Guofang Liu

Coordinated variation in leaf and root traits across multiple spatial scales in Chinese semi-arid and arid ecosystems.

• Variation in plant functional traits is the product of evolutionary and environmental drivers operating at different scales. Little is known about whether, or how, this variation is coordinated between aboveground and belowground organs across and within spatial scales. • We address these questions using a hierarchically designed dataset of pairwise leaf and root traits related to carbon and nutrient economy of 64 species belonging to 14 plant communities in northern Chinese semi-arid and arid regions. • While both root and leaf traits showed most of their variance among (individuals and) species within communities, leaf trait variance tended to be relatively higher at coarser spatial scales than root trait variance. While leaf nitrogen (N) per area to root N per length ratio increased and specific leaf area to specific root length and leaf [N] to root [N] ratios decreased from semi-arid to arid environments owing to climatic/edaphic shifts, the matching pairs showed a strong pattern of positive correlation that was upheld across spatial scales and geographic areas. • Thus, trade-offs in plant resource investment across organs within individual vascular plants are constrained within a rather narrow range of variation. A new challenge will be to test whether and how such trait coordination is also seen within and across other biomes of the world.

Clonality-Climate Relationships along Latitudinal Gradient across China: Adaptation of Clonality to Environments

Plant clonality, the ability of a plant species to reproduce itself vegetatively through ramets (shoot-root units), occurs in many plant species and is considered to be more frequent in cold or wet environments. However, a deeper understanding on the clonality-climate relationships along large geographic gradients is still scarce. In this study we revealed the clonality-climate relationships along latitudinal gradient of entire China spanning from tropics to temperate zones using clonality data for 4015 vascular plant species in 545 terrestrial communities. Structural equation modeling (SEM) showed that, in general, the preponderance of clonality increased along the latitudinal gradient towards cold, dry or very wet environments. However, the distribution of clonality in China was significantly but only weakly correlated with latitude and four climatic factors (mean annual temperature, temperature seasonality, mean annual precipitation, precipitation seasonality). Clonality of woody and herbaceous species had opposite responses to climatic variables. More precisely, woody clonality showed higher frequency in wet or climatically stable environments, while herbaceous clonality preferred cold, dry or climatically instable environments. Unexplained variation in clonality may be owed to the influences of other environmental conditions and to different clonal strategies and underlying traits adopted by different growth forms and phylogenetic lineages. Therefore, in-depth research in terms of more detailed clonal growth form, phylogeny and additional environmental variables are encouraged to further understand plant clonality response to climatic and/or edaphic conditions.

Functional traits drive the contribution of solar radiation to leaf litter decomposition among multiple arid-zone species

In arid zones, strong solar radiation has important consequences for ecosystem processes. To better understand carbon and nutrient dynamics, it is important to know the contribution of solar radiation to leaf litter decomposition of different arid-zone species. Here we investigated: (1) whether such contribution varies among plant species at given irradiance regime, (2) whether interspecific variation in such contribution correlates with interspecific variation in the decomposition rate under shade; and (3) whether this correlation can be explained by leaf traits. We conducted a factorial experiment to determine the effects of solar radiation and environmental moisture for the mass loss and the decomposition constant k-values of 13 species litters collected in Northern China. The contribution of solar radiation to leaf litter decomposition varied significantly among species. Solar radiation accelerated decomposition in particular in the species that already decompose quickly under shade. Functional traits, notably specific leaf area, might predict the interspecific variation in that contribution. Our results provide the first empirical evidence for how the effect of solar radiation on decomposition varies among multiple species. Thus, the effect of solar radiation on the carbon flux between biosphere and atmosphere may depend on the species composition of the vegetation.

Understanding the ecosystem implications of the angiosperm rise to dominance: leaf litter decomposability among magnoliids and other basal angiosperms

Litter decomposition has been a key driver of carbon and nutrient cycling in the present and past. Based on extant species data, there is a great deal of variation in litter decomposability among major plant lineages, suggesting potential shifts in plant effects on carbon and nutrient cycling during the early evolutionary history of angiosperms. Existing data suggest that eudicot species produce faster decomposing litter compared to gymnosperms, ferns and mosses. One of the missing puzzle pieces in this transition is the basal angiosperms, the functional role of which in past carbon and nutrient cycling has seldom been investigated. We hypothesized that owing to constraints on leaf and plant design related to hydraulic capacity, basal angiosperm trees should generally have resource conservative leaves of low decomposability and that fast-decomposing leaves may only be found in short-statured taxa. We performed a litterbag experiment with simultaneous outdoor incubation of leaf litters in a common environment, including 86 basal angiosperm species (including the magnoliid lineage), 33 eudicots, five gymnosperms and four ferns. We fit a nonlinear model to the decomposition data, and each speciesr decomposability was estimated using the proportional rate of mass loss through the experiment. The mass loss rates were 59.2% lower in basal angiosperms than in eudicot trees. There was one exceptional group within basal angiosperms: the Piperales had higher k values than other magnoliid lineages, but all of the free-standing species were short. Eudicots had higher k values overall and covered a range of plant statures from small-statured herbs to big woody trees. Synthesis. Understanding the ecosystem-level effects of the angiosperm rise to dominance is a crucial goal. Our results indicated that, among generally slow-decomposing magnoliid lineages, only the Piperales have fast decomposition rate associated with small plant statures. Thus it is unlikely that early magnoliid trees were both forest canopy dominants and produced resource acquisitive leaves turning into fast decomposable litter during the evolutionary history of angiosperms.

Plant functional diversity and species diversity in the Mongolian steppe.

Background The Mongolian steppe is one of the most important grasslands in the world but suffers from aridization and damage from anthropogenic activities. Understanding structure and function of this community is important for the ecological conservation, but has seldom been investigated. Methodology/Principal Findings In this study, a total of 324 quadrats located on the three main types of Mongolian steppes were surveyed. Early-season perennial forbs (37% of total importance value), late-season annual forbs (33%) and late-season perennial forbs (44%) were dominant in meadow, typical and desert steppes, respectively. Species richness, diversity and plant functional type (PFT) richness decreased from the meadow, via typical to desert steppes, but evenness increased; PFT diversity in the desert and meadow steppes was higher than that in typical steppe. However, above-ground net primary productivity (ANPP) was far lower in desert steppe than in the other two steppes. In addition, the slope of the relationship between species richness and PFT richness increased from the meadow, via typical to desert steppes. Similarly, with an increase in species diversity, PFT diversity increased more quickly in both the desert and typical steppes than that in meadow steppe. Random resampling suggested that this coordination was partly due to a sampling effect of diversity. Conclusions/Significance These results indicate that desert steppe should be strictly protected because of its limited functional redundancy, which its ecological functioning is sensitive to species loss. In contrast, despite high potential forage production shared by the meadow and typical steppes, management of these two types of steppes should be different: meadow steppe should be preserved due to its higher conservation value characterized by more species redundancy and higher spatial heterogeneity, while typical steppe could be utilized moderately because its dominant grass genus Stipa is resistant to herbivory and drought.

Effects of rainfall pattern on the growth and fecundity of a dominant dune annual in a semi-arid ecosystem

AimsCurrent and future changes in rainfall patterns – amount and frequency – may particularly impact annual plants in semi-arid ecosystems. The aim of this study was to investigate how changes in rainfall patterns affect the growth and fecundity of sand dune annuals.MethodsThe effects of gradients in five rainfall amounts and five frequencies, based on historical and predicted values, on growth and fecundity of Agriophyllum squarrosum, a dominant annual in Mu Us Sandland, were examined in the near natural habitat.ResultsRainfall amount and frequency significantly affected all vegetative and reproductive traits. With decreased amount of rainfall, height, biomass, seed number, seed mass and reproductive effort decreased, while root/shoot ratio increased. Except for the two extreme frequencies (1- and 120-day intervals), values of all vegetative and reproductive traits increased with the increase of rainfall frequencies. Germinability of offspring seeds tended to increase with increasing aridity, suggesting that a maternal effect may have been present.ConclusionsOur study shows that the plastic response in growth and fecundity of A. squarrosum to rainfall fluctuation allows the plant to survive and reproduce under current unpredictable environments as well as the increased variability predicted with climate change in semi-arid regions.

Novel evidence for within-species leaf economics spectrum at multiple spatial scales

Leaf economics spectrum (LES), characterizing covariation among a suite of leaf traits relevant to carbon and nutrient economics, has been examined largely among species but hardly within species. In addition, very little attempt has been made to examine whether the existence of LES depends on spatial scales. To address these questions, we quantified the variation and covariation of four leaf economic traits (specific leaf area, leaf dry matter content, leaf nitrogen and phosphorus contents) in a cosmopolitan wetland species (Phragmites australis) at three spatial (inter-regional, regional, and site) scales across most of the species range in China. The species expressed large intraspecific variation in the leaf economic traits at all of the three spatial scales. It also showed strong covariation among the four leaf economic traits across the species range. The coordination among leaf economic traits resulted in LES at all three scales and the environmental variables determining variation in leaf economic traits were different among the spatial scales. Our results provide novel evidence for within-species LES at multiple spatial scales, indicating that resource trade-off could also constrain intraspecific trait variation mainly driven by climatic and/or edaphic differences.

Experimental evidence that the Ornstein-Uhlenbeck model best describes the evolution of leaf litter decomposability.

Leaf litter decomposability is an important effect trait for ecosystem functioning. However, it is unknown how this effect trait evolved through plant history as a leaf ‘afterlife’ integrator of the evolution of multiple underlying traits upon which adaptive selection must have acted. Did decomposability evolve in a Brownian fashion without any constraints? Was evolution rapid at first and then slowed? Or was there an underlying mean-reverting process that makes the evolution of extreme trait values unlikely? Here, we test the hypothesis that the evolution of decomposability has undergone certain mean-reverting forces due to strong constraints and trade-offs in the leaf traits that have afterlife effects on litter quality to decomposers. In order to test this, we examined the leaf litter decomposability and seven key leaf traits of 48 tree species in the temperate area of China and fitted them to three evolutionary models: Brownian motion model (BM), Early burst model (EB), and Ornstein-Uhlenbeck model (OU). The OU model, which does not allow unlimited trait divergence through time, was the best fit model for leaf litter decomposability and all seven leaf traits. These results support the hypothesis that neither decomposability nor the underlying traits has been able to diverge toward progressively extreme values through evolutionary time. These results have reinforced our understanding of the relationships between leaf litter decomposability and leaf traits in an evolutionary perspective and may be a helpful step toward reconstructing deep-time carbon cycling based on taxonomic composition with more confidence.

Correlated biogeographic variation of magnesium across trophic levels in a terrestrial food chain.

Using samples from eastern China (c. 25 – 41° N and 99 – 123° E) and from a common garden experiment, we investigate how Mg concentration varies with climate across multiple trophic levels. In soils, plant tissue (Oriental oak leaves and acorns), and a specialist acorn predator (the weevil Curculio davidi), Mg concentration increased significantly with different slopes from south to north, and generally decreased with both mean annual temperature (MAT) and precipitation (MAP). In addition, soil, leaf, acorn and weevil Mg showed different strengths of association and sensitivity with climatic factors, suggesting that distinct mechanisms may drive patterns of Mg variation at different trophic levels. Our findings provide a first step toward determining whether anticipated changes in temperature and precipitation due to climate change will have important consequences for the bioavailability and distribution of Mg in food chain.

Restoration of Degraded Ecosystem

Ecosystem is the most complete basic structure and functional unit for the research of ecology and other branches, so ecosystem restoration is the basis of different levels of ecological restoration research, and the research and practice of ecological restoration should take ecosystem as the basic object. The theme for the International Conference of Restoration Ecology in 2003 was “understand and restore ecosystem”, which indicated the basic significance of ecosystem restoration. There are many types of ecosystems, including forest, grassland, desert, ocean, lake and river. They are not only different in appearance, but also composed with separately unique biotic components. For different ecosystem types, the theory and methods of recovery and reconstruction are different. In the first three sections of this chapter, we discussed the ecological restoration for degraded forest ecosystem, grassland ecosystem, and wetland ecosystem. The fourth section described protection and restoration of sandland ecosystem. In the restoration research of each ecosystem type, the chapter emphasized the degradation actuality of different ecosystems, its reasons, corresponding restoration ways, and benefits and evaluation. There have been great achievements have been made in the ecosystem restoration research field in China, and some have reached the advanced international level. The authors of all sections are experts, who have spent years researching the ecosystem restoration, thus whether their discourses were based on themselves research, or their articles integrated peer research nationwide, they summarized the front research which reflected the overall level of this field in current in China.