Most diversity restoration projects are not to improve diversity per se, but rather to enhance the presence and abundance of species that are characteristic of reference or target community. The use of Bromus inermis ...Most diversity restoration projects are not to improve diversity per se, but rather to enhance the presence and abundance of species that are characteristic of reference or target community. The use of Bromus inermis suppresses annual noxious grasses and increases the control of other-forb group these species are also noxious weeds;these may be substituted with another perennial species of the same functional group all through the whole experimental period, as it occurs with other perennial-forb Carduus tenuifolius. A field experiment was conducted on abandoned arable land with sown low and high diversity treatments and natural colonization following typical farming practice for the site. Experimental plots were installed on former agricultural land that had been cropped with (a rotation of) monocultures until the end of 1995. The experiment was organized according to a block design with five replicate blocks. An opposite trend was performed among the colonizer species, because the colonizer grasses were relegated by the high dominance of sown grasses. But at the same time, the sown grasses facilitated the dominance of other colonizer-forbs species;therefore its functional replacement in the community due to sown effect was again tested. However, in natural conditions the other-forbs group was the dominant group, without taking into account the stepping-stone treatment and there was also a functional change of dominance. Our study has demonstrated the restoration effectiveness of species richness at abandoned arable land and may be enhanced by sowing late successional species.展开更多
Background: Can high diversity mixtures of later succession plant species be able to suppress early successional (arable weed) species than low diversity species mixtures? Can the removal of plant functional groups ha...Background: Can high diversity mixtures of later succession plant species be able to suppress early successional (arable weed) species than low diversity species mixtures? Can the removal of plant functional groups have important consequences on the sys-tem stability? Location: The study area was located at 850 m a.s.l., fifteen kilometers (15 km) to the west of Salamanca city, Spain, in a dehesa-like woodland. Methods: The field experiment was installed in Spring 1996 (May). The plots represented former agricultural lands cropped with (a rotation of) monocultures and abandoned right at the beginning of the experiment after the last crop was harvested in 1995. Before in-stalling plots, the fields were harrowed and equalized. The treatments (NC-natural colonization, LD-low diversity seed mixture and HD-high diversity seed mixture) were randomly allocated to the plots in each block. The experiment was organised accord-ing to a block design with five replicate blocks. Within each block, four plots measur-ing 10 × 10 m were marked out and each of the three treatments was randomly as-signed to one plot. All plots were separated by 2 m walkways. Results: The competitive ability of the sown species in different mixtures in LD, valued on the basis of their performance in HD, is a good predictor of their ability to suppress the weed crops spe-cies. This was also corroborated by the high relationship between the efficiency of the sown species in both treatments of species mixture (R<sup>2</sup> = 0.51, F (1, 33) = 34.56, P < 0.001). Conclusions: The increase of colonizing species cover was significantly lower in LD, which again supported the increase of biomass in 1998, being also lower in HD. Therefore, this increase in the community is more prominent in LD treatments. The effect of sown species was not so important in this increase.展开更多
We report carbon stock in biomass, litter and soil estimated for six locations in natural Quercus ilex L. stands of the Middle and High Moroccan Atlas. Twenty trees at each location were selected according to their di...We report carbon stock in biomass, litter and soil estimated for six locations in natural Quercus ilex L. stands of the Middle and High Moroccan Atlas. Twenty trees at each location were selected according to their diameter classes and felled to measure the biomass of trunk, branches, twigs and leaves and determine allometric relationships. Soil was sampled in five depths (0 - 15, 15 - 30, 30 - 50, 50 - 70 and 70 - 100 cm) and litterfall production measured in all tree stands. The total carbon stock in above-ground biomass ranged between 17 Mg·haǃ in Aït Aamar stand (High Atlas) and 91 Mg·haǃ in Ksiba stand (Middle Atlas). Perennial organs (trunk, branches and twigs) stored over 95% of the tree carbon stock. Soil organic carbon concentrations ranged from 0.01% (in 70 - 100 cm in all stands) to 8.1% (in 0 - 15 cm in the Ajdir stand in Middle Atlas). The total organic carbon stock in the soil ranged between 141.4 t·haǃ in Ajdir and 24.6 t·haǃ in Asloul. The litter contained 0.2 Mg C haǃ in the clearing (C2) stand of High Atlas and 14.3 Mg C haǃ in (Ajdir) of carbon. The best fitted model for predicting carbon stock in tree biomass was obtained by applying the allometric equation Y = aXb for each biomass fraction and stand, where Y is the aboveground biomass (dry weight) and X is the DBH (Mean diameter at breast height, 1.30 m). These previous data obtained in the present study confirm the important function of these natural forests as longterm C sinks, in forest biomass, litter and soil. The potential long term C storage of these systems is moderately high, especially in less-intensively managed forests that include large trees. The established relationship between DBH and carbon stock in different tree organs can be used for forest carbon accounting, and also synthesize available information on oak forest as a sink for atmospheric CO2, and identify the management options that may enhance the capacity for C capture/ storage in forest soils.展开更多
The dynamics of organic matter, carbon and nitrogen were studied during leaf decomposition over a three annual cycles period using the litterbag method at three permanently untilled and unfertilised plots. Our hypothe...The dynamics of organic matter, carbon and nitrogen were studied during leaf decomposition over a three annual cycles period using the litterbag method at three permanently untilled and unfertilised plots. Our hypothesis is to determine if each litter type influences the decomposition and C and N releases from each other litter type （three plots and two species）. The main objective of this study is the comparison of decomposition dynamics in a climax forest with respect to that occurring in the chestnut managed plots on terrain suitable for oak to have further insight into the recycling of above ground organic matter and these two associated bioelements. As for the loss of dry matter, two-way analysis of variance, involving the treatment and year factors, revealed the existence of significant differences only for year, while no differences were observed for either treatment or interaction. At the end of the 2.4 years of the study, most of the treatment assays higher nitrogen concentrations than the initial ones were recorded. These three treatments the samplings prior to the last one revealed nitrogen concentrations higher than the initial ones, such that it may be concluded that the trend was towards an increase in concentration.展开更多
A field experiment was carried out at the CSIC Muñovela farm belonging to the Spanish National Research Council (CSIC) in order to evaluate the effect of sowing orchard grass (Dactylis glomerata var. Trerano) ...A field experiment was carried out at the CSIC Muñovela farm belonging to the Spanish National Research Council (CSIC) in order to evaluate the effect of sowing orchard grass (Dactylis glomerata var. Trerano) and lucerne (Medicago sativa var. Aragon) in monoculture and in combination. The experiment was based on a randomized block designed with a factorial arrangement (5 × 2). Experimental units were 40 plots distributed in four blocks. The phosphorus fertilization (P) factor included two types of conditions: basal fertilization without phosphorus (-P) and basal fertilization with phosphorus (+P), and the vegetation cover factor (T) included five conditions depending on the grass (G) and the legume (L). Above-ground biomass showed statistically significant differences among seasons and years (P Lolium perenne L. and Poa pratensis L. throughout the three years indicated that both species significantly increased their presence over time regardless of the treatments applied. The analysis performed for the other plant species (those other than grasses and legumes) allowed us to determine that the T1 and T5 treatments, which correspond to single species not treated with the application of phosphorus, influenced the presence of 70% of other species planted. Our specific aim was to explore how changing plant biotic diversity affects productivity under a given set of conditions. We manipulated plant species richness as an experimental factor to determine if productivity would be affected by changes in the ratios of plants sown.展开更多
Grasses represent one of the Earth’s most common plant groups,and natural and cultivated habitats dominated by grasses cover about 40%of the land surface.In turn,each grass species hosts multiple fungal species which...Grasses represent one of the Earth’s most common plant groups,and natural and cultivated habitats dominated by grasses cover about 40%of the land surface.In turn,each grass species hosts multiple fungal species which can behave as endophytes.An analysis of the endophytic taxa identified in surveys conducted in 14 grass species showed that some of the most frequent taxa on each grass were also present across several host grasses.These taxa were Alternaria,Epicoccum,Cladosporium,Fusarium,and a few others.A similar analysis of airborne fungi surveyed at 41 different locations throughout the world showed that some of the most geographically widespread,and most locally frequent airborne fungi belonged to the same genera that are dominant endophytes in grasses(i.e.Cladosporium,Alternaria,Fusarium,etc.).Therefore,airborne spores of genera that are ubiquitous in grasses are common worldwide and attain high atmospheric concentrations.In addition,spores of the above mentioned fungi are also important respiratory allergens.Direct observation indicates that saprobic colonization and sporulation of non-systemic grass endophytes could become unrestrained when their host plant tissue dies.Subsequently,when appropriate environmental conditions favour sporulation on grass host surfaces,the natural cycle for airborne conidia initiates,and large numbers of these conidia disperse as inoculum for new endophytic infections.Therefore,the cycle of endophytism may be an important link between climate,plant biology and public health.展开更多
Epichloëfestucae is an endophytic fungus that infects systemically the aerial tissues of the host grass Festuca rubra.This fungus is transmitted vertically from the mother plant to seeds.Hypothetically,the presen...Epichloëfestucae is an endophytic fungus that infects systemically the aerial tissues of the host grass Festuca rubra.This fungus is transmitted vertically from the mother plant to seeds.Hypothetically,the presence of E.festucae could affect the infection of a plant by other fungal species.This could occur if E.festucae metabolites produced in planta interfere negatively with other fungal infections;or alternatively,if the modulation of plant defenses by the endophyte favour further fungal infections.We have analyzed the presence of culturable non-systemic endophytes in plants of F.rubra infected(E+)and not infected(E−)by E.festucae in two subarctic habitats,meadows and riverbanks in Northern Finland.The observed non-systemic endophyte infection frequencies were similar among E+and E−plants from riverbanks,and E+plants from meadows.In contrast to these,the infection frequency was significantly lower in E−plants from meadows.This result suggests that the presence of E.festucae is not a main factor determining the presence of non-systemic endophytes in plants.Instead,plant genetic characteristics related to compatibility with E.festucae and other endophytes in the more stable meadow populations might play a role in these fungus–fungus–plant interactions.As a result of the survey,18 different taxa of non-systemic endophytes were identified in plants of F.rubra.All were ascomycetes except for one basidiomycete.Three endophytic taxa could not be ascribed to a genus,but sequence data indicated that they were conspecific with other unidentified endophytes that have been isolated in cold biomes at different locations.展开更多
文摘Most diversity restoration projects are not to improve diversity per se, but rather to enhance the presence and abundance of species that are characteristic of reference or target community. The use of Bromus inermis suppresses annual noxious grasses and increases the control of other-forb group these species are also noxious weeds;these may be substituted with another perennial species of the same functional group all through the whole experimental period, as it occurs with other perennial-forb Carduus tenuifolius. A field experiment was conducted on abandoned arable land with sown low and high diversity treatments and natural colonization following typical farming practice for the site. Experimental plots were installed on former agricultural land that had been cropped with (a rotation of) monocultures until the end of 1995. The experiment was organized according to a block design with five replicate blocks. An opposite trend was performed among the colonizer species, because the colonizer grasses were relegated by the high dominance of sown grasses. But at the same time, the sown grasses facilitated the dominance of other colonizer-forbs species;therefore its functional replacement in the community due to sown effect was again tested. However, in natural conditions the other-forbs group was the dominant group, without taking into account the stepping-stone treatment and there was also a functional change of dominance. Our study has demonstrated the restoration effectiveness of species richness at abandoned arable land and may be enhanced by sowing late successional species.
文摘Background: Can high diversity mixtures of later succession plant species be able to suppress early successional (arable weed) species than low diversity species mixtures? Can the removal of plant functional groups have important consequences on the sys-tem stability? Location: The study area was located at 850 m a.s.l., fifteen kilometers (15 km) to the west of Salamanca city, Spain, in a dehesa-like woodland. Methods: The field experiment was installed in Spring 1996 (May). The plots represented former agricultural lands cropped with (a rotation of) monocultures and abandoned right at the beginning of the experiment after the last crop was harvested in 1995. Before in-stalling plots, the fields were harrowed and equalized. The treatments (NC-natural colonization, LD-low diversity seed mixture and HD-high diversity seed mixture) were randomly allocated to the plots in each block. The experiment was organised accord-ing to a block design with five replicate blocks. Within each block, four plots measur-ing 10 × 10 m were marked out and each of the three treatments was randomly as-signed to one plot. All plots were separated by 2 m walkways. Results: The competitive ability of the sown species in different mixtures in LD, valued on the basis of their performance in HD, is a good predictor of their ability to suppress the weed crops spe-cies. This was also corroborated by the high relationship between the efficiency of the sown species in both treatments of species mixture (R<sup>2</sup> = 0.51, F (1, 33) = 34.56, P < 0.001). Conclusions: The increase of colonizing species cover was significantly lower in LD, which again supported the increase of biomass in 1998, being also lower in HD. Therefore, this increase in the community is more prominent in LD treatments. The effect of sown species was not so important in this increase.
文摘We report carbon stock in biomass, litter and soil estimated for six locations in natural Quercus ilex L. stands of the Middle and High Moroccan Atlas. Twenty trees at each location were selected according to their diameter classes and felled to measure the biomass of trunk, branches, twigs and leaves and determine allometric relationships. Soil was sampled in five depths (0 - 15, 15 - 30, 30 - 50, 50 - 70 and 70 - 100 cm) and litterfall production measured in all tree stands. The total carbon stock in above-ground biomass ranged between 17 Mg·haǃ in Aït Aamar stand (High Atlas) and 91 Mg·haǃ in Ksiba stand (Middle Atlas). Perennial organs (trunk, branches and twigs) stored over 95% of the tree carbon stock. Soil organic carbon concentrations ranged from 0.01% (in 70 - 100 cm in all stands) to 8.1% (in 0 - 15 cm in the Ajdir stand in Middle Atlas). The total organic carbon stock in the soil ranged between 141.4 t·haǃ in Ajdir and 24.6 t·haǃ in Asloul. The litter contained 0.2 Mg C haǃ in the clearing (C2) stand of High Atlas and 14.3 Mg C haǃ in (Ajdir) of carbon. The best fitted model for predicting carbon stock in tree biomass was obtained by applying the allometric equation Y = aXb for each biomass fraction and stand, where Y is the aboveground biomass (dry weight) and X is the DBH (Mean diameter at breast height, 1.30 m). These previous data obtained in the present study confirm the important function of these natural forests as longterm C sinks, in forest biomass, litter and soil. The potential long term C storage of these systems is moderately high, especially in less-intensively managed forests that include large trees. The established relationship between DBH and carbon stock in different tree organs can be used for forest carbon accounting, and also synthesize available information on oak forest as a sink for atmospheric CO2, and identify the management options that may enhance the capacity for C capture/ storage in forest soils.
文摘The dynamics of organic matter, carbon and nitrogen were studied during leaf decomposition over a three annual cycles period using the litterbag method at three permanently untilled and unfertilised plots. Our hypothesis is to determine if each litter type influences the decomposition and C and N releases from each other litter type （three plots and two species）. The main objective of this study is the comparison of decomposition dynamics in a climax forest with respect to that occurring in the chestnut managed plots on terrain suitable for oak to have further insight into the recycling of above ground organic matter and these two associated bioelements. As for the loss of dry matter, two-way analysis of variance, involving the treatment and year factors, revealed the existence of significant differences only for year, while no differences were observed for either treatment or interaction. At the end of the 2.4 years of the study, most of the treatment assays higher nitrogen concentrations than the initial ones were recorded. These three treatments the samplings prior to the last one revealed nitrogen concentrations higher than the initial ones, such that it may be concluded that the trend was towards an increase in concentration.
文摘A field experiment was carried out at the CSIC Muñovela farm belonging to the Spanish National Research Council (CSIC) in order to evaluate the effect of sowing orchard grass (Dactylis glomerata var. Trerano) and lucerne (Medicago sativa var. Aragon) in monoculture and in combination. The experiment was based on a randomized block designed with a factorial arrangement (5 × 2). Experimental units were 40 plots distributed in four blocks. The phosphorus fertilization (P) factor included two types of conditions: basal fertilization without phosphorus (-P) and basal fertilization with phosphorus (+P), and the vegetation cover factor (T) included five conditions depending on the grass (G) and the legume (L). Above-ground biomass showed statistically significant differences among seasons and years (P Lolium perenne L. and Poa pratensis L. throughout the three years indicated that both species significantly increased their presence over time regardless of the treatments applied. The analysis performed for the other plant species (those other than grasses and legumes) allowed us to determine that the T1 and T5 treatments, which correspond to single species not treated with the application of phosphorus, influenced the presence of 70% of other species planted. Our specific aim was to explore how changing plant biotic diversity affects productivity under a given set of conditions. We manipulated plant species richness as an experimental factor to determine if productivity would be affected by changes in the ratios of plants sown.
基金funded by Project AGL2011-22783,granted by the Spanish Government.
文摘Grasses represent one of the Earth’s most common plant groups,and natural and cultivated habitats dominated by grasses cover about 40%of the land surface.In turn,each grass species hosts multiple fungal species which can behave as endophytes.An analysis of the endophytic taxa identified in surveys conducted in 14 grass species showed that some of the most frequent taxa on each grass were also present across several host grasses.These taxa were Alternaria,Epicoccum,Cladosporium,Fusarium,and a few others.A similar analysis of airborne fungi surveyed at 41 different locations throughout the world showed that some of the most geographically widespread,and most locally frequent airborne fungi belonged to the same genera that are dominant endophytes in grasses(i.e.Cladosporium,Alternaria,Fusarium,etc.).Therefore,airborne spores of genera that are ubiquitous in grasses are common worldwide and attain high atmospheric concentrations.In addition,spores of the above mentioned fungi are also important respiratory allergens.Direct observation indicates that saprobic colonization and sporulation of non-systemic grass endophytes could become unrestrained when their host plant tissue dies.Subsequently,when appropriate environmental conditions favour sporulation on grass host surfaces,the natural cycle for airborne conidia initiates,and large numbers of these conidia disperse as inoculum for new endophytic infections.Therefore,the cycle of endophytism may be an important link between climate,plant biology and public health.
基金funding from INTERACT(grant agreement No.262693)under the European Community’s Seventh Framework Programme,from Academy of Finland(Project No.137909)Spanish Government(Project AGL2011-22783).
文摘Epichloëfestucae is an endophytic fungus that infects systemically the aerial tissues of the host grass Festuca rubra.This fungus is transmitted vertically from the mother plant to seeds.Hypothetically,the presence of E.festucae could affect the infection of a plant by other fungal species.This could occur if E.festucae metabolites produced in planta interfere negatively with other fungal infections;or alternatively,if the modulation of plant defenses by the endophyte favour further fungal infections.We have analyzed the presence of culturable non-systemic endophytes in plants of F.rubra infected(E+)and not infected(E−)by E.festucae in two subarctic habitats,meadows and riverbanks in Northern Finland.The observed non-systemic endophyte infection frequencies were similar among E+and E−plants from riverbanks,and E+plants from meadows.In contrast to these,the infection frequency was significantly lower in E−plants from meadows.This result suggests that the presence of E.festucae is not a main factor determining the presence of non-systemic endophytes in plants.Instead,plant genetic characteristics related to compatibility with E.festucae and other endophytes in the more stable meadow populations might play a role in these fungus–fungus–plant interactions.As a result of the survey,18 different taxa of non-systemic endophytes were identified in plants of F.rubra.All were ascomycetes except for one basidiomycete.Three endophytic taxa could not be ascribed to a genus,but sequence data indicated that they were conspecific with other unidentified endophytes that have been isolated in cold biomes at different locations.
