Biometrics, Plant Sciences, Wageningen University, PO Box 100, 6700 AC Wageningen, The Netherlands.
Instituto de Ciencias Básicas, Universidad Nacional de Cuyo, Padre Contreras 1300, Parque Gral. San Martín, Mendoza M5502JMA, Argentina.
Sci Total Environ. 2016 Dec 15;573:1209-1216. doi: 10.1016/j.scitotenv.2016.03.139. Epub 2016 Apr 5.
Fire-prone Mediterranean shrublands may be seriously threatened by land degradation due to progressive opening of the vegetation cover driven by increasing drought and fire recurrence. However, information about the consequences of this opening process for critical ecosystem functions is scant. In this work, we studied the influence of vegetation amount, type, and spatial pattern in the variation of extracellular soil enzyme activity (acid phosphatase, β-glucosidase, and urease) in fire-prone shrublands in eastern Spain. Soil was sampled in vegetation-patch and open-interpatch microsites in 15 shrubland sites affected by large wildfires in 1991. On average, the activities of the three enzymes were 1.5 (β-glucosidase and urease) to 1.7 (acid phosphatase) times higher in soils under vegetation patches than in adjacent interpatches. In addition, phosphatase activity for both microsites significantly decreased with the fragmentation of the vegetation. This result was attributed to a lower influence of roots -the main source of acid phosphatase- in the bigger interpatches of the sites with lower patch cover, and to feedbacks between vegetation pattern, redistribution of resources, and soil quality during post-fire vegetation dynamics. Phosphatase activity was also 1.2 times higher in patches of resprouter plants than in patches of non-resprouters, probably due to the faster post-fire recovery and older age of resprouter patches in these fire-prone ecosystems. The influence on the studied enzymes of topographic and climatic factors acting at the landscape scale was insignificant. According to our results, variations in the cover, pattern, and composition of vegetation patches may have profound impacts on soil enzyme activity and associated nutrient cycling processes in fire-prone Mediterranean shrublands, particularly in those related to phosphorus.
易发生火灾的地中海灌木林地可能因植被覆盖的逐渐减少而受到严重威胁，这种减少是由干旱和火灾频发导致的。然而，关于这种开放过程对关键生态系统功能的影响的信息却很少。在这项工作中，我们研究了植被数量、类型和空间格局对西班牙东部易发生火灾的灌木林地土壤胞外酶活性（酸性磷酸酶、β-葡萄糖苷酶和脲酶）变化的影响。在 1991 年遭受大面积野火影响的 15 个灌木林地中，我们在植被斑块和开放斑块微生境中采集了土壤样本。平均而言，三种酶的活性在植被斑块下的土壤中比相邻斑块中的土壤高 1.5（β-葡萄糖苷酶和脲酶）至 1.7（酸性磷酸酶）倍。此外，两种微生境的磷酸酶活性都随着植被的破碎化而显著降低。这一结果归因于在斑块覆盖率较低的地点，由于较大的斑块间根系（酸性磷酸酶的主要来源）的影响较小，以及植被格局、资源再分配和火灾后植被动态过程中的土壤质量之间的反馈作用。在易发生火灾的生态系统中，繁殖体植物的斑块中的磷酸酶活性比非繁殖体植物的斑块中的磷酸酶活性高 1.2 倍，这可能是由于繁殖体植物在火灾后恢复较快，且年龄较大。在景观尺度上作用的地形和气候因素对研究酶的影响不大。根据我们的研究结果，植被斑块的覆盖度、格局和组成的变化可能对易发生火灾的地中海灌木林地土壤酶活性和相关养分循环过程产生深远影响，特别是与磷有关的过程。
