Effect of Herbage Density, Height and Age on Nutrient and Invertebrate Generalist Predator Abundance in Permanent and Temporary Pastures

Abstract

The aim of this research was to assess differences in the quantity and quality of herbage and invertebrate generalist predator abundance among permanent and temporary pastures. Two permanent pastures and four temporary ley pastures (either one year or two years since being sown) were monitored weekly for 10 weeks in the spring. Permanent pastures included a diverse range of native UK grass species, and temporary ley pastures were predominantly perennial ryegrass (Lolium perenne) with or without white clover (Trifolium repens). Weekly measurements of herbage height (in centimeters), herbage cover (fresh and dry matter in kg per hectare) and herbage density (fresh and dry matter in kg per hectare per centimeter) were obtained for each field, along with lycosid spider and carabid beetle abundance. Weekly pasture samples were used to obtain nutrient concentrations of dry matter, crude protein, neutral detergent fibre (NDF), acid detergent fibre (ADF), ash, oil, sugars, digestible organic matter in the dry matter (DOMD) and metabolisable energy (ME) in the herbage as a measure of forage quality for grazing or harvesting. A linear mixed model was used to assess the effect of sward age, herbage density and height on herbage production, nutrient concentrations and invertebrate abundance. Although this study showed that permanent pastures were associated with lower nutrient concentrations of crude protein, ash, oil and ME compared to younger and predominantly perennial ryegrass pastures, the older pastures were associated with higher carabid numbers. Furthermore, permanent pastures had a higher density of dry matter herbage compared to younger pastures, and more dense and taller swards were associated with higher lycosid numbers. The study suggests that within pastures of 3 to 20 cm height, increasing the height and density of swards increases both ME and oil concentrations in herbage, therefore enhancing forage nutrient quality. Older and more permanent pastures can be beneficial for plant and invertebrate generalist predator populations, and still provide a useful source of nutrients for forage production.

Ground beetles in Romanian oilseed rape fields and adjacent grasslands (Coleoptera: Carabidae)

“…ALEKSANDROWICZ and BAGIŃSKA, 2009;TEOFILOVA and KODZHABASHEV, 2020). Other important factors are the plant species diversity (BYERS et al, 2000), and dry matter density (TOUPET et al, 2020).…”

Effect of pasture cover and height on nutrient concentrations in diverse swards in the UK

“…Toupet et al (2020) found that permanent pastures had a higher density of dry matter herbage compared to younger pastures, and more dense and taller swards were beneficial for biodiversity such as invertebrates including lycosid spiders, and older swards being associated with higher abundance of carabid beetles. Generalist predators such lycosids and carabids are valuable for agricultural systems as they contribute to the fundamental ecosystem service of biological control of insect pests (Begg et al, 2017; Michalko et al, 2019), but there abundance is influenced both by the physical composition of the landscape and by how it is managed (Rusch et al, 2014; Holland et al, 2016).…”

“…Prior to the commencement of the study, the nutrient concentrations of 30 pasture samples (5 from each field) measured by the NIRS device were compared to wet chemistry analysis with the following correlations ( r ) for crude protein ( r = 0.48), neutral detergent fiber ( r = 0.41), sugars ( r = 0.78), oil ( r = 0.74), ash ( r = 0.30), digestible organic matter ( r = 0.79), nitrate nitrogen ( r = 0.63) and metabolizable energy ( r = 0.78). The NIR4 has been collaborated for fresh grass from different pasture types over several years (Bell et al, 2018; Toupet et al, 2020). The device takes five replicate scans, consisting of a spectrum of infrared energy reflected from the pasture sample illuminated by the scanner, from which nutrient concentrations are estimated from the average of the five scans.…”

Strands of Connection: Livestock Grazing, Vegetation Density, and Orb-Weaver Spider Persistence

“…While A. argentata seems to respond directly to grazing, A. quadrilorata , which exclusively inhabits the cattle-resistant Eryngium horridum , is indirectly affected by grazing. Therefore, although grazing may not be the best solution for all kinds of grassland management (Helden et al 2020), moderate grazing using limited animal load, up to 0.6 AU/ha/year (Jansen et al 2013; Clendenin 2016; Toupet et al 2020), seems to have the potential to maintain and preserve spiders and other generalist predators that are intrinsically linked to vegetation structure. Moreover, the ability of these spiders to disperse through ballooning offers a potential survival strategy in the face of grazing pressure, but it presents challenges related to identifying suitable habitats.…”