Contribution of feeding by European pine sawfly larvae to litter production and element flux in Scots pine plantations

Abstract

The contribution of larvae of the European pine sawfly, Neodiprionsertifer (Geoff.), to litter fall and element input was determined in two contiguous 25-year-old plantations of Scots pine (Pinussylvestris L.) near Glencairn, Ont., in 1972. Tree spacings were 1.2 × 1.2 and 1.8 × 1.8 m. Tree diameters, numbers of needle-bearing branches per tree, and the number of larval colonies per tree were greater in the less dense plantation. On the other hand, there was no difference between plantations with respect to tree height, number of needles per branch, number of larvae per colony, or percent defoliation. For the denser and less dense plantations, frass was the largest insect-derived component of litter fall at 804 and 1255 kg ha−1, respectively; needles constituted the major tree component of litter fall at 1107 and 929 kg ha−1, respectively, and the total combined contribution of tree and insect material to litter fall was 2395 and 2744 kg ha−1, respectively. Average element input (kilograms per hectare) to the soil via frass for the two plantations was greatest for nitrogen (6.9), followed by potassium (5.0), calcium (4.1), phosphorus (0.8), and magnesium (0.6).

The influence of a neotropical herbivore (Lamponius portoricensis) on nutrient cycling and soil processes

“…Selective, and often dramatic, feeding by insect herbivores exerts a strong influence on a number of forest ecosystem properties (Schowalter 2000). In addition to the welldocumented and conspicuous effects that they can have on plant growth and survival, herbivores can substantially alter plant species composition (Ritchie et al 1998) and the flow of nutrients within forest systems (Swank et al 1981;Fogal and Slansky 1985;Hollinger 1986;Schowalter et al 1991;Hunter 2001).…”

“…Although a number of experiments have demonstrated modification of canopy inputs by insect herbivores (e.g., Kimmins 1972;Ohmart et al 1983;Fogal and Slansky 1985;Grace 1986;Hollinger 1986;Risley and Crossley 1988;Lightfoot and Whitford 1990;Stadler and Michalzik 2000), few have addressed the effects of these modified inputs on the soil subsystem or plant growth (Seastedt et al 1983;Schowalter et al 1991;Lovett and Ruesink 1995;Belovsky and Slade 2000;Reynolds and Hunter 2001;Chapman et al 2003;Hunter et al 2003). Some have speculated that the addition of herbivore inputs could accelerate rates of nutrient cycling and even enhance primary productivity (Mattson and Addy 1975;Kitchell et al 1979).…”

Soil carbon and nitrogen mineralization following deposition of insect frass and greenfall from forests under elevated CO2 and O3

“…This fast processing of organic matter is possible because, unlike senesced leaves that have much of their nutrient content resorbed, frass and greenfall inputs are "higher quality" inputs that may contain 74% more available nitrogen than senescent leaves (Risely and Crossley 1993;Fonte and Schowalter 2004;Madritch et al 2007a). Further, soil nitrogen inputs from frass can exceed those from leaf litter during severe outbreaks (Fogal and Slansky 1984;Grace 1986;Hollinger 1986). Frass and greenfall inputs to the soil may result in increased nitrogen mineralization (Constantinides and Fownes 1994;Lightfoot and Whitford 1990;Reynolds et al 2000) leading to enhanced microbial immobilization (Lovett and Ruesink 1995;Christenson et al 2002;Lovett et al 2002) or export from the system (Swank and Crossley 1988;Eshleman et al 1998).…”

Modeling nitrogen flux by larval insect herbivores from a temperate hardwood forest

“…In forested biomes, in particular, larval insect herbivores are responsible for transforming and translocating (sensu Vanni 2002) considerable amounts of nitrogen (N) from the canopy to the soil in the form of frass (Fogal and Slansky 1985;Hollinger 1986;Reynolds and Hunter 2001;Lovett et al 2002;Hunter et al 2003). Frass-derived N typically falls at the peak of the growing season and is in a highly labile form (Lovett and Ruesink 1995).…”

“…Nitrogen inputs from insect frass are typically quantified by collecting frass in trays placed on the forest floor, weighing and analyzing the N concentration of the frass, and calculating the amount of N deposited per unit area and time (Fogal and Slansky 1985;Hunter et al 2003). A complementary approach to estimating frass N inputs is to scale individual N flux to the community level using general models of individual flux and information about community structure.…”