Higher-Order Interactions Decline with Latitude in Global Forest Plots

A research paper titled 'Higher-order interactions enhance the latitudinal tree diversity gradient' was published in Nature. The study examined both pairwise interactions and higher-order interactions across 32 large permanent forest plots, most in the northern hemisphere.

@Nature reported that evidence of higher-order interactions was detected in 40% of the 1,543 species–plot combinations for tree growth.

The strength of higher-order interactions declines with latitude. Higher-order interactions benefit rare species but disadvantage common species.

The stabilizing effect of higher-order interactions weakened towards higher latitudes. This pattern is consistent with the global decrease in species diversity from low to high latitudes, among the most robust biogeographic patterns. There has been continuing debate on the contribution of conspecific negative density dependence to the latitudinal diversity gradient evident for trees.

Theory suggests that conspecific negative density dependence based on pairwise interactions alone is not sufficient to explain the intricacies of diverse communities because higher-order interactions may greatly modify these interactions. @Nature reported there has been a lack of empirical studies investigating how higher-order interactions intertwine with pairwise interactions and how they may contribute to the latitudinal tree diversity gradient.

The new findings reveal an important interplay between pairwise interactions and higher-order interactions in promoting the latitudinal tree diversity gradient.

They help to clarify the contribution of conspecific negative density dependence to this biogeographic pattern.