Aesthetic Evaluation and Application of Ornamental Plant Landscape

This paper employed the scenic beauty evaluation(SBE)method to study the relationship between the aesthetic preference of the public and the effect of ornamental plant groups.The results showed that color contrast,plant density,morphological diversity,and species diversity significantly affected the planting effect of ornamental plants.According to the aesthetic preference of the public reflected by scenic beauty model,strong contrasts in plant color,varied plant forms,suitable planting density,and appropriate arrangement of plants effectively improved the ornamental effect of plant groups.

Changes in leaf stomatal traits of different aged temperate forest stands

Stomata control carbon and water vapor exchange between the leaves and the atmosphere,thus infl uencing photosynthesis and transpiration.Combinations of forest patches with different stand ages are common in nature,however,information of which stomatal traits vary among these stands and how,remains limited.Here,seven different aged forest stands(6,14,25,36,45,55,and 100 years)were selected in typical temperate,mixed broadleaf-conifer forests of northeast China.Stomatal density,size and relative area of 624 species,including the same species in stands of different ages were selected.Stomatal density,size and relative area were distributed log-normally,differing across all species and plant functional groups.Stomatal density ranged from 4.2 to 1276.7 stomata mm^(–2),stomatal size ranged from 66.6 to 8315.7μm^(2),and stomatal relative area 0.1–93.3%.There was a significant negative relationship between density and size at the species and functional group levels,while the relative stomatal area was positively correlated with density and size.Stomatal traits of dominant species were relatively stable across different stand ages but were significantly different for herbs.The results suggest that stomatal traits remain relatively stable for dominant species in natural forests and therefore,spatial variation in stomatal traits across forest patches does not need to be incorporated in future ecological models.

Self-stabilizing maintenance process in plant communities of alpine meadows under different grazing intensities

Backgrounds:Grazing prohibition and reduced grazing intensity,as two important“vegetation close-to-nature recovery”methods,have been suggested as economical and effective technologies for enhancing forage production.However,numerous studies have found that the yield of forage could be increased by removing or reducing grazing in a short time in some steady stage of alpine Kobresia meadows,but not in others.To reveal the mechanism behind this phenomenon,we proposed a series of experiments.Methods:We monitored the plant and soil characteristics in the key steady stages of Kobresia meadows under reduced and prohibited grazing conditions in the same geographic and climatic environments in the northeastern Qinghai-Tibet Plateau for 6 years.We estimated the relationships between the plant community and soil nutrients and obtained the following results.Results:All measured variables were positively correlated with each other.The plant community structure had higher path coefficients to aboveground biomass,soil organic matter,total nitrogen,and nitrate nitrogen than to other factors.The plant community structure played an important role in response to grazing intensity.Different plant functional groups(PFGs)had different responses to grazing intensity,which led to plant community re-establishment or re-organization under different grazing intensities.Poaceae and Kobresia were more sensitive to grazing intensity than other PFGs,and the ratio of Kobresia biomass(including Kobresia humilis and Kobresia pygmaea)to the total biomass of Poaceae and Kobresia could be used as an indicator of regime shifts within plant communities.With Kobresia pygmaea as the dominant species,the prohibition of grazing was not an efficient approach to increase the yield in the steady stages because this treatment needed more time to recover aboveground biomass.If Poaceae is the dominant PFG,grazing should only be prohibited for 3 years in the steady stages because the aboveground biomass will decrease if grazing is prohibited for more than 3 years.Conclusions:Therefore,the different steady stages of alpine meadows require different recovery methods to increase recovery efficiency and speed.

Climate change-driven shifts in plant–soil feedbacks:a meta-analysis

Background:Climate change is expected to affect plant–soil feedbacks(PSFs,i.e.,the effects of a plant on the growth of another plant or community grown in the same soil via changes in soil abiotic and biotic properties),influencing plant community dynamics and,through this,ecosystem functioning.However,our knowledge of the effects of climate changes on the magnitude and direction of PSFs remains limited,with considerable variability between studies.We quantified PSFs associated with common climate change factors,specifically drought and warming,and their corresponding ambient(control)conditions using a meta-analytical approach.We investigated whether drought and warming effects on PSFs were consistent across functional groups,life histories(annual versus perennial)and species origin(native versus non-native),planting(monoculture,mixed culture)and experimental(field,greenhouse/laboratory)conditions.Results:PSFs were negative(a mechanism that encourage species co-existence)under drought and neutral under corresponding ambient conditions,whereas PSFs were negative under both ambient and elevated temperatures,with no apparent difference in effect size.The response to drought was largely driven by stronger negative PSFs in grasses,indicating that grasses are more likely to show stronger negative PSFs than other functional groups under drought.Moreover,non-native species showed negative drought-induced PSFs while native species showed neutral PSFs under drought.By contrast,we found the opposite in pattern in response to warming for native and non-native species.Perennial herbs displayed stronger drought-induced negative PSFs than annual herbs.Mixed species communities displayed more negative PSFs than monocultures,independent of climate treatment.Finally,warming and drought treatment PSF effect sizes were more negative in experiments performed in the field than under controlled conditions.Conclusions:We provide evidence that drought and warming can induce context-specific shifts in PSFs,which are dependent on plant functional groups,life history traits and experimental conditions.These shifts would be expected to have implications for plant community dynamics under projected climate change scenarios.

Mowing and fertilizer effects on seedling establishment in a successional old field

Aims We used a 10-year field experiment that consisted of mowing and fertilizer treatments to evaluate the role of niche limitation in seedling establishment of species from different functional groups and of varying local abundance in an old field undergoing succession.Methods Seedlings of nine different species were planted into a successional field subjected to mowing and fertilizer treatments for 10 years that resulted in different plant communities and resource availability.Species representative of the factorial combination of three functional groups(C4 grasses,C3 grasses and legumes)and three abundance categories(abundant,present,or absent in the old field)were planted in four treatments resulting from the factorial combination of annual spring mowing(mowed and unmowed)and fertilizer application(annually fertilized and unfertilized).Survivorship,relative growth rate(RGR)and biomass were measured to determine the role of niche limitation on recruitment and growth.Important Findings Mowing increased the establishment success of seedlings.Fertilization had little influence on seedling performance and survivorship.C3 grasses had the highest survivorship,while C4 grasses and legumes had equivalent RGRs,but higher than C3 grasses.By contrast,survivorship of legumes was unrelated to mowing or fertilizer,suggesting that establishment of this functional group was dependent on other,unmeasured conditions or processes.Species already present,but at low abundance,performed better than locally abundant or absent species.Propagule limitation may restrict the arrival of a species.However,recruitment and establishment was subject to niche limitation,which varied among species,functional groups and whether a species is already resident at the site and its abundance.Thus,species interactions restrict establishment during old-field succession,supporting the niche limitation hypothesis.

Unexpected ecotone dynamics of a sand dune vegetation complex following water table decline

Aims Central Hungarian inland dune ranges harbor heterogeneous grassland vegetation with an extensive network of ecotones,arranged perpendicular to topography-driven hydrologic gradients.The area suffers from severe aridification due to climate change and local anthropogenic factors,which have led to a dramatic decline of the water table.As a result,groundwater is no longer reachable for lowlying plant communities;thus,we expect they are bound to undergo profound changes.This study investigates how the plant communities respond to this changing environment over time by monitoring ecotones,since they are frequently the hotspots of ecosystem change.We monitored five ecotones along permanent belt transects for 15 years to characterize their dynamic response,and to identify the internal structural changes of the plant communities the ecotones delimit.Methods Ecotones were delineated with the split moving window technique.The dynamics of two ecotone parameters,location and contrast,were analyzed with linear regression models incorporating two independent variables:study year as a measure of time since the loss of groundwater,and precipitation as a possible driver of interannual variations.The internal changes of the patches separated by the ecotones were analyzed using plant functional groups.Important Findings Precipitation had no detectable effect on the ecotone descriptors,but study year influenced ecotones in an unusual fashion.The position of the ecotones appeared to be very stable in time;their dynamics are stationary,not directional as we predicted.The contrasts had clear tendencies;two ecotones disappeared,one new one was formed and two ecotones showed no trend.The internal changes of the patches over time were dramatic,showing a shift toward more xeric and more open plant assemblages in most stretches of the transects.Thus,the dynamic response of the vegetation was not patch expansion vs.shrinking,but fusion vs.division,which profoundly restructured the vegetation pattern.Analysis of plant functional groups revealed that the trends of the ecotone contrasts could be traced back to internal changes of the patches and not to processes within ecotones.Hence,in situations where stationary ecotone dynamics prevail,ecotone position may be a poor indicator of the effects of strong directional environmental changes.However,in this study we show that ecotone contrast can serve as a sensitive tool for monitoring landscape pattern transformations in these cases.Also,this highlights the long-term nature of ecotone responses,which can have implications in landscape planning and restoration measures.