Season Length Indicators and Land‐Use Effects in Southeast Virginia Wet Flats

Abstract

temperature (Environmental Laboratory, 1987). Soil moisture, vegetation type, and land use were not taken The growing season concepts used by federal agencies in defining into account in the WDM, even though they all influence and regulating wetland hydrology ignore land use and rely on pubsoil temperature (Day and Megonigal, 1993; Cole and lished surrogate indicators. This study compared several growing sea-Brooks, 2000). The growing season defined in Soil Taxson indicators with measured air and soil temperature and hydrology data on three land-use types in the Great Dismal Swamp ecosystem onomy as "the portion of the year when soil temperaof Southeast Virginia to determine how accurate the indicators are tures are above biological zero in the upper part" (Soil on each land use. Water-table depths, 1-m air temperatures, and Survey Staff, 1975) was later adopted by the ACOE. soil temperature at 50-cm depths were measured for 18 mo at plots "Biological zero in the upper part" is assumed to occur representing forest, early successional field (field), and tilled (bare when soil temperatures stay at 5ЊC or warmer at the ground) land-use treatments at two study areas. Land use affected 50-cm depth (Environmental Laboratory, 1987). Because air and soil temperature through vegetation type and soil surface of the impracticality of measuring soil temperatures at properties, both of which are important for wetland restoration. Based 50 cm for every potential wetland site, the ACOE alon soil temperature at 50 cm, the growing season was continuous in lowed approximation of the growing season by the numforests but was interrupted in January for 1 to 7 d in some field and ber of frost-free days (Williams, 1992). The ACOE uses bare ground plots. Soil temperatures at 50 cm rose above biological zero (5؇C) 90 to 128 d before the published Ϫ2.2؇C growing season the 30-yr average dates between the first and last 0, started. The published Ϫ2.2؇C growing season was 28 to 88 d longer Ϫ2.2, or Ϫ4.4ЊC air temperature occurrence to calculate than the measured equivalent, and began after the water tables rose the number of days above that temperature at a freand stayed continuously in the upper 30 cm. A continuous growing quency of 5 in 10 yr, as published in NRCS soil survey season declaration is proposed for federal regulations in thermic wet report tables or downloaded from the Water and Cliflats on all land uses. Lengthening the growing season did not cause mate Data Center (NOAA-NCDC, 2003). However, the studied wetlands to fail the minimum federal wetland hydrology using air temperature data as an indicator for soil temrequirements for identification or delineation. perature has been questioned (Day and Megonigal, 1993; Cole and Brooks, 2000), and the lengths of alternative measured or published growing seasons have not been

Design and Implementation of a Simple Litter Catch-Basket System for Soil Studies

“…Litter fall and accumulation, which includes both leaf and twig material, is an important source of soil organic matter in forest soils (Finkl and Restrepo‐Coupe, 2007; Schaetzl and Anderson, 2005; Buol et al, 1997). Litter accumulation on the soil surface provides a food source to soil organisms (Moore et al, 2006; Anderson, 1975), supplies organic matter and plant nutrients to the underlying mineral horizons (Moore et al, 2006; Meier et al, 2005; Madeira and Ribeiro, 1995), moderates soil temperature fluctuations and evaporation rates (Burdt et al, 2005; Schaetzl and Anderson, 2005), and influences germination and establishment of plants (Brearley et al, 2003; Vellend et al, 2000). Because litter influences many soil properties and processes, the study of litter is of interest to soil scientists.…”