STREAM PERIPHYTON AND INSECT HERBIVORES - AN EXPERIMENTAL-STUDY OF GRAZING BY A CADDISFLY POPULATION
STREAM PERIPHYTON AND INSECT HERBIVORES - AN EXPERIMENTAL-STUDY OF GRAZING BY A CADDISFLY POPULATION
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DOI：
10.2307/1937823
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发表时间：
1983-01-01
期刊：
影响因子：
4.8
通讯作者：
RESH, VH
中科院分区：
文献类型：
--
作者：
LAMBERTI, GA;RESH, VH
在美国加利福尼亚州北部的一条溪流中，通过实验研究了草食性石蛾 H. borealis 的放牧对底栖藻类和细菌的影响。大硫磺溪。通过将人造基质瓷砖抬高到溪底上方，可以有效排除Helicopsyche的幼虫，但不能排除其他食草昆虫。在 3 个重复实验中，Helicopsyche 放牧导致藻类（叶绿素 a，0.3-1.4 .mu.g/cm2）和细菌（0.3-0.7 × 108 个细胞/cm2）的数量较低，但藻类周转率较高（每单位叶绿素 a 释放的 O2 = 34 .mu.g .cntdot. .mu.g-1 .cntdot.h-1)。当排除幼虫时，存在较高量的藻类（叶绿素 a，8.1-15.1 .mu.g/cm2）和细菌（1.9-4.8 × 108 个细胞/cm2），但藻类周转率（每单位叶绿素 a 释放的 O2 = 7 .mu.g .cntdot. .mu.g-1 .cntdot. h-1）为更低。在第二组田间实验中，通过改变附生生物的现存作物来评估附生生物对食草动物密度和空间分布的影响。最近邻分析表明，Helicopsyche 幼虫聚集在具有比周围基质上的背景水平更高的直立作物的附生生物上。这些幼虫在吃草后将实验增强的附生生物减少到背景水平后变得随机分布。 Helicopsyche 的放牧形成了以硅藻为主的藻类群落，其农作物产量较低，由于周转率高，能够支持消费者的高生物量。如此高的生产率可能是因为放牧的附生植物对光和养分的竞争不如未放牧的附生植物激烈。
The effects of grazing by the herbivorous caddisfly H. borealis on benthic algae and bacteria were experimentally studied in a northern California [USA] stream. Big Sulphur Creek. By elevating artificial substrate tiles above the stream bottom, larvae of Helicopsyche, but not other herbivorous insects, were effectively excluded. In 3 replicate experiments, grazing by Helicopsyche resulted in low amounts of algae (as chlorophyll a, 0.3-1.4 .mu.g/cm2) and bacteria (0.3-0.7 .times. 108 cells/cm2) but a high algal turnover rate (O2 evolved per unit chlorophyll a = 34 .mu.g .cntdot. .mu.g-1 .cntdot. h-1). When larvae were excluded, higher amounts of algae (as chlorophyll a, 8.1-15.1 .mu.g/cm2) and bacteria (1.9-4.8 .times. 108 cells/cm2) were present, but the algal turnover rate (O2 evolved per unit chlorophyll a = 7 .mu.g .cntdot. .mu.g-1 .cntdot. h-1) was lower. In a 2nd set of field experiments, the effects of periphyton on the density and spatial distribution of grazers were assessed by varying the standing crop of periphyton. Nearest-neighbor analysis indicated that Helicopsyche larvae were aggregated on periphyton with higher standing crop than that which was present as background levels on surrounding substrate. Such larvae became randomly distributed after their grazing reduced the experimentally enhanced periphyton to the background levels. Helicopsyche''s grazing resulted in a diatom-dominated algal community with a low standing crop that, because of a high turnover rate, was able to support a high biomass of consumers. This high rate of production probably occurred because competiton for light and nutrients was less severe in the grazed than in the ungrazed periphyton.