Riverdikes are habitats that must be revegetated quickly in order to prevent soil erosion. With increasing pressure to improve the cost efficiency of management, new revegetation techniques suitable under reduced mowi...Riverdikes are habitats that must be revegetated quickly in order to prevent soil erosion. With increasing pressure to improve the cost efficiency of management, new revegetation techniques suitable under reduced mowing frequencies are required. Imperata cylindrica (L.) P. Beauv. is an important component of grasslands in several Asian countries. Its vigorous rhizome elongation should be useful for quickly covering bare ground. We tested the effects of sowing (at two densities), transplanting, and sodding of I. cylindrica on plant cover and species richness of established vegetation over 3 years. The sodding and high-density sowing treatments achieved the most rapid increase in cover, followed by low-density sowing, transplanting, and the control. By year 2, however, the cover in the low- and high-density sowing treatments was similar. The sodding treatment had significantly fewer species than the other treatments in year 1. Between years 1 and 2 and years 2 and 3, the total number of species increased in the transplanting treatment, whereas it decreased in the sodding and two sowing treatments. Accordingly, if stabilization and erosion control are the priority, introduction of I. cylindrica using sod and high-density sowing is the most suitable method. If immediate green-up is not imperative, low-density sowing is likely to provide available resources for new seedlings of diverse species to become established, allowing the introduction of representative species in semi-natural grasslands. More research will be needed on the effects of introducing diverse species (e.g., sowing seed mixtures) that include I. cylindrica on the resulting floristic composition.展开更多
Shrub species are used in restoration projects on dryland for their facilitation effects,which include environmental improvements and protection from herbivore feeding.Facilitation effects on forage grasses are potent...Shrub species are used in restoration projects on dryland for their facilitation effects,which include environmental improvements and protection from herbivore feeding.Facilitation effects on forage grasses are potentially important in improving grazing capacity on rangelands.However,the morphology-dependent performance of benefactor plants in facilitating forage species growth and supplementation under moderate grazing intensity remains unclear.Here,our main purpose was to measure facilitation performance in terms of the survival of a native forage grass,Agropyron cristatum(L.)Gaertn.(Gramineae).,in accordance with the growth conditions of a sand-fixing benefactor shrub,Caragana microphylla Lam.,in the Hulun Buir Grassland,northern China.Six study sites with patches of A.cristatum and C.microphylla were established at the foot of fixed sand dunes.At each site,five quadrats were set in places where C.microphylla coverage was 100%and A.cristatum grew among the shrubs(shrub quadrats),and another five were set where A.cristatum grew alone without C.microphylla(grass quadrats).We measured the morphological traits of C.microphylla and A.cristatum in all 60 quadrats,along with the soil water content and soil temperature.The data were compared between the shrub and grass quadrats by generalized linear mixed-effect models to assess the shrub's facilitation effects.We also used such models to elucidate the relationship between the average height of C.microphylla and the morphological traits of A.cristatum in the shrub quadrats.The maximum height,average grazed height,and the number of seed heads of A.cristatum were greater in the shrub quadrats than in the grass quadrats.The soil surface temperature was lower in the shrub quadrats.The maximum height and seed head number of A.cristatum were positively associated with the average height of C.microphylla.These results suggest that the grazing impact and heat stress were smaller in shrub quadrats than in grass quadrats,and that the degree of this protective effect depended on the shrub height.The shrub canopy seemed to reduce the increase in soil temperature and keep the grass vigorous.Livestock likely avoided grazing grasses in the C.microphylla patches because of the shrub's spiny leaves;only the upper parts of the grass stems(including the seed heads)protruding from the shrub canopy were grazed.The sand-fixing shrub thus moderates the grazing impact and soil temperature,and contributes to vegetation restoration and grazing system sustainability.展开更多
文摘Riverdikes are habitats that must be revegetated quickly in order to prevent soil erosion. With increasing pressure to improve the cost efficiency of management, new revegetation techniques suitable under reduced mowing frequencies are required. Imperata cylindrica (L.) P. Beauv. is an important component of grasslands in several Asian countries. Its vigorous rhizome elongation should be useful for quickly covering bare ground. We tested the effects of sowing (at two densities), transplanting, and sodding of I. cylindrica on plant cover and species richness of established vegetation over 3 years. The sodding and high-density sowing treatments achieved the most rapid increase in cover, followed by low-density sowing, transplanting, and the control. By year 2, however, the cover in the low- and high-density sowing treatments was similar. The sodding treatment had significantly fewer species than the other treatments in year 1. Between years 1 and 2 and years 2 and 3, the total number of species increased in the transplanting treatment, whereas it decreased in the sodding and two sowing treatments. Accordingly, if stabilization and erosion control are the priority, introduction of I. cylindrica using sod and high-density sowing is the most suitable method. If immediate green-up is not imperative, low-density sowing is likely to provide available resources for new seedlings of diverse species to become established, allowing the introduction of representative species in semi-natural grasslands. More research will be needed on the effects of introducing diverse species (e.g., sowing seed mixtures) that include I. cylindrica on the resulting floristic composition.
基金supported by the Tripartite Environment Ministers Meeting(TEMM)JSPS KAKENHI(JP19H04316).We thank the staff of the Chinese Research Academy of Environmental Sciences(CRAES)the Overseas Environmental Cooperation Center(OECC),Japan for their support during the field survey.
文摘Shrub species are used in restoration projects on dryland for their facilitation effects,which include environmental improvements and protection from herbivore feeding.Facilitation effects on forage grasses are potentially important in improving grazing capacity on rangelands.However,the morphology-dependent performance of benefactor plants in facilitating forage species growth and supplementation under moderate grazing intensity remains unclear.Here,our main purpose was to measure facilitation performance in terms of the survival of a native forage grass,Agropyron cristatum(L.)Gaertn.(Gramineae).,in accordance with the growth conditions of a sand-fixing benefactor shrub,Caragana microphylla Lam.,in the Hulun Buir Grassland,northern China.Six study sites with patches of A.cristatum and C.microphylla were established at the foot of fixed sand dunes.At each site,five quadrats were set in places where C.microphylla coverage was 100%and A.cristatum grew among the shrubs(shrub quadrats),and another five were set where A.cristatum grew alone without C.microphylla(grass quadrats).We measured the morphological traits of C.microphylla and A.cristatum in all 60 quadrats,along with the soil water content and soil temperature.The data were compared between the shrub and grass quadrats by generalized linear mixed-effect models to assess the shrub's facilitation effects.We also used such models to elucidate the relationship between the average height of C.microphylla and the morphological traits of A.cristatum in the shrub quadrats.The maximum height,average grazed height,and the number of seed heads of A.cristatum were greater in the shrub quadrats than in the grass quadrats.The soil surface temperature was lower in the shrub quadrats.The maximum height and seed head number of A.cristatum were positively associated with the average height of C.microphylla.These results suggest that the grazing impact and heat stress were smaller in shrub quadrats than in grass quadrats,and that the degree of this protective effect depended on the shrub height.The shrub canopy seemed to reduce the increase in soil temperature and keep the grass vigorous.Livestock likely avoided grazing grasses in the C.microphylla patches because of the shrub's spiny leaves;only the upper parts of the grass stems(including the seed heads)protruding from the shrub canopy were grazed.The sand-fixing shrub thus moderates the grazing impact and soil temperature,and contributes to vegetation restoration and grazing system sustainability.