Differences in plant function in phosphorus- and nitrogen-limited mangrove ecosystems.
Differences in plant function in phosphorus- and nitrogen-limited mangrove ecosystems.
复制标题
磷和氮限制红树林生态系统中植物功能的差异。
作者：
C. Lovelock;I. Feller;M. Ball;Bettina M. J. Engelbrecht;Mei Ling Ewe
红树林生态系统可能是氮（N）或磷（P）有限的，因此容易受到营养物污染。无论是氮或磷的营养富集可能会对生态系统产生不同的影响，因为在氮或磷限制设置这些营养素的植物生理反应的根本差异。使用一个共同的红树林物种，白骨壤，在网站上的增长是无论是N或P限制，我们调查了不同的生理反应，N和P限制和施肥。我们测试的假设，水的吸收和运输，水力结构，是主要的过程限制生产力在P-有限的网站，但这是不是在N-有限的网站的情况。我们发现，植物在磷缺乏网站有较低的叶水势，气孔导度和光合碳同化速率，和较少的传导木质部，比那些在N限制网站。这些差异大大减少与磷施肥在磷有限的网站。相比之下，施肥与N在N-有限的网站有光合或水力性状的影响不大。我们的结论是，生长在N-和P-有限的网站差异影响红树林的水力途径。植物经历磷限制似乎是水分不足，并经历更明显的结构和功能的变化，缓解营养不足比那些在N-有限的生态系统。
Mangrove ecosystems can be either nitrogen (N) or phosphorus (P) limited and are therefore vulnerable to nutrient pollution. Nutrient enrichment with either N or P may have differing effects on ecosystems because of underlying differences in plant physiological responses to these nutrients in either N- or P-limited settings. Using a common mangrove species, Avicennia germinans, in sites where growth was either N or P limited, we investigated differing physiological responses to N and P limitation and fertilization. We tested the hypothesis that water uptake and transport, and hydraulic architecture, were the main processes limiting productivity at the P-limited site, but that this was not the case at the N-limited site. We found that plants at the P-deficient site had lower leaf water potential, stomatal conductance and photosynthetic carbon-assimilation rates, and less conductive xylem, than those at the N-limited site. These differences were greatly reduced with P fertilization at the P-limited site. By contrast, fertilization with N at the N-limited site had little effect on either photosynthetic or hydraulic traits. We conclude that growth in N- and P-limited sites differentially affect the hydraulic pathways of mangroves. Plants experiencing P limitation appear to be water deficient and undergo more pronounced changes in structure and function with relief of nutrient deficiency than those in N-limited ecosystems.