Academic journal article The American Midland Naturalist

A Comparison of Germination and Early Growth of Four Early Successional Tree Species of the Southeastern United States in Different Soil and Water Regimes

Academic journal article The American Midland Naturalist

A Comparison of Germination and Early Growth of Four Early Successional Tree Species of the Southeastern United States in Different Soil and Water Regimes

Article excerpt

ABSTRACT.-

To learn more about the basic biology of exotic relative to native tree species we conducted a greenhouse experiment comparing the germination and early seedling growth of four early successional tree species found in the southeastern United States: two exotics (Ailanthus altissima and Paulownia tomentosa) and two natives (Liquidambar styraciflua and Platanus occidentalis). Five soil types and three water regimes were used for the experiment. Liquidambar and Platanus, the native species, germinated significantly more quickly and were more sensitive to soil type than were the exotics, Ailanthus and Paulownia. Platanus grew tallest, and along with Paulownia, accumulated the greatest total biomass. Ailanthus alone exhibited a high root/shoot ratio in all soil types. In addition, species differed in their response to soil types for multiple growth traits. The results suggest that native tree species could be used to help retard the establishment of invasive tree species on bare soil.

INTRODUCTION

Because invasive exotics are often extremely difficult and expensive to control, it is important to identify efficient strategies for limiting their spread (Byers et al, 2002; Buckley et al, 2004). Studies have suggested that competition or predation from native species may slow invasive species (Newsome and Nobel, 1986; Simmons, 2005; Mandryk and Wein, 2006) , which suggests diat management programs might effectively use natives to control invasives. The value of this strategy, however, will depend on the basic biology of each species being used, e.g., conditions that favor the establishment of the invasive relative to the native, interactions between the invasive and exotic.

Because we have found only one study that compares the germination and early establishment of invasive and exotic trees that overlap in range (Butterfield et al, 2004), we conducted an experiment that compared the germination and early seedling growth of four tree species found in the southeastern United States: two native early successional tree species, Liquidambar styraciflua L. and Platanus ocadentalis L., and two exotic species, Ailanthus altissima (Mill.) Swingle and Paulownia tomentosa (Thumb.) Sieb. & Zeec. Ex Steud. Hereafter, we refer to the species by the genus only. Ailanthus is a USDA Forest Service "category 1" invasive (Owen, 2002), meaning it poses significant threats to natural ecosystems and commercial forestry practices (Miller, 1998). Paulownia has not yet been categorized, however, it is becoming a more prominent member of the local flora. Botii exotics frequently establish on bare soil in disturbed areas, such as on construction sites, railroad rights of way and roadsides. We compared the germination and seedling growth of the four species on five soil types and under three water treatments. The goals were to determine: (1) if germination and early growth differed between these four species and (2) if soil type and water regime affected germination and growth. Two otiier species were initially included in the study, Albizia julibrissin Durraz., an exotic and Liriodendron tulipifera L., a native, but were subsequently dropped from the experiment due to poor germination.

METHODS

Seed and soil collections.-Seeds of Ailanthus, Pauloumia and Platanus were collected from three - many trees along roadsides in North Carolina in fall 2004. Liquidambar seeds were collected from two North Carolina Forest Service stands. All seeds were cold/dry stratified at 12 C for 8 mo as suggested by Bonner (1974 a, b), Bonner and Burton (1974), and Little (1974). For each species, seeds from all sources were mixed before sowing.

Samples of five soil types were collected from the piedmont and coastal plain regions of North Carolina. The sandy loam coastal plain forested (CF) and clayey piedmont forested (PF) soils were collected from undisturbed (>50 y old) forests. Both soils had well developed O and A horizons. …

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