Herbicide Effects on Leaf Litter Decomposition Processes in An Oak‐Hickory Forest

Abstract

Herbicide treatments (2, 4, 5—Trichlorophenoxyacetic acid) of 0.225 g/m2 and 2.250 g/m2 were applied in a Latin square design to the forest floor of an oak—hickory forest in Georgia. White oak (Quercus alba) leaf litter decomposition and litter and soil microarthropod populations were studied in control and treated areas. Weight loss of natural white oak leaf litter averaged 35% for the 1st yr and reached 67% after 2 yr. Litter decomposition rates were similar in control and treated areas. However, white oak leaves defoliated through stem injections lost 59% of their biomass in 1 yr. Decomposition was increased because of initially higher N levels and a lower C:N ratio in defoliated leaf tissue. Herbicide spray treatment increased microarthropod densities for up to 8 mo after application. The herbicide spray apparently influenced springtail and mite reproductive activity in treated areas. The increases in soil and litter microarthropod densities were not sufficient to affect leaf litter weight losses. Repeated defoliation of plant communities and the resulting increased decomposition rates could cause imbalances in litter dynamics and cycling processes. Changes in the timing of annual litterfall and the rates of nutrient release may thus lead to soil desiccation and the depletion of available nutrient pools.

A technique for estimating rate of disappearance of dead herbage in pasture

“…It is probable that the herbage which was killed by the herbicide was chemically and structurally more susceptible to rapid breakdown by micro-organisms than material which had gone through the normal processes of senescence and death. Gottschalk and Spure (1979) have recently reported a similar result in a study of herbicide effects on leaf litter decomposition in forest.…”

Impact of heavy metals on mass and energy flux within the decomposition process in deciduous forests

“…In all three sites, the freshly fallen leaves, which in contrast to the mass loss investigations in the LCM, could only be included in this study (predominantly F. sylvatica, in Speyerer Hof mostly a mixture of F. sylvatica and Q. petraea) lost approximately 20% of their mass after 1 year of decomposition. Over the same time span, Gottschalk and Shure (1979) found a mass loss of Q. alba leaves of 35% (under climate conditions of Georgia, USA) and after 19 months, approximately 37% of the litter mass of Q. robur leaves were decomposed (in a woodland near Berlin, FRG) (Kratz and Bielitz 1989).…”

Environmental Impact of Triclopyr on Habitat Quality in Boreal Rights‐of‐Way

“…The rates of mass loss in our microcosm study (46%-47% at 121 days after treatment) were much higher than in our field study (~10% at 280 days after treatment to ~26% 1 year following treatment), likely influenced by the optimal conditions (60% soil water holding capacity, 20 ± 2 °C, 60% humidity, and 16:8-h light:dark photoperiod) maintained in microcosms. In our field study, litterbags were buried in late fall and recovered following winter, when decay rates were inhibited by colder temperatures (Gottschalk & Shure, 1979;Kim, 2007), thus resulting in lower mass loss rates in field conditions. In addition, within the first few months, litter can lose up to 30% of its mass from the leaching of water-soluble compounds (Berg & McClaugherty, 2003;Berg, 2014;Bryant et al, 1998;Naiman et al, 2005;Seastedt, 1984).…”

“…Far fewer examinations of herbicide toxicity have occurred in boreal ecosystems and, of these investigations, the main focus tends to be direct toxicity to plants, soil invertebrates, and wildlife (Clark et al, 2009; Isbister et al, 2017; Jimmo et al, 2018; Newton et al, 2008; Rombke et al, 2006; Wagner et al, 2004). However, herbicides can indirectly enter the soil ecosystem after leaf abscission, potentially leading to toxicity and avoidance by litter decomposers, impacting the litter decomposition rates and nutrient release that are critical for ecosystem health (Fletcher & Freedman, 1986; Gainer et al, 2019; Gottschalk & Shure, 1979). Plant litter decomposition and mineralization facilitated by soil invertebrates and microorganisms are essential in the formation of soil organic matter and soil fertility (Aber & Melillo, 1980; Carcamo et al, 2001) and contribute to habitat quality by providing nutrients to flora and fauna (see Seastedt, 1984).…”

“…Triclopyr is an herbicide that mimics the plant growth hormone auxin and inhibits senescence processes that translocate nutrients into belowground rhizomes before winter, consequently causing nutrients to remain in treated foliage (Brown, 1997; Gottschalk & Shure, 1979; Poovaiah, 1974). Moreover, auxin can indirectly inhibit lignification in leaves, resulting in lower lignin, a polymer that is challenging for microorganisms to metabolize (Austin & Ballare, 2010; Cromack & Monk, 1975; Gottschalk & Shure, 1979; Linck, 1976).…”