Intensity of Agricultural Practices and Effects on Adjacent Habitats

Abstract

In intensive agricultural areas small woodlots and woody hedgerows constitute the only remnant of natural forested habitats. Because they are reduced in size and are surrounded by farmlands, remnant habitats may be impacted by several abiotic factors. The conservation value of these habitats, however, cannot be fully ascertained while plant species richness and composition remain unknown. We describe the vegetation composition of woodlot edges and hedgerows associated with agricultural fields of different farming intensities. We inventoried thirteen woodlot edges and hedgerows in each of three types of farming systems characterized mainly by different frequency of tillage and by different levels of herbicide and fertilizer use. The number and percentage cover of species present did not differ greatly between farming regimes whereas the species composition varied considerably. In habitats adjacent to intensively farmed fields, we found more short‐lived grassy‐type plants that were largely of introduced origin and of weedy propensity. Conversely, more species typical of the maple‐tree association were found in habitats abutting less intensively managed fields. Species composition and abundance also differed with distances into the woodlots and hedgerows. These effects were more noticeable in woodlot edges than in hedgerows. We discuss the results in relation to their conservation as well as their agronomic implications. We suggest that a buffer strip at the edge of cultivated fields may be sufficient for the protection of native plants in woodlots (and probably of other wildlife) and, to a lesser extent, of hedgerows. Furthermore, buffer strips may reduce weed interaction between crop and non‐crop habitats.

Comparing weed composition in natural and planted hedgerows and in herbaceous field margins adjacent to crop fields

“…Consequently, many of the remaining natural hedgerows may have been degraded due to herbicide, but also by fertiliser drift (Rew et al 1992;Boutin and Jobin 1998) and other management practices, e.g., selective wood removal by farmers, ploughing too close to hedgerow edges. Gaps within these hedgerows may also originate from infrequent natural events, such as occasional tree falling, fire, ice storms, etc.…”

“…In Britain, studies have indicated that weed spread from hedgerows/field margins into croplands is limited to a few annual species such as brome (Bromus sterilis L.) and cleavers (Galium aparine L.) (Marshall and Smith 1987;Smith et al 1999). Boutin and Jobin (1998) also indicated that the more a field was managed intensively, the greater was the potential for adjacent habitats (woodlots or hedgerows impacted by misplacement of agrochemicals) to become sources of weeds (see also Boatman 1988). It was even suggested that, ultimately, croplands were probably the source of weeds that colonised gaps created by disturbances in adjacent non-crop habitats.…”

“…The problem of weed invasion in croplands from adjacent habitats has only been cursorily addressed in eastern Canada (Jobin et al 1997;Boutin and Jobin 1998). The objective of this study was to investigate weed abundance patterns in natural and planted woody hedgerows and in herbaceous field margins, and more specifically, to assess whether or not the various types of hedgerows and field margins act as reservoirs of weeds for invasion into fields.…”

When Landscaping Goes Bad: The Incipient Invasion of Mahonia bealei in the Southeastern United States

“…Woodlots are characterized as forest islands within an urban matrix, and often represent the only semi-natural areas remaining in suburban areas (Levenson 1981;Boutin and Jobin 1998). Forest ''islands'' and fragments may be more easily invaded than continuous forests (Fine 2002).…”

“…A small patch of forest (4 ha) may be sufficient to sustain native, forest-interior plants (Usher 1987). Therefore, woodlots represent critical conservation areas for native plants (Boutin and Jobin 1998). Additionally, woodlots represent important habitat for wildlife in urban areas (Matthiae and Stearns 1981).…”