Evaluating the contribution of tree-based land uses to carbon stocks and biodiversity in an Andean agricultural landscape

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Anna M. Visscher, Camilla Wellstein, Gianmaria Bonari and Stefan Zerbe, Faculty of Science and Technology, Free University of Bozen-Bolzano, Bolzano, Italy, Steven Vanek and Steven J. Fonte, Soil and Crop Sciences, Colorado State University, Fort Collins, CO, Katherin Meza, Raul Ccanto, Edgar Olivera and Maria Scurrah, Grupo Yanapai, Huancayo, Peru

Background/Question/Methods:
The Central Andes harbours a complex mosaic of land uses (e.g., production fields, pasture, forest, fallows). These land uses have been shown to differ in the provision of ecosystem services (ES), with tree-based land uses (e.g., hedgerows, forests) being especially important for ES such as C sequestration and biodiversity conservation. Evaluating the contribution of trees to ES at the landscape scale is critical for long-term planning and payment for ES schemes, but the effect of land uses with trees can extend beyond their immediate borders. A recent study from the Andes indicated that tree-based land uses can impact the provision of ES and macro fauna diversity into adjacent croplands, suggesting a need to incorporate this effect of trees into landscape level assessments of ES (Visscher et al., 2020). In this study we examined the contribution of woody land uses to C stocks (above- and below-ground) and macrofauna and ground cover diversity (Shannon Index) at the landscape level in a representative agricultural landscape of the Central Peruvian Andes. We estimated the effect of trees by evaluating a landscape scenario where trees were replaced with pasture, based on ES data and land-use maps generated from previous studies in the community of Quilcas (Huancayo, Junin). Beyond changes in land use, we also examined the potential influence of tree-based land uses on soil C (at 20 cm depth) and biodiversity in adjacent croplands and pastures.
Results/Conclusions
Given that C stocks were overall higher in tree-based land uses compared to non-forest land uses, the inclusion of trees in this landscape is estimated to increase the total C stock by 153 %. Tree-based land uses occupied 26.1 % of the studied landscape. Macrofauna diversity differed among the different land uses, being highest in land uses with alder trees (Alnus acuminata), such that the inclusion of trees to the landscape was associated with a 25 % increase in macrofauna diversity, but a slight negative effect on the diversity of ground cover (-6 %). When accounting for the influence of tree-based land uses on adjacent lands, the overall soil C stock of the landscape increased by 1.4 %, while macrofauna diversity increased by approximately 5 %. Our findings suggest that the addition of trees can enhance overall C stocks and soil macrofauna diversity in agroecosystems of the Peruvian highlands and that it is important to take into consideration spatial interactions between land uses with and without trees.