Spatial and temporal changes in shorebird habitats under different land use scenarios along the Yellow and Bohai Sea coasts in China.

The effect of coastal wetland loss on shorebird habitat in recent years has been widely reported in previous studies. Various coastal wetland conservation and restoration measures have been implemented or will soon be implemented in China. The extent to which these measures will affect the area and structure of coastal wetland habitat in the future remains unclear. Here, we predicted changes in habitat area and structure for 39 common shorebird species along the coasts of the Yellow and Bohai Seas using a cellular automata-Markov (CA-Markov) land use scenario model and a maximum entropy species distribution model, along with terrain factors (slope, aspect, and digital evaluation model) and climate factors (temperature and precipitation) from the Data Centre for Resources and Environmental Sciences at the Chinese Academy of Sciences, land cover maps interpreted using the human-computer interactive method, and citizen science data of shorebird occurrences derived from eBird, Global Biodiversity Information Facility, and Bird Report. We found that shorebird habitat was most abundant along the coasts of Bohai Bay, Laizhou Bay, and Yancheng. The area of habitat decreased and became increasingly fragmented between 2000 and 2020 for more than half of the 39 species. Under the future business-as-usual scenario, the area of shorebird habitat decreased from 2020 to 2050, and the remaining habitat became increasingly fragmented. Under the ecological protection (EP) scenario, habitat loss was mitigated, and habitat connectivity was improved. The area of habitat was lower in 2050 under the EP scenario than in 2000 for most species, especially threatened species, suggesting that the area of habitat will not return to year-2000 levels under the EP scenario. These results emphasize the need to protect remaining shorebird habitats and implement ecological conservation measures to ensure the long-term preservation of coastal wetlands.

Identification and scoring of conservation gaps in wetlands of China's coastal provinces: Implications for extending protected areas.

Wetlands in China's coastal provinces are strategically positioned along migratory flyways for waterbirds, serving as essential habitats and stopover sites due to the expansive land area and abundant wetland resources they offer. This study aimed to introduce a simplified index system to enable rapid assessment and prioritization of unprotected areas for wetlands in China's coastal provinces. A spatial analysis was conducted, combining wetland distribution and existing protected areas data and spatial extent of wetlands extracted by remote sensing data. Results indicate substantial gaps in coverage, covering an area of 108.33 × 104 ha, with 76% being natural wetlands. Over half of these gaps are identified as high-value wetlands with significant ecological functions. The uneven distribution of unprotected wetlands reflects a tension between economic development and wetland conservation. Our findings support the expansion of the existing coastal wetland protected areas' coverage, as well as protecting critical habitats in conservation gaps, and establishing of a network-based waterbird protection system. This research contributes to informed decision-making and policy in wetlands' conservation planning.

Evaluation of historical and future coastal wetland change in the Yellow and Bohai Seas using satellite images and a land use model.

Predicting the future distribution of coastal wetlands and characterizing changes in the area of wetlands between historical and future periods are important for the formulation of wetland conservation and management plans. Here, we used a cellular automata-Markov model and satellite images to simulate the future distribution of coastal wetlands under the business-as-usual scenario (BAU) and ecological protection scenario (EP) along the Yellow and Bohai Seas in China; we also explored historical (from 1990 to 2020) and future (from 2020 to 2050) changes in wetlands and the factors driving these changes. We found that the area of tidal flats gradually decreased because of increases in the area of saltpans, and the aquaculture area increased because of land reclamation and the invasion of Spartina alterniflora; most of the tidal flat area was fragmented into multiple small patches. If the current rate of degradation continues (BAU), the area of tidal flats will decrease by 21.25%, and the area of saltpans and aquaculture will increase by 13.83% and 21.25%, respectively. By contrast, under EP, the area of tidal flats will increase by 13.81%, and this increase will mainly stem from the conversion of areas with S. alterniflora (174.49 km2, 33.22%) to aquaculture areas (155.17 km2, 29.54%). Clear differences between historical and future periods were observed among Liaohe Estuary, Bohai Bay, Laizhou Bay, and the Yancheng-Nantong coasts. Land reclamation is the main factor inducing changes in the area of tidal flats, saltpans, and aquaculture in Liaohe Estuary, Bohai Bay, and Laizhou Bay. Land reclamation and the S. alterniflora invasion both affect the distribution of wetlands along the Yancheng-Nantong coasts.

Effects of water depth on the biomass of two dominant submerged macrophyte species in floodplain lakes during flood and dry seasons.

Floodplain lakes share characteristics of both deep and shallow lakes throughout any given year. Seasonal fluctuations in their water depth drive changes in nutrients and total primary productivity, which directly and indirectly affect submerged macrophyte biomass. To investigate how water depth and environmental variables affect submerged macrophyte biomass, we surveyed six sub-lakes in the Poyang Lake floodplain, China, during the flood and dry seasons of 2021. Dominant submerged macrophytes include Vallisneria spinulosa and Hydrilla verticillata. The effect of water depth on the biomass of these macrophytes varied between the flood and dry seasons. In the flood season, there was a direct effect of water depth on biomass, while in the dry season only an indirect effect was observed. During the flood season, the direct effect of water depth on the biomass of V. spinulosa was less than the indirect effect, with water depth primarily affecting the total nitrogen, total phosphorus and water column transparency. Water depth directly, positively affected H. verticillata biomass, with this effect being greater than the indirect effect by affecting the carbon, nitrogen and phosphorus content in the water column and sediment. During the dry season, water depth affected H. verticillata biomass indirectly through sediment carbon and nitrogen content, while for V. spinulosa, the effect on biomass was indirect through carbon content of the sediment and water column. The main environmental variables affecting submerged macrophyte biomass in the Poyang Lake floodplain during the flood and dry seasons, and the mechanisms through which water depth affects dominant submerged macrophyte biomass, are identified. An understanding of these variables and mechanisms will enable improved management and restoration of wetland.

An integrated model for prediction of hydrologic anomalies for habitat suitability of overwintering geese in a large floodplain wetland, China.

Climate anomalies and increasing human activities cause a high frequency of extreme hydrological events in wetlands, which has put waterbirds under greater survival pressure than ever. Therefore, it is crucial to predict the impact of this phenomenon on the habitat suitability of waterbirds. This study investigated the response of the goose distribution probability to hydrological variations using the flood duration index (FD), enhanced vegetation index (EVI), and waterbirds GPS tracking data in Poyang Lake. An overwintering geese habitat suitability index (HSI) is built based on the FD, EVI, and threat index and verifies the accuracy of the model simulation. Then, the effects of drought and flood on the goose habitat especially sub-lakes with different connectivity were analyzed. The findings reveal that in dry and flood years, geese will broaden their range of feeding vegetation (more fresh or mature vegetation) in response to environmental deterioration. Both drought and flood can lead to a decline in the HSI, especially flood. Connected sub-lakes are more vulnerable to hydrological anomalies than controlled sub-lakes. This research establishes a scientific foundation for floodplain wetland hydrology management and waterbird conservation.

Investigating the potential impact of ecological restoration strategies on people-landscape interactions through cultural ecosystem services: A case study of Xilin Gol, China.

Although cultural ecosystem services (CES) are greatly valued by diverse stakeholders, the full range of CES provided by a landscape is notoriously difficult to estimate. The resulting lack of objective norms for CES may lead to the loss of the multiple non-material factors that contribute to how a landscape is valued and experienced. This is especially true under ecological restoration, which could sharply change how people experience landscapes. Therefore, our aim in this study was to identify and analyze the CES that arise from people's interaction with their landscape, focusing specifically on the influences of different ecological restoration strategies. We carried out semi-structured interviews with the residents of villages in the Xilin Gol League, Inner Mongolia, China. Regarding the implementation of ecological restoration measures, the people living in typical pastoral zones would be most affected by these measures because their main livelihood (animal husbandry) depends strongly on grasslands. Our results demonstrated that human perception of the CES provided by landscapes is affected not only by the factors related to an individual's cultural worldview (e.g., ethnicity, age, education) but also by the utility of landscape features, which are reflected in the individual's landscape dependence (occupation). Our research provides a cultural perspective for aspects of local well-being in addition to ecological and economic targets. Understanding these other aspects is critical for implementing sustainable ecological restoration.

Land-use-mediated inconsistency of changes in the provision and delivery of soil erosion control services at the watershed scale.

Soil erosion control services (SECSs) are the benefits delivered to people derived from preventing the negative impacts of soil erosion, such as avoiding the loss in soil productivity and preventing the damage to infrastructures such as dams and roads. SECS is derived from the functions of the ecosystems and is delivered to people through physical processes and social activities. The land-use change (LUC) reshapes the SECSs supply capacity, the SECS flow over the landscape, and the related benefit people received. Numerous studies have revealed how LUC shapes the SECSs supply capacity. However, the SECSs flow to local communities, and the LUC-derived SECS flow dynamics remain unclear. This study quantified the SECSs delivered to local communities following a land-use-specific cascade mechanism and using the WATEM/SEDEM framework. The effects of on-site soil erosion and sediment delivery over the watershed were combined. The cultivated lands were considered as the conveyers of SECSs. The study revealed the inconsistency of temporal change in SECS provision and the actual SECSs delivery to local communities. The results illustrated the increased capacity for soil erosion prevention and sediment flow reduction and a consequent increase in SECS supply capacity. However, the total amount of actual SECSs delivered to the local communities was declined due to the land-use change featured in reduced cropland area. The results imply that changes in SECS provision capacity cannot directly indicate the changes in SECS delivery to local communities. Though the modeled SECSs did not cover all SECSs in this region, this study highlights the effectiveness of the land-use-specific cascade framework in describing the delivery of SECSs and the importance of addressing the delivery processes of ecosystem services from ecosystem to people.

Assessing landscape fragmentation in a desert-oasis region of Northwest China: patterns, driving forces, and policy implications for future land consolidation.

Landscape fragmentation is considered a serious threat to eco-environmental integrity and socioeconomic development. Although many studies have focused on landscape fragmentation resulting from agricultural production and urbanization, landscape fragmentation from the aspects of patterns, driving forces, and the policy perspective of ecosystems has rarely been investigated. Oases, as a unique landscape, face severe fragmentation in arid and semiarid regions. This study applied a combination of approaches, including remote sensing image interpretations, landscape fragmentation metrics, and community surveys, to analyze patterns and their driving forces, as well as the policy implications for future land consolidation, in the Hotan oasis of Northwest China from the space and time perspectives. Results show that the frequent occurrence of summer flood events changes the patch number, density, size, and splitting degree of oasis-desert ecotone vegetation. The socioeconomic factors including total population and irrigation area are more important driving forces on oasis landscape fragmentation, compared with natural factors such as temperature and precipitation. Rural expansion, road and canal system developments caused by population growth, and the rising number of households increase oasis landscape fragmentation. Rapid economic development, such as agricultural expansion and urbanization, has imposed the intensification of landscape fragmentation. Fragmentation reaches peak when agricultural development makes up 40-50% of study area. Rural residential reconstruction and farmland transfer policies facilitate the intensive utilization of land toward oasis fragmentation solutions, but many factors, such as landholders' household characteristics and living conditions, are partly responsible for the challenges in land consolidation. This study also demonstrates that intense human activities pose a great threat for land consolidation and sustainable development of oasis landscape.

An evaluating system for wetland ecological risk: Case study in coastal mainland China.

Coastal wetland degradation and fragmentation contribute to habitat and biodiversity loss. We construct wetland ecological risk assessment framework to evaluate the risk posed to 35 coastal wetland national nature reserves (NNRs) in China for the years 2000 and 2020. Our wetland ecological risk index (WRI) is based on an external hazard sub-index (EHI) and an internal vulnerability sub-index. Most NNRs have low EHI values in both 2000 and 2020. Ratios of change in EHI range from -22.76% to 52.15% (a negative value indicates a decrease, a positive value an increase), and the EHI for 20 of 35 NNRs (57.1%) decreases over time. Variation in the internal vulnerability index ranges -44.78% to 88.97%, and increases at 18 NNRs (51.4%) over time. WRI variation ranges between -48.13% and 82.91%, and increases at 19 NNRs (54.3%). Most NNRs are ranked as being at low, medium risk in both 2000 and 2020. Notably, the number of high-risk NNRs increases from 3 to 10 (for which WRI values also increase). Expansion of built-up land, cropland occupation (in 2020), road disturbance, and water quality are all significantly associated WRI. Intensified management of the 10 NNRs ranked at high risk is necessary to prevent further deterioration.

Hydrologic-induced concentrated soil nutrients and improved plant growth increased carbon storage in a floodplain wetland over wet-dry alternating zones.

Hydrological gradient variations in wetlands have a vital impact on wetland carbon storage. However, the mechanisms by which hydrological gradient variations affect biomass and carbon storage by regulating the soil nutrient contents and plant diversity remain unclear. This study attempted to explore these influencing mechanisms by studying the relationships between hydrological gradient variations and carbon storage in wetlands. The results showed that the average nutrient content, plant biomass and soil carbon content values in the high-frequency wet-dry alternating zones (HFWA, zones where the frequency of water level occurs between -25 cm and 25 cm greater than 0.5) were 1.4 times, 2.3 times and 0.43 higher, respectively, than those in the low-frequency wet-dry alternating zones (LFWA, zones where the frequency of water level occurs between -25 cm and 25 cm less than 0.3). These results indicated that the HFWA zones had higher soil nutrients, higher plant dominance, higher biomass and higher soil carbon contents than the LFWA zones. The structural equation model revealed a significant positive correlation between wet-dry alternations and the soil nutrient-plant biomass-soil carbon relation in wetlands. Moreover, there was also a significant positive correlation between wet-dry alternations and the plant dominance-plant biomass-soil carbon relation in wetlands. This implied that the concentrated effect of HFWA on soil nutrients promotes plant growth, enhances plant dominance, promotes plant productivity, and enhances the capacities of plants to input carbon to the soil, thereby increasing the soil carbon content. This study closely linked wetland hydrological gradients, plant biodiversity and wetland carbon sequestration and profoundly revealed the mechanisms by which hydrological gradients in wetlands regulate the concentrations of nutrient elements, thereby affecting vegetation growth and carbon sequestration; these results could provide a new cognitive basis for understanding the coupling of carbon and water.

Integrating ecosystem services modeling into effectiveness assessment of national protected areas in a typical arid region in China.

Protected areas (PAs) are essential for biodiversity conservation and for the delivery of ecosystem services (ESs). However, little is known about their effectiveness in providing ESs and contribution to species richness, especially in arid regions. Effectiveness evaluation is fundamental to understanding the extent of management enhancement required to fulfill conservation targets. In this study, we analyzed the supply of six ESs (water yield, nutrient retention, soil retention, sand fixation, carbon storage, and biodiversity richness) by landscapes in China's arid region of Xinjiang Uygur Autonomous Region (hereafter Xinjiang). The aim was to identify distribution of ESs hotspots and the extent of hotspots located within or outside national PAs. The results showed significant spatial heterogeneity and coverage differences in six types of ESs hotspots. Hotspots coverage of six ESs on average accounted for 10.45 % of the total area, distributed mainly in mountains and oases covered by vegetation and wetlands. Among these ESs hotspots, over 50 % fell within PAs. This suggested that although PAs delivered moderately well outcomes in preserving ESs and biodiversity in Xinjiang, conservation gaps needed to be addressed. Our study also revealed substantial differences in ESs supplied by different PAs, and serious deficiency existed in some PAs in protecting either biodiversity or key ESs outlined in their conservation objectives. Our study illustrated the priority areas for future conservation expansion and stressed the urgent shift toward broadening the goals of PAs from a dominant focus to ones that encompass multiple ESs for human well-being.

Increased association between climate change and vegetation index variation promotes the coupling of dominant factors and vegetation growth.

Vegetation productivity dynamics are closely related to climate change, and water availability determines vegetation growth in water-limited ecosystems. Nevertheless, how changes in the interactions between climatic factors and vegetation activity variation regulate the relationship between their trends remains unclear. The Normalized Difference Vegetation Index (NDVI) is an effective proxy of vegetation growth. First, we investigated the NDVI trends, and the results revealed a vegetation activity with weaker greening and greater spatial heterogeneity after an obvious land-cover breakpoint in 1999 compared with that before 1999 in northwest China. Notably, the Loess Plateau greatly led the greenness trends, but the Tibet Plateau showed mean browning after 1999, which implied that the coupling of climate change and vegetation trends varied with spatio-temporal changes. Subsequently, using the Geographical Detector Method (GDM), we quantified and compared the association between climate change and the interannual variability of NDVI in the two stages. Vegetation productivity variation is more closely related to changes in climatic factors after 1999 compared with that before 1999. Precipitation (PPT) and vapor pressure deficit (VPD) are the primary constraints to vegetation growth in both stages. Patterns in NDVI trend increases are consistent with those of increased PPT and decreased VPD and vice versa after 1999. However, the same patterns were not observed before 1999 because of the weak association between climate change and NDVI variation. This implicated a great significance of the association between climate change and changes in vegetation activity for the prediction of potential carbon sequestration due to the shift of dominant factors and their trends under future climate change.

Using citizen science data to inform the relative sensitivity of waterbirds to natural versus human-dominated landscapes in China.

Habitat loss is widely regarded as one of the most destructive factors threatening native biodiversity. Because migratory waterbirds include some of the most globally endangered species, information on their sensitivity to landscape would benefit their conservation. While citizen science data on waterbird species occurrence are subjected to various biases, their appropriate interpretation can provide information of benefit to species conservation. We apply a bootstrapping procedure to citizen science data to reduce sampling biases and report the relative sensitivity of waterbird species to natural versus human-dominated landscapes. Analyses are performed on 30,491 data records for 69 waterbird species referred to five functional groups observed in China between 2000 and 2018. Of these taxa, 30 species (43.5%) are significantly associated with natural landscapes, more so for cranes, geese, and ducks than for shorebirds and herons. The relationship between land association and the threat status of waterbirds is significant when the range size of species is considered as the mediator, and the higher the land association, the higher the threat status. Sensitive species significantly associated with natural landscapes are eight times more likely to be classified as National Protected Species (NPS) Classes I or II than less sensitive species significantly associated with human-dominated landscapes. We demonstrate the potential for citizen science data to assist in conservation planning in the context of landscape changes. Our methods might assist others to obtain information to help relieve species decline and extinction.

Assessing the influences of ecological restoration on perceptions of cultural ecosystem services by residents of agricultural landscapes of western China.

Landscape change caused by ecological restoration projects has both positive and negative influences on human livelihoods, yet surprisingly little research on the cultural consequences of ecological restoration in agricultural landscapes has taken place. Cultural consequences can be captured in the ecosystem services framework as cultural ecosystem services (CES). However, assessment and valuation of these services to support decision-making for this essential ecosystem is lacking. To help fill this gap, we assessed the opinions of Chinese rural communities about CES and the changes in their perception under the Grain for Green program (GFG), a nationwide program to relieve the pressure on ecosystems (soil erosion and land degradation) by converting cultivated land or barren land on steep slopes into grassland and forests. We used Guyuan City in China's Ningxia Hui Autonomous Region as a case study, using a workshop to identify the CES provided by the agricultural landscape, followed by semi-structured household interviews to quantify perceptions of these CES. We found that all eight CES types identified by the workshop were perceived by the rural communities. Reforestation changed their perceptions of CES directly due to land cover change and indirectly due to the resulting economic changes and migration of mostly young workers in search of better jobs. Cultivated land was perceived as more important than forest for CES provision. In addition, residential areas were perceived as providing significant CES because of local traditions that produce close and highly social neighborhood bonds in agricultural landscapes.

Challenges in coupling LTER with environmental assessments: An insight from potential and reality of the Chinese Ecological Research Network in servicing environment assessments.

Environmental assessments estimate, evaluate and predict the consequences of natural processes and human activities on the environment. Long-term ecosystem observation and research networks (LTERs) are potentially valuable infrastructure to support environmental assessments. However, very few environmental assessments have successfully incorporated them. In this study, we try to reveal the current status of coupling LTERs with environmental assessments and look at the challenges involved in improving this coupling through exploring the role that Chinese Ecological Research Network (CERN), the LTER of China, currently plays in regional environment assessments. A review of official protocols and standards, regional assessments and CERN researches related to ecosystems and environment shows that there is great potential for coupling CERN with environment assessments. However in practice, CERN does not currently play the expected role. Remote sensing and irregular inventory data are still the main data sources currently used in regional assessments. Several causes led to the present situation: (1) insufficient cross-site research and failure to scale up site-level variables to the regional scale; (2) data barriers resulting from incompatible protocols and low data usability due to lack of data assimilation and scaling; and (3) absence of indicators relevant to human activities in existing monitoring protocols. For these reasons, enhancing cross-site monitoring and research, data assimilation and scaling up are critical steps required to improve coupling of LTER with environmental assessments. Site-focused long-term monitoring should be combined with wide-scale ground surveys and remote sensing to establish an effective connection between different environmental monitoring platforms for regional assessments. It is also necessary to revise the current monitoring protocols to include human activities and their impacts on the ecosystem, or change the LTERs into Long-Term Socio-Ecological Research (LTSER) networks.

Effects of environmental variation on stable isotope abundances during typical seasonal floodplain dry season litter decomposition.

Unique hydrological characteristics and complex topography can create wide-ranging dry season environmental heterogeneity in response to groundwater level across China's Jiangxi Province Poyang Lake wetland. Soil traits are one of several fluctuating environmental variables. To determine the effects of soil variables on stable isotope (δ13C and δ15N) abundances during decomposition, we performed a field experiment using Carex cinerascens along a groundwater level gradient (GT-L: -25 to -50cm, GT-LM: -15 to -25cm, GT-MH: -5 to -15cm, GT-H: 5 to -5cm) in a shallow lake. Twelve soil properties-including total organic carbon (TOC), nitrogen (N), pH, moisture, bulk density, clay, silt, sand, peroxidase, cellulase, microbial biomass carbon (MBC), and microbial biomass nitrogen-were measured in surface soil samples to assess soil environmental conditions. Analyses were performed to determine the effects of soil traits and lignin degradation on changes in stable isotope abundances. This study revealed that stable isotope abundances were significantly lower at high groundwater levels than at low groundwater levels. Lignin degradation was associated with a decrease in both δ13C and δ15N abundances. These two stable isotopes were positively related with soil N and bulk density, but negatively with pH and microbial quotient (MBC/TOC). Variation partitioning analysis (VPA) showed that soil variables and lignin decay rates explained 80.1% of the δ13C variation and 42.8% of the δ15N variation. Soil chemical and biological variables exhibited significant interactions with lignin decay rates, indicating they may affect stable isotope abundances via complex mechanisms. Our results indicate that the change in stable isotope abundances during decomposition may be affected directly by soil variables or indirectly through lignin degradation. Our results provide useful insight for understanding the roles of litter decomposition and soil traits in changing environmental conditions of seasonal floodplain wetlands.

Wintering waterbirds in a large river floodplain: Hydrological connectivity is the key for reconciling development and conservation.

An alteration in the hydrological connectivity reduces the synergistic processes and interactions between rivers and their floodplains, and changes the distribution of waterbirds that rely on floodplains as foraging grounds. Recent river and wetland conservation and restoration efforts have been partially focused on reinstating the natural river-floodplain connectivity to ameliorate the ecological effects of regulation in river systems. However, in regions where human well-being is tightly linked with the cultivation of the floodplain (such as fisheries), management options are constrained and trade-offs among competing social, economic and ecological goals may be necessary for the wise use of wetlands. Poyang Lake in east central China includes numerous sub-lakes with different types of hydrological regulation; therefore, this lake may provide a useful context for exploring the likelihood of such trade-offs. In this study, we used multiyear simultaneous waterbird survey data together with habitat maps derived from satellite imagery for Poyang Lake to examine the variations in waterbird community structure and abundance within sub-lakes with different types of hydrological regulation. Using a Bayesian Markov chain Monte Carlo approach, we built generalized linear mixed models to explore the differences in wetland composition and waterbird abundance/diversity among three lake types (i.e. isolated, freely connected, and controlled) at community, guild and species levels. The results showed hydrological connectivity alteration clearly affects wintering waterbirds; in addition, the ecological benefits of a natural flow regime were most unambiguous at the community level. Nevertheless, little evidence exists to indicate that the lakes' ecological values as waterbird foraging grounds were compromised by partial regulation. That is, species richness and population size were comparable in naturally connected and controlled lakes. Our results suggest that, with carefully designed management plans, a delicate balance between waterbird conservation and development can be accomplished in large river floodplains.

Leaf-age effects on temperature responses of photosynthesis and respiration of an alpine oak, Quercus aquifolioides, in southwestern China.

Temperature responses and sensitivity of photosynthesis (A(n_)T) and respiration for leaves at different ages are crucial to modeling ecosystem carbon (C) cycles and productivity of evergreen forests. Understanding the mechanisms and processes of temperature sensitivity may further shed lights on temperature acclimation of photosynthesis and respiration with leaf aging. The current study examined temperature responses of photosynthesis and respiration of young leaves (YLs) (fully expanded in current growth season) and old leaves (OLs) (fully expanded in last growth season) of Quercus aquifolioides Rehder and E.H. Wilson in an alpine oak forest, southwestern China. Temperature responses of dark respiration (R(dark)), net assimilation (A(n)), maximal velocity of carboxylation (V(cmax)) and maximum rate of electron transport (J(max)) were significantly different between the two leaf ages. Those differences implied different temperature response parameters should be used for leaves of different ages in modeling vegetation productivity and ecosystem C cycles in Q. aquifolioides forests and other evergreen forests. We found that RuBP carboxylation determined the downward shift of A(n_)T in OLs, while RuBP regeneration and the balance between Rubisco carboxylation and RuBP regeneration made little contribution. Sensitivity of stomatal conductance to vapor pressure deficit changed in OLs and compensated part of the downward shift. We also found that OLs of Q. aquifolioides had lower An due to lower stomatal conductance, higher stomatal conductance limitation and deactivation of the biochemical processes. In addition, the balance between R(dark) and A(n) changed between OLs and YLs, which was represented by a higher R(dark)/A(n) ratio for OLs.

Major ecosystems in China: dynamics and challenges for sustainable management.

Ecosystems, though impacted by global environmental change, can also contribute to the adaptation and mitigation of such large scale changes. Therefore, sustainable ecosystem management is crucial in reaching a sustainable future for the biosphere. Based on the published literature and publicly accessible data, this paper discussed the status and trends of forest, grassland, and wetland ecosystems in China that play important roles in the ecological integrity and human welfare of the nation. Ecological degradation has been observed in these ecosystems at various levels and geographic locations. Biophysical (e.g., climate change) and socioeconomic factors (e.g., intensive human use) are the main reasons for ecosystem degradation with the latter factors serving as the dominant driving forces. The three broad categories of ecosystems in China have partially recovered from degradation thanks to large scale ecological restoration projects implemented in the last few decades. China, as the largest and most populated developing nation, still faces huge challenges regarding ecosystem management in a changing and globalizing world. To further improve ecosystem management in China, four recommendations were proposed, including: (1) advance ecosystem management towards an application-oriented, multidisciplinary science; (2) establish a well-functioning national ecological monitoring and data sharing mechanism; (3) develop impact and effectiveness assessment approaches for policies, plans, and ecological restoration projects; and (4) promote legal and institutional innovations to balance the intrinsic needs of ecological and socioeconomic systems. Any change in China's ecosystem management approach towards a more sustainable one will benefit the whole world. Therefore, international collaborations on ecological and environmental issues need to be expanded.