Appendix A. Individual Conceptual Networks Representing Agricultural Management and Ecosystem

1Appendix A. Individual conceptual networks representing agricultural 2management and ecosystem services provision.34 The relationships between agricultural management and eight ecosystem 5services (ES) provided by Pampean agroecosystems were represented in individual 6conceptual networks (Figs. 1 to 8). The eight conceptual networks developed in this 7work contained five types of nodes, and four types of logical links between nodes (see 8Section 2.3.). These logical links present capital letters in order to easily explain each 9conceptual network. 10111. Supporting Service: Elements cycling - C Balance1213Fig. 1 Conceptual network representing functional relationships between agricultural management and 14provision of the Supporting service: Elements cycling - C balance. Capital letters represent the logical 15links between nodes. Legend: circles meaning input variables; rounded-squares meaning decision 16variables; squares meaning state variables; triangles meaning ecosystem processes and diamond meaning 17ecosystem service provision indicators. Tº: temperature, and Pp: rainfall 181 1 19 It is generally known that C inputs in soils consist of crop residues and roots, 20and sometimes additions of soil organic amendments; while C loss is caused by humus 21and residue mineralization, in conditions where soil erosion and C leaching are minimal 22(C leaching is not an important cause of soil organic carbon (SOC) losses in Pampean 23agroecosystems (Roberto Álvarez, personal communication)) (Oorts and others 2006). 24The interaction between temperature and rainfall regulates SOC through the influence 25of soil organic matter (SOM) mineralization (Fig. 1, Relations A and B) (Roberto 26Álvarez and Raúl Lavado, personal communication). High temperature reduces SOC 27because of intense SOM mineralization, while there is no linear answer for rainfall (Fig.281, Relations A, B and F) (Álvarez and Lavado 1998). However, it is widely accepted 29that, in general, rainfall has the same effect as temperature (Fig. 1, Relations B and F) 30(Roberto Álvarez and Raúl Lavado, personal communication). Additionally, crop 31species, their growth rate and yield determine the amount and type (i.e., quality) of crop 32residue (including crop roots) (Fig. 1, Relations D and I) (Ernst and others 2002) which 33change SOC in surface soil layers, specially in no-tillage systems (Álvarez and Lavado 341998). Surface soil layers have greater C amounts because of the input of crop residue 35from harvested plants (Álvarez and Lavado 1998). Generally, legume species (e.g., 36soybean) have higher mineralization rates than gramineous species (e.g., wheat, maize) 37due to lower C/N relations (Fig. 1, Relation E) (Ernst and others 2002). 38 Another conditioning factor of SOC reduction is erosion vulnerability which is 39higher in continuous cropping systems, principally by 1) removing C from one site and 40depositing it elsewhere, and 2) promoting soil degradation and then reducing 41productivity (Fig. 1, Relation G) (Martínez-Mena and others 2008). However, it can be 42assumed that SOC movement is dependent on the topographic position (Haydée 43Steinbach and Roberto Álvarez, personal communication). Soils under no-tillage reduce2 2 44both eolic erosion in semiarid sites, and hydric erosion in sites with great slopes 45(Monzon and others 2006).46472. Supporting Service: Elements cycling - N Balance4849Fig. 2 Conceptual network representing functional relationships between agricultural management and 50provision of the Supporting service: Elements cycling - N balance. Capital letters represent the logical 51links between nodes. Legend: circles meaning input variables; rounded-squares meaning decision 52variables; squares meaning state variables; triangles meaning ecosystem processes and diamond meaning 53ecosystem service provision indicator. Tº: temperature, and Pp: rainfall 54 55 Soil nitrogen (N) availability is modulated by four main factors: SOM 56mineralization, crop residue, fertilization regime and N losses (Cassman and others 572002). N mineralization through SOM is a very important supply source due to its usage58availability (Fig. 2, Relation G), increasing or decreasing crop yield (Fig. 2, Relation J) 59(Bono and Álvarez 2007). The increase in soil moisture content increases mineralized N60(Fig. 2, Relations B and F) (Helena Rimski-Korsakov, personal communication). This 61increase is a direct consequence of higher microbial activity, until the concentration of 3 3 62oxygen in the soil becomes a limitation for the microorganisms (Navarro and others 631991). Moreover, SOM is not only affected by mineralization but also by crop residue 64disposal on soil surface layers (Fig. 2, Relation E) (Ernst and others 2002), as it occurs 65for SOC in no- and reduced tillage systems. N fertilization can increase the amount of 66soil N pools which will be available for crops (Fig. 2, Relation K) (Abril and others 672007). However, N excedent can also be immobilized by microorganisms, resulting in a68non linear effect (i.e., increase or reduce) of the application (Fig. 2, Relation K) 69(Cassman and others 2002; Portela and others 2006). Furthermore, N losses by 70denitrification, volatilization or leaching are the main causes for the low efficiency in 71the use of N, and therefore they affect available N in soil (Fig. 2, Relation L) (Abril and 72others 2007). Because of the low degree of these losses during the whole crop growth 73cycle (Álvarez and Grigera 2005), they can be grouped all together under the name of N74losses (Roberto Álvarez, personal communication). 75763. Supporting Service: Water cycling - Soil water balance7778Fig. 3 Conceptual network representing functional relationships between agricultural management and 79provision of the Supporting service: Water cycling - Soil water balance. Capital letters represent the 80logical links between nodes. Legend: circles meaning input variables; rounded-squares meaning decision 81variables; squares meaning state variables; triangles meaning ecosystem processes and diamonds meaning82ecosystem service provision indicators. Tº: temperature, and Pp: rainfall 4 4 83 84 In Pampean agroecosystems, water supply for crops is determined by nine 85variables: 1) evaporation, 2) runoff, 3) soil structural stability, 4) soil texture, 5) aquifer 86depth, 6) soil depth, 7) presence of weeds/fallow/cover crops, 8) irrigation, and 9) 87rainfall (Fig. 3, Relations M, N, O, P, Q, R, S, T and C). These variables, in general, 88increase or affect water supply for crops. For instance, no-tillage systems leave crop 89residue on the soil surface and, therefore, soil evaporation is clearly decreased (Fig. 3, 90Relations E and F) (Monzon and others 2006). Relative soil evaporation rates directly 91influence the amount of soil water retained which will be used by the crop (Fig. 3, 92Relation M) (O´Leary and Connor 1997). Stubble mulch protects the surface soil from 93erosion and runoff, and increases water storage by minimising surface sealing and 94enhancing infiltration, as well as by directly reducing evaporation (Fig. 3, Relations G, 95J, N and O) (O´Leary and Connor 1997). Moreover, irrigation not only increases water 96supply for crops (Fig. 3, Relation T) but also affects runoff, depending on the amount of97water irrigated and crop residue on soil surface (Fig. 3, Relation L) (Olga Heredia, 98personal communication). Systems under no-tillage can increase soil water 99accumulation during fallows (Fig. 3, Relation S), and thereby offer the potential for 100affecting crop yield in Pampean agroecosystems (Olga Heredia and Francisco Bedmar, 101personal communication) (Fig. 3, Relation U). 102 Soil depth is related with the ability of roots to explore soil profile and to absorb 103water stored there (Fig. 3, Relation R); on the other hand, aquifer depth can be defined 104by characterizing the average depth fluctuation of water table in different regions (Fig. 1053, Relation Q) (Esteban Jobbágy, personal communication). This is specially important 106in sandy soils (Claudia Sainato, personal communication). Finally, weeds can be burned107to avoid evaporation as well as the establishment of cover crops (Fig. 3, Relation S) 108(Olga Heredia and Silvina Portela, personal communication). 5 5 1091104. Supporting service: Soil conservation – Soil structural maintenance111112Fig. 4 Conceptual network representing functional relationships between agricultural management and 113provision of the Supporting service: Soil conservation – Soil structural maintenance. Capital letters 114represent the logical links between nodes. Legend: circles meaning input variables; rounded-squares 115meaning decision variables; squares meaning state variables; triangles meaning ecosystem processes and 116diamonds meaning ecosystem service provision indicators. Tº: temperature, and Pp: rainfall 117 118 Structural stability is defined as soil capacity to preserve the system of solids and119pore space, when subjected to different external disturbances (e.g., tillage) (Taboada 120and Micucci 2002). Its loss is the critical factor which determines structural 121deterioration. This deterioration is evidenced by the formation of surface crusts, higher 122rates of runoff and soil loss due to erosion, as well as reduced water storage (Taboada 123and Micucci 2002). Soil structural stability is clearly affected by land use, which is in 124turn positively associated with crop residue, total organic C concentration and the forms125of organic C (Fig. 4, Relations I and J) (Caravaca and others 2004). The close 126association found between structural stability, labile carbon and microbial biomass 6 6 127confirms both their importance in the mineralization process and their ability as 128aggregate cementitious (Fig. 4, Relations G and H) (Urricarriet and Lavado 1999). 129According to the first statement, SOM decomposition may be limited by pore size 130distribution due to the localization of SOM in pores inaccesible to microorganisms, a 131limited nutrient supply to microorganisms and restricted predation of those 132microorganisms (Miguel Taboada and Roberto Casas, personal communication). 133Furthermore, soil structural stability is one of the most important characteristics 134affecting crop yield (Fig. 4, Relation K) because it affects root penetration, water 135storage capacity, and air and water movement in soil (Fig. 4, Relation O) (Aparicio and 136Costa 2007). 1371385. Regulating Service: Climate regulation – N2O emission control 139140Fig. 5 Conceptual network representing functional relationships between agricultural management and 141provision of the Regulating service: Climate regulation – N2O emission control. Capital letters represent 142the logical links between nodes. Legend: circles meaning input variables; rounded-squares meaning 143decision variables; squares meaning state variables; triangles meaning ecosystem processes and diamonds144meaning ecosystem service provision indicators. Tº: temperature, and Pp: rainfall 1457 7 146 Although denitrification is only part of direct N2O emissions from soils, it is the 147most studied process in contrast with nitrification occurring in unsaturated soils, among 148other conditions (Fig. 5, Relation P) (Laura Yahdjian, personal communication). Thus, 149the main factors controlling denitrification are: soil pH, soil texture, nitrate 150concentration, C availability, aeration and moisture content (Guo and Zhou 2007). 151However, the major factors to consider, in terms of N2O production in Pampean 152agroecosystems, are available N in soil and moisture content (in this case, rainfall) (Fig. 1535, Relations N and O) (Palma and others 1997; Ciampitti and others 2005). For instance,154it is known that the presence of actively growing plants limits the denitrification process155in comparison with those treatments without plants, due to reduced water availability 156and to lower levels of nitrates in soil, to a lesser extent (Sainz Rozas and others 2004). 157Once the crop is harvested and crop residue remains on the surface, soluble C 158concentration is associated with denitrification (Fig. 5, Relation E); this is because 159bacteria biomass capable of denitrification is probably controlled primarily by C 160availability under aerobic conditions (Fig. 5, Relation M) (Miguel Taboada, personal 161communication), while emissions occur mainly during anaerobic conditions (Fig. 5, 162Relation O).1631646. Regulating Service: Water purification - Groundwater contamination control 1658 8 166Fig. 6 Conceptual network representing functional relationships between agricultural management and 167provision of the Regulating service: Water purification - Groundwater contamination control. Capital 168letters represent the logical links between nodes. Legend: circles meaning input variables; rounded-169squares meaning decision variables; squares meaning state variables; triangles meaning ecosystem 170processes and diamonds meaning ecosystem service provision indicators. Tº: temperature, and Pp: rainfall171172 Nitrate (NO3) leaching is one of the main causes for groundwater contamination 173(Fig. 6, Relations N and O) (Abril and others 2007; Claudia Sainato and Olga Heredia, 174personal communication). However, Mugni and others (2005) measured NO3 175concentration in four Pampasic streams and concluded that it was relatively modest 176compared to intensively cultivated basins in Europe and North America. Consequently, 177there is a slow N enrichment of water resources in Pampean agroecosystems (Portela 178and others 2006). Water quality is reduced not only by N fertilization (Fig. 6, Relation 179J) (Rimski-Korsakov and others 2004; Abril and others 2007), but also SOM 180mineralization through several years removes great amounts of NO3 towards aquifers 181(Portela and others 2006; Helena Rimski-Korsakov and Raúl Lavado, personal 182communication) (Fig. 6, Relation G). N fertilization could also be indirectly inducing 183soil NO3 leaching, by altering the ability of plants root system to acquire N from soil 184and net mineralization rate from organic N pools (Cassman and others 2002). 185Furthermore, fertilization in excess of crop requirements or water excedent, such as 186rainfall events (Fig. 6, Relation M) or irrigation (Fig. 6, Relation K), increase the 187probability of soil NO3 leaching (Costa and others 2002; Rimski-Korsakov and others 1882004; Vergé and others 2007). It is important to clarify that the Pampa region has low N189inputs through rainfall (Portela and others 2006). Other factors affecting soil NO3 190leaching are particle size distribution, soil porosity and the ocurrence of preferential 191flow paths. These causes can be grouped under soil texture, which is another important 9 9 192factor because of its ability for retaining water (Fig. 6, Relation L) (Taboada and 193Micucci 2002). 1941957. Regulating Service: Regulation of biotic adversities196197Fig. 7 Conceptual network representing functional relationships between agricultural management and 198provision of the Regulating service: Regulation of biotic adversities. Capital letters represent the logical 199links between nodes. Legend: circles meaning input variables; rounded-squares meaning decision 200variables; squares meaning state variables; triangles meaning ecosystem processes and diamonds meaning201ecosystem service provision indicators 202203 In Pampean agroecosystems, crop environment is determined by: 1) tillage 204system, 2) crop protection, 3) sowing density, 4) sowing date, 5) fertilization, 6) 205genotype selection, and 7) irrigation (Fig. 7, Relations B, A, C, D, E, F and G). These 206variables affect not only crop yield but also species composition and abundance of plant207and animal community, and beneficial species (Fig. 7, Relations H, J and L) (Emilio 208Satorre and Elba De la Fuente, personal communication). Beneficial species as well as 209crop environment and crop changes affect species composition and 210abundance/incidence of pests, diseases and weeds (Fig. 7, Relations K, L and N). The 211latter reduces crop yield and affects natural pest mitigation of ecosystems (Fig. 7, 10 10 212Relations I and O). The presence of weeds influences the presence of diseases and 213diversity and abundance of two insect types: pests, with negative consequences for 214cropping systems, and their natural enemies (Altieri 1999). Generally, a high density of 215weeds is counter-productive because they reduce crop yield and its quality (Albrecht 2162003). 2172188. Biodiversity maintenance219220Fig. 8 Conceptual network representing functional relationships between agricultural management and 221Biodiversity maintenance. Capital letters represent the logical links between nodes. Legend: circles 222meaning input variables; rounded-squares meaning decision variables; squares meaning state variables; 223triangles meaning ecosystem processes and diamond meaning ecosystem service provision indicator 224225 Biological diversity or biodiversity is defined as the wide variety of plants, 226animals, microorganisms and their genetic variations (Altieri 1999). In agroecosystems, 227the variety of crops are also considered as biodiversity components (María Elena 228Zaccagnini, personal communication). However, the type and abundance of biodiversity229may differ across agroecosystems in relation to their crop protection (i.e., 11 11 230phytotherapics application) and tillage system (Fig. 8, Relations A, B and C) (María 231Elena Zaccagnini, personal communication). 232 Other management strategies for increasing biodiversity involve the 1) 233manipulation of undisturbed areas within agroecosystems, 2) preservation of weeds, or 2343) introduction of mixtures containing grasses, legumes, flowering and/or aromatic 235plants. These strategies offer alternative food sources (i.e., pollen, nectar) to different 236organisms, and places for hibernation and reproduction (Fig. 8, Relation D) (Carmona 237and Landis 1999; Carmona and others 1999; Landis and others 2000). Furthermore, 238areas functioning as shelters act as biological corridors in the mobility of natural 239enemies (decreasing, in some cases, phytotherapic application) and their non-240fragmentation is fundamental to the establishment of these organisms and the rapid 241recolonization of agroecosystems after a disturbance (Fig. 8, Relation D) (Carmona and 242Landis 1999; Landis and others 2000; Jonsson and others 2008; Gardiner and others 2432009; Rufus and others 2009). 244 Sequences, rotations and landscape structure provide two types of 245agroecosystems heterogeneity (Fig. 8, Relations E and F). On the one hand, 246sequences/rotations are recognized as temporal heterogeneity even though they are 247planned biodiversity (e.g., crops, pastures); on the other hand, landscape structure can 248be identified as spatial heterogeneity (Elba De la Fuente, personal communication). 249Landscape structure plays a crucial role in the survival of species by offering different 250kinds of habitat (Claudio Ghersa, personal communication). 251252References12 12 253Abril A, Baleani D, Casado-Murillo N, Noe L (2007) Effect of wheat crop fertilization254 on nitrogen dynamics and balance in the Humid Pampas, Argentina. Agriculture,255 Ecosystems & Environment 119:171-176. 256Albrecht H (2003) Suitability of arable weeds as indicator organisms to evaluate species257 conservation effects of management in agricultural ecosystems. Agriculture,258 Ecosystems & Environment 98:201-211.259Altieri MA (1999) The ecological role of biodiversity in agroecosystems. 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Appendix A. Individual Conceptual Networks Representing Agricultural Management and Ecosystem

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