Chuntan Han

Distribution and Estimation of Aboveground Biomass of Alpine Shrubs along an Altitudinal Gradient in a Small Watershed of the Qilian Mountains, China

Shrublands serve as an important component of terrestrial ecosystems, and play an important role in structure and functions of alpine ecosystem. Accurate estimation of biomass is critical to examination of the productivity of alpine ecosystems, due to shrubification under climate change in past decades. In this study, 14 experimental plots and 42 quadrates of the shrubs Potentilla fruticosa and Caragana jubata were selected along altitudes gradients from 3220 to 3650 m a.s.l. (above sea level) on semi-sunny and semi-shady slope in Hulu watershed of Qilian Mountains, China. The foliage, woody component and total aboveground biomass per quadrate were examined using a selective destructive method, then the biomass were estimated via allometric equations based on measured parameters for two shrub species. The results showed that C. jubata accounted for 1 — 3 times more biomass (480.98 g/m2) than P. fruticosa (191.21 g/m2). The aboveground biomass of both the shrubs varied significantly with altitudinal gradient (P<0.05). Woody component accounted for the larger proportion than foliage component in the total aboveground biomass. The biomass on semi-sunny Received: 2 January 2014 Accepted: 19 May 2014 slopes (200.27 g/m2 and 509.07 g/m2) was greater than on semi-shady slopes (182.14 g/m2 and 452. 89 g/m2) at the same altitude band for P. fruticosa and C. jubata. In contrast, the foliage biomass on semi-shady slopes (30.50 g/m2) was greater than on semi-sunny slopes (27.51 g/m2) for two shrubs. Biomass deceased with increasing altitude for P. fruticosa, whereas C. jubata showed a hump-shaped pattern with altitude. Allometric equations were obtained from the easily descriptive parameters of height (H), basal diameter (D) and crown area (C) for biomass of C. jubata and P. fruticosa. Although the equations type and variables comprising of the best model varied among the species, all equations related to biomass were significant (P < 0.005), with determination coefficients (R2) ranging from 0.81 to 0.96. The allometric equations satisfied the requirements of the model, and can be used to estimate the regional scale biomass of P. fruticosa and C. jubata in alpine ecosystems of the Qilian Mountains.

Aboveground Biomass and Water Storage Allocation in Alpine Willow Shrubs in the Qilian Mountains in China

The aboveground biomass allocation and water relations in alpine shrubs can provide useful information on analyzing their ecological and hydrological functions in alpine regions. The objectives of this study were to compare the aboveground biomass allocation, water storage ratio and distribution between foliage/woody components, and to investigate factors affecting aboveground biomass allocation and water storage ratio in alpine willow shrubs in the Qilian Mountains, China. Three experimental sites were selected along distance gradients from the riverside in the Hulu watershed in the Qilian Mountains. The foliage, woody component biomass, and water allocation of Salix cupularis Rehd. and Salix oritrepha Schneid. shrubs were measured using the selective destructive method. The results indicated that the foliage component had higher relative water and biomass storage than the woody component in the upper part of the crown in individual shrubs. However, the woody component was the major biomass and water storage component in the whole shrub level for S. cupularis and S. oritrepha. Moreover, the foliage/woody component biomass ratio decreased from the top to the basal level of shrubs. The relative water storage allocation was significantly affected by species types, but was not affected by sites and interaction between species and sites. Meanwhile, relative water storage was affected by sites as well as by interaction between sites and species type.

New methods for calculating bare soil land surface temperature over mountainous terrain

Land surface temperature (LST) causes the phase change of water, links to the partitioning of surface water and energy budget, and becomes an important parameter to hydrology, meteorology, ecohydrology, and other researches in the high mountain cold regions. Unlike air temperature, which has common altitudinal lapse rates in the mountainous regions, the influence of terrain leads to complicated estimation for soil LST. This study presents two methods that use air temperature and solar position, to estimate bare LST with high temporal resolution over horizontal sites and mountainous terrain with a random slope azimuth. The data from three horizontal meteorological stations and fourteen LST observation fields with different aspects and slopes were used to test the proposed LST methods. The calculated and measured LST were compared in a range of statistical analysis, and the analysis showed that the average RMSE (root mean square error), MAD (mean absolute deviation), and R2 (correlation coefficient) for three horizontal sites were 5.09°C, 3.66°C, 0.92, and 5.03°C, 3.52°C, 0.85 for the fourteen complex terrain sites. The proposed methods showed acceptable accuracy, provide a simple way to estimate LST, and will be helpful for simulating the water and energy cycles in alpine mountainous terrain.

Surface energy balance of Bayi Ice Cap in the middle of Qilian Mountains, China

Energy balance at the glacier surface is important for understanding the impacts of climate change on glaciers. Here, we analyzed the characteristics of the glacier surface energy fluxes along with their contributions to glacier melt on Bayi Ice Cap in Qilian Mountains by using a point-scale energy balance model. The half-hourly meteorological data from an automatic weather station (AWS) located on the glacier was used to drive the energy balance model. The model simulated results could accurately represent the mass-balance observations from the stake near the weather station during summer 2016. Our results showed the net radiation (86%) played an important role in the surface energy balance, and the contribution of the turbulent heat fluxes (14%) to the energy budget was relatively less important. A distinct behavior of energy balance, as compared to other continental glaciers in China (e.g., two adjacent glaciers Laohugou No. 12 Glacier and Qiyi Glacier), is the fact that a sustained period of positive turbulent latent flux exists on Bayi Ice Cap during August, causing faster melt rate in the month of August. Our study also presented the effect of frequent summer snowfall in slowing down surface melt by changing the surface albedo during the beginning of the melting season.

Two-year comparative study of snow cover dynamics and its impact factors on glacier surface

Snow cover on glacial surfaces is a sensitive environmental indicator. However, it is difficult to differentiate snow cover from a bare ice surface, and snow cover also changes rapidly during the melt season. Monitoring these dynamics requires sufficient time and spatial resolution; thus, traditional satellite data lack the necessary spatial resolution and rarely used to monitoring snow cover on glacier surface, which induced monitoring of snow dynamics on glacier is more challenging. Time-lapse photography has the advantage of obtaining images with high time and spatial resolution. By using an automated time-lapse digital camera, this paper documents two successive years snow cover dynamics on the Shiyi glacier and compared the meteorological conditions which induced different melt conditions. Monitoring indicate that the 2012 melt season experienced a higher snow cover fraction than the 2013 melt season because of a greater accumulated snow depth, lower air temperature and fewer sunlight hours. Successive photographs also indicate that, on the Shiyi glacier, atmospheric dust accelerates the snow melt speed and attenuates the snow depth. For the bare ice surface, the effects of atmospheric dust were reduced because the dusts were composed of Fine particles and are more easily washed away by melt water or rain. Studies on the Shiyi glacier indicate that the snow cover fraction is a key parameter that indicates the status of glacial accumulation or ablation.