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Climate change scenarios established by the Intergovernmental Panel on Climate Change (IPCC) have developed a significant tool for analyzing, modeling, and predicting future climate change impacts in different research fields after more than 30 years of development and refinement. In the wake of future climate change, the changes in forest structure and functions have become a frontier and focal area of global change research. This study mainly reviews and synthesizes climate change scenarios and their applications in forest ecosystem research over the past decade. These applications include changes in 1) forest structure and spatial vegetation distribution, 2) ecosystem structure, 3) ecosystem services, and 4) ecosystem stability. Although climate change scenarios are useful for predicting future climate change impacts on forest ecosystems, the accuracy of model simulations needs to be further improved. Based on existing studies, climate change scenarios are used in future simulation applications to construct a biomonitoring network platform integrating observations and predictions for better conservation of species diversity.

Long-term continuous monitoring of precipitation isotopes has great potential to advance our understanding of hydrometeorological processes that determine stable isotope variability in the monsoon regions. This study presents 4-yr daily precipitation isotopes from Yungui Plateau in southwestern China that are influenced by Indian summer monsoon and East Asian monsoon. The local meteoric water line (LMWL;δ2H = 8.12δ18O + 11.2) was first established at the Tengchong (TC) site, which was close to the global meteoric water line (GMWL;δ2H = 8δ18O + 10), indicating little secondary subcloud evaporation in the falling rain. Precipitationδ18O values exhibited significant inverse relationships with precipitation amount (r= −0.42), air temperature (r= −0.43), and relative humidity (r= −0.41) with lower correlation coefficients throughout the entire period, which indicated that precipitation isotopic variability in TC could not be well explained by the local meteorological factors but influenced by other combined factors of regional precipitation amount and upstream rainout. Precipitationδ18O values showed a clear V-shaped trend throughout the observation period, characterized by higherδ18O values during the premonsoon period whereas lower values during the postmonsoon period. This seasonal variation of precipitationδ18O values was associated with the seasonal movement of the intertropical convergence zone and seasonal changes in moisture transport. Combined with backward trajectory analysis, precipitationδ18O values were estimated by a Rayleigh distillation model showing that upstream rainout processes from the Bay of Bengal (BoB) toward land (Myanmar) and recycling moisture over land were key factors affecting the isotopic compositions of the TC precipitation. These findings could enhance our understanding of atmospheric dynamics and moisture source in the monsoon regions and will potentially facilitate the interpretation of numerous isotopic proxy records from this region.SIGNIFICANCE STATEMENTThe variability of the summer monsoon and its onset, duration, and failure directly determine the strong rainfall and drought in a given region and have great impacts on regional societies and agriculture. To better understand this variability, this study presented a 4-yr daily dataset of precipitation isotopes on the Yungui Plateau of southwestern China to explore atmospheric processes and moisture sources that drive isotopic variability in this region. Precipitationδ18O exhibited remarkably seasonal variability, with higher values in premonsoon period and lower values in the postmonsoon period. During the Indian summer monsoon period, moisture sources primarily originated from the BoB toward the TC site, experiencing rainout processes and local moisture recycling over land using a Rayleigh fractionation model. These findings shed new light on the temporal variations of precipitation stable isotopes and facilitate our understanding of hydrological cycle in the monsoon regions.

The study on precipitation isotope variation can potentially improve the understanding of weather processes, regional water cycle and paleoclimate reconstruction in the subtropical monsoon region. Based on the measured stable isotope composition in precipitation (δ18Op) and daily precipitation from January 2010 to December 2021 in Changsha of the subtropical monsoon region of eastern China, the δ18Op variations, amount effect and local meteoric water line (LMWL) were analyzed and compared on daily, monthly and annual time scales, as well as under different precipitation intensities. The results showed that, on the daily time scale, δ18Op was significantly and negatively correlated with precipitation in the study area. Influenced by subcloud evaporation, small precipitation events (≤5 mm/d) could change the rainout level of precipitation isotopes. There were significant differences in the slope and intercept of the LMWL on different time scales, in different seasons and under different precipitation intensities. On the daily and monthly time scales, the slope and intercept of the LMWL in the cold half of the year were significantly smaller and larger than those in the warm half of the year, respectively, and the slope and intercept of the LMWL increased significantly with precipitation intensity, and then remained largely stable. On the annual time scale, the slope and intercept of the LMWL in the cold half of the year were smaller than those in the warm half of the year. The possible reasons for the differences in the LMWL on different time scales are the combined effects of seasonal differences in precipitation intensity and water vapor sources.

As regional heterogeneity on the Qinghai Tibetan Plateau (QTP), the “greening rate” between alpine steppe in the west and alpine meadow ecosystems in the east is difference during the past several decades. To investigate the difference, the net photosynthetic rate (An) and the supply (mesophyll conductance ( g), stomatal conductance ( g)) and demand (the maximum rates of Rubisco carboxylase activity ( V) and photosynthetic electron transport ( J)) for CO of three plants functional types (PFTs) were measured. Other functional traits and influencing factors were compared among ecosystems along the altitudinal gradients of QTP. The An of the PFTs was simulated under potential future conditions. At high altitudes, grass was found to maintain a relatively stable An by decreasing V, J, and g, while slightly increasing g, compared with that at a low altitude. The An of sedge and shrubs increased with rising V, J and g and g values, resulting in a large increment in the An at low altitudes. Grass seemed to be less sensitive to the environment by reducing the supply of and holding onto CO , while sedge and shrub increased both. Grass and sedge should be divided into two PFTs rather than remaining as one based on their opposite physiological and morphological functions in response to climate change. The ecosystem at 3600 m was transitional. C was likely to be a more dominant factor than T in affecting the An of grass. The order of rising An in PFTs was shrub > sedge > grass and the An of alpine meadow was found to increase more under the two future climate scenarios.

In many arid ecosystems, vegetation frequently occurs in high-cover patches interspersed in a matrix of low plant cover. However, theoretical explanations for shrub patch pattern dynamics along climate gradients remain unclear on a large scale. This context aimed to assess the variance of the Reaumuria soongorica patch structure along the precipitation gradient and the factors that affect patch structure formation in the middle and lower Heihe River Basin (HRB). Field investigations on vegetation patterns and heterogeneity in soil properties were conducted during 2014 and 2015. The results showed that patch height, size and plant-to-patch distance were smaller in high precipitation habitats than in low precipitation sites. Climate, soil and vegetation explained 82.5% of the variance in patch structure. Spatially, R. soongorica shifted from a clumped to a random pattern on the landscape towards the MAP gradient, and heterogeneity in the surface soil properties (the ratio of biological soil crust (BSC) to bare gravels (BG)) determined the R. soongorica population distribution pattern in the middle and lower HRB. A conceptual model, which integrated water availability and plant facilitation and competition effects, was revealed that R. soongorica changed from a flexible water use strategy in high precipitation regions to a consistent water use strategy in low precipitation areas. Our study provides a comprehensive quantification of the variance in shrub patch structure along a precipitation gradient and may improve our understanding of vegetation pattern dynamics in the Gobi Desert under future climate change.

Plant transpiration depends on environmental conditions, and soil water availability is its primary control under water deficit conditions. In this study, we improve a simplified process‐based model (hereafter “BTA”) by including soil water potential (ψₛₒᵢₗ) to explicitly represent the dependence of plant transpiration on root‐zone moisture conditions. The improved model is denoted as the BTA‐ψ model. We assessed the performance of the BTA and BTA‐ψ models in a subtropical monsoon climate and a Mediterranean climate with different levels of water stress. The BTA model performed reasonably in estimating daily and hourly transpiration under sufficient water conditions, but it failed during dry periods. Overall, the BTA‐ψ model provided a significant improvement for estimating transpiration under a wide range of soil moisture conditions. Although both models could estimate transpiration (sap flow) at night, BTA‐ψ was superior to BTA in this regard. Species differences in the calibrated parameters of both models were consistent with leaf‐level photosynthetic measurements on each species, as expected given the physiological basis of these parameters. With a simplified representation of physiological regulation and reasonable performance across a range of soil moisture conditions, the BTA‐ψ model provides a useful alternative to purely empirical models for modelling transpiration.

Long-term continuous monitoring of precipitation isotopes has great potential to advance our understanding of mechanisms that determine stable isotope variability in hydrological processes of monsoon regions. This study presents a 4-year daily data set of precipitation isotopes from Yungui Plateau of southwest China, influenced by southwest monsoon and East Asian monsoon. The local meteoric water line [LMWL, δ2H=8.12 (±0.04) δ18O+11.2(±0.4)] was established at the Tengchong (TC) site, which was similar to the global meteoric water line (GMWL, δ2H=8 δ18O+10) indicating little secondary sub-cloud evaporation in the falling rain. Precipitation δ18O exhibited significant inverse relationships with precipitation amount (r = -0.42) and air temperature (r = -0.43) throughout the entire period, which indicated that precipitation isotopic variability largely depended on the local meteorological conditions. Precipitation δ18O values are characterized by remarkably seasonal variability: In the summer monsoon period, moisture sources primarily originated from BoB source towards TC site experiencing local moisture recycling over land. The air masses were derived from the northern region of Africa and East Asia with the longest transporting distance and cyclonic activity over the source region in the Fall-winter period characterized with the depleted δ18O values. Precipitation δ18O at the TC site was estimated by a Rayleigh fractionation model considering rainout over BoB and land (Myanmar) during the vapor advection, and local recycling processes consistent with the observed precipitation δ18O values. These findings enhance our understanding of hydrological cycle in the Southwest monsoon regions and will potentially facilitate the interpretation of numerous isotopic proxy records from this region.

The demand for social and economic development has promoted research into water resources. The combined effects of natural conditions and human activities on regional water resource usage are not well understood. The sustainable utilization of water resources was assessed in terms of supply (e.g., precipitation) and demand (e.g., ecological water resources footprint (EFw)) sides in Hunan Province, China, from 2010 to 2019. The results showed that: (1) on the supply side, water resources were increased across Hunan Province. The spatial patterns of total water resources are significantly heterogeneous, with high values in the east and south, which are mainly affected by precipitation; (2) on the demand side, evapotranspiration was great in areas with high vegetation coverage. The EFw was high in relatively developed areas. The mean percentage of agricultural EFw remained dominant at approximately 60% with a steady decreasing trend, while that of eco-environmental EFw increased; and (3) the sustainable utilization of water resources in Hunan Province is generally rational. Moreover, the potential for water resource development and utilization is really significant in eastern and southern Hunan Province. The findings are beneficial in providing an important scientific basis for policymaking relating to the efficient utilization of regional water resources.

In recent decades, terrestrial vegetation in the northern hemisphere (NH) has been exposed to warming and more extremely high temperatures. However, the consequences of these changes for terrestrial vegetation growth remain poorly quantified and understood. By examining a satellite-based vegetation index, tree-ring measurements and land-surface model simulations, we discovered a consistent convex pattern in the responses of vegetation growth to temperature exposure (TE) for forest, shrub and grass in both the temperate (30°−50° N) and boreal (50°−70° N) NH during the period of 1982−2012. The response of vegetation growth to TE for the three vegetation types in both the temperate and boreal NH increased convergently with increasing temperature, until vegetation type-dependent temperature thresholds were reached. A TE beyond these temperature thresholds resulted in disproportionately weak positive or even strong negative responses. Vegetation growth in the boreal NH was more vulnerable to extremely high-temperature events than vegetation growth in the temporal NH. The non-linear responses discovered here provide new insights into the dynamics of northern terrestrial ecosystems in a warmer world.

Snow is a crucial component of the cryosphere and its has been experiencing a significant decline for the Northern Hemisphere (NH) (35–90°N) snow cover extent (SCE) in March-April over the 1948–2012 period. However, the causes of this historical snow cover decline are still uncertain. Here, based on the Global Land Data Assimilation System version 2.0 (GLDAS) reanalysis reanalyzed snow cover extent (SCE) and climate model simulations that separate different anthropogenic forcings, we attribute changes of spring SCE over the NH to anthropogenic and natural climate forcings using an optimal fingerprint technique. We find that fingerprints from greenhouse-gases (GHG) and stratospheric aerosols can be clearly detected in the historical SCE records, whereas natural forcing has not contributed to the long-term SCE trend in a discernible way. The GHG-induced warming is primarily responsible for the NH SCE decline, which, however, has been partly offset (by ∼16%) by aerosol-induced climatic cooling. Our findings confirm the negative effect of warming on SCE changes yet highlight the positive role of aerosols in slowing SCE decline over the past 65 years.

Vegetation water use is closely related to its biophysical functioning and is often under stress from various environmental factors. However, commonly used root water uptake models only consider the stress from root zone moisture availability. There is a need to incorporate the stress from both the above-ground factors and root zone water condition. In this study, a newly developed coupled supply- and demand-induced (S&D) root water uptake model is examined with measurements on two tree species, Guihua in the subtropical monsoon climate and Drooping Sheoak in the Mediterranean climate. The results show that the S&D model outperforms a supply-constraint water stress function (the S-shape model) for both studied species. The S&D model predicts 67% and 84% temporal variability in the measured water stress for Guihua and Drooping Sheoak, respectively. The improvement of the S&D model over the S-shape model is more significant for Guihua than for Drooping Sheoak, which might be associated with the specific climate conditions. A two-step parameterization approach is adopted in this study for the S&D model, and is recommended for future applications. These results further support the validity of the S&D model, and should be considered for the root water uptake modeling.

In view of future changes in climate, it is important to better understand how different plant functional groups (PFGs) respond to warmer and drier conditions, particularly in temperate regions where an increase in both the frequency and severity of drought is expected. The patterns and mechanisms of immediate and delayed impacts of extreme drought on vegetation growth remain poorly quantified. Using satellite measurements of vegetation greenness, in-situ tree-ring records, eddy-covariance CO2 and water flux measurements, and meta-analyses of source water of plant use among PFGs, we show that drought legacy effects on vegetation growth differ markedly between forests, shrubs and grass across diverse bioclimatic conditions over the temperate Northern Hemisphere (NH). Deep−rooted forests exhibit a drought legacy response with reduced growth during up to 4 years after an extreme drought, whereas shrubs and grass have drought legacy effects of approximately 2 years and 1 year, respectively. Statistical analyses partly attribute the differences in drought legacy effects among PFGs to plant eco-hydrological properties (related to traits), including plant water use and hydraulic responses. These results can be used to improve the representation of drought response of different PFGs in land surface models, and assess their biogeochemical and biophysical feedbacks in response to a warmer and drier climate. This article is protected by copyright. All rights reserved.

With the increasing temperature and intensified drought, global climate change has profound impacts on tree growth in temperate regions, which consequently regulates terrestrial-atmosphere biogeochemical processes and biophysical feedbacks. Thus, increasing numbers of studies have addressed the long-term annual trends in tree growth and their response to climate change at diverse spatial scales. However, the potential divergence in tree growth trends and growth variability (represented by coefficient of variance) in different seasons across large-scale climate gradients remains poorly understood. Here, we investigated the tree growth trends and growth variability in different seasons across diverse drought conditions in forested regions over northeastern China during the period 1982&ndash, 2015, using both remote sensing observations and in situ tree-ring measurements. We found clear seasonal divergence in tree growth trends during 1982&ndash, 2015, and the apparent increase was mainly observed in spring and autumn, attributed mainly to the increase in spring temperature and autumn solar radiation, respectively, but not in summer. The magnitudes of increasing trends in tree growth decrease with the increase of the multi-year average dryness index (MAI) in semi-arid areas (1.5 &lt, MAI &lt, 4.0) in all seasons. We further revealed that the interannual variability in tree growth was much larger in the semi-arid regions than in the humid and semi-humid regions in all seasons, and tree growth variability was significantly and negatively correlated with the variations in temperature and water deficit. Our findings improve our understanding of seasonal divergence in tree growth trends and provide new insights into spatial patterns in forest vulnerability in a warmer and drier climate.