Differential responses of amphibian and reptile assemblages to size of riparian buffers within managed forests

Abstract

2019. Differential responses of amphibian and reptile assemblages to size of riparian buffers within managed forests. Ecological Applications 29(8):Abstract. Streamside management zones (i.e., riparian buffers; SMZs) are commonly implemented within managed forests to protect water quality but may also provide habitat for riparian-associated wildlife. Yet, little research has rigorously addressed the value of SMZs for wildlife, particularly for cryptic species such as amphibians and reptiles. Previous studies of herpetofauna within SMZs have focused on one or a few stream-associated species, and questions remain regarding variation among species or guilds and what role SMZs serve toward conservation of herpetofaunal diversity in managed forests. However, recent statistical advances have improved our ability to analyze large multi-species presence-absence data sets, accounting for low detection rates typical for some herpetofaunal species. Our study represents an extensive landscape-scale examination of herpetofaunal communities within SMZs using a multi-species occupancy approach. We conducted four replicate surveys at 102 headwater streams, spanning a gradient of SMZ widths and adjacent forest stand ages, within the Ouachita Mountains, Arkansas, USA. We used a hierarchical Bayesian community occupancy model to estimate species richness and species-specific occupancy responses to SMZ and overstory characteristics, accounting for variation in occupancy and detection attributable to site and sampling covariates. We documented high richness (37 species) within SMZs. Across the herpetofaunal community, occupancy and species richness were consistently positively associated with SMZ width, with maximum predicted richness of 30 species occurring at sites with buffers extending 51 m on either side of the stream. However, we documented considerable variation among groups and species within groups, underscoring the potential for different responses to forest management among taxa. Reptile predicted richness increased more rapidly up to SMZs of~35 m, whereas maximum salamander predicted richness was not seen until an SMZ width of 55 m. Estimated salamander richness was highest within SMZs embedded in mature managed pine stands and was higher in SMZs comprised of a deciduous or mixed overstory vs. a pine overstory. Compared to salamanders, more anuran species showed high mean estimated occupancy (>75%) at narrower SMZs (<30 m). Collectively, our results indicate that SMZs surrounding small first-order streams in intensively managed forests not only protect water quality, but also can support diverse amphibian and reptile communities.

Influence of landscape and vegetation characteristics on herpetofaunal assemblages in Gulf Coastal Plain pine forests

“…Further work is needed to understand herpetofaunal population dynamics in working forests, as evidenced by the relatively low occupancy estimates we saw for many species and by the variation in responses shown by herpetofauna to specific effects of forest management activities in other studies (Rothermel and Luhring 2005, Todd and Andrews 2008, Haggerty et al 2019. Low occupancy estimates are a common feature of many reptile and amphibian species (Guzy et al 2019, Zipkin et al 2020), but it can be difficult to discern if low estimates are due to sampling methodology, interspecific interactions, unincorporated landscape variables, or naturally sparse populations. While our results suggest that vegetation structure and soil characteristics are influential in determining species distributions, the broad scope of some of our covariates, like the long timeframe used to determine recent use of prescribed burns and the use of only a single season of vegetation data, might have dulled some inferences.…”

“…We used a model structure assuming static occupancy over the sampling period, given the short duration relative to the lifespans of our focal taxa, lack of intense management action within sites during the study, and the fact that the size of our sites exceeded the known home ranges of even the most wide-ranging of our target species (Bailey et al 2014, Howze andSmith 2015). We built a binary encounter matrix representing detection (1) and non-detection (0) data for each species at each site during each survey occasion and used a variation of the model written and modified by Zipkin et al (2009), Hunt et al (2012), and Guzy et al (2019). If species i occupies site j, then the true occupancy state z ij = 1, otherwise z ij = 0.…”

“…Few studies (Guzy et al 2019, Jones et al 2020) have rigorously assessed effects of vegetation structure on herpetofaunal assemblages and species distributions across heterogeneous landscapes with variable types and intensities of anthropogenic disturbance. Specifically, herpetofaunal communities in working loblolly pine forests and nearby longleaf forests remain understudied.…”

Riparian reserves protect butterfly communities in selectively logged tropical forest

“…In selectively logged subtropical and warm‐temperate forests of Australia, riparian reserves maintained bat activity similar to that of mature forests (Lloyd et al, 2006). Within intensively managed timber plantations in the United States, 30–50 m old‐growth forest buffers along streams support communities of birds, amphibians and reptiles typically associated with mature forests (Guzy et al, 2019), while webs of riparian grassland strips in South Africa maintained the abundance and species richness of dragonflies (Kietzka et al, 2021). However, insect species richness does not always correlate well with the level of disturbance (Bonebrake et al, 2010).…”

Multi‐species occupancy modeling provides novel insights into amphibian metacommunity structure and wetland restoration

“…MSOM have been integrated into a structured decision‐making approach to inform the management of amphibian communities, based on the inclusion of key habitat variables (hydroperiod, area, and connectivity) linked to important management decisions (Grant et al 2013). These models have also been used to evaluate anthropogenic impacts to amphibian communities and management practices (Muncy et al 2014, Guzy et al 2018, 2019). Rare amphibian species require sufficient data to inform management practices underpinned by clear inferences, yet these data are hard to obtain due to their rarity (MacKenzie et al 2005).…”