As a nature-based and cost-effective solution, forestation plays a crucial role in combating global warming, biodiversity collapse, environmental degradation, and global well-being. Although China is acknowledged as a global leader of forestation and has achieved considerable overall success in environmental improvements through mega-forestation programs, many negative effects have also emerged at local scales due to the planting of maladapted tree species. To better help achieve carbon neutrality and the new vision of an ecological civilization, China has committed to further increase forestation. However, where forestation lands and such efforts should really be located is not so well understood yet and agreed upon, especially in the face of rapid climate change. Based on an ensemble-learning machine, we predicted the spatial habitats (ecological niche) of the forest, grassland, shrubland, and desert under present and future climate conditions based on the natural climax vegetation distribution across China. We show that the potential forestation lands are mainly located in eastern China, which is east of the Hu Line (also known as the Heihe-Tengchong Line). Under future climate change, forests will shift substantially in the latitudinal, longitudinal, and elevational distribution. Potential forestation lands will increase by 33.1 million hectares through the 2070s, mainly due to the conversions of shrub and grassland to forests along the Hu Line. Our prediction map also indicates that grassland rehabilitation is the universal optimal vegetation restoration strategy in areas west of the Hu Line. This analysis is consistent with much of the observed evidence of forestation failures and recent climate-change-induced forest range shifts. Our results provide an overview and further show the importance of adaptive science-based forestation planning and forest management. 

Where should China practice forestry in a warming world?

Forest policy and decision-makers are challenged by the need to balance the increasing demand for multiple ecosystem services while addressing the impacts of natural disturbances (e.g., wildfires, droughts, wind, insect attacks) and global change scenarios (e.g., climate change) on its potential supply. This challenge motivates the development of a framework for incorporating concerns with a wide range of ecosystem services in multiple criteria management planning contexts. Thus, the paper focused on both the analysis of the current state-of-the art research in forest management planning and the development of a conceptual framework to accommodate various components in a forest management process. On the basis of a thorough recent classification of forest management planning problems and the state-of-the-art research, we defined the key dimensions of the framework and the process. The emphasis was on helping to identify how concerns with a wide range of ecosystem services may be analyzed and better understood by forest ecosystem management planning. This research discusses the potential of contemporary management planning approaches to address multiple forest ecosystem services. It highlights the need for a multi-level perspective and appropriate spatial resolution to integrate multiple ecosystem services. It discusses the importance of methods and tools that may help support stakeholders’ involvement and public participation in hierarchical planning processes. The research addresses the need of methods and tools that may encapsulate the ecological, economic, and social complexity of forest ecosystem management to provide an efficient plan, information about tradeoffs between ecosystem services, and the sensitivity of the plan to uncertain parameters (e.g., prices, climate change) on time.

A Design for Addressing Multiple Ecosystem Services in Forest Management Planning

Both in Germany and in China, there is strong expertise regarding the different aspects of forest management, as well as forest products management. Nevertheless, forestry in both countries is facing challenges, some of which are regional, but many of which are shared. Therefore, experts from both countries (Technical University of Munich Germany; Northwest AF Forestry Academy of Shaanxi, China; Thunen Institut, Germany; FEDRC GIZ Forest Policy Facility (Forestry Economics Development and Research Center of the Deutsche Gesellschaft fur Internationale Zusammenarbeit GmbH), Germany; and Center for Natural Forest Protection in Shaanxi, China) met to share their knowledge and deduce recommendations for future multifunctional forest management for the temperate zone. The workshop, held at the Northwest A&F University in September 2018, included presentations and intensive discussions, as well as a field tour. The results of the workshop that are summarized in this white paper are meant to provide an overview of the multi-faceted nature of the topic for interested scientists and forest practitioners, describe tools that can be used to analyze various aspects of multifunctionality and, in an exemplary fashion, highlight gathered experience from long- and short-term experiments. Included are social demands, economic goals, and scientific baselines. The topics reach from economic evaluations of forest ecosystem services over forest management practices, including afforestation, restoration, and preparations to face climate change, to wood/forest products utilization and participation of local people for poverty reduction. Overall, an optimistic picture emerges, showing that by using adapted forest management practices, which try to embrace the concept of multifunctionality, various use schemes and demands can be integrated at single sites, allowing us to achieve both environmental protection and productive forests, including societal demands, as well as aspects of tradition and national identity.

https://www.mdpi.com/1999-4907/11/3/266/pdf

Multifunctionality of Forests: A White Paper on Challenges and Opportunities in China and Germany

Forest carbon exchange and use efficiency (the capacity of transferring gross primary production to net ecosystem production) play an important role in regulating the atmospheric carbon balance and thus affecting the climate. Here, we conducted a synthesis of eddy covariance fluxes measurement across China's typical forests to examine the magnitude, pattern and controls of forest carbon fluxes and carbon use efficiency. The results showed that China's forests had strong carbon sink capacity and high carbon use efficiency. The average annual gross primary production (GPP), ecosystem respiration (RE) and net ecosystem production (NEP) of forests was 1541 ± 92, 1155 ± 91 and 382 ± 37 g C m−2 a−1, and the average NEP:GPP, RE:GPP and NEP:RE was 0.25 ± 0.02, 0.74 ± 0.02 and 0.36 ± 0.04, respectively. Both carbon fluxes and use efficiency significantly varied with biomes, presenting higher values in subtropical and temperate forests than tropical and boreal forests. GPP and RE geographically decreased linearly with latitude increasing, while the NEP and its ratios to GPP and RE peaked at the mid-latitude. Large variances of carbon fluxes and use efficiency were mainly attributable to the regulation of mean annual temperature (MAT). MAT explained 40–54% of the variation in carbon fluxes, and 21–47% of variation in carbon use efficiency. Our result also indicated that carbon use efficiency was affected by stand age that presented an apparent decreasing trend from young to old-growth forests. The results advance our understanding about the variances and controls of carbon exchange and use efficiency and are valuable for regional carbon budget assessment.

Magnitude, pattern and controls of carbon flux and carbon use efficiency in China's typical forests

Forests play a crucial role by regulating the global and local weather through the exchange of atmospheric gases and water vapor. The present study aims to study the intra-annual variability of net ecosystem exchange (NEE) of carbon dioxide in a sal (Shorea robusta) dominated moist deciduous forest in India by integrating eddy covariance (EC) data and Biome-Biogeochemical Cycle (Biome-BGC) model. The study also attempts to address the spatial variability of NEE with respect to phenology. Monthly average NEE were estimated using a calibrated Biome-BGC model and the spatial NEE was mapped using random forest (RF) regression algorithm. Phenology metrics were generated using the moderate resolution imaging spectrometer (MODIS) enhanced vegetation index product (MOD13A2) and its relationship with the estimated NEE was studied. RF regression model for monthly average spatial NEE estimation was built with an R2 of 0.84 and % RMSE of 3.68%. The study revealed that the NEE at the regional scale can be estimated using the basic meteorological variables like mean temperature, vapor pressure deficit, minimum temperature and total precipitation. Biome-BGC model output showed that the sal forest of the study area acted as a net sink of carbon in almost all months of 2015, except April to June. Peak NEE value (− 2.80 to − 2.96 g C m−2 day−1) was observed during October month. Annual NEE of sal forest in 2015 was found to be − 526.87 g C m−2 year−1. With the start of season (end of June), sal forest showed an increasing trend in NEE while decreasing trend was observed at the end of season (end of October). The study showed the applicability of Biome-BGC model in Indian forest when integrated with EC data. The study also highlighted the utility of RF in capturing the spatial variability of NEE over large area.

Integration of eddy covariance and process-based model for the intra-annual variability of carbon fluxes in an Indian tropical forest

The carbon balance of forests is controlled by many component processes of carbon acquisition and carbon loss and depends on the age of vegetation, soils, species composition, and the local climate. Thus, examining the carbon balance of different forests around the world is necessary to understand the global carbon balance. Nevertheless, the available information on the carbon balance of Larix principis-rupprechtii forests in the Qinling Mountains remains considerably limited. We provide the first set of results (2010–2013) from a long-term project measuring forest-atmosphere exchanges of CO2 at the Qinling National Forest Ecosystem Research Station (QNFERS), and compare the net ecosystem exchange (NEE) based on biometric measurements with those observed via the eddy covariance method. We also compare the total ecosystem respiration via scaled-up chamber and eddy covariance measurements. The net primary productivity (NPP) was 817.16 ± 81.48 g·C·m−2·y−1, of which ΔBliving and Dtotal accounted for 77.7%, and 22.3%, respectively. Total ecosystem respiration was 814.47 ± 64.22 g·C·m−2·y−1, and cumulative annual soil respiration, coarse woody debris respiration, stem respiration, and leaf respiration were 715.47 ± 28.48, 15.41 ± 1.72, 35.28 ± 4.78, and 48.31 ± 5.24 g·C·m−2·y−1, respectively, accounting for 87.85%, 1.89%, 4.33%, and 5.93% of the total ecosystem respiration. A comparison between ecosystem respiration from chamber measurements and that from eddy covariance measurements showed a strong linear correlation between the two methods (R2 = 0.93). The NEE of CO2 between forests and the atmosphere measured by eddy covariance was −288.33 ± 25.26 g·C·m−2·y−1, which revealed a carbon sink in the L. principis-rupprechtii forest. This number was 14% higher than the result from the biometric measurements (−336.71 ± 25.15 g·C·m−2·y−1). The study findings provided a cross-validation of the CO2 exchange measured via biometric and eddy covariance, which are beneficial for obtaining the true ecosystem fluxes, and more accurately evaluating carbon budgets.

https://www.mdpi.com/1999-4907/9/2/67/pdf

Biometric and Eddy Covariance Methods for Examining the Carbon Balance of a Larix principis-rupprechtii Forest in the Qinling Mountains, China

Coarse woody debris (CWD) is an essential component in defining the structure and function of forest ecosystems. Long-term dynamics of CWD characteristics not only affect the release rates of chemical elements from CWD, but also the species diversity of inhabiting plants, animals, insects, and microorganisms as well as the overall health of ecosystems. However, few quantitative studies have been done on the long-term dynamics of CWD characteristics in forest ecosystems in China. In this study, we conducted nine tree censuses between 1996 and 2016 at the Huoditang Experimental Forest in the Qinling Mountains of China. We quantified forest biomass including CWD and CWD characteristics such as decay states and diameter classes during this period and correlated with stand, site, and climatic variables. The forest biomass was dominated by live tree biomass (88%); followed by CWD mass (6%–10%). Understory biomass contributed only a small portion (1%–4%) of the overall biomass. Significant differences in average annual increment of CWD mass were found among forest stands of different species (p < 0.0001). Forest biomass, stand age, forest type, aspect, slope, stand density, annual average temperature, and precipitation were all significantly correlated with CWD mass (p < 0.05), with forest type exhibiting the strongest correlation (r2 = 0.8256). Over time, the annual mass of different CWD characteristics increased linearly from 1996–2016 across all forest types. Our study revealed that forest biomass, including CWD characteristics, varied by forest type. Stand and site characteristics (forest biomass, forest type, aspect, slope and stand density) along with temperature and precipitation played a major role in the dynamics of CWD in the studied forest ecosystems.

https://www.mdpi.com/1999-4907/8/10/403/pdf

Lin Hou

Papers

Multifunctionality of Forests: A White Paper on Challenges and Opportunities in China and Germany

Biometric and Eddy Covariance Methods for Examining the Carbon Balance of a Larix principis-rupprechtii Forest in the Qinling Mountains, China

Dynamics of Coarse Woody Debris Characteristics in the Qinling Mountain Forests in China