Pan evaporation (E_pan) is a critical measure of the atmospheric evaporation demand. Analyzing meteorological data from the Tropical Rainforest Comprehensive Meteorological Observation Field in the Xishuangbanna Tropical Botanical Garden (XTBG Meteorological Observing Station) based on physical models is helpful to improve our understanding of the state of the hydrological cycle in the Xishuangbanna tropical rainforest region. In this study, we investigated the long-term trend in E_pan using the observation data from 1959 to 2021. Moreover, correlation analyses of E_pan were performed, such as trend test, assessment of periodic properties and abrupt change analysis. Then, D20 E_pan data and related meteorological data from 1979 to 2008 were used to drive Penman‒Monteith and PenPan models for simulating E_pan. The partial derivative attribution method was used to analyze the dominant factors affecting E_pan. The results showed that E_pan exhibits obvious periodic changes, the 19a is the first primary period. In addition, there was a clear ‘evaporation paradox’ phenomenon in Xishuangbanna. E_pan showed a decreasing trend during both 1959-2008 and 2009-2018, and the decreasing trend reached a significant level with a rate of -3.404 mm·a^-2 during 1959-2008. Through comparative analysis, the PenPan model was considered more suitable for simulating E_pan in Xishuangbanna. In order to identify the main meteorological factors influencing E_pan, complete data from the D20 pan monitoring period, namely, 1979-2008, were selected for attribution calculations. The variations in the net radiation and saturated vapor pressure deficit are the main triggers that explain the ‘evaporation paradox’ phenomenon in Xishuangbanna.

Patterns in functional trait variation associated with the ecological strategies of lianas and trees in subtropical montane forests remain poorly understood due to lack of trait comparisons. Here, we filled this gap by investigating trait divergence between lianas and trees with different leaf habits for 13 traits of 33 species (7 deciduous and 4 evergreen liana species, and 10 deciduous and 12 evergreen tree species) in a subtropical montane forest in southwestern China. We found that lianas had significantly larger stem xylem vessel diameter, higher theoretical hydraulic conductivity, specific leaf area, leaf nitrogen, and phosphorus concentrations, but lower leaf dry-matter content and N/P ratio than sympatric trees, indicating that lianas employ an acquisitive ecological strategy, with a more efficient stem hydraulic system and more productive leaves. In contrast to trees, lianas exhibited a larger variation in vessel diameter, with a few wide and many narrow vessels in the xylem, indicating a greater vessel dimorphism. Growth form explained 48.7% of the total trait variation, while leaf habit only explained 3.8% of trait variation, without significant interaction between growth form and leaf habit. In addition, significant stem-leaf trait relationships were only found in trees, but not in lianas, indicating decoupling of stem hydraulic function and leaf traits in subtropical lianas. These results suggest that subtropical montane lianas and trees differ strikingly in stem and leaf functional traits. Further studies are warranted to strengthen our understanding of the mechanisms underlying the strong divergence in ecological strategies between lianas and trees in subtropical forest ecosystems.

Studies of selected habitat conditions, as well as spatiotemporal variability of the number and selected traits of individuals of the species Arum alpinum were carried out in 2020-2021 in the foothills of the Western Carpathians. The investigations were conducted in permanent patches located in the Golesz nature reserve (Patch I), near the village of Markowce (Patch II), in the Kozigarb nature reserve (Patch III), and near the village of Żółków (Patch IV). Patches I and III were established in a Tilio cordatae-Carpinetum betuli oak-hornbeam forest with undergrowth dominated by low-growth vegetation with narrow leaves, whereas Patches II and IV were established in a Populetum albae riparian forest with undergrowth dominated by broad-leaved species. The most abundant population of A. alpinum was noted in Patch I, but substantial numbers of both vegetative and reproductive individuals were also present in Patches II and IV. The occurrence of temporal variability of individual traits increased from its lowest level in Patch IV, through Patches I and II, to its highest level in Patch III. The significant positive correlation in all populations between length of petioles and blade dimensions, as well as between length of generative stems and infructescence traits confirmed previous findings. Moreover, we showed that A. alpinum was not closely affiliated with a specific forest community. Significant shading and moist nutrient-rich soils are suitable for this species, while dry soils and excessive insolation may limit the flowering and fruiting of individuals.

In angiosperms, diverse floral traits are adaptations to various selective pressures and ecological functions. So far, studies on floral traits in orchids have focused primarily on the labellum but never on bracts. A bumblebee-pollinated and rewarding terrestrial or epiphytic herb, Thunia alba (Lindley) H. G. Reichenbach (Orchidaceae), has conspicuously large and curly bracts that enclose the spur and pedicel of flowers. We hypothesized that these large bracts could protect spurs against nectar robbers. To confirm this hypothesis, we experimentally removed the bracts to record the changes in visiting behavior of mutualistic pollinators and antagonistic nectar robbers and evaluated their effects on reproduction success. Our result revealed that Bombus breviceps, the only pollinator of T. alba, shifted to nectar robbery when the bracts were removed, and the proportion of robbed flowers also significantly increased. Thunia alba was found to be pollinator limited regardless of whether in intact treatment or removed bract treatment. Removal of bracts had no effect on the visiting frequency of B. breviceps, but it reduced male and female reproductive success. These findings indicate that, under complex environmental pressures with limited pollination, large bracts can protect against nectar robbers and enhance the fitness of T. alba.

Nitrogen (N) deposition exhibits significant impacts on ecosystem functions and processes. Previous studies have indicated that N addition has an impact on the stoichiometry of plant leaf C:N:P ratios. However, few studies have focused on effects of N addition on belowground systems. This study aims to examine the impact of 7 years of N addition on above- and belowground C:N:P stoichiometry at plant community level in a temperate grassland located in Inner Mongolia. A 7-year field N addition experiment was conducted, which included six treatments: Cont: control; N1: 0.4 mol·m^-2 N; N2: 0.8 mol·m^-2 N; N3: 1.6 mol·m^-2 N; N4: 2.8 mol·m^-2 N; N5: 4 mol·m^-2 N with six replicates. Above- and belowground plant biomass and C:N:P stoichiometry were measured and analyzed. Our results showed that N addition resulted in a reduction of aboveground C concentration, but an increase in aboveground N and P concentrations, with a decrease in C:N and C:P ratios and an increase in N:P ratio. Furthermore, the aboveground C, N, and P pools all exhibited an increase as a result of N addition. However, N addition did not have any significant effect on belowground C, N, P concentrations, ratios, pools, or stoichiometric characteristics in the soil layers of 0-10, 10-30, 30-50, and 50-100 cm. These results suggest that increasing levels of N deposition significantly alter the aboveground C:N:P stoichiometry at the plant community level, which may affect functions and processes in the grassland ecosystem, but have little effect on belowground C:N:P stoichiometry.

Trade-offs in growth and reproduction are essential parts of the adaptive strategies of clonal plants. How rhizomatous psammophytes respond to aeolian processes (sand burial and wind erosion) by means of trade-offs is supposed to be especially important for their colonization on the active sand dune. Despite partial documentation of the responses of rhizomatous species to aeolian processes, how these clonal species respond to aeolian processes by means of potential trade-offs in growth and reproduction still remains unclear. In this study, we employed field investigation and biomass modeling to evaluate the trade-offs between vegetative and reproductive growth as well as between the number and size of ramets of Phragmites communis in response to sand burial and wind erosion. Sand burial enhanced the accumulation of seed biomass and reproductive effort. Wind erosion reduced reproductive effort but had no significant influence on seed biomass. Sand burial increased the biomass of ramets, while wind erosion increased ramet population density and accelerated ramet maturation. Our results demonstrate that rhizomatous psammophytes adjust their growth strategies in response to aeolian processes, i.e. reproductive growth and ramet size increase in response to sand burial, while vegetative growth and ramet numbers increase in response to wind erosion.

Investigating the variations in leaf stoichiometry among plant common species at different altitudes, along with the factors that influence these variations and the adaptative strategies employed, is of significant importance for understanding biogeochemical cycles amidst global environmental changes. In this research, we measured soil organic carbon and nutrient concentrations, as well as leaf stoichiometry for plant common species at five altitudes (2400-3200 m with an interval of 200 m) within the Qilian Mountains of Northwest China. This study aims to enhance our understanding of how plant common species in mountainous regions exhibit adaptable responses to altitude variations and how potential environmental changes in the future may influence their leaf functions. Results showed that the leaf C:N:P stoichiometry of plant common species varied with increasing altitude. Across altitudes, mean annual temperature (MAT), soil total phosphorus, mean annual precipitation (MAP), soil water content, and soil nitrate nitrogen were the main factors influencing leaf element concentrations of plant common species. However, leaf stoichiometric ratios were mainly determined by MAT, MAP, and soil total nitrogen. The effects of MAT and MAP on both leaf element concentrations and leaf stoichiometric ratios of plant common species were found to be significant. Plant growth in the study area was mainly limited by P. The results not only highlight the adaptive strategies employed by plants, but also contribute to understanding of leaf stoichiometry, and establishing connections between individual plant species and broader plant community composed of these common species.

The ecology of plant species relies on the synchronous functioning of leaves and roots, but few studies have simultaneously examined the community trait dispersion (CTD) patterns of both organs. We measured 16 analogous leaf and root traits on 44 co-occurring woody species in a subtropical forest in southern China, aiming to examine whether leaf and root traits were coordinated, organized into parallel trait axes, exhibited similar CTD, and displayed consistent responses in CTD and community-weighted means of (CWM) traits over environmental gradients. While the first axes of leaf and root trait variation similarly exhibited a fast-slow continuum, leaf traits covered a secondary “carbon economics” axis, contrasting to root traits depicting a collaboration axis reflecting species’ mycorrhizal dependency. Analogous leaf and root chemical traits were generally coordinated but less so for morphological traits. At the community level, changes in the CWM of the first axes were generally consistent among organs with more conservative traits found as increasing elevation but not for the second axis. While root traits became thinner and more conservative as soil phosphorus concentration decreased, leaf traits rarely varied. When different trait axes were combined, leaf traits were overdispersed but tended to converge with increased elevation and soil potassium and phosphorus levels, whereas root traits were clustered but tended to diverge along the same gradients. Our study highlights fine filtering of different suites of traits above- and belowground, which in turn might reduce overall niche overlap among species and promote coexistence with diverse functional designs.

Reabsorbing nutrients from senescent tissues before leaf falling has been recognized as a strategy to adapt to nutrient deficiency. However, how nutrient resorption modulates the nitrogen (N)-phosphorus (P) balance inside plants remains unclear, especially under increased soil N availability. We examined the impacts of N addition at varying rates (0-32 g N m^-2 yr^-1) on nutrient resorption and the performance of nutrient resorption on controlling the internal N-P balance in the leaf and stem of a dominant grass species, Leymus secalinus, in a saline-alkaline grassland in northern China. After 6 years of N addition, N concentration and N:P ratio in green and senesced tissues (leaf and stem) rose with increasing N addition. The P concentration in green tissues decreased, but did not significantly change in senesced tissues with increasing N addition. The N resorption efficiency (NRE), P resorption efficiency (PRE), and NRE:PRE ratio significantly decreased along the N addition gradient. Moreover, we found more sensitive responses of N:P ratio in senesced tissues than in green tissues; such exacerbation of plant internal N-P imbalances mainly resulted from a disproportionate reduction in nutrient resorption, especially NRE. Overall, our study suggested that differences in NRE and PRE further exacerbated the internal N-P imbalances in plant litters.

Energy partitioning and evapotranspiration (ET) of alpine meadows in permafrost areas are crucial for water cycle on the Qinghai-Tibet Plateau. However, seasonal (freeze-thaw cycle) variations in energy partitioning and ET and their driving factors must be clarified. Therefore, 4-year energy fluxes [i.e. latent heat (LE) and sensible heat (H)] were observed, and bulk parameters [i.e. surface conductance, decoupling coefficient (Ω), and Priestley-Taylor coefficient (α)] were estimated in an alpine meadow in the Qinghai-Tibet Plateau. Mean daily LE (27.45 ± 23.89 W/m²) and H (32.51 ± 16.72 W/m²) accounted for 31.71% and 50.14% of available energy, respectively. More available energy was allocated to LE during the rainfall period, while 67.54 ± 28.44% was allocated to H during the frozen period. H was half the LE during rainfall period and seven times the LE during frozen period due to low soil water content and vegetation coverage during the frozen season. Mean annual ET was 347.34 ± 8.39 mm/year, close to mean annual precipitation. Low mean daily Ω (0.45 ± 0.23) and α (0.60 ± 0.29) throughout the year suggested that ET in the alpine meadow was limited by water availability. However, ET was constrained by available energy because of sufficient water supply from precipitation during rainfall season. In contrast, large differences between ET and precipitation indicated that soil water was supplied via lateral flow from melting upstream glaciers and snow during the transition season. The results suggest that seasonal variations in bulk parameters should be considered when simulating water and energy fluxes in permafrost regions.

Successful introgression of a transgene from a transgenic crop into a wild or weedy relative is determined by the fitness of backcross generations carrying the transgene. To provide insight for ecological risk assessment of gene flow between transgenic Brassica napus and wild Brassica juncea, this study investigated the fitness of the first backcross generations from the second to the sixth progenies (BC₁F₂R-BC₁F₆R) between glyphosate-resistant transgenic B. napus and wild B. juncea at low density (5 plants/m²) and high density (10 plants/m²), and monoculture and mixed planting (wild B. juncea: BC₁F₂R-BC₁F₆R = 1:1). Correlations between the fitness components of backcross progeny, planting density and planting patterns were analyzed. In the monoculture at low density, compared with B. juncea, earlier generations BC₁F₂R and BC₁F₃R had low composite fitness, while later generations from BC₁F₄R to BC₁F₆R were more fit. At high density, whatever monoculture or mixed planting, all backcrossed generations had lower composite fitness than B. juncea. Correlation analysis indicated that both planting density and pattern significantly affected the fitness components of the first backcross generations from the second to the sixth progenies (BC₁F₂R-BC₁F₆R). These results indicate that the probability of transgene introgression from cultivated B. napus to weedy B. juncea is likely to be highly contingent on the specific growing conditions of their backcross descendants.

Climate warming, rising atmospheric CO₂ concentration (C_a), and nitrogen (N) availability are exerting profound impacts on global forest ecosystems, particularly in high-altitude mountains. This study investigated the tree-growth dynamics of timberline Larix chinensis in the Taibai Mountain, central China, and explored its ecophysiological responses to environmental stresses by combining tree growth and stable isotopes. The results showed that the growth rate of L. chinensis has significantly increased since the 1960s, and that tree growth in this timberline was particularly sensitive to temperature in spring. Moreover, the continuously rising intrinsic water-use efficiency (iWUE), linked to higher C_a and warmer environment, promoted the growth of L. chinensis. Before the 1960s, tree-ring δ¹⁵N gradually increased, then shifted to an insignificant decline with the acceleration of tree growth, and broke the preexisting carbon-nitrogen balance. Meanwhile, climate warming and increased iWUE have replaced N as the principal drivers of tree growth since the 1960s. It is believed that L. chinensis may gradually suffer a decline in N availability as it continues to grow rapidly. The insightful understanding of the biochemical mechanisms of plant responses to growth-related environmental conditions will improve our ability to predict the evolution of high-elevation mountain ecosystems in the future.

Allocating resources for reproduction involves ecological and evolutionary factors and can reduce vegetative growth in plants. This interrelationship is not easily observed in nature, as there are many parameters that can limit the production of reproductive structures or the addition of biomass. We related tree-ring width to supra-annual reproductive behaviour of Cedrela odorata L. (Meliaceae) in the Atlantic Forest of Rio de Janeiro State. In general, the development of reproductive structures occurred in wet years, without water deficit at the beginning of the growth season. However, in these years, tree-ring width was smaller. These results may be associated with the lack of correlation between tree-ring width and local climate. In this way, we highlight the importance of incorporating reproductive data in radial growth studies to expand the understanding of growth variability in tropical forests.

Although understanding mutualism stability has advanced over the last few decades, two fundamental problems still remain in explaining how mutualisms maintain stable. (i) How does resolve conflict between mutualists over resources? (ii) In the presence of less cooperative and/or uncooperative symbionts, how does prevent symbiont populations from becoming dominated by uncooperative individuals? Many past explanations of mutualism stability have assumed that interactions between mutualists are symmetrical. However, in most mutualisms, interactions between hosts and symbionts show varying degrees of asymmetry at different levels. Here, we review three major types of asymmetric interactions within obligate mutualisms: (i) asymmetric payoffs, which is also defined as individual power differences, (ii) asymmetric potential rates of evolutionary change, and (iii) asymmetric information states between hosts and symbionts. We suggest that these asymmetries between mutualists help explain why cooperation and conflict are inherent in the evolution of mutualisms, and why both hosts and symbionts present diversified phenotypes while cooperation predominates.