RESUMEN
The allocation dynamics of soil carbon pools during soil development and land use are the key to revealing the carbon cycle process. To clarify the distribution of the soil carbon pool and its change trend, a soil reclamation chronosequence (0 a, 60 a, 160 a, 280 a, 1 000 a, and 1 500 a reclamation) was established in a typical alluvial plain in the Lower Yangtze River, and the content and density of soil organic carbon (SOC), soil inorganic carbon (SIC), particulate organic carbon (POC), and mineral-associated organic carbon (MAOC), along with carbon sequestration potential (CSP) indicators of topsoil under different land use types were measured and analyzed. The results showed that after approximately 1 500 a reclamation, the SOC content developed from the Yangtze River alluvial deposits generally increased by 4.9% after the initial decline, whereas the SIC content decreased to 0.2% from 25.8% of the total carbon content due to its rapid leaching. The MAOC content was normally higher than that of POC, and MAOC was contributing 48.0%-79.7% of the SOC accumulation. In this region, the soil organic carbon density (SOCD) accounted for 57.4%-100% of the total carbon density, the soil carbon sequestration levels (CSL) ranged from 18.6% to 56.1%, and CSP under paddy-dryland rotation increased by 20.8% compared to that under dryland. The C/N ratio and total nitrogen content are key factors in explaining soil carbon accumulation processes, and the reclamation year plays an important role in evaluating soil carbon sequestration levels. After long-term utilization, the cultivated soil in the Yangtze River floodplain must be carefully managed through balanced fertilization to maintain soil productivity, promote the accumulation of SOC, and avoid the decline in soil carbon sequestration capacity.
RESUMEN
OBJECTIVE: To explore the distribution of pressure- and heat-sensitive acupoints of the Large Intestine of Hand-Yangming, Stomach Meridian of Foot-Yangming and the Lung Meridian of Hand-Taiyin below the elbow and knee joints in patients with allergic rhinitis, so as to explore the positive reaction points at the body surface of allergic rhinitis. METHODS: Thirty variant rhinitis volunteer subjects and 30 healthy subjects were recruited in the present study. The subcutaneous induration, reaction points of emptiness-like feeling or pressing pain below the elbow- and knee-joints along the Large Intestine Meridian, Stomach Meridian and the Lung Meridian were inspected first, then re-examined by using heat-sensitized moxibustion method and a hand-held pain threshold tester (mechanical pressure), respectively. The frequency and coincidence rate of pressing-pain sensitive and heat-sensitive points were analyzed. RESULTS: In the 30 patients with allergic rhinitis, 10 positive reaction points as Kongzui (LU6), Chize (LU5), Hegu (LI4), Quchi (LI11), Shousanli(LI10), Zusanli (ST36), Shangjuxu (ST37), Fenglong (ST40), Xiajuxu (ST39), and non-acupoint of the Lung Meridian were found. Among them, the duration of heat-sensitive reaction in the LU6, LI10, ST37, ST40, and ST39 regions was obviously shorter in patients than in healthy subjects (P<0.01,P<0.005). The heat-sensitive forms of the positive reaction points were mainly heat transmission, heat-penetration and local reaction. The mechanical pain thresholds of the positive reaction points (LI4, LU6, LI10, LI11 and non-acupoint of the Lung Meridian) at the upper limbs and those (ST36, ST37 and ST40) at the lower limbs were evidently lower in patients than in healthy volunteer subjects (P<0.05). The pressure- and heat-sensitive acupoints were basically coincide in the patients, but being higher in patients than in healthy subjects in the frequency of occurrence. The mechanical pain threshold of the pressure-sensitive acupoints in patients was remarkably lower on the left side than on the right side of the upper limb, and obviously higher on the left side than on the right side of the lower limb (P<0.05). No significant differences were found between the right and left sides in the pain threshold in healthy subjects (P>0.05). CONCLUSION: There is a high overlap in the distribution of pressure- and heat-sensitive acupoints of the Lung, Large Intestine and Stomach meridians below the elbow and knee joints in patients with allergic rhinitis, and there is an imbalance between the left and right limbs in the mechanical pain threshold of the pressure- and heat-sensitive acupoints, but needing being further confirmed.
