63
What kind of experiments would help predict what would happen with encroachment and succession of these woody legume species and communities in the future?
Measurement of gas-exchange rates at various levels of temperature, light, CO 2 , and
other resources for the various species of woody legumes and their associated species would be very helpful. The woody legumes should have high rates of gas
exchange at high light levels, which is characteristic of early successional species.
Species other than the woody legumes that are present in these communities should
also be examined, especially understory species and low-density species. These are
the species that could be community replacements and future community dominants
in the high temperature, high CO 2 environment of the future. Associated or understory species should have lower gas exchange rates at high light levels and relatively
high rates at low light levels, which is expected for late successional species. Carbon
uptake and possibly growth rates or relative growth rates of these species should be
examined at a variety of soil moisture levels, light levels, and elevated CO 2 , nitrogen, and temperature levels. Potential woody legume replacement species from dry,
more southern, or northern environments (depending on community location)
should be examined and evaluated as well.
In the future, soil organisms and soil processes should not be ignored, especially
nitrogen fi xation and the organisms associated with the woody legume roots. Soil
microbial communities will undoubtedly change as atmospheric CO 2 and temperature levels increase. Other atmospheric inputs will change as well, including nitrogen type and amount and other airborne chemicals. All these factors taken together
will probably modify soil biotic communities and alter soil biotic and abiotic reactions. One specifi c reaction of concern would be nitrogen fi xation, but there are
others including the various nitrogen cycle conversion reactions. These potential
changes will probably alter surface plant and animal communities, but how is
unknown at this time.
There is still considerable uncertainty with the predictions of global and regional
long-term climate changes. However, increases in extreme events are expected and
may be very important in the future, but their frequency and intensity are unclear.
Rainfall amounts, distribution, duration, and locations as well as water movement
and fl ow seem certain to change in the future, but direction and amount of these
changes, and the effects of altered climate, are further unknowns. Similar things
appear true for the other abiotic components of this system. As the abiotic components change, the biotic components will change as well.
These woody legume communities are changing over the short term, but their
future composition and structure is diffi cult to predict. They will continue to change,
and they will have a different species composition in the world of the future. It
appears that these woody legumes are encroaching into various warm season grasslands because of changing environmental conditions, which would include anthropogenic forces. The woody legume communities next appear to undergo successional
changes leading to new communities without the woody legumes. Some of these
changes are fairly well known, but some of the new communities will have relatively unknown structure and composition. These legume and other communities
are biologically, ecologically, and economically quite dynamic and very important.
9 The Future
What kind of experiments would help predict what would happen with encroachment and succession of these woody legume species and communities in the future?
Measurement of gas-exchange rates at various levels of temperature, light, CO 2 , and
other resources for the various species of woody legumes and their associated species would be very helpful. The woody legumes should have high rates of gas
exchange at high light levels, which is characteristic of early successional species.
Species other than the woody legumes that are present in these communities should
also be examined, especially understory species and low-density species. These are
the species that could be community replacements and future community dominants
in the high temperature, high CO 2 environment of the future. Associated or understory species should have lower gas exchange rates at high light levels and relatively
high rates at low light levels, which is expected for late successional species. Carbon
uptake and possibly growth rates or relative growth rates of these species should be
examined at a variety of soil moisture levels, light levels, and elevated CO 2 , nitrogen, and temperature levels. Potential woody legume replacement species from dry,
more southern, or northern environments (depending on community location)
should be examined and evaluated as well.
In the future, soil organisms and soil processes should not be ignored, especially
nitrogen fi xation and the organisms associated with the woody legume roots. Soil
microbial communities will undoubtedly change as atmospheric CO 2 and temperature levels increase. Other atmospheric inputs will change as well, including nitrogen type and amount and other airborne chemicals. All these factors taken together
will probably modify soil biotic communities and alter soil biotic and abiotic reactions. One specifi c reaction of concern would be nitrogen fi xation, but there are
others including the various nitrogen cycle conversion reactions. These potential
changes will probably alter surface plant and animal communities, but how is
unknown at this time.
There is still considerable uncertainty with the predictions of global and regional
long-term climate changes. However, increases in extreme events are expected and
may be very important in the future, but their frequency and intensity are unclear.
Rainfall amounts, distribution, duration, and locations as well as water movement
and fl ow seem certain to change in the future, but direction and amount of these
changes, and the effects of altered climate, are further unknowns. Similar things
appear true for the other abiotic components of this system. As the abiotic components change, the biotic components will change as well.
These woody legume communities are changing over the short term, but their
future composition and structure is diffi cult to predict. They will continue to change,
and they will have a different species composition in the world of the future. It
appears that these woody legumes are encroaching into various warm season grasslands because of changing environmental conditions, which would include anthropogenic forces. The woody legume communities next appear to undergo successional
changes leading to new communities without the woody legumes. Some of these
changes are fairly well known, but some of the new communities will have relatively unknown structure and composition. These legume and other communities
are biologically, ecologically, and economically quite dynamic and very important.
9 The Future