Photosynthesis-nitrogen relations in Amazonian tree species
Photosynthesis-nitrogen relations in Amazonian tree species
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DOI：
10.1007/bf00317909
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发表时间：
1994-02
期刊：
影响因子：
2.7
通讯作者：
P. Reich;M. Walters;D. Ellsworth;C. Uhl
中科院分区：
文献类型：
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作者：
P. Reich;M. Walters;D. Ellsworth;C. Uhl
在物种之间，光合作用能力(Amax)通常与叶片含氮量(N)有关，但物种特有关系的变化还不是很清楚。为了解决这个问题，我们研究了邻近亚马逊群落中23种物种的Amax-N关系，这些物种受到氮(N)、磷(P)和/或其他矿物营养的不同限制。在3种晚演替林型(Tiera Firme、Caatinga和Bana)中各研究了5种，在干扰地(人工和早期次生演替Tiera Firme样地)上研究了8种。质量基础上表达的Amax与23个物种中的17个物种相关(p<；0.05)，而面积基础上的Amaxan与23个物种中的21个相关(p<；0.05)。对于干扰适应较早的演替物种，其Amax-N关系的斜率较大，而对较晚演替物种的截距较小。在质量基础上，7个早期次生演替物种的Amax-N斜率平均为≈15μmolCO2[gN]-1s-1，15个演替晚期物种的平均斜率为≈4μmolCO2[gN]-1s-1。受干扰地物种的叶寿命比演替后期物种短，比叶面积大。在所有23个物种中，聚集度-N质量关系的斜率与SLA(R2=0.001.70)正相关，与叶寿命(R2=0.78)和次生生态位负相关(R2=0.90)。因此，适应干扰的早期演替物种表现出一系列有利于资源获取和在其高资源更新生态位中快速生长的特征(叶片寿命短，SLA和Amax高，Amax-N斜率大)。Amax-N关系的意义和形式与三个演替后期群落的相对营养限制有关。在物种和群落水平上，N限制的Caatinga比P和N限制的Bana对N的依赖程度更高，而在P和Ca限制的Tiera Firme对草甸土的依赖程度最低，这三个群落基于质量的Amax-N斜率的差异反映了这种模式(分别为6.0molCO2[gN]-1s-1)。在所有23种植物中，估计的达到补偿所需的叶片数(净光合作用≈为零)与积累量斜率和暗呼吸速率呈正相关，与叶片寿命呈负相关。在Amax-N坡度上，物种间的差异与潜在的光合作用N利用效率和Amaxper单位叶N有很好的相关性。Amazxon N的依赖性和这种关系的形式在亚马逊物种和群落之间是不同的，这既与N、P和其他矿质养分的相对有效性一致，也与物种适应不同资源可获得性生境的内在生态生理特征相一致。
Among species, photosynthetic capacity (Amax) is usually related to leaf nitrogen content (N), but variation in the species-specific relationship is not well understood. To address this issue, we studied Amax-N relationships in 23 species in adjacent Amazonian communities differentially limited by nitrogen (N), phosphorus (P), and/or other mineral nutrients. Five species were studied in each of three late successional forest types (Tierra Firme, Caatinga and Bana) and eight species were studied on disturbed sites (cultivated and early secondary successional Tierra Firme plots). Amaxexpressed on a mass basis (Amass) was correlated (p<0.05) with Nmassin 17 of 23 species, and Amaxon an area basis (Aarea) was correlated (p<0.05) with Nareain 21 of 23 species. The slopes of Amax-N relationships were greater and intercepts lower for disturbance adapted early successional species than for late successional species. On a mass basis, the Amax-N slope averaged ≈15 μmol CO2[g N]-1s-1for 7 early secondary successional species and ≈4 μmol CO2[g N]-1s-1for 15 late successional species, respectively. Species from disturbed sites had shorter leaf life-span and greater specific leaf area (SLA) than late successional species. Across all 23 species, the slope of the Amass-Nmassrelationship was related (p<0.001) positively to SLA (r2=0.70) and negatively to leaf life-span (r2=0.78) and temporal niche during secondary succession (years since cutting-and-burning, r2=0.90). Thus, disturbance adapted early successional species display a set of traits (short leaf life-span, high SLA and Amaxand a steep slope of Amax-N) conducive to resource acquisition and rapid growth in their high resource regeneration niches. The significance and form of the Amax-N relationship were associated with the relative nutrient limitations in the three late successional communities. At species and community levels, Amaxwas more highly dependent on N in the N-limited Caatinga than in the P-and N-limited Bana and least in the P-and Ca-limited Tierra Firme on oxisol-and differences among these three communities in their massbased Amax-N slope reflects this pattern (6.0, 2.4, and 0.7 μmol CO2[g N]-1s-1, respectively). Among all 23 species, the estimated leaf Nmassneeded to reach compensation (net photosynthesis ≈ zero) was positively related to the Amass-Nmassslope and to dark respiration rates and negatively related to leaf life-span. Variation among species in the Amax-N slope was well correlated with potential photosynthetic N use efficiency, Amaxper unit leaf N. The dependence of Amaxon N and the form of the relationship vary among Amazonian species and communities, consistent with both relative availabilities of N, P, and other mineral nutrients, and with intrinsic ecophysiological characteristics of species adapted to habitats of varying resource availability.