1 Ecological Processes and Functions of Natural Forests
With supported of the National Key Basic Research Program of China (973 program) of the MOST; the Key Program of the Chinese Academy of Sciences (CAS); the Pilot Technology Project of CAS; and the International Cooperation and Exchange Project of the National Natural Science Foundation of China, we have made great progress in studying mechanisms for sustaining biodiversity, ecological functions, theories and technologies of natural forest management, as well as refining the theoretical framework of boundary layer ecology and its application in global climate change research. More than 120 papers have published in such journals as the Journal of Ecology, Ecography, Oecologia, Oikos, PLoS ONE, Agricultural and Forest Meteorology, Journal of Geophysical Research, and Journal of Hydrology. The group has also published more than 10 monographs. In addition, this group has developed conservation technologies for natural forests and successfully applied them to a 710,000 ha of such forests. The group received the second prize of the National Science and Technology Progress Award in 2012; the second prize of the Liaoning Provincial Science and Technology Progress Award in 2009; the first prize of the Liangxi’s Forestry Science and Technology Award in 2009; and the third prize of the Jilin Provincial Science and Technology Progress Award in 2012. The group also received the Norbert Gerbier-MUMM International Award from the World Meteorological Organization for its research on boundary layer ecology in 2012.
Pattern, dynamics and maintenance mechanisms of biodiversity in the natural forests of Changbai Mountain
Since 2004, we have monitored 70 tree species, more than 70,000 individual trees, and 50,000 seedlings in a 25-ha broadleaf Korean pine mixed forest plot, as well as eight additional 1-ha forest plots at different successional stages along altitudinal gradients in the temperate forests of the Changbai Mountain in Northeast China. We focus on the pattern and dynamics of biodiversity and examine biodiversity maintenance mechanisms in these temperate forests. The following accomplishments have resulted from our work: 1) Research on biodiversity patterns revealed that most woody plants in temperate forests are aggregated and their aggregation intensity varied with abundance, shade tolerance and dispersal ability of species. About 30% of the species pairs showed significantly negative small-scale associations, clearly higher than the 6% commonly found in tropical forests, and species interaction strength increased with species abundance, supporting the “abundance-asymmetry hypothesis”; 2) Research on biodiversity dynamics revealed that annual and seasonal dynamics of seed rain depend on temperature and precipitation, and clarified key mechanisms and their relative importance in influencing tree survival in temperate forests. Tree diameter was found to be the most important factor, followed by biotic factors and then environmental factors; and 3) Research on biodiversity maintenance mechanisms showed that negative density dependence occurred at multiple life stages from seedling to adult in temperate forests, and revealed that both habitat heterogeneity and dispersal limitation contributed to species coexistence, with the latter more important.
Forest ecosystem services
We used old growth forests of the temperate biome as a reference to study the influence of human activities on the structure andfunction of forest ecosystems. We examined the mechanisms of regulating natural forest structure and how to optimize ecological functions of natural forests, as well as the importance of regeneration and recovery of key species at the stand and landscape scales. We also examined the mechanisms of carbon sequestration and found that old growth natural forests at Changbai Mountain can function as a carbon sink. We found that harvesting has a limited effect on total organic carbon in forest soil, while significantly altering the ratio of active to recalcitrant organic carbon and increasing soil organic carbon mineralization. Furthermore, we found that implementation of the Natural Forest Protection Program in Northeast China (1998–2008) has increased carbon storage within key public welfare forests, but has had no significant effect on soil carbon dynamics in general public welfare forests and commercial forests.
Theory and technology for sustainable naturalforest management
In light of forestry practices in China and the need for forest management in Northeast China, our group developed FORESTAR (V1.0), a forest management decisionsupport system. This system uses the technologies of spatial analysisand multi-source data fusion. It integrates theories of ecosystem management and landscape ecology with improvement in forest harvesting and regeneration technology at the stand scale, and incorporates concepts of forest biodiversityprotection andsustainable management at the landscape scale.
FORESTAR employs land managed by the Jilin ForestBureau as the modeling unit. It takes into account multiple forest management objectives, including the integrity of ecological functions, the conservation of biological diversity, the allocation of forest harvesting regimes, and the goal of forest economic development to derive spatially explicit management plans. The system can generate a variety of forest management scenarios for specific objectives. With the aid of FORESTAR, our group developed sustainable natural forest management plans that combine the social, economic, and ecological dimensions of forest management.
Boundary layer ecology and its applications in global climate change research
Our group has systematically studied the structure, function and kinetic laws of the canopy-atmosphere, soil-atmosphere and root-soil interfaces. We have also applied concepts of boundary layer ecology to the study of global climate change. We have established a carbon flux measurement system with high temporal and spatial resolutions above the forest canopy and taken the lead in research on carbon fluxes in forest ecosystems in China. We developed two novel correction methods for long-term CO2 flux measurements that were recognized as a ‘new important development in the eddy method’. Our findings revealed that the old-growth natural forests in the Changbai Mountain are functioning as a carbon sink. These conclusions supported the scientific hypothesis that primary forests can serve as a baseline reference in evaluating the carbon sequestration potential of all forest ecosystems. Using the OTC (open-top chamber) method, we conducted research on the adaptation of tree species to elevated CO2. This experiment has been carried out for more than 11 years following the planting of seedlings in large open-top chambers. Our group constructed a large scale in-situ facility for precipitation and nitrogen addition experiments. We also installed the first forest canopy crane in China, covering an area of 0.8 ha of the intact primary forest. This facility will be used to extrapolate plot measurements to regional scales.
2 Ecology and Management of Plantation Forests
Our group has been supported primarily by the following programs: the National Basic Research Program of China (973 Program), Key Programs of Chinese Academy of Sciences, the National Science Foundation for Distinguished Young Scholars, and the Strategic Priority Research Program of the Chinese Academy of Sciences. Under the support of these programs, our research has focused on degradation processes and the management of soil fertility in subtropical, arid and semi-arid plantation forests; management theories and technologies of farmland shelterbelt forests; and carbon cycles in plantation forests. We have made important progress on these topics and published 142 papers, including those in high-profile international journals such as Soil Biology and Biochemistry, Agricultural and Forest Meteorology, Ecological Engineering, Plant and Soil, Geoderma, Forest Ecology and Management, Applied Soil Ecology and the Journal of Agricultural, and Food Chemistry. One member of our group has received the “Agriculture Award of the Third World Network of Scientific Organization (TWNSO)”. Our group has also won the first prize of the National Science & Technology Progress Award and the first prize of the Provincial Science & Technology Progress Award. In addition, we have filed and received 21 patents. Five consulting reports have been adopted by General Office of the State Council of the People’s Republic of China.
Site degradation and management practices of timber plantation forests
Focusing on the problem of limited productivity and sustainable management of plantation forests, we have intensively studied productivity decline in replanted and monocultural plantations from the perspectives of soil chemistry, soil biology and plant nutrition. We have accomplished the following. Focusing on soil organic matter as a critical component of soil quality, we clarified the composition and characteristics of soil organic matter in typical subtropical forests, and described the development of soil fertility using labile soil organic matter as an index. Second, we found that stumps and other residues generated during plantation establishment play important roles in soil organic matter formation and nutrient recycling. As a result, we proposed the idea of shifting traditional management practices such as the burning of harvest residues during site preparation to retaining those residues. This is an important means of maintaining and enhancing the long-term productivity of plantation forest ecosystems, since harvest residues can provide the essential nutrients for tree growth of the next generation. Third, cyclic dipeptide as a new compound was isolated from soils of replanted Cunninghamia lanceolata plantations in southern China (Figure 9), and this has been shown to be the key allelopathic compound causing the decline in productivity of C. lanceolata plantation forests. This finding clarified the previous assumption that phenolic acids such as ρ-hydroxy benzoic acid are allelochemicals leading to the decline in productivity of replanted C. lanceolata plantation forests. Fourth, through study of the diversity and functions of soil fauna under different forest stands, we developed a new index to assess soil quality based on diversity, function and abundance of soil fauna. Fifth, based on comparisons among different broadleaved tree species mixed with C. lanceolata, we found that in the mixed plantation of C. lanceolata andMichelia macclurei, a planting ratio of 8 to 2 for the respective species can improve the site productivity.
The aforementioned findings were honored with the Provincial Science & Technology Progress Award and were published in 18 papers in international journals such as Soil Biology & Biochemistry, Journal of Agricultural and Food Chemistry, Biology and Fertility of Soils, Plant and Soil, Geoderma, and Forest Ecology and Management. In achieving these results, our group has been supported by the National Basic Research Program of China “Structure, function and regulation of main plantation forest ecosystem in China” and the National Natural Science Foundation of China (Key Program). Moreover, our consulting report “Suggestion on building high-quality and high-productivity timber plantation forests in subtropical and tropical China” was adopted by the General Office of the State Council of the People’s Republic of China.
Degradation processes of sandlands and demonstration experiments of vegetation restoration
Pinus sylvestris var. mongolica has been an important conifer tree species for the reforestation in the sandland region of north China. It has been introduced for sand fixation in the southern Horqin sandlands since the 1950s. Since that time, the expansion of sandland erosion has been a focus of control efforts with significant improvements achieved. These efforts have resulted in an increase in the area of broadleaf forests, shrubs, grass lands and farmlands, along with a significant decrease in the area of bare sandland. However, since the early 1990s P. sylvestris plantations that were originally introduced in the area have declined. Theseplantations are characterized by a shorter life span, shoot dieback, tree death and failure of natural regeneration. A series of studies based on water balance has been conducted and the mechanisms causing the decline of P. sylvestris plantations have been clarified. Due to the combination of precipitation and temperature over the same period, along with sufficient levels of rainfall, P. sylvestris has displayed faster growth in the early growth stage at the introduced sites. The life span of P. sylvestris in this region is shorter than that in the regions of origin. Spring drought in the introduced region impeded seed germination during the study period. Although the seed could germinate in the rainy season, the geminated seedlings could not survive due to ectomycorrhizal mortality caused by high temperatures in the surface soil. Sixty years after the introduction of P. sylvestris, we analyzed land use changes based on data accumulated from long-term monitoring to shed light on reasons for plantation dieback and mortality in sandlands. After 56 years of afforestation (1953–2009), the P. sylvestris plantations accounted for 12% of the total water consumption. In contrast, agricultural land and broadleaved forests accounted for more than 40% and 20% of total water consumption, respectively. The planting of broadleaved forests over large areas along with farmland expansion has resulted in the decline of the groundwater table. With the occurrence of an extreme drought year (approximately once every 15 years), in conjunction with a decreasing groundwater table, P. sylvestris plantations experienced difficulties in the uptake of underground water, weakening tree vigor and enhancing subsequent predisposition to insect and pathogen attacks. The ultimate outcome is dieback and mortality of trees. The groundwater table in the introduced region has declined at a rate of about 0.1 m per year for 60 years since the introduction of P. sylvestrisplantations.
Desertification is one of the major environmental issues in the western part of the Horqin Sandland. To properly manage vegetation in desertification-prone zones, it is crucial to understand the processes through which populations of psammophytes may expand. We studied how rhizomatous clonal plants (Phragmites communis) extended from interdune lowlands toward active sand dunes and their role in the restoration of sand dune vegetation. One important finding was that rhizomes extended at a rate of 5.2 m per year, and that the active sand dunes migrated at a rate ranging from 1.8 m to 3.8 m per year in the study site. Thus vegetative propagation of P. communis could play an important role in restoring the natural vegetation of the dune fields
The aforementioned findings have been published in international journals such as Soil Biology & Biochemistry, Agricultural Water Management, Journal of Applied Geophysics, Journal of Environmental Quality, Biological Conservation, Plant and Soil, Geoderma,and Forest Ecology and Management. One member of our group received the National Science Grant for Distinguished Young Scholars. The consulting report ‘Thoughts and suggestions on the degradation of protective plantations in China” has been adopted by the General Office of the State Council of the People’s Republic of China. Our work has been awarded the second prize for Science & Technology Awards by Liaoning Province and the Ministry of Science and Technology of China. We have established a large-scale comprehensive demonstration zone of 7000 ha in the western Horqin Sandland, which showcases our example of comprehensive management of the Horqin Sandland in the arid regions of China.
Forest management of the Three-North Shelterbelt
Our research has focused on management and evaluationof the benefits of the Three-North Shelterbelt region in China. Guidelines for the protection of mature shelter forests and a technological system for the management of shelter forests have been developed. Technologies for monitoring the health of mature shelter forests have also been developed.
Concepts related to the mature status of shelter forests have been clarified and quantitative methods to monitor mature age classes have been described. In this process, the growth of shelter forests has been partitioned into three phases ¾pre-mature stage, mature stage and regeneration stage. The core theory and technology has been published in the ‘Encyclopedia of World Ecology’. We used photographic technology with a fisheye lens to measure shelter forest canopy structure. We also developed a model including a widely-used software package to determine the relationship between shelter forest structure and readily measurable parameters. In addition, we have constructed a table for optimal light permeability for shelterbelt forests and a chart for optimal density regulation. These elements form a comprehensive technical system for the regulation and management of shelter forests.
Results of our research results have been published in international journals such as Agricultural and Forest Meteorology, Plant and Soil, Forest Ecology and Management,andthe Journal of Environmental Quality. In addition, we have received the "Agriculture Prize Award by the Third World Network of Scientific Organizations", the IUFRO Scientific Achievement Award, and the National Science & Technology Progress Award. Our consulting report "Effectiveness, existing problems and suggestions for future development of the Three-North Shelter Forest Program" has been adopted by the Central Office of China.
Carbon cycling in artificial forests and their responses to global climate change
Afforestation and reforestation have significant impacts on C, N and water cycling in terrestrial ecosystems. These are among the most important practices for reducing carbon emissions and increasing carbon sinks in terrestrial ecosystems according to the framework of the "Kyoto Protocol".
We have conducted research on carbon cycling in Chinese fir plantations in the subtropical region of southern China. Major accomplishments are as follows: 1) We found that a non-additive effect occurs in the decomposition process of mixed fir and broad-leaved litter, and that the rate of decomposition is affected by broad-leaved litter quality. Mixed litter of alder (Alnus) and Chinese fir (Cunninghamia lanceolata) is beneficial to litter decomposition and nutrient release; 2) We added additional carbon sources to soils in Chinese fir plantations, and the priming effect of exogenous carbon sources on carbon mineralization was quantified; 3) The relative contribution of litter and roots to soil carbon mineralization in Chinese fir plantations in subtropical ecosystems was determined, and we found that the carbon input from roots played a more important role than litter in soil carbon cycling processes; and 4) We discovered that the stability of deep soil organic carbon was greatly influenced by fresh litter input, which plays an important role in enhancing soil microbial activities and soil organic matter quality.
At the same time, our team has studied the effects of artificial forest plantations of different species on ecosystem carbon storage using stable 13C techniques. The effects of fir plantations in southern China and the Three-North Shelter Forest Program on regional terrestrial ecosystem carbon pools was evaluated adopting ‘3S’ technology and a large number of field investigations.
Increases in the concentration of CO2 and O3, N deposition, and change of precipitation patterns all have effects on pattern and process in terrestrial ecosystems. Using long-term observations via the open top chamber method, we determined the effects of increased CO2 and O3 concentrations on CO2 exchange in both leaf photosynthesis processes and active oxygen metabolism. We also simulated the effects of long-term nitrogen deposition on C and N cycling and soil biodiversity in artificial forest ecosystems. The sensitivity response of artificial forest ecosystems to nitrogen deposition was described.
Global climate change affects the amount and frequency of precipitation. How to simulate the effects of extreme precipitation events on ecosystem processes of terrestrial ecosystem remains a difficult challenge. Precipitation control experiments have been conducted in different artificial forest ecosystems, which may help reveal the response and sensitivity of these ecosystems to changes in precipitation patterns.
Our work has been published in mainstream international journals such as Soil Biology & Biochemistry, Agricultural and Forest Meteorology, Geoderma, Plant and Soil, Applied Soil Ecology, PLoS ONE, Global Change Biology, Environmental Science & Technology, and Environmental and Experimental Botany.
3 Forest Landscape Pattern and Process
The Center for Landscape Ecology and Regional Development was originally established as the Department of Landscape Ecology in 1988, the first such research institution in China. IAE sponsored and organized the first China Landscape Ecology Workshop in 1989. Since then six such workshops have been conducted, among which the Institute has sponsored two, co-sponsored one, and hosted one. The Institute also sponsored the Asia and Pacific Regional Landscape Ecology Workshop on two occasions. Since 1996 the Landscape Ecology Group has published 602 peer-reviewed papers and 16 books. Researchers from this group have received 8 national, provincial, and Chinese Academy of Sciences awards. One quarter of all Ph.D. and M.S. students in the field of landscape ecology in China have graduated from this Institute.
Over the last five years, significant achievements have been made in the development and application of forest landscape models, the analysis of the effects of forest landscape processes on forest landscape change, determination of the structure and function of urban forests, and in urban and regional landscape planning. The group has published 97 peer-reviewed papers in SCI journals including Global Change Biology, Ecological Applications, Landscape Ecology, Landscape and Urban Planning, PLoS ONE, International Journal of Wildland Fire, Forest Ecology and Management, Canadian Journal of Forest Research, and Forest Science, as well as 7 books. The group has also received four Science and Technology Achievement Awards from Liaoning Province and Shenyang City, and co-sponsored The 8th International Association of Landscape Ecology (IALE) World Congress held in Beijing in 2011. To date, 43 M.S. and 30 Ph.D. students have graduated from this program.
Development and validation of forest landscape models
Climatic change and forest landscape processes occur at large temporal (10–100 years) and spatial scales (1000–10,000,000 ha). Their interactions with forests and environments cannot be explained by the use of data from current vegetation surveys. Conventional approaches such as inventory, sampling, and monitoring are not adequate to answer questions at such large spatio-temporal scales. In addition, ecological factors interact at multiple scales in complex ways that cannot be described using simple quantitative expressions. Thus forest landscape models become an effective and necessary tool in addressing problems at large spatiotemporal scales. Since independent spatio-temporal time series data do not usually exist, predictions generated by forest landscape models at regional scales have been limited by computational capacity and difficulties in validating results. Scientists at the Institute have been involved in the development and applications of the forest landscape model LANDIS PRO 7.0. This model embodies two significant breakthroughs in forest landscape modeling. First, it expands the simulation capacity to regional scales (~108 ha) so that the modeled results can be compared to predictions made by regional-scale species distribution models (e.g., TreeAtlas/DISTRIB). Secondly, it has been redesigned to be compatible with forest inventory data, which may therefore be used for initialization, calibration, and validation. We have successfully applied the model to three major forest regions in Northeast China. We can now directly use the “second-tier” Forest Inventory Data of China for model initialization and calibration, and have satisfactorily evaluated long-term prediction results using old growth data. This work has addressed the core issues of forest landscape modeling and attracted the attention of numerous research communities. Research findings have been published in international journals such as Landscape Ecology, Forest Ecology and Management, and Landscape and Urban Planning. At the invitation of the editor-in-chief of Forest Ecology and Management, the flagship journal in its field, Dr. He and colleagues from the United States served as guest editors for a special issue on forest landscape modeling in 2008. He published a paper on forest landscape model definition, characterization, and classification. This paper provided a comprehensive review of the development, applications, and standardization of forest landscape models. Reviewers commented that the paper “tackles the core issues in forest landscape modeling”. It was among the 25 most downloaded papers for that year. Currently the LANDIS model is being applied in more than 100 countries and regions including the United States, Canada, United Kingdom, France, Finland, Switzerland, Germany, China, India, and Russia. Dr. He was invited by the International Association of Landscape Ecology and the International Union of Forest Research Organization to serve as conference chair, and also organized the International Workshop on Forest Landscape Modeling held in Beijing in 2006. He was also invited to make presentations at symposia in 2012 for the US-International Association for Landscape Ecology Annual Conference and in 2013 for the 98th Ecology Society of America Annual Meeting.
Long-term influences of large-scale spatial processes (e.g., fire and harvesting) on forest landscapes
Our group has proposed a theoretical framework that couples ecosystem and landscape models to study the role and influences of landscape processes in climate change, and to further improve the accuracy of ecological modeling and predictions. We focused on the long-term effects of landscape processes such as harvesting, plantation development, fire and fuel management in the forests of Northeast China. In particular, we have focused on: (1) Spatio-temporal patterns of fire occurrence in Northeast China and prediction of fire spread behavior; (2) Remote sensing assessment of burn severity and its effects on post-fire vegetational succession; and (3) Response of fire disturbance to climate change and its influences on regional forest productivity. More than 30 papers describing our results have been published in the International Journal of Wildland Fire, Forest Ecology and Management, Ecological Modeling, Ecological Applications, Global Change Biology, PLoS ONE, and Landscape Ecology. These papers have been cited by many peer scientists. In light of his research contributions, Dr. Hong S. He was invited to give a keynote presentation in this area at the 2007 World Congress of IALE.
Urban forest structure, function, and ecological benefits
Using Shenyang as a case study area, we have developed a strong research program of urban ecology and urban forestry, including studies of urban forest structure and function, ecological benefits of urban forests, and environmental assessment. In particular, we have (1) Proposed to use greenness indices to quantify urban forests at the species level; (2) Illustrated the response of major tree species in Shenyang to climate warming over the past 50 years, and shown that the recent 50-year climate of Shenyang is experiencing a warming and drying trend; and (3) Developed a systematic framework and survey to assess urban forests in China for the first time, and identified suitable tree species for urban forestry in northern Chinese cities. We have published approximately 50 SCI papers, 7 books, and filed 20 patents on this subject. We also received the Liaoning Province Scientific and Technological Improvement Award on two occasions, and a Shenyang City Award for Scientific and Technological Improvement.
Forest landscape process controls
We believe that forest landscape processes are important controls for ecosystem management. Proper fire management, harvesting regimes, and plantation practices are important for fostering forest regeneration, restoring forest health, and mitigating effects of climate change. We have emphasized the importance of integrating the principles of disturbance ecology within forest ecosystem management. Research findings have been published in top academic journals such as Ecology, Ecosystems, Journal of Biogeography, and Forest Ecology and Management. In 2010 when Russia experienced massive forest fires, we provided a strategic consulting report entitled “Challenges in Chinese forest fire management and possible solutions” to the Chinese Government, which was adopted by the General Office of the State Council of the People's Republic of China.