Drewa Paul B, Peters Debra P C, Havstad Kris M
United States Department of Agriculture--Agricultural Research Service, Jornada Experimental Range, Las Cruces, NM, 88003, USA.
Oecologia. 2006 Nov;150(1):29-39. doi: 10.1007/s00442-006-0502-4. Epub 2006 Jul 29.
Relationships involving fire and perennial grasses are controversial in Chihuahuan Desert grasslands of southern New Mexico, USA. Research suggests that fire delays the resprouting of perennial grasses well after two growing seasons. However, such results are confounded by livestock grazing, soil erosion, and drought. Additionally, post-fire grass responses may depend on initial clone size. We evaluated the effects of fire, grazing, and clone size on Bouteloua eriopoda (black grama) in southern New Mexico grasslands. Four 2-ha plots were established in each of four sites. Fire and grazing were applied or not applied in 1999 such that four treatment combinations were assigned randomly to plots within each site. Within each plot, small (0-10 cm(2) basal area), medium (10-30 cm(2)), and large ( > 30 cm(2)) clones were initially mapped in five 0.91-m(2) quadrats where grass attributes and litter cover were evaluated before and at the end of two growing seasons following fire. Maximum fire temperature was also measured. At a population level, canopy and litter cover were each approximately 50% less in burned than unburned areas. However, compared to initial levels, canopy height had increased by 10% at the end of the study, regardless of fire. At a clonal level, basal cover reductions were attributed mostly to large clones that survived fire. Smaller clone densities had decreased by as much as 19% in burned compared to unburned areas, and fire reduced the basal cover of medium clones. Basal and canopy cover, recruitment, and clone basal area decreased with increased fire temperatures. Almost all responses were independent of grazing, and interactive effects of grazing and fire were not detected. Fire did not kill all perennial grass clones, regardless of size. However, rapid responses were likely influenced by above-average precipitation after fire. Future studies in desert grasslands should examine how perennial grass dynamics are affected by fire, precipitation patterns, and interactions with grazing.
在美国新墨西哥州南部的奇瓦瓦沙漠草原，涉及火与多年生草本植物的关系存在争议。研究表明，火灾会使多年生草本植物在两个生长季节后很久才重新发芽。然而，这些结果受到牲畜放牧、土壤侵蚀和干旱的干扰。此外，火灾后草本植物的反应可能取决于初始克隆大小。我们评估了火灾、放牧和克隆大小对新墨西哥州南部草原上的布氏草（黑格兰马草）的影响。在四个地点各设立了四个2公顷的样地。1999年对样地进行了火灾和放牧处理或不处理，使得四种处理组合被随机分配到每个地点的样地中。在每个样地内，在五个0.91平方米的样方中最初绘制了小（基部面积0 - 10平方厘米）、中（10 - 30平方厘米）和大（> 30平方厘米）克隆，在火灾后的两个生长季节开始前和结束时评估草本植物属性和凋落物覆盖情况。还测量了最高火灾温度。在种群水平上，与未燃烧区域相比，燃烧区域的冠层和凋落物覆盖分别减少了约50%。然而，与初始水平相比，无论是否发生火灾，研究结束时冠层高度都增加了10%。在克隆水平上，基部覆盖减少主要归因于在火灾中存活的大型克隆。与未燃烧区域相比，燃烧区域较小克隆的密度下降了多达19%，火灾减少了中型克隆的基部覆盖。基部和冠层覆盖、幼苗补充以及克隆基部面积随着火灾温度的升高而下降。几乎所有反应都与放牧无关，未检测到放牧和火灾的交互作用。无论大小，火灾并没有杀死所有多年生草本植物克隆。然而，快速反应可能受到火灾后高于平均水平的降水影响。未来在沙漠草原的研究应考察多年生草本植物动态如何受到火灾、降水模式以及与放牧相互作用的影响。
