Elm （Ulmus pumila）, widely distributed in the north temperate zone, contributes to a special savanna-like woodland in typical grassland region in the northeastern China. This woodland performs a variety of ecologica...Elm （Ulmus pumila）, widely distributed in the north temperate zone, contributes to a special savanna-like woodland in typical grassland region in the northeastern China. This woodland performs a variety of ecological functions and environmental signifi- cance, such as decreasing soil erosion, stabilizing sand dunes, preserving species diversity. However, in the last approximate 30 years, the species composition, productivity and distribution area of elm woodland has decreased severely. A series of studies have been carried out to find out whether the climate changes or human disturbances caused the degradation of elm woodland and how these factors af- fected elm woodland. In this study, undisturbed, plowing and grazing elm woodland were investigated in 1983 and 2011 by using Point-Centered Quarter method. The relationship between vegetation changes and environmental factors was analyzed by Bray-Curtis ordination. The results show that in 2011, species diversity and understory productivity of undisturbed elm woodland decrease slightly compared to those of undisturbed elm woodland in 1983. However, nearly 60% of the species is lost in the plowing and grazing elm woodland relative to the species undisturbed elm woodland in 1983. Interestingly, plowing stimulates the growth of elm and certain understory species through furrowing soil and accelerating soil nutrient turnover rate. Grazing disturbance not only leads to species loss and productivity decrease, but also induces changes in elm growth （small, short and twisted）. The mean age of the elm was 29 -4- 2 yr in undisturbed and plowing elm woodland, while only 15 yr in the grazing elm woodland. The results of Bray-Curtis ordination analysis show that all sample stands clustered to three groups： Group I including the undisturbed sample stands of 83UE （undisturbed elm wood- land in 1983） and l lUE （undisturbed elm woodland in 2011）; Group II including sample stands of PE （elm woodland disturbed by plowing）; Group III including samples stands of GE （elm woodland disturbed by grazing）. The results indicate that the long time distur- bance of the plowing and grazing have converted elm woodland to different community types. Climate change is not the primary reason causing the degradation of elm woodland, but plowing and grazing disturbance. Both plowing and grazing decrease the vegetation composition and species diversity. Grazing further decreases vegetation productivity and inhibits the growth of elm tree. Therefore, we suggest that reasonable plowing and exclusive grazing would be favorable for future regeneration of degraded elm woodland.展开更多
This paper investigated effects of four ecological variables on the damage levels of elm leaf beetle （different effects of minimum and maximum values, relations between each two variables were also explored） and dis...This paper investigated effects of four ecological variables on the damage levels of elm leaf beetle （different effects of minimum and maximum values, relations between each two variables were also explored） and discussed current management measures. The results showed that among these factors, interval between elm trees significantly affected damage level by this leaf beetle species, and perimeter of elm trunk could change this effect. On the other side, while middle values for each index were deleted, effects comparison between minimum and maximum parts showed that good root soil as overwintering was related with more damage; more severe damages on elm tree would result in more control measures used; on elm tree with bigger mink, more damages were observed; and if other elm tree was closer, more damages would occur. Secondly, good root soil was related with more measures used; good root soil was correlated with smaller perimeter; good root soil was associated with bigger interval. Thirdly, more measures were correlated with bigger perimeter; more measures were also correlated with good root soil. Fourthly, bigger perimeter was correlated with worse root soil. Current dominant control measures included chemical pesticide application preventing adult insects from descending or climbing up along trunk before and after overwintering. These results suggested that we should focus on elm leaf beetle management on all the elm trees instead of only on bigger elm trees at proper period simultaneously because occurrence on these elm trees were related intensively although this adult elm leaf beetle species could not fly and had limited movement ability.展开更多
基金Under the auspices of the Seventh Framework Programme(European Commission,No.226818)National Natural Science Foundation of China(No.31070294,31072070,31100331)
文摘Elm （Ulmus pumila）, widely distributed in the north temperate zone, contributes to a special savanna-like woodland in typical grassland region in the northeastern China. This woodland performs a variety of ecological functions and environmental signifi- cance, such as decreasing soil erosion, stabilizing sand dunes, preserving species diversity. However, in the last approximate 30 years, the species composition, productivity and distribution area of elm woodland has decreased severely. A series of studies have been carried out to find out whether the climate changes or human disturbances caused the degradation of elm woodland and how these factors af- fected elm woodland. In this study, undisturbed, plowing and grazing elm woodland were investigated in 1983 and 2011 by using Point-Centered Quarter method. The relationship between vegetation changes and environmental factors was analyzed by Bray-Curtis ordination. The results show that in 2011, species diversity and understory productivity of undisturbed elm woodland decrease slightly compared to those of undisturbed elm woodland in 1983. However, nearly 60% of the species is lost in the plowing and grazing elm woodland relative to the species undisturbed elm woodland in 1983. Interestingly, plowing stimulates the growth of elm and certain understory species through furrowing soil and accelerating soil nutrient turnover rate. Grazing disturbance not only leads to species loss and productivity decrease, but also induces changes in elm growth （small, short and twisted）. The mean age of the elm was 29 -4- 2 yr in undisturbed and plowing elm woodland, while only 15 yr in the grazing elm woodland. The results of Bray-Curtis ordination analysis show that all sample stands clustered to three groups： Group I including the undisturbed sample stands of 83UE （undisturbed elm wood- land in 1983） and l lUE （undisturbed elm woodland in 2011）; Group II including sample stands of PE （elm woodland disturbed by plowing）; Group III including samples stands of GE （elm woodland disturbed by grazing）. The results indicate that the long time distur- bance of the plowing and grazing have converted elm woodland to different community types. Climate change is not the primary reason causing the degradation of elm woodland, but plowing and grazing disturbance. Both plowing and grazing decrease the vegetation composition and species diversity. Grazing further decreases vegetation productivity and inhibits the growth of elm tree. Therefore, we suggest that reasonable plowing and exclusive grazing would be favorable for future regeneration of degraded elm woodland.
基金Supported by SIPT of Northeast Agricultural University(201410224069)the National Natural Science Foundation of China(31100304)"Academic Backbone" Project of Northeast Agricultural University(15XG01)
文摘This paper investigated effects of four ecological variables on the damage levels of elm leaf beetle （different effects of minimum and maximum values, relations between each two variables were also explored） and discussed current management measures. The results showed that among these factors, interval between elm trees significantly affected damage level by this leaf beetle species, and perimeter of elm trunk could change this effect. On the other side, while middle values for each index were deleted, effects comparison between minimum and maximum parts showed that good root soil as overwintering was related with more damage; more severe damages on elm tree would result in more control measures used; on elm tree with bigger mink, more damages were observed; and if other elm tree was closer, more damages would occur. Secondly, good root soil was related with more measures used; good root soil was correlated with smaller perimeter; good root soil was associated with bigger interval. Thirdly, more measures were correlated with bigger perimeter; more measures were also correlated with good root soil. Fourthly, bigger perimeter was correlated with worse root soil. Current dominant control measures included chemical pesticide application preventing adult insects from descending or climbing up along trunk before and after overwintering. These results suggested that we should focus on elm leaf beetle management on all the elm trees instead of only on bigger elm trees at proper period simultaneously because occurrence on these elm trees were related intensively although this adult elm leaf beetle species could not fly and had limited movement ability.
