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首页> 外文期刊>Estuarine Coastal and Shelf Science >Relationship between land-use in the agro-forestry system of les Landes, nitrogen loading to and risk of macro-algal blooming in the Bassin d'Arcachon coastal lagoon (SW France)
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Relationship between land-use in the agro-forestry system of les Landes, nitrogen loading to and risk of macro-algal blooming in the Bassin d'Arcachon coastal lagoon (SW France)

机译：莱斯·兰德斯农林业系统中的土地利用，氮素含量与阿尔卡雄盆地（Bassin d'Arcachon）沿海泻湖中大型藻类开花风险之间的关系（法国西南部）

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Nitrogen loading to the Bassin d'Arcachon coastal lagoon (SW France) was evaluated by studying land-use and nitrogen output in its 3001 km~2 catchment. At present, the catchment is dominated by forestry (79%), while intensive agriculture occupies 9% of the surface. The N-output of two hydrological subunits, i.e. the Tagon subunit dominated by pine forestry and the Arriou II subunit comprising both forestry and intensive agriculture, were monitored for a seven year period (1996-2002). From these observations it was calculated that forestry contributes on average 1.6 kg total N ha~(-1) yr~(-1), which is dominated by organic nitrogen (DON + PON are 70% of N). On an areal basis, intensive agriculture contributes 26 times more than forestry, i.e. 41.6 kg total N ha~(-1) yr~(-1), which is mainly in the form of nitrate (65% of N). These data were upscaled to the catchment and the upscaling was validated by comparison to gauged nitrogen throughputs for the catchment of the Leyre river that is the major tributary to the system. Taking into account the other known N sources and the interannual variability in the catchment it was estimated that nitrogen loading to the lagoon was on average 90 kg ha~(-1) yr~(-1) (range from 54 to 126 kg ha~(-1) yr~(-1)). The sandy soils of the catchment have a clear potential for denitrification, but anoxic conditions (waterlogged) and input of organic matter to fuel this process are required. Currently, agricultural practices and spatial planning do not make use of this potential. Nitrogen loading in the Bassin d'Arcachon is reflected by 10-40 μM nitrate concentrations in winter, which became depleted during spring as a result of uptake by vegetation. Short-term uptake experiments showed that the macroalga Monostroma obscurum is well adapted to temperatures between 10 to 20℃ and competitive with respect to the seagrass Zostera noltii when the nitrate concentrations are above 10 μM. Spring conditions with high nitrate and high insolation are therefore favourable for M. obscurum and this species presents a high risk for algal blooming. In contrast, the macroalga Enteromorpha clathrata well adapted to summertime temperatures around 25℃, forms occasionally blooms in the lagoon. This phenomenon is limited due to the low DIN concentrations in summer.
机译：通过研究其3001 km〜2集水区的土地利用和氮输出，评估了Bassin d'Arcachon沿海泻湖（法国西南）的氮负荷。目前，流域以林业为主（占79％），而集约化农业占地表的9％。监测了七个水文亚基（即以松林为主的塔贡亚基和包括林业和集约农业的Arriou II亚基）的氮输出，为期7年（1996-2002年）。从这些观察结果可以计算出，林业平均贡献了总计1.6 kg的总N ha〜（-1）yr〜（-1），这主要由有机氮（DON + PON占N的70％）决定。从面积上看，集约化农业的贡献是林业的26倍，即总N ha〜（-1）yr〜（-1）达到41.6公斤，主要以硝酸盐的形式（占N的65％）。这些数据被放大到集水区，并且通过与作为系统主要支流的莱尔河集水区的标定氮流量进行比较来验证了放大的规模。考虑到其他已知的氮源和流域的年际变化，估计泻湖的氮负荷平均为90 kg ha〜（-1）yr〜（-1）（范围从54到126 kg ha〜 （-1）yr〜（-1））。流域的沙质土壤具有明显的反硝化潜力，但是需要缺氧条件（浸水）和有机物以补充该过程的燃料。当前，农业实践和空间规划并未利用这一潜力。冬季，硝酸盐浓度为10-40μM，这反映了阿尔卡雄河（Bassin d'Arcachon）中的氮负荷，由于植物的吸收，硝酸盐氮在春季逐渐枯竭。短期吸收实验表明，暗纹大型藻Monostroma obscurum非常适合10至20℃的温度，并且当硝酸盐浓度高于10μM时，与海藻Zostera noltii有竞争性。因此，硝酸盐含量高和日照强度高的春季条件对黑毛霉菌是有利的，该物种存在藻华大量繁殖的危险。相比之下，大型藻类Enteromorpha clathrata非常适合夏季温度在25℃左右，偶尔会在泻湖中绽放。由于夏季的DIN浓度较低，因此这种现象受到限制。

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