Variation of carbon source and sink along the environmental gradient from lakeside to highlands in Yuanchi swamp wetlands, Changbai Mountains, China.

Lacustrine wetlands have long-term carbon storage capacity and contribute significantly to regional carbon cycle, but it is unclear how its carbon sinks respond to climate change. We measured soil heterotrophic respiration carbon emissions (CO2 and CH4), vegetation carbon sequestration, and related environmental factors (temperature, water level, etc.) of five kinds of natural swamps (Phragmites marsh-L, Carex schmidtii marsh-C, Rhododendron capitatum swamp-D, Betula fruticose swamp-H, Larix olgensis swamp-LT)by using static chamber gas chromatography and relative growth equation methods, along the water environmental gradients from lakeside to highlands in Yuanchi of Changbai Mountains. We quantified the carbon source/sink function (CSS) and global warming potential (GWP) of various swamp types by estimating ecosystem net carbon balance, and revealed the variation patterns and formation mechanisms of CSS and GWP along the environmental gradients, aiming to explore the response of carbon source/sink of lakeside wetland in high altitude area to climate change. The results showed that marshes (L and C) were weak sources (-1.018 and -0.090 t C·hm-1·a-1) at the lower habitats of the water environment gradient, shrub swamps (D and H) were strong or weak sinks (1.956 and 0.239 t C·hm-1·a-1) at the middle habitats, forest swamp (LT) was strong source (-3.214 t C·hm-1·a-1) at the upper habitat. The spatial changes were promoted by water level and suppressed by soil temperature. For GWP, strong thermal radiation for marshes (from 44.682 to 59.282 t CO2·hm-1·a-1), cold radiation for shrub swamps (from -0.920 to -7.008 t CO2·hm-1·a-1), and weak thermal radiation for forest swamp (11.668 t CO2·hm-1·a-1), and their GWP was only promoted by soil temperature. Under current climate change background, marshes and forest swamp at both ends of the water environment gradient from lakeside to highlands played a positive feedback effect due to the increases of CH4 or CO2 emissions, while the middle shrub swamp still maintained a negative feedback effect in Yuanchi located the high-altitude area of the temperate Changbai Mountains.

[Spatial differentiation and mechanism of carbon source/sink of forest swamps in riverside of Changbai Mountains, China]. / 长白山河滨森林湿地碳源/汇空间分异规律及机制.

To quantify the carbon source/sink function of riparian zone swamps and explore the feedback relationship with climate change, we measured the annual fluxes of soil greenhouse gas, soil carbon emission, net vegetation carbon sequestration and related environmental factors (temperature, water level, etc.) by static chamber-gas chromatography and relative growth equation methods in three kinds of forest swamps (Alnus sibirica swamp, Betula platyphylla swamp, and Larix olgensis swamp) distributed along the water reduction gradient of lowland to highland in the stream riparian zone of Changbai Mountains. The results showed that the annual fluxes of CH4(0.19-0.85 mg·m-2·h-1), CO2(60.81-228.63 mg·m-2·h-1), and N2O (-0.02-0.05 mg·m-2·h-1) showed spatial variations along the water gradient of lowland to highland, with a trend of first constant then decreasing, decreasing, and first absorption then emission, respectively. The spatial variations of annual fluxes of these greenhouse gases were controlled by water levels. The annual net carbon sequestration of vegetation (2.61-3.45 t C·hm-2·a-1) was constant along the water gradient, which was mainly promoted by nitrate nitrogen content. The carbon source/sink and global warming potential (GWP) undergo regular changes along water gradients. The A. sibirica swamp was a carbon sink (1.93 t C·hm-2·a-1), the B. platyphylla swamp was a weak carbon source (-0.18 t C·hm-2·a-1), and the L. olgensis swamp was a strong carbon source (-2.51 t C·hm-2·a-1). The spatial variation of carbon source/sink in forest swamps was jointly promoted by water level and nitrate nitrogen content. A. sibirica swamp exhibited a strong cooling effect with a strong negative feedback effect on climate change (-5.88 t CO2·hm-2·a-1). L. olgensis swamp exhibited a strong warming effect with a strong positive feedback effect (10.97 t CO2·hm-2·a-1). B. platyphylla swamp exhibited a weak warming effect, approximately neutral (2.95 t CO2·hm-2·a-1). The spatial variation of GWP in forest swamps was mainly inhibited by water level.

Effects of light-felling intensity on hydrological effects of litter in Korean pine forests by 'planting conifer and preserving broadleaved tree' in Xiaoxing'an Mountains of China.

To understand the effects of 'planting conifer and preserving broadleaved tree' and light-felling on the hydrological effects of litter layer during the restoration of the climax vegetation broad-leaved Korean pine forest in temperate zone of Northeast China, we measured litter accumulation, water holding process of litter, and maximum holding water, maximum blocking and effective blocking amount of litter layers using sample survey method and indoor immersion method in three forests (aspen-Korean pine forests, white birch-Korean pine forest, and Mongolian oak-Korean pine forest) under different light-felling intensity (control, C; low light-felling, L; moderate light-felling, M; heavy light-felling, H) in Xiaoxing'an Mountains. The results showed that the intensity of light-felling had different effects on litter accumulation (7.32 to 15.58 t·hm-2) in three forest types. L, M and H significantly enhanced litter accumulation by 24.3%-34.6% in the Mongolian oak-Korean pine forest, L and M enhance it by 15.3%-19.3% in aspen-Korean pine forest, and H enhance it by 27.1% in white birch-Korean pine forest. Water holding capacity (W) and water absorption rate (V) of the undecomposed layer and the semi-decomposed layer of the litter were in accordance with the relationship between the soaking time (t): W=alnt+b (R2>0.908), V=ktn (R2≥0.999). The intensity of light-felling (except H in aspen-Korean pine forests) increased the maximum water holding capacity (17.86-45.12 t·hm-2), maximum interception capacity (16.10-34.19 t·hm-2) and effective interception capacity (13.42-27.42 t·hm-2) of litter by 30.1%-74.8%, 27.4%-83.6% and 26.7%-86.0%, respectively, while changed the differences of effective blocking amount of litters among forest types. Therefore, light-felling significantly enhanced the hydro-ecological function of litter layers in the medium-term broad-leaved Korean pine forests by 'planting conifer and preserving broadleaved tree'. The low, moderate, and heavy light-felling was best one for the Mongolian oak-Korean pine forest, the aspen-Korean pine forest, and the white birch-Korean pine forest, respectively.

[Effects of harvest on greenhouse gas emissions from forested swamp during non-growing season in Xiaoxing'an Mountains of China.] / é‡‡ä¼å¯¹å°å ´å®‰å²­æ£®æž—æ²¼æ³½éžç”Ÿé•¿å­£åœŸå£¤æ¸©å®¤æ°”ä½“æŽ’æ”¾çš„å½±å“.

Soil greenhouse gas emission during non-growing season plays an important role in ecosystem carbon and nitrogen cycling in mid and high latitude regions. However, the effects of harvest on greenhouse gas emission during non-growing remain unclear. We measured the fluxes of CO2, CH4 and N2O and environmental factors (soil temperature, moisture, soil organic carbon and total nitrogen etc.) during non-growing season from four kinds of forested swamps (Alnus sibirica swamp, Betula platyphylla swamp, Larix gmelinii-Carex schmidti swamp, L. gmelinii-moss swamp) under different harvest disturbances for 10 years, including control (no cutting), 45% selective cutting, clear cutting, by using static chamber technique and gas chromatography in Xiaoxing'an Mountains, Northeast China. The aim of this study was to reveal the effects of harvest on greenhouse gas emission from temperate forested swamp during non-growing season and the main controlling factors. The results showed that the average fluxes of CO2, CH4 and N2O from four kinds of swamps distributed in 53.08-81.31 mg·m-2·h-1, 0.09-3.07 mg·m-2·h-1 and 4.07-8.83 µg·m-2·h-1, respectively. Clear cutting significantly increased the fluxes of CO2, CH4, and N2O from A. sibirica swamp and L. gmelinii-moss swamp. Selective cutting significantly increased CO2 fluxes from B. platyphylla swamp and L. gmelinii-moss swamp and decreased CO2 flux from A. sibirica swamp. Selective cutting significantly decreased CH4 fluxes from all the four forested swamps and N2O flux from Larix gmelinii-Carex schmidti swamp. The CO2 fluxes from natural forested swamps were strongly influenced by soil temperature, soil organic carbon and C/N. CH4 fluxes were influenced by soil temperature, soil organic carbon. N2O fluxes were affected by air temperature and soil pH. Harvesting increased the correlation between soil CO2 flux and air temperature, soil moisture and snow depth, the correlation between soil CH4 flux and air temperature, soil moisture and C/N, as well as the correlation between soil N2O flux and soil total nitrogen and C/N. The annual cumulative contribution of CO2, CH4 and N2O emission from natural forested swamp during non-growing season were 33.2%-46.5%, 6.3%-9.1% and 61.5%-68.3%, respectively. The clear cutting increased the annual cumulative contribution of CO2 from B. platyphylla swamp and L. gmelinii-moss swamp and that of N2O from other swamps except L. gmelinii-moss swamp. The selective cutting increased the annual cumulative contribution of CO2, CH4 and N2O from L. gmelinii-C. schmidti swamp and L. gmelinii-moss swamp, but decreased that from B. platyphylla swamp. The annual cumulative contributions of N2O and CO2 during non-growing season were relatively high from temperate natural forested swamps, and clear cutting further increased their contribution, while the selective cutting just increased that of CH4 during non-growing season.

[Effects of light-felling on non-growing season greenhouse gas emission from soils in Korean pine forests in Maoer Mountains, China.] / é€å ‰æŠšè‚²å¯¹æ¸©å¸¦å¸½å„¿å±±çº¢æ¾æž—éžç”Ÿé•¿å­£åœŸå£¤æ¸©å®¤æ°”ä½“æŽ’æ”¾çš„å½±å“.

Non-growing season soil greenhouse gas emission may play an important role in the forest ecosystem carbon and nitrogen cycle. However, it is not clear about the effects of the cutting distur-bance on soil greenhouse gas emissions during non-growing season. The CO2, CH4 and N2O fluxes and related environmental factors (soil temperature, water content, carbon and nitrogen, etc.) were monitored in the Korean pine plantation (fifty year-old) under different light-felling manners (control, no cutting; the half light-felling, cutting 50% of broad-leaved trees in canopy; the whole light-felling, cutting 100% of broad-leaved trees in canopy), using static chamber technique and gas chromatography during non-growing season in Maoer Mountains of China. The main aim was to reveal the influence of cutting disturbance on soil greenhouse gases emission during non-growing season and its controlling factors. The results showed that the whole and half light-felling manners significantly decreased CO2emission flux by 21.0% and 22.8%, and N2O by 23.5% and 11.2%, and decreased CH4uptake by 16.0% and 16.4%. The contribution of non-growing season CO2, CH4 and N2O emission to annual total was 11.7%-14.2%, 13.1%-17.0% and 63.9%-72.6%, respectively. Light-felling manners decreased annual cumulative contribution of CO2 by 1.4%-2.5%, that of CH4 by 0.7%-3.9%, but increased that of N2O by 2.4%-8.7%. Furthermore, light-felling increased the correlations of soil CO2 fluxes with soil temperature, soil water content, nitrate and ammonium, and decreased its correlation with soil organic carbon content. Light-felling increased the correlations of soil CH4 flux with soil water content, soil pH, soil organic carbon, ammonium, and decreased its correlation with nitrate. Light-felling increased the correlations between soil N2O flux and soil temperature, decreased the correlations with nitrate and ammonium, and changed the positive correlation with soil pH to negative. Therefore, light-felling had significant effects on the emission fluxes of the greenhouse gas during non-growing season, with the whole light-felling decreased more soil N2O emission flux than the half light-felling.

[Short-term effects of fire disturbance on greenhouse gases emission from Betula platyphylla-forested wetland in Xiaoxing'an Mountains, Northeast China].

By the methods of static chamber and gas chromatography, this paper studied the effects of fire disturbance on the seasonal dynamics and source/sink functions of CH4, CO2 and N2O emissions from Betula platyphylla-forested wetland as well as their relations with environmental factors in Xiaoxing' an Mountains of China. In growth season, slight fire disturbance on the wetland induced an increase of air temperature and ground surface temperature by 1.8-3.9 degrees C and a decrease of water table by 6.3 cm; while heavy fire disturbance led to an increase of air temperature and 0-40 cm soil temperature by 1.4-3.8 degrees C and a decrease of water table by 33.9 cm. Under slight or no fire disturbance, the CH4 was absorbed by the wetland soil in spring but emitted in summer and autumn; under heavy fire disturbance, the CH4 was absorbed in spring and summer but emitted in autumn. The CO2 flux had a seasonal variation of summer > spring = autumn under no fire disturbance, but of summer > autumn > spring under fire disturbance; and the N2O flux varied in the order of spring > summer > autumn under no fire disturbance, but of autumn > spring > summer under slight fire disturbance, and of summer > spring = autumn under heavy fire disturbance. At unburned site, the CO2 flux was significantly positively correlated with air temperature and ground surface temperature; at slightly burned site, the CO2 flux had significant positive correlations with air temperature, 5-10 cm soil temperature, and water table; at heavily burned sites, there was a significant positive correlation between CO2 flux and 5-40 cm soil temperature. Fire disturbance made the CH4 emission increased by 169.5% at lightly burned site or turned into weak CH4 sink at heavily burned site, and made the CO2 and N2O emissions and the global warming potential (GWP) at burned sites decreased by 21.2% -34.7%, 65.6% -95.8%, and 22.9% -36.6% respectively, compared with those at unburned site. Therefore, fire disturbance could decrease the greenhouse gases emission from Betula platyphylla-forested wetland, and planned firing could be properly implemented in wetland management.

[Effects of forest cutting on greenhouse gas emissions from Larix gmelini-Sphagnum swamps in Lesser Xing' an Mountains of Heilongjiang, China].

By using static chamber and gas chromatography methods, this paper studied the effects of clear cutting and selective cutting on the CO2, CH4, and N2O emissions from Larix gmelini-Sphagnum swamp in Lesser Xing' an Mountains. Dramatic changes in the seasonal dynamics of CH4 and N2O emissions were detected in different treatment sites. Control site absorbed CH4 in summer and emitted CH4 in autumn, and absorbed N2O in both summer and autumn; selective cutting site emitted CH4 and N2O mainly in summer; and clear cutting site emitted CH4 in summer and autumn, and absorbed N2O in summer but emitted it in autumn. Cutting pattern had less effects on the seasonal dynamics of CO2 emission. Both on the clear cutting site and on the selective cutting site, the CO2 emission was in order of summer > spring > autumn. Forest cutting altered the source and sink functions of the sites. Control site functioned as a source of CO2 and a weak sink of CH4 or N2O, while forest cutting sites had a decrease of CO2 emission by 25%, and became a weak source of N2O and a weak or strong source of CH4. Compared with that of control site, the Global Warming Potential (GWP) of selective cutting site and clear cutting site was reduced by 24.5% and increased by 3.2%, respectively.

[Distribution patterns of woody plant diversity in stream riparian forests along an altitudinal gradient in Changbai Mountains].

By setting up sample transects and using alpha and beta diversity indices, this paper studied the woody plant diversity and its responses to cutting in the stream riparian primeval and secondary forests along an altitudinal gradient in Changbai Mountains. The results showed that all of the primeval forest communities distributed at different altitudes were composed of 11-13 tree species, but the importance of these tree species varied with altitude. Conifer species gradually took the place of broad-leaved tree species along the altitudinal gradient. Cutting not only made the tree species richness and importance changed, but also further strengthened the trend of tree species replacement. The Shannon-Wiener diversity index of the woody plants in primeval forests varied from 2.454 to 2.544 at the altitudes of 750-800 m, 800-850 m and 850-900 m, which was higher than that (2.250) at the altitude of 900-950 m. Cutting changed this distribution pattern, and enlarged the fluctuation (2.174-2.692) among the communities at different altitudes. The Cody index of primeval forest communities along the altitudinal gradient varied from 1.5 to 3.5, and the community similarity coefficient varied from 0.85 to 0.94. As for the secondary forest communities, their Cody index and community similarity coefficient changed from 0.5 to 6.0 and from 0.68 to 0.91, respectively, indicating that cutting increased the tree species replacement rate, and reduced the community similarity. However, a higher continuity still existed in the secondary forest communities.