Litter cover as an index of nitrogen availability in rehabilitated mine sites

Abstract

The spatial heterogeneity of litter cover and bioavailability of nitrogen within a 9-year-old rehabilitated bauxite mine in south Western Australia was examined. Three replicate plots (6 m by 6 m) were each divided into 100 quadrats. Litter cover, vegetation distribution, and projected foliage cover were mapped, and litter (overstorey leaves, understorey leaves, and other assorted fractions) and soil (depth: 0–5, 5–10, and 10–30 cm) were sampled from within each quadrat. Litter distribution reflected projected foliage cover, and accumulated within microtopographic depressions. Distribution of soil nitrate (NO3–) reflected the distribution of litter. The 15N natural abundance (d15N) values of soil (0–5 cm) and the understorey litter fraction were significantly correlated (R2 = 0.529, P < 0.05), whereas carbon isotope composition (d13C) of soil (0–5 cm) was significantly correlated with the distribution of the assorted litter fraction (R2 = 0.296, P < 0.05). It is concluded that site preparation practices that effect microtopography, such as contour ripping and revegetation along contours, will have a significant impact on nitrogen (N) distribution and bioavailability within rehabilitated mine sites.

Long-term impact of prescribed burning on the nutrient status and fuel loads of rehabilitated bauxite mines in Western Australia

“…The soil C:N ratio in all of the burn treatments was less than 20:1, which is comparable to levels recorded for unmined forest in the current study but considerably lower than the ratios of 35-45:1 previously recorded in the jarrah forest (Wallace and Hatch, 1952;Todd et al, 2000). The high proportion of litterfall from leguminous species in rehabilitated areas that have a high concentration of N and other nutrients predispose them to rapid decomposition (Hingston, 1980).…”

“…The high proportion of litterfall from leguminous species in rehabilitated areas that have a high concentration of N and other nutrients predispose them to rapid decomposition (Hingston, 1980). For eucalypt forests, the soil C:N ratio largely determines the rates of mineralisation and nitrification (Todd et al, 2000). Generally, there is little mineralisation of organic matter until the C:N ratio is reduced to less than 20:1 (Adams et al, 1989;Attiwill et al, 1996).…”

Plant and Soil Responses to Created Microtopography and Soil Treatments in Bottomland Hardwood Forest Restoration

“…Topographic heterogeneity has long been recognized as an important component of bottomland hardwood forests (Oosting 1942; Wikum & Wali 1974; Buchholz 1981; Hardin & Wistendahl 1983), and spatial heterogeneity is thought to promote diverse communities (Huston 1994). Small‐scale microtopographic heterogeneity, on the order of decimeters or less, influences community structure directly and indirectly through various mechanisms, including differential seedling recruitment along hydrologic gradients (Keddy & Ellis 1984), variation in litter accumulation (Todd et al 2000), differences in plant establishment and mortality due to microsite characteristics (Eldridge et al 1991), and variation in biogeochemical cycling in response to flooding regimes (Darke & Walbridge 2000). Microtopographic heterogeneity in bottomland forests is often created through disturbances such as tree fall, sediment accumulation, erosion following flooding, and animal activities (Ehrenfeld 1995).…”

“…Although microtopographic variation is an important and natural part of bottomland hardwood forests, the creation of microtopographic heterogeneity during restoration efforts has been largely absent (Stolt et al 2000), perhaps due in part to the significant costs incurred in contouring large areas. However, incorporating microtopography into wetland restorations may create the edaphic and hydrologic variations essential for the colonization, establishment, and survival of a diverse community (Beatty 1984; Todd et al 2000), thereby accelerating the development of wetland species composition and function (Bruland & Richardson 2005).…”