Abstract
AbstractLand use and corresponding habitat loss are major drivers of local species extinctions. Orthoptera as important grassland herbivores showed different responses to land‐use intensity in different studies, and the susceptibility of this group remains unclear. We sampled annually for seven years 150 temperate grassland sites across three regions in Germany, for which land‐use gradients were quantified as mowing, grazing, and fertilization intensity. We analyzed the effects of land‐use intensity on orthopteran diversity and community abundance. To describe species‐specific responses to environmental gradients, we employed a new approach termed “niche model,” coupled with a randomization procedure, which is sensitive even for rare species for which trends may otherwise be difficult to detect. Based on abundance‐weighted means for each species, we quantified the species' occurrence along land‐use gradients and identified potential losers and winners of intensive land use. Overall, high land‐use intensity negatively affected orthopteran diversity across years and regions, corresponding to decreases with high fertilization, mowing, and grazing intensity. Intensive mowing and grazing negatively affected abundance. Diversity and abundance increased with the time after the last cut. The niche model detected 15 of 29 Orthoptera species as losers of land use, showing significantly higher abundance in grasslands with low‐intensity land use. Two species were winners of high land‐use intensity, whereas the remaining 12 were assigned as opportunists. Most species were losers of high fertilization intensity, followed by frequent mowing. Grazing intensity was least detrimental at the species level. Omnivorous, herbivorous, and graminivorous species did not differ in their response to land‐use intensity, whereas bryovorous/lichenivorous Tetrix species showed consistently negative responses to intensive land use. Our highly replicated, long‐term and large‐scale survey suggests that further land‐use intensification threatens many Orthoptera and causes a consistent diversity loss. Low intensity of fertilization, infrequent mowing, and variable grazing will help to maintain a high diversity of orthopterans. The generality of our niche model approach advances studies on species' susceptibility in various study systems.
Highlights
The current loss of species is to a great extent caused by anthropogenic influences (Pimm et al 1995, Hooper et al 2005), especially by land-use change and intensification (Tilman et al 2001) and by the corresponding loss or fragmentation of habitats (Krauss et al 2010)
A total of 32 Orthoptera species out of eight subfamilies were recorded in 150 sites, thereof 19 in ALB, 19 in Schorfheide- Chorin (SCH), and 14 in Hainch-Dün and its surrounding areas (HAI)
We have looked into the dynamics of diversity changes following mowing: Orthopteran diversity and total abundance increased with the time span between sampling and last cut, which may probably be due to more time for migration from neighboring habitats, repopulation, and egg hatching
Summary
The current loss of species is to a great extent caused by anthropogenic influences (Pimm et al 1995, Hooper et al 2005), especially by land-use change and intensification (Tilman et al 2001) and by the corresponding loss or fragmentation of habitats (Krauss et al 2010). Intensified land use is often described to decrease biodiversity, such as plant species richness (Haddad et al 2000, Kleijn et al 2009) and insect diversity (Haddad et al 2000, Allan et al 2014). These negative effects are often related to nitrogen input by fertilization (Van Den Berg et al 2011, Socher et al 2012, Simons et al 2014). Microbial biomass and fungal abundance decline with decreasing plant species richness (Zak et al 2003) and arthropod species richness declines (Haddad et al 2001, 2009, Allan et al 2014, Simons et al 2014), especially of herbivorous insects (Scherber et al 2010)
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