Vourlitis George L, Zorba Gypsi, Pasquini Sarah C, Mustard Robert
Department of Biological Sciences, California State University, San Marcos, CA 92096.
J Arid Environ. 2007 Jul;70(1):164-173. doi: 10.1016/j.jaridenv.2006.12.005.
Semi-arid shrublands of southern California, including chaparral and coastal sage, are found in widely varying elevation and microclimatic regimes and are subjected to disturbance such as fire and atmospheric N deposition that have the capacity to alter soil and litter C and N storage. Here we present a case study where soil and litter C and N were measured over 19 months in post-fire chaparral and mature coastal sage stands to assess whether differences in soil and litter C and N between these diverse shrublands could be attributed to differences in elevation, stand age, rainfall, and/or estimated N deposition exposure. Our results indicate that atmospheric N deposition exposure, either alone or in conjunction with other environmental variables (elevation, rainfall, and/or stand age), was the most frequent predictor of the spatial pattern in the soil and litter N and C variables observed. These results are consistent with those reported for high-elevation coniferous forests arrayed along an N deposition gradient in southern California, suggesting that N deposition may affect the soil N and C storage of semiarid shrublands and woodlands in a qualitatively similar manner.
南加州的半干旱灌木丛，包括矮橡树林和海岸鼠尾草，分布在海拔和微气候条件差异很大的地区，并且受到火灾和大气氮沉降等干扰，这些干扰有能力改变土壤和凋落物中的碳和氮储存。在这里，我们展示了一个案例研究，在火灾后的矮橡树林和成熟的海岸鼠尾草林中，对土壤和凋落物中的碳和氮进行了19个月的测量，以评估这些不同灌木丛之间土壤和凋落物中碳和氮的差异是否可归因于海拔、林分年龄、降雨量和/或估计的氮沉降暴露量的差异。我们的结果表明，大气氮沉降暴露，单独或与其他环境变量（海拔、降雨量和/或林分年龄）一起，是观察到的土壤和凋落物中氮和碳变量空间格局最常见的预测因子。这些结果与南加州沿氮沉降梯度分布的高海拔针叶林的报道结果一致，表明氮沉降可能以定性相似的方式影响半干旱灌木丛和林地的土壤氮和碳储存。
