How to Define Spacing Among Forest Trees to Mitigate Competition: A Technical Note

Abstract

Defining the optimal spacing between tree species to reduce competition and thus mitigate drought effects is essential but highly complex. The equilibrium in terms of the number of trees, where competition for shared resources like water, nutrients, and light is minimized, depends on various environmental and tree-related factors. This study, conducted in the temperate Norway spruce forests of the Czech Republic at an altitude of 400–500 m, introduces a new method for determining ideal tree spacing to reduce competition. Here, we filtered out the effects of elevation and diameter at breast height on field-measured xylem sap flow for 101 Norway spruce trees, aiming to account for the most important driver of sap flow variability: tree density and its underlying effects on individual tree traits. We found that when the N number of trees (median) per unit area has the least competition pressures, adding or removing the n number of trees may not significantly change the situation, thus affecting competition among trees. The tolerance capacity (n) is a function of area (A) that determines the permissible deviation from N. Our technique offers a new tool for forest managers and policymakers, helping them make informed decisions about thinning and plantation strategies based on elevation gradients.