Unexpectedly, intense livestock grazing in arid rangelands strengthens the seedling vigor of consumed plants

Abstract

Grazing intensification with non-native livestock is known to degrade vegetation cover, particularly in arid environments where low resource availability strongly limits plant recovery after damage. However, it remains unclear whether the effect of grazing on consumed plants is transmitted to plant offspring. We hypothesized that grazing would reduce fruit weight, germination percentage, and seedling vigor of consumed vegetation. Therefore, we collected mature fruits from six dominant shrub species in seven independent paddocks with increasing livestock densities. Fruits were air-dried and weighed before seed sowing. After seedling emergence, we measured the percentage of germination and seedling vigor, i.e., height and number of leaves. Hierarchical models were used to account for the effects of plant species and year of collection. Results show that, in general, increasing livestock density reduced fruit weight and percentage of germination of consumed plants. However, surprisingly, increasing livestock density enhanced seedling vigor. Overall, increasing livestock density has both negative and positive effects on consumed plants offspring.

Evaluating the fitness effects of seed size and maternal tree size onPolylepis tomentella(Rosaceae) seed germination and seedling performance

“…Differences in mean seed size at the intra-specific level have been associated with a diversity of adaptations to a broad range of ecological niches and conditions (Quero et al 2007, Tripathi & Khan 1990. Although some studies have shown a direct link between seed size and seedling performance (Leger et al 2019), other studies have found to be environmentally dependent or associated with habitat degradation (Ma et al 2019, Renison et al 2004, Seltmann et al 2007a, Tadey & Souto 2016. In semiarid environments, plants are limited by xeric conditions which impose severe constraints to seedling recruitment.…”

Transgenerational effects of ungulates and pre-dispersal seed predators on offspring success and resistance to herbivory

“…Ungulates affected seed viability by decreasing seed mass in some arid and semiarid shrubs [23,25]. In our system, ungulates affected seed quality by reducing the content of carbon in the seeds, but there was no effect in seed mass or nitrogen content.…”

“…These impacts entail a significant decrease in the number of seeds produced by damaged plants. Additionally, mammalian herbivores may diminish the quality of the seeds produced by the attacked plants, greatly lessening their germination, emergence and establishment [22–25]. Seed quality is related to the resource investment into the seeds by the maternal plant, and for many species it is critical for germination and seedling survival [6,7,10,26,27].…”

Livestock Effects on Genetic Variation of Creosote Bushes in Patagonian Rangelands

“…In arid and semi-arid environments, however, several studies have shown negative impacts of livestock on plant density, species richness and cover of native vegetation (Perelman et al 1997, Buttolph & Coppock 2004, Cingolani et al 2005, Zhao et al 2005, Tadey 2006, Tadey & Souto 2016). It has also been well documented that livestock affect sexual reproduction in plants by decreasing floral abundance and/or seed production (Whitham et al 1991, Paige 1992, Strauss et al 1996, Strauss & Armbruster 1997, Tadey 2007).…”