Evidence on the response of Patagonian forage grasses to the mulching effect of recent tephra deposits in Argentina

Abstract

In Patagonia, arid and semiarid lands are being affected both by inappropriate management practices, which are leading to degradation, and by volcanic activity, whose effects are still unclear. This study aimed to test whether superficial deposition of volcanic tephra could benefit two of the most prominent Patagonian forage grass species (Poa ligularis and Pappostipa speciosa var. speciosa). Pots with P. ligularis and P. speciosa were kept under wet (W) and dry (D) conditions in the presence (Tþ) or absence (TÀ ) of tephra for 105 days, and then were all well-watered. We determined the effects of tephra on soil water retention and conservation, soil moisture content (% v/v), plant growth, stomatal conductance (gs), and gs recovery capacity. The water regime significantly affected both species performance and gs. The presence of tephra increased soil water conservation, soil moisture content in wet conditions, and P. ligularis gs in wet conditions, and decreased senescence in dry conditions (9% in P. ligularis and 16% in P. speciosa). The presence of tephra allowed roots to grow in 8/10 and 2/10 pots in W conditions for P. ligularis and P. speciosa, respectively, and in only 1/10 pots in D conditions, only for P. ligularis. Tephra was also associated with gs recovery after dry conditions. Poa ligularis was more positively affected by tephra than P. speciosa, probably because P. ligularis has higher phenotypic plasticity. The positive effects of tephra may increase the resilience and resistance of P. speciosa and P. ligularis to periods of water shortage.

Aeolian Remobilisation of the 2011-Cordón Caulle Tephra-Fallout Deposit: Example of an Important Process in the Life Cycle of Volcanic Ash

“…Ash accumulations in plants are the most commonly observed remobilisation deposit, with accumulation effectiveness depending on the species, quality, age and density of vegetation cover (Kok et al, 2012). In the studied area, two main species of plants are identified (Edwards et al, 2017): grassy or herbaceous steppe (e.g., Poa ligularis, Pappostipa speciosa) of 0.2-0.5 m height (Figure 5A) and shrub steppe (e.g., Prosopis denudans) of 1-2 m height (Figure 5B). Additionally, large interpatch areas (bare soil between plants), showing strong erosion surfaces, are common (Figure 5C).…”