Elevated CO₂ enhances leaf senescence during extreme drought in a temperate forest

In 2007, an extreme drought and acute heat wave impacted ecosystems across the southeastern USA, including a 19-year-old Liquidambar styraciflua L. (sweetgum) tree plantation exposed to long-term elevated (E(CO(2))) or ambient (A(CO(2))) CO(2) treatments. Stem sap velocities were analyzed to assess plant response to potential interactions between CO(2) and these weather extremes. Canopy conductance and net carbon assimilation (A(net)) were modeled based on patterns of sap velocity to estimate indirect impacts of observed reductions in transpiration under E(CO(2)) on premature leaf senescence. Elevated CO(2) reduced sap flow by 28% during early summer, and by up to 45% late in the drought during record-setting temperatures. Modeled canopy conductance declined more rapidly in E(CO(2)) plots during this period, thereby directly reducing carbon gain at a greater rate than in A(CO(2)) plots. Indeed, pre-drought canopy A(net) was similar across treatment plots, but declined to ～40% less than A(net) in A(CO(2)) as the drought progressed, likely leading to negative net carbon balance. Consequently, premature leaf senescence and abscission increased rapidly during this period, and was 30% greater for E(CO(2)). While E(CO(2)) can reduce leaf-level water use under droughty conditions, acute drought may induce excessive stomatal closure that could offset benefits of E(CO(2)) to temperate forest species during extreme weather events.     

Vertical and seasonal variation in the δ¹³C of leaf-respired CO₂ in a mixed conifer forest

The C-isotopic composition (δ13C) of leaf respiration (δ(LR)) has previously been shown to vary among functional groups, plant organs and times of day. We here investigated vertical and seasonal variation in δ(LR) through deep (~35 m) forest canopies. We measured δ(LR), δ13C of leaf bulk organic matter (δ(LB)), specific leaf area, net photosynthesis (A) and dark respiration in shade, middle and sun foliage in four conifer species from May to August. We used Keeling plots to estimate δ(LR); we developed a novel technique for ensuring that the respiratory substrate was not changing over the course of the measurement. Variables δ(LR) and δ(LB) displayed a vertical pattern in Abies grandis, Pseudotsuga menziesii and Thuja plicata, but were independent of canopy position in Larix occidentalis. Vertical gradients in δ(LB) (3.6‰) and δ(LR) (2.8‰) were similar. The respiratory enrichment (δ(LR)-δ(LB)) was smaller in expanding (3‰) than mature (4-8‰) foliage. There was a linear relationship between the respiratory enrichment and A. Our data support the hypothesis that δ(LR) values are related to patterns of C allocation among metabolic pathways. We demonstrated that considerable variation in δ(LR) occurs vertically through the canopy (3‰ gradient) and seasonally (3-7‰). Understanding sources of variation in respiratory signals is fundamental to comprehending C dynamics and for global model applications.     

Does strategy of resource acquisition in tropical woody species vary with life form,leaf texture,and canopy gradient?

In order to test whether the strategy of resource acquisition varies with life form, leaf texture and canopy gradient, we measured light-saturated net photosynthetic capacity (A _max-mass) and leaf nitrogen and phosphorus concentrations (N _mass and P _mass) for 127 woody species of understory (small shrubs and tree seedlings) and 47 woody species of canopy (large shrubs and tree adults) in a tropical montane rain forest of Hainan Island, South China. Photosynthetic nitrogen use efficiency (PNUE) and photosynthetic phosphorus use efficiency (PPUE) were studied by taking into account functional groups, which classified by either life form (FG1) or leaf texture (FG2). For FG1, there were significant (P < 0.05) differences between trees and shrubs in A _mass, N _mass and P _mass, but not in PNUE and PPUE; whereas for FG2, there were significant (P < 0.05) differences between the papery-leaved species and those with leathery leaves in the measured leaf traits inclusive of PNUE and PPUE. Within the same classification systems, significant allometric scaling relationships were found in the leaf trait pairs of A _mass-N _mass and A _mass-P _mass. Considered separately, the slope and y-intercept of the linear regression between A _mass and N _mass did not differ among functional groups nor between understory and canopy, but those for the linear regression between A _mass and P _mass differed significantly (P = 0.001) between understory and canopy species regardless of functional groups. The results of phylogenetic comparative analyses were in accordance with the observed positive scaling relationships. The overall results indicate that there are no fundamentally different nitrogen capture strategies in tropical woody species regardless of their life form, leaf texture and canopy gradient. However, the strategies of phosphorus acquisition of tropical woody species differ with canopy layer increases. This variation may correspond to the special soil conditions in this ecosystem, as phosphorus is an element limiting plant growth in tropical areas.     

Biodiversity of arbuscular mycorrhizal fungi in different trees of madhupur forest, Bangladesh

Roots and rhizosphere soils of Acacia auriculiformis A. Cunn. ex Benth., A. mangium Wild., Artocarpus heterophyUus Lamk. C., Dalbergia sissoo Roxb. ex A. P. D., Eucalyptus camaldulensis Dehnn., Hevea brasiliensis （Wild. ex Juss） Muell. Arg., Swietenia macrophylla King. and Tectona grandis L. were collected from different locations of Madhupur forest area to study the biodiversity of Arbuscular Mycorrhizal （AM） fungal colonization and spore population. All the plants showed AM colonization. Out of eight selected plants, mycelial colonization was lowest in the roots of A. heterophyllus （22%） and the highest was in the roots of H. brasiliensis （78%）. Mycelial intensity was observed poor （25%-77%） and moderate （23%-57%） in all plants species and abundant （11%-40%） was in most of the plant species. Vesicular colonization was observed in five plant species. The lowest was recorded in E. camaldulensis （4%） and the highest was in H. brasiliensis （21%）. Poor （24%-56%）, moderate （16%-100%） and abundant （11%-40%） type of vesicular intensity were observed. Arbuscular colonization was observed in three plants. The highest was in A. mangium （72%） and the lowest was in S. macrophylla （17%）. Arbuscular intensity was recorded as poor （12%-44%）, moderate （22%-100%） and abundant （4%-47%）. The highest AM fungal spore population was in A. auriculiformis （714） and the lowest was in D. sissoo （102）. Five AM fungal genera were recorded. Glomus was found to be dominant. A few spores remained unidentified. Significant correlation was observed between percent coloniza- tion and spore population. The results of the present study indicate the occurrence of AM fungi and the mycotrophism of the plants of Madhupur forest area and the applicability of AM technology in the forest management of Madhupur forest.     

How do trees affect spatio-temporal heterogeneity of nutrient cycling in mediterranean annual grasslands?

? In this study we analyzed heterogeneity in nutrient cycling induced by trees in Mediterranean annual grasslands, comparing years of higher and lower than average precipitation and analyzing the effects of two different solar radiation scenarios.

? Organic matter and consequently upper soil N, K, Ca and Mg were significantly greater in those locations receiving the highest levels of solar radiation, and as expected from many other studies in the literature, there was an increase in all macronutrients (except P) as well as pH below the canopy.

? Contrary to what was expected, plant nutrient concentrations did not directly reflect those found in the soil, with the exception of K. The studied grassland responded to increased nutrient availability by enhancing growth and changing botanical composition rather than by increasing plant nutrient concentrations. Hence, the total amount of accumulated nutrients in the ecosystem was larger below the tree than outside it, although this is mainly a consequence of plant growth enhancement. The levels of Ca, Mg, and Na in plants decreased during the driest year, and the N content was mostly determined by the composition of the grass.

? Temporal nutrient variability, particularly within-years, explained most of the variability in plant nutrient concentration, while spatial variability induced by trees was determined to be of secondary importance. These results are significant for ecosystem nutrient modelling.

     

Assessing the oil degradation potential of endogenous micro‐organisms in tropical marine wetlands

As part of a larger study on the bioremediation of oil spills in tropical mangrove habitats, we conducted a series of flask experiments to test for the presence of hydrocarbon degrading microorganisms in representative wetland habitats. Also tested was the biodegradation of selected oils (Gippsland Crude, Arabian Light Crude and Bunker C), that are transported along the Australian coast. We also tested for potential inhibition of biodegradation by natural organics in the mangrove pore waters and evaluated the ability of an oxygen release compound (ORC) to stimulate biodegradative processes. Evaporation was a significant factor in removing the light alkane and aromatic hydrocarbons from air and nitrogen sparged flasks. Evaporation removed 27% of the Gippsland, 37%of the Arabian, and 10% of the Bunker oils. Oxygen was necessary to support biodegradation as expected. The microorganisms were capable of biodegrading the nonvolatile saturate fraction of each oil. Degradation removed another 14 of the Gippsland, 30 of the Arabian, and 22 of the Bunker C oils. Normalisation of the individual aromatic hydrocarbon classes to internal triterpane biomarkers indicated some degradation of aromatics in the Arabian Light and Bunker C oils. Although alkane degradation rates were comparable in the three oils, the Gippsland oil had a higher wax content and after 14 days incubation, still contained as much as 25 of the alkanes present in the original oil. Thus, degradation of its aromatic fraction may have been delayed. Based on these results we estimate that Arabian Light Crude oil would have a shorter residence time than the other oils in mangrove sediment. It has a higher content of light hydrocarbons, which are readily removed by both physical and microbial processes. The Bunker C would be expected to have the longest residence time in mangrove sediment, because it contains a larger percentage of higher molecular weight, unresolved components. Comparison of the efficiency of inoculates from three tropical intertidal habitats (Avicennia and Rhizophora mangroves, plus salt marsh sediments) indicated the presence of hydrocarbon degrading microorganisms in all three habitats. There was no known history of oil contamination in the soil source area. There was no inhibition of degradation due to addition of mangrove pore waters. The ORC did not facilitate degradation in closed laboratory experiments. These results were used to formulate a bioremediation strategy to treat oiled sediments in mangrove forests in Queensland Australia, which was based on forced aeration and nutrient addition.Evaporation was a significant factor in removing the light alkane and aromatic hydrocarbons from air and nitrogen sparged flasks. Evaporation removed 27% of the Gippsland, 37% of the Arabian, and 10% of the Bunker oils. Oxygen was necessary to support biodegradation as expected. The micro-organisms were capable of biodegrading the non-volatile saturate fraction of each oil. Degradation removed another 14% of the Gippsland, 30% of the Arabian, and 22% of the Bunker C oils. Normalisation of the individual aromatic hydrocarbon classes to internal triterpane biomarkers indicated some degradation of aromatics in the Arabian Light and Bunker C oils. Although alkane degradation rates were comparable in the three oils, the Gippsland oil had a higher wax content and after 14 days incubation, still contained as much as 25% of the alkanes present in the original oil. Thus, degradation of its aromatic fraction may have been delayed. Based on these results we estimate that Arabian Light Crude oil would have a shorter residence time than the other oils in mangrove sediment. It has a higher content of light hydrocarbons, which are readily removed by both physical and microbial processes. The Bunker C would be expected to have the longest residence time in mangrove sediment, because it contains a larger percentage of higher molecular weight, unresolved components. Comparison of the efficiency of inoculates from three tropical intertidal habitats (Avicennia and Rhizophora mangroves, plus salt marsh sediments) indicated the presence of hydrocarbon degrading micro-organisms in all three habitats. There was no known history of oil contamination in the soil source area. There was no inhibition of degradation due to addition of mangrove pore waters. The ORC did not facilitate degradation in closed laboratory experiments.These results were used to formulate a bioremediation strategy to treat oiled sediments in mangrove forests in Queensland Australia, which was based on forced aeration and nutrient addition.     

Do tannins in leaves of trees and shrubs from African and Himalayan regions differ in level and activity?

Mature leaves of trees and shrubs from sub-humid tropical regions of Benin (Acioa barteri, Cassia sieberiana, Dialium guineense, Dichrostachys cinerea, Guiera senegalensis, Milletia thonningii, Piliostigma reticulatum) and arid and semiarid regions of Zimbabwe and Niger (Acacia holosericea, A. nilotica, Dichrostachys cinerea, Securidaca longepedunculata, Parinari cuvetelio, Ziziphus mucronata) in Africa, and from sub-tropical region in foot-hills of North-West Humid Himalayan range (Albizia stipulata, Bauhenia variegata, Cedrela toona, Celtis australis, Dendrocalamus hamiltonii, Grewia optiva, Leucocephala leucocephala, Morus alba, Papulus ciliata, Quercus incana, Q. semecarpifolia, Q. glauca, Q. serrata, Q. ilex, Robinia pseudoacacia, Salix tetrasperma) were analysed for crude protein, total phenols (TP), protein precipitation capacity (PPC) and operational activity of tannins (values are as mean ± SE). There was no significant difference in the crude protein values of forages obtained from the Himalayan and African region (15.2 ± 1.16 and 14.1 ± 1.19%, respectively), however the levels of TP and biological value of tannins as PPC were significantly higher for the African forages (TP 15.7 ± 4.27 vs 6.0 ± 1.0%; PPC 327.2 ± 113.6 vs 56 ± 15.9 mg bovine serum albumin precipitated/g). The operational activity of tannins expressed as mg protein precipitated per unit of phenols was also significantly higher in forages from the African regions (1.97 ± 0.47 vs 0.66 ± 0.17). For a small set of leaves from arid and semiarid zones of Middle East (Syria, A. cyanophylla; Israel, A. saligna) and India (Eugenia jambolana, Eucalyptus punctata, Prosopis cineraria and Shorea robusta) TP, PPC and tannin activity were closer to those for the African forages.This revised version was published online in November 2005 with corrections to the Cover Date.     

Relationship between the stoichiometric characteristics and leaf functional traits of Castanopsis hystrix in different ages

Both the stoichiometric characteristics and leaf functional traits can reflect the adaptability of plants to changes in the external living environment. In particular, for varying aged forest plants, the study of stoichiometric characteristics and leaf functional traits can reflect the plant’s life history strategy and its resource investment and allocation methods. In this paper, the 1.5-year-old, 5-year-old, 15-year-old and 20-year-old Casta -nopsis hystrix were selected as the research objects to investigate the trends of stoichiometry and leaf functional traits, and their synergistic changes were verified. The results showed that with the increase of age, the stability of C. hystrix stoichiometry gradually increased, and the functional traits also tended to invest in security. However, there was no synergistic change between the two, which might be attributed to the different sensitivity of the C. hystrix leaf to the environment at the life history level of 1.5-year-old to 20-year-old.     

Is elevation of carbon dioxide concentration beneficial to seedling photosynthesis in the understory of tropical rain forests?

Cuttings of the southeast Asian tropical rain forest tree species, Pongamia pinnata (L.) Pierre were raised in growth chambers providing a photosynthetic photon flux density (PPFD) of 60 micromol m(-2) s(-1) with either a low or a high red:far-red light ratio (LR and HR, repectively). The chambers were supplied with air containing CO(2) at a concentration of either 400 (LR4 and HR4, respectively) or 800 micromol mol(-1) (HR8 and LR8, respectively). After 4 months, leaf morphology and photosynthetic characteristics were determined. Relative to HR4, the LR4 treatment increased leaf area and total chlorophyll concentration (Chl) by 24 and 25%, respectively, but reduced leaf mass per unit area (LMA) by 19%. Elevated [CO(2)] significantly increased leaf area and LMA but did not affect Chl of LR or HR plants. Leaf nitrogen concentration was unaffected by the red:far-red light ratio but decreased significantly in seedlings in the elevated [CO(2)] treatment. Photosynthesis measured in situ under the growth conditions of ambient light and [CO(2)] (A(amb)) was 30% lower on an area basis and 14% lower on a mass basis in LR4 plants than in HR4 plants. Elevated [CO(2)] reduced the activity of ribulose-1,5-bisphosphate carboxylase/oxygenase and thus decreased light-saturated photosynthetic rate in both HR and LR plants. Elevated [CO(2)] increased mean leaf area and decreased respiration rates in both LR and HR plants. The LR8 plants had significantly higher A(amb) than LR4 plants, but similar A(amb) to HR8 plants.     

Incorporation and remobilization of ¹³C within the fine-root systems of individual Abies alba trees in a temperate coniferous stand

Forest ecosystems have a large carbon (C) storage capacity, which depends on their productivity and the residence time of C. Therefore, the time interval between C assimilation and its return to the atmosphere is an important parameter for determining C storage. Especially fine roots (≤2 mm in diameter) undergo constant replacement and provide a large biomass input to the soil. In this study, we aimed to determine the residence time of C in living fine roots and the decomposition rates of dead fine roots. Therefore, we pulse-labelled nine 20-year-old individual silver fir trees (Abies alba Miller; ～70 cm tall) with 13CO? in situ to trace the assimilated C over time into the fine-root systems. Whole trees were harvested at different time points after labelling in autumn, biomass was determined and cellulose and starch of fine roots were extracted. Moreover, soil cores were taken and ingrowth cores installed, in which fine roots were genetically identified, to assess incorporation and remobilization of 13C in the fine roots of silver fir trees; litterbags were used to determine fine-root decomposition rates. The 13C label was incorporated in the fine-root system as cellulose within 3 days, with highest values after 30 days, before reaching background levels after 1 year. The highest δ13C values were found in starch throughout the experiment. 13C recovery and carbon mean residence times did not differ significantly among fine-root diameter classes, indicating size-independent C turnover times in fine roots of A. alba trees of ～219 days. Furthermore, carbon was remobilized from starch into newly grown fine roots in the next spring after our autumn labelling. One year after installation, litterbags with fine roots revealed a decrease of biomass of ～40% with relative 13C content in fine-root bulk biomass and cellulose of ～50%, indicating a faster loss of 13C-labelled compounds compared with bulk biomass. Our results also suggest that genetic analysis of fine-root fragments found in soil and ingrowth cores is advisable when working in mixed forest stands with trees of similar fine-root morphology. Only then can one avoid dilution of the labelling signal by mistake, due to analysis of non-labelled non-target species roots.     

Effects of Culture Media and Light Intensity on in vitro Growth of Oncidium under CO2 Enrichment Condition

The effects of culture media and light intensity on in vitro growth of Oncidium ‘Aloha Iwanga‘ were investigated under CO2 enrichment condition. Height, fresh and dry weight of the Oncidium seedlings were measured, and the leaf number per plant, shoot number per plant, leaf width and leaf chlorophyll content were also investigated. The results were as follows: 1) The seedling height, fresh and dry weight, leaf number per plant, leaf width and leaf chlorophyll content of the shoots growing on MS complete culture medium were higher than those on 1/2MS, VW and 1/2VW media. The root number per plant and ratio of dry matter of the seedlings cultured on 1/2MS and 1/2VW media were higher than those on MS and VW; 2) The seedling height, flesh weight, dry weight, dry matter ratio and leaf chlorophyll content, leaf length, leaf width, root length, leaf number per plant, root number per plant of seedlings of Oncidium growing under 4 500 lx and 1 700 lx were higher than those under 750 lx. However, there was no significant difference in those growth parameters mentioned above while dealing with 4 500 lx and 1 700 lx except for the seedling height. Nevertheless, the leaf color of plants under 4 500 lx was lighter and the leaves of the lower parts became yellowish in comparison with those growing under 1 700 lx.     

Can methyl jasmonate treatment of conifer seedlings be used as a tool to stop height growth in nursery forest trees?

A plant's induced defense system can be triggered by the application of the plant hormone methyl jasmonate (MeJA), and recent research suggest that MeJA treatment may become a tool for protection of conifer seedlings against insect herbivory (e.g. by the pine weevil Hylobius abietis). A side-effect of MeJA application is temporarily reduced height growth. This has generally been considered as negative, but in forest tree nurseries this could instead be beneficial since it is commonly desired to stop the growth of nursery seedlings in late summer. Artificially longer dark periods (long nights/short days) are widely used in high-latitude nurseries to terminate height growth and induce freezing tolerance. However, long night treatment requires specialized nursery equipment and are labor intensive. Therefore alternatives are sought after. We compared long-night and MeJA treatments by following the growth of Norway spruce (Picea abies) seedlings throughout one season. The regulatory effect of MeJA on height growth was similar if not even better than that of long nights, i.e. it was terminated faster. However, MeJA treatment also reduced root growth and delayed the development of freezing tolerance. MeJA may therefore not replace long-night treatments, but it could facilitate a more flexible application of long nights by gaining a longer time interval during which this treatment can be used without risking the seedlings growing too large.

     

Multiple disturbance patterns and population structure of a tropical tree species,Afzelia africana (Leguminosae–Caesalpinioideae), in two contrasting bioclimatic zones of the Republic of Benin

Understanding how multiple disturbances affect species population structure is crucial for designing a better conservation strategy of threatened species. In this paper, we assessed the disturbance patterns and evaluated their effects on the population structure of Afzelia africana, in two different bioclimatic zones of the Republic of Benin. The main disturbances in the studied area included branch pruning and debarking. Individuals of medium size (20–40 cm) were mostly pruned and debarked. The percentages of pruning and debarking were similar at population level across the two studied bioclimatic zones (t = ?0.04, p = 0.96; t = 0.73, p = 0.48). Examining this at individual level, pruning was similar but debarking was higher in the Sudanian zone (12.14 ± 0.93%) than in the Sudano-Guinean zone (7.44 ± 0.88) (W = 40859, p < 0.001). Population structure was bell-shaped in the Sudanian zone regardless of the disturbance level. In contrast, in the Sudano-Guinean zone, mildly disturbed populations showed an inverse J-shaped structure, whereas those highly disturbed were bell-shaped. This underlined the climatic (dryness) and disturbance effects on the establishment and recruitment of small trees into the next life stage in tropical savanna ecosystems. Good regeneration pattern and the largest individuals were found within the protected areas, demonstrating the prominent role of protected areas for the species conservation. Therefore, we suggested that conservation efforts should be extended to populations outside the protected areas. Forestry department should establish firebreaks networks to protect small individuals and facilitate their recruitment, as well as the regulation and enforcement should be improved on the sustainable use of the species.     

Is the ranking of poplar genotypes for leaf carbon isotope discrimination stable across sites and years in two different full-sib families?

Introduction   

Because of its vigorous growth, poplar can play an important role for sustainable production of woody biomass to cover renewable energy needs. Hence, the selection of suitable genotypes has to be based on relevant traits, among which intrinsic water use efficiency (W _i, estimated through leaf carbon isotope discrimination, Δ) may be a key trait. Besides a large genetic variation in Δ among the frequently planted poplar hybrids, the use of Δ in deployment or breeding programmes requires insights in the robustness of the genotype ranking for Δ across environments and years.     

Changes in the biochemical composition and enzyme activity during dormancy release of Cyclocarya paliurus seeds

Cyclocarya paliurus is only propagated from seeds which have pronounced dormancy. Overcoming seed dormancy is an important component of efficient and cost-effective seedling production of Cyclocarya paliurus. Changes in biochemical composi-tion and enzyme activity were investigated during dormancy release. The activities of all the studied enzymes in the stratified seeds increased significantly, compared to those in the control samples. Of the enzymes examined, the activities of protease increased the most (413.8%), followed by peroxidase (278.7%), lipase (161.0%), glucose-6-phosphate dehydrognase (149.1%) and amylase (60.6%) after 8 months of stratification. Crude fat and protein constituted the bulk of the storage reserves in mature seeds of C. pali-urus. Compared with the seeds before stratification, about 45% of the starch, 46% of the protein and 11% of the crude fat were de-pleted during dormancy release of C. paliurus seeds, while the soluble sugar content was enhanced by 101.5% in the germinating seeds. Correlation analysis showed, during dormancy release of C. paliurus seeds, a close positive relationship between POD and G6PDH activity as well as soluble sugar content and amylase activity, while there was a significant negative relationship between storage substances and their related enzyme activities.     

Short-day treatment during the growing period limits shoot growth and increases frost hardiness of hybrid aspen plants in the nursery

In Finland, under nursery conditions hybrid aspen may continue their shoot growth until early September. Thus, frost hardening is usually delayed. To solve this problem, we used a three-week period of short-day (SD) treatment between late July and mid-August. During autumn after frost exposure, frost hardiness (FH) was assessed three times with a stem-browning test. The re-sults showed that after SD treatment shoot growth ceased and FH increased when compared to untreated hybrid aspen. Furthermore, the height of SD-treated hybrid aspen varied much less than that of the control plants. We conclude that SD treatment in the nursery during the growing period can be used as a supplementary method for producing well-hardened and uniform hybrid aspen plants.     

Model estimates of net primary productivity,evapotranspiration, and water use efficiency in the terrestrial ecosystems of the southern United States during 1895–2007

The effects of global change on ecosystem productivity and water resources in the southern United States (SUS), a traditionally ‘water-rich’ region and the ‘timber basket’ of the country, are not well quantified. We carried out several simulation experiments to quantify ecosystem net primary productivity (NPP), evapotranspiration (ET) and water use efficiency (WUE) (i.e., NPP/ET) in the SUS by employing an integrated process-based ecosystem model (Dynamic Land Ecosystem Model, DLEM). The results indicated that the average ET in the SUS was 710 mm during 1895–2007. As a whole, the annual ET increased and decreased slightly during the first and second half of the study period, respectively. The mean regional total NPP was 1.18 Pg C/yr (525.2 g C/m²/yr) during 1895–2007. NPP increased consistently from 1895 to 2007 with a rate of 2.5 Tg C/yr or 1.10 g C/m²/yr, representing a 27% increase. The average WUE was about 0.71 g C/kg H₂O and increased about 25% from 1895 to 2007. The rather stable ET might explain the resulting increase in WUE. The average WUE of different biomes followed an order of: forest (0.93 g C/kg H₂O) > wetland (0.75 g C/kg H₂O) > grassland (0.58 g C/kg H₂O) > cropland (0.54 g C/kg H₂O) > shrubland (0.45 g C/kg H₂O). WUE of cropland increased the fastest (by 30%), followed by shrubland (17%) and grassland (9%), while WUE of forest and wetland changed little from the period of 1895–1950 to the period of 1951–2007. NPP, ET and WUE showed substantial inter-annual and spatial variability, which was induced by the non-uniform distribution patterns and change rates of environmental factors across the SUS. We concluded that an accurate projection of the regional impact of climate change on carbon and water resources must consider the spatial variability of ecosystem water use efficiency across biomes as well as the interactions among all stresses, especially land-use and land-cover change and climate.