Microenvironmental Heterogeneity Driven by Trees in Arid Woodlands: Effects of Neltuma flexuosa Canopy in the Monte Desert

ABSTRACT

Woody plants modify environmental conditions, increase heterogeneity, and affect the spatial distribution of other species. These changes can include differences between under‐canopy and exposed areas, microheterogeneity under the canopy, and temporal variability. Data on the mechanisms underlying microenvironmental heterogeneity in drylands remain scarce, yet understanding these mechanisms is crucial for planning conservation, management, and restoration programs. In the Monte Desert (Argentina), Neltuma flexuosa alters the spatial distribution of shrubs and herbs, as well as soil properties. In this work, we analyzed the changes in light, soil, and water conditions produced by N. flexuosa at two different scales in the Ñacuñán Reserve (Mendoza, Argentina). We randomly selected 12 trees, installed a set of pluviometers and evaporimeters, and measured soil water content, temperature, and photosynthetically active radiation (PAR) intensity once per month in two mesohabitats (under the canopy and exposed areas) and two microhabitats (under the northern or southern canopy of N. flexuosa ). Our results showed that N. flexuosa plays a significant role in generating diverse microhabitats. At the mesohabitat scale, it intercepted rainfall and reduced evaporation, thereby lowering the water deficit. In addition, it moderated extreme temperatures and reduced solar radiation. This effect was stronger in the southern microhabitat than in the northern one, and in the summer season. These modifications were heterogeneous and promoted microheterogeneity beneath their canopy, resulting in distinct microenvironments. This heterogeneity aligns with species distribution patterns found in previous studies. The varying requirements of species for these factors likely determine each species' capacity to occupy different microhabitats.