In many ecosystems ungulates have coexisted with grasslands over long periods of time. However, high densities of grazing animals may change the floristic and structural characteristics of vegetation, reduce biodivers...In many ecosystems ungulates have coexisted with grasslands over long periods of time. However, high densities of grazing animals may change the floristic and structural characteristics of vegetation, reduce biodiversity, and increase soil erosion, potentially triggering abrupt and rapid changes in ecosystem condition. Alternate stable state theory provides a framework for understanding this type of dynamic. In the Sanjiangyuan atop the Qinghai-Tibetan plateau (QTP), grassland degradation has been accompanied by irruptions of native burrowing animals, which has accentuated the loss of ground cover. Severely degraded areas of alpine meadows are referred to as 'Heitutan'. Here, using the framework of alternate stable state theory, we describe the proximate and ultimate drivers of the formation of Heitutan on the QTP, and we assess prospects for recovery, in relation to the degree of biophysical alteration, of these alpine meadows. Effective rehabilitation measures must address the underlying causes of degradation rather than their symptoms. Heitutan degradation is not uni-causal. Rather it reflects different mechanisms operating at different spatio-temporal scales across this vast region. Underlying causes include overly aggressive exploitation of the grasslands (e.g. overgrazing), amplification of grazing and erosion damage by small mammals when outbreaks occur, and/or climate change. Given marked variability in environmental conditions and stressors, restorative efforts must vary across the region. Restoration efforts are likely toyield greatest success if moderately and severely degraded areas are targeted as the first priority in management programmes, before these areas are transformed into extreme Heitutan.展开更多
Iterative linear programming methods are proposed for optimum balanced animal diet in this paper. According to ＂wooden bucket theory＂ of the nutritional balance, each nutrient in the feeding standard has equal impor...Iterative linear programming methods are proposed for optimum balanced animal diet in this paper. According to ＂wooden bucket theory＂ of the nutritional balance, each nutrient in the feeding standard has equal importance. It＇s unreasonable to use common goal programming to attach different weighted value to different nutritional parameters. This paper introduces an effective algorithm to deal with this kind of problem. When the permitting cost of livestock ration is given, we can design a ration formula with linear program-this is the first round. Then, according to the differences between the permitting cost and the formula cost gained in the first round, adjust the feeding standard and the feeding raw materials, and conduct the second round of linear programming for ration formula. If there is still a very big difference between the formula cost and the permitting cost, the third round will be taken, and so on. In this iteration course the formula cost gradually approaches the permitting cost. It is the key that the feeding standard and feeding raw materials are modified in each round. This method ensured the nutritive equilibrium with the formulation of least-cost ration. This is an especially important method when the primary goal of the optimization tool is to improve economic and nutritive efficiency.展开更多
This experiment was carried out to determine feed intake and digestibility of grazing sheep on pasture. A total of 14 animals randomly divided into two groups with seven animals each group were used in the experiment....This experiment was carried out to determine feed intake and digestibility of grazing sheep on pasture. A total of 14 animals randomly divided into two groups with seven animals each group were used in the experiment. Digestibility of pastures was determined using two types of markers-alkane （C32-C36） and chromium oxide. Dry matter intake （DMI） was 717.22 g/d based on chromium oxide method in the experiment, while according to alkane method, DMI was 965.93 g/d and 1,051.07 g/d for C32 and C36, respectively. In conclusion, pastures met 74%-81% of crude protein （CP） and 57%-61% of energy requirements of lambs grazing on Yuzuncu Yil University pasture, who are mid-quality and 4-7 month-old with a 275 g/d expected daily gain. It was calculated that when 628-693 g/d of barley is given, both CP and metabolizable energy （ME） requirements of animals can be met.展开更多
This study was carried out to investigate if on-farm cut vs. grazed pastures differed in soil fertility and species density in the temperate Himalayan highlands. Soil fertility and species relative density were measur...This study was carried out to investigate if on-farm cut vs. grazed pastures differed in soil fertility and species density in the temperate Himalayan highlands. Soil fertility and species relative density were measured from 30 cut and 30 grazed dairy pastures. In both types of pasture, soil pH, available phosphorus(P) and exchangeable potassium(K) were negatively correlated with pasture age and slope. In cut pasture, cocksfoot(Dactylis glomerata) and pasture age were positively correlated,whereas in grazed pasture, they were negatively correlated. In grazed pasture, unsown species and pasture age were positively correlated. Soil available P was significantly greater in cut pastures whereas soil exchangeable K was significantly greater in grazed pastures. In terms of species density, cut pasture had greater densities of cocksfoot and Italian ryegrass(Lolium multiflorum), whereas grazed pasture showed greater densities of white clover, sedge and local grass. Our study suggests that, if there are no improvements in the current method of pasture management, the cut pastures in the future are likely to have a simple pasture mixture constituting only cocksfoot and white clover(Trifolium repens).Whereas in grazed pasture, the pasture mixture is likely to be comprised of white clover and unsown species such as sedge, local grass and broadleaf weeds.展开更多
In this pape, almost periodic solution of a n-species Lotka-Volterra competition system with grazing rates and diffusions is investigated. By using the method of upper and lower solutions anti Schauder fixed point the...In this pape, almost periodic solution of a n-species Lotka-Volterra competition system with grazing rates and diffusions is investigated. By using the method of upper and lower solutions anti Schauder fixed point theorem as well as Lyapunov stability theory, we give sufficient conditions under which the strictly positive space homogeneous almost perilodic solution of the system is globally asymptotically stable. Moreover, some numerical simulations are given to validate our theoretical analysis.展开更多
Aims Species-rich plant communities are more resistant to invasions.In the past decade it was demonstrated that genetic variation also has many ecological effects.In our study we aimed to test whether the patterns of ...Aims Species-rich plant communities are more resistant to invasions.In the past decade it was demonstrated that genetic variation also has many ecological effects.In our study we aimed to test whether the patterns of response to the genetic diversity of a resident species differ between colonizing species of different growth forms and whether the response is affected by soil nutrients.Methods We established experimental stands of a common grass,Festuca rubra,harbouring three levels of genetic diversity(1,6 or 18 clonal genotypes,referred to as genotypic diversity)under two soil nutrient levels.In the fourth year after the stands were established,we sowed a mixture of four colonizers into the stands:a stoloniferous legume(Trifolium repens),a broad-leaf tussock grass(Anthoxanthum odoratum),a largerosette forb(Plantago lanceolata)and a small-rosette forb(Campanula rotundifolia).We observed species establishment and growth over 3 years.We tested whether colonization success depended on genotypic diversity,specific Festuca genotypes,soil nutrients and colonizer growth form.Important Findings The colonization success and biomass of the colonizers were significantly affected by the genotypic diversity and the genotype identity of the resident clonal grass.The response,however,differed between the colonizers.The strongest response to the genotypic diversity of the resident species was observed in the tussock grass with a growth form and architecture similar to the resident species.The large-rosette species responded in early stages of growth whereas the stoloniferous legume did not respond at all.The intraspecific genotypic diversity and genotype identity of the resident species play an important role in the assembly of plant communities.展开更多
基金supported by Special Fund for Agroscientific Research in the Public Interest(201203041)the National Natural Sciences Foundation of China(41161084)International Science & Technology Cooperation Program of China(2011DFG93160,2011DFA20820)
文摘In many ecosystems ungulates have coexisted with grasslands over long periods of time. However, high densities of grazing animals may change the floristic and structural characteristics of vegetation, reduce biodiversity, and increase soil erosion, potentially triggering abrupt and rapid changes in ecosystem condition. Alternate stable state theory provides a framework for understanding this type of dynamic. In the Sanjiangyuan atop the Qinghai-Tibetan plateau (QTP), grassland degradation has been accompanied by irruptions of native burrowing animals, which has accentuated the loss of ground cover. Severely degraded areas of alpine meadows are referred to as 'Heitutan'. Here, using the framework of alternate stable state theory, we describe the proximate and ultimate drivers of the formation of Heitutan on the QTP, and we assess prospects for recovery, in relation to the degree of biophysical alteration, of these alpine meadows. Effective rehabilitation measures must address the underlying causes of degradation rather than their symptoms. Heitutan degradation is not uni-causal. Rather it reflects different mechanisms operating at different spatio-temporal scales across this vast region. Underlying causes include overly aggressive exploitation of the grasslands (e.g. overgrazing), amplification of grazing and erosion damage by small mammals when outbreaks occur, and/or climate change. Given marked variability in environmental conditions and stressors, restorative efforts must vary across the region. Restoration efforts are likely toyield greatest success if moderately and severely degraded areas are targeted as the first priority in management programmes, before these areas are transformed into extreme Heitutan.
文摘Iterative linear programming methods are proposed for optimum balanced animal diet in this paper. According to ＂wooden bucket theory＂ of the nutritional balance, each nutrient in the feeding standard has equal importance. It＇s unreasonable to use common goal programming to attach different weighted value to different nutritional parameters. This paper introduces an effective algorithm to deal with this kind of problem. When the permitting cost of livestock ration is given, we can design a ration formula with linear program-this is the first round. Then, according to the differences between the permitting cost and the formula cost gained in the first round, adjust the feeding standard and the feeding raw materials, and conduct the second round of linear programming for ration formula. If there is still a very big difference between the formula cost and the permitting cost, the third round will be taken, and so on. In this iteration course the formula cost gradually approaches the permitting cost. It is the key that the feeding standard and feeding raw materials are modified in each round. This method ensured the nutritive equilibrium with the formulation of least-cost ration. This is an especially important method when the primary goal of the optimization tool is to improve economic and nutritive efficiency.
文摘This experiment was carried out to determine feed intake and digestibility of grazing sheep on pasture. A total of 14 animals randomly divided into two groups with seven animals each group were used in the experiment. Digestibility of pastures was determined using two types of markers-alkane （C32-C36） and chromium oxide. Dry matter intake （DMI） was 717.22 g/d based on chromium oxide method in the experiment, while according to alkane method, DMI was 965.93 g/d and 1,051.07 g/d for C32 and C36, respectively. In conclusion, pastures met 74%-81% of crude protein （CP） and 57%-61% of energy requirements of lambs grazing on Yuzuncu Yil University pasture, who are mid-quality and 4-7 month-old with a 275 g/d expected daily gain. It was calculated that when 628-693 g/d of barley is given, both CP and metabolizable energy （ME） requirements of animals can be met.
文摘This study was carried out to investigate if on-farm cut vs. grazed pastures differed in soil fertility and species density in the temperate Himalayan highlands. Soil fertility and species relative density were measured from 30 cut and 30 grazed dairy pastures. In both types of pasture, soil pH, available phosphorus(P) and exchangeable potassium(K) were negatively correlated with pasture age and slope. In cut pasture, cocksfoot(Dactylis glomerata) and pasture age were positively correlated,whereas in grazed pasture, they were negatively correlated. In grazed pasture, unsown species and pasture age were positively correlated. Soil available P was significantly greater in cut pastures whereas soil exchangeable K was significantly greater in grazed pastures. In terms of species density, cut pasture had greater densities of cocksfoot and Italian ryegrass(Lolium multiflorum), whereas grazed pasture showed greater densities of white clover, sedge and local grass. Our study suggests that, if there are no improvements in the current method of pasture management, the cut pastures in the future are likely to have a simple pasture mixture constituting only cocksfoot and white clover(Trifolium repens).Whereas in grazed pasture, the pasture mixture is likely to be comprised of white clover and unsown species such as sedge, local grass and broadleaf weeds.
基金This work is supported by Science and Technology Project of Chongqing Municipal Education Committee （Grant No. KJ 110501） of China, Natural Science Foundation Project of CQ CSTC （Grants No. CSTC2012jjA20016） of China and the NSFC （Grant Nos. 51005264, 11101298, 40801214） of China.
文摘In this pape, almost periodic solution of a n-species Lotka-Volterra competition system with grazing rates and diffusions is investigated. By using the method of upper and lower solutions anti Schauder fixed point theorem as well as Lyapunov stability theory, we give sufficient conditions under which the strictly positive space homogeneous almost perilodic solution of the system is globally asymptotically stable. Moreover, some numerical simulations are given to validate our theoretical analysis.
基金supported by the Czech Science Foundation(grant number 19-00522S)partly by a long-term research development project of the Academy of Sciences of the Czech Republic grant number RVO 67985939 and the Ministry of Education,Youth and Sports.
文摘Aims Species-rich plant communities are more resistant to invasions.In the past decade it was demonstrated that genetic variation also has many ecological effects.In our study we aimed to test whether the patterns of response to the genetic diversity of a resident species differ between colonizing species of different growth forms and whether the response is affected by soil nutrients.Methods We established experimental stands of a common grass,Festuca rubra,harbouring three levels of genetic diversity(1,6 or 18 clonal genotypes,referred to as genotypic diversity)under two soil nutrient levels.In the fourth year after the stands were established,we sowed a mixture of four colonizers into the stands:a stoloniferous legume(Trifolium repens),a broad-leaf tussock grass(Anthoxanthum odoratum),a largerosette forb(Plantago lanceolata)and a small-rosette forb(Campanula rotundifolia).We observed species establishment and growth over 3 years.We tested whether colonization success depended on genotypic diversity,specific Festuca genotypes,soil nutrients and colonizer growth form.Important Findings The colonization success and biomass of the colonizers were significantly affected by the genotypic diversity and the genotype identity of the resident clonal grass.The response,however,differed between the colonizers.The strongest response to the genotypic diversity of the resident species was observed in the tussock grass with a growth form and architecture similar to the resident species.The large-rosette species responded in early stages of growth whereas the stoloniferous legume did not respond at all.The intraspecific genotypic diversity and genotype identity of the resident species play an important role in the assembly of plant communities.
