Seeds project

Until a few years ago, information on the abundance and composition of soil seed banks in South American deserts and semideserts was scarce. Certain preconceptions on the role of granivory ("insignificant") and the magnitude of soil seed reserves ("much lower than in other deserts of the world") prevailed. Results from recent studies in Argentina and Chile show that, on average, seed reserves in South America are not quantitatively different from the ones in other similar areas in other continents. Furthermore, there is an abundant and diverse guild of granivorous animals (birds, ants and small mammals) in many South American localities. However, much more remains to be learnt about the dynamics of the seeds in all deserts, especially about the factors that affect their production and that cause their disappearance once they are dispersed.

Within the framework of our research program, which is focused on the study of the composition and structure of the plants-seeds-consumers system, this project is aimed at analyzing the factors that affect seed input and losses in desert ecosystems. The main idea that leads our research is that climate (mainly rainfall) is the main factor that affects seed production and that granivorous animals are important direct and indirect agents that regulate seed loss in the central Monte desert. The main research lines are:

phenology and seed production in plants (mainly grasses)
The objective is to quantify seed production and temporal and spatial patterns of primary and secondary dispersal.

seedling establishment and changes in plant abundance
The objective is to measure variations in abundance and cover of plants of the herbaceous stratum (especially grasses) and to describe temporal and spatial patterns of seedling emergence and survival.

composition and size of soil seed banks and their spatial and temporal dynamics
The objective is to determine variations in the composition and abundance of seeds in the soil among years, seasons, environments and microhabitats and to establish their probable association with climatic factors (e.g., droughts) and biological factors (e.g., germination events, pathogen attack or predation).

patterns and mechanisms of germination in several herbaceous species
The objective is to study dormancy patterns of seeds so as to establish how this mechanism determines whether soil banks of different plant species are persistent or transient.

mechanisms affecting seed persistence in the soil
The objective is the integration of the knowledge developed in the previous points to analyze the role granivorous animals play as postdipersal seed predators. For that purpose, we study the effects of consumers on seeds (i.e., top-down effects) together with other potential sources of seed loss (e.g., germination, deep burial, weathering, fungal and bacterial attack).