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Crown removal revitalises sand‐fixing shrubs that show declining vigour with age in drought‐prone environments; however, the underlying mechanisms are poorly understood. Here, we addressed this knowledge gap by comparing the growth performance, xylem hydraulics and plant carbon economy across different plant ages (10, 21 and 33 years) and treatments (control and crown removal) using a representative sand‐fixing shrub (Caragana microphylla Lam.) in northern China. We found that growth decline with plant age was accompanied by simultaneous decreases in soil moisture, plant hydraulic efficiency and photosynthetic capacity, suggesting that these interconnected changes in plant water relations and carbon economy were responsible for this decline. Following crown removal, quick resprouting, involving remobilisation of root nonstructural carbohydrate reserves, contributed to the reconstruction of an efficient hydraulic system and improved plant carbon status, but this became less effective in older shrubs. These age‐dependent effects of carbon economy and hydraulics on plant growth vigour provide a mechanistic explanation for the age‐related decline and revitalisation of sand‐fixing shrubs. This understanding is crucial for the development of suitable management strategies for shrub plantations constructed with species having the resprouting ability and contributes to the sustainability of ecological restoration projects in water‐limited sandy lands. Summary statement: Embolism accumulation restricted carbon assimilation in aging shrubs and resulted in growth decline, while the crown‐removal treatment revitalised plants by promoting the construction of new hydraulic systems in resprouts and enhancing carbon balance through the removal of dysfunctional old stems. [ABSTRACT FROM AUTHOR]

Differences in key physiological characteristics between plant species can result in their contrasting performances in vegetation restoration projects, but ecophysiological comparative studies in close relation to ecological restoration projects are scarce. Hedysarum fruticosum Pall. and Caragana microphylla Lam. are two leguminous shrub species widely used in combination for fixation of active sand dunes in semiarid regions of northern China, but they clearly differ in fitness at different stages of dune vegetation development; that is, H. fruticosum quickly gains a community dominance at the initial stage but yields to C. microphylla in a few years after the fixation of dunes. To reveal the underlying mechanism of such a pattern, key physiological characteristics related to xylem water transport, leaf water use, and drought tolerance were compared between these two species at a typical site of sand dune fixation project in Inner Mongolia. Compared with C. microphylla, H. fruticosum shows an acquisitive and risky water management strategy with substantially higher hydraulic efficiency and photosynthetic capability but reduced resistance to drought‐induced xylem embolism, which endows it an advantage under conditions of relatively high soil water availability at the early stage of dune fixation. In contrast, C. microphylla exhibits more conservative water use and characteristics of greater drought tolerance, which results in greater dominance under the more drought‐stressed conditions of the later stage of dune fixation. Our study for the first time provides a potential mechanistic explanation for the clear switching of dominant positions between the two important sand‐fixing shrub species during the sand dune revegetation process. [ABSTRACT FROM AUTHOR]

• Tree growth and response to climate warming are related to xylem hydraulics. • High hydraulic efficiency is an important basis for fast radial growth. • Temperature is the main climatic factor controlling tree growth in Northeast China. • Growth accelerated in two conifers accompanying temperature increase since 1990s. • The warming-drying trend may reverse the increased radial growth at low elevations. Tree-ring analysis provides an effective way to detect complex responses of trees to climate warming and has been extensively used in ecological studies; however, there is often a lack of simultaneous physiological investigations explaining the observed patterns. Here, we paralleled dendroclimatic analyses with hydraulics measurements in co-occurring Larix olgensis and Pinus koraiensis trees along an elevational gradient (low, middle and high) in Northeast China. We aimed to detect potential differences in patterns of growth and responses to climate warming between the two conifer species considering their distinctions in life history strategy and key functional traits and to provide a mechanistic explanation for such differences. Our tree-ring analyses showed that L. olgensis trees exhibited a linear increase in basal area increment at the initial part of lifetime while Korean pine trees usually have a long slow growth period up to several decades at the juvenile stage. Consistent with their contrasts in growth rate, the larch species showed significantly higher hydraulic conductivity and functional traits favoring more efficient carbon gain at the shoot level compared to sympatric Korean pine trees. Results of the dendroclimatological analyses indicate that temperature rather than precipitation is the controlling factor for growth in both species under the current climate regime. Radial growth of both species overall accelerated accompanying the rapid warming since 1990s except a significant decrease in growth for Korean pine trees at the low elevation site, which is likely due to stronger competitions from co-occurring broadleaf trees in the mixed forest environments. In the larch species, the substantially lower degree of response in growth at the low elevation site compared to trees at higher elevations suggests that the drying effect of warming at the low elevation may have to a certain degree offset the beneficial effects of warming on growth of larch trees. [ABSTRACT FROM AUTHOR]

• Soil moisture significantly decreased with the stabilization of sand dunes. • Shrubs of different dune fixation stages showed contrasting functional traits. • High hydraulic efficiency and prodigal water use allowed success in active dunes. • Strong hydraulic safety and water conservation enabled persistence in fixed dunes. Dominating sand-fixing shrubs play crucial roles in the stabilization and rehabilitation of sand dunes. Different sand-fixing shrub species often separate along the temporal-spatial environmental gradient during the sand dune stabilization process; however, the physiological mechanisms underlying such a separation remain poorly understood, which limits our ability to identify the causes of land desertification and the cruxes of rehabilitation. We investigated xylem hydraulics and water use characteristics of four important shrub species used for sand dune fixation projects in northern China that show distinct preferences to different stages of dune stabilization, i.e. two species succeed in active dunes and the other two in fixed dunes. The major aim was to examine the roles of xylem hydraulics, water use and the coordination of these two aspects in determining the habitat preferences of sand-fixing shrubs along the process of dune stabilization in water-limited environments. The two active-dune species consistently exhibited higher stem hydraulic conductivity but lower resistance to drought-induced xylem embolism than the two fixed-dune species, which reflects contrasting requirements to shrub hydraulic functionality in sand dunes of the two successional stages that differ substantially in soil water regimes. In coordination with contrasts in hydraulics, they also diverged clearly in water use strategies with the fixed-dune shrubs showing more conservative water use. Our results highlight the critical roles that hydraulics and water utilization play in determining the adaptation of dominating sand-fixing shrub species to their respective environments shaped by the plant-soil interactions during sand dune vegetation development. [ABSTRACT FROM AUTHOR]