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Planting shrubs on sand land and degraded pasture are two main measures for desertification control particularly in northwest China. However, their effects on soil organic carbon (SOC) and its fractions remain uncertain. We assessed the changes in stocks of SOC, light fraction of SOC (LF–SOC) and heavy fraction of SOC (HF–SOC) after planting Artemisia ordosica (AO, 17 years), Astragalus mongolicum (AM, 5 years) and Salix psammophila (SP, 16 years) in sand land and planting Caragana microphylla (CM, 24 years) on degraded pasture. Results show that: 1) after planting AO, AM and SP on sand land, SOC stocks increased by 162.5%, 45.2% and 70.8%, respectively, and LF–SOC accounted for a large proportion in the increased SOC. Dry weights of LF–SOC, rather than carbon concentrations, were higher in shrublands than that in sand land; 2) after planting CM on degraded pasture, SOC stock decreased by 9.3% and all the loss was HF–SOC in 60–100 cm soil layer where both herbaceous fine root biomass (HFRB) and soil water content (SWC) also decreased. The results indicate that planting shrubs can result in an increase of SOC in sand land, whereas that can lead to a decrease of SOC in degraded pasture. The increase of SOC in sand land mainly bases on the accumulation of dry weight of LF–SOC. The loss of SOC in degraded pasture is caused by the decrease of carbon concentrations of HF–SOC, which can be related to the reduction of HFRB and SWC in deep soil layer. Therefore, shrub-planting for desertification control not always improve the quantity and stability of SOC in northwest China.
The investigations were carried out in the years 2000- -2004 on permanent grassland in Czarny Potok (Beskidy Mts.- 650 a. s. 1.). Botanical census was conducted by using Klapp’s method on 26 plots (18 random selected plots and 8 controls). The whole floristic material was subjected to numerical classification. As a result, three main types of plots with the dominating species of: Juncus effusus (1), Cirsium arvense (2) and Deschampsia caespitosa (3), were distinguished. Poa trivialis was the dominating species of the control plots. Results of the floristic and habitat analysis confirmed that the main factors determining the formation of meadow and pasture communities are as follows: the method of use, water relations and soil nutrient availability. It was found that idle glades are characterised by degraded sward of the average (the sward patches with the domination of Deschampsia caespitosa) or low use value (the swards patches with the domination of Cirsium arvense and Juncus effusus). The deterioration of the feeding value of the fallow plots is an effect of their high weed infestation, which in turn results, in this case, from habitat changes as a consequence of the cessation of use and earlier errors made in cultivation measures. Both high and low soil moisture, with improper meadow management, accelerated the weed infestation of the sward, what in turn lowers its use value. Cutting and fertilisation positively affect the use value of plant habitats, what was confirmed by the botanical and habitat analysis of the control plots with the domination of Poa trivialis, which is known to be of good use value.
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