[Variations of water use efficiency and its relationship with leaf nutrients of different altitudes of Wuyi Mountains, China]. / æ­¦å¤·å±±ä¸åŒæµ·æ‹”æ¤ç‰©æ°´åˆ†åˆ©ç”¨æ•ˆçŽ‡çš„å˜åŒ–åŠå ¶ä¸Žå »åˆ†å˜åŒ–çš„å ³ç³».

We determined the water use efficiency and nitrogen and phosphorus concentrations of plants at different altitudes (600, 900, 1300, 1500, 1800, 2000, 2100 m) in Wuyi Mountains to understand the relationship of water use efficiency with foliar nutrients. The results showed that plant water use efficiency increased with altitude, and the leaf δ18O of tree showed no significant variance with altitude. On the whole, leaf nitrogen concentration showed no obvious trend, while leaf phosphorus concentration at high altitude was significantly higher than that at low altitude. No significant relationship between water use efficiency and foliar nitrogen concentration was found in this study, but water use efficiency had a positive correlation with foliar phosphorus concentration. In conclusion, the change of water use efficiency was mainly caused by the difference in photosynthetic rate. The effect of water status on plant water use efficiency was not significant. The variances of leaf phosphorus concentrations along the altitudinal gradient may affect photosynthetic rate and in turn the water use efficiency of plant in this area.

[Variations of soil labile organic carbon along an altitude gradient in Wuyi Mountain].

By using sequential fumigation-incubation method, this paper determined the soil labile organic carbon (LOC) content under evergreen broadleaf forest, coniferous forest, sub-alpine dwarf forest, and alpine meadow along an altitude gradient in Wuyi Mountain National Nature Reserve in Fujian Province of China, with its relations to soil microbial biomass carbon (MBC), total organic carbon (TOC), total nitrogen (TN), and fine root biomass (FRB) analyzed. The results showed that soil LOC occupied 3.40%-7.46% of soil TOC, and soil MBC occupied 26.87%-80.38% of the LOC. The LOC under different forest stands increased significantly with altitude, and decreased with soil depth. Soil LOC had very significant correlations with soil MBC, TOC, TN and FRB, and its content was obviously higher at higher altitudes than at lower altitudes.

[Seasonal variation and temperature sensitivity of soil respiration under different plant communities along an elevation gradient in Wuyi Mountains of China].

Taking the National Nature Reserve in Wuyi Mountains as experimental site, the seasonal variation and temperature sensitivity of soil respiration under four plant communities along an elevation gradient were studied, with their relations to the main environmental factors analyzed. The results showed that the soil respiration under the four plant communities had the same seasonal pattern, with the maximum (3.10-6.57 micromol CO2 x m(-2) x S(-1)) occurred in summer and the minimum (0.27-1.15 micromol CO2 x m(-2) x s(-l)) in winter. Soil respiration rate had a significant exponential correlation with soil temperature, but its correlations with soil moisture and litter input differed with plant communities. The Q10 value of soil respiration was higher at high elevation than at low elevation. In mid-subtropical regions, the seasonal variation of soil respiration at different elevations was mainly controlled by soil temperature, indicating that in the case of global warming in the future, soils at higher elevation might release more CO2 to the atmosphere.