Effect of shade and precipitation on germination and seedling establishment of dominant plant species in an Andean arid region, the Bolivian Prepuna.

Natalio Roque Marca,Kazuya Naoki,Ramiro Pablo López

doi:10.1371/journal.pone.0248619

Abstract

Germination and seedling establishment are two critical processes in the life cycle of plants. Seeds and seedlings must pass through a series of abiotic and biotic filters in order to recruit as members of their communities. These processes are part of the regeneration niche of the species. In arid regions, the regeneration niche is frequently associated to facilitation by shade. Facilitation is a positive interaction between plants, in which one of them acts as a benefactor (the nurse) of the other (the beneficiary). The result of this interaction can be reflected in the increased growth, survival, and/or reproduction of the beneficiary plant. In this study, we determined experimentally the effect of shade and irrigation on the germination and early survival of dominant species of a semi-arid Andean region, the Bolivian Prepuna. An experiment with Acacia feddeana, Prosopis ferox, Cercidium andicola (woody species), Parodia maassii, and Oreocereus celsianus (cactus species) was carried out at an experimental garden in La Paz, Bolivia, with a bifactorial design, considering shaded and unshaded pots, subjected to two irrigation treatments (≈50 and 80 mm of rainfall during the whole study period). Microenvironmental conditions did not affect the seed germination of the woody species. However, they showed differences in seedling survival: A. feddeana survived better under shade, whereas P. ferox and C. andicola survived better without shade. Cercidium andicola, compared to P. ferox, was more affected by shade and low irrigation. Although germination success of cacti was low, both species germinated better under shade and with high irrigation. These results showed differences in the regeneration niche of dominant species of the Prepuna which may favor their coexistence and which may be characteristic of other dry Andean regions.

Highlights

Plant regeneration comprises a life cycle from seeds to seedlings and adult plants [1, 2]
O. celsianus and P. maassii, germination reached its highest fraction with high irrigation ( 80 mm) and artificial shade
Neither species germinated in unshaded pots with low irrigation ( 50 mm), and O. celsianus had negligible germination in the other treatment combinations (Fig 2)

Summary

Introduction

Plant regeneration comprises a life cycle from seeds to seedlings and adult plants [1, 2]. Shade is mostly provided by nurse species, which are larger species that modify the microenvironment beneath them, and sometimes by inanimate objects, such as rocks or dead plant material [11,12,13]. This positive effect of nurses is considered one of the main mechanisms that underlies facilitative relationships between plants [14], and is one of the most important plant—plant interactions in habitats with extreme environmental conditions [15, 16]. The facilitating effect of nurse plants appears to be more important during germination and establishment of beneficiary species [10, 17], and the positive effect frequently disappears or becomes competitive in later phases of the beneficiary’s life cycle [18,19,20]

Methods

Results

Conclusion