that regional governments select RDP priorities based on the specific features of their region. Regional policy priorities play an important role in explaining farmers' participation in agri-environmental schemes but not in measures aimed at improving farmer competitiveness.
Simulated selection responses for breeding programs including resistance and resilience to parasites in Creole goats
Gunia, M. ; Phocas, F. ; Gourdine, J.L. ; Bijma, P. ; Mandonnet, N. - \ 2013
Journal of Animal Science 91 (2013)2. - ISSN 0021-8812 - p. 572 - 581.
meat quality traits - nematode infections - genetic-parameters - production systems - gastrointestinal helminths - small ruminants - dairy sheep - merino ewes - schemes - contamination
The Creole goat is a local breed used for meat production in Guadeloupe (French West Indies). As in other tropical countries, improvement of parasite resistance is needed. In this study, we compared predicted selection responses for alternative breeding programs with or without parasites resistance and resilience traits. The overall breeding goal included traits for production, reproduction and parasite resilience and resistance to ensure a balanced selection outcome. The production traits were body weight (BW) and dressing percentage (DP). The reproduction trait was fertility (FER), which was the number of doe kiddings per mating. The resistance trait was worm fecal egg count (FEC), which is a measurement of the number of gastro-intestinal parasite eggs found in the feces. The resilience trait was the packed cell volume (PCV), which is a measurement of the volume of red blood cells in the blood. DP, BW and FEC were measured at 11 mo of age, which is the mating or selling age. FER and PCV were measured on females at each kidding period. The breeding program accounting for the overall breeding goal and a selection index including all traits gave annual selection responses of 800 g for BW, 3.75% for FER, 0.08% for DP, -0.005 ln(eggs/g) for FEC, and 0.28% for PCV. The expected selection responses for BW and DP in this breeding program were reduced by 2% and 6%, respectively, compared to a breeding program not accounting for FEC and PCV. The overall breeding program, proposed for the Creole breed, offers the best breeding strategy in terms of expected selection responses, making it possible to improve all traits together. It offers a good balance between production and adaptation traits and may present some interest for the selection of other goat breeds in the tropics.
Environmental factors driving the effectiveness of European agri-environmental measures in mitigating pollinator loss – a meta-analysis
Scheper, J.A. ; Holzschuh, A. ; Kuussaari, M. ; Potts, S.G. ; Rundlöf, M. ; Smith, H. ; Kleijn, D. - \ 2013
Ecology Letters 16 (2013)7. - ISSN 1461-023X - p. 912 - 920.
agricultural landscapes - farmland biodiversity - species richness - conservation - communities - management - bees - intensity - countries - schemes
In Europe, agri-environmental schemes (AES) have been introduced in response to concerns about farmland biodiversity declines. Yet, as AES have delivered variable results, a better understanding of what determines their success or failure is urgently needed. Focusing on pollinating insects, we quantitatively reviewed how environmental factors affect the effectiveness of AES. Our results suggest that the ecological contrast in floral resources created by schemes drives the response of pollinators to AES but that this response is moderated by landscape context and farmland type, with more positive responses in croplands (vs. grasslands) located in simple (vs. cleared or complex) landscapes. These findings inform us how to promote pollinators and associated pollination services in species-poor landscapes. They do not, however, present viable strategies to mitigate loss of threatened or endangered species. This indicates that the objectives and design of AES should distinguish more clearly between biodiversity conservation and delivery of ecosystem services. Keywords: Agri-environmental schemes, ecological contrast, ecosystem services, landscape context, land-use intensity, pollinators.
Predicted accuracy of and response to genomic selection for new traits in dairy cattle
Calus, M.P.L. ; Haas, Y. de; Pszczola, M.J. ; Veerkamp, R.F. - \ 2013
Animal 7 (2013)2. - ISSN 1751-7311 - p. 183 - 191.
genetic-relationship information - breeding programs - holstein cattle - energy-balance - strategies - emissions - progress - schemes - designs - impact
Genomic selection relaxes the requirement of traditional selection tools to have phenotypic measurements on close relatives of all selection candidates. This opens up possibilities to select for traits that are difficult or expensive to measure. The objectives of this paper were to predict accuracy of and response to genomic selection for a new trait, considering that only a cow reference population of moderate size was available for the new trait, and that selection simultaneously targeted an index and this new trait. Accuracy for and response to selection were deterministically evaluated for three different breeding goals. Single trait selection for the new trait based only on a limited cow reference population of up to 10 000 cows, showed that maximum genetic responses of 0.20 and 0.28 genetic standard deviation (s.d.) per year can be achieved for traits with a heritability of 0.05 and 0.30, respectively. Adding information from the index based on a reference population of 5000 bulls, and assuming a genetic correlation of 0.5, increased genetic response for both heritability levels by up to 0.14 genetic s.d. per year. The scenario with simultaneous selection for the new trait and the index, yielded a substantially lower response for the new trait, especially when the genetic correlation with the index was negative. Despite the lower response for the index, whenever the new trait had considerable economic value, including the cow reference population considerably improved the genetic response for the new trait. For scenarios with a zero or negative genetic correlation with the index and equal economic value for the index and the new trait, a reference population of 2000 cows increased genetic response for the new trait with at least 0.10 and 0.20 genetic s.d. per year, for heritability levels of 0.05 and 0.30, respectively. We conclude that for new traits with a very small or positive genetic correlation with the index, and a high positive economic value, considerable genetic response can already be achieved based on a cow reference population with only 2000 records, even when the reliability of individual genomic breeding values is much lower than currently accepted in dairy cattle breeding programs. New traits may generally have a negative genetic correlation with the index and a small positive economic value. For such new traits, cow reference populations of at least 10 000 cows may be required to achieve acceptable levels of genetic response for the new trait and for the whole breeding goal.
Farmers’ adoption of extensive wheat production – Determinants and implications
Finger, R. ; Benni, N. El - \ 2013
Land Use Policy 30 (2013)1. - ISSN 0264-8377 - p. 206 - 213.
risk attitudes - participation - conservation - schemes
Using farm-level panel data, we analyze farmers’ adoption decisions with respect to extensive wheat production, which is supported in Switzerland since 1992 with an ecological direct payment scheme. It shows that in particular farms with a small area under wheat, low levels of input use and low wheat yields adopted extensive wheat production in the first phase of the programme. If later adoption phases are included in a duration analysis, the difference in wheat area between adopters and non-adopters vanish. However, the level of wheat yields and input use still tend to be lower for adopters. Hence, less intensive producing farms (with lower yield levels) are much more likely to adopt extensive wheat production, which indicates free-riding effects. In contrast, more intensively producing farms, i.e. those farms that may actually harm the environment, usually not adopt extensive wheat production. Thus, aggregated environmental effects of this programme may not reach its full potential and the effectiveness of voluntary participation in agri-environmental programmes should be re-considered. Moreover, we find that changes in wheat prices and the ecological direct payment significantly influenced adoption decisions
Interactive effects of landscape context constrain the effectiveness of local agri-environmental management
Concepción, E.D. ; Díaz, M. ; Kleijn, D. ; Báldi, A. ; Batáry, P. ; Clough, Y. ; Gabriel, D. ; Herzog, F. ; Holzschuh, A. ; Knop, E. ; Marshall, J.P. ; Tscharntke, T. ; Verhulst, J. - \ 2012
Journal of Applied Ecology 49 (2012)5. - ISSN 0021-8901 - p. 695 - 705.
different spatial scales - farmland biodiversity - agricultural landscapes - species-diversity - field margins - schemes - corridors - europe - matrix - birds
summary 1. Ecological theory predicts that the effectiveness of local agri-environmental management to enhance species richness at field scales will be the highest at intermediate levels of landscape complexity because of nonlinear effects of landscape context on field-scale diversity. 2. We examined how landscape complexity determined effectiveness of local agri-environmental management in terms of effects on species richness of birds, plants, spiders and bees in 232 extensive and intensive paired fields (112 arable fields and 120 grasslands) from 18 regions located in six European countries. 3. As predicted, landscape complexity enhanced field-scale species richness in a mostly nonlinear (sigmoidal) way, with earlier species richness increases in extensive than in intensive fields along landscape complexity gradients. Length of semi-natural boundaries (for arable fields) and proportion of unfarmed habitat (for grasslands) were the landscape features influencing species richness. 4. The relationships between effectiveness of local management and landscape complexity for all taxa were best described with hump-shaped curves, indicating the highest effectiveness at intermediate landscape complexities. 5. Synthesis and applications. We used models to investigate how and why effects of local management intensity on species richness vary along wide gradients of landscape complexity. We conclude that landscape-scale management options should take priority over local extensification measures within agri-environmental programmes. These programmes should follow a hierarchical multi-scale approach directed to address landscape-scale constraints on local diversity.
Can altruism stabilise international climate agreements?
Pol, T.D. van der; Weikard, H.P. ; Ierland, E.C. van - \ 2012
Ecological Economics 81 (2012). - ISSN 0921-8009 - p. 112 - 120.
environmental agreements - contingent valuation - social identity - public-goods - cooperation - preferences - fairness - coalitions - consumer - schemes
We study the impact of altruism on the stability of international climate agreements. We consider the standard two-stage game for the analysis of international environmental agreements where countries announce their participation at the first stage and abatement levels are chosen at the second stage. We modify the game to consider altruism in the participation decision, i.e. countries consider, to a certain extent, the net benefits for other countries in their decisions. We study two types of altruism: impartial altruism, where countries show a concern for all other countries, and community altruism, where the concern extends only to coalition partners. We use the stability of coalitions model (STACO) to illustrate the impacts of both types of altruism on the stability of a climate agreement. We find that a limited degree of altruism is sufficient to stabilise the Grand Coalition such that a globally efficient climate policy can emerge while in the absence of altruism only a fraction of countries would join a climate agreement and the benefits of cooperation would largely remain unexploited. Our results indicate how moving beyond national interests can support the success of international climate agreements
Simulation of efficiency impact of drainage water reuse: case of small-scale vegetable growers in North West Province, South Africa
Speelman, S. ; Haese, M.F.C. D'; Haese, L. D' - \ 2011
Agrekon 50 (2011)1. - ISSN 0303-1853 - p. 89 - 101.
data envelopment analysis - productive efficiency - technical efficiency - irrigation - benchmarking - victoria - schemes - farms - spain - dea
This paper focuses on estimating the effect of drainage water reuse on the technical efficiency of small-scale vegetable growers in South Africa applying a data envelopment analysis (DEA). In the semi-arid North West Province of South Africa water scarcity and the soon to be implemented water charges have urged farmers in small-scale irrigation schemes to evaluate the efficiency of their water use. Data on 60 farmers were used to estimate the level of technical efficiency and the effect that drainage water re-use could have on efficiency levels. This effect of water reuse was simulated by a 5, 10, 15 and 20 per cent reduction in water use at farm level. A Malmquist productivity index was calculated to evaluate the effect of these reductions. The main finding was that under current farming conditions many farmers operated at suboptimal levels of technical efficiency. While a reduction in water use evidently increased factor productivity for most farms, the effect clearly varied strongly between farms. This confirms the need to take a systems approach for this type of evaluations.
Variability in smallholders' irrigation water values: study in North-West Province, South Africa
Speelman, S. ; Frija, A. ; Perret, S. ; Haese, M.F.C. D'; Farolfi, S. ; Haese, L. D' - \ 2011
Irrigation and Drainage 60 (2011)1. - ISSN 1531-0353 - p. 11 - 19.
productivity - agriculture - farmers - schemes
Capturing the economic value of water use is an integral part in the design of economic incentives and institutional arrangements that can ensure sustainable, efficient and equitable allocation of water. Irrigation water values of small-scale irrigators are, however, seldom studied and too little attention is paid to the determinants of the variability of water values. In South Africa issues like the call for more efficient water allocation resulting from growing water scarcity, the approaching introduction of water charges for smallholders and the crucial role in rural development attributed to small-scale schemes, render this knowledge even more important. This study therefore first assesses irrigation water values at small-scale irrigation schemes in South Africa using the residual imputation method. Results reveal that, without input subsidies, smallholders have difficulties generating a profit from certain irrigated crops. This raises doubts about the capacity of smallholders to pay for water. The average economic value of irrigation water in this study is US$0.188¿m-3. The water values are, however, shown to be highly variable. The General Linear Model shows that this variability can be mainly attributed to the crop choice and to the irrigation scheme design and institutional setting.
Policy options in a worst case climate change world
Swart, R.J. ; Marinova, N.A. - \ 2010
Mitigation and Adaptation Strategies for Global Change 15 (2010)6. - ISSN 1381-2386 - p. 531 - 549.
albedo enhancement - carbon-dioxide - schemes - capture - system - energy - cycle - air - co2
Climatic changes more rapid and extreme than assessed by the IPCC cannot be excluded, because of the possibility of positive earth system feedbacks and thresholds. Do today's policy makers have to take these into account, and if so, are the options different from those considered today? The paper briefly summarizes the types of extreme climatic changes noted in the literature and then evaluates the options to address them in a what-if manner. Different from other studies, which usually look at only one type of measure, we consider a broader portfolio of options: drastic emissions reduction programmes, drawing greenhouse gases from the atmosphere ("carbon dioxide removal"), "emergency cooling" through influencing the radiative balance of the atmosphere ("solar radiation management"), and finally adaptation beyond the options considered seriously today. Politics will have to decide on the choice or mix of "emergency" measures, but research can ensure that such decisions are based on the best scientific information. If through concerted international efforts to mitigate greenhouse emissions low stabilization levels could be reached, such decisions may never have to be made. However, research in support of some form of a "plan B" is now warranted, focusing on those options that have the most positive ratio between potential effectiveness and feasibility on the one hand, and environmental and political risks on the other hand. Such plan should not be limited to one set of options such as geo-engineering and should explicitly take into account not only the relationships between the options but also the wide variety in characteristics of the individual options in terms of effectiveness, feasibility, environmental risks, and political implications.
Sensitivity of LISEM predicted catchment discharge to initial soil moisture content of soil profile
Sheikh, V. ; Loon, E. van; Hessel, R. ; Jetten, V.G. - \ 2010
Journal of Hydrology 393 (2010)3-4. - ISSN 0022-1694 - p. 174 - 185.
spatial variability - sequential assimilation - surface evaporation - runoff generation - model - parameters - simulation - schemes - scale - uncertainty
This study conducts a broad sensitivity analysis, taking into account the influence of initial soil moisture content in two soil layers, layer depths, event properties, and two infiltration models. A distributed hydrology and soil erosion model (LISEM) is used. Using the terrain data from the Catsop research catchment and two different rainfall events, the sensitivity of discharge is investigated for a range of pre-event soil moisture contents (0.1-0.40 cm(3) cm(-3)) in two-layers for a two-layer Green-Ampt as well as Richards infiltration model. The sensitivity of the predicted discharge to the initial condition of soil moisture appears to depend highly on all factors: infiltration model, event properties, topsoil/subsoil depth configuration and the level of the initial condition itself. There are interaction effects between all the factors. However, the effect of the different infiltration models is most pronounced. The Green-Ampt model shows less sensitivity to moisture content variation of both top and subsoil. Top/subsoil depth configuration rarely influences the results of the Green-Ampt model. The Richards model shows a highly variable discharge - initial soil moisture relation with changing rainfall intensity and topsoil/subsoil depth configurations. Two methods of sensitivity analysis, relative sensitivity and One factor-At-a Time sensitivity, have been used. The two methods gave comparable results. Depending on the other parameter values, 1% changes in topsoil moisture content resulted into 0.8-1.81% and 0.03-3.5% changes in total discharge predicted by the Green-Ampt and Richards models, respectively.
Sampling design optimization for multivariate soil mapping
Vasat, R. ; Heuvelink, G.B.M. ; Borúvka, L. - \ 2010
Geoderma 155 (2010)3-4. - ISSN 0016-7061 - p. 147 - 153.
constrained optimization - regionalized variables - local estimation - schemes
Much attention has been paid to sampling design optimization over the past decades. Many methods have been developed and applied, but only a few of these deal with simultaneous optimization of the sampling design for multiple soil variables. In this paper we present a method implemented as R-code that minimizes the average kriging variance (AKV) for multiple soil variables simultaneously. The method is illustrated with real soil data from an experimental field in central Czech Republic. The goal of the method is to minimize the sample size while keeping the AKV values of all tested soil variables below given thresholds. We defined and tested two different objective functions, critical AKV optimization and weighted sum of AKV optimization, both based on the AKV minimization with annealing algorithm. The crucial moment for such an optimization is defining the mutual spatial relationship between all soil variables with the Linear Model of Coregionalization and proper modelling of all (cross)variograms which are used in the optimization process. In addition, a separate optimization was made for each of the tested soil characteristics to evaluate a possible gain of the simultaneous approach. The results showed that the final design for multivariate sampling is “fully-optimal” for one soil variable — optimal number of observations and optimal structure of sampling pattern, and “sub-optimal” for the others, while no clear difference between the two optimization criteria was found. We can recommend using the method in situations where periodical soil surveys are planned and where multivariate soil characteristics are determined from the same soil samples at once.