Grace James B, Keeley Jon E
U.S. Geological Survey, National Wetlands Research Center, 700 Cajundome Boulevard, Lafayette, Louisiana 70506, USA.
Ecol Appl. 2006 Apr;16(2):503-14. doi: 10.1890/1051-0761(2006)016[0503:asemao]2.0.co;2.
This study investigates patterns of plant diversity following wildfires in fire-prone shrublands of California, seeks to understand those patterns in terms of both local and landscape factors, and considers the implications for fire management. Ninety study sites were established following extensive wildfires in 1993, and 1000-m(2) plots were used to sample a variety of parameters. Data on community responses were collected for five years following fire. Structural equation modeling (SEM) was used to relate plant species richness to plant abundance, fire severity, abiotic conditions, within-plot heterogeneity, stand age, and position in the landscape. Temporal dynamics of average richness response was also modeled. Richness was highest in the first year following fire, indicating postfire enhancement of diversity. A general decline in richness over time was detected, with year-to-year variation attributable to annual variations in precipitation. Peak richness in the landscape was found where (1) plant abundance was moderately high, (2) within-plot heterogeneity was high, (3) soils were moderately low in nitrogen, high in sand content, and with high rock cover, (4) fire severity was low, and (5) stands were young prior to fire. Many of these characteristics were correlated with position in the landscape and associated conditions. We infer from the SEM results that postfire richness in this system is strongly influenced by local conditions and that these conditions are, in turn, predictably related to landscape-level conditions. For example, we observed that older stands of shrubs were characterized by more severe fires, which were associated with a low recovery of plant cover and low richness. These results may have implications for the use of prescribed fire in this system if these findings extrapolate to prescribed burns as we would expect.
本研究调查了加利福尼亚州火灾频发的灌木丛野火后的植物多样性模式，旨在从局部和景观因素两方面理解这些模式，并考虑其对火灾管理的影响。1993年在大面积野火之后设立了90个研究地点，使用1000平方米的样地对各种参数进行采样。火灾发生后的五年里收集了群落反应的数据。采用结构方程模型（SEM）将植物物种丰富度与植物丰度、火灾严重程度、非生物条件、样地内异质性、林分年龄和景观位置联系起来。还对平均丰富度反应的时间动态进行了建模。丰富度在火灾后的第一年最高，表明火灾后多样性得到增强。随着时间的推移，丰富度总体呈下降趋势，逐年变化归因于降水量的年际变化。在以下情况的景观中发现了丰富度峰值：（1）植物丰度适中偏高；（2）样地内异质性高；（3）土壤氮含量适中偏低、沙含量高且岩石覆盖率高；（4）火灾严重程度低；（5）火灾前林分较年轻。其中许多特征与景观位置和相关条件相关。我们从结构方程模型结果推断，该系统火灾后的丰富度受局部条件强烈影响，而这些条件又可预测地与景观水平条件相关。例如，我们观察到较老的灌木林分火灾更严重，这与植物覆盖恢复率低和丰富度低有关。如果这些发现如我们所预期的那样外推到规定火烧，那么这些结果可能对该系统中规定火烧的使用有影响。
