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Leaf-stem allometry is an important spectrum that linked to biomass allocation and life history strategy in plants, although the determinants and evolutionary significance of leaf-stem allometry remain poorly understood. Leaf and stem architectures - including stem area/mass, petiole area/mass, lamina area/mass, leaf number, specific leaf area (LA), and mass-based leafing intensity (LI) - were measured on the current-year branches for 28 species growing in a common garden in SW China. The leaf anatomical traits, stem wood density (WD), and stem anatomical and mechanical properties of these species were also measured. We analyzed leaf-stem allometric relationships and their associations with stem hydraulic ad mechanical properties using species-level data and phylogenetically independent contrasts. We found isometric relationship between leaf lamina area/mass and stem area/mass, suggesting that the biomass allocation to leaf was independent to stem size. However, allometric relationship between LA/mass and petiole mass was found, indicating large leaves invest a higher fractional of biomass in petiole than small ones. LI, i.e., leaf numbers per unit of stem mass, was negatively related with leaf and stem size. Species with larger terminal branches tend to have larger vessels and theoretical hydraulic conductivity, but lower WD and mechanical strength. The size of leaf lamina, petiole, and stem was correlated positively with stem theoretical hydraulic conductivity, but negatively with stem WD and mechanical strength. Our results suggest that leaf-stem allometry in species was shaped by the trade-off between stem hydraulic efficiency and mechanical stability, supporting a functional interpretation of the relationship between leaf and stem dimensions.

Stable isotopes in wood cellulose of tree rings provide a high-resolution record of environmental conditions, yet intra-annual analysis of carbon and oxygen isotopes and their associations with physiological responses to seasonal environmental changes are still lacking. We analyzed tree-ring stable carbon (δ C) and oxygen (δ O) isotope variations in the earlywood (EW) and latewood (LW) of pines from a secondary forest ( ) and from a natural forest ( ) in southwestern China. There was no significant difference between δ C and δ C in , while δ C was significantly higher than δ C in . For both and , δ C was highly correlated with previous year's δ C , indicating a strong carbon carry-over effect for both pines. The intrinsic water use efficiency (iWUE) in the earlywood of was slightly higher than that of , and iWUE of both pine species showed an increasing trend, but at a considerably higher rate in . Respective δ C and δ C series were not correlated between the two pine species and could be influenced by local environmental factors. δ C of was positively correlated with July to September monthly mean temperature (MMT), whereas δ C of was positively correlated with February to May MMT. Respective δ O and δ O in were positively correlated with those in , indicating a strong common climatic forcing in δ O for both pine species. δ O of both pine species was negatively correlated with May relative humidity and δ O in was negatively correlated with May precipitation, whereas δ O in both pine species was negatively correlated with precipitation during autumn months, showing a high potential for climate reconstruction. Our results reveal slightly higher iWUE in natural forest pine species than in secondary forest pine species, and separating earlywood and latewood of for δ O analyses could provide seasonally distinct climate signals in southwestern China.

The coordination between minor vein density (MVD) and stomatal density (SD) has been found in many plants. However, we still know little about the influence of leaf node on this correlation relationship. Here, we devised the new functional trait ‘stomatal number per minor vein length’ (SV). By measuring leaflet area (LA), MVD, SD, and SV, we demonstrated the significance of this functional trait in Arachis hypogaea (peanut) grown under different light regimes and in sun leaves of Dalbergia odorifera and Desmodium renifolium . We found that SV did not change significantly with leaflet node or with LA within each light treatment, while shading caused a significant decrease in SV. The positive correlation between SD and MVD was found in peanut under each light regime. Sun leaves of D. odorifera and D. renifolium also had stable SV along the leaflet node, with a positive correlation between MVD and SD. We conclude that under a certain light regime, a stable SV similar to the positive correlation between MVD and SD can also indicate the coordination between leaf water supply and demand. Our findings highlight the significance of SV and provide new insight into the coordination between stomatal number and minor vein length.

Climate change will impact all plant physiological processes including water transport, photosynthesis, and nutrient assimilation. How these processes are coordinated in response to climate change is not fully understood. Here we tested how these processes will respond to elevated CO2 concentration ([CO2]) and temperatures for two herbaceous species (an invasive and a native Eupatorium species in East Asia; family Asteraceae) and whether these processes are coordinated using a controlled experiment. We also investigated the differences between these two species, and the structural basis for changes in physiology. Leaf photosynthetic capacity (Amax, measured under ambient conditions) increased significantly in the native species, while that of the invasive species did not change under elevated [CO2] and temperatures. The leaf hydraulic conductance (Kleaf) of both species tended to increase under elevated temperatures and [CO2], with that of the native species increasing to a greater extent. Changes in Kleaf and Amax were coordinated, and Kleaf was closely associated with leaf minor vein density across treatments. The increased photosynthetic capacity of the native species was probably related to an increased N investment in photosynthesis; its leaf N decreased but chlorophyll concentration increased inviting detailed studies in N partitioning. No coordination between water use (water transport, stomatal conductance, and water use efficiency) and leaf tissue nutrient (N, P) concentrations was found, probably owing to the active control in nutrient uptake. Thus, photosynthesis is coordinated with water transport in response to climate change, while the coordination between water use and nutrient accumulation can be absent due to active control. Our results also suggest that global climate change will not necessarily fuel more positive responses in invasive plants than native plants.

Climate change may lead to alterations in tree growth and carbon cycling. Interpreting the response of forest growth to climate change requires an understanding of the temporal and spatial patterns of seasonal climatic influences on the growth of tree species. However, the effects of climate change on pine forest dynamics in tropical region of Thailand remain poorly understood. This study develops three new tree ring-width chronologies of Pinus latteri (Tenasserim pine) in northern and northeastern Thailand and analyzes their climate-growth relationships and temporal stability. Ring-width chronologies of P. latteri at three sites showed significantly positive correlations with precipitation, relative humidity and self-calibrated Palmer Drought Severity Index (scPDSI) during the dry season (previous November to current April) and early rainy season (May–June). Conversely, significantly negative correlations were found between ring-width site chronologies and air temperatures (mean, maximum and minimum) from April to August. Therefore, our results revealed that radial growth of Tenasserim pines from northern and northeastern Thailand was mainly limited by moisture availability during the dry-to-wet transition season from April to June. Moving correlations revealed that Tenasserim pines in the lowland area of northeastern Thailand became more sensitive to moisture availability in recent 30 years (1985–2017) as compared with early period (1951–1984). Accompanying the shifted growth sensitivity to climate change, growth synchrony among trees was increasing and tree growth rates of Tenasserim pines have been declining during recent decades at two more moisture-limited sites in northeastern Thailand. Recent rapid warming and increasing drought during the transition season (April–June) together intensify climatic constrains on tree growth of Tenasserim pines in the lowland area of northeastern Thailand. Considering continued regional climate change, pine forests in tropical lowland areas may encounter intensified drought stresses, and thus, become more vulnerable to future climate change. Our results serve as an early indicator of potential effects of climate change on tropical pine species and raise concerns about sustainable managements of pine forests under a changing climate.

Intra-annual monitoring of tree growth dynamics is increasingly applied to disentangle growth-change relationships with local climate conditions. However, such studies are still very limited in subtropical regions which show a wide variety of climate regimes. We monitored stem radius variations (SRV) of Pinus kesiya var. langbianensis (Szemao pine) over five years (2012–2015 and 2017) in the subtropical monsoon mountain climate of the Ailao Mountains, Yunnan Province, southwest China. On average, the stem radial growth of Szemao pine started in early March and ended in early October, and the highest growth rates occurred during May to June. Stem radius increments were synchronous with precipitation events, while tree water deficit corresponded to the drought periods. Correlation analysis and linear mixed-effects models revealed that precipitation and relative humidity are the most important limiting factors of stem radial increments, whereas air temperature and vapor pressure deficit significantly affected tree water balance and may play an important role in determining the growing season length and seasonality (i.e., duration, start, and cessation). This study reveals that moisture availability plays a major role for tree growth of P. kesiya var langbianensis in the Ailao Mountains, southwest China.

Abstract Desiccation-tolerant (DT) plants can withstand dehydration to less than 0.1 g H2O g−1 dry weight. The mechanism for whole-plant recovery from severe dehydration is still not clear, especially for woody DT plants. In the present study, we evaluated the desiccation tolerance and mechanism of recovery for a potentially new woody resurrection plant Paraboea rufescens (Gesneriaceae). We monitored the leaf water status, leaf gas exchange, chlorophyll fluorescence and root pressure of potted P. rufescens during dehydration and rehydration, and we investigated the water content and chlorophyll fluorescence of P. rufescens leaves in the field during the dry season. After re-watering from a severely dehydrated state, leaf maximum quantum yield of photosystem II of P. rufescens quickly recovered to well-watered levels. Leaf water status and leaf hydraulic conductance quickly recovered to well-watered levels after re-watering, while leaf gas exchange traits also trended to recovery, but at a slower rate. The maximum root pressure in rehydrated P. rufescens was more than twice in well-watered plants. Our study identified P. rufescens as a new DT woody plant. The whole-plant recovery of P. rufescens from extreme dehydration is potentially associated with an increase of root pressure after rehydration. These findings provide insights into the mechanisms of recovery of DT plants from dehydration. Desiccation-tolerant (DT) plants can survive in extremely dry environments and withstand dehydration to less than 0.1 g H2O g−1dry mass, and after rehydration the DT plants will regain normal function. This study provides the first evidence that Paraboea rufescens, a small shrub from Gesneriaceae, is a DT plant. After re-watering from a severely dehydrated state, leaf water status and leaf physiological function of P. rufescenscan quickly recover to the well-watered levels. This study also shows that root pressure is an important driving force for whole-plant recovery in P. rufescensfrom severe desiccation.

Tropical forests are major carbon sinks on the Earth's land surface. However, our understanding of how the demographic rate and carbon sink capacities of tropical forests respond to climate change remains limited. In this study, we investigated the impacts of environmental drivers on forest growth, mortality, recruitment, and stem net primary productivity (NPP stem ) over 16 years at five tropical forest plots in Xishuangbanna, Southwest China. These plots are along a successional gradient spanning three tropical secondary forests (tropical secondary forest‐1 [TSF‐1], tropical secondary forest‐2 [TSF‐2], and tropical secondary forest‐3 [TSF‐3]) and two primary forests (tropical rainforest [TRF] and tropical karst forest [TKF]). Our results showed that early successional secondary forests (TSF‐2 and TSF‐3) had higher diameter growth rates and relative mortality rates. An extreme drought event during 2009–2010 reduced the growth rate, relative recruitment rate, and NPP stem for most plots while increasing mortality in early successional forest plots. We observed significant negative effects of maximum temperature (T max ) on NPP stem and diameter growth rate across all plots. Additionally, we found that precipitation had significant positive effects on diameter growth rate across all plots. Furthermore, tree mortality increased with rising T max , whereas precipitation significantly enhanced tree recruitment. Our findings highlight the vulnerability of tree growth, mortality, recruitment, and productivity in tropical forests to extreme drought events in Southwest China. Continued climate warming and more frequent droughts will induce higher mortality rates and impede growth, thus reducing the carbon sink capacity of tropical forests, especially in early successional stage tropical secondary forests. 热带森林是地球上陆地生态系统重要的碳汇。然而目前对于热带森林的群落动态和碳汇能力如何响应气候变化方面的研究较少。在本研究中，我们分析了环境因子对过去16年来西双版纳地区五个热带森林样地直径生长率、死亡率、更新以及树干净初级生产力的影响。这五个森林样地包括三个热带次生林（TSF‐1, TSF‐2和 TSF‐3）以及两个热带原始林（热带季节雨林TRF、热带喀斯特森林TKF）。结果显示演替早期的次生林（TSF‐2, TSF‐3）表现出更高的直径生长率和相对死亡率。2009‐2010年的极端干旱事件使得大部分样地的直径生长率、相对更新率和NPPstem下降，而处于演替早期的次生林样地的死亡率显著增加。发现最高气温（Tmax）与NPPstem和直径生长率呈显著的负相关关系，而降水与五个样地的直径生长率呈显著的正相关关系。树木的死亡率与Tmax呈显著的正相关关系，而更新率与降水呈显著的正相关关系。本研究强调了中国西南地区热带森林的生长、死亡、更新以及生产力对极端干旱事件的脆弱性。持续的气候变暖以及频发的干旱事件将会导致树木生长的下降和死亡率的增加，进而降低热带森林的碳汇能力，而这种影响对于演替早期的热带次生林更为严峻。【翻译:付培立】 Secondary tropical forests demonstrate superior growth rates. Policymakers and forest managers should prioritize these forests alongside primary forests for conservation and restoration efforts. Early successional tropical secondary forests are more vulnerable to hot‐dry climate. Forest managers should focus on the scientific and sustainable management of these forests to mitigate the effects of temperature extremes and drought. Climate warming threatens tropical tree growth, recruitment, and tropical forest carbon sink capacity. Experts need to develop proactive management practices and climate‐resilient strategies to address these challenges. 热带次生林具有较高的生长速率，因此决策者和森林管理者应加强对热带次生林的保护和恢复。 处于演替早期的热带次生林对干热气候更为敏感，因此森林的管理者应该加强对该类型森林科学和可持续管理以应对气候变化的影响。 气候变暖将威胁热带森林的生长、更新以及碳汇能力。因此应采取主动的管理手段和气候适应型的措施以应对这些挑战。 Tropical forests are vital components of the global carbon cycle and play an important role in mitigating climate change. However, the effects of climate change on the dynamics of these ecosystems are not fully understood. In this study, we explored how different types of tropical forests in Southwest China responded to climate change from 2004 to 2020. By tracking forest growth, mortality, regeneration, and productivity, we found that secondary forests, especially those at early successional (younger) stages, are more vulnerable to extreme climatic events like droughts and heat waves. These events reduced tree growth and regeneration, increased tree mortality, and impacted the forests' ability to fix carbon. Climate change, including rising temperatures and more frequent droughts, may decrease tropical forest growth, recruitment, and carbon sequestration while increasing tree mortality in the future. 热带森林是全球碳循环的关键组成部分，对于缓和气候变化的影响具有重要的作用，然而关于气候变化如何影响热带森林动态方面还有待于进一步的研究。本研究分析了气候变化对中国西南地区不同类型的热带森林在2004‐2020年影响。发现五个热带森林样地的生长、死亡、更新以及生产力均呈显著的年际变化。其中处于演替早期的热带森林对极端气候事件的响应更加敏感，极端干旱事件使得其树木的生长率、更新率以及树干净初级生产力的降低和死亡率升高。未来持续的气温变暖和频发的干旱事件将会降低热带森林的生长速率、更新率和固碳潜力。

[This corrects the article on p. 2050 in vol. 7, PMID: 28119725.].

In the \"Higgs basis\" for a generic 2HDM, only one scalar doublet gets a nonzero vacuum expectation value and, under the criterion of minimal flavor violation, the other one is fixed to be either color-singlet or color-octet, which are named as the type-III and type-C models, respectively. In this paper, the charged-Higgs effects of these two models on [Formula omitted]- [Formula omitted] mixing are studied. First of all, we perform a complete one-loop computation of the electro-weak corrections to the amplitudes of [Formula omitted]- [Formula omitted] mixing. Together with the up-to-date experimental measurements, a detailed phenomenological analysis is then performed in the cases of both real and complex Yukawa couplings of charged scalars to quarks. The spaces of model parameters allowed by the current experimental data on [Formula omitted]- [Formula omitted] mixing are obtained and the differences between type-III and type-C models are investigated, which is helpful to distinguish between these two models.