Stability in Relation to Nutrient Enrichment in Arthropod Consumers of Old‐Field Successional Ecosystems

Abstract

Two adjacent, abandoned hayfields in central New York State were subjected to nutrient enrichment perturbation by means of a single application of 10-10-10 N, P, K fertilizer early in the growing season of 1970. Aboveground arthropod herbivores and carnivores were monitored with respect to net productivity (dB/dt) and diversity for one growing season (1970) in the younger field (6 yr old), and for two growing seasons (1970 and 1971) in the older field (17 and 18 yr old). Sampling of arthropods was done with a gasolinepowered suction sampler between 1200 and 1600 h, twice weekly.Stability of the old-field arthropods was defined as resistance to change imposed by external (fertilizer) perturbation and was measured in terms of (1) magnitude (amplitude of deflection from ground state, (2) rate of initial response to perturbation, and (3) rate of damping or return to ground state. The degree of deflection from ground state was determined by comparing fertilized (treated) plots with unfertilized (control) plots in each field.During the first growing season the older, more species-rich field was less stable with respect to magnitude and rate of productivity deflection than the younger, less species-rich field at both arthropod consumer levels. In addition, the magnitude of productivity deflection from ground state was lower in the carnivore level than in the herbivore trophic level.By the second growing season, the productivity of the arthropod consumers in the treated plots of the older field had not yet returned to control levels. The productivity of arthropod herbivores in the older field exhibited a relatively lower magnitude of response in 1971 than in 1970, while the arthropod carnivores in the older field exhibited a significantly greater difference from ground state in 1971 than in 1970.It was concluded that ( 1) the magnitude of deflection caused by the enrichment perturbation was decreased up the trophic levels from the herbivore to the carnivore level, (2) the rate of response to perturbation decreased up the trophic levels, and (3) although in control plots diversity increased and productivity decreased with increasing successional age for both trophic levels, stability was not positively related to either higher diversity or to increasing age in either consumer trophic level in this old-field successional ecosystem.

The effects of foliar pubescence and nutrient enrichment on arthropod communities ofMetrosideros polymorpha(Myrtaceae)

“…Herbivore and detritivore biomass also increased in some fertilised blocks, but this effect was weak and variable (Table 2), consistent with a related study that showed smaller individuals dominate the response to nutrient enrichment (Gruner, 2004b). Responses of community species richness or diversity in other studies have been more variable and equivocal than abundances (Hurd & Wolf, 1974;Kirchner, 1977;Sedlacek et al, 1988;Haddad et al, 2000). Discrepancies in the qualitative responses of diversity across systems may be biologically based and system specific, or might vary according to differences in spatial scale (Whittaker & Heegaard, 2003), trophic or taxonomic focus (Haddad et al, 2000), diversity metric or standardisations employed (McCabe & Gotelli, 2000), or experimental time frame (Haddad et al, 2000).…”

Richness and species composition of arboreal arthropods affected by nutrients and predators: a press experiment

“…However, the estimates of species richness from individual-based rarefaction did not increase with fertilization for any trophic group. Numerous studies have examined the diversity of herbivorous or other arthropods in response to fertilization, but generalizations have been elusive (e.g., Hurd and Wolf 1974;Kirchner 1977;Kajak 1981;Vince et al 1981;Prestidge 1982;Strauss 1987;Sedlacek et al 1988;Siemann 1998;Haddad et al 2000). However, several of these studies observed higher abundance of sap-sucking Auchenorryncha and other herbivorous groups, but decreasing evenness and diversity as a small number of species emerged as dominant (Prestidge 1982;Sedlacek et al 1988;Haddad et al 2000).…”

Top‐Down Cascade from a Bitrophic Predator in an Old‐Field Community

“…Therefore, generalist predators like these mantid nymphs exert different effects on the plant community than would a specialist predator attacking only one or a few prey items. Another effect of enhanced primary production on consumers may be increased fecundity, which would show up as higher abundance and secondary productivity the following season (Hurd and Wolf 1974). In any case, that mantids can exert strong direct and indirect effects on herbivorous arthropods has been documented by Eisenberg (1984b, 1990a) for T. sinensis, and by Mook and Davies (1966) and Hurd (1991, 1994) for another temperate mantid, Mantis religiosa.…”