The methane (CH₄) fluxes in grasslands are sensitive to changes in precipitation and soil nitrogen concentrations, which was poorly understood, especially on the Tibetan Plateau. Therefore, an experiment was conducted from May 2012 to October 2013, by using the static chamber technique and gas chromatography method. We set up five treatments: an increased 2 g m^-2 NH₄NO₃ treatment (2gN); an increased 4 g m^-2 NH₄NO₃ treatment (4gN); and treatment with precipitation increased by 20% (Pre), and added 2 g m^-2 NH₄NO₃ and precipitation (20%) treatment (N+Pre), and a control treatment (CK). The five treatments showed decreasing CH₄ uptake rates in the following order: CK (71.66 ± 6.6 µg m^-2 h^-1) > N+Pre (58.57 ± 3.7 µg m^-2 h^-1) > Pre (52.66 ± 2.3 µg m^-2 h^-1) > 2gN (47.63 ± 3.1 µg m^-2 h^-1) > 4gN (39.12 ± 3.3 µg m^-2 h^-1). The 2gN and 4gN treatment resulted in 33.5% and 45.4% lower CH₄ uptake than the CK treatment, respectively. The path analysis indicated that the above-ground biomass and litter fall were the most important factor promoting and limiting the CH₄ uptake rate of alpine meadow, respectively.

The effects of changing precipitation and wind regimes on plant physiology are increasingly drawing attention of eco-physiologists. In the manipulative experiment we studied the physiological mechanisms of annual C4 herbs in the semi-arid sandy land to understand the functional significance of their traits and responses to the changing environment, grass Setaria viridis, characterized by the moderate stem water content and low leaf water content, more effectively absorbed light energy and utilized water resources than two dominant dicot plants, Salsola collina and Bassia dasyphylla. Precipitation increase and wind reduction promoted photosynthesis of the three C4 herbaceous plants, and their photosynthetic rates were higher in the end of July than that in August. Precipitation increase and the 20% reduction in wind velocity could also enhance their stomatal conductance and transpiration rate. The transpiration rate was consistent with the change in stomatal conductance, exhibiting highly positive correlation. The interactive effects of precipitation increase and wind velocity reduction made great changes in photosynthetic rate of the S. collina, lifted the photosynthetic rate and water use efficiency of the S. viridis. Our results suggest that the C4 herbs have shown some degree of stress resistance, and they are able to acclimate better to frangible environment of semi-arid sandy land. Furthermore, the changing environments heighten photosynthesis of the C4 herbs, which is pretty important to strength the arid plant stress resistance, then contributed to the ecosystem community production and dry matter accumulation.

Soil particle size distribution (PSD) is becoming an increasingly useful tool for the objective description of soil structure and intrinsic links between soil and the environment. Here we examined the fractal features of PSD and its correlation with soil physiochemical properties in grasslands under grazing and protected from grazing (enclosure) animals, before and after plant growing periods in a semiarid grassland ecosystem, in northern China. Our results showed that sand content was significantly higher in grassland soils under grazing compared with the enclosure at both sampling times (May and September), whereas their silt and clay contents followed the reverse pattern. The fractal dimensions of PSD (D_m) under enclosure were significantly greater than those found under grazing. The soil clay, silt contents and Dm were positively correlated with soil total N, total C, soil pH, and moisture content. By contrast, the soil sand content declined with increasing total N, total C, pH, and moisture content of soil. The soil fractal dimension of PSD had a positive correlation with soil clay and silt content, whereas it had a negatively correlated with sand content. From these results, we conclude installing enclosures can promote soil clay, silt, and soil particles' fractal dimension, with the latter could be used as a quantitative indicator of soil fertility characteristics. But it is unnecessary to use the fractal dimension of PSD as an index to evaluate the effects of enclosure management on degraded grassland.

Forest structure in Europe has been shaped by forest management which may vary from intensive clearcuttings to single-tree selection cuttings. Most investigations on silver fir forests have been carried out in the mountains. Forests in lowlands have been less studied, although many of them are of natural origin. We investigated and assessed potential stand structural differences between managed and partially protected mixed silver fir stands. We also assessed the impact of silvicultural activities that led to the development of current stand structures of mixed Abies alba stands. The study was conducted in Janów Forests in south-eastern Poland. We randomly established 40 circular nested plots in three managed and three partially protected stands. Although both managed and partially protected stands differed in the intensity of management and the type of selection cuttings, we found little difference in the composition and stand structure. Regardless of management intensity all stands were characterized by diversified natural regeneration, where the main tree species, especially in the phase of seedlings, was silver fir. The basal area of standing dead trees was higher for the protected than managed stands, but the differences were not significant, whereas the mean volume of dead standing trees was significantly higher in the reserve. Both in managed and protected stands, silver fir benefited from the management measures mimicking natural processes. Our results suggest that low intensity forest management for silver fir dominated forests will be crucial for conserving these forests and their unique structure in the region.

Pinus cembra forests are limited to the Alps and Carpathians. Although several studies regarding their structure were carried out in some locations in the Tatra Mts. it required further investigations. Therefore, the aims of this study were to describe the stand and shrub structure of P. cembra forests, compare their structure with the Picea abies forests and analyse differences between silicate and calcicolous P. cembra forests in the Tatra Mts. The data were collected on the 16 sampling plots (500 m²), in the Swiss stone pine and Norway spruce forests. We measured the diameter at breast height (dbh) of each tree and recorded the young trees and shrubs. In order to compare species composition between silicate and calcicolous P. cembra forests, we made 91 relevés in their entire range of distribution (917 ha). Furthermore, we examined the share of main tree species along the altitude and inclination gradients, using the GAM models. The tree density in the P. cembra forests reaches 618 stems per ha, whereas their basal area (BA) 23.17 m² ha^-1. Main tree species are P. cembra and P. abies. P. cembra dominates in the higher thickness classes. The BA and dbh structure varies significantly between P. cembra and P. abies forests. The most abundant juveniles are P. abies and Sorbus aucuparia. The differences between forests growing on different substrate are relatively low. The altitude has a significant impact on the share of P. cembra (increase) and P. abies (decrease). The inclination has a significant impact on the increase of share of P. cembra.

In a small-scale field experiment, we estimated the contribution of aboveground litter to the energy budget of different collembolan and earthworm species. In a 50-year-old spruce plantation, the natural spruce litter was replaced by an equivalent amount of maize litter. The natural difference in the isotopic composition of carbon (C) between the spruce and maize allowed us to estimate the proportions of different carbon sources in the tissues of soil animals. The dependence on litter-derived C was least pronounced in Collembola having low δ¹⁵N values, indicating the feeding on non-vascular plants. In contrast, collembolans having high δ¹⁵N values belonged to the food chains based on fresh plant residuals. These results suggest that different species of litter-dwelling collembolans may regulate substantially different energy channels. Some species of endogeic earthworms (Aporrectodea rosea and A. caliginosa) utilize aboveground plant residues, though soil organic matter and other belowground sources of carbon prevail in the energy budget of their populations.