Differential effect of shade, water and soil type on emergence and early survival of three dominant species of the Atacama Desert

Abstract

Understanding the regeneration niche of species may allow us to gain insight into how communities are structured. In deserts, the regeneration niche is usually related to spaces beneath shrubs where shade cast by shrubs creates microenvironments that benefit seedlings and where even small amounts of rain may favour germination and establishment. Shade and water may also interact with different types of soils. However, species may have different requirements for germination and seedling survival. We could expect that shrub species with different drought tolerances exhibit different responses to the combination of these factors. We ask if responses of dominant species of the Atacama Desert to abiotic factors (shade, water and soil type) are related to their drought tolerance, a topic not exhaustively explored in shrubs growing in true deserts. We conducted two factorial experiments. The first one was designed to evaluate how shade (microhabitat) in combination with water may affect germination (emergence) and early survival. In the second experiment, we assessed the influence of shade in relation to soil type. Each species responded distinctively to the three variables under study, but in general, their emergence responses were more influenced by water (more water, greater emergence) than by microhabitat or soil type. Survival was influenced both by microhabitat and by water and was higher under shade and abundant water. Soil type affected only one of our species in terms of emergence. Species responses in general depended on their tolerance to stress. In one species, there was indication of a seed-seedling conflict. Our results show similar species responses to environmental constraints but also more or less unique responses that are related to their tolerance to drought and which may ultimately permit species coexistence. We found that shade may not be important for germination but may be crucial for survival in dry years.

Shading Gradients Drive Differential Responses of Leaf Traits in an Early Community Germinated by Forest Topsoil

“…The dual response showed that slight shading increased the values of leaf traits and severe shading decreased them to that in full light conditions in a few species. In a given community, plant species usually present specific differences in response to light demand or shading tolerance; these differences may affect the responses of species that co-occurred across the shading gradients [14,15,19]. For seedlings of tropical tree species [7], the largest changes in most species in this study were observed to occur at relatively high light conditions compared to in low light conditions (3-12% daylight).…”

“…Meanwhile, vegetation restoration with diverse tree species requires long-term successions, and seedling survival and growth are critical for successful community establishment in the early stages [17]. Excessive radiation can generate stress in plant individuals and communities; thus, shading is a necessary and effective method of protecting seedlings [6,18,19]. Shade effects are also considered as key determinants of organ functional differentiation, individual performance, and community dynamics [20][21][22][23].…”