Patterns of CO2 exchange and productivity of the herbaceous vegetation and trees in a humid savanna in western Kenya

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• 作者：Dennis Otieno ; Joseph Ondier ; Sebastian Arnhold ; Daniel Okach…
• 关键词：Canopy conductance ; Canopy transpiration ; Gross primary production ; Hydraulic lift ; Humid savanna ; Soil water availability
• 刊名：Plant Ecology
• 出版年：2015
• 出版时间：October 2015
• 年：2015
• 卷：216
• 期：10
• 页码：1441-1456
• 全文大小：1,042 KB
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• 作者单位：Dennis Otieno (1)
  Joseph Ondier (2)
  Sebastian Arnhold (3) (4)
  Daniel Okach (1)
  Marianne Ruidisch (1)
  Bora Lee (1)
  Andreas Kolb (3)
  John Onyango (2)
  Bernd Huwe (3)
  
  1. Department of Plant Ecology, University of Bayreuth, 95440, Bayreuth, Germany
  2. Department of Botany, Maseno University, P.O. Box 333, Maseno, Kenya
  3. Department of Soil Physics, University of Bayreuth, 95447, Bayreuth, Germany
  4. Professorship of Ecological Services, University of Bayreuth, 95447, Bayreuth, Germany
  
• 刊物类别：Biomedical and Life Sciences
• 刊物主题：Life Sciences
  Plant Sciences
  
• 出版者：Springer Netherlands
• ISSN：1573-5052

文摘

Factors governing the dynamics between woody and herbaceous vegetation in the savanna are of ecological interest since they determine ecosystem productivity and stability. Field measurements were conducted in a humid savanna in the Lambwe valley, western Kenya, to compare CO2 exchange of the herbaceous vegetation and trees and its regulation. Soil characteristics and root distribution patterns under tree canopies and in the open locations dominated by the herbaceous vegetation were profiled in 1-m-deep soil layers. Soil water content (SWC) was measured at 30 cm depth both in the herbaceous vegetation and also under the tree canopies. The mean maximum monthly gross primary production (GPPmax) in the herbaceous vegetation was determined from chamber measurements, while daily GPP (GPPday) in both the grass and tree canopies was simulated using the PIXGRO model. The highest mean GPPmax in the herbaceous vegetation was 26.2 ± 3.7 μmol m-2 s-1 during April. Seasonal fluctuations of GPP in the herbaceous vegetation were explained by soil water availability (R 2 = 0.78) within the upper 30-cm soil profile. Seasonal GPPday fluctuations were larger (between 1 gC m-2 d-1 and 10 gC m-2 d-1) in the herbaceous vegetation compared to the trees, which fluctuated around 4.3 ± 0.3 gC m-2 d-1 throughout most of the measurement period. Daily tree canopy transpiration (Ec), canopy conductance (Gc), and GPPday were decoupled from SWC in the top 30-cm soil profile. On average, ecosystem GPPday (mean of tree and herbaceous vegetation) was 14.3 ± 1.2 gC m-2 d-1 during the wet period and 6.1 ± 0.9 gC m-2 d-1 during drought. Differences between the herbaceous and tree canopy responses were attributed to soil moisture availability.