Temporal and spatial variations and influencing factors of gross primary productivity in Changbai Mountain Nature Reserve, China.

Changbai Mountain Nature Reserve (CNR) is a typical temperate forest ecosystem, and gross primary production (GPP) of which is closely related to topography and climate change. Research on the spatio-temporal variations and influencing factors of GPP in the CNR is of great significance for assessing growth status of vegetation and the quality of ecological environment. We calculated GPP in CNR using the vegetation photosynthesis model (VPM), and analyzed the influences of slope, altitude, temperature, precipitation, and total radiation. The results showed that the range of annual average GPP in CNR was 63-1706 g C·m-2·a-1 from 2000 to 2020 and that GPP decreased with the increases of altitude. Temperature played the most important role in driving the spatial varia-tion of GPP, with a significant positive correlation with GPP. During the study period, the overall annual GPP showed a significant increase trend in CNR, with an average annual increase of 13 g C·m-2·a-1. The areas with increase of annual GPP accounted for 79.9% of the total area, and the area proportion of annual GPP increase differed in each plant functional type. Annual precipitation was significantly negatively correlated with GPP in 43.2% of CNR, while annual mean temperature and annual total radiation were significantly positively correlated with GPP in 47.2% and 82.4% of CNR. GPP would increase continuously in CNR under the scenario of future global warming.

[Water use efficiency and leaf nutrient characteristics of five major tree species in broadleaved Korean pine forest in Changbai Mountains, China]. / 长白山阔叶红松林5ç§ä¸»è¦æ ‘ç§æ°´åˆ†åˆ©ç”¨æ•ˆçŽ‡ä¸Žå¶ç‰‡å »åˆ†ç‰¹å¾.

Water use efficiency (WUE) of five dominant tree species (Pinus koraiensis, Fraxinus mandshurica, Acer mono, Quercus mongolica, and Tilia amurensis) was estimated using the stable carbon isotope method in a broadleaved Korean pine forest in Changbai Mountains. Leaf carbon (C), nitrogen (N), and phosphorus (P) contents were measured to analyze nutrient utilization of the dominant species. The relationship between WUE and leaf nutrient contents was systematically assessed. WUE was different due to the variations of micrometeorological factors at different locations in the canopy. The four broadleaved tree species showed upper layer > middle layer > lower layer, while P. koraiensis showed upper layer > lower layer > middle layer. WUE of evergreen coniferous P. koraiensis was higher than that of two broadleaved species with diffuse-porous wood (T. amurensis and A. mono) and lower than that of two broadleaved species with ring-porous wood (F. mandshurica and Q. mongolica). The compound-leaved species (F. mandshurica) had the highest WUE. The WUE of new leaves was significantly higher than old leaves in P. koraiensis. The carbon content and C/N of the old and new leaves of evergreen coniferous P. koraiensis were significantly higher than those of the other four broadleaved tree species, while nitrogen content and N/P were significantly lower than those of the four broadleaved tree species. P content of old leaves of P. koraiensis was significantly lower than that of the four broadleaved tree species. P content of new leaves of current year was not significantly different from that of the broadleaved tree species. The WUE of five tree species had a poor correlation with leaf C content, but a positive correlation with leaf N content. The WUE of evergreen coniferous and deciduous broadleaved tree species was correlated with leaf P content but in opposite direction.

[Characteristics of water use efficiency in a succession series of broadleaved Korean pine forests in Changbai Mountain, China.] / 长白山阔叶红松林演替序列水分利用效率特征.

Water use efficiency (WUE) is an objective indicator of plant water use, the research of which is helpful to understand the carbon-water coupling mechanism in terrestrial ecosystems. We investigated WUE of dominant tree species in the succession series of broad-leaved Korean pine forests in Changbai Mountain (middle-aged poplar-birch secondary forest, mature poplar-birch secondary forest, broad-leaved Korean pine forest) by using stable carbon isotope technology. The WUE of three forests under different succession stages decreased in order of broad-leaved Korean pine forest > middle-aged poplar-birch secondary forest > mature poplar-birch secondary forest. In addition, the same tree species had different WUE in different forest stands. The WUE of Populus davidiana and Betula platyphylla in the middle-aged poplar-birch secondary forest was higher than that in mature poplar-birch secondary forest. The WUE of Fraxinus mandshurica in broad-leaved Korean pine forest was much higher than that in middle-aged poplar-birch secondary forest. The WUE of Acer mono and Quercus mongolica in broad-leaved Korean pine forest was higher than that in mature poplar-birch secondary forest. The dominant tree species had different WUE as for wood types which generally presented ring-porous wood species>diffuse-porous wood species. There were different seasonal trends during the growing season among the dominant species in the broad-leaved Korean pine forest. The WUE of Fraxinus mandshurica, Acer mono, Quercus mongolica and Tilia amurensis showed first decreasing and then increasing, while that of Pinus koraiensis was opposite. The WUE of the broad-leaved Korean pine forest was negatively correlated with temperature in the growing season. The different WUE was one of the strategies for dominant species in the broad-leaved Korean pine forest in Changbai Mountains to adapt to the community succession and respond to climate and environmental change.

[Effects of water and nitrogen stress on water utilization of dominant species in broadleaved Korean pine forest in Changbai Mountain, China]. / æ°´æ°®èƒè¿«å¯¹é•¿ç™½å±±é˜”å¶çº¢æ¾æž—ä¼˜åŠ¿æ ‘ç§æ°´åˆ†åˆ©ç”¨çš„å½±å“.

The aggravation of global nitrogen deposition may change plant water utilization and affect plant growth. Understanding the changes of vegetation water consumption under nitrogen deposition is of great significance for simulating and predicting the evolution of each component of forest hydrological cycle. We used the hydrogen and oxygen isotope tracer method to analyze water consumption source, quantity and law of Quercus mongolica (Qm), Fraxinus manshurica (Fm) and Tilia amurensis (Ta), the dominant species in broadleaved Korean pine forest of Changbai Mountain, under different add amounts of nitrogen [low nitrogen addition group (11.8 kg·hm-2·a-1), LN; high nitrogen addition group (23.6 kg·hm-2· a-1), HN] and different amounts of simulated precipitation (water addition amount were 0, 400, 800 and 1600 mL, equivalent to single rainfall amount were 0, 16, 32 and 64 mm, respectively). The results showed that under the condition of relative drought, soil water utilization ratio of Qm, Fm and Ta in the LN group were 26%, 12% and 20%, higher than that in HN group. When the amount of simulated precipitation was 16 mm, soil water utilization ratio of Qm, Fm and Ta in LN group reached the highest, being 73%, 70% and 43%, respectively. This ratio also reached a high value in HN group, but being less than the values in LN group. When the amount of simulated precipitation was 32 mm, soil water content approximated the average value in broadleaved Korean pine forest in the growing season in Changbai Mountain. The average soil water utilization ratio of test tree species in HN group was 39%, higher than that in LN group (16%). When the amount of simulated precipitation reached 64 mm, the soil water was saturation. Soil water utilization ratio of Qm, Fm and Ta in LN group was 14%, 5% and 1%, which was lower than that in HN group, the corresponding ratio were 64%, 13% and 10%, respectively. In conclusion, under the condition of less precipitation and relatively dry soil, the soil water utilization ratio of those three tree species were lower, and the increases of nitrogen availability further reduced the ratio. When the amount of precipitation was high and soil moisture was higher than the average value of the growing season, soil water utilization ratio of those tree species was higher. With the increases of soil nitrogen availability, this ratio was further increased.

[Variation characteristics of NDVI and its response to climatic change in the growing season of Changbai Mountain Nature Reserve during 2001 and 2018]. / 2001­2018年长白山自然保护区生长季NDVIå˜åŒ–ç‰¹å¾åŠå ¶å¯¹æ°”å€™å˜åŒ–çš„å“åº”.

To understand the dynamics of temperate forest in Northeast Asia and its response to climate change under the scenario of global change, we examined the temporal and spatial changes of normalized difference vegetation index (NDVI) and their correlation with temperature and precipitation of Changbai Mountain Nature Reserve in the growing season during 2001 and 2018, based on the remote sensing database of MODIS with a resolution of 250 m, land surface temperature data with a resolution of 1 km and meteorological data in the studied and surrounding area. The results showed that, in the growing season of 2001-2018, the averaged NDVI value of the study area was 0.711. Vegetation coverage was relatively high, increasing with a rate of 0.0025·a-1. The temperature showed an extremely significantly increasing trend (0.032 ℃·a-1), the rate of which was higher than that at global level. Precipitation also showed a significantly increasing trend (5.54 mm·a-1) with increased interannual variation. Spatially, NDVI generally was higher in the northwest and decreased with elevation. During the study period, the area with increased NDVI accounted for 46.2%, mainly concentrated in the north and south central high-altitude areas, while 53.8% of total area remained unchanged or slightly decrease. NDVI of the study area was mainly affected by temperature. At the annual scale, NDVI and land surface temperature were positively correlated, with 90.2% presented positive correlation and 43.6% significantly correlated. At the monthly scale, the impact of temperature on NDVI was more significant at the beginning and the end of growing season.

[Applications of compound-specific isotope analysis in tree non-structural carbohydrates research: A review.] / ç‰¹å®šåŒ–åˆç‰©åŒä½ç´ åˆ†æžæŠ€æœ¯åœ¨æ ‘æœ¨éžç»“æž„æ€§ç¢³æ°´åŒ–åˆç‰©ç ”ç©¶ä¸­çš„åº”ç”¨.

Compound-specific isotope analysis (CSIA) can precisely determine the carbon isotopic composition (δ13C) of specific compounds in a complex substrate. The δ13C values in tree non-structural carbohydrates (NSC) compounds, e.g. sugars, organic acids, and sugar alcohols, measured via CSIA could help tracing the newly assimilated photosynthate during carbon transfer and exchange with atmosphere. Further, they can act as sensitive indicators of the physiological response of trees to environmental change. In this review, we first systematically introduced the methods of CSIA with respect to sampling, purification, and analysis. Then, compound-specific δ13C difference among different NSCs and across tree carbon pools, as well as temporal pattern and mechanism underlying the variation of δ13C were described. Finally, we discussed the interaction between δ13C in tree NSCs, the main substrates of respiration, and respired CO2(δ13CR). Further studies on the post-photosynthetic discrimination, tree stress physiology, and tree-ring δ13C formation with the promising applications of CISA were suggested.

[Relationship between tree ring δ13C and net primary productivity of Pinus koraiensis in Changbai Mountain, China]. / é•¿ç™½å±±çº¢æ¾å¹´è½®ç¢³åŒä½ç´ ä¸Žå‡€åˆçº§ç”Ÿäº§åŠ›çš„å ³ç³».

Carbon isotope in tree ring is an effective indicator of climate and environmental change. However, few studies have analyzed the indication effect of tree ring carbon isotope on net primary productivity (NPP) of forests. Based on meteorological factors of growing seasons, we analyzed the variation trend and the relationship between the tree ring δ13C chronosequence of Korean pine (Pinus koraiensis) and net primary productivity (NPP) of Korean pine in Changbai Mountain. We found that before 1970, the change of Korean pine tree ring δ13C and NPP was synchronous, with a highly significant linear positive correlation between them, indicating that tree ring δ13C recorded the impacts of climate change on NPP. After 1970, tree ring δ13C was negatively correlated with NPP but not statistically significant, meaning that other environmental factors such as severe droughts reduced the sensitivity of tree ring δ13C to climate change and the recording of NPP by tree ring δ13C. The δ13C of the current year was also correlated with the corresponding NPP in the following year, which indicated that the current year's environmental conditions were of great significance to the growth of Korean pine in the following year. This study showed that tree ring δ13C was a good indicator of the NPP of Korean pine in Changbai Mountain and that tree ring δ13C had the potential to reconstruct long-term changes of forest NPP in the history.

[Stable carbon isotopic characteristics of plant-litter-soil continuum along a successional gradient of broadleaved Korean pine forests in Changbai Mountain, China.] / 长白山阔叶红松林演替序列植物-凋落物-åœŸå£¤ç¢³åŒä½ç´ ç‰¹å¾.

Stable carbon isotope composition can accurately indicate ecosystem carbon cycling and provide key information for the study of the influence of forest succession on the carbon cycling and carbon sequestration potential. We measured the δ13C values and carbon and nitrogen contents of leaf, trunk, root, litter, and soil along a forest successional gradient in Changbai Mountain, which included a middle-aged poplar-birch secondary forest, a mature poplar-birch secondary forest, and an old-growth broad-leaved Korean pine forest. The results showed that leaf δ13C reduced with their position from the upper canopy to lower canopy, bark δ13C was less than xylem, fine root δ13C was less than course root. In contrast to the secondary forests, δ13C of the undecomposed litter layer was less than that of the semi-decomposed layer and decomposed litter layer in the broad-leaved Korean pine forest. Soil δ13C increased with depth. The ascending order of mean δ13C was leaf, litter, root, trunk, and soil, indicating that there is obvious fractionation among different organs of plants and among different parts of a specific organ. In addition, plant δ13C first decreased and then increased with the succession process, but soil δ13C increased with the succession processes. The different patterns of the changes of plant and soil δ13C along forest succession could be explained by the relationship between nitrogen content and carbon isotope fractionation effect, indicating that carbon isotope fractionation was affected by the change of dominant tree species and the variation of carbon turnover rate.

[Characteristics of climate change in Changbai Mountain ecological functional area, Northeast China.] / 长白山生态功能区气候变化特征.

We integrated the meteorological records from 36 national weather stations and CN05.1 gridded daily observation dataset to analyze the climate change characteristics of Changbai Mountain eco-functional area. Linear tendency estimation, Mann-Kendall mutation test, cumulative anomaly method and Morlet wavelet analysis were used to investigate the temporal and spatial variation of temperature (annual temperature, seasonal temperature, extreme temperature), moisture (annual precipitation, seasonal precipitation, relative humidity), radiation (sunshine duration, sunshine percentage) and wind speed from 1961 to 2016. The results showed that, during 1961-2016, the temperature of this area increased, the radiation and wind speed decreased, and the precipitation varied periodically. Specifically, winter temperature [0.45 ℃·(10 a)-1] and the lowest temperature [0.74 ℃·(10 a)-1] significantly increased. The mean annual wind speed significantly decreased [-0.21 m·s-1·(10 a)-1]. No abrupt climate change was observed. The annual precipitation days decreased considerably [-7.01 d·(10 a)-1], which was different from the climate change pattern of Northeast China. The annual precipitation trend coefficient of this area was 16.06 mm·(10 a)-1 , which could not be simply depicted by increase or decrease in trend. The precipitation change in this area was dominated by periodically patterns, and the period was 26 years and 3 years. Our results would be instructive to the regional ecological assessment, and the research on ecosystem responses to climate change and phenological changes.

[Measuring and calculating methods of plant mesophyll conductance: A review.] / 植物叶肉导度的测定及计算方法综述.

Mesophyll conductance (gm) refers to the diffusion capacity of CO2 inside mesophyll cells, which is the reciprocal of resistance of mesophyll cells. In the early stage of photosynthesis research, mesophyll diffusion resistance to CO2 was usually assumed to be zero, namely the gm was infinite. In recent studies, however, the gm was found to be limited and changed with external environments. As gm directly determines CO2 diffusion and affects leaf photosynthetic efficiency, it is of great significance to mechanestic research of photosynthesis. Presently, simultaneous chlorophyll fluorescence and gas exchange, the curve-fitting and instantaneous carbon isotope (13CO2) discrimination are commonly used to estimate gm, but few literature have been introduced on those methods in China. Therefore, it is particularly necessary to elaborate the principles and processes of these methods and to compare their advantages and disadvantages. We synthesized the relevant literature, and introduced the three methods in detail from the aspects of principle, derivation process and advantages and disadvantages, aiming to provide a methodological basis to promote the research on gm in China. The curve-fitting method was easy to understand and operate. Its fitting model varied with the status of photosynthesis, which is needed to be divided strictly by researchers. Consequently, it was not conducive to be widely used. Although the instantaneous carbon isotope (13CO2) discrimination method improved the accuracy of results, it was complex in measurement and strict in operation. Furthermore, it was less sensitive to test errors with low reliability. Compared with the above two methods, simultaneous chlorophyll fluorescence and gas exchange was more operable and reliable, and was more conducive to the observation and analysis for large samples with multi-processing and multi-repetition. In addition, the use of chlorophyll fluorescence technology not only simplified the test procedures, but also reduced the accidental errors, making the results more scientific. Chlorophyll fluorescence technology also provided saturated pulse activation energy to maximize leaf photosynthetic potential. But this method also had many problems, for instance, to improve the accuracy of chlorophyll fluorescence parameters, a lower gas flow rate was needed, which would increase the risk of gas diffusion and leakage. Thus, this method had a high requirement for a reasonable gas flow rate. In general, simultaneous chlorophyll fluorescence and gas exchange method was most widely used in the actual determination of plant gm.

[Natural science research in Changbai Mountain during 1956-2018:A review.] / é•¿ç™½å±±åœ°åŒºè‡ªç„¶ç§‘å­¦ç ”ç©¶ç»¼è¿°: 1956­2018.

We synthesized the scientific research carried out in Changbai Mountain from 1956 to 2018 by mapping knowledge domains and bibliometrics based on the literature from international database (WOS) and domestic databases (CNKI and CSCD). The results showed that natural science research in Changbai Mountain underwent three stages during 1956-2018, including embryo stage, growing stage, and rapid development stage. The natural research in Changbai Mountain could be divided into five fields, i.e., forest and ecological science, volcano and geology science, environmental change science, resource sciences and utilization, animal and microbial science, with a total of 20 main research directions. Since 2000, forest and ecological science, volcano and geological science, environmental change science dominated the natural science research in Changbai Mountain. The researches in recent 20 years mainly concentrated on the following seven disciplines: community ecology, forest management, soil ecology, ecosystem ecology, eco-climatology, forest responses to environmental change, and volcanic geology. International researches showed a trend of strong integration of different disciplines. We forecast that the natural science research in the Changbai Mountain would deepen its research in the next decade. Moreover, other fields such as old-growth forest and large-scale ecosystem carbon processes, forest-altitude-climate change, soil fauna and microorganisms, forest management and human activities, biodiversity, volcanic origin and eruption history, volcanic eruption dynamics and volcanic monitoring will emerge as the new research focus. Scale polarization, elements diversification, discipline crossing, and research deepening would be the future trend of natural science research in Changbai Mountain.

[Applicability of daytime downward longwave radiation parameterized models in Changbai Mountains, Northeast China].

A total of eight clear-sky and eight cloudy-sky parameterized models for estimating daytime downward longwave radiation were evaluated by using the meteorological data measured in the Changbai Mountains region, Northeast China. The results indicated that the Satterlund model performed better in estimating clear-sky downward longwave radiation, and the bias (BIAS) and root mean square error (RMSE) were -23.34 and 28.55 W· m(-2), respectively. Although the coefficients were not significantly changed, the performance of Satterlund model was significantly improved after the locally calibrated, and the BIAS and RMSE decreased to -6.33 and 18.08 W · m(-2), respectively. Jacobs model was found to be best for modeling cloudy-sky downward long-wave radiation and the BIAS and RMSE were 0.38 and 29.29 W · m(-2), respectively. Sensitivity analysis showed that the vapor pressure was the most sensitive variable to the atmospheric emissivity and the temperature was not sensitive to it. The predicted results of the optimal model (clear- and cloudy-sky) were consistent with the measured data, while the performance of these models was affected by a sudden change of cloudy cover.

[Diurnal and seasonal variations of energy balance over Horqin meadow].

Based on the measurements of eddy flux and micrometeorological factors, this paper analyzed the diurnal and seasonal variations of energy balance over Horqin meadow. The results showed that annual energy balance ratio (EBR) of the eddy covariance system was 0.77, and EBR was biggest in growing season, middle in bare soil period and smallest in snow-covered period. Diurnal variations of energy components all presented bell-shaped curves. The peak of net radiation appeared around 12:00 and peaks of other components slightly lagged. Seasonal variation of net radiation presented a single-peak curve, and the annual average was 5.71 MJ x m(-2) x d(-1). Seasonal variation of latent heat flux was similar to that of net radiation, and the annual average was 2.84 MJ x m(-2) x d(-1). Seasonal variation of sensible heat flux presented a double-peak curve, and the peaks appeared in April and September, respectively. Annual averaged sensible heat flux was 1.87 MJ x m(-2) x d(-1). Maximum soil heat flux (3.47 MJ x m(-2) x d(-1)) appeared in April, and the soil heat flux became negative after September. Annual budget ratios of energy components presented a decreasing order of latent heat flux, sensible heat flux and soil heat flux, which accounted for 49.8%, 35.8% and 3.1% of net radiation, respectively. Seasonal variation of Bowen ratio (beta) presented a 'U' shape, and the annual average was 1.61. beta was small (0.18) and relatively stable in growing season, while it was large (2.39) and fluctuated severely in non-growing season.

[Spatiotemporal variation characteristics and related affecting factors of actual evapotranspiration in the Hun-Taizi River Basin, Northeast China].

Based on the meteorological and hydrological data from 1970 to 2006, the advection-aridity (AA) model with calibrated parameters was used to calculate evapotranspiration in the Hun-Taizi River Basin in Northeast China. The original parameter of the AA model was tuned according to the water balance method and then four subbasins were selected to validate. Spatiotemporal variation characteristics of evapotranspiration and related affecting factors were analyzed using the methods of linear trend analysis, moving average, kriging interpolation and sensitivity analysis. The results showed that the empirical parameter value of 0.75 of AA model was suitable for the Hun-Taizi River Basin with an error of 11.4%. In the Hun-Taizi River Basin, the average annual actual evapotranspiration was 347.4 mm, which had a slightly upward trend with a rate of 1.58 mm · (10 a(-1)), but did not change significantly. It also indicated that the annual actual evapotranspiration presented a single-peaked pattern and its peak value occurred in July; the evapotranspiration in summer was higher than in spring and autumn, and it was the smallest in winter. The annual average evapotranspiration showed a decreasing trend from the northwest to the southeast in the Hun-Taizi River Basin from 1970 to 2006 with minor differences. Net radiation was largely responsible for the change of actual evapotranspiration in the Hun-Taizi River Basin.

[Accuracy evaluation of the TRMM satellite-based precipitation data over the mid-high latitudes].

Satellite-based precipitation product plays a significant role in analyzing spatial pattern of precipitation. TRMM 3B42 (3B42), as one of important precipitation products, is a key forcing factor for ecological, climate and hydrological models with its sufficient spatial and temporal scales. At present, there is still limited knowledge of accuracy and error structure of new version 3B42 V7, especially the lack of evaluating its accuracy in regions of mid-high latitudes, which restricts its application in the field of ecology, climate and hydrology. Based on 3B42 V7 product and data obtained from 53 weather stations in the period of 1998-2012 over Inner Mongolia, the paper evaluated the accuracy of 3B42 and revealed the spatial distribution of accuracy evaluation indices and its influencing factors. The result of overall accuracy evaluation indicated that there was overestimation of the amount of precipitation by 3B42 at daily, monthly and annual timescales. Error of 3B42 increased with the increasing timescale, and mean error and mean absolute error of daily precipitation were just -0.06 and 0.88 mm, respectively. It showed good performance for detecting the occurrence of rain events with equitable threat score (ETS) of 0.23, but slightly overestimated the frequency of rainy events. Moreover, altitude and average annual precipitation had impacts on data accuracy. The absolute error of precipitation decreased and yet the ability of detecting rain events be- came weak with the increasing altitude, while the effect of average annual precipitation on data accuracy was opposite.

[Characteristics of evaporation over broadleaved Korean pine forest in Changbai Mountains, Northeast China during snow cover period in winter].

Based on the measurement data of water vapor flux by open-path eddy covariance system and of the micrometeorological factors in broad-leaved Korean pine forest in Changbai Mountains during the snow cover period from 2002 to 2005, this paper analyzed the dynamics of snow cover evaporation and the relationships between the evaporation and meteorological factors. The energy balanced ratio during the snow cover period was 79. 9% , and the latent heat flux accounted for 21. 4% of net radiation. The diurnal variation of the evaporation presented a single-peak curve, and the evaporation rate during snow-melting period was higher than that during stable snow cover period. The half-hour evaporation presented liner relationship with net radiation and quadratic relationship with air temperature. The daily evaporation presented quadratic relationship with net radiation and exponential relationship with air temperature. The daily evaporation presented a dynamic trend of decreasing-stable-increasing, with the maximum at increasing stage and the minimum at stable stage. The maximum value of the daily evaporation was 0.73 mm d-1, and the minimum value was 0. 004 mm d-1. During the snow cover periods of 2002-2003, 2003-2004 and 2004-2005, the annual evaporation was 27.6, 25.5, and 22.9 mm, accounting for 37.9% , 19.5% , and 30. 0% of the precipitation in the same periods, respectively. The mean value of the daily evaporation in the three periods was 0. 17, 0. 19, and 0. 17 mm d-1, respectively.

[Research progress on photosynthesis regulating and controlling soil respiration].

To understand the mechanisms of soil respiration and accurately estimate its magnitude are the crucial basis of evaluating global carbon balance. However, the previously built soil respiration forecast models usually neglect the physiological processes that photosynthesis supplies substrates for rhizospheric respiration, leading to the defect in evaluating the mechanisms of soil respiration. This paper summarized the research progress on the mechanisms of photosynthetic regulation and control of soil respiration, introduced the related main research methods, and discussed the existing problems and research hotspots.

[Runoff process in forested basin of Hun River-Taizi River, Northeast China: a simulation study].

Based on the hydrological data from the Beikouqian and Nandianyu stations in the upstream of Hun River and Taizi River as well as the meteorological data from the Qingyuan, Xinbin, and Benxi County stations, Northeast China in 1998-2007, a distributed hydrological model (DHS-VM) was applied to simulate the hydrological process in Hun-Tai basin. The scientific applicability of the model was validated, and the reference values of the most sensitive model parameters were provided. The simulated monthly runoff Nash-Suttclife coefficient (E value) for the source region of Hun River in calibration period (1998-2002) and validation period (2003-2007) was 0.9675 and 0. 8957, respectively, which could better reappear the monthly runoff process in this source region. The simulated monthly and annual runoff E values for the upstream of Taizi River were greater than 0.6, indicating that this model had good applicability in Hun-Tai basin, and the calibrated parameter scheme had a good reliability. This paper established a solid framework for the hydrological study over ungauged basin, and constructed a reasonable parameter scheme.

[Measurement and estimation methods and research progress of snow evaporation in forests].

Accurate measurement and estimation of snow evaporation (sublimation) in forests is one of the important issues to the understanding of snow surface energy and water balance, and it is also an essential part of regional hydrological and climate models. This paper summarized the measurement and estimation methods of snow evaporation in forests, and made a comprehensive applicability evaluation, including mass-balance methods (snow water equivalent method, comparative measurements of snowfall and through-snowfall, snow evaporation pan, lysimeter, weighing of cut tree, weighing interception on crown, and gamma-ray attenuation technique) and micrometeorological methods (Bowen-ratio energy-balance method, Penman combination equation, aerodynamics method, surface temperature technique and eddy covariance method). Also this paper reviewed the progress of snow evaporation in different forests and its influencal factors. At last, combining the deficiency of past research, an outlook for snow evaporation rearch in forests was presented, hoping to provide a reference for related research in the future.

[Canopy conductance characteristics of poplar in agroforestry system in west Liaoning Province of Northeast China].

By using Granier' s thermal dissipation probe, the sap flow of poplar in a poplar-maize agroforestry system in west Liaoning was continuously measured, and as well, the environmental factors such as air temperature, air humidity, net radiation, wind speed, soil temperature, and soil moisture content were synchronically measured. Based on the sap flow data, the canopy conductance of poplar was calculated with simplified Penman-Monteith equation. In the study area, the diurnal variation of poplar' s canopy conductance showed a "single peak" curve, whereas the seasonal variation showed a decreasing trend. There was a negative logarithm relationship between the canopy conductance and vapor pressure deficit, with the sensitivity of canopy conductance to vapor pressure deficit change decreased gradually from May to September. The canopy conductance had a positive relationship with solar radiation. In different months, the correlation degree of canopy conductance with environmental factors differed. The vapor pressure deficit in the whole growth period of poplar was the most significant environmental factor correlated with the canopy conductance.