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National Parks in Mexico are home to small communities. Whereas productive activities are by definition prohibited within park limits, restoration and conservation practices are encouraged. One way to benefit the inhabitants of these parks is to promote conservation practices that can be productive at the same time. This paper describes and evaluates the practice of regular pruning of Abies religiosa (HBK) in the Cofre de Perote National Park as both a measure to prevent forest fires and a means to obtain the raw material for the manufacturing of Christmas wreaths. Under the guidance of our university research team, over a period of 3 years, local women pruned trees over a total area of 36 ha and used part of the pruning waste (2.71 %) to make the wreaths. The income generated from pruning and from sale of the wreaths contributes significantly to household expenses. We describe the collaboration between the local Women’s Group, the academic team, a federal government agency and the local authorities. The study concludes that the laws regulating national parks in Mexico should specifically stress the importance of allowing productive activities compatible with conservation.

Photosynthesis is the process by which plants absorb atmospheric carbon (C) as they grow and convert it to biomass. However, plants acquire nitrogen (N) and phosphorus (P) only when these are available in the soil solution, which makes these elements the most limiting nutrients to plant growth and productivity in most terrestrial ecosystems. This chapter discusses the C, N, and P reservoirs in soil and plant biomass of two sites (Churince and Pozas Azules) in desert grassland dominated by Sporobolus airoides at the Cuatro Cienegas Valley. We also analyzed the influence of different factors such as soil nutrients, water availability, and microbial nutrient transformations that determine the resource allocation to different pools in this oligotrophic ecosystem. We observed higher aboveground and belowground biomass in Churince than in Pozas Azules. Additionally, we observed higher C and P contents in roots, higher soil total organic C and organic P at Churince, and higher N concentration in the aboveground grass biomass at Pozas Azules. Nutrient contents showed different patterns between sites. Total carbon, N, and P contents were all higher in Churince than Pozas Azules. At the ecosystem level, organic C and organic P were higher in Churince, but no differences were observed in N. In the two soil types studied, C:N:P stoichiometric ratios were different, suggesting that the same dominant plant species makes different adjustments of nutrient concentrations depending on water and nutrient availability, a response that can affect ecosystem nutrient pools as well as various ecosystem processes.

Summary 1. Biological nitrogen (N) fixation by symbiotic and free-living organisms is considered the main pathway for N soil enrichment in desert and semi-desert ecosystems. This fact is more noticeable in tropical ecosystems where legume species have a high relative abundance. However, this biological fixation pathway does not guarantee the maintenance of soil N pools, and N conservation pathways are important in understanding controls over soil N cycling. 2. In dryland ecosystems, desert plants can form a ‘fertility island’ (FI) as soils beneath plants show higher concentrations of N and organic matter. 3. Here we assess how carbon (C) and N may interact to conserve soil N within the FI soil of two legume species (Prosopis laevigata and Parkinsonia praecox), one a known N-fixer and the other believed not to fix N, as well as within adjacent bare ground soil. In a semi-arid tropical ecosystem in central Mexico, we examined spatial patterns in C and N pools and transformation rates, and we investigated seasonal variations in these relationships. 4. Results show that FI soil C and N could be linked to total N storage through net C and N immobilization in microbial biomass and heterotrophic microbial activity. Soil under P. laevigata canopy had greater total N as well as N accumulated in microbial biomass than soil under P. praecox and bare ground soil. Nevertheless, inorganic N and potential net N mineralization rates were similar under soils of both species, although we expected higher inorganic N and N-mineralization values in N-fixer species to explain the greater total N. Higher total N concentrations under P. laevigata probably result from greater inputs of organic C and a higher potential net C mineralization rate in comparison to P. praecox and bare ground soil. 5. Even though N input and output values were not measured, the results highlight the importance of assessing the role of organic C, heterotrophic microbial activity, and N storage in microbial biomass in order to understand controls over N retention in soil N cycling. Thus, soil C-N interactions could be a control factor of N soil conservation in this tropical semi-arid ecosystem.