Rapid leaf decay and nutrient release in a chinese tallow forest

Abstract

The Chinese tallow tree, Sapium sebiferum, was introduced to the Texas Gulf Coast in the early 1900's and has spread into coastal prairie habitats. Since coastal prairie contains few deciduous trees, we studied leaf fall dynamics, rate of decomposition, and the quantity and rate of nutrient input from decomposing tallow leaves. Among-year leaf fall averaged 382.6 g·m·yr, similar to other south temperat deciduous forests and about as predicted by Meentemeyer et al.'s (1982) AE-lignin model. Decay of tallow leaves (k=-4.33) was much more rapid than native black willow (k=-0.35) and than other temperate deciduous trees (k=-0.77). The ratio of lignin to initial nitrogen concentration, highly correlated with rate of decomposition for hardwood trees, was low for Chinese tallow and may contribute to rapid leaf decay. Taking AE and lignin content into account, Meentemeyer's (1984) model predicted k=-1.39 for Chinese tallow and k=-0.88 for black willow. Decay of tallow was much faster but decay of willow was slower than predicted, suggesting that decay on the coastal prairie may be controlled by factors other than lignin content and climate. N, P, and K characteristically accumulate as leaves decay. However, these elements did not accumulate as tallow leaves decayed, possibly because high densities of Armadillidium vulgare, a detritivore, reduced immobilization of elements by microbes. This would result in increased turnover of these elements. Accumulation of Al, Fe, Zn, and S in decaying tallow litter may be related to flood-drain cycles on coastel prairie clay soils. Ca, N, K, Mg, and S were added to forest soil in greatest amounts from decaying tallow leaves. Concentrations of P, K, NO-N, Zn, Mn, and Fe were significantly higher and Mg and Na were significantly lower in forest than in prairie soil, raising the possibility that Chinese tallow trees altered the distribution of nutrients in the soil profile. We conclude that the Chinese tallow tree may enhance productivity in ecosystems to which it has been introduced by addition of nutrients from rapid decay of leaves.

Litter traits and palatability to detritivores: a case study across bio-geographical boundaries

“…It could be possible to predict the direction of the effect that changing litter traits will have on decomposition rates, based on the differences between the native and exotic litter. For instance, Cameron and Spencer (1989) reported an increase in decomposition and nutrient cycling following invasion by a plant that produced faster decomposable litter (low lignin:N ratio) than the natives, and the exotic litter was consumed by the isopod Armaddillidium vulgare, an important detritivore in the area. On another situation, the litter produced by an invasive grass had a high C:N ratio and, as expected, was rejected by P. scaber (Bastow et al, 2008).…”

Implications of newly-formed seed-dispersal mutualisms between birds and introduced plants in northern California, USA

“…The species has become highly invasive in the southeastern U.S., where it infests large floodplain, wetland, and low-lying forest areas, enriching soil and forming monocultures that displace native species (Bruce et al 1997;Cameron and Spencer 1989;Jubinsky and Anderson 1996). Fourteen bird species in the invaded region have been shown to consume T. sebifera seeds (Renne et al 2000).…”

Effects of simulated herbivory and resource availability on native and invasive exotic tree seedlings

“…Although no native Euphorbiaceae tree exists for comparison, Celtis laevigata is a common native tree found in coastal prairies, recently abandoned agricultural fields, woodland thickets, and other habitats where Sapium is found (Cameron & Spencer 1989, Bruce et al 1995, Harcombe et al 1999. Like Sapium, Celtis has a similar flowering and fruiting phenology and is insect pollinated and bird dispersed (Schopmeyer 1974).…”

“…A 20-year record of sapling growth and mortality in an East Texas floodplain forest reveal that Celtis is the most similar native species to Sapium (Paul Harcombe, Rice University, unpublished data). Likewise, after Sapium, Celtis is the second most abundant tree species establishing in coastal prairies and Sapium woodlands (Cameron & Spencer 1989, Bruce et al 1995. Celtis is readily consumed by a variety of insects (personal observation), but is considered tolerant of moderate levels of herbivory (van Auken & Lohstroh 1990).…”

“…Sapium's success as an invader is frequently attributed to a lack of pests and pathogens (Scheld & Cowles 1981, Harcombe et al 1993, Jubinsky & Anderson 1996, Bruce et al 1997. Observations support that Sapium loses very small amounts of leaf area to herbivory in the United States (Scheld & Cowles 1981, Siemann & Rogers 2001) and its leaves are presumed to contain costly secondary metabolites that repel herbivores (Cameron & Spencer 1989, Jubinsky & Anderson 1996.…”