Abstract
BackgroundIn the Peruvian Coastal Desert, an archipelago of fog oases, locally called lomas, are centers of biodiversity and of past human activity. Fog interception by a tree canopy, dominated by the legume tree tara (Caesalpinia spinosa), enables the occurrence in the Atiquipa lomas (southern Peru) of an environmental island with a diverse flora and high productivity. Although this forest provides essential services to the local population, it has suffered 90% anthropogenic reduction in area. Restoration efforts are now getting under way, including discussion as to the most appropriate reference ecosystem to use.Methodology/Principal FindingsGenetic diversity of tara was studied in the Atiquipa population and over a wide geographical and ecological range. Neither exclusive plastid haplotypes to loma formations nor clear geographical structuring of the genetic diversity was found. Photosynthetic performance and growth of seedlings naturally recruited in remnant patches of loma forest were compared with those of seedlings recruited or planted in the adjacent deforested area. Despite the greater water and nitrogen availability under tree canopy, growth of forest seedlings did not differ from that of those recruited into the deforested area, and was lower than that of planted seedlings. Tara seedlings exhibited tight stomatal control of photosynthesis, and a structural photoprotection by leaflet closure. These drought-avoiding mechanisms did not optimize seedling performance under the conditions produced by forest interception of fog moisture.Conclusions/SignificanceBoth weak geographic partitioning of genetic variation and lack of physiological specialization of seedlings to the forest water regime strongly suggest that tara was introduced to lomas by humans. Therefore, the most diverse fragment of lomas is the result of landscape management and resource use by pre-Columbian cultures. We argue that an appropriate reference ecosystem for ecological restoration of lomas should include sustainable agroforestry practices that emulate the outcomes of ancient uses.
Highlights
The Guidelines and Primer of the Society for Ecological Restoration call upon practitioners of ecological restoration to rediscover the past to determine what needs to be restored at a given site [1]
An analysis of molecular variance (AMOVA) for the Peruvian populations showed that 93% of total genetic diversity occurred within populations (W = 0.232, df = 170, P,0?001), while only 7% was attributable to variation among populations (W = 0.019, df = 8, P,0.001)
Our results strongly suggest that the presence and dominance of tara (Caesalpinia spinosa) in the Atiquipa fog oasis is attributable to past human activity
Summary
The Guidelines and Primer of the Society for Ecological Restoration call upon practitioners of ecological restoration to rediscover the past to determine what needs to be restored at a given site [1]. The best known oases are those created by and dependent on local availability of ground or runoff water Much rarer are those where the main source of water is the deposition of fog droplets. In the Peruvian Coastal Desert, an archipelago of fog oases, locally called lomas, are centers of biodiversity and of past human activity. Fog interception by a tree canopy, dominated by the legume tree tara (Caesalpinia spinosa), enables the occurrence in the Atiquipa lomas (southern Peru) of an environmental island with a diverse flora and high productivity. This forest provides essential services to the local population, it has suffered 90% anthropogenic reduction in area. Restoration efforts are getting under way, including discussion as to the most appropriate reference ecosystem to use
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