Bird functional diversity decreases with time since disturbance: does patchy prescribed fire enhance ecosystem function?

Abstract

Animal species diversity is often associated with time since disturbance, but the effects of disturbances such as fire on functional diversity are unknown. Functional diversity measures the range, abundance, and distribution of trait values in a community, and links changes in species composition with the consequences for ecosystem function. Improved understanding of the relationship between time since fire (TSF) and functional diversity is critical given that the frequency of both prescribed fire and wildfire is expected to increase. To address this knowledge gap, we examined responses of avian functional diversity to TSF and two direct measures of environmental heterogeneity, plant diversity, and structural heterogeneity. We surveyed birds across a 70-year chronosequence spanning four vegetation types in southeast Australia. Six bird functional traits were used to derive four functional diversity indices (richness, evenness, divergence, and dispersion) and the effects of TSF, plant diversity and structural heterogeneity on species richness and the functional diversity indices were examined using mixed models. We used a regression tree method to identify traits associated with species more common in young vegetation. Functional richness and dispersion were negatively associated with TSF in all vegetation types, suggesting that recent prescribed fire generates heterogeneous vegetation and provides greater opportunities for resource partitioning. Species richness was not significantly associated with TSF, and is probably an unreliable surrogate for functional diversity in fire-prone systems. A positive relationship between functional evenness and structural heterogeneity was common to all vegetation types, suggesting that fine-scale (tens of meters) structural variation can enhance ecosystem function. Species more common in young vegetation were primarily linked by their specialist diets, indicating that ecosystem services such as seed dispersal and insect control are enhanced in more recently burnt vegetation. We suggest that patchy prescribed fire sustains functional diversity, and that controlled use of patchy fire to break up large expanses of mature vegetation will enhance ecosystem function.

Drivers affecting mammal community structure and functional diversity under varied conservation efforts in a tropical rainforest in Cameroon

“…As a result, functional diversity is increasingly studied in different taxonomical groups (e.g. birds; Hidasi‐Neto, Barlow & Cianciaruso, ; Monnet et al ., ; Sitters et al ., ; fish; Wu et al ., ; Colin et al ., ; Teichert et al ., and mammals; Flynn et al ., ; Ahumada et al ., ; Chillo & Ojeda, ) and on regional and global levels (Safi et al ., ; Magioli et al ., ; González‐Maya et al ., ; Mazel et al ., ).…”

Logging and fire regimes alter plant communities

“…, Sitters et al. ). We assigned these categorizations based on field observation and literature reviews (Walsh and Entwisle , , , Costermans , Wood et al.…”

“…, Sitters et al. ). They also can act as surrogates for physiological functional patterns that are often impractical to measure (McIntyre and Lavorel , Diaz and Cabido ).…”

Spatiotemporal effects of logging and fire on tall, wet temperate eucalypt forest birds

“…Species with particular functional traits are prone to decline in landscapes undergoing change (Tylianakis et al 2008, Lindenmayer et al 2015, including those subject to fire (Sitters et al 2016). This is termed the "performance filtering hypothesis" (Mouillot et al 2012) in which particular functional traits can be "filtered out" by increasing amounts of disturbance in the landscape.…”

“…), including those subject to fire (Sitters et al. ). This is termed the “performance filtering hypothesis” (Mouillot et al.…”