Changes in plant biomass and species composition of alpine Kobresia meadows along altitudinal gradient on the Qinghai-Tibetan Plateau

Abstract

Alpine Kobresia meadows are major vegetation types on the Qinghai-Tibetan Plateau. There is growing concern over their relationships among biodiversity, productivity and environments. Despite the importance of species composition, species richness, the type of different growth forms, and plant biomass structure for Kobresia meadow ecosystems, few studies have been focused on the relationship between biomass and environmental gradient in the Kobresia meadow plant communities, particularly in relation to soil moisture and edaphic gradients. We measured the plant species composition, herbaceous litter, aboveground and belowground biomass in three Kobresia meadow plant communities in Haibei Alpine Meadow Ecosystem Research Station from 2001 to 2004. Community differences in plant species composition were reflected in biomass distribution. The total biomass showed a decrease from 13196.96+/-719.69 g/m(2) in the sedge-dominated K. tibetica swamp to 2869.58+/-147.52 g/m(2) in the forb and sedge dominated K. pygmaea meadow, and to 2153.08+/-141.95 g/m(2) in the forbs and grasses dominated K. humilis along with the increase of altitude. The vertical distribution of belowground biomass is distinct in the three meadow communities, and the belowground biomass at the depth of 0-10 cm in K. tibetica swamp meadow was significantly higher than that in K. humilis and K. pygmaea meadows (P<0.01). The herbaceous litter in K. tibetica swamp was significantly higher than those in K. pygnaeca and K. humilis meadows. The effects of plant litter are enhanced when ground water and soil moisture levels are raised. The relative importance of litter and vegetation may vary with soil water availability. In the K. tibetica swamp, total biomass was negatively correlated to species richness (P<0.05); aboveground biomass was positively correlated to soil organic matter, soil moisture, and plant cover (P<0.05); belowground biomass was positively correlated with soil moisture (P<0.05). However, in the K. pygnaeca and K. humilis meadow communities, aboveground biomass was positively correlated to soil organic matter and soil total nitrogen (P<0.05). This suggests that the distribution of biomass coincided with soil moisture and edaphic gradient in alpine meadows.

Dynamics of above- and below-ground biomass and C, N, P accumulation in the alpine steppe of Northern Tibet

“…These results are consistent with the alpine meadow ecosystem in the Tibetan Plateau, where the biomass of the companion species such as legumes, sedges, and forbs was higher than the biomass of the dominant species in the Kobresia pygnaeca meadow, Kobresia humilis meadow, and Kobresia tibetica swamp meadow . The biomass of the alpine steppe in the current study is lower than the biomass of alpine meadow in the Tibetan Plateau reported by Kato et al (2004), Zhao et al (2005), Wang et al (2008), andZhang et al (2009). This is because the habitat of the alpine steppe is harsher, and plant growth is limited by the low temperature and precipitation, as well as the barren soils when compared with the alpine meadow.…”

Adaptive characteristics of grassland community structure and leaf traits along an altitudinal gradient on a subtropical mountain in Chongqing, China

“…Previous studies have shown that above-ground biomass may decrease (Pérez and Frangi 2000;Wang et al 2007Wang et al , 2008, or present a hump-shaped pattern in relation to altitude (Raich et al 1997). For the Hongchiba Fig.…”

“…There are many studies relating to biomass structure and species richness so there is considerable information about how these are adapted to altitudinal gradients (Fleishman et al 1998;Pérez and Frangi 2000;Lomolino 2001;Rahbek 1995Rahbek , 2005Wang et al 2007Wang et al , 2008. Nevertheless, patterns of species richness and biomass along altitudinal gradients vary geographically.…”

“…Above-ground biomass may show a linearly decreasing pattern (Pérez and Frangi 2000;Wang et al 2007Wang et al , 2008, or a hump-shaped pattern in relation to altitude (Raich et al 1997). Obtaining measurements of below-ground biomass of plant communities is much more difficult than obtaining measurements of above-ground biomass.…”

“…The relationship between plant species richness and biomass is also a topic of several studies of terrestrial ecosystems (Kassen et al 2000;Lomolino 2001;Mittelbach et al 2001;Whittaker and Heegaard 2003), but biomass measured in these studies is mostly that above-ground. Below-ground biomass affects subsurface biogeochemical processes and soil development to modify the habitat for vegetation, and consequently influences above-ground community structure and species richness in interaction with environmental factors (e.g., precipitation and temperature) (Fan et al 2009;Wang et al 2007Wang et al , 2008. Thus, there is a need for further studies of relationships between species richness and below-ground biomass.…”