Root Phenology as a Factor of Competition among Grass Seedlings

Abstract

Highlight: Roots of plants express phenology significant to readily invade and become established on disturbed sites. competitive relationships, as do aerial parts. The following devel-Favorable root phenology is one of the adaptive strategies opmental stages of root phenology are proposed: (1) germination, allowing this superior competitive ability. (Perhaps the same (2) initial root growth, (3) rapid extension of root-soil contact, (4) dormancy, and (5) death. Examples of root phenological develop-principles apply to annual and perennial forbs.) The following ment in seedlings of three grass species are given to demonstrate discussion relates primarily to competition between seedlings of &ects on competition. annual and perennial grasses. Range plants universally compete with each other for the limited resources (light, water, nutrients, soil, air) of their ecosystem, Lacking human or biological interference, competition is a major factor in the determination of composition in a given plant community. Plants have many adaptations (morphological, anatomical, physiological, and phenological) suiting them to a place in the ecosystem. Among these is a characteristic phenology or response to seasonal change. Timing of the developmental stages of aerial plant parts (vegetative, reproductive, and dormant) has significant survival value in competition situations; timing of phenological development in roots, though less obvious, similarly has important survival value. A recent literature search failed to disclose any reference to studies of toot phenology, or to the development of theories of the function of variations in root phenology in plant competition. The author has conducted a line of research over the years, aimed at discovering the controlling factors in competition between seedlings of important native and introduced perennial and annual grasses of intermountain west rangelands. This work has led to investigations of rooting habits, including phenology, which have significance in understanding plant competition. Published results of seleL_ed experiments are recounted here in the development of conclusions principle of plant competition. regarding root phenology as a Stands of perennial grasses have a natural competitive advantqe over annual grasses. It is not necessary for them to begin ,T;~o seed following each aormant period. However, once mature plants are removed, and reestablishment from seed required; perennials are at a disadvantage. Seedlings of annuals Author is chairman and professor,

Suppression ofBromus tectorumL. by Established Perennial Grasses: Potential Mechanisms—Part One

“…Pathways by which B. tectorum facilitate its expansion are myriad and include phenotypic plasticity to new host environments [2], it increases the rates and sizes of wildfires, which fosters more invasion [3], rapid above-and below-ground growth rates [4,5], prolific seed production [6], landscape disturbance [7][8][9], and elevated atmospheric CO 2 [10,11].…”

Seed Bank Depletion: The Key to Long-Term Downy Brome ( Bromus tectorum L.) Management

“…Other researchers reported rooting depths of over 39 inches in root box studies (Harris 1967) and over 59 inches deep under field conditions (Hironaka 1961;Hulbert 1955). Harris (1977) indicated that downy brome roots grow 7 to 8 inches deep before lateral roots develop and lateral roots then tend to grow more downward than horizontally. Lateral root growth was reported to be 8 to 12 inches (Hulbert 1955).…”

“…Downy brome roots will continue to grow in very dry soils. Downy brome roots have poorly developed endodermis and suberized casparian strips to insulate against hot, dry soil and drought (Harris 1977). High air temperatures cause leaf water potentials to drop and roots cannot absorb soil moisture fast enough to keep plants from desiccating.…”

“…Harris (1967;1977) and Harris and Wilson (1970) evaluated competition between downy brome and bluebunch wheatgrass and between downy brome and crested wheatgrass (Agropyron cristatum). Downy brome stands from 0 to 5%, 45 to 50%, and 95 to 100% cover were labeled as sparse, moderate, and dense, respectively.…”

Rangelands, Volume 28, Number 5 (October 2006)

“…By 2005, 107 parcels totaling 295,700 acres had been incorporated into the Stewardship Trust. 7 The purpose of Colorado Stewardship Trust lands is to protect long-term productivity and sound stewardship instead of maximizing returns to the trusts. These lands are not guaranteed to remain as open space forever because an 80% majority vote of the Land Board commissioners can remove them from the Stewardship Trust rolls.…”