Trees: a powerful geomorphic agent governing the landscape evolution of a subtropical wetland

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• 作者：Pamela L. Sullivan ; René M. Price ; Michael S. Ross ; Susana L. Stoffella…
• 刊名：Biogeochemistry
• 出版年：2016
• 出版时间：July 2016
• 年：2016
• 卷：128
• 期：3
• 页码：369-384
• 全文大小：1,736 KB
• 刊物类别：Earth and Environmental Science
• 刊物主题：Earth sciences
  Geochemistry
  Biochemistry
  Soil Science and Conservation
  Terrestrial Pollution
  
• 出版者：Springer Netherlands
• ISSN：1573-515X
• 卷排序：128

文摘

Transpiration-driven ion accumulation in soil has been invoked as a biological and physical feedback mechanism in wetlands that governs topographic differences by regulating soil accretion—with greater transpiration, ion accumulation and soil accretion occurring on tree islands as compared to the surrounding marsh. The strength of this mechanism is hypothesized to be controlled by the ratio of evapotranspiration (ET) to precipitation (P), where under greater ET to P conditions soil accretion may move from organic to mineral in nature. We tested the existence of this mechanism on tree islands in a subtropical wetland, determined if it supports mineral soil formation, and assessed its control on the development of nutrient resource contrasts (tree islands–marsh). To test our hypotheses, biannual measurements of groundwater, surface water and aboveground biomass were made from 2007 to 2012. Water samples were analyzed for water isotopes, concentrations of major ions, and total and dissolved nutrients on constructed tree islands. We found that tree transpiration led to the advective movement of water and associated ions toward the center of the tree islands, supporting CaCO₃ precipitation. CaCO₃ accretion on the tree islands was estimated at roughly 1 mm per decade, and represented 5 % of the total soil accretion since the islands’ planting. We also observed depletion in groundwater nutrient concentrations as tree biomass accumulated, indicative of tight nutrient cycling. This work provides direct evidence that trees can act as powerful geomorphic agents in wetland systems, forming mineral soils that support landscape heterogeneity on time scales of centuries to millennia.KeywordsWeatheringSoil formationTree islandsPlant-groundwater–surface water interactionsEverglades