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Pan F.,CAS Institute of Subtropical Agriculture | Pan F.,Cuangxi Normal University | Pan F.,Chinese Academy of Sciences | Zhang W.,CAS Institute of Subtropical Agriculture | And 7 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2011

Ecological stoichiometry theory' which was put forward to investigate nutrient cycling of marine ecosystem by Reiners' has been incorporated successfully into many research fields such as decomposition dynamics' nutrient cycling and biology ecological response to global change and so on. The ratio of carbon: nitrogen: phosphorus (C:N:P) in planktonic biomass was found to be well-constrained in marine ecosystem. Some analyses indicated the existence of analogous ratios in plants' suggesting that the theory may be applicable in terrestrial ecosystems. Here we tested if the ecological stoichiometry theory is applicable to the typical Karst Peak-Cluster Depression' where our previous studies showed that soil nutrient in the upward slope was higher than in the downward slope. It was speculated that the possible reason could be that the litter carbon' nitrogen' phosphorus and carbon: nitrogen: phosphorus (C:N:P) ratio were the same as soil nutrient. It was also inferred that litter C: N: P ratio could play an important role in the decomposition and nutrient cycling of Karst forested ecosystems. In this study' the slope gradients of litter carbon' nitrogen' phosphorus and their mass ratio in four vegetation succession stages was analyzed in order to understand the spatial differentiation and ecological stoichiometry trail of litter nutrient of plant communities in the typical Karst Peak-Cluster Depression. The results of this study showed that (1) carbon, nitrogen, phosphorus and N:P ratio in litter standing crops increased from the early to the later succession stages, while the ratio of C:N and C:P decreased. (2) The content of litter carbon, ratio of C:N, C:P and N:P in upward slope were larger than that in downward slope, while the reverse trend was exhibited in phosphorus content and no significantly different nitrogen content was observed among slopes (P<0.05). The result of Canonical Correspondence Analysis (CCA) showed that the succession stages and slope position had greater impact on the litter accumulation, nutrient distribution and storage, compared to that of slope and bare rock. (3) It is known that the litter decomposition and nutrient cycling is mainly constrained by the N:P ratio. Previous research indicated that litter P concentrations and low N:P ratio did not limit decomposition, but litter N concentrations and high N:P ratios showed contrary results. The lack of significant differences among N elements among slopes and significant difference of P elements reflected that the fluctuations of P content affected vegetation litter N:P ratio and the changing decomposition rate in typical Karst Peak-Cluster Depression. Lower N and high lignin content (namely higher N:P ratio) under the case of low P leading decomposition rate become lower, thus lower N:P ratio is easy for litter decomposition. It is presumed that litter decomposed faster in the downward slope and in young-growth plant communities than that in the upward slope and in old-growth plant communities due to the lower N:P ratio. As a result, less litter nutrient was stored in the downward slope and in young-growth plant communities. Therefore, litter in the upward slope, old-growth forests were conducive to the accumulation of nutrients.

Liu S.-J.,CAS Institute of Subtropical Agriculture | Liu S.-J.,Chinese Academy of Sciences | Liu S.-J.,University of Chinese Academy of Sciences | Zhang W.,CAS Institute of Subtropical Agriculture | And 6 more authors.
Chinese Journal of Applied Ecology | Year: 2010

Soil samples were collected from the grassland, shrub land, secondary forest, and original forest on the hill slope in a typical karst peak-cluster depression area of northwest Guanxi, with the spatiotemporal heterogeneity of soil physical properties investigated by classical statistics, and the formation causes of the heterogeneity analyzed by redundancy analysis (RDA). In 0-15 cm soil layer, the clay (<0.002 mm) and silt (0.002-0.05 mm) contents of shrub land and original forest had significant differences with those of grassland and secondary forest, respectively, but the clay, silt, and sand (0.05-2.0 mm) contents had no significant differences between grassland and secondary forest. No significant difference was observed in the soil sand content among the four land types, but the soil bulk density of grassland was significantly different from that of other three land types. The soil clay content of grassland increased with increasing elevation, while that of the other three land types was the highest on medium slope, and had no significant differences for the same land types among different slope locations. The soil clay content in different layers of 0-30 cm had a greater variation extent in original forest (14.55%) than in grassland (7.12%), shrub land (11.24%), and secondary forest (13.77%), and the soil particle size composition was greatly affected by the disturbance of human activities. Soil organic carbon (SOC) and vegetation type were the dominant factors affecting the soil physical properties, and the bare rock ratio had greater effects on soil sand content.

Liu S.,CAS Institute of Subtropical Agriculture | Liu S.,Chinese Academy of Sciences | Liu S.,University of Chinese Academy of Sciences | Zhang W.,CAS Institute of Subtropical Agriculture | And 9 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2011

Spatiotemporal heterogeneity of soil nutrients was put forward to indicate the distribution and changes of soil nutrients. Comparing with non-karst regions, former studies had shown that soil nutrients were inversed in karst peak-cluster depression, namely nutrient-inversion. The reasons for nutrients inversion in karst peak-cluster depression were obscure. Therefore, this study aimed to explore the impacts of vegetation succession and topographical attributes on surface soil nutrients and validate whether it is universal for nutrients inversion. An experiment was designed to compare the distribution of soil nutrients under three mainly vegetations to theoriginal forest. In order to explore the temporal and spatial variability of soil nutrients and its controlling factors, the soil samples of topsoil (0-15cm) were collected in two typical Karst peak-cluster with four vegetation succession stages (grassland, shrubland, plantation forest, original forest) in northwest Guangxi, southwest China. A total of 202 samples were collected from twelve sampling lines (each vegetation type had three sample lines for comparison), including 48 grassland samples, 46 shrubland samples, 44 plantation forest samples and 64 original forest samples. Analysis of variance (ANOVA) was utilized to analyze the differences of topsoil nutrient contents for different vegetation types and topographical attributes, respectively. The results showed that there were significant differences of topsoil nutrients (soil organic carbon, total nitrogen, carbon/nitrogen ratio, total phosphorus, total potassium, available nitrogen, available phosphorus, and available potassium) and soil pH values among different vegetation succession stages. Except for the total potassium, other nutrient contents increased with vegetation succession. The slope position had different effects on soil nutrient contents. Many influencing factors affected the variability of nutrients at the same time, such as human disturbance and its intensity, soil physical properties, vegetation community, ground litter and so on. Carbon and nitrogen of original forest, as well as phosphorus and potassium of other vegetation succession stages, was accorded with the "nutrient depression effect", which meant that nutrient reduced with the increase of elevation. In addition, carbon and nitrogen of grassland, shrubland and artificial forest increased with elevation. It was due to the disturbance of human activities. In addition, Our study indicates that vegetation succession plays a positive role in soil nutrient accumulation and thegovernment should keep on carrying out to protect vegetation from human disturbance. Phosphorus (available phosphorus 3.55-11.41 mg/kg) and potassium (available potassium 64.05-105.75 mg/kg) are always limiting nutrient factors in karst peak-cluster depression regions. Additionally, nutrient-inversion is not a common phenomenon and if there was no interference of human, the distribution of soil nutrients in Karst peak-cluster depression will accord with other regions, following the "nutrient depression effect".

Shu S.-Y.,CAS Institute of Subtropical Agriculture | Shu S.-Y.,Chinese Academy of Sciences | Shu S.-Y.,University of Chinese Academy of Sciences | Wang K.-L.,CAS Institute of Subtropical Agriculture | And 9 more authors.
Chinese Journal of Ecology | Year: 2010

This paper studied the variation pattern of soil alkaline phosphatase activity and its relationships with soil physical and chemical properties at four different stages of vegetation succession in a typical karst peak-cluster depression of northwest Guangxi, China. Succession stage and soil depth had significant effects on the soil alkaline phosphatase activity, but slope position had less effects. During the succession of original forest-secondary forest, bush forest-grass, and with the increase of soil depth, the soil alkaline phosphatase activity decreased, and had significant difference among different soil layers. The soil alkaline phosphatase activity had significant positive correlations with soil pH and soil organic matter, total N and P, available N, P, and K, silt, and sand contents, and significant negative correlations with soil bulk density and soil total K and clay contents. The canonical correspondence analysis (CCA) showed that succession stage and bare rock rate had primary effects on soil alkaline phosphatase activity, while slope gradient, slope position, and slope direction also had great effects on it.

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