Neill Christopher
Marine Biological Laboratory, The Ecosystems Center, 02543, Woods Hole, MA, USA.
Oecologia. 1993 Oct;95(4):499-505. doi: 10.1007/BF00317434.
Hydrologic regime is an important control of primary production in wetland ecosystems. I investigated the coupling of flooding, soil salinity and plant production in northern prairie marshes that experience shallow spring flooding. Field experiments compared whitetop (Scolochloa festucacea) marsh that was: (1) nonflooded, (2) flooded during spring with 25 cm water and (3) nonflooded but irrigated with 1 cm water · day. Pot culture experiments examined whitetop growth response to salinity treatments. The electrical conductivity of soil interstitial water (EC) at 15 cm depth was 4 to 8 dS· m lower in flooded marsh compared with nonflooded marsh during 2 years. Whitetop aboveground biomass in flooded marsh (937 g · m, year 1; 969 g · m, year 2) exceeded that of nonflooded marsh (117 g · m year 1; 475 g · m, year 2). Irrigated plots had lower EC and higher aboveground biomass than nonflooded marsh. In pot culture, EC of 4.3 dS · m (3 g · L NaCl) reduced total whitetop biomass by 29 to 44% and EC of 21.6 dS · m (15 g · L NaCl) reduced biomass by more than 75%. Large reductions of EC and increases of whitetop growth with irrigation indicated that plants responded to changes in soil salinity and not other potential environmental changes caused by inundation. The results suggest that spring flooding controls whitetop production by decreasing soil salinity during spring and by buffering surface soils against large increases of soil salinity after mid-summer water level declines. This mechanism can explain higher marsh plant production under more reducing flooded soil conditions and may be an important link between intermittent flooding and primary production in other wetland ecosystems.
水文状况是湿地生态系统初级生产力的重要控制因素。我研究了北方草原湿地中洪水、土壤盐分与植物生产力之间的耦合关系，这些湿地在春季会经历浅洪水。实地实验比较了白顶草（Scolochloa festucacea）湿地的三种情况：（1）非淹水状态；（2）春季淹水25厘米；（3）非淹水但每天灌溉1厘米水。盆栽实验研究了白顶草对盐分处理的生长反应。在两年时间里，与非淹水湿地相比，淹水湿地15厘米深度土壤间隙水的电导率（EC）低4至8 dS·m。淹水湿地的白顶草地上生物量（第一年937克·平方米；第二年969克·平方米）超过非淹水湿地（第一年117克·平方米；第二年475克·平方米）。灌溉地块的EC低于非淹水湿地，地上生物量高于非淹水湿地。在盆栽实验中，4.3 dS·m（3克·升氯化钠）的EC使白顶草总生物量减少29%至44%，21.6 dS·m（15克·升氯化钠）的EC使生物量减少超过75%。灌溉导致EC大幅降低和白顶草生长增加，表明植物对土壤盐分变化做出反应，而非淹没引起的其他潜在环境变化。结果表明，春季洪水通过在春季降低土壤盐分以及在夏中水位下降后缓冲表层土壤盐分大幅增加来控制白顶草产量。这种机制可以解释在更还原的淹水土壤条件下湿地植物产量更高的现象，并且可能是其他湿地生态系统中间歇性洪水与初级生产力之间的重要联系。
