Youchao Chen

Temporal-Spatial Variation and Controls of Soil Respiration in Different Primary Succession Stages on Glacier Forehead in Gongga Mountain, China

Soil respiration (SR) is an important process in the global carbon cycle. It is difficult to estimate SR emission accurately because of its temporal and spatial variability. Primary forest succession on Glacier forehead provides the ideal environment for examining the temporal-spatial variation and controlling factors of SR. However, relevant studies on SR are relatively scarce, and variations, as well as controlling factors, remain uncertain in this kind of region. In this study, we used a static chamber system to measure SR in six sites which represent different stages of forest succession on forehead of a temperate glacier in Gongga Mountain, China. Our results showed that there was substantial temporal (coefficient of variation (CV) ranged from 39.3% to 73.9%) and spatial (CV ranged from 12.3% to 88.6%) variation in SR. Soil temperature (ST) at 5 cm depth was the major controlling factor of temporal variation in all six sites. Spatial variation in SR was mainly caused by differences in plant biomass and Total N among the six sites. Moreover, soil moisture (SM), microbial biomass carbon (MBC), soil organic carbon (SOC), pH and bulk density could influence SR by directly or indirectly affecting plant biomass and Total N. Q10 values (ranged from 2.1 to 4.7) increased along the forest succession, and the mean value (3.3) was larger than that of temperate ecosystems, which indicated a general tendency towards higher-Q10 in colder ecosystems than in warmer ecosystems. Our findings provided valuable information for understanding temporal-spatial variation and controlling factors of SR.

DETECTION OF METAL IONS USING A WAVELENGTH INTERROGATION SURFACE PLASMON RESONANCE SENSOR WITH CALIX[4]ARENE DERIVATIVES AS SENSING FILMS

A wavelength interrogation surface plasmon resonance (SPR) sensor with gold substrate modified with calix[4]arene derivative as sensing film was used to detect metal ions in aqueous solutions. We found that only Ag+and Cu2+could be selectively detected with the detection limit of 10−7 mol/L and 10−4 mol/L, respectively. XPS data confirmed the presence of Au-S bond between the calixarene derivative and the gold substrate and complexation between the calixarene derivative and Ag+ or Cu2+.

Comparison of soil respiration among three different subalpine ecosystems on eastern Tibetan Plateau, China

Abstract The pattern of soil respiration and its responsible factors are still unclear in subalpine ecosystems. In this study, we used a static chamber system to measure soil respiration in a primary Abies fabri (Masters) Craib forest, a secondary A. fabri forest and a clear-cut land on Gongga Mountain, east of Tibetan Plateau in China. Our results showed there were substantial diurnal and temporal variations in these three subalpine ecosystems. The diurnal coefficient of variation (CV) of soil respiration was lowest in primary forest (20.5%), and highest in clear-cut land (40.4%). Diurnal patterns of soil respiration were generally associated with soil temperature at 5 cm for all the three systems. The temporal CV was lowest in secondary forest (55.6%), and highest in clear-cut land (82.8%). Soil temperature at 5 cm depth was the major factor controlling 55–61% of temporal variation of soil respiration. The temperature sensitivity (Q10 value) was higher in clear-cut land (Q10 = 6.7) than that in primary forest (3.7) and secondary forest (3.0), indicating that soil respiration in clear-cut land was more sensitive to temperature change. Annual soil respiration was 3330.2 g carbon dioxide (CO2) m−2 year−1, 2358.9 g CO2 m−2 year−1 and 4162.8 g CO2 m−2 year−1 for primary forest, secondary forest and clear-cut land, respectively. Our findings provided valuable information for understanding the effect of forest ecosystem change and land management on soil respiration in high-elevation subalpine ecosystems.

Cadmium Distribution in a Timberline Forest in the Hengduan Mountains in the Eastern Tibetan Plateau

In order to study the regional distribution, characterization, and possible source of Cadmium in the eastern Tibetan Plateau, samples of leaves, xylem, twigs, bark, and roots of timberline forest trees (fir or spruce) and soils at depths from 0 to 40 cm were collected in eight sites in Hengduan Mountains. According to Cd contents, organs and tissues were divided into three groups: the highest-level organ (roots: 0.237 mg · kg−1), the high-level organ/tissue (bark: 0.183 mg · kg−1 and twigs: 0.159 mg · kg−1), and the low-level organ/tissue (xylem: 0.054 mg · kg−1and leaves: 0.048 mg · kg−1). Cd contents in Transect A were a little higher than Transect B. Sites near pollutant sources and high-levels are more sensitive to Cd pollution and accumulated more Cd, while Cd contents in sites far away from pollutant sources and low-level organ/tissue were relatively low. It is suggested that the eastern Tibetan Plateau has already been polluted by the influence of general circulation to some extent. Nevertheless, low Cd contents in some sites prove that high mountains may barricade Cd pollutants from monsoon.

The chromium in timberline forests in the eastern Tibetan Plateau

In order to study the regional distribution, trait and possible source of chromium in the eastern Tibetan Plateau, we collected samples of xylem, bark, leaves and twigs in two parallel northwest-southeast belt transects (TA and TB) from the Hengduan Mountains. According to the Cr mean concentration, organ/tissue was split into two groups: the high-level organ/tissue (twigs: 1.476 mg kg(-1)) and the low-level organ/tissue (bark: 0.413 mg kg(-1), leaves: 0.340 mg kg(-1) and xylem: 0.194 mg kg(-1)). The mean Cr concentrations of twigs and leaves in TB samples were higher than those in the TA samples, and the mean Cr concentration in both sites gradually reduced from southeast to northwest. Both the southeasterly and southwesterly monsoons could be significant, influential factors in this connection. The top three mean Cr concentrations were S7, S1 and S8, which were closer to the developed city. Mean Cr concentrations in S3, S4 and S5, (remote, high mountains) were relatively low. The high mountains acting as a barrier to the monsoon and the distance from the big city may play important roles in the distribution of Chromium. Furthermore, the relationship between the mean Cr concentration and precipitation, timberline trees as bio-monitors of chromium pollution in polluted areas and the possible source of Cr in the eastern Tibetan Plateau are also discussed. This study may provide reliable proof of Cr contamination processes, and so help in future to prevent further Cr pollution, and also be helpful in understanding the important function of forest ecosystems in relation to atmospheric pollution and global change. To better understand the characteristics of temporal and spatial distribution of Cr concentration, we found that tree ring, fine roots and soil samples are good choices.

The cadmium and lead of soil in timberline coniferous forests, Eastern Tibetan Plateau

The health of coniferous forests has been attended due to the heavy metal pollution. The accumulation of heavy metals can increase the risk of harmful effects in the future. The monitoring of soil in timberline forests in the east of the Tibetan plateau was performed. Soil samples were collected by laminating sampling. Concentrations of Cd and Pb were analyzed by ICP-MS. Spatial distribution of elements (Cd and Pb) by geostatistical analysis is presented. The concentrations of Pb and Cd between different years (in 1990 and in 2012) also are compared. Results show that Cd and Pb concentrations of soil are much higher in current levels. Cd and Pb inputs of timberline forests present an increasing trend in the last two decades. Such heavy metal monitoring of soil is needed to provide databases so that the next step of this kind would be to evaluate levels of trace metal accumulation, formulate environmental legislation and control strategies of timberline forests in the future. The possible source and influencing factors of Cd and Pb in soil are also discussed.

Highway construction and protection of sichuan giant panda sanctuaries

Planned highway will pass through the buffer zone or the core zone of world natural heritage Sichuan giant panda sanctuaries. There is a direct impact on the authenticity and integrity of world natural heritage Sichuan giant panda sanctuaries during the highway construction and operation period. We propose to reduce the construction project on environmental stress and ecological impact by the special management measures.

Soil respiration in the deglaciered area on Gongga Mountain, Southwest China

Soil respiration rates were measured during 2006 to 2009 using a soil respiration chamber connected to a portable photosynthesis system (CI-301). Vegetation succession on Hailuogou deglaciered area is serially divided into 7 stages:® herbs community,