Trade-offs between the metabolic rate and population density of plants.
The energetic equivalence rule, which is based on a combination of metabolic theory and the self-thinning rule, is one of the fundamental laws of nature. However, there is a progressively increasing body of evidence that scaling relationships of metabolic rate vs. body mass and population density vs. body mass are variable and deviate from their respective theoretical values of 3/4 and -3/4 or -2/3. These findings questioned the previous hypotheses of energetic equivalence rule in plants. Here we examined the allometric relationships between photosynthetic mass (M(p)) or leaf mass (M(L)) vs. body mass (beta); population density vs. body mass (delta); and leaf mass vs. population density, for desert shrubs, trees, and herbaceous plants, respectively. As expected, the allometric relationships for both photosynthetic mass (i.e. metabolic rate) and population density varied with the environmental conditions. However, the ratio between the two exponents was -1 (i.e. beta/delta = -1) and followed the trade-off principle when local resources were limited. Our results demonstrate for the first time that the energetic equivalence rule of plants is based on trade-offs between the variable metabolic rate and population density rather than their constant allometric exponents.
Deng
Jian-Ming
JM
MOE Key Laboratory of Arid and Grassland, School of Life Science, Lanzhou University, Lanzhou, China.
Li
Tao
T
Wang
Gen-Xuan
GX
Liu
Jing
J
Yu
Ze-Long
ZL
Zhao
Chang-Ming
CM
Ji
Ming-Fei
MF
Zhang
Qiang
Q
Liu
Jian-Quan
JQ
D004734:Energy Metabolism; D010788:Photosynthesis; D010944:Plants / Q000378:metabolism*; D013045:Species Specificity