『Abstract
Little research has been done to study the combined fire-drought
impacts on the structure and functioning of Mediterranean fire-prone
ecosystems. In this study we have evaluated post-fire patterns
of soil phosphorus (P) availability and transformation rates in
a Mediterranean shrubland subjected to different drought treatments.
Precipitation was manipulated in various treatments to evaluate
the combined effects of fire and moisture in the soil. The following
treatments were included: long-term historical average precipitation,
or historical control (HC); moderate drought (MD, 25％ reduction
from HC); severe drought (SD, 45％ reduction from HC); and environmental
control without rainfall manipulation (EC). In late summer, these
plots were burned in order to evaluate the joint effects of drought
and fire. In order to compare burned and non-burned scenarios,
unburned plots were maintained without rainfall manipulation.
Post-fire soil samples, collected in the spring, were analyzed
for P fractions, P transformation rates (net solubilization and
immobilization, gross mineralization) and phosphatase activity.
Mid- to high-intensity fire caused a short-term increase of rapid-to-mid
turnover inorganic P pools in the soil, as well as a decline of
rapid turnover organic P pools (including microbial P) and acid
phosphatase activity. Fire also induced an overall rise in the
flux among P pools, including gross P mineralization, net microbial
immobilization and net geochemical solubilization, with the latter
being the most affected. Moreover, under drier than average conditions,
this ‘mineralizing’ effect of fire was partially (rapid turn over
inorganic P, total P flux among pools and net solubilisation)
or completely (net immobilization) offset. Thus, our results indicate
that a direct environment will limit the extent of post-fire peak
in soil P availability. This effect may act synergistically with
increased water stress to further inhibit vegetation recovery
after fire, possibility which is particularly relevant for fire-prone
Mediterranean shrublands where P limitation is widespread.
Keywords: P fractions; P transformation rates; Fire; Drought;
Climate change』
1. Introduction
2.Material and methods
2.1. Study area, experimental design and soil sampling
2.2. General physico-chemical soil properties
2.3. Soil phosphorus fractionation
2.4. Phosphorus transformation rates and phosphatase activity
2.5. Statistical analysis
3. Results
3.1. General soil properties
3.2. Soil phosphorus fractionation
3.3. Soil phosphorus transformation rates
4. Discussion
5. Conclusions
Acknowledgments
References