Understanding how terrestrial ecosystems would respond to future climate change can substantially contribute to scientific evaluation of the interactions between vegetation and climate. To reveal the ...future climate impacts might on the nature and magnitude of global vegetation, the spatiotemporal distribution and net primary productivity (NPP) of global terrestrial biomes and their dynamics in this century were quantitatively simulated and compared by using the improved Comprehensive and Sequential Classification System and the segmentation model. The 33 general circulation models under the four scenarios of Representative Concentration Pathways (RCPs) were utilized to simulate the future climate change. The multi-model ensemble results showed that at the global scale, the distribution of forests and deserts would expand by more than 2% and 4% over this century, respectively. By contrast, more than 11% of grassland regions would shrink. Despite the considerable differences in the simulated responses of the biomes, the poleward movement or expansion of temperate forest were prominent features across all the scenarios. Meanwhile, the terrestrial NPP was projected to increase by 7.44, 9.51, 9.46, and 12.02PgDW·a−1 in 2070s relative to 1970s in the RCP2.6, RCP4.5, RCP6.0, and RCP8.5, respectively. The largest NPP decrease would occur in tundra & alpine steppe. NPP in the Tropical Zone, the North Temperate Zone, and the North Frigid Zone was estimated to increase in this century, whereas NPP in the South Temperate Zone was projected to decrease slightly across all scenarios. Overall, ecosystems in the mid-/high latitudes would be more vulnerable to future climate change in terms of distribution ranges and primary productivity despite the existing uncertainties. Some vegetation would benefit from the warmer and wetter climate. However, most of these plants would suffer and experience irreversible changes, particularly in the northern hemisphere.
•The distribution and NPP of global terrestrial biomes during this century under the four RCPs were modeled.•The distribution of forests and deserts would expand at the expense of contraction of grasslands.•All GCMs agree that the terrestrial NPP would increase in this century.•The largest NPP decrease would occur in tundra & alpine steppe.•NPP in the South Temperate Zone was projected to decrease slightly.
•Distribution edges as natural labs to infer trees’ flowering response to warming.•Reduced chilling gains increasing importance in regulating tree flowering.•Apple bloom and late frost risk in ...contrasting climatic regions were investigated.•The redistribution of apple trees, northward or uphill, may be needed in Shaanxi.
The timing of flowering phenology in most temperate trees results from the interplay of winter chilling and spring heat. As global warming progresses, reduced chilling may gain increasing importance in regulating flowering dates, and eventually offset flowering advances in response to warmer springs. Later onset of flowering events may arise, with negative effects on plant fitness. However, delayed flowering in trees may also reduce the risk from late frosts. Different temperature conditions at both margins of the apple growing areas of Shaanxi in China provide a natural laboratory to examine the responses of trees’ flowering phenology and late frost risk to climate warming. We identified the chilling and heat accumulation periods for apples by Partial Least Squares regression of first flowering dates against daily chilling and heat accumulation rates during 2001–2016. We then analyzed the impacts of temperatures during these periods on flowering timing, and evaluated the frost risk for each site. Results indicated increasing importance of chilling temperatures from north to south, with greatest effects determined for the warmest site, where delayed blossom has been observed during the past 16 years. Since late frosts mostly occurred before tree flowering, only minor frost damage was detected for our study areas, with future delays in flowering likely to reduce the frost risk even further. The redistribution of apple trees to nearby locations with cold winters, either northward or uphill, could be a promising strategy to reduce the risk of insufficient chilling and ensure that production remains viable in a warming future.
•Seasonal, not annual climate variability drives grassland productivity.•Heat waves and drought in summer dominate the temporal variation in productivity.•Impacts of winter and spring warming may ...increase as warming trends continue.•Long-term (20 yr) grassland ANPP data were related with daily climate factors.
Strong correlations between aboveground net primary productivity (ANPP) of grasslands and mean annual temperature or precipitation have been widely reported across regional or continental scales; however, inter-annual variation in these climate factors correlates poorly with site-specific ANPP. We hypothesize that the reason for these weak correlations is that the impacts of climatic variation on grassland productivity depend on the timing and intensity of variation in temperature and precipitation. In this study, long-term records of grassland productivity on the Loess Plateau in China were related with daily temperature and precipitation during 1992–2011 using Partial Least Squares (PLS) regression to test the above-mentioned hypothesis. Our results suggested that temperature increases during the early stage of the growing season (April–May) were positively correlated with ANPP. However, these effects were canceled out when this phase was followed by a hot and dry summer (June–July). Impacts of drought and heat in August on productivity were negligible. Increased temperature and precipitation during the senescence period (September–October) and a warmer dormancy phase (November–March) were negatively correlated with productivity in the following year, while precipitation during the dormancy period had no detectable effects. Climatic variability in summer has thus far been the dominant driver of temporal variation in grassland productivity. Warming during winter and spring currently play minor roles, but it seems likely that the importance of these secondary impacts may increase as warming trends continue. This evaluation of climate variability impacts on ecosystem function (e.g. grassland productivity) implies that not only the magnitude but also the timing of changes in temperature and precipitation determines how the impacts of climate changes on ecosystems will unfold.
Drought is frequently recorded as a result of climate warming and elevated concentration of greenhouse gases, which affect the carbon and water cycles in terrestrial ecosystems, particularly in arid ...and semi-arid regions. To identify the drought in grassland ecosystems and to determine how such drought affects grassland ecosystems in terms of carbon and water cycles across the globe, this study evaluated the drought conditions of global grassland ecosystems from 2000 to 2011 on the basis of the remotely sensed Drought Severity Index (DSI) data. The temporal dynamics of grassland carbon use efficiency (CUE) and water use efficiency (WUE), as well as their correlations with DSI, were also investigated at the global scale. Results showed that 57.04% of grassland ecosystems experienced a dry trend over this period. In general, most grassland ecosystems in the northern hemisphere (N.H.) were in near normal condition, whereas those in the southern hemisphere (S.H.) experienced a clear drying and wetting trend, with the year 2005 regarded as the turning point. Grassland CUE increased continually despite the varied drought conditions over this period. By contrast, WUE increased in the closed shrublands and woody savannas but decreased in all the other grassland types. The drought conditions affected the carbon and water use mainly by influencing the primary production and evapotranspiration of grass through photosynthesis and transpiration process. The CUE and WUE of savannas was most sensitive to droughts among all the grassland types. The areas of grassland DSI that showed significant correlations with CUE and WUE were 52.92% and 22.11% of the total grassland areas, respectively. Overall, droughts sufficiently explained the dynamics of grassland CUE, especially in the S.H. In comparison with grassland CUE, the grassland WUE was less sensitive to drought conditions at the global scale.
With the deepening research of global change, studies of carbon cycle of grassland ecosystem, one of the widely distributed vegetation type, is of great significance in estimating global carbon ...cycle. Grassland degradation and desertification caused by human activities(such as land reclamation and grazing etc) is becoming increasingly serious in our country, so it is urgency to study the effects of human on grassland soil carbon. Under the condition of increasing measuring precision and region density, it is superior to use remote sensing in grassland carbon storage measurement through acquisition and inversion vegetation information and related biophysics parameters, it is possible to monitor the space distribution of grassland carbon-fixed amount in large range and multi-scale timely and accurately. In this paper, the importance of carbon cycle of grassland ecosystem was discussed, and researches on carbon cycle of grassland ecosystem in China was summarized and analysed, including the three carbon pools(plants carbon pool, litterfall carbon pool and soil carbon pool), effects of natural or human activities on carbon storage and methods to estimate the carbon storage. Additionally, based on the principal of grass growth, together with analysis of various global ecosystem NPP estimation methods, we put forward a novel thought to establish an carbon estimation model and testify its accuracy with meteorological data and field observation data such as grassland biomass, NPP, net ecological productivity (NEP) etc, which is much more suitable for carbon source/sink estimation of grassland ecosystem in China. At last, the existing problems and prospects of carbon source/sink researches of main grassland in China were discussed.
With the implementation of the Grain for Green Project, the apple plantation area is increasing in Loess Plateau. However, due to severe water scarcity, the sustainability of apple tree growth is ...threatened. In this paper, we used meteorological data (1990⁻2013) and forecasted climate data (2019⁻2050) to estimate water demand and establish a water suitability model to study the water balance between available water and water consumption of the apple trees. The results show that: (i) the order of the average water demand of apple plantation in each subarea is Shaanxi Province > Yuncheng area > Gansu Province > Sanmenxia Region, ranging from 500 to 950 mm; (ii) the temporal variability of water suitability from 1990 to 2013 is large, and the higher values are concentrated in the late growth stage of the apple trees and the lower values are concentrated in the early growth stage; (iii) the temporal and spatial distribution of water suitability is relatively stable and even in the Loess Plateau in the period of 2019⁻2050; (iv) the water suitability is mainly affected by effective precipitation and reference evapotranspiration and the reference evapotranspiration is mainly affected by the solar radiation (36%) and average temperature (38%). Furthermore, due to the joint influence of precipitation increases and solar radiation (average temperature) increases, the future water suitability of the apple plantation area in the Loess Plateau is showing a non-significant downward trend under RCP4.5 scenario.
Current climate change (e.g., temperature and precipitation variations) profoundly influences terrestrial vegetation growth and production, ecosystem respiration, and nutrient circulation. Grasslands ...are sensitive to climate change, and the carbon sequestration ability is closely related to water availability. However, how the terrestrial water budget influences regional carbon sequestration by the grassland ecosystem is still unclear. In this study, we modified a terrestrial biogeochemical model to investigate net ecosystem productivity (NEP) of Chinese grasslands under different aridity index (AI) levels from 1982 to 2008. The results showed that Chinese grasslands acted as a carbon sink of 33.7 TgC. yr-1, with a clear decrease in the spatial distribution from the humid end (near-forest) to the arid end (near-desert). During these 27 years, gross primary productivity (GPP) and net primary productivity (NPP) significantly increased with regional warming over the entire range of the AI, but no significant tendency was found for NEP. Meanwhile, only NPP in the arid zone (AR) and the semiarid zone (SAR) were significantly correlated with mean annual precipitation (MAP), and no significant correlation was found between heterotrophic respiration (Rh and MAP; NPP and Rh were both positively correlated with mean annual temperature (MAT) in all AI zones except for NPP in AR; no significant correlation between NEP and MAP or MAT was found. These results revealed that the grasslands with different AI levels keep different response patterns to temperature and precipitation variations. On the basis of these results, we predicted that the gap of carbon sequestration ability between humid and arid grassland will expand. The total carbon sink in Chinese grasslands will continue to fluctuate, but there is a danger that it might shrink in the future because of a combination of climatic and human factors, although CO2 fertilization and N deposition might partly mitigate this reduction.
The “Grain for Green” Program (GGP), which combats and reverses the landscape‐scale habitat degradation by converting agricultural lands to forests and grasslands, was launched in 1999 in western ...China. An assessment of the extent to which the GGP has altered the vegetation cover and ecological functions in these regions is much needed. The present study initially analyzed land use and cover change of forests and grasslands over western China between 2000 and 2015. A variety of satellite‐based ecological indicators, including net primary productivity, normalized difference vegetation index, leaf area index, carbon use efficiency, and water use efficiency, were used to reflect the biophysical consequences of the GGP in western China. Results indicated that the spatial extent of forests and grasslands increased by 13.97 × 103 and 11.13 × 103 km2, respectively, which were mainly converted from deserts and croplands. The ecosystem functions of forests and grasslands showed an asymmetric response in northwestern and southwestern China. The normalized difference vegetation index and water use efficiency of forests, as well as the net primary productivity and water use efficiency of grasslands, increased significantly over this period. The GGP also has led to an increase in leaf area index and carbon use efficiency of forests and grasslands. The Loess Plateau and the Three Rivers Source area represent the most effectively recovered regions in western China. Rising precipitation rates have contributed to vegetation recovery to some extent, especially in northwestern China, whereas the GGP was the prominent reason for the improvement of ecosystem functions across the entire region of western China.
Plain Language Summary
Land degradation has caused severe environmental problems in many areas worldwide and severely restrains the sustainable development of numerous local economies. Land degradation also undermines the livelihoods and food security of people, especially in the economically underprivileged regions. Western China has experienced land degradation because of both its geological location and climatic conditions. To combat and mitigate this situation, the Chinese government implemented a series of national‐scale ecological policies and programs during the late 1990s and early 2000s. Nearly 20 years have passed since the implementation of these projects. Therefore, it is appropriate to comprehensively assess the biophysical consequences of these programs. The present study aims to evaluate the extent to which the vegetation of western China recovered during the 2000–2015 period based on a variety of remotely sensed data streams. Results indicated that the spatial extent of forests and grasslands have expanded. The ecosystem functions of forests and grasslands showed an asymmetric response in the southwest and northwest regions of western China. These findings may provide guidelines for government agencies and policy makers involved in initiating adaptation strategies designed to adapt to climate change and to manage vegetation production.
Key Points
The transition from deserts to grasslands in northwestern China amounted to 51.54 × 103 km2 during the period 2000–2015
The ecosystem functions of forests and grasslands showed an asymmetric response in the southwestern and northwestern regions
The Loess Plateau and the Three Rivers Source region represent the mostly effectively recovered regions of western China
The effects of calcium chloride (CaCl₂), gibberellic acid (GA₃) and salicylic acid (SA) either alone or in various combinations on the fruit quality and chilling injury of honey peaches were ...investigated during 20 days of cold storage and subsequent 3 days of ambient temperature storage (simulating shelf life). Results showed that the effects of the combined treatments were better than those of each individual treatment. The combination of CaCl₂ and SA was the most effective treatment in alleviating chilling injury by controlling membrane permeability, inhibiting respiration rate and delaying polyphenol oxidase activity. The single CaCl₂ treatment was the most viable in maintaining fruit quality by keeping firmness and retarding weight loss rate during cold and subsequent ambient temperature storage. Therefore, the combined treatment of CaCl₂ and SA was the most effective in peach preservation, and the single CaCl₂ treatment can also be promoted. PRACTICAL APPLICATIONS: The combination of CaCl₂ and SA is an effective method in alleviating the chilling injury and keeping the storage quality of honey peaches under cold storage. The CaCl₂ treatment alone presents promising options for commercialization because of its low cost and ease of application. The significance of this research is ascribed to the postharvest application of nontoxic chemicals that cannot only extend the storage life of honey peaches, but can also promote the effectiveness of environmentally friendly methods in fruit storage. Overall, the outcomes of this study may serve as practical guidelines on honey peach storage for both fruit producers and consumers.
This paper aims to reveal the responses of global natural vegetation to future climate change in the twenty-first century. Thus, the dynamics of terrestrial net primary productivity (NPP) in three ...time slices, namely, 2030s, 2050s and 2070s are projected using a segmentation model that utilized 25 global climate models under the Representative Concentration Pathway 2.6 (RCP2.6) scenario. The results showed that forests would expand at the expense of grasslands and deserts in the current century. Terrestrial NPP is projected to increase globally from 127.04 ± 1.74 Pg DW·a⁻¹ in 2030s to 127.62 ± 2.57 Pg DW·a⁻¹ in 2070s. Temperate forest, the largest distributed vegetation, would contribute the most to the overall increase (548.50 Tg DW·a⁻¹). The NPP of warm desert, savanna, and tropical forest is projected to increase by 31.03, 248.45 and 111.25 Tg DW·a⁻¹, respectively. By contrast, the NPP of all the other vegetations would decline at the end of this century. In the tropical and the south temperate zones, terrestrial NPP is projected to decrease by 99.32 and 25.56 Tg DW·a⁻¹, respectively, with the difference lying in the increasing–decreasing trend in the former and the continually decreasing trend in the latter. However, terrestrial NPP in the north temperate and north frigid zones is projected to increase consistently by 639.43 and 57.73 Tg DW·a⁻¹, respectively. The “increase-peak-decline” trend of greenhouses gases described in the RCP2.6 would lead to the warming and cooling periods during this century. The vegetation NPP of various ecosystems or climate zones would respond differently to the future climate change. In general, ecosystems in northern high latitudes would become more vulnerable to future climate change compared to other vegetations.
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