Early growth, biomass allocation, and nutrient stoichiometry of Pinus pseudostrobus seedlings grown in commercial and locally available substrate mixtures

Abstract

Seedling quality is a key determinant of reforestation success, yet the use of peat moss ( Sphagnum sp.) as the dominant substrate component imposes economic and logistical barriers for community nurseries in developing countries. We evaluated the early growth, biomass allocation, and nutrient stoichiometry of Pinus pseudostrobus Lindl. seedlings grown for 60 days in four substrate mixtures combining commercial (agrolite, vermiculite, peat moss) and locally available materials (topure -a surface Andosol horizon-, pine bark, and oak forest soil). A completely randomized design with 20 seedlings per treatment was used. Germination (75.2%) was consistent across treatments, whereas survival differed markedly (base mix [BM] = 76%; pine bark [PB] = 64%; topure [TP] = 62%; oak soil [OS] = 50%). Seedlings in BM and TP accumulated the greatest total biomass and the highest sturdiness quotients, although all treatments remained below the value of 6 that denotes sturdy, well-balanced seedlings. The Dickson Quality Index, computed on a fresh-mass basis, did not differ significantly among substrates. Nitrogen concentration differed significantly among substrates (OS and TP > BM = PB), as did C: N, C: P, and N: P stoichiometric ratios, indicating substrate-driven variation in nutritional quality. The N: P ratios (3.7–5.4) were consistently below 10, suggesting nitrogen limitation across all treatments. Topure (TP) was the only substrate combining adequate morphological performance with enhanced N availability, offering a viable locally sourced alternative to reduce dependence on imported peat moss in community-based nurseries in western Mexico. This pattern is consistent with the high-P, low-N controlled-release fertilizer applied uniformly at transplanting, of which only a fraction of the nitrogen load would have been released within the 60-day window.