Table of Content

10 November 2017, Volume 36 Issue 11

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Estimation and spatial distribution of aboveground carbon storage for natural Pinus sylvestris var. mongolica forests on sandy land.

CONG Jun-xia1, ZHENG Xiao2,3*, ZHU Jiao-jun2,3, SONG Li-ning2,3, GAO Xi-ning1, LI Xiu-fen1, YAN Tao2,3

2017, 36(11):  2997-3007. 

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Accurate estimation of carbon storage and carbon density of a single category of forest is an important basis for studying regional forest carbon storage. Pinus sylvestris var. mongolica (MP) natural forests were selected as the object of this study, and a new method for estimating MP stand structure was established based on the combination of inventory data, ground survey data and multisource remote sensing data. Based on the method, we estimated the carbon storage and carbon density of MP forests in the natural concentrated distribution region (the region of Honghuaerji Forestry Bureau under the jurisdiction of Inner Mongolia). Finally, the topographic features of carbon storage and carbon density of MP forests were discussed in combination with topographic features. The results showed that there was a significant linear relationship between diameter at breast height and Tasseled Cap Greenness of Landsat8 OLI. The area of the natural MP forests in the study region was 70923.30 hm² in 2016, the aboveground (stem, branch and leaf) carbon storage was 3.91 Tg C, and average carbon density was 55.18 t·hm^-2 (10.26-148.75 t·hm^-2). Influenced by human interference and natural elements, the carbon storage and carbon density increased first and then decreased with increasing altitude, whereas it decreased with increasing slope. The maximum carbon density occurred on the sunny slope and the minimum value was located on the shade slope due to the heliophilous characteristics for the MP. According to the spatial distribution characteristics of carbon storage and carbon density, subregionspecific management can significantly improve carbon sink.

 

Effect of planting density on the aboveground growth and fine root biomass in Fraxinus mandschurica Rupr. plantation.

GU Jia-cun*, XIAO Li-juan, MA Zhen-dong, XIA Xiu-xue, GAO Guo-qiang

2017, 36(11):  3008-3016. 

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Stand density has an important influence on the growth of individual trees and the accumulation of stand volume; however, the relationship between stand density and tree’s fine roots is still not well understood. We conducted an experiment in Fraxinus mandschurica Rupr. plantations with four planting densities (Treatment I: 1.0 m×1.0 m, II: 1.5 m×1.5 m, III: 2.0 m×2.0 m, and IV: 1.5 m×3.0 m) in Maoershan, Heilongjiang, China, and measured the diameter at breast height (DBH), selfthinning proportion from 2012 to 2016, leaf biomass production in 2013, 2014 and 2016, and used soil core and ingrowth core methods to estimate the standing biomass and biomass production of fine roots (diameter ≤2.0 mm ) and absorptive roots (diameter ≤0.5 mm). Results showed that the Treatment I had the highest branching intensity (31.55%) and the lowest tree height, while Treatment III had the largest mean DBH and tree height. Leaf biomass production increased with increasing stand age across all treatments, with the maximum occurring in Treatment II. Treatment I had the highest total selfthinning proportion. During the study period, the survivorship of living trees at the plot level was negatively correlated with annual leaf biomass production and increment of DBH (the former was statistically significant). Both fine roots and absorptive roots showed the largest standing biomass and production in Treatment IV, in which standing biomasses of absorptive roots were (184.62±17.73), (146.45±5.59), (150.32±5.39) and (242.81±19.07) g·m^-2 in Treatment I to IV, respectively. At the plot level, both standing biomass and production of absorptive roots were negatively correlated with stand density (the latter was statistically significant). Ratios of annual production of absorptive roots to leaf production and to annual increment of DBH were the highest in Treatment IV, but were similar among the other three treatments. In summary, the initial planting density of 2500 ind·hm^-2 was the optimal choice as manifested by the largest mean DBH and tree height, higher survivorship of living trees as well as the balanced biomass allocation between absorptive roots and leaves.

The effects of thinning on soil enzyme activities in Larix kaempferi plantations with different site conditions.

YU Li-zhong1,2*, ZHANG Jing-pu1,2, LIU Li-fang1,2, ZHANG Jin-xin1,2, YANG Kai1,2

2017, 36(11):  3017-3027. 

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Thinning is an important forest management practice promoting tree growth and influencing soil properties in plantations, especially for soil microorganisms and enzyme activities. The objective of this study was to determine the effects of different thinning intensities on soil enzyme activities in Larix kaempferi plantations. This study was conducted in two different site conditions (high or low soil fertility) in the montane region of eastern Liaoning Province of Northeast China. The thinning treatments included control treatment, 25% and 50% thinning intensity. The results showed that the phenol oxidase activity was higher in autumn season than in other seasons, while the activities of exoglucanase, β-glucosidase, N-acetyl-β-glucosaminidase, acid phosphatase were higher in spring season than in summer and autumn seasons at the two sites. In addition, the 25% thinning treatment significantly increased the activities of phenol oxidase and Nacetylβ-glucosaminidase in the 0-10 cm soil layer, whereas 25% and 50% thinning treatments decreased the activities of β-glucosidase, N-acetylβvglucosaminidase, acid phosphatase in the 10-20 cm soil layer at the low soil fertility site. There were significant positive correlations between enzyme activities and soil total carbon, total nitrogen and inorganic nitrogen when all samples were pooled together. In contrast, these studied enzyme activities were negatively correlated with soil pH. Especially, the correlations between soil enzyme activities and inorganic nitrogen decreased in the 25% thinning treatment at the low soil fertility site. In addition, the correlations between soil enzyme activities and soil total carbon, available phosphorus also decreased, while the correlations between soil enzyme activities and soil total phosphorus increased in the 50% thinning treatment at the high soil fertility site. In conclusion, to improve the soil enzyme activities, 25% and 50% thinning intensity should be conducted in Larix kaempferi plantations with low and high soil fertility, respectively.

Effects of mixed Pinus tabuliformis and Quercus mongolica plantation on the functional diversity of soil microbial community.

DENG Jiao-jiao1,2, ZHOU Yong-bin1,2, YIN You2, ZHANG Song-zhu2, ZHU Wen-xu2*

2017, 36(11):  3028-3035. 

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Soil microorganisms play important roles in material and energy flows of terrestrial ecosystems; understanding the changes of function and structure of soil microorganisms is of great significance to the study of the whole ecosystem. In order to evaluate the effect of the mixed Pinus tabuliformis Carr. + Quercus mongolica Fisch. ex Ledeb. forest on soil microbial community functional diversity, by using Biolog Ecoplate system, this paper studied the functional diversity of soil microbial community under three different vegetation types in Jianping County, Liaoning Province, including pure P. tabuliformis Carr. forest (YC), novegetation soil (NP), and mixed P. tabuliformis Carr. + Q. mongolica Fisch. ex Ledeb. forest (YM). The results showed that soil microbial metabolic activity (AWCD) was in the order of YM>YC>NP, and soil microbial metabolic activity of NP was the lowest. There were variations in carbon utilization by soil microbial communities among the three plantation forests. Soil microbes in the mixed forest had significantly higher utilization rates in L-asparagine, L-phenylalanine, L₄₀ serine, L-threonine, Tween-40, D-galactose acid-γ-fat, phenethylamine, D-glucose, amino acid, 4-hydroxy benzoic acid than in the YC (P<0.05). Principal component analysis showed that carbohydrate and amino acids were important factors affecting soil metabolic activity. The Shannon’s diversity index of soil microbes was not significantly different among the three plantation forests. The McIntosh’s index was in order of YM>YC>NP, while there was no significant difference in Simpson’s index between the YM and YC, and both had significantly higher Simpson’s index than NP. Our results demonstrated that planting P. tabuliformis and Q. mongolica trees together can promote soil microbial activity.

Allocation of soil aggregates, organic carbon and microbial biomass carbon affected by agroforestry modes in Pinus sylvestris var. mongolica plantations in sandy area.

GUO Xin-wei1,2, LI Zhi-yuan1,2, QIN Sheng-jin1,2, ZHOU Yong-bin1,2, WEI Ya-wei1,2*

2017, 36(11):  3036-3042. 

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The objective of this study was to assess how agroforestry modes affect allocation of soil aggregates (SA), organic carbon (SOC) and microbial biomass carbon (MBC). We measured the contents of the SA, SOC and MBC in three modes: Pinus sylvestris var. mongolica (PS), P. sylvestris var. mongolica-Arachis hypogaea (PA), P. sylvestris var. mongolica-Setaria italica (PH) in Fujia Forest Farm, Northwest Liaoning. The results showed that (1) the aggregate composition was dominated by particles of 0.053-0.25 mm which accounted for 37%-45% of the total under the three modes and the proportion of soil aggregates with particles >0.25 mm was the highest in the PH. (2) The change pattern of organic carbon content in aggregates with aggregate size was significantly different between the two kinds of agroforestry (P<0.05). The distribution of organic carbon contents in soil aggregates with the increase of aggregate size exhibited an “upsidedown N type” for PA and a “N” type for PH. (3) SOC and MBC in the toplayer soil (0-20 cm) of the three modes were in the order of PH > PS > PA. (4) The SOC accumulation was mainly influenced by the contents of aggregates of 0.053-0.25 mm and >2 mm. In addition, MBC was significantly correlated with SOC in 0-50 cm soil layer in the PH, but not in the PA. These results indicate that agroforestry modes can affect MBC and SOC contents.

Effects of gap size on soil microbial biomass carbon, nitrogen and phosphorus in a secondary forest in a montane region of eastern Liaoning Province, China.

XIAO Jian-qiang1,2,3, ZHANG Wei-wei1,2,3, YU Li-zhong1,2, YANG Kai1,2*

2017, 36(11):  3043-3048. 

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Gap disturbance plays an important role in the processes of regeneration and succession of secondary forests, and influences the capability of soil nutrient supply. To indicate the effects of gap size on the processes of nutrient cycling in soil, we measured soil microbial biomass carbon, nitrogen and phosphorus during the peak growing season at the 0-20 cm depth in large, medium and small gaps (90-670 m²) formed 6 years ago in the  secondary forest in a montane region of eastern Liaoning Province, China. The results showed that compared with the control soil (i.e., the soil in the understory), there were no significant differences in microbial biomass carbon, microbial biomass phosphorus, the ratios of microbial biomass carbon to total carbon and microbial biomass phosphorus to total phosphorus in the three sizes of gaps at the soil depths of 0-10 and 10-20 cm. In addition, there were also no significant differences in microbial biomass carbon, nitrogen, phosphorus, the ratios of microbial biomass carbon to total carbon, microbial biomass nitrogen to total nitrogen and microbial biomass phosphorus to total phosphorus among the three gap sizes. In comparison with the control soil, microbial biomass nitrogen and the ratio of microbial biomass nitrogen to total nitrogen were significantly higher in the medium gaps with the size of 290 m² in the 10-20 cm soil layer, indicating the increase of cycling and availability of soil nitrogen in the medium gaps.

Decomposition of mixed leaf litter of Larix kaempferi plantation in eastern montane region of Liaoning Province.

LI Ying-hua1,2,3, ZHOU Li1,3*, WU Jian1,2,3, ZHOU Wang-ming1,3, DAI Li-min1,3, LU Zheng-mao4, HUANG Li-ya5

2017, 36(11):  3049-3055. 

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Nutrient release of leaf litter decomposition plays an important role in sustainable maintenance of soil quality, nutrient balance and plant productivity. In the present study, we investigated the response of leaf litter mixture decomposition rate and nutrient dynamics of Larix kaempferi-Pinus koraiensis mixed plantation and Larix kaempferi-Alnus japonica mixed plantation to three mixing ratios (75∶25, 50∶50, 25∶75) by using litter bag method in May 2015. The results indicated that A. japonica had the highest mass loss, while P. koraiensis had the lowest when considering the decomposition of singlespecies litter. The mixture of L. kaempferi and A. japonica at the 3 mixing ratios had an antagonistic effect on N release, but the leaf litter mixture of 25% L. kaempferi and 75% P. koraiensis showed a promoting effect on N release. Therefore, the leaf litter mixtures of L. kaempferi+A. japonica and L. kaempferi+P. koraiensis showed nonadditive effects, and the N and P releases were influenced by mixing ratios during decomposition.

Effects of understory removal on soil enzyme activities in a Pinus sylvestris var. mongolica plantation in Horqin Sandy Land.

ZHENG Lin-lin1,2, ZHAO Qiong1*, ZENG De-hui1

2017, 36(11):  3056-3063. 

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Understory vegetation is an important component of forest ecosystems, which plays an important role in ecosystem nutrient cycling. The effects of understory removal on soil microbial biomass, activities of enzymes catalyzing organic carbon (C), nitrogen (N), and phosphorus (P), and available N and P concentrations were examined in a nutrientpoor Pinus sylvestris var. mongolica plantation in Horqin Sandy Land. Understory removal significantly decreased microbial biomass C and P, available P concentrations, as well as all measured enzyme activities in summer (August), but only decreased N-acetylβ-Dglucosidase activity and did not influence microbial biomass, available nutrient concentrations and activities of other enzymes in spring (May). These results suggested that preservation of understory vegetation could effectively improve soil microbial activity and accelerate mineralization of organic C, N and P, and thus maintain the nutrient supply in this nutrientpoor pine plantation.

Soil CO₂ efflux during nongrowing season in a Korean larch (Larix olgensis Henry) plantation in mountainous area in eastern Liaoning Province.

YOU Wen-zhong1, WEI Wen-jun2*, ZHANG Hui-dong2, WANG Rui-zhao2, YAN Ting-wu2, MAO Yi-xin2

2017, 36(11):  3064-3071. 

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The mountainous areas of eastern Liaoning Province have a long and cold winter with deep snow cover. At the beginning and end of the nongrowing season in late autumn and early spring, however, topsoil undergoes repeated freezethaw cycles and soil CO₂ emission during these periods can be important in annual carbon budget. In this study, we set up three 20 m × 30 m plots in a Korean larch (Larix olgensis Henry) plantation, a common forest type in eastern Liaoning Province, and measured soil respiration (R_s) to quantify CO₂ emission (F_CO2) during the periods of freezethaw cycles in late autumn and early spring. Four polyvinyl chloride (PVC) collars were installed in each plot and R_s was measured, 2-3 times a month for 4 winters (2010-2014), using portable CO₂ infrared gas analyzer (Li-8100). The results showed a “U” change of R_s in nongrowing season from late autumn to early spring. R_s was positively correlated with soil temperature at 10 cm depth (T₁₀) and air temperature (T_a) and the relationship was best fitted with an exponential model. The fitted relationships were stronger in late autumn than in early spring and in 2010/2011 and 2011/2012 winters than in 2012/2013 and 2013/2014 winters. R_s varied substantially among years from (0.42±0.02) to (0.72±0.04)  μmol CO₂·m^-2·s^-1 by nongrowing season averages and the total F_CO2 in nongrowing season was 137, 92, 100 and 159 g C·m^-2 for the 4 study winters, respectively. Within a nongrowing season, the F_CO2 in late autumn ranged from 29.66 to 63.48 g C·m^-2 in the 4 years, about 0.68-3.36 times greater than that in early spring. The overall contribution of F_CO2 in the two freezethaw periods in late autumn and early spring to the total F_CO2 in the nongrowing season ranged from 47.69% to 54.66% across the 4 study winters. The acceleration capacity of soil CO₂ release of freezethaw cycles during the alternation of autumn to winter was stronger than that during alternation of winter to spring. These results help understand the patterns of forest soil carbon emission during non-growing season in northeastern China.

Effects of ectomycorrhizal fungi on physiological indexes of Pinus sylvestris var. mongolica seedlings and soil enzyme activities under cadmium stress.

YIN Da-chuan1*, DENG Xun2, SONG Xiao-shuang2, QI Jin-yu1

2017, 36(11):  3072-3978. 

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A pot experiment was conducted to study the effects of different cadmium (Cd) concentrations on growth and physiological traits, chlorophyll contents, activities of antioxidant enzyme (CAT, POD and SOD), contents of osmotic adjustment substances (soluble sugar, MDA and free proline), and activity of rhizosphere soil enzymes of Pinus sylvestris var. mongolica by inoculating ectomycorrhizal fungus Suillus luteus. The results showed that after 1 month Cd stress treatment on 1-year-old P. sylvestris var. mongolica seedlings, the seedling growth and the antioxidant enzyme activities in inoculated group were higher than those in uninoculated group, and most of the indicators investigated reached significant difference levels (P<0.05). CAT and POD activities declined and then increased with the increase of Cd concentration, while SOD activity showed a symmetrical pattern between the aboveground and underground parts. Meanwhile, the determination of seedling cell osmotic regulation substances showed that the cell damage degree of inoculated group was lower than that of uninoculated group. The results indicated that inoculating ectomycorrhizal fungi could help relieve the stress of Cd of P. sylvestris var. mongolica seedlings. Under Cd stress, ectomycorrhizal fungi can effectively improve rhizosphere soil enzyme activity of P. sylvestris var. mongolica seedlings (especially the urease), and further improve the tolerance of P. sylvestris var. mongolica seedlings to heavy metal. The results can provide reference for phytoremediation of heavy metal polluted soils using woody plants.

The responses of chlorophyll fluorescence kinetics parameters of six tree species to soil moisture changes.

ZHANG Guo-sheng1*, HAO Lei1, YAN Zi-juan1, ZHAO Xin1, WANG Ying3, BAI Yu-rong2, LI Xiao-long4

2017, 36(11):  3079-3085. 

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To assess the responses of leaf chlorophyll fluorescence kinetics parameters to soil water stress, the diurnal variation of leaf chlorophyll fluorescence kinetics parameters of six sandfixation tree species (Salix psammophila C. Wang et Ch.Y. Yang, Salix gordejevii Y.L. Chang et Skv., Elaeagnus angustifolia L., Ampelopsis aconitifolia var. glabra Diels, Amorpha fruticosa L., and Ammopiptanthus mongolicus (Maxim. ex Kom.) S.H. Cheng) were determined with a portable modulated chlorophyll fluorescence spectrometer (Mini-PAM) in the growing season in 2015. The results showed that the diurnal variations of quantum yield (Yield), the apparent photosynthetic electron transport rate (ETR), the maximum photochemical efficiency of PSⅡ (F_v/F_m) and nonphotochemical quenching (NPQ) were obviously of singlepeak curve. Yield, ETR and F_v/F_m decreased with the decrease of soil water, while NPQ increased. These results indicated that the chlorophyll fluorescence kinetics parameters could be used as evaluation indicators of resistance. The response of F_v/F_m was most sensitive to the change of soil moisture. The sensitivity of F_v/F_m to soil moisture for the six tree species ranked in the order of Ammopiptanthus mongolicus > Salix psammophila > Salix gordejevii > Ampelopsis aconitifolia > Amorpha fruticose > Elaeagnus angustifolia. In conclusion, xerophilous tree species was most sensitive to soil moisture change, followed by mesophilous and hygrophilous tree species.

Vegetation change in relation to soil microbes, enzyme activity and soil fertility in the tundra of Changbai Mountain.

ZHANG Ying-jie1, JIN Ying-hua1*, GU Xiao-nan1, XU Jia-wei1, TAO Yan1, HE Hong-shi1,2, WANG Ai-lin1, LIU Yu-xia1, NIU Li-ping1

2017, 36(11):  3086-3093. 

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Herbaceous plants have encroached into tundra area of Changbai Mountain under warming climate, which has severely changed the tundra vegetation. We analyzed soil microbes, soil enzyme activity and soil fertility at different stages of herbaceous encroachment. We also analyzed subsequent changes of soil microbial community structure and enzyme activity and the effects of soil microbial community structure and enzyme activity on soil fertility as well as the effects of changes in soil fertility on vegetation changes. Results showed that: (1) Soil microbes and soil enzyme activity changed as the vegetation changed. Among these changes, soil microbial PLFAs and enzyme activity continued to increase with the level of herbaceous encroachment. However, soil microbial PLFAs and enzyme activity decreased when the herbaceous plants dominated the plant communities. (2) The decomposition of soil organic matter was accelerated and the available nutrients increased with the increase of soil microbial PLFAs and enzyme activity under high level of herbaceous encroachment. (3) A transformation process from positive feedback to negative feedback occurred between soil microbes, enzyme activity and the level of herbaceous encroachment. Therefore, the changes of soil microbes and enzyme activity significantly affected herbaceous plant encroachment of the tundra vegetation of Changbai Mountain.

Dynamic changes of soil microbial biomass in different restoration periods of Daxing’anling after fire disturbance.

SUN Long, WU Guang-yuan, HU Tong-xin*

2017, 36(11):  3094-3101. 

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Wildfire is an important disturbance factor of the boreal forest ecosystem of China. With global warming, wildfire disturbance is much more serious. In this paper, the dynamic changes of soil microbial biomass carbon and nitrogen were measured at three different restoration stages of Dahurian larch (Larix gmelinii) forests after severe fire disturbance in the Daxing’an Mountains. The results indicated that the soil microbial biomass carbon and nitrogen increased at the beginning of the growing season and then decreased until the end of the growing season, and the microbial biomass carbon and nitrogen were higher in upper layer soil than in lower layer soil. The soil microbial biomass nitrogen in the plots 3 and 28 years after fire disturbance was higher than that in control plots, and vice versa in plots 9 years after fire disturbance. The soil microbial biomass carbon in plots 3 years after fire disturbance was lower than that in control plots, and vice versa in plots 9 and 28 years after fire disturbance. The soil microbial biomass carbon and nitrogen reached the maximum value in June and then decreased until the end of the growing season. There was a significant negative correlation between the soil microbial biomass carbon and phosphorus in upper layer in plots 9 years after fire disturbance. The soil microbial biomass nitrogen was negatively correlated with the soil water content in lower layer in plots 9 years after fire disturbance. The results of this study will provide a reference for assessing soil microbial biomass nitrogen and carbon and its impact factors after fire disturbance in boreal forest of China.

Scale-dependent spatial variation of species diversity in typical vegetation types in Changbai Mountain, China.

CAO Lin-lin1,2,3, SU Bao-ling1, ZHOU Wang-ming2,3, YU Da-pao2,3, WU Jian2,3, BI Jian-hua1,2,3, HUANG Li-ya4, DAI Li-min2,3*

2017, 36(11):  3102-3108. 

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Spatial distribution pattern and scale-dependent spatial variation of species diversity index are of great importance to reveal formation and maintenance mechanism of species diversity. We selected the broadleaved Korean pine forest (BKPF), natural secondary birch forest (BF) and artificial larch forest (LF) after logging in Changbai Mountain as the research objects and used variance and coefficient of variation to explore the scale-dependent spatial variation of species abundance and richness in Changbai Mountain. The results showed that: (1) the variance of species abundance increased linearly with spatial scale, while the coefficient of variance decreased with spatial scale in BKPF and LF. The variance of species richness showed a unimodal variation, reaching the maximum at the 20 m×20 m scale in BKPF and LF. It is indicated that large-scale species abundance can be estimated from smaller scales, whereas richness cannot be estimated. (2) The variance and coefficient of variance of species abundance in BF were consistent with those in BKPF, while the variation of species richness increased as the scale increased and never showed a unimodal variation. It was due to the significant increase in the aggregation degree of major tree species in BF. (3) The species abundance and richness had significant correlation each other on the small scale for all the three plots, but the correlation was no longer significant as the scale increased. Our results revealed the scale-dependent spatial variation and its reasons of species diversity of typical vegetation types in Changbai Mountain, providing data support for restoration and management of the broad-leaved Korean pine forest.

Ecological stoichiometry of different forest types in mountainous region of eastern Liao-ning Province.

BI Jian-hua1,2,3, SU Bao-ling1, YU Da-pao2,3, WU Jian2,3, CAO Lin-lin1,2,3, DAI Li-min2,3, ZHOU Li2,3*

2017, 36(11):  3109-3115. 

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Stoichiometry plays an important role in elucidating the supply status and relationship of nutrient elements in ecosystems and in revealing the limiting factors that affect forest structure and function. The present study selected natural broadleaved mixed forest, Quercus mongolica forest, Pinus tabuliformis forest, Larix gemelinii plantation, and Pinus koraiensis plantation and investigated ecological stoichiometry characteristics and their difference among different forest types, through measuring the contents of carbon (C), nitrogen (N) and phosphorus (P) in leaves, litter, and soil. Our results showed that (1) the contents of C, N and P differed significantly among the five forest types, and those in leaves and litter were consistently higher than in the soil. In particular, N content was the highest in the natural broadleaved mixed forest and lowest in the Q. mongolica forest. (2) The rank of the C∶N and C∶P in the five forest types was litter>leaf>soil, while N∶P was leaf>litter>soil. The mean of leaf N∶P was 12.16, indicating that the growth of plants in this area might be limited by N. (3) The correlations in N, P, C∶N and N∶P were positively associated between leaves and litter, while N and C∶N in both leaves and litter were negatively correlated with those in the soil. These results suggest that the understanding of stoichiometry characteristics of nutrients in “plantlittersoil” is essential to reveal the nutrient status and the biochemical cycle of forest ecosystems.

Effects of drought stress on N and P stoichiometry and allocation of poplar seedlings.

WANG Kai1*, LI Yi-hang1, JIANG Tao2, YAO Hong-jia1, ZHAN Shu-ting1

2017, 36(11):  3116-3122. 

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To understand the effects of drought stress on N and P stoichiometry in different organs of poplar seedlings, one-year-old Populus × xiaozhuanica cv. Zhangwu seedlings were grown under suitable water level, mild, moderate and serious water stress treatments, i.e., 80%, 60%, 50% and 40% of field capacity, with water controlling method in pots. The results showed that compared with the suitable water level treatment, with the increase of drought stress time, N content firstly declined and then increased in leaves, while it firstly decreased and then had no difference with the suitable water treatment in stems, and declined in roots in the drought stress treatments. P content firstly decreased and then increased in leaves and stems, and increased in roots in the drought stress treatments. However, N/P firstly elevated and then declined in leaves and stems, and decreased in roots in drought stress treatments. There were significant correlations among roots, stems, and leaves in N or P content (P<0.05), while N content was not correlated with P content in all organs (P>0.05). N content of different organs followed the order: leaves>stems and roots, but there was no significant difference in P content among different organs. Meanwhile, the coefficients of variation for N content and N/P followed the order: roots>stems>leaves, but the coefficient of variation for P content was similar in different organs. These results indicated that with the increase of drought stress, N limitation for poplar seedlings was enhanced. The variation degree of N was smaller than that of P in leaves and stems, but the variations of N and P were similar in roots under drought stress.

Quantitative characteristics and dynamic analysis of the endangered species Rhododendron chrysanthum population in Changbai Mountain.

JIN Hui, ZHAO Ying, YIN Hang*, QIN Li-wu, LIU Li-jie, WANG Chao, JIA Xiang, LI Bing-yan

2017, 36(11):  3123-3130. 

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Rhododendron chrysanthum is listed as one of the national protected plants at third category in Chinese Plant Red Book. Its population size is very small, being on the verge of extinction. Based on the methods of population static life table, survival curve, and individual amount dynamic prediction, the quantitative characteristics and dynamic trend of R. chrysanthum population at different altitudes of alpine tundra in Changbai Mountain were studied. The results were as follows: (1) The spindleshaped size class structure suggested that R. chrysanthum population exhibited a declined pattern. (2) The growth potential of population decreased gradually with the rising altitude. Under incomplete random disturbance, the growth potential of the population was limited, and the V_pi″ of low altitude was close to 0. (3) The survival curve of population exhibited as the DeeveyⅢ type, which had higher death rate and lethal force with obvious degradation at the higher altitude. (4) After 1, 2, and 4 age classes, the individual number at age class 4 would increase to varying degree. The individual number was supplemented in the later growth stage. (5) The population size of R. chrysanthum was maintained mainly by ramets reproducing from reptant roots. The possible factors leading to the species being endangered might be its biological characteristics and the disturbances from human activities.

Response of radial growth of Picea jezoensis var. komarovii to climate factors along an altitudinal gradient on Changbai Mountain, Northeast China.

WANG Shou-le1,2, ZHAO Yuan1,2, GAI Xue-rui1,2, WANG Xiao-yu1,2, YU Da-pao1*, ZHOU Wang-ming1, ZHOU Li1, DAI Li-min1

2017, 36(11):  3131-3137. 

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In order to clarify the stability of the tree growth response to the climate and its elevation difference, this study dendrochronologically developed chronologies of spruce (Picea jezoensis var. komarovii) growing at the elevation of 1200 m (low), 1400 m (middle) and 1600 m (high) on the northern slope of Changbai Mountain, and then explored the relationship of radial growth and climate and its dynamics. The results showed that spruce generally had a low climate sensitivity (0.12-0.16). Comparatively, spruce at low altitude had higher climate sensitivity. The radial growth of spruce was significantly positively correlated with mean maximum temperature in May at the three elevations. Additionally, spruce at middle and low elevations was significantly negatively correlated with the precipitation in May. However, the correlation between spruce’s radial growth and the climate was not stable. Since 1986, mean maximum temperature in May displays a decreasing trend, which made the correlation between spruce’s growth and climate decline. The breakpoints of correlation coefficients from significant to nonsignificant occurred at 11.8 (mean temperature in May) and 19.9 ℃ (mean maximum temperature in May), respectively. The increased correlation between growth and climate was mainly affected by the increasing precipitation in May in recent years, and the breakpoint occurred at 72.2 mm. This study provides a reference date for climate reconstruction and the prediction of spruce’s growth under climate change.

Dynamics of forest landscape pattern in Changbai Mountain.

WANG Mei-ling1,2, ZHANG Ji-chao1, WANG Bo-jian2,3, WANG Shi-yang2,3, HAO Zhan-qing2, WANG Xu-gao2*

2017, 36(11):  3138-3147. 

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Based on Landsat remote sensing image data in 2004 and 2015, we analyzed the changes in spatial distribution, shape, landscape fragmentation and diversity of Changbai Mountain National Nature Reserve and four neighboring forestry bureaus. The results showed that landscape changes did not always differ between the reserve and the neighboring forestry bureaus. The shape of forest landscapes became more regular, and the coniferous forest area decreased, which was mostly converted to broadleaved mixed forest areas from 2004 to 2015 in both the reserve and its neighboring forestry bureaus. The total forest area in the reserve was almost unchanged, while the forest area in the forestry bureaus was reduced by 7326 hm², which was mostly converted to cultivated lands, followed by bare, harvested and construction lands. Generally, the landscapes in the study area tended to become more fragmented, heterogeneous, and diverse from 2004 to 2015, which indicated strong effect of human disturbances. In addition, the landscape changes varied among the four forestry bureaus. For instance, the shape of forest landscapes in Baihe Forestry Bureau became more regular, and the degree of fragmentations decreased, while the other forestry bureaus, such as Quanyang and Songjianghe showed the opposite trend.

Effects of soil nutrients on seedling growth of major tree species in montane region of eastern Liaoning Province, China.

WANG Jing1,2,3, XU Shuang1,2, YAN Tao1,2,3, MA Wei-juan4, YAN Qiao-ling1,2*

2017, 36(11):  3148-3159. 

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A key to solve the problems about coniferous plantation degradation in montane regions of eastern Liaoning Province is to convert pure coniferous plantations into mixed coniferbroadleaf forests or promote the natural regeneration of broadleaved tree species in coniferous plantations. Seedling growth, a period of tree regeneration sensitive to environmental changes, is a crucial process to determine either the success or failure of plant regeneration. Moreover, soil nutrient is a dominant factor to ensure seedling growth. We took the seedlings of three dominant tree species including Juglans mandshurica, Fraxinus rhynchophylla and Quercus mongolica as the research objects to explore: (1) the effect of soil (from larch plantation, Korean pine plantation and secondary forest) on seedling growth, and (2) the relationship between seedling growth and soil nutrients. The results showed that the differences of soil nutrient in the three forest types had no obvious effect on seedling biomass for J. mandshurica and Q. mongolica, and there were no significant correlations between nutrient contents in seedlings and soil nutrients (P>0.05). In contrast, there were positive correlations between soil nutrient and seedling biomass allocation and nutrient contents in root, stem and leaf for Q. mongolica and F. rhynchophylla (P<0.05). Based on the N/P ratios in the leaves of seedlings, the growth of J. mandshurica seedling was likely to be restricted by the N content in the soil of secondary forest (N/P=10.7) and pine plantation (N/P=11.6). However, the growth of F. rhynchophylla seedling was possibly restricted by the P content in the soil of secondary forest (N/P=25.0) and larch plantation (N/P=19.4), and the growth of Q. mongolica seedling was not restricted by N or P in the three studied forest soils. All of these results indicated that the seedling growth of Q. mongolica and F. rhynchophylla was more sensitive to the dynamics of soil N and P contents than that of J. mandshurica grown in the soil of coniferous plantations. In future, more attention should be paid to other factors such as light and temperature, which may affect the seedling growth of broadleaved tree species in the coniferous plantations.

Leaf age-related changes in photosynthesis of Quercus mongolica leaves in relation to leaf functional traits.

CUI Xi-tian1,2, YUAN Feng-hui1*, WANG An-zhi1, GUAN De-xin1, WU Jia-bing1, JIN Chang-jie1

2017, 36(11):  3160-3167. 

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Photosynthetic capacity directly determines the productive capacity of plant, and it is often affected by intrinsic factors of leaves and environmental conditions. In this study, following the day scale of leaf age, the changes of photosynthetic parameters of Quercus mongolica with leaf age and  their relationships with leaf functional traits from leaf budding were analyzed. We found that during the first few days after leaf budbreak, leaf respiration rate of Q. mongolica was higher than photosynthetic rate, hence the value of net photosynthetic rate was negative. The maximum net photosynthetic rate (P_max), the maximum net photosynthetic rate when CO₂ was saturated (J_max), and the maximum Rubisco catalytic reaction rate (V_cmax) were influenced more greatly by environmental factors (precipitation, soil moisture) during the middlegrowth period than in other periods. During the whole early growth season, the correlations among photosynthetic parameters and chlorophyll content and leaf area were extremely significantly positive (P<0.01), while the relationships between photosynthetic parameters and specific leaf weight were negatively correlated in leaf budding period of the early growth season, positively correlated in leafexpansion period of the early growth season, and negatively correlated after leaf fully expanded in the early growth season. In the middlegrowth season, there was no significant correlation between photosynthetic parameters and leaf functional traits. At the end of the growth season, the correlations between photosynthetic parameters and functional traits were markedly positive (P<0.05). Our study indicated that it was necessary to differentiate leaf photosynthetic capacities and their physiological and biochemical mechanisms following different growth stages or periods.

Responses of non-structural carbohydrates accumulation and distribution of Caragana microphylla seedlings to drought stress.

LEI Hong1, WANG Kai1*, TIAN Hao1, GAO Xiang1, ZHAO Li-ren2

2017, 36(11):  3168-3175. 

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To understand the response of nonstructural carbohydrates (NSC) to drought stress, two-year-old Caragana microphylla seedlings were planted in four different water treatments (suitable water level, mild, moderate and serious drought stress, i.e., 80%, 60%, 40% and 20% of field waterholding capacity) for 15, 30, 45 and 60 days. The results showed that there were significant interacting effect between drought stress degree and duration on the contents of soluble sugar, starch and total NSC of leaves, stems, coarse and fine roots of C. microphylla seedlings. Under mild drought stress, the soluble sugar, starch and total NSC contents in each organ were significantly lower than those under suitable water level on the 30th day of treatment. Moreover, the soluble sugar content in fine roots and starch content in coarse roots were significantly higher than those under suitable water level on the 60th day of treatment. Under moderate drought stress, the soluble sugar content in stems and coarse roots was firstly significantly lower than that under suitable water level, and then it gradually increased. Meanwhile, compared with mild drought stress, the soluble sugar content in leaves, stems and fine roots increased while the starch content in stems and coarse roots decreased under moderate drought stress. Under serious drought stress, the starch content in each organ was significantly lower than that under suitable water level on the 15th day of treatment, and it was significantly higher than that under suitable water level on the 60th day of treatment. These results indicated that C. microphylla seedlings adapted to different drought environments by adjusting accumulation and distribution of NSC contents in different organs.

Adaptive strategies of adult Platycladus orientalis and Robinia pseudoacacia to spring drought.

WANG Kai*, ZHAO Cheng-jiao, DENG Jie, ZHANG Ying, GAO Shuang

2017, 36(11):  3176-3181. 

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In the present study, the effects of spring drought stress on morphology and physiological characteristics of leaves and roots of mature Platycladus orientalis and Robinia pseudoacacia were analyzed and the adaptive strategies of the two tree species under drought stress were compared. The results showed that the proline and soluble protein contents, and SOD and POD activities in leaves of P. orientalis were significantly lower than those in leaves of R. pseudoacacia (P<0.05), but the soluble sugar content and CAT activity in leaves of P. orientalis were significantly higher than those in leaves of R. pseudoacacia under spring drought stress (P<0.05). Meanwhile, the difference in malondialdehyde content in leaves was not significant between P. orientalis and R. pseudoacacia (P>0.05). The proline and soluble protein contents, and POD and CAT activities in roots of P. orientalis were significantly lower than those in roots of R. pseudoacacia (P<0.05). However, the soluble sugar and malondialdehyde contents in roots of P. orientalis were significantly higher than those in roots of R. pseudoacacia (P<0.05). The specific leaf weight and root activity of P. orientalis were significantly higher than those of R. pseudoacacia (P<0.05). The root length density and root area index of R. pseudoacacia were significantly greater than those of P. orientalis(P<0.05). These results indicated that there were differences in permeating substance contents and antioxidative enzyme activities between P. orientalis and R. pseudoacacia under spring drought stress. The damages of spring drought to leaves were similar between P. orientalis and R. pseudoacacia, but the damages were more severe to the roots of P. orientalis. Adult P. orientalis mainly adopted droughttolerance strategies, while mature R. Pseudoacacia mainly adopted droughtavoidance strategies under spring drought.

Characteristics of sap flow and its influencing factors of Pinus sylvestris var. mongolica in sandy land of Northwest Liaoning.

LU Zhi-peng1,2, WEI Ya-wei1,2, LI Zhi-yuan1,2, GUO Xin-wei1,2, ZHOU Yong-bin1,2*

2017, 36(11):  3182-3189. 

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Sap flow is a basic indicator to quantify plant transpiration water consumption. In this study, a continuous sap flow observation of Pinus sylvestris var. mongolica in a semiarid area of northwestern Liaoning was carried out by using the FLGS-TDP thermal dissipation sap flow probe from May to October in 2015, and the microclimate in the forest was recorded simultaneously. On the basis, the dynamic characteristics of the sap flow of Pinus sylvestris var. mongolica and its influencing factors were studied. Results showed that during the growing season, the sap flow rate of Pinus sylvestris var. mongolica varied with weather conditions, both the sap flow rate and its daily cumulative volume were decreased in the sequence of sunny > cloudy > rainy. The trend of sap flow rate followed reversed "U", and there was a phenomenon of "midday depression of photosynthesis" in sunny day. From May to October, both trunk sap flow rate and monthly accumulation amounts decreased as follows: July > June > August > May > September > October. With respect to the season dynamics, the starting hour of the trunk flow in summer was about an hour earlier than that in autumn; moreover, the trunk sap flow rate was higher in summer than in autumn. In addition, the sap flow was affected significantly by meteorological factors, in which the active radiation light, air temperature, saturated vapor pressure deficit and wind speed all affected sap flow positively, while the air humidity influenced sap flow negatively. The effects of soil temperature and humidity on the sap flow changed with time (month), weather conditions (cloudy, sunny and rainy) and soil depths (5, 10, 20, 40 and 100 cm). For example, there were significantly positive correlations between the temperature of surface soil (0-10 cm) and the sap flow (unit based on day or month) during the growing season, while there were significantly negative correlations between the temperature of deep soil (20-100 cm) and the sap flow. In addition, the sap flow increased significantly with the increase of soil moisture in May and October, while decreased remarkably with the increase of soil moisture during the growing season from June to September.

Responses of Juniperus sabina and Pinus sylvestris var. mongolica seedlings to shading in low nutrient conditions.

MENG Peng*

2017, 36(11):  3190-3198. 

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To determine the effects of shade on survival rate, relative growth rate (RGR), biomass allocation and photosynthesis characteristics, potted seedlings of shadetolerant Juniperus sabina and shadeintolerant Pinus sylvestris var. mongolica in lownutrient substrate were grown without shade or under a 35%, 65% or 95% reduction of full sunlight over two growing seasons. The results showed that, with decreased light availability, J. sabina growth and survival did not change significantly. Total biomass and RGR increased and then decreased; RGR indicators were positive; and the shoot/root ratio increased significantly. In contrast, the survival rate and growth of P. sylvestris var. mongolica decreased significantly. Total biomass and RGR decreased; the RGR was negative under 95% shade; and the shoot/root ratio decreased significantly. The maximum photochemical efficiency (F_v/F_m) of J. sabina was more sensitive to shade and increased significantly under 35% shade, while the F_v/F_m of P. sylvestris var. mongolica increased significantly until 65% shade. A JIPtest showed that the standardized fluorescence values (V_t) of J. sabina under shade were lower than those under the nonshading treatment (CK) from initial O phase to final P phase. Furthermore, the proportion of electron energy across the Q_A reaction center to the whole energy captured (ψ_o), quantum yield of electron transfer (ψ_Eo), size of plastoquinone pool (S_m), plastoquinone pool reduction rate (S_m/T_fm), number of reduced primary quinone acceptors (N), and energy for electron transfer per excited crosssection (ET_o/CS_o) all increased. The density of reaction centers (RC/CS_o) increased, while dissipation per excited crosssection (DI_o/CS_o) and per reaction center (DI_o/RC) decreased, leading to significantly higher performance indexes (PI_ABS, PI_CSo, PI_CSm) under shade than under CK. The V_t of P. sylvestris var. mongolica under shade was higher than under CK from O phase to P phase; however, the above fluorescence parameters were lower or were not significantly different under shade except for the heat dissipation indexes. DI_o/RC remained unchanged in P. sylvestris var. mongolica under shade, and the performance indexes (PI_ABS, PI_CSo and PI_CSm) also remained unchanged. The above results indicated that J. sabina was able to maintain high growth and survival under low light intensity by maintaining a positive carbon balance and increasing the proportion of aboveground biomass and electron transfer energy levels during the lightreaction stage. In contrast, P. sylvestris var. mongolica had a low survival rate due to a carbon budget imbalance, and the decreases in proportion of aboveground biomass and electron transfer energy level under shading conditions.

Community composition characteristics of wood-decaying fungi in temperate secondary forest ecosystems in China.

LI Tong1, 2, LI Jun-ning1, 2, WEI Yu-lian1*

2017, 36(11):  3199-3208. 

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Wood-decaying fungi, an important group in forest ecosystems, can utilize wood matrix for organism growth and play an important role in nutrient cycling in the forest ecosystems. In order to understand the community composition of wooddecaying fungi in temperate secondary forest ecosystems, four representative secondary forest ecosystems were selected in this study, e.g. Changbai Mountain secondary poplarbirch forest in Jilin Province, Baishilazi Nature Reserve in Liaoning Province, Dongling Mountains Nature Reserve in Beijing, and Baotianman Nature Reserve in Henan Province. Based on field investigations and laboratory analysis, fungal flora and diversity composition of wooddecaying fungi from the four sites were analyzed. In total, 73 wooddecaying fungal species were found in Changbai Mountain secondary poplarbirch forest, 104 species in Baishilazi Nature Reserve, 106 species in Dongling Mountain Nature Reserve and 124 species in Baotianman Nature Reserve. There were 18 common species among the four sites. Each site had its dominant fungal genera: Phellinus was in Changbai Mountain secondary poplarbirch with seven species, Trametes was in Baishilazi Nature Reserve with seven species, Hymenochaete was in Dongling Mountain Nature Reserve with nine species and Polyporus was in Baotianman Nature Reserve with ten species. Comparison of the rarefaction curves of the fungi from the different sites showed that the dominant species of each site had positive relationship with their dominant hosts. And the composition of the tree species played a key role in the composition of the wooddecaying fungi. The genera geographical elements of polypores were dominated by cosmopolitan element and the North Temperate element, with a distinct North Temperate character.

Community characters of wood-decaying fungi on dominant hosts in the broad-leaved Korean pine mixed forest in Changbai Mountain.

WEI Yu-lian1*, LI Tong1,2

2017, 36(11):  3209-3215. 

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Wood-decaying fungi are an important component of forest ecosystems; they can decompose the dead wood and play a key role in the nutrient cycle of the ecosystem. The broadleaved Korean pine mixed forest in Changbai Mountain harbors complex structure and multiplex plants and provides rich substrates for wood-decaying fungi. To understand the effect of the host plants on wooddecaying fungi, 325 subplots, each with 20 m × 20 m, were selected in the Changbai Mountain Plot (the CBS plot). Every fungal individual in the subplots was recorded and identified, and the statistic analyses of wood-decaying fungi collected from four dominant hosts were done, including Acer, Quercus, Tilia and Pinus. The results showed that the fungi on the four hosts comprised 86.6% of all individuals and 95.3% of all species in the subplots. The discrepancy of the fungal species on different hosts was clearly observed. The Venn diagram showed that only seven species were common on the four hosts. The distinct species on different hosts accounted for >25% of their respective fungal composition. Moreover, the decaying degree and the diameter of dead wood also influenced the fungal community. The highest fungal diversity was observed on the wood with large diameter (>10 cm) and in the decaying degree 2.

Spatiotemporal variation of water yield and its driving factors in Northeast China.

WU Jian1,2,3, LI Ying-hua1,2,3, Huang Li-ya4, LU Zheng-mao5, YU Da-pao1,3, ZHOU Li1,3, DAI Li-min1,3*

2017, 36(11):  3216-3223. 

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Land use change across Northeast China experienced a significant spatiotemporal variation between 1990 and 2010. Northeast China is one of the most sensitive regions to global climate change. A better understanding of the effects of land use change and climate change on water yield is of great importance to water resource planning and sustainable management. Based on the land use data in 1990, 2000, and 2010, meteorological data, and soil data, InVEST model was used to analyze the spatiotemporal changes in water yield in Northeast China from 1990 to 2010. Structural equations were used to explore the influence of climate change and land use change on water yield in Northeast China. The results showed that the water yield in Northeast China had a trend of increase after an initial decrease in the 20 years. In addition, montane regions of Eastern Liaoning Province and Changbai Mountain area had the highest water yield, while the plain area had the least water yield. The precipitation was estimated to be the main factor leading to the spatiotemporal variation of water yield in Northeast China, while temperature and land use change had a minor influence on water yield.

Spatiotemporal change characteristics of extreme temperature indices in Jilin Province during 1961-2015.

REN Jing-quan1, GUO Chun-ming1*, LIU Yu-xi2, MU Jia1, LI Jian-ping1, LI Qi3

2017, 36(11):  3224-3234. 

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Based on the data of 50 meteorological stations in Jilin Province during 1961-2015, the variations of extreme temperature indices were analyzed. The result showed that warm days, warm nights, frost days, warm spell duration days, daily temperature range, annual maximum value of daily maximum and minimum increased from west to east in Jilin Province. Summer days, warm nights and cold duration spell days decreased from west to east, while ice days increased from south to north. Cold days, cold nights, frost days, cold spell duration days and daily temperature range were found to decrease significantly by 0.75 d·10 a^-1, 2.34 d·10 a^-1, 3.15 d·10 a^-1, 1.67 d·10 a^-1 and 0.23 ℃·10 a^-1 respectively; warm days, warm nights, summer days, hot nights, annual maximum value of daily minimum, annual minimum value of daily maximum, warm spell duration days and growing season length showed statistically significant increasing trends at rates of 0.76 d·10 a^-1, 1.55 d·10 a^-1, 2.34 d·10 a^-1, 1.62 d·10 a^-1, 0.16 ℃·10 a^-1, 0.57 ℃·10 a^-1, 0.80 d·10 a^-1 and 3.22 d·10 a^-1 respectively. It was found that the most extreme temperature indices had an abrupt change in the 1980s, the cold indices decreased and warm indices increased after the change. The main period of the most extreme temperature indices was 3 years. When the longitude increased by 1 degree, the cold spell duration days, summer days, and hot nights decreased by 0.2, 5.2 and 2.3 d, respectively. When the latitude increased by 1 degree, the cold spell duration days, ice days, summer days, warm nights, annual maximum value of daily maximum, annual maximum value of daily minimum increased by 0.5 d, 4.2 d, 5.3 d, 2.3 d, 0.7 ℃, 0.5 ℃, respectively. When the altitude increased by 100 m, the cold spell duration days, growing season length, summer days, and hot nights decreased by 0.4, 1.8, 5.8, 2.9 d, respectively.

Dynamic characteristics of different grade precipitation events during past 45 years in Daxing’anling forest region, Inner Mongolia.

WANG Bing1, BIAN Yu-ming1, ZHANG Qiu-liang1*, DAI Hai-yan2

2017, 36(11):  3235-3242. 

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Based on the daily precipitation observation data of 11 meteorological stations from 1971 to 2015 in Inner Mongolia Daxing’anling forest region, the linear regression, inverse distance weighted (IDW) interpolation and Morlet wavelet analysis method were employed to analyze the spatiotemporal dynamics of precipitation days and intensity at different grades in Daxing’anling forest region, Inner Mongolia. The results showed that: (1) Lightrain days showed a decreasing trend, while the variation trends of moderate and heavyrain days were not obvious. The variation trend in annual precipitation intensity at each grade was not significant. The fluctuation of heavyrain intensity tended to be gentle after 2000. (2) The average contribution rate of precipitation at different grades was in the order of heavy rain>moderaterain>light rain. (3) Different grades of precipitation intensity showed different periodic variation patterns on different time scales. The lightrain showed periodic variations on 7, 13, 19, 27 a, moderaterain on 22 and 10 a, and heavy rain on 25 and 7 a. (4) Spatially, moderaterain days, heavyrain days and precipitation intensity at all levels showed a gradual increase trend from the west to the east, while lightrain days showed an opposite pattern. (5) There was no significant difference in spatial variation of annual precipitation in Daxing’anling forest region. The results can provide basic reference for forestry and agricultural production in this region.

Discussion on the protection and restoration technology of secondary forest ecosystems in Northeast China.

YU Li-zhong1,3,4*, LIU Li-fang1,4, WANG Xu-gao1, SUN Yi-rong1,4， KONG Xiang-wen2， GAO Tian1,4， LI Xiu-fen3,4

2017, 36(11):  3243-3248. 

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As an important ecological barrier, forests in Northeast China play critical roles in national ecological civilization construction, environmental protection, and socioeconomic development.  Based on the analysis of current situation of forest resources in Northeast China, the current problems and the development direction of the secondary forest ecosystems were proposed. Furthermore, according to the National Forest Management Plan for the coming thirty years and National Natural Forest Protection Project (NNFPP), the technology and measures of protection, restoration and utilization for the secondary forest ecosystems were put forward, and the management and protection of secondary forest ecosystems during the period of “post-NNFPP” were also explored. All of these would be conducive to sustainable development of forests in Northeast China.

 

Forestation and management scheme of Pinus sylvestris var. mongolica plantations in sandy lands based on their decline mechanisms.

SONG Li-ning1,2,3, ZHU Jiao-jun1,2,3*, ZHENG Xiao1,2,3

2017, 36(11):  3249-3256. 

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Pinus sylvestris var. mongolica (MP) is the most important evergreen conifer tree species for afforestation in the Three North Shelter Forest Program. Since the beginning of 1990s, however, the MP plantations in the earliest introduced area (more than 30-35 years old) have declined, which are characterized by withered top, low growth rate, dead stems and no natural regeneration. A series of experiments in comparison with the sparse MPgrassland in Keerqin sandy land and natural MP forests in Hulunbeier sandy land have been conducted by using thermal dissipation, stable isotope and remote sensing technologies. As a result, the mechanisms of the decline of the MP plantations have been almost determined. In this paper, we systematically summarized the previous results about the decline mechanisms of the MP plantations. The major conclusions are as follows: the soil moisture threshold of severe water stress for the MP plantation was determined (20% of field capacity); the water use strategy (9-21 years old trees only used soil water, but 31-41 years old trees used both soil water and groundwater) and the water balance of MP plantations (water imbalance, 39 mm of groundwater was used to maintain water balance) were tested; as well as the contribution of transpiration of MP plantations to consumption of water resources at a regional scale was quantified (consuming 12.3% of total water resources). Finally, the decline processes of the MP plantations were revealed. Based on these findings, countermeasures solving the decline of MP plantations and afforestation programs have been proposed, which provides reference for preventing decline and rational management for existing MP plantations, and spatial layout for this tree species in the future.

Advances on research of pyrogenic carbon in forests.

HUANG Wen-tao1,2, HU Yuan-man1, CHANG Yu1*, LIU Miao1, ZHANG Hong-xin3, ZHANG Wei3

2017, 36(11):  3257-3265. 

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Pyrogenic carbon (PyC) is a continuum that is produced by incomplete combustion of biomass or fossil fuels. On account of the high stability of PyC, it is a vital potential carbon (C) sink, which plays an important role in global C cycling and climate change. As the main part of terrestrial ecosystems, forest ecosystems have been disturbed by forest fires of different sizes and intensities every year. Therefore, a lot of PyC is accumulated in forest ecosystems. Moreover, with global warming, the forest fire occurrence and burned area will increase, and so will the accumulation of PyC. The PyC has become an important part of C pool in forest ecosystems. However, PyC pool in forests has not been considered in the forest ecosystem C cycle and its related ecological models. This paper reviews PyC identification and quantification, PyC in forests, ecological roles of PyC and estimation of PyC stock. Finally, we discuss future directions of forest PyC study to provide reference for the related studies of forest C budget and C cycle in China.

 

Advance in studies on the effects of climate change on decomposition of tree litters.

XU Sheng, FU Wei, PING Qin, HE Xing-yuan*, CHEN Wei, WU Xian, SU Li-li, HUANG Yan-qing

2017, 36(11):  3266-3272. 

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Global climate change has been widely concerned all over the world for many years. There are lots of studies on the effects of climate change factors including global warming, drought, increasing CO₂ concentration and nitrogen deposition on forest ecosystems. Tree litters play an important role in matter cycles in forest ecosystems, and their response to climate change has been studied extensively. However, the results and mechanisms of climate change effects on litter are still much controversial, due to the differences in experimental methods including tree species, treatment time, etc. In addition, comprehensive reports are lacking in the advance of the effects of climate change on tree litter decomposition. Previous studies are scattered, and limited to a narrow scope. In this paper, we comprehensively review the effects of climate change including global warming, drought, increasing CO₂ and O₃ concentrations and nitrogen deposition on litter quality and decomposition of trees. Some prospects of the effects of climate change on tree litters are also reviewed. This review may provide some scientific references for the studies of forest litters and the development of some ecological theories, particularly the matter and nutrient cycles in forest ecosystems under global climate change.

A review of formation mechanism on the ‘divergence problem’ of tree growth-climate relationship.

GAI Xue-rui1,2, YU Da-pao1, WANG Shou-le1,2, JIA Xiang3, WU Jian1,2, ZHOU Wang-ming1, ZHOULi1, DAI Li-min1*

2017, 36(11):  3273-3280. 

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The “divergence problem” of tree radial growth-climate relationship arose in the 1990s. Initially, tree-ring researchers found the phenomenon that the temperature sensitivity of tree’s radial growth decreased at Alaska’s alpine timberline. Then, similar reports appeared in many regions of the mid and high latitudes in the northern hemisphere. This discovery raises a challenge to the established basic hypothesis in dendrochronology-“uniformity principle” of relationship of radial growth-climate, and to the scientificity of data derived from ring index based on the hypothesis. Despite extensive research published, there are lots of arguments about the causes and mechanisms of the formation of “divergence problem”. To clarify the formation mechanism of “divergence problem”, this review sorted the related research in the literature into location, tree species, driving factors and analyzed the misjudgment induced by research methods. The results showed that the tree species involved in “divergence problem” are growing mainly in the regions of midhigh latitude and high altitude, and sensitive to moisture and temperature. The climate warming and drying in these regions resulted in soil water deficit (exceeding the water threshold) or temperatureinduced physiological changes of trees (exceeding the temperature threshold of normal growth or dormancy). Consequently, climate sensitivity or tree growth decreased. There are some other explanations for the formation mechanism, including the change of atmospheric CO₂ concentration, the influence of anthropogenic activities; however, the threshold hypothesis is the most possible explanation for the formation mechanism of “divergence problem”.

A review on water transport in xylem of vascular plants and its affecting factors.

ZHANG Hong-xia1,2, YUAN Feng-hui1*, GUAN De-xin1, WANG An-zhi1, WU Jia-bing1, JIN Chang-jie1

2017, 36(11):  3281-3288. 

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The mechanism of water transport in vascular plants is one of the most important topics in plant research. As a longdistancetransport tissue in vascular plants, xylem provides a low resistance pathway for water movement from root to leaf. Since the xylem is a structural network of interconnected conduits, altered network structure of xylem following the changes in abiotic factors (e.g. water stress, nitrogen deposition, light, etc.) directly affects the dynamics of water transport in plants. Based on the review of driving force and microstructure for xylem water transport, uptodate understanding of the mechanism of xylem water transport was briefly summarized in this paper, and the direct and indirect impacts of abiotic factors on the xylem water transport were also discussed. Finally, a promising observation technique for xylem network structure was introduced and further studies on the interaction of various factors in xylem water transport were suggested.

 

The development status and breeding trend of hardy kiwifruit cultivars in the world.

ZHANG Min1, WANG He-xin1,2, LOU Xin1,2*, ZHAO Li-na1, YAN Dong-ling1

2017, 36(11):  3289-3297. 

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Hardy kiwifruit, a perennial deciduous vine, belongs to the genus Actinidia (Actinidiaceae). The fruit of hardy kiwifruit features multiple nutrients, sweet and sour tasting, as well as unique flavor. High tolerance of frost and freezing characterizes the adult hardy kiwifruit plant. Recently, as a new economic tree species with great explorative potentials, hardy kiwifruit has gained much attention all over the world. In this study, the characteristics of 74 kiwifruit species from different countries and regions of the world were summarized and analyzed. Meanwhile, this study also pointed out the future directions of selecting and breeding of hardy kiwifruit cultivars. These results may be helpful for breeding and exploration of kiwifruit cultivars in China.

RS/GISbased evaluation of forest ecosystem service value in Northeast China.

XIAO Xiao1,2, MU Zhi-lin3, ZHAO Xue-yan4, LI Jing-zhong2,5, XUE Bing1,2*

2017, 36(11):  3298-3304. 

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Forest ecosystem is a critical component of the terrestrial ecosystem, and its service value evaluation could offer a scientific basis for improving forestry sustainability as well as for policy making. This study applied the remote sensing interpretation data of the forest in Northeast China in 2015 to assess the ecosystem service value and figure out its spatial distribution pattern. The results showed that the ecosystem service value in Northeast China achieved 2.4066 trillion CNY, consisting of biodiversity protection (942.4 billion CNY), carbon fixation and oxygen releasing (784.2 billion CNY), water conservation (546.9 billion CNY), soil conservation (111.8 billion CNY), accumulation of nutrients (12.3 billion CNY), and purification of atmospheric environment (9.0 billion CNY). Spatially, the ecosystem service value showed an increasing trend from west to east, particularly between the eastern and western regions of Heilongjiang and Jilin provinces. The research results were of great significance to policymaking of forest resources management and establishing sustainable environmental accounting system in Northeast China.

Spatial overlapping analysis for nature reserves, forest parks and wetland parks in forestry management system of Northeast China.

YANG Zhen, CHENG Kun, FU Li-qiang, ZONG Cheng*, MA Jian-zhang

2017, 36(11):  3305-3310. 

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The protected areas of China mainly include nature reserves, scenic areas, forest parks, wetland parks, geological parks and other categories. The purpose and management system of these categories are different, and some protected areas overlapped in spatial distribution because different institutions selected and established them respectively. This paper analyzed the spatial distribution and overlapping area of protected areas under forestry management system in Northeast China, using spatial overlay analysis of GIS. The results indicated that nature reserves, forest parks and wetland parks covered  86.24% of cities and counties in Northeast China, with a small amount of gaps in protected areas in counties of west Heilongjiang, middle and west Jilin and middle Liaoning. There were 345000 hm² of 20 overlapping areas between the two categories of nature reserves, forest parks and wetland parks, among which 319800 hm² of 16 overlapping areas were found between nature reserves and forest parks. The main overlapping areas were in Daxinganling, Xiaoxinganling and Changbai Mountain where the natural resources were rich. Though the purpose of establishing several protected areas in the same region is to develop more functions, the overlapping of protected areas caused many problems of conservation and management. So, we proposed suggestions of overlapping status survey, unified management mechanism, and clear administrative privileges.

Applications of nuclear magnetic resonance in the study of plant litter decomposition in forest ecosystems.

WANG Yu-zhe, LIU Xian, HU Ya-lin*

2017, 36(11):  3311-3320. 

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Litter decomposition links the above and belowground carbon (C) and nutrient cycling in forest ecosystems, and plays a key role in the global C cycles through its controls on fluxes of carbon dioxide (CO₂) and the formation of soil organic matter (SOM). Thus, it is important to investigate the dynamics of organic C composition in decomposing litter under global climate change. Unlike traditional proximate wetchemical analyses, nuclear magnetic resonance (NMR) spectroscopy is a nondestructive and noninvasive technique, and has been considered as a valuable tool in the characterization of the chemical compositional changes of organic C during plant litter decomposition at the level of functional group. The aim of this study was to give an overview of the application of NMR technique in the study of plant litter decomposition. We summarized the peerreviewed articles that contained NMR spectra of both undecomposed and decomposed litters based on four plant groups (broadleaf trees, conifers, shrubs, grasses). The dynamics of different organic C functional groups and their ratios in litter during decomposition as well as the underlying mechanisms were discussed. NMR technique would be helpful to improve our understanding of the decomposition of different organic C groups in litter and its controls on the builtup of soil organic matter.

Estimating model of typical forest litter moisture content based on the field spectrum in Daxing’anling of China.

XIE Zi-xi1, HU Hai-qing1, YANG Xi-guang2, SUN Long1*

2017, 36(11):  3321-3328. 

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Daxing’anling is a highly frequent forest fire disaster area in China. Accurate prediction of forest fuel moisture content is of great significance to improve the accuracy of forest fire forecast in this area. In this study, first derivative transformation and continuum removal methods were used to identify the bands sensitive to forest litter moisture. And the correlation coefficients were calculated between measured forest litter moisture and four spectral variables, including the original reflectance, the first derivative reflectance, the continuumremoval reflectance and first derivate of the continuumremoval reflectance. Then the highly relevant bands were selected as independent candidate variables and the forest litter moisture content estimation model was established by using a stepwise regression method. The determination coefficient (R²), mean relative error (MRE) and root mean square error (RMSE) of the model were calculated for evaluating the model. The results showed that there was a higher correlation between forest litter moisture content and first derivate of the continuumremoval reflectance compared to other spectral variables. The more sensitive bands were 398-668, 768-1068, 1098, 1278, 1388-1438, 1458-1538, 1868-1898, 1988-2088, 2198-2208, 2228-2238 nm (P<0.05). The extreme values of the correction coefficients were -0.653 and 0.610 at 2008  and 1888 nm, respectively. The model used to estimate forest litter moisture content was established by using multilinear stepwise regression method. The R², MRE and RMSE of the model were 0.537, 0.303 and 0.499, respectively. This study provides reference in fast estimating forest litter moisture content by using remote sensing technology.