Browsing by Author "Liu, Changxiang"

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    Effects of fire on vegetation in the Big Thicket of southeastern Texas, United States of America
    (1995) Liu, Changxiang; Harcombe, Paul A.
    This study shows that fire had a strong short-term effect on the small-sized individuals in the understory of two dry upland vegetation types, sandhill and upland pine. Large trees were less affected than saplings and small trees. The changes in these types were mainly structural rather than compositional. The influence of fire diminished toward the wet end of the vegetation gradient. Post-fire recruitment via resprouting and germination from seeds was rapid. The interaction of fire and vegetation type was apparent in the comparison of the two dry upland types with slope types. Simulation of fuel and fire provided additional, although not very strong, support for the existence of differences in fire behavior corresponding to an environmental gradient from dry upland forests to mesic and wet slope forests. Ordination using pre- and post-fire data suggests that fire had limited effects on current vegetation patterns and there was no indication that any present pre-fire type would be converted to another type. Furthermore, there were no clear convergent or divergent patterns in overall vegetation change; hence it was difficult to predict long-term changes. An eight-year record of vegetation change at a tornado damaged savanna site in Hickory Creek Unit demonstrates that the tornado had resulted in the succession of the vegetation toward a midslope forest, but two prescribed fires partially reversed such a trend. Phytolith analysis revealed that upland pine and some upperslope forests had abundant grass phytoliths. This indicates that these types had a grass component in the past under an open canopy which might have disappeared as a result of fire suppression, logging, and encroachment of shrubs and hardwoods.
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    Patterns of vegetation in fire-prone habitats, southeastern Texas, United States
    (1992) Liu, Changxiang; Harcombe, Paul A.
    Patterns of vegetation in fire-prone habitats were analyzed by ordination. The results showed that vegetation was highly related to soil texture, but was not obviously related to fire history. I concluded that either fire and soil effects are confounded or fire effects have been reduced by long-time fire suppression. Indicators of site productivity--height and volume increment of loblolly pine, and stand basal area--were weakly related to vegetation type, but not related to soil texture. The lack of a relationship between these indicators and soil texture suggests that site productivity may not be related simply to soil texture and that interactions with other species may obscure the response of loblolly pine to site productivity. The flammable portion of fine fuel was higher in dry types than in wet types which is consistent with the hypothesis that fire effects will be greater in dry types than in wet types.