Resent research has identified the existence of social networks as a common and important denominator in cases where different stakeholders have come together to effectively deal with natural resource problems and dilemmas. It has even been shown that social networks can be more important than the existence of formal institutions for effective enforcement and compliance with environmental regulations. However, all social networks are not created equal. On the contrary, the structural pattern of relations (i.e. the topology) of a social network can have significant impact on how actors actually behave. This clearly has implications for actors’ abilities to manage environmental challenges. This review aims to add more precision to initial insights and pending hypotheses about the positive impacts of social networks on governance processes and outcomes, by reviewing and synthesizing empirically based literature explicitly studying structural characteristics of social networks in natural resource governance settings. It is shown that significant differences in governance processes and outcomes can be expected among networks experiencing structural differences in terms of density of relations, degree of cohesiveness, subgroup interconnectivity, and degree of network centralization. Furthermore, the review shows that none of these structural characteristics present a monotonically increasing positive effect on processes of importance for resource governance, and that favoring one characteristic likely occurs at the expense of another. Thus, assessing the most favorable level and mix of different network characteristics, where most of the positive governance effects are obtained while undesired effects are minimized, presents a key research and governance challenge.

https://www.stockholmresiliencecenter.org/download/18.5ce3bd8012d79a5929580003005/Bodin+and+Crona+2009_Social+networks+in+NRM+review.pdf

The role of social networks in natural resource governance: What relational patterns make a difference?

Soil Nutrient Bioavailability—A Mechanistic Approach

Summary 1. Agricultural intensification reduces ecological resilience of land-use systems, whereas paradoxically, environmental change and climate extremes require a higher response capacity than ever. Adaptation strategies to environmental change include maintenance of shade trees in tropical agroforestry, but conversion of shaded to unshaded systems is common practice to increase short-term yield. 2. In this paper, we review the short-term and long-term ecological benefits of shade trees in coffee Coffea arabica, C. canephora and cacao Theobroma cacao agroforestry and emphasize the poorly understood, multifunctional role of shade trees for farmers and conservation alike. 3. Both coffee and cacao are tropical understorey plants. Shade trees in agroforestry enhance functional biodiversity, carbon sequestration, soil fertility, drought resistance as well as weed and biological pest control. However, shade is needed for young cacao trees only and is less important in older cacao plantations. This changing response to shade regime with cacao plantation age often results in a transient role for shade and associated biodiversity in agroforestry. 4. Abandonment of old, unshaded cacao in favour of planting young cacao in new, thinned forest sites can be named ‘short-term cacao boom-and-bust cycle’, which counteracts tropical forest conservation. In a ‘long-term cacao boom-and-bust cycle’, cacao boom can be followed by cacao bust due to unmanageable pest and pathogen levels (e.g. in Brazil and Malaysia). Higher pest densities can result from physiological stress in unshaded cacao and from the larger cacao area planted. Risk-averse farmers avoid long-term vulnerability of their agroforestry systems by keeping shade as an insurance against insect pest outbreaks, whereas yield-maximizing farmers reduce shade and aim at short-term monetary benefits. 5. Synthesis and applications. Sustainable agroforestry management needs to conserve or create a diverse layer of multi-purpose shade trees that can be pruned rather than removed when crops mature. Incentives from payment-for-ecosystem services and certification schemes encourage farmers to keep high to medium shade tree cover. Reducing pesticide spraying protects functional

/pdf/multifunctional-shade-tree-management-in-tropical-3a6lhn9waz.pdf

Multifunctional shade‐tree management in tropical agroforestry landscapes – a review

Crop and irrigation management strategies for saline-sodic soils and waters aimed at environmentally sustainable agriculture.

Complex challenges demand complex solutions. By their very nature, these problems are difficult to define and are often the result of rigid social structures that effectively act as “traps”. However, resilience theory and the adaptive cycle can serve as a useful framework for understanding how humans may move beyond these traps and towards the social innovation that is required to address many complex problems. This paper explores the critical question of whether networks help facilitate innovations to bridge the seemingly insurmountable chasms of complex problems to create change across scales, thereby increasing resilience. The argument is made that research has not yet adequately articulated the strategic agency that must be present within the network in order for cross scale interactions to occur. By examining institutional entrepreneurship through case studies and examples, this paper proposes that agency within networks requires specific skills from entrepreneurs, including ones that enable pattern generation, relationship building and brokering, knowledge and resource brokering, and network recharging. Ultimately, this begins to build a more complete understanding of how networks may improve human capacity to respond to complex problems and heighten overall resilience.

https://www.ecologyandsociety.org/vol16/iss1/art5/ES-2010-3812.pdf

Surmountable Chasms: Networks and Social Innovation for Resilient Systems

Access to knowledge on farm management practices is essential for the maintenance of productive agroforestry systems. Farmers who lack the means to acquire farming knowledge from formal sources often rely on information within their informal social networks. However, little research has explored the explicit structure of farmer communication patterns. We examined advice network structures by using farmer attributes, i.e., kin relationships, community involvement, and imitation, to characterize structural positions and investigated the consequences of such structure on farming practices in cocoa agroforestry systems in Ghana, West Africa. Furthermore, we used a multicommunity approach; we constructed networks for four communities to increase replication and enhance the generality of our conclusions. A high density of advice ties occurred among a small group of farmers, indicating a core- periphery structure. Settler farmers composed 73% of core position members, suggesting that social proximity did not control the formation of informal advice structures. Because core farmers were highly participative in community activities, the promotion of community involvement may facilitate the movement of knowledge and social exchange to strengthen informal networks. Farmers in both core and peripheral structural positions indicated that they observed fellow farmers and subsequently adopted their practices. Of highly sought farmers, 84% used external information, predominately from government institutions, thus functioning as bridging links between formal and informal networks. Both external and farmer-derived sources of knowledge of agroforestry practices were transferred through informal advice networks, providing available information throughout the farming community, as well as a foundation for community-based adaptive management.

/pdf/transfer-of-knowledge-on-agroforestry-management-practices-c3pyhtb73q.pdf

Transfer of Knowledge on Agroforestry Management Practices: the Structure of Farmer Advice Networks

Farm product diversification, shade provision and low access to fertilizers often result in the purposeful integration of upper canopy trees in cocoa (Theobroma cacao) plantations. Subsequent modification to light and soil conditions presumably affects nutrient availability and cocoa tree nutrition. However, the level of complementarity between species requires investigation to minimize interspecific competition and improve resource availability. We hypothesized beneficial effects of upper canopy trees on cocoa biomass, light regulation, soil fertility and nutrient uptake. We measured cocoa standing biomass and soil nutrient stocks under no shade (monoculture) and under three structurally and functionally distinct shade trees: Albizia zygia (D.C.) Macbr, a nitrogen fixer; Milicia excelsa (Welw.), a native timber species; and Newbouldia laevis (Seem.), a native small stature species. Vector analysis was employed to diagnosis tree nutrition. Cocoa biomass was higher under shade (22.8 for sole cocoa versus 41.1 Mg ha−1 for cocoa under Milicia), and declined along a spatial gradient from the shade tree (P < 0.05). Percent canopy openness differed between the three shade species (P = 0.0136), although light infiltration was within the optimal range for cocoa production under all three species. Soil exchangeable K was increased under Newbouldia, while available P decreased and total N status was unaffected under all shade treatments. Nutrient uptake by cocoa increased under shade (43–80% and 22–45% for N and P, respectively), with K (96–140%) as the most responsive nutrient in these multistrata systems. Addition of low-density shade trees positively affected cocoa biomass close to the shade tree, however proper management of upper stratum trees is required for optimum cocoa productivity and sustainability.

/pdf/shade-tree-effects-in-an-8-year-old-cocoa-agroforestry-37eu5igsou.pdf

Shade tree effects in an 8-year-old cocoa agroforestry system: biomass and nutrient diagnosis of Theobroma cacao by vector analysis

Fertilization is standard practice in forest tree seedling nursery culture. Additionally, fertilization at outplanting has potential to facilitate nutrient uptake and reduce transplant shock. Fertilization, however, may dramatically alter rhizosphere chemical properties such as pH, ion availability, and electrical conductivity (EC). These changes may inhibit root system growth and function by reducing soil osmotic potential and creating specific ion toxicities. The risk of root damage associated with high EC levels appears to be dependent on species, age of root system, and soil moisture availability. Root inhibition in container nursery culture of conifers is likely to occur above 2.5 dS  m−1, though threshold EC levels for bareroot culture and field plantings are largely unavailable. Fertilization at outplanting has the added risk that drought conditions may prevent leaching of excess fertilizer salts, which can increase rhizosphere EC beyond safe levels and ultimately impair root uptake of water or nutrients. For fertilization programs to be successful, a critical threshold balance must be maintained between optimizing seedling nutrient availability in the rhizosphere, while minimizing potential for root damage. Future research is needed to identify optimal EC levels for a range of species across all stages of the reforestation process, from nursery culture through plantation establishment.

Fertilizer-induced Changes in Rhizosphere Electrical Conductivity: Relation to Forest Tree Seedling Root System Growth and Function

Competition between maize and pigeonpea in semi-arid Tanzania: Effect on yields and nutrition of crops

Frequent nutrient removals accompanying wood and crop harvests from rotational woodlot systems may contribute to declining site productivity and sustainability because of soil nutrient depletion. However, selecting for nutrient-efficient tree species may well sustain productivity under this system. To test this hypothesis, a randomized complete block experiment was adopted to assess effects of five tree species on soil nutrients status, nutrient use efficiency and wood yield in semi-arid Tanzania. After 5 years rotation, top soils under Gliricidia sepium (Jaqua), Acacia polyacantha Willd. and Acacia mangium Willd. were the most fertile with soil organic carbon and exchangeable cation status raised close to those in natural Miombo systems. Soil inorganic N and extractable P levels reached sufficiency levels for subsequent maize culture. Wood productivity in tree fallows averaged three times higher than that of Miombo woodlands indicating the high potential of the woodlot system to supply fuelwood, and consequently relieve harvesting pressures on the natural forests. Acacia crassicarpa A. Cunn. ex Benth. produced the most wood (51 Mg ha−1) at low nutrient “costs” presumably due to high nutrient use efficiency. Wood yield of this species was 42 and 120% greater than that of A. polyacantha and A. nilotica, respectively, but contained comparatively less nutrients (42–60% less for P, K, and Ca). Gliricidia sepium and A. polyacantha returned the largest amount of nutrients through slash at harvests. Of all test species, A. crassicarpa exhibited the most promise to sustain wood production under rotational woodlot systems due to relatively high productivity and low nutrient export at harvest.

V. R. Timmer

Papers

Transfer of Knowledge on Agroforestry Management Practices: the Structure of Farmer Advice Networks

Shade tree effects in an 8-year-old cocoa agroforestry system: biomass and nutrient diagnosis of Theobroma cacao by vector analysis

Fertilizer-induced Changes in Rhizosphere Electrical Conductivity: Relation to Forest Tree Seedling Root System Growth and Function

Competition between maize and pigeonpea in semi-arid Tanzania: Effect on yields and nutrition of crops

Nutrient use efficiency and biomass production of tree species for rotational woodlot systems in semi-arid Morogoro, Tanzania