Remote Sensing Monitoring of the Subalpine Coniferous Forests and Quantitative Analysis of the Characteristics of Succession in East Mountain Area of Tibetan Plateau——A Case Study With Zamtang County

The study area lies in the Dadu River drainage area in upstream Yangtze River.The spatial distribution of subalpine coniferous forests in 1989 and 2009 was extracted by means of a combined method of object orientation and visual interpretation,and then the overlaying analysis of these data was conducted.The type and spatial location of succession were discovered and served as the sample of dependant variable.Meanwhile,supported by GIS technology and based on DEM and thematic data,the eight variables including altitude,slope,sin and cosin of aspect,curvity of land surface,and distance to residential area,cultivated land and road were extracted served as the sample of spatial succession of subalpine coniferous forests to fit Logistic Regression,and then the contribution of each independent variable as well as the spatial property of the occurrence probability of succession was calculated.The results suggested that,during the succession of subalpine coniferous forests to meadow,the closer to the residential area and cultivated land,the greater the contribution to succession is.In particular,when the distance to the residential area decreases by one unit,the probability for its conversion to meadow will be increased by 1.15 times.During the succession of subalpine coniferous forests to deciduous-broadleaved shrubs,the sin of aspect and distance to residential area contribute more,and the probability of succession increases with increasing degree of northwardness,i.e.when the degree of northwardness increases by one unit,the probability will be increased by 1.2 times.The quantitative analysis of spatial succession property of subalpine coniferous forests will supply scientific basis to the protection and restoration of subalpine coniferous forests.

Nutrient and Litter Patterns in Three Subalpine Coniferous Forests of Western Sichuan, China

Investigations were conducted to quantify litterfall, and litter and nutrient accumulation in forest floor, and to acquire information on litter decomposition and nitrogen and phosphorus release patterns in three different subalpine coniferous forests, a plantation （P1）, a secondary forest （SF）, and a primitive forest （PF）, in western Sichuan, China. The litter trap method was used to evaluate litterfall with the litterbag method being utilized for litter decomposition. Seasonal patterns of litterfall were similar in the three forests, with two peaks occurring in September-November and March-May. The plantation revealed an annual litterfall of 4.38 x 103 kg ha-1, which was similar to those of SF and PF, but P1 had a lower mass loss rate and a higher C/N ratio. The C/N ratio may be a sound predictor for the decomposition differences. N concentrations of leaf litter in both the secondary forest and primitive forest increased first and then decreased, and the percentages of their final/initial values were 108.9% and 99.9%, respectively. P concentration in the three forests increased by the end of the study. The results of litterfall and decomposition indicated that in the plantation the potential to provide nutrients for soil organic matter was similar to those of SF and PF; however, its slower decomposition rate could result in a somewhat transient accumulation of litter in the forest floor.

Response of clonal plasticity of Fargesia nitida to different canopy conditions of subalpine coniferous forest

The aim of this study is to explore the effects of canopy conditions on clump and culm numbers,and the morphological plasticity and biomass distribution patterns of the dwarf bamboo species Fargesia nitida.Specifically,we investigated the effects of canopy conditions on the growth and morphological characteristics of F.nitida,and the adaptive responses of F.nitida to different canopy conditions and its ecological senses.The results indicate that forest canopy had a significant effect on the genet density and culm number per clump,while it did not affect the ramet density.Clumps tended to be few and large in gaps and forest edge plots,and small under forest understory plots.The ramets showed an even distribution under the closed canopy,and cluster distribution under gaps and forest edge plots.The forest canopy had a significant effect on both the ramets’biomass and biomass allocation.Favourable light conditions promoted ramet growth and biomass accumulation.Greater amounts of biomass in gaps and forest edge plots were shown by the higher number of culms per clump and the diameter of these culms.Under closed canopy,the bamboos increased their branching angle,leaf biomass allocation,specific leaf area and leaf area ratio to exploit more favourable light conditions in these locations.The spacer length,specific spacer length and spacer branching angles all showed significant differences between gaps and closed canopy conditions.The larger specific spacer length and spacer branching angle were beneficial for bamboo growth,scattering the ramets and exploiting more favourable light conditions.In summary,this study shows that to varying degrees,F.nitida exhibits both a wide ecological amplitude and high degree of morphological plasticity in response to differing forest canopy conditions.Moreover,the changes in plasticity enable the plants to optimize their light usage efficiency to promote growth and increase access to resources available in heterogeneous light environments.

Streamwater chemistry and flow dynamics along vegetation-soil gradient in a subalpine Abies fabri forest watershed, China

Streamwater chemistry and spatial flow dynamics from a subalpine Abies fabri forest in an experimental watershed located in the east slope of Gongga Mountain were analyzed to gain insights into the gradient effect of primary community succession on the stream biogeochemical process. Results showed that high sand content(exceeding 80%) and porosity in the soil(exceeding 20% in A horizon and 35% in B horizon), as well as a thick humus layer on the soil surface, made the water exchange quickly in the Huangbengliu(HBL) watershed. Consequently, no surface runoff was observed, and the stream discharge changed rapidly with the daily precipitation. The flow trends of base ions in the stream water were influenced by the Abies fabri succession gradient. Ca 2+ , HCO - 3 and SO 2- 4 were the dominant anions in the streamwater in this region. A significant difference of Ca 2+ , HCO - 3 and SO 2- 4 concentration exported between the succession stages in the watershed can be found. But they had the similar temporal change in the stream flow. Ca 2+ , HCO - 3 and SO 2- 4 showed significantly negative correlations with the daily precipitation and the stream discharge. \;Concentrations of Cl -, Na +, K +, and Mg 2+ were low in all streamwaters monitored and we observed no differences along the Abies fabri succession gradient. Low ratios of Na:(Na+Ca) (range from 0.1 to 0.2) implied cations were from bedrock weathering(internal source process in the soil system) in this region. But, a variance analysis showed there were almost no differences between rainwater and streamwaters for Mg 2+ , Na +, K +, and Cl - concentrations. This indicated that they might be come from rainfall inputs(external source). The highly mobile capacity, rapid water exchange between precipitation and discharge, and long-term export lead to this observed pattern were suggested.