Evidence for “diminishing returns” from the scaling of stem diameter and specific leaf area

Abstract

Research indicates that increases in total leaf area (A(T)) may fail to keep pace with increases in total leaf mass (M(L)) across plants differing in size (e.g., as measured by stem diameter, D). This "diminishing returns" hypothesis predicts that the scaling exponent for A(T) vs. M(L) will be less than one and that the exponent for specific leaf mass (i.e., A(T) / M(L)) vs. D will be negative. These predictions were examined using data from 46 plants ranging between 0.125 cm ≤ D ≤ 0.485 m across 25 woody dicot species. Standardized major axis slopes were used to quantify scaling exponents and random effects models were used to quantify species and size effects on the numerical values of exponents. The exponents for A(T) vs. M(L) and A(T) / M(L) vs. D differed among species and different species groupings. In general, the exponent for A(T) vs. M(L) was less than one and the exponent for A(T) / M(L) vs. D was negative, as predicted. However, random effects models indicated that species effects overshadowed size effects, although size effects were statistically significant. The diminishing returns hypothesis therefore receives statistical support, i.e., although the numerical values of exponents are "species-dependent," they are less than unity, as predicted by theory.

Within-stand and seasonal variations of specific leaf area in a clonal Eucalyptus plantation in the Republic of Congo

“…3a-b and (4)) made it possible to predict accurately A t , B t , and SLA t from DBH. As reported in two recently published studies (Holdaway et al, 2008;Niklas and Cobb, 2008), we found that A t increased non-isometrically with B t : for increasing tree size, A t increased more slowly than B t (b A < b B ), thus explaining the decreases in SLA t with increasing DBH (a < 1, and b SLA < 0). Our mean a value (0.91; Table 1) was similar to the mean value (0.90) found by Holdaway et al (2008) for several Nothofagus solandri stands in New Zealand.…”

“…Similar tree size related differences in SLA have been reported for other tree species (e.g., Niinemets, 1997;Holdaway et al, 2008;Niklas and Cobb, 2008), but it is still unclear if these differences are mostly driven by ontogenic changes (e.g., Day et al, 2001), differences in light-environment (e.g., White and Scott, 2006), or increased water limitation with tree size (e.g., Woodruff et al, 2004;Cavaleri et al, submitted for publication).…”

Adaptability of Woody Plants in Aridic Conditions

“…The reduction of leaf area during water deficit is typical for plants from arid stands. Several authors (Reich et al, 2003, Wright et al, 2004Niclas & Cobb, 2008) have confirmed the narrow relationship between leaf structure and function. Our comparison of the leaf area ratio to dry weight of the leaves (SLA) of the analysed species confirmed the interspecific differences (Table 1).…”

Multi-year Assessment of Airborne Metals in Fallon, Nevada, Using Leaf-surface Chemistry

“…Oven dry leaf masses were first transformed to the ¾ power before this standardization step. This transformation incorporates a concept of diminishing returns whereby leaf area increases ever more slowly as leaf mass increases, i.e., at a power of ¾ of leaf mass (Niklas & Cobb, 2008). This transformation was not done originally with the 2007 leaf collection (Sheppard et al, 2009a), but it has since been done on that data set in addition to the data from 2008-2010.…”