Effects of soil water regime and ECM inoculant on soil’s N & P availability and the above-ground physiological structure of Pinus brutia seedlings

Abstract

The Calabrian trees (Pinus brutia) are negatively affected by climate change due to prolonged and intense fires, as well as extended drought, especially in the summer. One main problem that may arise, is the under-development of the species and its time of maturity until the next fire incident. While research on the effects of climate change on the Calabrian trees continues to expand, as well as some methods to mitigate these effects, there has been very limited research on the mitigation of these effects using ectomycorrhiza in the earliest stages of trees’ development, while they are seedlings. This experiment could provide knowledge about the impact of early inoculation on seedlings’ development and consequently mature trees’ development. Overall, this study aimed to investigate the effect of ectomycorrhizal (ECM) spores’ inoculation, on four-months-old Pinus brutia seedlings, focusing on aboveground development as well as the water and nutrient uptake of the seedling. Sixty large pots were prepared and four treatment groups were created, regarding the irrigation and the inoculation status – Inoculation: Yes/No, Water: 300ml/1000ml. During the experimental period, from April to July, once a month, seedlings’ height, soil humidity, soil nitrate, ammonium, and phosphate concentrations were measured. ECM inoculation as well as its interaction with the water treatment significantly affected the percentage growth of shoot height. The inoculated seedlings showed less increase than the non-inoculated seedlings. ECM inoculation didn’t significantly affect the percentage change in stem height. Nitrate concentration in soil showed a higher plant uptake in the final month. In non-inoculated pots, a significant increase occurred possibly due to higher nitrification rates and lower plant uptake. Ammonium concentration was affected by the inoculation and its interaction with the water treatment. One of the inoculated groups contained much higher ammonium content than any other treatment group. Probably because of the ability of ECM to stabilise ammonium and prevent it from being converted to nitrate quickly. Additionally, regarding phosphates, the inoculation caused a larger uptake by the seedlings, especially during May-June. Soil humidity was only significantly affected by water treatment, and not by inoculation. As expected, there was a gradual reduction of soil humidity, due to high temperatures. ECM infection rates were much higher in inoculated seedlings (100%) compared to non-inoculated seedlings (16.7%). Overall, the results suggest that early ECM inoculation allows for greater nutrient absorption by seedlings, higher resilience for abiotic stresses (e.g., high temperature), and less investment in aboveground development.