Effects of riparian vegetation removal on nutrient retention in a Mediterranean stream
Effects of riparian vegetation removal on nutrient retention in a Mediterranean stream
复制标题
河岸植被去除对地中海溪流养分保留的影响
DOI：
10.2307/1468120
复制
发表时间：
2000
影响因子：
--
通讯作者：
S. Sabater
中科院分区：
文献类型：
--
作者：
F. Sabater;A. Butturini;E. Martí;I. Muñoz;A. Romani;J. Wray;S. Sabater
在西班牙东北部的地中海森林河流里埃拉梅捷（Riera Major），我们通过比较砍伐和未砍伐河段的NH4-N和PO4-P吸收长度，研究了河岸植被去除对藻类动态和河流养分保留效率的影响。1995年6月至9月，我们在200 m的土壤中进行了6次短期添加N（以NH4Cl形式）和P（以Na2HPO4形式），以测定养分吸收长度。研究地点从河岸树木的冠层覆盖度上划分为2个明显的河段：前100 m完全被砍伐（即被砍伐河段），其余100 m完好无损（即阴影河段）。在我们取样之前的冬天，树木被从被砍伐的河段的河岸上移走。遮荫河段河岸植被以桤木（Alnus glutinosa）为主。该研究是在夏季和秋季进行的，由于森林冠层条件的不同，两个河段之间的光可用性差异最大。采伐河段的水藻生物量和水藻覆盖河面百分比均高于遮荫河段，说明采伐对水藻有刺激作用。总体而言，与遮荫河段相比，砍伐河段的养分保持效率更高（即吸收长度更短），特别是PO4-P。尽管测井后PO4-P的保留效率比NH4-N的保留效率提高得更大，但两个研究区NH4-N的保留效率都高于PO4-P。两个研究河段的PO4-P传质系数均与初级产量相关，表明藻类活动在控制该河段PO4-P动态中起重要作用。相比之下，NH4-N传质系数仅与被淹河段的藻类盖度%呈正相关，与阴影河段的任何藻类相关参数均不相关。缺乏与藻类生产的相关性表明，除了藻类活动之外的机制（即微生物异养过程或非生物机制）也可能影响该流中的NH4-N保留。总体而言，本研究表明，在阴凉的小溪流中，伐木干扰可能会改变溪流内的生态特征，从而导致溪流营养物质保持效率的变化。此外，河道与邻近河岸带紧密联系的改变可能直接或间接影响河流生态系统功能的生物地球化学过程。
We examined the effects of riparian vegetation removal on algal dynamics and stream nutrient retention efficiency by comparing NH4-N and PO4-P uptake lengths from a logged and an unlogged reach in Riera Major, a forested Mediterranean stream in northeastern Spain. From June to September 1995, we executed 6 short-term additions of N (as NH4Cl) and P (as Na2HPO4) in a 200-m section to measure nutrient uptake lengths. The study site included 2 clearly differentiated reaches in terms of canopy cover by riparian trees: the first 100 m were completely logged (i.e., the logged reach) and the remaining 100 m were left intact (i.e., the shaded reach). Trees were removed from the banks of the logged reach in the winter previous to our sampling. In the shaded reach, riparian vegetation was dominated by alders (Alnus glutinosa). The study was conducted during summer and fall months when differences in light availability between the 2 reaches were greatest because of forest canopy conditions. Algal biomass and % of stream surface covered by algae were higher in the logged than in the shaded reach, indicating that logging had a stimulatory effect on algae in the stream. Overall, nutrient retention efficiency was higher (i.e., shorter uptake lengths) in the logged than in the shaded reach, especially for PO4-P. Despite a greater increase in PO4-P retention efficiency relative to that of NH4-N following logging, retention efficiency for NH4-N was higher than for PO4-P in both study reaches. The PO4-P mass-transfer coefficient was correlated with primary production in both study reaches, indicating that algal activity plays an important role in controlling PO4-P dynamics in this stream. In contrast, the NH4-N mass-transfer coefficient showed a positive relationship only with % of algal coverage in the logged reach, and was not correlated with any algal-related parameter in the shaded reach. The lack of correlation with algal production suggests that mechanisms other than algal activity (i.e., microbial heterotrophic processes or abiotic mechanisms) may also influence NH4-N retention in this stream. Overall, this study shows that logging disturbances in small shaded streams may alter in-stream ecological features that lead to changes in stream nutrient retention efficiency. Moreover, it emphasizes that alteration of the tight linkage between the stream channel and the adjacent riparian zone may directly and indirectly impact biogeochemical processes with implications for stream ecosystem functioning.