ENVIRONMENTAL FACTORS THAT AFFECT REGENERATION IN THE FORESTS OF THE DRY CHACO - MONTE ECOTONE

FIGUEROA AGOSTINA; MERCADO AGUSTIN; ILLANES JUAN; CAMPOS VALERIA

San Juan

Jornada; XLI Reunión Científica Anual de la Sociedad de Biología de Cuyo; 2023

Spatial environmental heterogeneity in relation to factors leads to non-random plant distribution in landscapes. In arid ecosystems, precipitation, due to its scarcity, is the most limiting environmental factor for plant communities. This factor and topography affect thermal, hydrological and edaphic conditions influencing the structure, function and dynamics of communities. The objective of theenvironmental work was to evaluate the relationship between factors and the abundance of sapling individuals of tree species in native forests of the Dry Chaco-Monte ecotone (San Juan). For this, 34 plots of 17.8 m radius (1000 m2) were sampled, where individuals with a diameter at the height of the base less than 7.5 cm and a minimum height of 1.5 m were counted as sapling. The environmental factors considered were: actual evapotranspiration (aet), climatic water deficit (def), Palmer drought severity index (pdsi), precipitation accumulation (pr), runoff (ro), descending surface shortwave radiation (srad), minimum temperature (tmin), maximum temperature (tmax). These variables corresponded to the summer of 2018-2019 (TerraClimate, Abatzoglou et al., 2018). The data were fitted to a negative binomial distribution because they presented overdispersion (assessed in the residuals). The abundance of the sapling varied between 0 and 83. The minimum and maximum of the variables were the following: aet 35.67 - 63.05 mm; def 121.5 - 146.4 mm; pdsi-0.7 - 0.35; pr 37.5 - 66.5 mm; ro 1.75 - 3.25mm; srad 252.85 - 289.4 W/m2; tmin 11.22 - 18.9 °C; tmax 25.75 - 32.4°C; twi -4536.06 - 6816.98. The minimal adequate model included the following variables: pdsi (-1.129±0.318); pr (0.121±0.054); and ro (-3.809±1.228). The abundance of sapling was negatively affected by pdsi and ro, while precipitation showed a positive relationship with the abundance of saplings. The pdsi uses temperature and precipitation data to estimate the severity of drought, the negative relationship between pdsi and the abundance of saplings would be showing a lower tolerance of sapling to drought. On the other hand, greater runoff (ro) from the ecosystem implies a greater amount of water that drains through the river network, leaving little water available for plants, which negatively affects the abundance of sapling. Finally, the abundance of precipitation would be favoring the establishment of sapling tree species in this Dry Chaco-Monte ecotone. The regeneration of native forests is an important aspect to evaluate to know the dynamics, structure and functioning of these ecosystems. Saplings are more vulnerable to environmental factors, because they aren’t mature in their root systems and structures, which makes them less resistant. Understanding this relationship between environmental factors and forest regeneration allows us to propose better proposals for the management and conservation of forests.