Caloric content of plant species and its role in a Leymus chinensis steppe community of Inner Mongolia, China

The caloric contents of 42 species and their composition in a Leymus chinensis steppe community of Inner Mongolia, China were determined and analyzed based on the field experiment for 11 years. The caloric content (x ± SD) of aboveground parts of plant species varied from (13156 ± 1141) J·g−1 (ash contained) to (18141 ± 527) J·g−1. The average caloric content of all species was (16899 ± 840) J·g−1 and the inter-specific CV (coefficient of variation) was 4.9%. Of all the species, Caragana microphylla had the highest caloric content (18142 J·g−1). Grasses had a higher average caloric content ((17425 ± 291) J·g−1) than forbs ((16734 ± 844)J·g−1). When the herbaceous species were classified into subgroups according to life-form and growth-form, the order of average caloric contents, from high to low, was: tall grasses ((17717 ± 92) J·g−1) > legume ((17228 ± 433) J·g−1) > short grasses ((17250 ± 218) J·g−1) > remaining forbs ((16784 ± 529) J·g−1) > subshrubs ((16719 ± 69) J·g−1) > annuals and biennials ((15911 ± 1759) J·g−1). There was a positive correlation (P < 0.05) between the caloric contents of 42 species and their relative biomass in the community. When all species were classified into 3 groups according to their composition in the community, the average caloric contents, weighed by the species relative biomass, followed the order: dominant (17740 J·g−1) > companion (17244 J·g−1) > incidental (16653 J·g−1). The plants with high caloric contents were more competitive, which allowed them to gain a dominant status, whereas the competitive abilities of plants with low caloric contents were generally weak. The latter made up the companion or incidental species in a steppe community.