bwimage: A package to describe image patterns in natural structures

Currently R is the most popular software for data analyses among biologists. Here, we present bwimage, a package designed to describe patterns from black and white images. The package can be used for a wide range of applications. We implemented functions previously described in the literature to calculate parameters designed originally, but not exclusively, for vegetation structures. Additionally, we propose a new parameter: the aggregation index. We demonstrate applications for field work, providing examples that range from calculation of canopy openness, description of patterns in vertical vegetation structure, to patterns in bird nest structure. We provide advice and illustrated examples of how to produce high quality images for analyses.

bwimage: A package to describe image patterns in natural structures

Currently R is the most popular software for data analyses among biologists. Here, we present bwimage, a package designed to describe patterns from black and white images. The package can be used for a wide range of applications. We implemented functions previously described in the literature to calculate parameters designed originally, but not exclusively, for vegetation structures. Additionally, we propose a new parameter: the aggregation index. We demonstrate applications for field work, providing examples that range from calculation of canopy openness, description of patterns in vertical vegetation structure, to patterns in bird nest structure. We provide advice and illustrated examples of how to produce high quality images for analyses.

An introduced plant is associated with declines in terrestrial arthropods, but no change in stream invertebrates

Riverine systems often spread non-native species, yet the co-occurring impacts of introduced riparian vegetation on aquatic- and terrestrial-derived resources are unknown. We compared aquatic and terrestrial arthropod communities and their flux into and out of streams in riparian reaches invaded and uninvaded by Robinia neomexicana, a woody plant introduced to a western Colorado watershed. We found that invaded reaches had fewer terrestrial arthropods collected off foliage, conceivably because of the plant’s later leaf-out phenology. Overall, seasonal and annual factors best described terrestrial and aquatic arthropod communities. However, when we evaluated vegetation and stream characteristics in lieu of season and year, we found terrestrial arthropod biomass and richness were negatively related to cover of R. neomexicana and positively related to vegetative cover, forb cover, and vertical vegetation structure. Our results suggest ecosystems respond to landscape variation differently, where directly related food web components (i.e., terrestrial arthropods on introduced vegetation) respond stronger than more distally related constituents (i.e., aquatic insects).

bwimage: A package to describe image patterns in natural structures

Currently R is the most popular software for data analyses among biologists. Here, we present bwimage, a package designed to describe patterns from black and white images. The package can be used for a wide range of applications. We implemented functions previously described in the literature to calculate parameters designed originally, but not exclusively, for vegetation structures. Additionally, we propose a new parameter: the aggregation index. We demonstrate applications for field work, providing examples that range from calculation of canopy openness, description of patterns in vertical vegetation structure, to patterns in bird nest structure. We provide advice and illustrated examples of how to produce high quality images for analyses.

Prescribed burning as a conservation tool for management of habitat for threatened species: the quokka, Setonix brachyurus, in the southern forests of Western Australia

Prescribed burning is frequently advocated as a means of managing habitat for threatened species. We studied effects of fire on the quokka (Setonix brachyurus), a species currently used as a focal species for planning prescribed burns in the southern forests of Western Australia. We examined (i) the recolonisation of burnt areas; (ii) the refuge value of unburnt vegetation; and (iii) fire prediction variables that may help to guide fire planning to achieve desired habitat management outcomes. We hypothesised that fire regimes promoting vegetation structure and patchiness of burnt and unburnt vegetation would result in more rapid recolonisation of burnt areas by quokkas. Occupancy modelling identified the most important variables for recolonisation as retention of vertical vegetation structure and multiple unburnt patches across >20% of the total area. These outcomes were associated with high surface moisture, low soil dryness and slow fire rates of spread. Intense wildfire resulted in complete loss of vegetation structure and a lack of unburnt patches, which contributed to these areas remaining uncolonised. Burning with high moisture differentials, maximising the effectiveness of edaphic barriers to fire, retaining unburnt vegetation and maintaining vegetation structure were found to be important elements of fire regimes in this region.