The Combined Application of WTP and WTA in Contingent Valuation Methods

The In most contingent valuation (CV) studies, WTP (Willingness to pay) and WTA (Willingness to accept) were often used separately, so protesting or no response or even babbling answers are increasing, and the debate persists over the reliability of CV in economic policy analysis. In order to improve the reliability of CV, WTP and WTA is used syn-chronously to estimate the restoration cost of Maqu grassland ecosystem. Data were partly from questionnaire survey, and partly from interviews and authorities. Before conclusions were derived, we assumed these data that came from interviews and authorities were right. The main result is: If we assumed that the degraded grassland of Maqu needs 10 years to be restored, and divided the restoring period into two stages, then the restoration cost was 0.85 × 108 RMB per year in former 4 years, 0.022 × 108 RMB per year in latter 6 years. The total cost of Maqu grassland restoration was 3.62 × 108 RMB. For all the costs of restoration, WTA occupied 94% and WTP only occupied 6%, suggesting that local grassland degradation was mainly caused by overgrazing and that the overloading livestock must be eliminated in order to achieve restoration successfully. Our research also showed that combining WTP and WTA in contingent valuation is very useful in estimating the cost of environmental improvement projects. Of course, whether these results are right or not, further researches are needed in the future, especially for the actual number of livestock in Maqu grassland.

comLinking flowering and reproductive allocation in response to nitrogen addition in an alpine meadow

Aims Plants can change in phenology and biomass allocation in response to environmental change.It has been demonstrated that nitrogen is the most limiting resource for plants in many terrestrial ecosystems.Previous studies have usually focused on either flowering phenology or biomass allocation of plants in response to nitrogen addition;how-ever,attempts to link flowering phenology and biomass allocation are still rare.In this study,we tested the effects of nitrogen addition on both flowering phenology and reproductive allocation in 34 common species.We also examined the potential linkage between flowering time and reproductive allocation in response to nitrogen addition.Methods We conducted a 3-year nitrogen addition experiment in Tibetan alpine meadow.We measured first flowering date and the repro-ductive allocation for 34 common plant species in control,low and high nitrogen added plots,respectively.one-way analysis of variance was used to examine differences of first flowering date and reproductive allocation among treatments.The relationships between the change in species first flowering date and change in reproductive allocation in response to nitrogen addition were examined by calculating Pearson correlation coefficients.Important Findings For most species,both first flowering date and reproductive alloca-tion significantly responded to nitrogen addition.Nitrogen addition significantly delayed the first flowering date and reduced the repro-ductive allocation for all graminoid species,but accelerated flower-ing and increased reproductive allocation for most forb species.We found that changes in first flowering date significantly negatively correlated with the changes in reproductive allocation over spe-cies in response to nitrogen,which indicated a positive relationship between flowering response and plant performance in reproductive allocation.species that advanced their flowering time with nitrogen addition increased their reproductive allocation,whereas those that delayed flowering time tended to decline in reproductive allocation with nitrogen addition.our results suggest that species-specific switch from vegetative growth to reproductive growth could influence species performance.

Community-level trait responses and intra-specific trait variability play important roles in driving community productivity in an alpine meadow on the Tibetan Plateau

Aims Human activities have dramatically increased nutrient inputs to ecosys-tems,impacting plant community diversity,composition and function-ing.Extensive research has shown that a decrease in species diversity and an increase in productivity are a common phenomenon following fertilization in grasslands ecosystem.The magnitude of the response of species diversity and above-ground net primary productivity(ANPP)to fertilization mainly depends on species traits(mean trait values)and traits variability(plasticity).Our aim of this study was to examine(i)changes of species diversity(species richness and Shannon-Wiener index)and ANPP following fertilization;(ii)which species traits or community-weighted mean(CWM)traits can determine ANPP,as expected from the‘biomass ratio hypothesis’;and(iii)the relative role of intra-specific and inter-specific trait variability in this process following fertilization.Methods We measured ANPP and four key plant functional traits:specific leaf area(SLA),leaf dry matter content(LDMC),mature plant height(MPH)and leaf nitrogen concentration(LNC)for 25 component species along a fertilization gradient in an alpine meadow on the Tibetan Plateau.In addition,trait variation of species was assessed using coefficients of variation(CV),and we calculated the ratio of the CVintra to the CVinter.Important Findings Our results showed that:(i)fertilization significantly reduced species richness and Shannon-Weiner diversity index,but sig-nificantly increased ANPP;(ii)there was a significant positive correlation between ANPP and CWM-SLA and CWM-MPH,yet there was no significant relationship between ANPP and CWM-LNC or CWM-LDMC;(iii)intra-specific variability in SLA and MPH was found to be much greater than inter-specific variability,especially at the higher fertilization levels.We con-cluded that CWM-SLA and CWM-MPH can be used to assess the impacts of species changes on ecosystem functioning,and dominant species can maximize resource use through intra-spe-cific variability in SLA and MPH to compensate for the loss of species following fertilization,therefore maintaining high com-munity productivity.

Root–shoot competition interactions cause diversity loss after fertilization:a field experiment in an alpine meadow on the Tibetan Plateau

Aims A decrease in species diversity after fertilization is a common phenomenon in grasslands;however,the mechanism causing it remains highly controversial.The light competition hypothesis to explain loss of diversity has received much attention.The aim of the present paper was to test this hypothesis.Methods Fertilization was used to control above-and belowground resources simultaneously,while shade was used to control aboveground resource in an alpine meadow on the Tibetan Plateau.Univariate general linear models was used to estimate the effects of fertilization and shade on above-and belowground vegetation characteristics,including photosynthetically active radiation(PAR)in the understory,aboveground biomass,belowground biomass,R:S ratio,species richness and Simpson’s diversity index.Important findings PAR was similar in the understory of shaded and fertilized plots,but only fertilization reduced species richness and diversity,suggesting that light competition alone could not explain diversity loss after fertilization.The root biomass and R:S ratio had a significant increase in shaded plots,but the richness and diversity did not change,suggesting that root competition alone also could not explain diversity loss after fertilization in this community.Our results illustrated that the root–shoot competition interactions,investigated from a functional groups perspective,should be the most reasonable explanation leading to the diversity loss due to fertilization.

The effects of fertilization on the trait-abundance relationships in a Tibetan alpine meadow community

Aims Comparisons of the trait-abundance relationships from various habitat types are critical for community ecology,which can offer us insights about the mechanisms underlying the local community assembly,such as the relative role of neutral vs.niche processes in shaping community structure.Here,we explored the responses of trait-abundance relationships to nitrogen(N),phosphorus(P)and potassium(K)fertilization in an alpine meadow.Methods Five fertilization treatments(an unfertilized control and additions of N,P,K and NPK respectively)were implemented using randomized block design in an alpine Tibetan meadow.Species relative abundance(SRA),plant above-ground biomass and species richness were measured in each plot.For 24 common species,we measured species functional traits:saturated height,specific leaf area(SLA)and leaf dry matter content(LDMC)in each treatment but seed size only in the unfertilized control.Standard major axis(SMA)regression and phylogenetically independent contrasts(PICs)analysis were used to analyse species trait-abundance relationships in response to different fertilization treatments.Important Findings Positive correlations between SRA and saturated height were raised following N,P and NPK fertilizations,which indicated an increase in light competition in these plots.In P fertilized plots,SRA was also positively correlated with LDMC because tall grasses with a nutrients conservation strategy often have a relative competitive advantage in capturing limited light and soil nutrients.In K fertilized plots,neither the trait-abundance relationships nor above-ground biomass or species richness significantly differed from that in the control,which suggests that K was not a limiting resource in our study site.These significant correlations between species traits and relative abundance in fertilized treatment suggest that trait-based selection plays an important role in determining species abundance within local communities in alpine meadows.

Effects of enhanced UV-B radiation on fitness of an alpine species Cerastium glomeratum Thuill

Aims Information about how species respond to extreme environments,such as high UV-B radiation,is very useful in estimating natural ecosystem structure and functions in alpine areas.Our aim is to examine the effect of enhanced UV-B radiation on the fitness of an alpine meadow annual species on Qinghai-Tibet Plateau.Methods Plants of Cerastium glomeratum Thuill.were exposed to ambient(control)or ambient plus supplemental UV-B radiation(enhanced),simulating a 9%ozone depletion over Gannan,China(102
53#E,34
55#N,2900 m in altitude),up to leaf senescence and fruit maturation.Plant height,flower phenology,biomass allocation and reproductive parameters of the species were measured.Important findings Plant height in C.glomeratum was reduced by enhanced UV-B radiation at early growth stages and compensated with ongoing development.Fruit biomass,aboveground biomass,total biomass and reproductive effort(fruit dry mass/aboveground biomass)were not affected by enhanced UV-B radiation,but a significant increase in root/shoot ratio was found.Enhanced UV-B radiation delayed onset of flowering by 1 day and shortened duration of flowering by 5 days in C.glomeratum.But because of the long period of flowering time(83–88 days),this did not make any significant effect on flower number,seed number,pollination success(number of seeds per fruit)or reproductive success(fruit to flower ratio)in C.glomeratum.Enhanced UV-B radiation had no effect on seed germination and seed mass either.And the high production and low germination rate of the seed might be the strategy of C.glomeratum to survive the extreme environments on alpine meadow.All these results showed that C.glomeratum was tolerant to enhanced UV-B radiation.

Seed germinating characteristics of 54 gramineous species in the alpine meadow on the eastern Qinghai-Tibet plateau

The germination experiment was started on March 3,2004,and seeds were collected from July to October in 2003.We analyzed the percentage of germination,days to first germination,germination period and days to 50%germination.Among the 54 examined species,26 species exceeded 80%germination,11 species exceeded 60%–80%germination,8 exceeded 40%–0%,5 exceeded 20%–40%,and 4 showed less than 20%.A principalcomponent analysis revealed that the species were distributed along two statistically independent axes,the first primarily represented the germination rate and the second represented the time of germination process.Based on scores of germination characteristics,cluster analysis of the 54 gramineous species could be divided into 4 distinct groups:rapid,slow,intermediate germinating(germination percentage>50%),and low germinating(germination percentage<50%).The meaning of different groups to the vegetation regeneration was discussed.

Short-term responses of an alpine meadow community to removal of a dominant species along a fertilization gradient

Aims The relationship between biodiversity and ecosystem functioning has intrigued ecologists for several decades,but the effect of loss of a dominant species on community structure and functioning along a nutrient gradient remains poorly understood.The aim of this paper was to test the effect of a dominant species on community structure and function by conducting a species removal experiment along a fertilization gradient.Methods We removed the population of a dominant species(Elymus nutans)in a long-term fertilization field in an alpine meadow on the Tibetan Plateau,China.univariate general linear models were used to evaluate the effects of fertilization and removal on above-ground vegetation characteristics,including photosynthetically active radiation in the understory,species richness,shannon-Weiner diversity index,simpson’s dominance index,above-ground biomass(includ-ing different functional groups)and seedling richness and density.Important Findingsresults revealed that after two plant growing seasons,there was no significant effect of the removal of a dominant species on species richness and diversity of the remaining vegetation,but the biomass of forbs and seedling recruitment were significantly increased indicative of the potential for long-term effects.moreover,removal had a large effect at high fertilization levels,but little effect when fertilization levels were low.our studies indicated that community response to loss of a dominant species was mainly dependent on resource availability and the remaining functional group identities.We also found seedling recruitment was usually more sensitive to the influence of competition of dominant species than the estab-lished vegetation in the short term.

Increased community compositional dissimilarity alleviates species loss following nutrient enrichment at large spatial scales

Aims Anthropogenic activities have drastically increased nutrient availabil-ity,resulting in declines in species richness in many plant communi-ties.However,most previous studies have explored only species-loss patterns and mechanisms over small sampling areas,so their results might overestimate species loss at larger spatial scales.The aim of this research was to explore species diversity change patterns and species-loss rates at multiple scales in alpine meadow communities following nutrient enrichment.Specifically,we asked two closely related ques-tions:(i)do changes in species diversity and species-loss patterns differ among spatial scales?and(ii)how does community compositional dissimilarity and species turnover change among spatial scale?Methods This study was implemented in an alpine meadow community,which is regarded as one of the most sensitive and vulnerable ter-restrial ecosystems to anthropogenic nutrient enrichment.We conducted a fertilization experiment that involved the addition of nitrogen(N),phosphorus(P)and a mixture of both to a series of quadrats ranging from 1 to 16 m2 over 5 years to study the variations in the patterns of species diversity in response to nutrient additions at different spatial scales.Important Findings Our results showed that the changes in species diversity and species loss were dependent on the type of fertilization and the spatial scale.After N and NP fertilization,species diversity significantly decreased at the small scale but not at the large scale,and the rate of species loss decreased as the spatial scale increased.In contrast,the differences between the P addition and control communities were negligible at both the small and large spatial scales.N fertilization caused species to be lost from the small sampling scale,but because different species were lost from dif-ferent samples,there was an increase in compositional dissimilarity at larger spatial scales,which reduced the total number of species lost when measured at larger scales.These findings highlight spatial scale in evalu-ating the biodiversity loss after fertilization and suggest that the compo-sitional dissimilarity might play an important role in mediating species loss after fertilization.Our study significantly improved our understanding of changes in species diversity and species loss at different spatial scales under nutrient-enrichment scenarios.

Structural,compositional and trait differences between the mature and the swamp meadow communities

Aims The mature meadows(MMs)and the swamp meadows(SMs)are the two most important ecosystems in the eastern Tibetan Plateau,China.Besides their substantial differences in terms of soil water conditions and thereby the soil oxygen and nutrients,however,little is known about the differences in community composition,struc-ture,traits and productivity between these two meadows.We par-ticularly ask whether light availability mediated by physical structure heterogeneity is a key determinant of the difference in community composition and productivity between these two meadows.Methods We examined the community structure,composition,aboveground net primary productivity(ANPP),light availability in understory and the community-weighted means(CWMs)for leaf morphological and physiological traits in 12 random plots(5 m×5 m)for each of the studied habitats.Important findings The results showed that plant community in the MM had higher variation in both vertical and horizontal structure and thus had more light availability in the understory.The MM had higher spe-cies richness and greater ANPP than the SM.The CWMs of leaf morphological and physiological traits for species in the MM fea-tured a fast-growing strategy(i.e.higher height,leaf area and net photosynthesis rate and lower nitrogen:phosphorus ratio),in con-trast to those in the SM.We also found that there were significant correlations between the CWM of traits and the ANPP,indicating that some key traits in these habitats have linked to community productivity.Our study also suggests that the heterogeneity in the community structure,which affects light availability in the under-story,may play an important role in determining the community composition and productivity.In conclusion,our study revealed significant differences in community structure,composition and traits between the MM and the SM,and the light availability that related closely to community structure is the key factor to deter-mine the composition and productivity of the community of these two habitats.