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  • Volume 12 Issue 5
    The picture desplays two study sites, including 70-80-year-old Pinus densiflora (top) and 80-90-year-old Quercus serrata (bottom) forests in the Gwangneung Experimental Forests, Pocheon, in central Korea. See Han et al. 871–881.
      
    Research Articles
    Zhiheng Wang, Yaoqi Li, Xiangyan Su, Shengli Tao, Xiao Feng, Qinggang Wang, Xiaoting Xu, Yunpeng Liu, Sean T. Michaletz, Nawal Shrestha, Markku Larjavaara, and Brian J. Enquist
    2019, 12 (5): 791-803.
    Abstract ( 168 )   PDF(pc) (2852KB) ( 43 )   Save
    Aims

    Plant height is a key functional trait related to aboveground biomass, leaf photosynthesis and plant fitness. However, large-scale geographical patterns in community-average plant height (CAPH) of woody species and drivers of these patterns across different life forms remain hotly debated. Moreover, whether CAPH could be used as a predictor of ecosystem primary productivity is unknown.

    Methods

    We compiled mature height and distributions of 11 422 woody species in eastern Eurasia, and estimated geographic patterns in CAPH for different taxonomic groups and life forms. Then we evaluated the effects of environmental (including current climate and historical climate change since the Last Glacial Maximum (LGM)) and evolutionary factors on CAPH. Lastly, we compared the predictive power of CAPH on primary productivity with that of LiDAR-derived canopy-height data from a global survey.

    Important Findings

    Geographic patterns of CAPH and their drivers differed among taxonomic groups and life forms. The strongest predictor for CAPH of all woody species combined, angiosperms, all dicots and deciduous dicots was actual evapotranspiration, while temperature was the strongest predictor for CAPH of monocots and tree, shrub and evergreen dicots, and water availability for gymnosperms. Historical climate change since the LGM had only weak effects on CAPH. No phylogenetic signal was detected in family-wise average height, which was also unrelated to the tested environmental factors. Finally, we found a strong correlation between CAPH and ecosystem primary productivity. Primary productivity showed a weaker relationship with CAPH of the tallest species within a grid cell and no relationship with LiDAR-derived canopy height reported in the global survey. Our findings suggest that current climate rather than historical climate change and evolutionary history determine the geographical patterns in CAPH. However, the relative effects of climatic factors representing environmental energy and water availability on spatial variations of CAPH vary among plant life forms. Moreover, our results also suggest that CAPH can be used as a good predictor of ecosystem primary productivity.

    Zhaoqi Wang, Jinfeng Chang, Shushi Peng, , Shilong Piao, Philippe Ciais and Richard Betts
    2019, 12 (5): 804-814.
    Abstract ( 116 )   PDF   Save
    Aims

    The impacts of future global warming of 1.5°C and 2°C on the productivity and carbon (C) storage of grasslands in China are not clear yet, although grasslands in China support ~45 million agricultural populations and more than 238 million livestock populations, and are sensitive to global warming.

    Methods

    This study used a process-based terrestrial ecosystem model named ORCHIDEE to simulate C cycle of alpine meadows and temperate grasslands in China. This model was driven by high-resolution (0.5° × 0.5°) climate of global specific warming levels (SWL) of 1.5°C and 2°C (warmer than pre-industrial level), which is downscaled by EC-EARTH3-HR v3.1 with sea surface temperature and sea-ice concentration as boundary conditions from IPSL-CM5-LR (low spatial resolution, 2.5° × 1.5°) Earth system model (ESM).

    Important Findings

    Compared with baseline (1971–2005), the mean annual air temperature over Chinese grasslands increased by 2.5°C and 3.7°C under SWL1.5 and SWL2, respectively. The increase in temperature in the alpine meadow was higher than that in the temperate grassland under both SWL1.5 and SWL2. Precipitation was also shown an increasing trend under SWL2 over most of the Chinese grasslands. Strong increases in gross primary productivity (GPP) were simulated in the Chinese grasslands, and the mean annual GPP (GPPMA) increased by 19.32% and 43.62% under SWL1.5 and SWL2, respectively. The C storage increased by 0.64 Pg C and 1.37 Pg C under SWL1.5 and SWL2 for 50 years simulations. The GPPMA was 0.670.880.39 (0.82) (model meanmaxmin0.670.390.88 (0.82) (model meanminmax (this study)), 0.851.240.45 (0.97)0.850.451.24 (0.97) and 0.941.300.61 (1.17)0.940.611.30 (1.17) Pg C year−1 under baseline, SWL1.5 and SWL2 modeled by four CMIP5 ESMs (phase 5 of the Coupled Model Inter-comparison Project Earth System Models). In contrast, the mean annual net biome productivity was −18.554.47−40.37 (−3.61),−18.55−40.374.47 (−3.61),18.6564.03−2.03 (10.29)18.65−2.0364.03 (10.29) and 24.1538.778.38 (24.93)24.158.3838.77 (24.93) Tg C year−1 under baseline, SWL1.5 and SWL2 modeled by the four CMIP5 ESMs. Our results indicated that the Chinese grasslands would have higher productivity than the baseline and can mitigate climate change through increased C sequestration under future global warming of 1.5°C and 2°C with the increase of precipitation and the global increase of atmospheric CO2 concentration.

    Yong Zhou, Xia Li, Hui Liu, Yubao Gao, Wade J. Mace, Stuart D. Card and Anzhi Ren
    2019, 12 (5): 815-824.
    Abstract ( 43 )   PDF   Save
    Aims

    The leaves of almost all terrestrial plant species are colonized by endophytic fungi. Compared to agronomic grasses, which usually harbor few endophytes, native grasses generally possess greater endophyte species diversity. Existing studies examining endophyte effects on natural grasses under competition normally considered the infection status (infected or uninfected), and rarely considered endophyte species.

    Methods

    We examined the effects of endophyte infection and of endophyte species on the interspecific competitive ability of a subdominant species, Achnatherum sibiricum, at two nitrogen levels (high nitrogen and low nitrogen). Achnatherum sibiricum plants infected by two different species of endophyte (Epichloë sibirica and E. gansuensis) and uninfected plants were grown in monoculture and binary mixtures with a dominant species, Stipa grandis (six individuals per species for monocultures and three + three individuals of each species in mixtures). Shoot and root biomass, tiller number and total phenolic concentration were measured after 3 months. Moreover, the aggressivity index was calculated to compare the competitive ability of Asibiricumrelative to Sgrandis.

    Important Findings

    Both Egansuensis (Eg)- and Esibirica (Es)-infected Asibiricum plants showed a greater competitive ability than the uninfected plants under high nitrogen supply, while the opposite result occurred under low nitrogen supply. At high nitrogen levels, Eg plants had a higher tiller number and a greater shoot biomass inhibitory effect on Sgrandis than Es plants had when growing in mixture, while Es plants showed better root growth performance than Eg and uninfected plants under mixture conditions at all nitrogen levels. A higher concentration of phenolic compounds in Eg plants than in Es plants might contribute to the higher inhibitory effect of Eg plants on competing plants. Our study indicates that the interaction between endophyte infection and nitrogen availability can alter the competitive ability of the host plant Asibiricum but that these two endophyte species work in different ways, which may influence the coexistence of Asibiricum with the dominant species.

    Aiying Zhang, Will Cornwell, Zhaojia Li, Gaoming Xiong, Dayong Fan and Zongqiang Xie
    2019, 12 (5): 825-833.
    Abstract ( 46 )   PDF   Save
    Aims

    Community assembly links plant traits to particular environmental conditions. Numerous studies have adopted a trait-based approach to understand both community assembly processes and changes in plant functional traits along environmental gradients. In most cases these are long-established, natural or semi-natural environments. However, increasingly human activity has created, and continues to create, a range of new environmental conditions, and understanding community assembly in these ‘novel environments’ will be increasingly important.

    Methods

    Built in 2006, the Three Gorges Dam, largest hydraulic project in China, created a new riparian area of 384 km2, with massively altered hydrology. This large, newly created ecosystem is an ideal platform for understanding community assembly in a novel environment. We sampled environment variables and plant communities within 103 plots located in both the reservoir riparian zone (RRZ) and adjacent non-flooded and semi-natural upland (Upland) at the Three Gorges Reservoir Area. We measured six traits from 168 plant species in order to calculate community-level distribution of trait values. We expected that the altered hydrology in RRZ would have a profound effect on the community assembly process for the local plants.

    Important Findings

    Consistent with previous work on community assembly, the distribution of trait values (range, variance, kurtosis and the standard deviation of the distribution neighbor distances) within all plots was significantly lower than those from random distributions, indicating that both habitat filtering and limiting similarity simultaneously shaped the distributions of traits and the assembly of plant communities. Considering the newly created RRZ relative to nearby sites, community assembly was different in two main ways. First, there was a large shift in the mean trait values. Compared to Upland communities, plant communities in the RRZ had higher mean specific leaf area (SLA), higher nitrogen per unit leaf mass (Nmass), and lower maximum height (MH). Second, in the RRZ compared to the Upland, for the percentage of individual plots whose characteristic of trait values was lower than null distributions, the reductions in the community-level range for SLA, Nmass, nitrogen per unit leaf area (Narea) and phosphorus per unit leaf area (Parea) were much larger, suggesting that the habitat filter in this newly created riparian zone was much stronger compared to longer established semi-natural upland vegetation. This stronger filter, and the restriction to a subset of plants with very similar trait values, has implications for predicting riparian ecosystems’ responses to the hydrological alterations and further understanding for human’s effect on plant diversity and plant floras.

    Tingting An, Mingjie Xu, Tao Zhang, Chengqun Yu, Yingge Li, Ning Chen, Jiaxing Zu, Junxiang Li, Juntao Zhu, Yi Sun, Tingting Zhao and Guirui Yu
    2019, 12 (5): 834-845.
    Abstract ( 40 )   PDF   Save
    Aims

    Evapotranspiration (ET) is an important component of the terrestrial water cycle and is easily affected by external disturbances, such as climate change and grazing. Identifying ET responses to grazing is instructive for determining grazing activity and informative for understanding the water cycle.

    Methods

    This study utilized 2 years (2014 and 2017) of eddy covariance data to test how grazing regulated ET for an alpine meadow ecosystem on the Tibetan Plateau (TP) by path analysis.

    Important Findings

    Radiation dominated ET with a decision coefficient of 64–74%. The soil water content (SWC) worked as the limiting factor in the fenced site. However, in the grazing site, the limiting factor was the vapor pressure deficit (VPD). Grazing had large effects on ET because it greatly affected the water conditions. The SWC and VPD were enhanced by 14.63% and 4.36% in the grazing site, respectively. Therefore, sufficient water was supplied to ET, especially during drought, and strengthened the transpiration pull. As a result, a favorable micrometeorological environment was created for ET. Grazing shifted the limiting factor of ET from the SWC to VPD, which weakened the limiting effect of the water conditions on ET and advanced the ET peak time. In addition, grazing altered the compositions of ET by changing the community structure, which directly resulted in an increased ET. In summary, grazing enhanced ET through altering the community structure and micrometeorological environments. The findings of this study further improve our understanding of the driving mechanisms of grazing on ET and will improve our predictions for the global water cycle.

    Ling-Yun Wan, Shan-Shan Qi, Chris B. Zou, Zhi-Cong Dai, Guang-Qian Ren, Qi Chen, Bin Zhu and Dao-Lin Du
    2019, 12 (5): 846-856.
    Abstract ( 49 )   PDF   Save
    Aims

    Change in nitrogen (N) availability regulates phosphorus (P) acquisition and potentially alters the competition among native species and invasive weeds. This study determines how current and projected N deposition affect the growth, the intraspecific and interspecific competitive ability of native and invasive plants in calcareous soils with low P availability.

    Methods

    A controlled greenhouse experiment was conducted using sparingly soluble hydroxyapatite (HAP) to simulate the calcareous soils with low P availability. The growth and competitive intensity between an invasive weed (Solidago canadensis) and a native weed (Pterocypsela laciniata) exposed to two levels of N addition representative of current and future N deposition in China were experimentally determined.

    Important Findings

    P acquisition and the growth of both S. canadensis and P. laciniata growing alone significantly increased with increasing N level. However, the effect of N addition was reduced when intraspecific or interspecific competition existed. N addition altered the competitive relationship between S. canadensis and P. laciniata allowing S. canadensisto out-compete P. laciniata due to variation in P acquisition from HAP. Elevated N deposition might assist the invasion of S. canadensis in the widely distributed calcareous soils under environmental changes.

    Huan-Huan Song, Tao Yan and De-Hui Zeng
    2019, 12 (5): 857-870.
    Abstract ( 25 )   PDF   Save
    Aims

    Mongolian pine (Pinus sylvestris var. mongolica) and Xiaozhuan poplar (Populus × xiaozhuanica) are two predominant afforestation tree species in the semi-arid sandy lands of northeast China, which are characterized by poor soil nutrients. Plant litter decomposition plays a critical role in regulating nutrient cycling in terrestrial ecosystems. Admixture of broadleaf litter to conifer litter is expected to improve litter decomposition and soil fertility, and thus productivity. However, the effects on the decomposition of litter mixture of the above two tree species are not well understood. Therefore, it is essential to assess the decomposition performance of litter mixture with the aim of improving forest nutrient management and the establishment of mixed plantation. Appropriate forest management practice is critical for the sustainability of site productivity in plantation forests.

    Methods

    We conducted a field litterbag decomposition transplant experiment for single pine litter, single poplar litter and their mixture in a pine stand, a poplar stand and an adjacent grassland for 16 months in the Keerqin Sandy Lands, northeast China.

    Important Findings

    After 16 months of incubation, there remained significantly more litter mass of pine (73.8%) than of poplar (67.2%). The mass remaining was positively correlated with litter carbon (C):nitrogen (N), C:phosphorus (P) and lignin:N ratios, and negatively with litter N and P concentrations, which suggests that initial litter chemical properties were an important factor affecting litter decay. Generally, net N and P immobilizations were observed during decomposition. This indicates that litter decomposition in this area was N-limited as N was progressively immobilized, and then tended to induce P limitation. Thus, we strongly recommend prohibiting litter harvesting by local residents to maintain soil fertility in this nutrient-poor area. Our results do not support the home-field advantage hypothesis, as illustrated by the fact that, in most cases, mass loss of litter from native habitat was comparable to that in transplanted habitats during decomposition. Furthermore, a dominant additive effect was detected, indicating that the establishment of mixed plantation may not be appropriate for these two species.

    Seung Hyun Han, Seongjun Kim, Hanna Chang, Hyun-Jun Kim, Asia Khamzina and Yowhan Son
    2019, 12 (5): 871-881.
    Abstract ( 36 )   PDF   Save
    Aims

    Assessment of factors regulating root decomposition is needed to understand carbon and nutrient cycling in forest ecosystems. The objective of this study is to examine the effects of soil depth and root diameter on root decomposition and to analyze the relationship of root decomposition with factors such as soil environmental conditions and initial litter quality.

    Methods

    Two decomposition experiments were conducted in natural pine (Pinus densiflora) and oak (Quercus serrata) forests over a 2-year period using the litterbag technique. For the soil depth experiment, 216 litterbags containing fine roots (∅ = 0–2 mm) were buried at 0–10-, 10–20- and 20–30-cm soil depths. Soil properties and soil enzyme activities and microbial biomass at each soil depth were analyzed. For the root diameter experiment, 216 litterbags containing roots 0–1-, 1–2- and 2–3-mm in diameter were buried at 10-cm soil depth. The initial litter qualities (carbon (C), nitrogen (N), calcium (Ca) and phosphorus (P) concentrations) for each of the root diameter classes were analyzed. Litterbags were retrieved after 3, 6, 12 and 24 months in each forest type.

    Important Findings

    The root decomposition rate was significantly altered by soil depth and root diameter. After 2 years, the root decay constant at 0–10-cm depth (pine: 0.35 and oak: 0.41) was significantly higher than that at 10–20-cm (0.31 and 0.37) and 20–30-cm (0.32 and 0.33) depths in the P. densiflora and Q. serrata forests. Enzyme activities and microbial biomass declined with soil depth, which may be associated with decreasing soil moisture and organic matter. The decay constant for the 0–1-mm roots (pine: 0.32 and oak: 0.37) was higher than that of 1–2-mm (0.29 and 0.33) and 2–3-mm roots (0.26 and 0.33) for the P. densiflora and Q. serrata forests. Difference in initial P concentration and C/N ratio among the different diameter roots were linearly related with root decomposition. In particular, the increasing C/N ratio with root diameter resulted in decreases in the decomposition rate. These results indicate the surface soil microbial activities and initial C/N ratio of root litter as important drivers of C dynamics in temperate pine and oak forests.

    Yin Li, Helge Bruelheide, Thomas Scholten, Bernhard Schmid, Zhenkai Sun, Naili Zhang, Wensheng Bu, Xiaojuan Liu and Keping Ma
    2019, 12 (5): 882-893.
    Abstract ( 35 )   PDF   Save
    Aims

    Tree species richness has been reported to have positive effects on aboveground biomass and productivity, but little is known about its effects on soil organic carbon (SOC) accumulation.

    Methods

    To close this gap, we made use of a large biodiversity–ecosystem functioning experiment in subtropical China (BEF-China) and tested whether tree species richness enhanced SOC accumulation. In 2010 and 2015, vertically layered soil samples were taken to a depth of 30 cm from 57 plots ranging in tree species richness from one to eight species. Least squares-based linear models and analysis of variance were used to investigate tree diversity effects. Structural equation modeling was used to explore hypothesized indirect relationships between tree species richness, leaf-litter biomass, leaf-litter carbon content, fine-root biomass and SOC accumulation.

    Important Findings

    Overall, SOC content decreased by 5.7 and 1.1 g C kg−1 in the top 0–5 and 5–10 cm soil depth, respectively, but increased by 1.0 and 1.5 g C kg−1 in the deeper 10–20 and 20–30 cm soil depth, respectively. Converting SOC content to SOC stocks using measures of soil bulk density showed that tree species richness did enhance SOC accumulation in the different soil depths. These effects could only to some extent be explained by leaf-litter biomass and not by fine-root biomass. Our findings suggest that carbon storage in new forests in China could be increased by planting more diverse stands, with the potential to contribute to mitigation of climate warming.

    Jordi Bou, and Lluís Vilar
    2019, 12 (5): 894-906.
    Abstract ( 32 )   PDF   Save
    Aims

    Our aims were 3-fold: (i) to determine whether global change has altered the composition and structure of the plant community found in the sessile oak forests on the NE Iberian Peninsula over the last decades, (ii) to establish whether the decline in forest exploitation activities that has taken place since the mid-20th century has had any effect on the forests and (iii) to ascertain whether there is any evidence of impact from climate warming.

    Methods

    We assess changes in the plant community by comparing a current survey of sessile oak forest with a historical data set obtained from previous regional studies dating from 1962 to 1977. We analyse the regional changes in the community in terms of biodiversity variables, species composition and plant traits. Furthermore, plants traits such as plant life forms and chorological groups are used to discern any effects from land-use changes and climate warming on the plant community.

    Important Findings

    There has been a loss of diversity in the community and, in the hottest region, there is also a loss of species richness. The composition of the community suggests that, although significant changes have taken place over recent decades, these changes differ between regions as a result of the low impact global change has had in the western regions. For instance, while the tree canopy cover in the western sessile oak forests remains stable, the eastern sessile oak forests are still recovering from the former exploitation that led to a loss of their rich and abundant herbaceous stratum. In fact, the recovery process in the Catalan Pre-Coastal Range has constituted an increase in the Euro-Siberian plants typical to this community. Moreover, in the eastern forests, there is evidence that climate warming has impacted the thermophilization of the sessile oak forests found on the Coastal Range.

    Yumei Li, Yun Zhang, Zhaochen Kong, Long Zhao, Li Wang, Yuanyuan Li and Lixin Chen
    2019, 12 (5): 907-916.
    Abstract ( 37 )   PDF   Save
    Aims

    Climate change can significantly affect the vegetation worldwide. Thus, paleovegetation and paleoclimate reconstruction should consider the quantitative relationship between modern vegetation and climate. The specific objectives of this study were (i) to assess the influence of environmental variables on pollen assemblages in the Kanas region, (ii) to reconstruct the evolution of vegetation over the past 3000 years using pollen records and (iii) to quantify historical climate change (including mean annual temperature and total annual precipitation) using a weighted averaging partial least squares regression method (WAPLS) applied to fossil pollen data from the Kanas wetland in Xinjiang, China.

    Methods

    A total of 65 surface and 50 fossil samples were collected from the Kanas wetland and analysed for 14C, pollen and grain size. By combining these data with those obtained from 214 samples of surface pollen assemblages in north Xinjiang, the late Holocene climate was reconstructed using a WAPLS model.

    Important Findings

    The vegetation in Kanas was dominated by forest for the past 3000 years, undergoing an arbour-vegetation transition from predominantly pine to spruce over that period. The WAPLS model showed that the paleoclimate progressed from cold-wet to warm-dry and subsequently back to cold-wet. Prior to 1350 calibrated years before the present (cal. yr BP), the climate of Kanas was cold and wet, and conditions became increasingly warm and dry until 870 cal. yr BP. The temperature reconstruction model indicated that a ‘Little Ice Age’ occurred ~380 cal. yr BP. These data will help us improve the understanding of abrupt climate change and provide important information regarding the prediction of climate.

Impact Factor
1.833
5 year Impact Factor
2.299
Editors-in-Chief
Wen-Hao Zhang
Bernhard Schmid