Patches

Patches can have both positive and negative impacts on landscape. While forest patches between agricultural areas may prove beneficial for the ecological health, a landfill next to a sensitive wetland may have an adverse effect (Dramstad et al., 1996). Below, patches are categorized according to size, number, and location (Table 1).

Patch Size

Patch Number

Patch Location

Edge habitat and species Interior habitat and species

Habitat loss

Local extinction probability

Metapopulation

Extinction

Extinction

dynamics

Recolonization

Habitat diversity

Number of large patches

Patch selection for

Barrier to disturbance

Grouped patches as

conservation

Large patch benefits

habitat

Small patch benefits

1.1 Edges and boundaries

An edge is the outer section of a patch displaying different characteristics than the interior conditions of a patch, in terms of vertical and horizontal structure, width, and species composition and abundance. These differences constitute the edge effect and the edge acting as a transition zone between habitats presents opportunities for landscape planners to facilitate the achievement of an ecological goal. While the shapes of patches can be natural, i. e. due to their boundaries, they can as well be artificial, i. e. administrative, and thus, differ to a varying extent from natural edges (Dramstad et al., 1996). (Table 2).

Edge

Boundaries

Shapes of patches

• Edge structural diversity •

Natural and human edges •

Edge and interior species

• Edge width •

Straight and curvilinear •

Interaction with

• Administrative and natural

boundaries

surroundings

ecological boundary •

Hard and soft boundaries •

Ecologically "optimum"

• Edge as filter •

Edge curvilinearity and

patch shape

• Edge abruptness

width • Coves and lobes

Shape and orientation

Table 2. Edge, boundaries, and shapes of patches