Community Ecology Processes, Models, and Applications

counteracts the effects of nutrient addition (De
Deynet al. 2004). These inoculation experiments in
mesocosms support exclusion experiments in the
field by Brown and Gange (1992) and Scha ̈dler
et al. (2004), who used selective biocides to elimi-
nate belowground and aboveground insects. Early
secondary succession slowed down when using soil
insecticides (Scha ̈dleret al. 2004) and accelerated
when using foliar insecticides (Brown and Gange
1992). Depending on the type of ecosystem, succes-
sion may slow down or speed up due to below- and
aboveground activities respectively (Davidson
1993; Kardolet al. 2006), but these results show
that ecosystem restoration is profoundly influenced
by above- and belowground biotic interactions and
not by changes in the abiotic environment alone.
Aboveground–belowground community interac-
tions enhance temporal variation in natural commu-
nities (Bardgettet al. 2005). For example, in an
extensively grazed pasture, cattle facilitated ant ac-
tivity, resulting in ant mounds with relatively path-
ogen-free soil, which was rapidly colonized by
pathogen-sensitive plant species (Blomqvistet al.
2000). The result was a spatio-temporal mosaic of
ant mounds and plant populations. Similarly, my-
corrhizal fungi in the plant roots can counteract
aboveground insect damage on plants (Gangeet al.
2003) and the individual effects of soil nematodes,
root-feeding wireworms and aboveground grass-
hoppers resulted in non-additive effects on plant
community composition (Van Ruijvenet al. 2005).

Enhanced exposure to aboveground and below-

ground invertebrates did not necessarily increase

plant community diversity. We know now that

aboveground and belowground biodiversity may,

at least to some extent, interact and also that second-

ary succession needs to be perceived from an above-

ground–belowground community perspective.

However, this area of research still needs more ex-

amples for convincing generalizations to be made.

7.3.3 Consequences for restoration and conservation

Biodiversity restoration and conservation clearly

require an aboveground–belowground approach.

Secondary succession is influenced by abiotic con-

ditions, as well as aboveground and belowground

community interactions. Probably, these abiotic

and biotic interactions act at different spatial and

temporal scales and there will be hierarchies in

controlling effects. For example, climate determines

the type of biome, soil type determines which veg-

etation types can occur, and aboveground verte-

brate herbivores determine vegetation structure

and patch structure in the landscape. At the smal-

lest spatial scale, aboveground invertebrate herbi-

vores, plant pathogens and plant–soil organism

interactions ultimately determine the composition

and dynamics of the plant community by influen-

cing plant competition, performance and abun-

dance (Fig. 7.2). Conservation and restoration

Climate

Soil type

Hydrology

Aboveground

biotic interactions

Belowground

biotic interactions

Continent

Region

Watershed-field

Landscape-field

Plot

Factor Scale

Figure 7.2Hierarchies in influences of plant community structure and composition. Climate influences plant
communities at continental scales, whereas belowground interactions influence plant communities at the smallest (plot,
<1m^2 ) scale.

APPLICATIONS OF COMMUNITY ECOLOGY APPROACHES 89