PHOTOSYNTHESIS-NITROGEN RELATIONS IN AMAZONIAN TREE SPECIES .2. VARIATION IN NITROGEN VIS-A-VIS SPECIFIC LEAF-AREA INFLUENCES MASS-BASED AND AREA-BASED EXPRESSIONS
PHOTOSYNTHESIS-NITROGEN RELATIONS IN AMAZONIAN TREE SPECIES .2. VARIATION IN NITROGEN VIS-A-VIS SPECIFIC LEAF-AREA INFLUENCES MASS-BASED AND AREA-BASED EXPRESSIONS
复制标题
DOI：
10.1007/bf00317910
复制
发表时间：
1994-02-01
期刊：
影响因子：
2.7
通讯作者：
WALTERS, MB
中科院分区：
文献类型：
--
作者：
REICH, PB;WALTERS, MB
研究了23种亚马逊树种叶片氮(N)、比叶面积（SLA）（叶片“厚度”或“密度”的反比指数）和光合能力（A(max)）之间的关系，以表征不同年龄和光照微环境下叶片自然种群中这些特性的尺度变化，并研究了物种内N和SLA的变化如何影响质量与面积基础上A(max)- N关系的表达。A(max)-N关系的斜率，即A的变化与N （μ mol CO2 gN-1 s-1）的变化，当这两个测量都以质量为基础而不是以面积为基础时，斜率始终更大，高达300%。这种关系的x截距（n补偿点）在质量基础上一般为正，而在面积基础上则不为正。在本文中，我们讨论了这些差异的原因和影响。12种植物叶片质量N（N（质量））与叶片表观密度呈显著线性关系（p < 0.05）， 23种回归曲线均为正斜率。在13种植物中，基于质量的A(max) （A（质量））与SLA呈正相关（p < 0.05）。这些模式反映了N（质量）和SLA随叶龄增加而同时下降。18种植物的叶面积N（N（面积））与叶片表观密度呈显著相关（p < 0.05）。在这种情况下，所有关系的斜率都为负。总的来说，在所有物种中都是一致的，随着叶龄和光照梯度的增加，SLA降低（叶片变得“更厚”），N（质量）也减少，但比例更慢，因此N（面积）增加。由于A（质量）对N（质量）的线性依赖和负4截距，因此，“厚”叶（低SLA）平均而言往往比“薄”叶具有更低的N（质量）和A（质量），但更高的N（面积）。A（质量）随N（面积）的增加而减小的趋势降低了A（面积）随Na（面积）增加的速率，导致A(max)-N关系在面积上的斜率低于质量基础上的斜率，其中17种中有16种两者均显著。对于唯一的物种例外（面积大于质量斜率），N（面积）的变化与N（质量）的变化有关，而与SLA无关，因此，这些数据也与这一解释一致。N、SLA和A（max）之间的关系解释了A（max）每N变化的变化率如何根据使用质量或面积表达模式而变化三倍。
The relationships between leaf nitrogen (N), specific leaf area (SLA) (an inverse index of leaf ''thickness'' or ''density''), and photosynthetic capacity (A(max)) were studied in 23 Amazonian tree species to characterize scaling in these properties among natural populations of leaves of different ages and light microenvironments, and to examine how variation within species in N and SLA can influence the expression of the A(max)-to-N relationship on mass versus area bases. The slope of the A(max)-N relationship, change in A per change in N (mumol CO2 gN-1 s-1), was consistently greater, by as much as 300%, when both measures were expressed on mass rather than area bases. The x-intercept of this relationship (N-compensation point) was generally positive on a mass but not an area basis. In this paper we address the causes and implications of such differences. Significant linear relationships (p < 0.05) between mass-based leaf N (N(mass)) and SLA were observed in 12 species and all 23 regressions had positive slopes. In 13 species, mass-based A(max) (A(mass)) was positively related (p < 0.05) with SLA. These patterns reflect the concurrent decline in N(mass) and SLA with increasing leaf age. Significant (p < 0.05) relationships between area-based leaf N (N(area)) and SLA were observed in 18 species. In this case, all relationships had negative slopes. Taken collectively, and consistent in all species, as SLA decreased (leaves become ''thicker'') across increasing leaf age and light gradients, N(mass) also decreased, but proportionally more slowly, such that N(area) increased. Due to the linear dependence of A(mass) on N(mass) and a negative 4-intercept, ''thicker'' leaves (low SLA) therefore tend, on average, to have lower N(mass) and A(mass) but higher N(area) than ''thinner'' leaves. This tendency towards decreasing A(mass) with increasing N(area) decreases the rate at which A(area) increases with Na(area) resulting in a lower slope of the A(max)-N relationship on an area than mass basis in 16 of 17 species where both were significant. For the sole species exception (higher area than mass-based slope) variation in N(area) was related to variation in N(mass) and not in SLA, and thus, these data are also consistent with this explanation. The relations between N, SLA and A(max) explain how the rate of change in A(max) per change in N can vary three-fold depending on whether a mass or area mode of expression is used.