Environmental Engineering Reference
In-Depth Information
Northern fence lizards (
Sceloporus undulatus
) that may themselves be benefi cial in
glade restoration. Because
Sceloporus
consume herbivores such as grasshoppers, Van
Zandt et al. (2005) hypothesized that the presence of the lizards in and around
brush piles might result in a trophic cascade, reducing herbivore damage to native
plants. Surveys of six Missouri glades showed that lizard activity occurred mainly
close to habitat structures, where they reduced grasshopper abundance by 75% and
plant damage to several glade plant species by over 66% (Figure 8.11). Future glade
restoration can benefi t by taking into account the top-down effects of predators on
grazers in this glade food web.
8.3
Managing
succession for
harvesting
In contrast to restoration managers who look for ways to help successions run their
course, farmers and gardeners work hard to fi ght succession - by planting desired
species and weeding out unwanted competitors. In their attempt to maintain the
characteristics of an early-successional stage - growing a productive annual grass -
arable farmers are forced to resist the natural succession to herbaceous perennials,
and beyond, to shrubs and trees. This is a never-ending battle. In other cultures,
though, agricultural 'gardening' poses fewer problems in the way that succession is
confronted (Section 8.3.1). Others use controlled burning to create a successional
mosaic of benefi t to hunters (Section 8.3.2).
8.3.1
Benzoin
'gardening' in
Sumatra
Benzoin is an aromatic resin, used for fl avoring, incense and medicinal products,
which is tapped from the bark of tropical trees in the genus
Styrax
. This has been
going on for centuries and benzoin still provides a signifi cant income to many
Fig. 8.11
(a) Lizard
activity in Ozark glades
declines with distance
from structures such as
brush piles, leading to
(b) reductions in their
prey, grazing grasshop-
pers, close to the
structures. (c)
Percentage herbivore
damage to the two forbs
Echinacea paradoxa
and
Rudbeckia missouriensis
(but not to the sedge
Carex
sp.) was lower
close to the structures,
a result mirrored (d) in
transplant experiments
involving the herb
Aster
oblongifolius
and the
grass
Schizachyrium
scoparium
. Standard
error bars are shown.
(After Van Zandt et al.,
2005.)
(a)
(b)
25
15
20
15
10
10
5
5
0
0
0
1
2
3
4
≤
1
8
16
Distance from structure (m)
Distance from structure (m)
(c)
(d)
50
50
Echinacea
Rudbeckia
Carex
Schizachyrium
Aster
40
40
30
30
20
20
10
10
0
0
≤
1
8
16
≤
1
8
16
Distance from structure (m)
Distance from structure (m)
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