Grasslands of cleared woodlands have lower invertebrate diversity and different assemblages to remnant woodlands in grazed landscapes of eastern Australia

Abstract

Clearing of woodlands is used by graziers to promote pasture production, even though understanding of impacts of clearing on native fauna is lacking. We evaluate impacts of clearing on biodiversity by comparing invertebrates associated with ground-layer vegetation of cleared woodlands (grasslands) to that of nearby uncleared woodlands. Two replicates of grasslands consisting of pastures dominated by introduced grasses were compared with two woodlands at each of four locations. The adjacent riparian forest to each grassland and woodland site allowed evaluation of the effect of woodland clearing on the adjacent riparian zone. All habitats were grazed. Invertebrates of ground-layer vegetation were sampled using three suction subsamples of 1m2 at each site. Grasslands had significantly lower order richness and abundance of herbivores, pollinators and macroinvertebrates (food for birds) than the woodlands, whereas the riparian forests closely resembled each other in all metrics. Invertebrate assemblages of grasslands also differed significantly from those of the woodlands. BEST analysis showed that groundcover and leaf-litter percentage cover correlated strongest with invertebrate composition. This study has demonstrated that grazing management relying on clearing of fertile grassy woodlands of the rangelands of Central Queensland alters invertebrate diversity and assemblage. Thus, tree clearing not only leads to biodiversity losses in the canopy layer, but also in the ground-layer vegetation. Implications for insect conservation Pastoralists have the capacity to improve outcomes for invertebrate biodiversity by maintaining groundcover (ground-layer vegetation and litter cover) above 80%, by encouraging native pastures over introduced species such as Buffel Grass and by retaining native woodlands.

Influence of Riparian Conditions on Physical Instream Habitats in Trout Streams in Southeastern Minnesota, USA

“…Studies suggest that there may be a significant time lag between the establishment of new buffers and observable improvement in instream habitats; although, it may be possible to observe some improvements soon after buffer establishment [58]. We observed several "good" characteristics typically associated with ideal riparian zones, including long overhanging vegetation [31], minimal bare soil [27], bank reinforcement with natural rocks, and scattered shrubs and trees on and/or along the banks [12]. These features were correlated with better instream cover, more coarse substrates, reduced embeddedness, more pool habitat, and reduced fine sediments.…”

“…In the mid-1990s, the need for guidelines to protect riparian zones (at a basic level) was initiated by several nations, including the United States, Australia, New Zealand, Canada, United Kingdom, Sweden, and South Africa [80,81]. To that end, strategies to protect riparian areas began initially with forested buffers (improved forest management) [75], later expanding to include grassy buffers [31,82]. Despite a deeper understanding (i.e., how to protect, issues with scale, determining necessary width, and so on), monitoring of important river features is often overlooked.…”

“…Maintaining a healthy riparian zone in agricultural settings can include the creation of wide buffers [27] and/or excluding livestock by fencing the corridor [28]. Ideal instream conditions such as reduced temperatures [28], reduced fine-sediment inputs [29], suitable instream habitat and cover for aquatic life [12], and narrower, deeper channels with stable banks [30] may be achieved via well-vegetated banks and mixed deciduous trees [31].…”