Rapid response of hydrological loss of DOC to water table drawdown and warming in Zoige peatland: results from a mesocosm experiment.

A large portion of the global carbon pool is stored in peatlands, which are sensitive to a changing environment conditions. The hydrological loss of dissolved organic carbon (DOC) is believed to play a key role in determining the carbon balance in peatlands. Zoige peatland, the largest peat store in China, is experiencing climatic warming and drying as well as experiencing severe artificial drainage. Using a fully crossed factorial design, we experimentally manipulated temperature and controlled the water tables in large mesocosms containing intact peat monoliths. Specifically, we determined the impact of warming and water table position on the hydrological loss of DOC, the exported amounts, concentrations and qualities of DOC, and the discharge volume in Zoige peatland. Our results revealed that of the water table position had a greater impact on DOC export than the warming treatment, which showed no interactive effects with the water table treatment. Both DOC concentration and discharge volume were significantly increased when water table drawdown, while only the DOC concentration was significantly promoted by warming treatment. Annual DOC export was increased by 69% and 102% when the water table, controlled at 0 cm, was experimentally lowered by -10 cm and -20 cm. Increases in colored and aromatic constituents of DOC (measured by Abs(254 nm), SUVA(254 nm), Abs(400 nm), and SUVA(400 nm)) were observed under the lower water tables and at the higher peat temperature. Our results provide an indication of the potential impacts of climatic change and anthropogenic drainage on the carbon cycle and/or water storage in a peatland and simultaneously imply the likelihood of potential damage to downstream ecosystems. Furthermore, our results highlight the need for local protection and sustainable development, as well as suggest that more research is required to better understand the impacts of climatic change and artificial disturbances on peatland degradation.

Dynamics and sources of soil organic C following afforestation of croplands with poplar in a semi-arid region in northeast China.

Afforestation of former croplands has been proposed as a promising way to mitigate rising atmospheric CO2 concentration in view of the commitment to the Kyoto Protocol. Central to this C sequestration is the dynamics of soil organic C (SOC) storage and stability with the development of afforested plantations. Our previous study showed that SOC storage was not changed after afforestation except for the 0-10 cm layer in a semi-arid region of Keerqin Sandy Lands, northeast China. In this study, soil organic C was further separated into light and heavy fractions using the density fractionation method, and their organic C concentration and (13)C signature were analyzed to investigate the turnover of old vs. new SOC in the afforested soils. Surface layer (0-10 cm) soil samples were collected from 14 paired plots of poplar (Populus × xiaozhuanica W. Y. Hsu & Liang) plantations with different stand basal areas (the sum of the cross-sectional area of all live trees in a stand), ranging from 0.2 to 32.6 m(2) ha(-1), and reference maize (Zea mays L.) croplands at the same sites as our previous study. Soil ΔC stocks (ΔC refers to the difference in SOC content between a poplar plantation and the paired cropland) in bulk soil and light fraction were positively correlated with stand basal area (R (2) = 0.48, p<0.01 and R (2) = 0.40, p = 0.02, respectively), but not for the heavy fraction. SOCcrop (SOC derived from crops) contents in the light and heavy fractions in poplar plantations were significantly lower as compared with SOC contents in croplands, but tree-derived C in bulk soil, light and heavy fraction pools increased gradually with increasing stand basal area after afforestation. Our study indicated that cropland afforestation could sequester new C derived from trees into surface mineral soil, but did not enhance the stability of SOC due to a fast turnover of SOC in this semi-arid region.

[Current distribution of Schisandra chinensis in China and its predicted responses to climate change].

With integration of literature data, specimens records, and field surveys, the current distribution map of Schisandra chinensis in China was drawn, and, based on this map and considering 21 environmental factors, the future distribution of S. chinensis in China in the 2050s and 2080s under the IPCC A2 and A1B climate change scenarios was predicted by using Maxent software. Currently, the S. chinensis in China occurred in 15 provinces, involving 151 counties, and its distribution area decreased with decreasing latitude and longitude. The main distribution area included Heilongjiang, Liaoning, Inner Mongolia, and Jilin. The potential distribution area of S. chinensis in China was 145.12 x 10(4) km2, 48.6% of which were the favorable habitat area, mainly distributed in Changbai Mountains, Xiaoxing'anling Mountains, Daxing'anling Mountains, and the regions between Hebei and Liaoning provinces. The most favorable habitat area only accounted for 0.3%, and was mainly in the Kuandian Manchu Autonomous County, Benxi Manchu Autonomous County, and Huanren Manchu Autonomous County of Liaoning Province, the Antu County and Helong County of Jilin Province, and the Yakeshi City of Inner Mongolia. Under the two climate change scenarios, the potential future distribution area of S. chinensis in China would have a gradual decrease, and the decrement would be larger under A2 than under A1B scenario. By 2050, the distribution area of the S. chinensis under A1B and A2 scenarios would be moderately decreased to 84.0% and 81.5% of the current distribution area, respectively; by 2080, the distribution of S. chinensis under A2 scenario would be dramatically decreased to only 0.5% of the current range, and that under A1B scenario would be decreased to 1/2 of the current range.

[Estimation models of understory shrub biomass and their applications in red soil hilly region].

With 16 familiar species of understory shrub at Qianyezhou ecological experimental station in red soil hilly region under Chinese Academy of Sciences as test objects, crown area (A(c)) and projected volume (V(c)) were used as the variables for building quadratic and power allometric equations, respectively, to estimate the biomass of individual populations, and mixed-model was used to estimate the biomass of the 16 species. The best-fit models were applied to estimate the biomass of understory shrub in different forest types. The results showed that the biomass of shrub layer varied significantly among different stand types. With species-specific models, the biomass in deciduous, secondary, and coniferous forests was estimated as 4 773, 3 175 and 733 kg x hm(-2), respectively; while with mixed model, the estimation result was a little lower, being 3 946, 2 772 and 840 kg x hm(-2), respectively. Under the conditions of species-specific models being not established, mixed model was more convenient and practical in estimating the biomass of understory shrub.

[Aboveground biomass of three conifers in Qianyanzhou plantation].

In this paper, the regressive models of the aboveground biomass of Pinus elliottii, P. massoniana and Cunninghamia lanceolata in Qianyanzhou of subtropical China were established, and the regression analysis on the dry weight of leaf biomass and total biomass against branch diameter (d), branch length (L), d3 and d2L was conducted with linear, power and exponent functions. Power equation with single parameter (d) was proved to be better than the rests for P. massoniana and C. lanceolata, and linear equation with parameter (d3) was better for P. elliottii. The canopy biomass was derived by the regression equations for all branches. These equations were also used to fit the relationships of total tree biomass, branch biomass and foliage biomass with tree diameter at breast height (D), tree height (H), D3 and D2H, respectively. D2H was found to be the best parameter for estimating total biomass. For foliage-and branch biomass, both parameters and equation forms showed some differences among species. Correlations were highly significant (P <0.001) for foliage-, branch-and total biomass, with the highest for total biomass. By these equations, the aboveground biomass and its allocation were estimated, with the aboveground biomass of P. massoniana, P. elliottii, and C. lanceolata forests being 83.6, 72. 1 and 59 t x hm(-2), respectively, and more stem biomass than foliage-and branch biomass. According to the previous studies, the underground biomass of these three forests was estimated to be 10.44, 9.42 and 11.48 t x hm(-2), and the amount of fixed carbon was 47.94, 45.14 and 37.52 t x hm(-2), respectively.

[Interspecific association between understory species in a southern highland plantation].

Based upon 2 x 2 contingency table, chi2 test and association coefficient were used to determine the interspecific association between understory species in a southern highland plantation, and to analyze the restoration degree and the stability of southern highland vegetations originated from plantation. The Qianyanzhou in Taihe County of Jiangxi Province, a typical sample of southern highland plantation, was chosen to make the study. The results showed that both in shrub layer and in herb layer, species pair with chi2 reaching significant level (P <0.05) was few in number. In shrub layer, 12 species pairs' association was highly significant (P < 0.01), 19 pairs' was significant (P < 0.05), and other 200 pairs' was nonsignificant, while in herb layer, 11 pairs' was highly significant, 11 pairs' was significant and other 83 pairs' was nonsignificant. According to interspecific association and correlation, shrub layer was divided into two species groups: Group I . Adinandra bockiana, Syzygiumn grijsii, Vaccinium bracteatunm, Ilex aculeolata, Smilax ferox, Eurya muricata and Group II . Lespedeza davidii, Serissa serissoides, Vitex negundo var. cannabifolia. Many species in Group I had a significantly negative association with the species in Group II, and dominant species always played a key role in the relationships among species. The three dominant species in herb layer, Wooduardia japonica, Dryopteris atrata and Adiantun flabellulaturn, had a highly significant positive correlation between each other, and moreover, had a significant or highly significant positive association with many other herbaceous species. Similarily, dominant species in shrub layer played a key role on the interspecific association in the two species groups. The ratios of positive and negative association indicating the species compositions of the two layers were fluctuating, which was 125/106 in shrub layer and 42/63 in herb layer. Several shortcomings of interspecific association method were pointed out, with some proposals put forward.

Image analysis and coummunity monitoring on coniferous forest dynamics in Changbai Mountain.

The structure and dynamics of coniferous forests in Changbai Mountain were studied at different spatial scales, including ground survey of permanent plots and analysis of multitemporal satellite images. Plot-scale examinations showed that the mortality rate was 7% - 9%, and the recruitment rate was 18% - 20% per 10 years. Species composition changed over time. Picea jezoensis var. microsperma, Abies nephrolepis and Betula ermanii presented a self-maintaining capability, because they could regenerate under canopy. Larix olgensis was a pioneer species and could regenerate only in open land or gaps. This species played an important role by providing conditions for the regeneration of spruce and fir. The tree density in the mature forest was 1 000 stems x hm(-2) for trees bigger than 3 cm in diameter, which showed no significant variations among different stands. Landsat TM images were used for detecting the cover changes from 1984 to 1997. Large scales of wind throw were detected by this approach. Based on t he analysis of radiance changes at the landscape scale, the pixel number of the disturbed area was similar to that of the succeeding stands, suggesting that the forest was in a state of equilibrium. Fine gaps, however, were difficult to identify with the TM data because of its coarse resolution. The mosaic structure ofthe subalpine vegetation was characterized by scattered larch patches. At the landscape level, the vegetation was in a stable stage.

[Structures and spatial distribution patterns of dominant populations in Sycopsis sinensis community in Houhe Nature Reserve].

Based on the investigation data of 2 quadrats (1,600 m2 and 2,400 m2) in Houhe Nature Reserve, tree size class method was applied to analyze the structures of the dominant populations, and t-test of v/m ratio, mean crowing index, negative binomial parameter, patchiness index and Morisita index were applied to analyze the spatial distribution patterns of two dominant populations. The clumping degrees were also evaluated according to their size classes in different quadrats. The results showed that Sycopsis sinensis population was a declining population, dominated by IV trees and difficult to regenerate. In the population, the individual percentage of IV trees accounted for 79.4% in Q1 and 87.4% in Q2, and those of I trees and II trees were few. However, the population of Cyclobalanopsis axyodon was an growing one, and the individual percentages declined with the increasing size classes. The spatial distribution patterns of the two dominant populations distributed in clumps, but the clumping degrees existed diversity. With the increase of the size classes, the clumping degree of the population of Sycopsis sinensis intensified from random to clumping distribution, while that of the population of Cyclobalanopsis axyodon weakened from clumping to random distribution.