Terrestrial plants on Earth have been drastically affected by climate change and anthropogenic disturbances since the Industrial Revolution. The global patterns of the relationships between various plant functional traits determine the distribution and productivity of plant species worldwide. Although many studies have confirmed the importance of key traits and their relationships in the adaptation and evolution of plant species, comprehensive analyses of trait relationships within and across global biomes and biogeographical realms remain limited. In this study, we investigated the spectrum of plant functional traits and their relationships by combining functional trait data spanning 5633 species and 2342 sites across global biomes and biogeographical realms. We found that plant functional traits varied greatly and were highly specific to biomes and realms. The slopes of the standardized major axis regressions between bivariate traits reflected the resource-use strategies of each biome and realm. Multidimensional traits were highly coordinated with trade-offs but depended particularly on plant functional types. Climatic factors played a critical role in determining the composition of plant species across biomes and realms by modulating a set of essential trait combinations, namely the coordination and trade-offs of plant functional traits, which enhanced the adaptability of plants to their environments. Therefore, we propose that future studies must focus on investigating the relationships between the local habitat specificity of traits, as well as their relationships with environmental changes. Additionally, we suggest improving models that predict changes in vegetation based on continuous variations in plant functioning across global flora.

Plant functional traits and their interrelationships are critical in shaping the evolutionary and adaptive trajectories of plant species, as well as their responses to environmental changes. Grassland ecosystems serve as a natural laboratory for exploring plant trait coordination, given their high biodiversity, environmental heterogeneity and intricate species interactions. However, the patterns of trait covariation across grasslands-the largest terrestrial ecosystems globally-and their environmental dependencies remain poorly understood. In this study, we compiled a newly updated dataset for grassland ecosystems to analyse global patterns of leaf traits across grassland species and to identify their key climatic drivers. A global database comprising 9158 site-level observations was used. We found that leaf traits and their relationships varied significantly across climatic zones and plant functional types. Globally, C4 plants, forbs and annuals exhibited a resource acquisition strategy. Plants in temperate climates tended to adopt a conservative strategy, whereas those in boreal, subtropical, tropical and Mediterranean climates were more likely to employ a resource acquisition strategy. A clear conservative-acquisitive trade-off axis among functional traits was observed across global grasslands. Precipitation primarily drove the first axis of trait variation, which largely reflected a resource-acquisition strategy. In contrast, temperature predominantly influenced the second axis, which was associated with leaf nitrogen status. Synthesis. Our findings underscore the strong global associations among plant functional traits, the pivotal role of plant functional types in mediating trait coordination and trade-offs and their dependencies on climatic zones and environmental factors. These findings provide valuable insights into the coordination and trade-offs of trait relationships at a global scale.

Understanding how plant functional traits respond to nutrient enrichment becomes more crucial for predicting changes in grassland community composition and functions under global changes. However, it remains unclear how nitrogen (N) and phosphorus (P) additions jointly influence a variety of leaf traits and how they coordinate with contrastingly adaptive mechanisms in arid ecosystems. A two-year field experiment with five N levels and two P treatments was conducted to examine the effects of N and P additions on leaf/community functional traits in a desert steppe. We found N addition significantly affected the other six leaf morphological and nutrient traits except leaf thickness (LT); nitrogen addition remarkably increased leaf nitrogen concentration (Nmass) and decreased C/N with or without P; nitrogen addition profoundly elevated stomatal conductance (gs) but did not obviously affect photosynthetic rate (Aarea) except Tribulus terrestris. Compared to grasses, the annual forb T. terrestris exhibited stronger competitiveness (Nmass, Aarea) with increased N application. Nitrogen addition obviously increased community-weighted means (CWMs) of Nmass, specific leaf area (SLA), plant height, gs and Aarea, improving aboveground biomass (AGB), whereas P addition significantly enhanced CWM of SLA but reduced CWMs of transpiration rate and LT. With increasing N addition rates, dominant S-strategy species (higher LT and C/N) in low-nutrient environments were gradually substituted by R-strategy species (higher Nmass and Aarea) in high-nutrient environments. Our results highlight differential responses of plant functional traits to nutrient enrichment and divergent adaptive strategies among species should be considered when assessing the impacts of global environmental changes on community assembly and functioning.

Much attention has been given to the distribution of soil organic carbon and nitrogen in alpine grasslands, but the important role of the deep soil layers has been understudied. In this study, the soil organic carbon and nitrogen contents in the shallow (0–30 cm), middle (30–100 cm) and deep (100–300 cm) layers were examined, and the effects of climatic, soil and vegetation factors were investigated along a climatic gradient on the Tibetan Plateau. We found that although soil organic carbon and nitrogen on the Tibetan Plateau declined logarithmically with depth, the total soil organic carbon and nitrogen in the middle and deep layers accounted for more than two‐thirds of the total carbon and nitrogen in the 3‐m depth soil profile. Carbon to nitrogen ratio increased with soil depth in 1 m soil, but it remained consistent in 1–3 m soil. The surface carbon and nitrogen contents were positively correlated with precipitation. The comprehensive research has revealed that soil carbon and nitrogen contents are mainly influenced by the local humid climate, vegetation productivity, and soil properties, which strongly depend on soil depth. Therefore, more attention should be given to the changes in carbon and nitrogen in deep soils in alpine regions.

Elucidating biomass partitioning between above- and belowground parts in plant communities is vital to better assessing the ecological services of terrestrial ecosystems. However, the knowledge of biomass allocation in grasslands is scant, especially for the divergent mechanisms under both contrasting conditions. On two large geographic transects, Tibetan Plateau and Inner Mongolian Plateau, we analyzed the general and differential mechanisms of biomass allocation (plant biomass ratio of root to shoot, R/S) in temperate vs. alpine grasslands. We found that the R/S exhibited large variations, ranging from 3.89 to 45.10 in temperate grasslands and from 4.74 to 80.72 in alpine grasslands. The R/S decreased with increasing precipitation in both grasslands, whereas it weakly related to temperature. Plant functional group had highest importance on R/S than mean annual precipitation, mean annual temperature, soil nitrogen and phosphorus availabilities, and plant richness and diversity index. Climate factors indirectly but strongly drove R/S by mainly changing plant functional group compositions. Particularly, forbs affected R/S more than other dominant plant functional types. This information can provide a profound insight into the biomass allocation dynamics in grasslands at regional level under climate change scenarios.

A variable future climate would lead to changes in the biomass allocation pattern of plant communities, but its divergent changes under different environments have not been clearly explored, greatly limiting a better understanding of the responsess of grassland ecosystems to environmental changes. Herein, we conducted field samplings at 215 grassland sites in the Qinghai-Tibetan and Inner Mongolian Plateaus to analyze community biomass allocation patterns (specifically, the ratio of root to shoot, R/S) in various grasslands along environmental gradients. We found a gradual increase in R/S from humid to semi-arid and arid environments across both plateaus. In humid environment, soil factor had a significant effect on the R/S of alpine humid grassland, while climate factor had a significant effect on the R/S of humid grassland. In semi-arid environment, both climate and plant factors had significant effects on R/S in semi-arid grassland. In arid environments, climate and plant factors had significant effects on R/S in arid grassland. These findings emphasize the multifaceted role of environmental factors in shaping biomass allocations across diverse ecosystems, enriching our understanding of ecological dynamics. The current results are timely in advancing the fundamental understanding of the mechanisms of biomass allocation in grasslands and are useful for global research on grasslands in different environments.

Nitrogen (N) and phosphorus (P) enrichments are expected to increase above-ground net primary productivity (ANPP), alter plant community composition, and accelerate biodiversity losses. However, how N and P synergistically affect plant communities and the underlying mechanisms remain elusive. Here, a 2-year in situ experiment with five levels of N and two levels of P treatments in an arid ecosystem was conducted to examine the independent and interactive effects of N and P additions on plant community structure and ANPP and their driving factors. The analysis of variance showed that nutrient enrichment significantly increased ANPP by a maximum value of 93% at N (15 g N m - 2 yr - 1 ) treatment and a maximum of 95% at N -P (10 g N m - 2 yr - 1 , 10 g P 2 O 5 m - 2 yr - 1 ) treatments. N addition alone significantly decreased species richness and dominance but increased evenness and diversity. The principal component analysis indicated that dominant species of plant communities gradually shifted from a perennial species Stipa breviflora to an annual species Tribulus terrestris under N and P enrichments. The nonmetric multi-dimensional scaling ordination revealed that N addition significantly promoted the divergence in species composition, whereas P enrichment relieved this change. The structural equation modelling illustrated that N and P additions affected ANPP mainly via modifying plant community composition and structure. This study demonstrates that the potential mechanism of adverse changes in a vulnerable ecosystem is related to the alterations in plant functional groups mainly due to divergent responses of dominant species to nutrient enrichment. This should be considered when assessing and modelling the ecological and evolutionary trajectories of terrestrial ecosystems under the conditions of global environmental changes.

BACKGROUND:Predicting relationships between plant functional traits and environmental effects in their habitats is a central issue in terms of classic ecological theories. Yet, only weak correlation with functional trait composition of local plant communities may occur, implying that some essential information might be ignored. In this study, to address this uncertainty, the objective of the study is to test whether and how the consistency of trait relationships occurs by analyzing broad variation in eight traits related to leaf morphological structure, nutrition status and physiological activity, within a large number of plant species in two distinctive but comparable harsh habitats (high-cold alpine fir forest vs. north-cold boreal coniferous forest).RESULTS:The contrasting and/or consistent relationships between leaf functional traits in the two distinctive climate regions were observed. Higher specific leaf area, photosynthetic rate, and photosynthetic nitrogen use efficiency (PNUE) with lower N concentration occurred in north-cold boreal forest rather than in high-cold alpine forest, indicating the acquisitive vs. conservative resource utilizing strategies in both habitats. The principal component analysis illuminated the divergent distributions of herb and xylophyta groups at both sites. Herbs tend to have a resource acquisition strategy, particularly in boreal forest. The structural equation modeling revealed that leaf density had an indirect effect on PNUE, primarily mediated by leaf structure and photosynthesis. Most of the traits were strongly correlated with each other, highlighting the coordination and/or trade-offs.CONCLUSIONS:We can conclude that the variations in leaf functional traits in north-cold boreal forest were largely distributed in the resource-acquisitive strategy spectrum, a quick investment-return behavior; while those in the high-cold alpine forest tended to be mainly placed at the resource-conservative strategy end. The habitat specificity for the relationships between key functional traits could be a critical determinant of local plant communities. Therefore, elucidating plant economic spectrum derived from variation in major functional traits can provide a fundamental insight into how plants cope with ecological adaptation and evolutionary strategies under environmental changes, particularly in these specific habitats.

Comparisons of vegetation production between temperate and alpine grasslands are not well studied, and the understanding of the underlying mechanisms is still incomplete. To address this issue, we selected the Inner Mongolia and Tibet regions to conduct large-transect surveys for temperate grassland (TG) and alpine grassland (AG), respectively, in China, to reveal the universal and differential mechanisms of above-and belowground biomass production (GB, AGB and BGB) and precipitation use efficiencies (PUE) in the two grasslands. The relative importance of climatic factors on biomass and PUE is greater than that of soil and biological factors. Elevated mean annual precipitation (MAP) consistently increased GB in both TG and AG. Increased mean annual temperature (MAT) reduced GB by weakening the soil nutrient status in TG, whereas it increased GB by improving the soil nutrient status in AG. MAP promoted more AGB than BGB in TG, whereas MAT affected BGB more than AGB in AG. When the multicomponent heterogeneity of other factors in grasslands was eliminated, the effect of MAP on GB remained significant for both TG and AG. After removing the effect of multifactorial het-erogeneity, however, the significant effect of MAP on PUE of the two grasslands was largely enhanced. From these results, we can conclude that climatic factors do not always exert identical effects on different grasslands. In particular, highlighting the divergent mechanisms of biomass production and precipitation use efficiency between temperate and alpine grasslands can improve the understanding of the carbon sink and hydraulic sensitivity of various grasslands.

以山东省寿光市清水泊农场农田及7个不同复垦年限废弃盐田土壤为研究对象,采用空间代替时间序列方法对不同土层(0～20、20～40、40～60、60～80、80～100cm)土壤理化性状与微生物特性进行了研究.结果表明:(1)复垦后土壤含盐量降低,土壤有机质、全氮、速效磷及速效钾含量增加,各养分含量在复垦8a时达到最大值,基本达到农田水平;(2)土壤中细菌、放线菌数量随着复垦年限的增加呈先增加后下降的趋势,而真菌数量则持续上升;(3)复垦有利于土壤脲酶、碱性磷酸酶、蔗糖酶和过氧化氢酶的提高,复垦年限越长,酶活性提高越显著;(4)通过构建复垦质量变化预测定量模型,预测复垦土壤有机质、全氮、速效磷及速效钾含量达到对照农田水平分别需8.75、8.45、8.24、8.41a;(5)经主成分分析得出,影响复垦土壤质量演变的主要因子为蔗糖酶、过氧化氢酶、有机质和细菌.本文分析了废弃盐田复垦土壤各理化和微生物指标的变异特征及时空分布规律,可为科学指导黄河三角洲废弃盐田复垦区土壤综合治理和农业可持续发展提供理论依据.

[目的]研究农田排水沟渠的水盐和养分的分布特征,探究生态修复立地条件.[方法]本研究通过对黄河三角洲两种典型农田排水沟(农沟、斗沟)不同坡面(东、西、南、北)、坡位(上、中、下)的植被进行调查,并对按照不同土层深度(0～10cm、10～20cm、20～40cm)测定坡位的土壤水分、盐分、养分含量.并对数据进行PCA分析.[结果]结果表明:(1)土壤水分盐分共同构成农田排水沟表层土壤的重要影响因素.土壤水分在农沟中坡位最高,在斗沟表现为下坡位最高,在北坡和西坡的下坡位占据主要因素.农田排水沟土壤全盐含量在农田排水沟中坡位集中,构成该坡位的主要影响因素.(2)在中坡位形成显著的有机质富集区,土壤全氮受植被根系影响显著,养分一般在根区形成显著影响.土壤养分分布与物种丰富度相关,在斗沟同时受到植被生物量的影响.农田排水沟在中坡位体现出盐分、养分的综合影响,北坡和西坡下坡位同时受到水分和养分的制约,南坡和东坡则受到养分和植被的综合影响.(3)农田排水沟的中坡位亟待降低盐胁迫、建植耐盐品种,上坡位、下坡位保持土壤水分和养分、降低盐分析出尤为重要.阳坡半阳坡合理水分补充有利于群落稳定,阴坡、半阴坡可以通过增加耐盐植物种类提高物种丰富度以增强微生态抗逆性.[结论]农田排水沟生态受表层土壤水盐、深层养分与地被植被影响较大,不同坡向坡位的主要影响因子不同,应采取适宜的生态修复方式.

Field experiments were conducted to evaluate the effects of wheat straw return methods, which included the use of surface straw mulch and a buried straw layer, on soil water content, electrical conductivity (EC), and sodium adsorption ratio (SAR) of saline sodic soils in an effort to identify useful ways for reducing soil salt accumulation and enhancing soil water content. The results showed that the straw return treatments were effective for inhibiting salt accumulation and soil water loss, resulting in a reduction of EC and SAR but an enhancement of soil water content. After a year-long experiment, compared with the treatment with no straw return, the straw burial and straw mulching treatments decreased the EC by 10.5% and 3.5%, reduced the SAR by 7.4% and 21.5%, and increased the soil water by 0.9% and 4.4%, respectively. Furthermore, the combined application of straw layer burial and surface straw return had a more significant effect than the individual treatments; the positive effect of straw return occurred mainly focused in the topsoil (0–40 cm) and decreased with increasing soil depth. Our results allowed us to conclude that burial of the straw layer was necessary to enhance the effects of surface mulch, and the combination of surface mulch (3.0 t ha −1 of wheat straw) and straw layer burial (6.0 t ha −1 of wheat straw) proved to be a better straw return method than the others.

通过室内土柱模拟试验,研究不同灌水量对盐渍土的改良效果.试验共设计3个不同灌水量,分别为S1(200 mm)、S2(300 mm)、S3(400 mm).结果表明:(1)灌溉淋洗对0—40 cm土壤盐分淋失影响较大,其中0—20 cm脱盐率最高,表现为S3>S2>S1,不同处理在剖面上均出现积盐,S1、S2在40—60 cm出现积盐,说明低灌水量对土壤表层盐分具有淋洗作用,但会造成底层土壤盐分累积;(2)K+、Na+、Ca2+、Mg2+、Cl-、SO 42-、HCO 3-含量在灌水后有较大幅度的下降,且整体溶脱率随灌溉水量的增加而增加.各离子在0—20 cm随灌水量增加表现为不同的变化规律,Ca2+先溶脱后积累,HCO 3-变化规律与Ca2+相反,表现为先积累后溶脱,其他离子均随灌水量的增加而减少;(3)灌水后,S1、S2的pH在剖面上的分布与灌水前相似,0—40 cm土壤总碱度随灌水量增加呈先增后减的趋势,表现为先碱化再脱碱,与土壤pH变化一致.研究成果可为盐碱地改良和节水灌溉提供参考.

We measured soil water and salt distribution characteristics at 0-40 cm soil depth in a silvopastoral system of Fraxinus chinensis and Robinia pseudoacacia mixed forest × Medicago sativa, which is located in Land Use Scientific Observation Field Base of Ministry of Land and Resource in Wudi, Shandong Province, China. The moving split-window technique was used to analyze the internal-system edge effect. The results showed that both soil water and salt contents in this system heterogeneously distributed in the horizontal direction. The variation of soil water was greater and that of soil salt contents was the smaller when closer to the soil surface. With the mixed forest tree row as the boundary line, the contents of soil water and salt on both sides showed similar change trend. With the decreases of distance to the tree row, soil water content reduced first and then increased but the salt contents had a stable fluctuation at 0-10 cm soil layer. Soil water content showed a trend of decrease-flat-decrease but the salt contents first enhanced and then reduced at 10-20 cm soil layer, respectively. At the deeper soil layer (20-40 cm), the water content fluctuated stably but the salt content continued increasing. Both the contents of soil water and salt in the vertical direction increased significantly with soil depth. Except HCO3- and K+, there was a similar change trend between ions and total salt content in the soil of silvopastoral system, and the correlation between these ions and total salt content was Na+>Cl->SO42->Mg2+>Ca2+. Based on the technique of moving split-window, the edge effect zone of soil water in the silvopastoral system was 2.5 m from the east side of the tree row to 2 m from the west side. Soil salinity in the silvopastoral system was mainly affected by the tree row within the range of 1.0 m, and by both of the tree row and M. sativa within the range of 1.0-3.0 m.