Subtropical redberry juniper Juniperus pinchotii-mixed grasslands of west Texas (southern USA) are valued for livestock grazing and as wildlife habitat. However, in some areas juniper has become very dense. Mechanical control by root-ploughing is effective but expensive, and whilst chaining lowers juniper height, stems resprout and litter accumulates. Burning may be an economical and ecologically sound, alternative. This study assessed vegetation changes following spring burning and/or chaining of juniper-mixed grassland on the Masterson JY Ranch, King County.
Redberry juniper was the dominant woody species. Main grasses were sideoats grama Bouteloua curtipendula, hairy grama B. hirsuta, perennial threeawn species (Aristida wrightii, A. purpurea, A. longiseta), little bluestem Schizachyrium scoparium, silver bluestem Bothriochloa saccharoides, tall dropseed Sporobolus asper, rough tridens Tridens muticus, buffalograss Buchloe dactyloides, hairy tridens Erioneuron pilosum and fall witchgrass Leptoloma cognatum.
Treatments (randomized design, 2 replications) were: untreated (control); chained in 1974-75; and burning in March 1979 of 1974-75 chained areas. Burning were repeated in 1980, in addition to 1969 burn/chained (1974-75) and a 1969 burn/chained (1974-75)/1980 burn.
Along six randomly located (30.5 m) transects prior to burning in 1979 and 1980 and between May-September (1979-1981) the following were recorded: shrub cover and density, woody debris and bare ground cover, forb density; perennial grass standing crops and frequency. Response of juniper and three common shrubs (skunkbush Rhus aromatica, algerita Berberis trtfoliolata and littleleaf sumac Rhus microphylla)was determined from 10-100 randomly selected plants,
Livestock were returned in June after each burn (1 animal unit/20-22 ha, i.e. light to moderate stocking rate).
Rainfall from April-September 1979 was 18% above average, and from April-September 1980 was 32% below average.
Woody debris cover on chained areas was 17-25%, and less than 2% following burning; it was 4-6% on control and 11 year-old burned areas. Bare ground averaged 36% and 4% on control, 26% and 29% on chained, and 52% and 79% on burned areas during the 1979 and 1980 growing seasons, respectively.
In the first growing season following burning, shrub cover was less than 7% (doubling in the next year); in control and chained areas it ranged 21-31%. Importantly, juniper recovery was slower than other shrubs, burning also had the greatest impact on reduction of the least desirable grass (threeawn) and annual forb (common broomweed Xanthocephalum dracunculoides) species.
Compared to non-burned areas, perennial grass yields were similar or increased following burning in 1979 (wet year). In 1980 (dry year) yields were 50% less than no-burn chained areas, although only slightly less than controls. Burning in 1979 caused a great decrease in forb diversity (2.0 vs. 6.5-7.0 species/0.25 m²) and density (4.4 vs. 30.4-41.6 individuals/0.25 m²), but in May 1980 no significant differences were apparent across treatments.
Slow redberry juniper regrowth indicates that a relatively long fire interval (15 years) should be adequate reduce juniper cover. The authors suggest that burning should be confined to gentle-moderate slopes to minimize soil erosion risk due to bare ground exposure.
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