Fire acting as an increasing spatial autocorrelation force: Implications for pattern formation and ecological facilitation

TL;DR

This study investigates how fire influences vegetation spatial patterns, revealing that fire increases tree clustering and autocorrelation, with facilitation at fine scales and competition at coarser scales, impacting ecosystem dynamics.

Contribution

It demonstrates that fire acts as a force increasing spatial autocorrelation and aggregation of trees, highlighting scale-dependent facilitation and competition in ecosystems.

Findings

Fire increases tree clustering and spatial autocorrelation.

Positive autocorrelation at fine scales, negative at coarse scales.

Facilitation at small scales coexists with competition at larger scales.

Abstract

Fire is an indissoluble component of ecosystems, however quantifying the effects of fire on vegetation is challenging task as fire lies outside the typical experimental design attributes. A recent simulation study showed that under increased fire regimes positive tree-tree interactions were recorded (Bacelar et al., 2014). Data from experimental burning plots in an African savanna, the Kruger National Park, were collected across unburnt and annual burn plots. Indices of aggregation and spatial autocorrelation of the distribution of trees between different fire regimes were explored. Results show that the distribution of trees under fire were more clumped and exhibited higher spatial autocorrelation than in unburnt plots: In burnt plots spatial autocorrelation values were positive at finer scales and negative at coarser scales potentially indicating co-existence of facilitation and competition within the same ecosystem depending on the scale. The pattern derived here provides inference for (a) fire acting as an increasing aggregation & spatial autocorrelation force (b) tree survival under fire regimes is potentially facilitated by forming patches of trees (c) scale-dependent facilitation and competition coexisting within the same ecosystem with finer scale facilitation and coarser scale competition.