| In this study,six research sites of three types grassland in fenced grasslands of Northern China were used as research objects to analysis the differences in the response of biomass,stoichiometry and homeostasis of grassland communities to burning under different seasons.With the intensification of global drought,the theoretical basis and suggestions for the restoration and treatment of degraded grassland are provided.The main conclusions are as follows:(1)Burning did not significantly change the plant height,coverage and aboveground biomass of vegetation(P > 0.05),but significantly affected aboveground vegetation and underground biomass in all the study sites(P < 0.05).There were regional differences in the effect of burning on the characteristics of fenced grasslands of northern China,which promoted the growth of gramineae on the whole(the largest increase in the importance of plant species was 118.74%),inhibited the propagation of non-gramineae in all the study sites except Ewenki Banner,and improved the edibility of grassland communities(the largest decrease in the importance of plant species was 85.08%).Burning reduced the correlation between aboveground biomass,diversity indexes and environmental factors respectively,but increased the correlation between underground biomass and environmental factors.(2)There were seasonal differences and category differences of plant community functional groups in the effect of burning on the chemical properties of leaves,the effect of burning on the leaves of non-gramineous plants was stronger than that of gramineous plants,and the effect of burning on the leaves of plants in autumn was stronger than that in spring.There were no seasonal differences in the effects of burning on chemical properties and chemical element quantification ratios of root,but the significant effects of burning on chemical element quantification ratios of root at 0-10 cm were greater than that at 10-30 cm.There were regional differences in the effect of burning on the soil of fenced grassland,which was mainly affected by burning in autumn(P < 0.05).(3)The relationships between leaf-root-soil system and environmental factors changed in different degrees after burning.In the relationships between plant leaves and environmental factors,burning had little effect on the correlation.Burning in different seasons strengthened the correlation between plant roots and environmental factors,even changed the positive or negative correlation,and the effect of burning in spring was stronger than that in autumn.however,the correlation between soil and environmental factors was weakened by burning in different seasons,and the weakening effect of burning in autumn was stronger than that of burning in spring.(4)The effects of burning in autumn on the stoichiometric homeostasis of leaves and roots elements were significantly stronger than that of burning in spring;the stoichiometric homeostasis of carbon and phosphorus elements of leaves was stronger than that in roots under burning,which always maintained a "strict homeostasis"(P > 0.05);however,the stoichiometric homeostasis of nitrogen of roots was stronger than that of leaves,and it was always maintained as "strict homeostasis"(P > 0.05).The stoichiometric homeostasis of nitrogen in leaves decreased significantly under burning,the stoichiometric homeostasis of nitrogen in gramineae decreased to "weak homeostasis"(0.25 < 1/H < 0.5)after burning of two seasons,and the stoichiometric homeostasis of nitrogen decreased to "weak homeostasis"(0.25 < 1/H < 0.5)after burning in autumn;however,the stoichiometric homeostasis of carbon and phosphorus in roots decreased significantly.The stoichiometric homeostasis of carbon in roots of 10-30 cm and 0-30 cm decreased to "homeostatic"(0 <1/H < 0.25)after burning in autumn,and the stoichiometric homeostasis of phosphorus in roots of 0-10 cm and 0-30 cm decreased to "weak homeostasis"(0.25 < 1/H < 0.5)and "weakly plastic"(0.5 < 1/H < 0.75)after burning in autumn,respectively. |
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