Germination characteristics of five coexisting neotropical species of Acacia in seasonally dry Chaco forests in Argentina

Abstract

At a regional scale, habitat heterogeneity can play a very important role in allowing the coexistence of species through their specialization in the use of patches differing in environmental conditions. Here, we explore responses of seed germination to environmental and anthropogenic factors of five Acacia species that co‐occur in subtropical dry Chaco forests in central Argentina and the habitat heterogeneity of this region. Open and closed sites were characterized in terms of environmental factors by measuring temperature, water content, light quality and soil conditions. Through germination experiments, we evaluated seed responses to both environmental (temperature, light quality and water stress) and anthropogenic factors (fire and cattle). Data were analyzed through a univariate analysis (generalized linear model, GLM) followed by a multivariate analysis (principal component analysis, PCA) in order to obtain a general pattern of Acacia seed responses. Some differences were detected among the Acacia species at the species level and the multivariate analysis (PCA) showed a general pattern with two groups of species differing in germination characteristics: A. aroma, A. caven and A. atramentaria had a higher number of hard seeds after fire and seed consumption by cattle, whereas A. praecox and A. gilliesii showed a reduced time to germinate under different environmental conditions. The multivariate analysis suggests a regenerative niche differentiation between two groups of Acacia species. The habitat heterogeneity described in the dry Chaco forests from central Argentina could facilitate the coexistence of the five Acacia species at the landscape and regional levels.

Different strategies for breaking physical seed dormancy in field conditions in two fruit morphs of Vachellia caven (Fabaceae)

“…the highest percentage of emerged seedlings of the indehiscent morph and almost all the emerged seedlings of the dehiscent morph, when precipitation start to decrease until spring. However, a previous study observed that this species has a high germination at 20/10°C (Venier et al ., 2017) and a high survival of seedlings under water stress (Venier et al ., 2013), suggesting that seeds could survive with low water availability in the environment and remain in the seedling stage until the rainy season. This may be a strategy to ensure their establishment, capitalizing on the resources mobilized by the first rains of spring, when much of the annual vegetation has still not established, i.e.…”

“…; Seigler and Ebinger, 2005) is a tree native to Argentina. The species has PY (Funes and Venier, 2006) and previous studies have shown that neither high temperatures that simulate a fire nor cattle ingestion may break seed dormancy in this species (Venier et al ., 2017; Venier et al ., 2012a). Previous work in some Fabaceae species reported a seasonal pattern in dormancy loss, suggesting that fluctuating temperatures may be a key factor to break dormancy and trigger germination (Van Assche et al ., 2003).…”

Fire damage on seeds ofCalliandra parvifloraBenth. (Fabaceae), a facultative seeder in aBrazilianflooding savanna

“…The seeds were disinfected in 2% NaOCl for 1 min and soaked in distilled H 2 O for 12 h, considering the role of water (rainfall) to alleviate the germination of Fabaceae seeds (Dauro et al, 1997). We distributed the seeds in glass dishes (each dish = 12 seeds) containing sandy substrate to resemble the natural substrate, and because this was successfully used in other studies concerning germination of Mimosoide species, including Calliandra (Calil et al, 2007; Ekasari, 2017; Venier et al, 2017). We performed four repetitions ( n = 12 seeds) for each treatment: burnt and unburnt fruit seeds, sampling procedure similar to that used in Dello Jacovo et al (2019).…”

“…Fire-adapted plant populations persist due to individuals' resprout capacity (sprouting species), abundant seed production, and soil seed bank formation, and their germination can increase when post-fire-mediated dormant seeds break (Daibes et al, 2019;Keeley & Zedler, 1978;Ooi, Denham, Santana, & Auld, 2014;Pausas & Keeley, 2014). Sprouting and non-sprouting Fabaceae species show different post-fire regeneration strategies, but in the Cerrado open savannas resprouting is the most common strategy (Daibes et al, 2019;Santana et al, 2010;Schutte, Vlok, & Van Wyk, 1995;Venier, Cabido, & Funes, 2017;Zupo, Daibes, Pausas, & Fidelis, 2021). In spite of this, fire effects on seed germination in Fabaceae are not related to the regeneration form of the species (Herranz, Ferrandis, & Martínez-S anchez, 1998).…”

“…In spite of this, fire effects on seed germination in Fabaceae are not related to the regeneration form of the species (Herranz, Ferrandis, & Martínez-S anchez, 1998). In addition, optimal heat requirements for seed germination vary among coexisting species, such as in minimizing interspecific competition in secondary succession initiated after the fire (Carter, Lesh, & Mogush, 2000;Herranz et al, 1998;Tarrega, Calvo, & Trabaud, 1992;Venier et al, 2017).…”