The land-use dynamics of potato agrobiodiversity in the highlands of central Peru: a case study of spatial-temporal management across farming landscapes

In the high Andes, environmental and socio-economic drivers are transforming land use and presumably affecting the in situ conservation of potato (Solanum spp.). To monitor the use and conservation of intraspecific diversity, systematic and comparative studies across land-use systems are needed. We investigated the spatial-temporal dynamics of potato in two contrasting landscapes of Peru’s central Andes: a highland plateau (Huancavelica) vs. an eastern slope (Pasco). We examined household-level areal allocations, altitudinal distribution, sectoral fallowing practices, and the conservation status for three main cultivar groups: (i) bred varieties, (ii) floury landraces, and (iii) bitter landraces. Mixed methods were used to survey 323 households and the 1,101 potato fields they managed in 2012–2013. We compared the contemporary altitudinal distribution of landraces with 1975–1985 altimeter genebank data from the International Potato Center. We show that intensification occurs in each landscape through adaptations of traditional management practices while maintaining high intraspecific diversity. Access to land and production end use (sale vs. consumption) significantly affected smallholder management and differentiated the landscapes. Total areas in Huancavelica and Pasco were allocated to 82.9% vs. 74.2% floury landraces, 9.2% vs. 25.7% bred varieties, and 7.9% vs. 0.1% bitter landraces. In market-oriented Pasco, fields in sectoral fallows between 3,901 m and 4,116 m above sea level consistently contained the highest levels of landrace diversity. The bulk of diversity in subsistence-oriented Huancavelica occurred between 3,909 m and 4,324 m outside sectoral fallows. Most of the unique landraces documented were scarce across households: 45.4% and 61.7% respectively in Huancavelica and Pasco. Bred varieties showed the widest (1,100 m) and bitter landraces the narrowest (400 m) altitudinal distributions. Potato cultivation has moved upward by an average of 306 m since 1975. Landrace diversity is versatile but unevenly distributed across landscapes. This requires adaptive ways to incentivize in situ conservation.

highlands is driven by context-specific pressures that require smallholders' differential 146 management adjustments while allowing the maintenance of high intraspecific diversity. 147 Implications for the long-term in situ conservation tied to land use are reflected upon.  150 We conducted in-depth research in five communities pertaining to two contrasting highland 151 landscapes of Peru's central Andes (Fig 1; Table 1). The first cluster of three farmer    165 Drawing from cartography and participatory methods we conducted participatory mapping   using the packages glmnet caret and catools [62]. as it involved human subjects in non-invasive survey procedures. We sought and obtained 292 the approval of community authorities prior to survey implementation. We described the 293 objectives of the study, the methodology, the oral prior informed consent option, voluntary 294 nature and confidentiality of households participating during a community assembly.

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Community authorities from the five communities selected agreed to the study. Households 296 were surveyed only after community-level approval.  3.1. Household characteristics 299 We calculated and compared main household features across landscapes (Table 2). These  (Table 3). 60.0%, dual purpose 23.5%, and solely consumption 16.5%. Most field production had a 320 secondary end use. In Huancavelica, farmers saved medium-sized tubers for both seed and 321 making freeze-dried chuño from 90.7% of fields. Seed and chuño production exclusively 322 were secondary uses for 8.1% and 0.4% of fields respectively. Only 0.8% of production from 323 sampled fields had no secondary end use. In Pasco, secondary uses were seed and chuño 324 production (20.0%), tuber seed exclusively (39.4%), chuño production exclusively (28.4%), 325 seed and pig feed (4.8%), pig feed exclusively (1.1%), chuño and pig feed (0.8%). Only 5.5% 326 of production from surveyed fields did not have any secondary end use.

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In both landscapes, households followed two potato cropping calendars, the qatun tarpuy,  360 ‡Calculated from sum of distinct cultivars across the three cultivar groups.

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We contrasted the spatial distribution and relative abundance of cultivars by cultivar group 362 (Fig 2A, 2B) and RCF level (Fig 3A, 3B) for a representative community in each landscape.

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Red listing showed that most cultivars were very scarce (RCF<0.05) across households: 364 45.4% of total cultivars in Huancavelica and 61.7% in Pasco (Table 5). These were  Table 6). Overall, for the landscapes combined, 12.5% of cultivars 370 were in the cropping portfolios of most households while 29.6% were grown by less than 1% 371 of households.    (Table 8).  (Table 9).

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These always tended to be two to three times larger for households in Pasco for fields with 430 bred varieties and floury landraces or a mix of these two cultivar groups.      differentiating features of potato production between landscapes (Fig 7B; S1 Fig D, E, F).

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All fields in Pasco belonged to a fallowing sector. This applied to 23.3% of fields in 563 Huancavelica. Field fallowing rates were also higher in Pasco at this range, 0.85 (±0.06) vs.   (Table 11; Fig 8; Fig 9). Pasco showed the greatest upward shift of 404 m for 576 floury landraces. For bitter landraces, the upward shift has been less pronounced overall.      Across landscapes, cultivar groups were not spatially separated but rather overlapped and to 729 a large extent shared the same space. This finding confirms that rationales other than niche  situation. Yet, it represents only one season and does not account for inter-seasonal variation. 750 We recorded the application of chemicals per field (yes/no) but did not measure the frequency 751 or amounts of fertilizers and fungicides used. We therefore have no way of providing a fine-