228 Basic principles for molding land mosaics
Figure 9.1Tidal wetland and river spanned by multilane highway bridge which
facilitates wildlife and floodwater passage. Note: habitat heterogeneity in the
floodplain; small meandering channel on mudflat; picnic recreation area on left;
and continuous woody vegetation corridor along field that reduces agricultural
runoff and enhances wildlife movement. Dover/Smyrna, Delaware, USA. Photo
courtesy of US Federal Highway Administration.(C) Plants in wetlands.Because the water table level is close to the irregular
soil surface in a wetland, considerable spatial microheterogeneity and
temporal change in water conditions are the norm, often producing a
high diversity and biomass of adaptable, seasonally changing species.
(D) Wetlandcomplexes.Aconnected cluster or complex of wetlands normally
provides the highest wetland biodiversity and stability.
(E) Ephemeral ponds.Ephemeral ponds (or vernal pools) which dry out for a
period most years often contain a concentration of both rare plants that
thrive with alternating inundation and dry soil, and rare animals which
either burrow deeply into the soil during dry periods, or seasonally
migrate some distancefromandtothepond.
(F) Wetland surroundings.Natural vegetation surrounding a wetland or
ephemeral pond reduces sediment and other pollutant inputs, and is