Brockway Dale G, Gatewood Richard G, Paris Randi B
Southern Research Station, USDA Forest Service, 520 Devall Drive, Auburn, AL 36849, USA.
J Environ Manage. 2002 Jun;65(2):135-52. doi: 10.1006/jema.2002.0540.
Prior to Anglo-European settlement, fire was a major ecological process influencing the structure, composition and productivity of shortgrass prairie ecosystems on the Great Plains. However during the past 125 years, the frequency and extent of grassland fire has dramatically declined as a result of the systematic heavy grazing by large herds of domestic cattle and sheep which reduced the available levels of fine fuel and organized fire suppression efforts that succeeded in altering the natural fire regime. The greatly diminished role of recurrent fire in these ecosystems is thought to be responsible for ecologically adverse shifts in the composition, structure and diversity of these grasslands, leading specifically to the rise of ruderal species and invasion by less fire-tolerant species. The purpose of this study was to evaluate the ecological effects of fire season and frequency on the shortgrass prairie and to determine the means by which prescribed fire can best be restored in this ecosystem to provide the greatest benefit for numerous resource values. Plant cover, diversity, biomass and nutrient status, litter cover and soil chemistry were measured prior to and following fire treatments on a buffalograss-blue grama shortgrass prairie in northeastern New Mexico. Dormant-season fire was followed by increases in grass cover, forb cover, species richness and concentrations of foliar P, K, Ca, Mg and Mn. Growing-season fire produced declines in the cover of buffalograss, graminoids and forbs and increases in litter cover and levels of foliar P, K, Ca and Mn. Although no changes in soil chemistry were observed, both fire treatments caused decreases in herbaceous production, with standing biomass resulting from growing-season fire approximately 600 kg/ha and dormant-season fire approximately 1200 kg/ha, compared with controls approximately 1800 kg/ha. The initial findings of this long-term experiment suggest that dormant-season burning may be the preferable method for restoring fire in shortgrass prairie ecosystems where fire has been excluded for a prolonged time period.
在盎格鲁 - 欧洲人定居之前，火灾是影响大平原短草草原生态系统结构、组成和生产力的主要生态过程。然而在过去的125年里，由于大量家养牛羊的系统性重度放牧，减少了易燃细物的可利用水平，以及有组织的灭火努力成功改变了自然火灾规律，草原火灾的频率和范围急剧下降。人们认为，反复发生的火灾在这些生态系统中的作用大幅减弱，是导致这些草原在组成、结构和多样性方面出现生态不利变化的原因，具体表现为杂草物种的增加以及耐火性较差物种的入侵。本研究的目的是评估火灾季节和频率对短草草原的生态影响，并确定在该生态系统中能以最佳方式恢复规定火烧，从而为众多资源价值带来最大益处的方法。在新墨西哥州东北部一片野牛草 - 蓝格兰马短草草原上，在进行火灾处理之前和之后，测量了植被覆盖度、多样性、生物量和养分状况、凋落物覆盖度以及土壤化学性质。休眠季节火烧后，禾本科植物覆盖度、杂类草覆盖度、物种丰富度以及叶片中磷、钾、钙、镁和锰的浓度都有所增加。生长季节火烧导致野牛草、禾本科植物和杂类草的覆盖度下降，凋落物覆盖度增加，叶片中磷、钾、钙和锰的含量上升。尽管未观察到土壤化学性质的变化，但两种火灾处理都导致草本植物产量下降，生长季节火烧后的现存生物量约为600千克/公顷，休眠季节火烧后的现存生物量约为1200千克/公顷，而对照区约为1800千克/公顷。这项长期实验的初步结果表明，对于长时间没有火灾的短草草原生态系统，休眠季节火烧可能是恢复火灾的更优方法。
