Drought effects on fine-root and ectomycorrhizal-root biomass in managed Pinus oaxacana Mirov stands in Oaxaca, Mexico

Abstract

The effects of a severe drought on fine-root and ectomycorrhizal biomass were investigated in a forest ecosystem dominated by Pinus oaxacana located in Oaxaca, Mexico. Root cores were collected during both the wet and dry seasons of 1998 and 1999 from three sites subjected to different forest management treatments in 1990 and assessed for total fine-root biomass and ectomycorrhizal-root biomass. Additionally, a bioassay experiment with P. oaxacana seedlings was conducted to assess the ectomycorrhizal inoculum potential of the soil for each of the three stands. Results indicated that biomasses of both fine roots and ectomycorrhizal roots were reduced by almost 60% in the drought year compared to the nondrought year. There were no significant differences in ectomycorrhizal and fine-root biomass between the wet and dry seasons. Further, the proportion of total root biomass consisting of ectomycorrhizal roots did not vary between years or seasons. These results suggest that both total fine-root biomass and ectomycorrhizal-root biomass are strongly affected by severe drought in these high-elevation tropical pine forests, and that these responses outweigh seasonal effects. Forest management practices in these tropical pine forests should consider the effects of drought on the capacity of P. oaxacana to maintain sufficient levels of ectomycorrhizae especially when there is a potential for synergistic interactions between multiple disturbances that may lead to more severe stress in the host plant and subsequent reductions in ectomycorrhizal colonization.

Ectomycorrhizal communities in a Mediterranean forest ecosystem dominated by Quercus ilex: seasonal dynamics and response to drought in the surface organic horizon

“…The mechanisms underlying these shifts may include responses of both trees and ECM symbionts. For instance, ecophysiological adaptations of forest trees to drought, such as reduced fine root production (Valdes et al 2006), may in turn drive fungal shifts. Similarly, ECM symbionts unequally survive drying under controlled conditions (di Pietro et al 2007).…”

Modelling intra- and inter-annual growth dynamics of Scots pine in the whole-tree carbon balance framework

“…11). Measurements of root phenology are limited (Du andFang 2014, Delpierre et al 2016a) but root growth is strongly affected by soil temperature and moisture (Bowen 1970, Valdés et al 2006 and it continues until autumn if conditions are favourable (Puhe 2003, Steinaker et al 2010. The lengths of the growth periods as presented here thus vary from two months (primary growth) to four months (secondary growth, root growth) (II, Fig.…”

“…Water availability has also a direct effect especially on secondary growth via turgor pressure, which drives cell enlargement ) and via cambial activity, which is decreased under drought conditions (Deslauriers et al 2016). Low levels of soil moisture also decrease or inhibit root growth (Bowen 1970, Valdés et al 2006.…”

“…Babst et al 2013), leaves (e.g. Norgren and Elfving 1994) and roots (Valdés et al 2006). For example, some important results of the temperature dependence of growth date back decades or even centuries (De Réaumur 1735, Sarvas 1972.…”

Ectomycorrhizal Fungi and Their Applications

“…Their data have demonstrated an important effect of rainfall and soil moisture on community composition at the species level and less infl uence of temperature on the abundance of ECM exploration types. Valdés et al ( 2006 ) observed that a severe drought had an important effect on both total fi ne-root biomass and the ECM-root biomass in a tropical pine forest and suggested that forest management practices should consider the effects of drought in reducing the capacity of Pinus oaxacana to form ECM.…”