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Ecology of Turfgrass Weeds

2012; Linguagem: Inglês

10.2134/turfweedsandtheircontrol1994.acsesspublicatiturfweedsandthe29x

2691-2341

T. L. Watschke, R. E. Engel,

Botany, Ecology, and Taxonomy Studies

Ecology is the study of the reciprocal relations between organisms and their environment. In Principles of Plant and Animal Pest Control (2) it is stated that weeds possess many growth characteristics and adaptations that enable them to exploit successfully the numerous ecological niches left unoccupied, exposed, or only partially filled by crop cultures. Interactions among turfgrasses, their management, and the environment are complex and dynamic with any ecological discussion concerning turfgrass communities strongly influenced by these interactions. Environments are dictated largely by climate, edaphic, and geographic factors; however, unlike naturally occurring climax vegetation, turfgrasses persist only in settings managed by humans. Human input is an intrinsic part of the turfgrass ecosystem. Without being managed by humans, most turfgrass species would succumb to the next plant succession. In early times, grass communities evolved when humans cleared forests and woody plant regrowth was prevented due to grazing by domesticated animals. These grasses were adapted to defoliation and persisted due to low growth habit. These forage species also had excellent regrowth capacity when defoliation pressure was removed. Turfgrass occurs in grass communities that are not grazed by animals (forage) or grown as annuals (grain production). Turfgrass communities exist as a result of management practices that manipulate many of their natural growth tendencies to increase their ecological fitness in the sward. Turfgrass management practices provide the foundation for turfgrass weed control strategies by minimizing opportunities for development of ecological niches necessary for weed encroachment. Since turfgrass management may be defined as the creation of environmental conditions that favor the competitive nature of the desired species over all others, weeds are excluded from consideration as a permanent component in most turfgrass ecosystems. Such a management definition places an important emphasis on the reciprocal relations between turfgrasses and their environment and is uniquely suited to encompass all aspects of weed control strategies. J.P. Grime (1) concluded that where the objective of turf management is to maintain a uniform monoculture, e.g., lawns, bowling greens, cricket patches, it is desirable to restrict the frequency of vegetation gaps to a minimum and to encourage the growth of grasses that produce a dense, rapidly-repairing, leaf canopy close to the ground surface. If the objective of turf management is to maintain a genetically diverse plant community, e.g., picnic areas, roadsides, parkland, nature reserves, it may be helpful to disturb the established vegetation by occasionally grazing, mowing, or harrowing in order to create gaps into which regeneration of the component species can take place. Coring or any other management practice, pest, or site use that causes voids in the turf stand are considered to be ecological trigger factors. Management of turf creates a holocoenotic environment that responds dramatically to a trigger factor (the ecological change resulting from the void will cause another site change, which will cause another, and so on). Therefore, in almost all instances, proper turfgrass management minimizes voids in the stand. Most of the time, well maintained turf should be dense enough to prevent any view of the soil surface. When conditions exist that necessitate core cultivation (compacting and low infiltration rates), timing of the coring must be precise enough so that the void created in the stand does not provide an opportunity for weed encroachment. Coring during the spring can stimulate summer annual emergence and fall coring can increase winter annual emergence. When coring cannot be done at more opportune times of the year, the use of preemergence herbicides following or in conjunction with the coring may be desirable. Within the context of the definition of turfgrass management, it is also important to provide turfgrass communities with the best combination of aesthetic quality and function. Such an integration occurs when there is concensus about the ecological purpose of the turfgrass area on which the management system is imposed. Usually, the purpose of the turfgrass community is to stabilize soil, provide a ground cover for the landscape, support recreational activity, reduce mud and dust, or improve overall aesthetic quality. Regardless of the purpose, quality turfgrass communities are the result of management strategies that best reflect the manager's ability to achieve compromise between aesthetics and function, manipulate plant competition through cultural practices, and correctly anticipate plant responses to changing environments.