Study On Plant Species Litter Decomposition Changes Under Different Grazing Intensities In The Songnen Grassland

Litter accumulation and decomposition are basic functional processes of grasslandecosystem, and its nutrient dynamic and cyclic process directly affect grassland ecosystemservices and functioning. Grazing is one of the most important use of grassland and animal’sbehaviors, feeding, trampling and discharging, directly or indirectly affect plant communitycomposition, ecological system functioning, soil environment and soil biological community.It may promote the soil nitrogen mineralization, and is advantageous to the transformation oforganic nitrogen to inorganic state form in the soil, which is easy for plants to uptake, and, inturn, affects the litter decomposition and nutrient cycling. Therefore, the study onaccumulation and decomposition of the litter under different grazing intensities can not onlyprovide a theoretical basis on grazing ecosystem nutrient cycling study, but also play animportant guiding role on rational utilization of grassland and maintaining the sustainabledevelopment of grassland ecosystem.This study was conducted on the GSCR platform at the Songnen Grassland EcosystemResearch Station of Northeast Normal University. It examined the interspecific difference inlitter decomposition of the main plant speciess (Leymus chinensis, Chloris virgata,Phragmitis australis, Kalimeris interifolia, Hemarthria sibirica, Setaria viridis,Calamagrostis epigeios), as well as impacts of grazing intensities (control, light grazing andheavy grazing) on rate of plant species litter decomposition and carbon, nitrogen andphosphorus loss. There were the main results as followed:(1) Both litter decomposition rate and C loss rate showed change among differentspecies: C. virgate> K. interifolia> S. viridis> L. chinensis> C. epigeios> P. australis> H. sibirica.There was no significant difference in litter decomposition rate between P. australis and H.sibirica (P>0.05). There were significant difference in litter decomposition rate and loss rateof C among other plant species (P <0.05). Litter decomposition rate of different plant specieswere positively correlated with N and P content and negatively correlated with C content andC/N. So, litter decomposition increased with N and P content and decreased with C contentand C/N. Litter P loss rate showed interspecific difference: P. australis <H. sibirica <S. viridis <C. epigeios <L. chinensis <K. interifolia <C. virgata. There were no significant difference in litterP loss rate between L. chinensis or K. interifolia and S. viridis, between C. epigeios and L. chinensis,between P. australis and H. sibirica (P>0.05). Litter P loss rate of C. virgata were significantdifferent from other six plant species (P <0.05). There were siginificant differences in litter Nloss rate among all the plant species. Specifically, litter N loss rate changed among differentplant species as: H. sibirica <C. epigeios <S. viridis <C. virgate <P. australis <L. chinensis <K. interifolia.(2) Light grazing significantly increased the litter decomposition rate of P. australis, H.sibirica, L. chinensis and S. viridis, and significantly reduced the litter decomposition rate of K.interifolia (P <0.05). There was no significant difference in litter decomposition rate of C.virgata between the control and light grazing (P>0.05). Decomposition rate of different plantspecies litter were significantly increased by heavy grazing (P <0.05). Both light grazing andheavy grazing significantly increased litter C loss rate of H. sibirica, L. chinensis, C. virgata andS. viridis, and significantly reduced C loss rate of K. interifolia (P <0.05). There was nosignificant difference in litter C loss rate of P. australis between light grazing and the control(P>0.05), but the difference between heavy grazing and the control was significant (P <0.05). Light grazing significantly reduced litter N loss rate of P. australis, L. chinensis and K.interifolia, and significantly enhanced litter N loss rate of H. sibirica and S. viridis (P <0.05).There was no significant response in litter N loss rate of C. virgata to light grazing (P>0.05).Heavy grazing significantly reduced litter N loss rate for each plant species (P <0.05). Lightgrazing significantly increased litter P loss rate of P. australis, H. sibirica, C. virgata and S. viridis(P <0.05), but not for L. chinensis and K. interifolia. Heavy grazing significantly increasedlitter P loss rate of different plant species (P <0.05).In general, litter decomposition and C loss rate of annual plant were significantly higherthan that of perennial plant (except K. interifolia), and litter decomposition and C loss rate ofcompositae plant were significantly higher than that of gramineae (except C. virgata). Litter Ploss rate of annual plant (expect S. viridis) was higher than that of perennial plant, and litter Ploss rate of compositae plant was higher than that of gramineae (except C. virgata). Litter Nloss rate of compositae plant was higher than that of gramineae. The interspecific differencein litter decomposition showed that litter decomposition rate depended mainly on its quality.With the increase of grazing intensities, litter decomposition rate (in addition to K.interifolia) increased, but there was difference in the magnitude of the response. Effects ofgrazing intensities on the decomposition depended on litter quality (N and P content).Herbivore grazing had a stronger effect on plant species litter with lower N and P content;Grazing promoted carbon release of plant litter (with the exception of P. australis and K.interifolia). Except for H. sibirica and S. viridis under the condition of light grazing, litternitrogen tended to accumulate under grazing conditions for other species. Except for K.interifolia under light grazing condition, litter phosphorus of other plant species tended torelease under grazing conditions.