Guang-You Hao

Stem growth and canopy activity are two of the key processes in trees and are associated with one another. These two processes and their relationships may be altered under climate change, yet the underlying mechanisms by which climatic factors impact them remain unclear. This study examined stem growth and canopy activity and their responses to climate using tree-ring width data from 614 increment cores and satellite-based normalized difference vegetation index (NDVI) data from 17 Mongolian pine (Pinus sylvestris var. mongolica Litv.) plantation sites in northern China. Stem growth was not significantly (p > 0.05) correlated with canopy activity at both broad spatial and individual-site scales. Broadly, stem growth was primarily driven by temperature-induced water stress whereas canopy activity was constrained by growing season precipitation, causing a difference in the spatial patterns of these two processes across the Mongolian pine plantations. Locally, stem growth was more vulnerable to high-temperature-exacerbated drought stress during the growing season and more affected by pre-growing-season hydroclimatic variability than canopy activity, especially at more arid sites, which could decouple interannual correlations between the two processes. Our study reveals climate-driven decoupling between stem growth and canopy activity, complicating the estimations of overall carbon dynamics, and thereby underscores the necessity of comprehensively assessing forest dynamics and carbon sequestration.

Drylands worldwide face high pressure to expand agricultural production while reversing land degradation. Whether higher production also brings more balanced ecosystem benefits remains unclear. Here, using 34 years of data from a typical dryland agro-pastoral region in northern China, we show that landscapes can have enhanced combinations of services while becoming less balanced. We measured crop production, grazing support and water purification, and used this frontier proximity as a measure of technical efficiency. Technical efficiency increases over time but balance among services declines and high efficiency-low balance areas are highly persistent over time. Wetter conditions contribute to rising efficiency, whereas service balance depends more on grassland retention, land use composition and initial conditions. An increase of 7.5% in grassland area marks the fitted crossover, where balanced outcomes became more likely than specialized ones. Dryland governance should therefore evaluate production gains together with service balance and land use structure, since rising efficiency can mask a narrowing of ecosystem service portfolios.

Functional traits are widely used to explain plant performance including growth rate; however, how above‐ and below‐ground traits coordinate in affecting resource acquisition, transportation and utilization that jointly determine long‐term tree growth remains understudied. In a common garden, we quantified stem radial growth rates based on tree‐ring analyses and measured 24 economic and hydraulic traits of leaves, stems, coarse roots and fine roots in 33 temperate broad‐leaved tree species that co‐occur in forests of Northeast China. Beyond testing individual trait–growth relationships, trait network and whole‐plant economics spectrum (PES) analyses were used to uncover the physiological mechanisms underlying growth rate differences across tree species. Across species, growth rate correlated positively with multiple functional traits: leaf photosynthetic rate ( A _a ), leaf mass per area (LMA), fine‐root average diameter (AD) and hydraulic conductance in both above‐ and below‐ground organs. Notably, the traits reflecting carbon assimilation and hydraulic efficiency consistently emerged as ‘hub traits’ with high connectivity in the trait networks at both organ and whole‐plant levels, and they also tended to show stronger linear correlations with growth rate. Our results revealed a PES ranging from an acquisitive strategy represented by higher carbon assimilation rate, more efficient water transport across organs, thicker fine roots and lower wood tissue investment, associated with fast tree growth, to a conservative strategy represented by a combination of opposite trait values, associated with slow growth. Synthesis . Our findings highlight the predictive roles of individual traits related to carbon acquisition, water transportation, soil resource capture and tissue investment in growth. The trait network and spectrum analyses further present a more integrative framework for explaining interspecific variation in tree growth rate, which provides novel and comprehensive insights into the mechanistic understanding and prediction of tree productivity at the species level from a trait‐based perspective.

Temperate ring‐porous tree species are more vulnerable to freezing‐induced embolism than their diffuse‐porous counterparts due to their large earlywood vessels. Although ring‐porous species can restore hydraulic function by forming earlywood vessels in early spring, they may face high risk of embolism during spring frosts. Here, we tested the hypothesis that ring‐porous temperate trees employ a strategy of enhanced freezing avoidance to protect their vulnerable earlywood vessels from the risk of freezing‐induced embolism. We quantified the degree of embolism in overwintering stems, ice nucleation temperature (INT _xylem ), water content (WC _xylem ), and non‐structural carbohydrate (NSC) concentrations in stem xylems of 20 temperate tree species (nine diffuse‐porous and 11 ring‐porous) grown in a common garden. Consistent with our hypothesis, ring‐porous species suffered severe embolism over the winter and exhibited stronger freezing avoidance during spring. While diffuse‐porous species rely on smaller vessels to resist freezing‐induced embolism, ring‐porous species showed stronger ability of freezing avoidance by lowering INT _xylem via reduced WC _xylem and higher NSC concentrations. This strategy likely protects their vulnerable, newly developed earlywood vessels from freezing‐induced hydraulic dysfunction. These findings reveal distinct strategies between temperate diffuse‐porous and ring‐porous species for coping with spring frost stress, providing insights into forest responses to climate change.

Hydrological intensification in desert oases decouples food production from aridity, yet how irrigation‐supported blue‐water consumption (BWC) reshapes nonlinear trade‐offs among ecosystem services remains uncertain. We examined crop production (CP), soil conservation (SC), and water purification (WP) in the Hetao Irrigation District from 2001 to 2023 using multisource earth observation, generalized additive models, pairwise interaction analysis, and path analysis. CP increased by 22.5% from 1.80 to 2.21 t ha ⁻¹ , while mean BWC rose from 37.7 to 130.2 mm. In contrast, SC varied strongly among years (0.80–3.33 t ha ⁻¹ ) and WP remained stable (0.78–0.80) but showed divergent spatial trends. CP increased almost monotonically with BWC, whereas SC declined sharply at low BWC and WP showed a hump‐shaped response, with the transition from positive to negative marginal sensitivity occurring at approximately 170–180 mm BWC. BWC reshaped the geometry and turning points of service relationships more strongly than climatic water balance, which mainly altered interaction magnitude. High BWC helped sustain CP during dry years but kept SC–WP coordination in a low‐synergy state and did not reproduce the broader CP–WP synergies observed under wet conditions. Path analysis further showed that stable croplands were characterized by a stronger BWC–CP linkage and landscape configuration constraints on regulating services, whereas expanding croplands were more strongly limited by temperature, sandy soils, and alkaline soil conditions. These results indicate that blue‐water‐dependent intensification can stabilize production but narrow the conditions for regulating service synergy, highlighting the need to reduce excessive blue‐water dependence in stable croplands and restrict expansion onto edaphically constrained margins.

Resource acquisition, transport, storage and utilization are key determinants of plant performance. Functional coordination and trade-offs are well explored in a conceptual framework of the plant economics spectrum, but how different organs coordinate across these resource dimensions to optimize whole-plant strategies remains largely unclear. We measured 47 functional traits of leaves, stems, coarse roots and fine roots in 33 co-occurring broadleaf tree species from temperate forests in Northeast China, to examine aboveground–belowground coordination across four above-mentioned resource dimensions. We found decoupling between leaves and fine roots in resource acquisition. No significant relationships were observed between leaf and fine root traits associated with acquisition efficiency (leaf photosynthetic rate–specific fine-root length; specific leaf area–specific fine-root area) or spatial occupation (leaf thickness–fine-root diameter; leafing intensity–fine-root branching intensity), supporting functional independence between the two resource-acquiring organs. In contrast, aboveground and belowground organs exhibited coordinated patterns in resource transport. Stem and coarse-root hydraulic efficiency showed positive correlations, and leaf venation density was positively correlated with coarse-root vessel diameters, which also increased with stem vessel diameters. Similar inter-organ relationships were found in resource storage. Nonstructural carbohydrate storage, especially starch, showed synchronized variation between stems and coarse roots, alongside their structural alignments in axial and total parenchyma fractions. As for resource utilization, leaf lamina mechanical resistance (punching force) was positively correlated with coarse-root mechanical strength (modulus of elasticity and rupture), which also positively covaried with corresponding modulus of elasticity and rupture in stems. Additionally, leaf and fine-root tissue density, stem and coarse-root wood density, and stem and coarse-root dry matter content all showed significant positive correlations. These coordinations collectively support the integrated whole-plant strategies in resource transport, storage and utilization. Our work reveals aboveground–belowground specialization and integration patterns, advancing the understanding of whole-plant functioning and its underpinning mechanisms across deciduous broad-leaved species in temperate forests.

Summary statement: The adaptive significance of vestured pits in desert shrubs lies in their capacity to enhance drought‐induced xylem embolism resistance and, in the meantime, allow for relatively high hydraulic efficiency; however, this adaptation comes at a cost of increased susceptibility to freezing‐induced embolism.