[A new assessment method for the quality of ecological monitoring data: taking CERN's tree growth dataset as a case].

This paper presented a new and simple assessment method for the quality of ecological monitoring data. This method theorized the associations between the data reliability as an ordinal variable with different number of classes and the data sources such as natural main ecological processes, secondary ecological processes, and extraneous and exotic processes, and offered a new data quality index to estimate the quality of the whole dataset by using the reasonableness ratio of observations. The assessment results provided the reliability class of each dataset, good explanations for outlier (or error data) flagging decisions, and quality value of the whole dataset. The method was applied to assess two tree growth datasets from Chinese Ecosystem Research Network (CERN), and the results demonstrated that the new data quality index could quantitatively evaluate the quality of the tree growth datasets. The new method would facilitate the development of corresponding software.

[Soil active organic matter in broadleaved forest and Chinese fir plantation in subtropical region of China].

A comparative study was made on the soil active organic matter in a broadleaved forest and two Chinese fir (Cunninghamia lanceolata) plantations in subtropical region of China, aimed to understand the effects of forest conversion and continuous plantation on soil organic C and nutrient status. After the conversion from broadleaved forest to Chinese fir plantation, the contents of soil total organic C, humus C, humic acid, and fulvic acid decreased by 27.8%-52.1%, 32.2%-52.8%, 36.4%-59.0%, and 29.7%-50.0%, respectively. Continuous plantation also resulted in the decrease of soil organic C and humus contents. The contents of soil total organic C, humus C, humic acid, and fulvic acid in second generation of Chinese fir plantation were 9.0%-25.0%, 25.0%-38.0%, 28.6%-39.2% and 23.1%-36.4% lower than those in the first generation of Chinese fir plantation, respectively. More obvious effects were observed on the soil active organic matter. After the conversion from broadleaved forest to Chinese fir plantation, the maximum decrement of soil microbial biomass C and N and dissolved organic C and N was 61.8%, 38.2%, 43.3%, and 69.0%; while comparing with the first generation of Chinese fir plantation, the second generation of Chinese fir plantation had the maximum decrement of soil microbial biomass C and N and dissolved organic C and N being 34.7%, 29.3%, 30.4%, and 18.4%, respectively. Soil nutrient contents also decreased due to forest conversion and continuous plantation. In comparing with broadleaved forests, Chinese fir plantations had a decrease of soil N, P, and K contents being 15.7%-31.2%, 11.5%-49.3%, and 15.1%-33.8%, respectively. There were close relationships between soil nutrients and soil active organic matter fractions except cold water extractable organic N.

[Effects of root system and litter of Chinese fir on soil microbial properties].

A simulation test was conducted to study the effects of the root system and litter of Chinese fir (Cunninghamia lancceolata) on soil microbial properties. After the amendment with C. lancceolata root system, the soil microbial biomass C, basal respiration, total organic C, and microbial quotient increased significantly (P < 0.05), while soil metabolic quotient (qCO2) presented an opposite trend. In the treatment amended with C. lancceolata litter, the soil basal respiration and qCO2 decreased significantly (P < 0.05), whereas soil microbial biomass C, total organic C, and microbial quotient had less change. A significant interaction between C. lancceolata root system and litter was observed on soil basal respiration and qCO2. The qCO2 had significant positive correlations with soil total organic C (R2 = 0.209) and dissolved organic C (R2 = 0.325), suggesting that the C use efficiency of soil microbes decreased with increasing soil organic C content. Comparing with litter, the root system of C. lancceolata played more important roles in soil ecological processes.