Agriculture Reference
In-Depth Information
Aridity
+
Obligate
resprouters
Soil
fertility
-
ES1
+
Postfire
gaps
Fire
frequency
Genetic
turnover
+
+
Plant
flammability
Fire
intensity
Resprout
mortality
Drought
tolerance
Postfire
seeders
ES2
Seedling
survivorship
Climate
fluctuations
Obligate
resprouters
Obligate
seeders
Facultative
seeders
Fig. 9.5
Model of factors driving the evolution of postfire seeders and the further specialization
of obligate postfire seeders. Resprouting is hypothesized to be a trait contributing to persistence
on a wide variety of fire-prone landscapes. With increases in the predictability of high-
intensity fires capable of creating gaps for seedling recruitment, selection has delayed
reproduction to a single postfire pulse of seedling establishment. Further changes in fire
regimes that placed a greater premium on seedling recruitment and limited the value of
resprouting have led to some lineages abandoning the resprouting habit and evolution of the
obligate seeding life history. On rare occasions there apparently have been reversals in the
ES2 arrow with obligate seeders giving rise to facultative resprouters.
just an intensification of those responsible for the initial transition to postfire
seeding. However, other factors that affected resprouting mortality and more
rapid adaptation to changing climates by reduced generation time may have also
played a role.
There has been much interest in trying to sort out the environmental correlates
between resprouting and seeding. This question has been framed differently by
various authors and there is need for some clarification. Often it is placed in the
context of resprouting vs. seeding after fire. This has the potential for creating
some confusion since most woody species that only resprout after fire (postfire
obligate resprouters) also reproduce by seedlings during the inter-fire interval, so
in effect they are seeders, just not postfire seeders. Thus, there are two evolution-
ary transitions to be addressed:
