A Study On The Characteristics Of Carbon Balance In Phyllostachys Edulis Plantation Ecosystem

Moso bamboo (Phyllostachys edulis) is one of the important forest species in SouthChina. It is widely distributed and has a long planting history. Partly estimated, the area ofMoso bamboo plantation is more than 3.0×10⁶hm² in China, accounting for about 20% of thetotal bamboo forests area all over the world. The cultivated area has been increasing gradually theseyears, thus not only supplied a lot of commercial timber for the country, but also played animportant role in the maintenance of ecological balance. Based on the measurement of CO₂dynamics and productivity survey, the characteristics of carbon balance between assimilationand release in Moso bamboo plantation was studied with CID-301 portable photosynthesissystem in Huitong County, Hunan Province. The results showed that:(1) Annual and daily dynamic pattern of soil respiration and litter respiration in Mosobamboo plantation was measured. It was the fist time to analyze the contribution of autotrophicrespiration, heterotrophie respiration and each component of respiration to soil respiration inMoso bamboo plantation.â‘ Total soil respiration, mineral soil respiration, root respiration and litter annualrespiration of Moso bamboo plantation were 2.1276, 1.4403, 0.6873 and 0.3058μmolCO₂·m^-2·s^-1, respectively. The annual dynamic pattern could be represented with a curveof one-peak type. The respiration rates increased with increasing atmospheric and soiltemperature from January to July. Total soil respiration, mineral soil respiration, rootrespiration and litter respiration reached their highest values in August, being 4.9487, 3.0092,1.9359 and 0.7976μmolCO₂·m^-2·s^-1, respectively. All of these respiration rates disereasedgradually with falling temperature from August to January or Febery next year. At this time, therespiration rates reached the lowest values, which were 0.764, 0.701, 0.0625 and 0.0471μmolCO₂·m^-2·s^-1, respectively. Litter respiration mainly concentrated in the month from May toSeptember, accounting for 73.6% of the whole-year value.â‘¡The daily variation diagram of total soil respiration, mineral soil respiration, rootrespiration and litter respiration of Moso bamboo plantation could also be represented withcurves of one-peak type. They usually increased with higher temperature and decreased withlower temperature. From 6:00-14:00, the rates increased with increasing temperature, reaching the highest value at 16:00-18:00. After this time, they decreased until 4:00～8:00 in nextmorning. Soil respiration of Moso bamboo plantation during day and night time did not differsignificantly.â‘¢The amount of CO₂ released in Moso bamboo plantation was 33.9414 tCO₂.hm^-2.a^-1or 2.8284 tCO₂.hm^-2 for one month. The annual respiration of litter layers, mineral soil, deadfine root and lively fine root were 4.154, 19.052, 1.1367 and 9.5957 tCO₂·hm^-2.a^-1, whichaccounting for 12.24%, 56.14%, 3.35% and 28.27% of the total forest respiration, respectively.The result showed that the turnover time of soil organic carbon in Moso bamboo plantationwas 21.35 years.â‘£Soil temperature, humidity and the interaction between them remarkably affected soilrespiration. Soil temperature alone could explain 67.4% of the change of Moso bamboo soilrespiration. The correlation between the total soil respiration and soil temperatures at 5cm and10cm soil depth was closer than that between total soil respiration and atmosphere temperature.Compared with soil temperature, soil water content contributed less to the change of soilrespiration. Soil water content could only explain 10% of the change of soil respiration in theMoso bamboo plantation. However, there was obvious interaction between soil temperatureand water content. When combining together, they could explain 79.8% of the change of Mosobamboo soil respiration. This study suggested that the critical point of temperature respondingto soil respiration should be about 30℃and the critical point of soil water content which wouldcause inhibition of soil respiration should be about 36% in Moso bamboo plantation. Rootbiomass of Moso bamboo and soil microbiological carbon could explain 72.8% and 73.75% ofthe change of soil respiration in the Moso bamboo plantation, respectively. When combiningtogether, root biomass and soil surface temperature could explain 86% of the change of soilrespiration in the Moso bamboo plantation.(2) By employing biomass investigation method, carbon storage and carbon distributionin Moso bamboo plantation ecosystem were measured. It showed that the carbon storage inMoso bamboo plantation ecosystem was 144.3 tC·hm^-2, consisting of 110.95 tC·hm^-2 in forestsoil, 32.61 tC·hm^-2 in vegetation, and 0.74 tC·hm^-2 in forest litter.â‘ The average carbon concentration in all Moso bamboo organs were 47.74%-50.13%.The value for branch, sheath, stem, leaf, rhizome, and root were 50.13%, 49.91%, 49.27%, 48.00%, 47.8%, and 47.74%, respectively. The average carbon concentration in Moso bambooorgans were not correlated to their age.â‘¡Vegetation carbon storage in Moso bamboo plantation was 31.97 tC·hm^-2. The carbonstorage in tree layer was 30.58 tC·hm^-2, which contributing to 95.64% of vegetation carbonstorage while the shares of litter and under storey were 2.33% and 2.02%, respectively. Thecarbon storage shares of different organs in Moso Bamboo plantation were positively related totheir biomass.â‘¢Carbon content of three soil layers (60cm depth) in Moso bamboo plantation was1.015%-2.607%, differing significantly among different soil layers. Soil carbon content andcarbon storage were highest in surface layer (0-20cm), contributing to 44.75% of soil carbonstorage, being 1.38 times and 1.97 times those in 20-40cm and 40-60cm layers, respectively.â‘£Soil granule structure of Moso bamboo plantation was dominated by＞5mm aggregatefor all the three soil layers, accounting for 26.39%-42.38% of all soil aggregate. Soilaggregates of 1-5mm and＜0.25mm accounted for 14%-18% and 2.31%-6.73%, respectively.Mean weight diameter of soil aggregate in Moso bamboo plantation was 0.90 mm, whichtended to increase with descending soil layers. The accumulation of soil organic carbon wassignificantly related to organic carbon in 0.25-3.15mm aggregate. However, the correlationsbetween soil organic carbon accumulation and organic carbon in both＞3.15mm and＜0.25mmaggregates were not significant.(3) This study for the first time reported that fine root growth rate and deeomposation rateof Moso bamboo plantation were 6.895 t.hm^-2.a^-1 and 0.3124 t.hm^-2.a^-1, respectively. Theannual turnover of fine root in Moso bamboo plantation was 0.93 time.yr^-1. It was thereforecomputed that the annual carbon input into soil through litter fall was 2.2451 t.hm^-2.a^-1 in Mosobamboo plantation, of which 78.5% was from aboveground litter and 21.5% was fromunderground dead roots. As the litter fall decomposed, 0.802t.hm^-2.a^-1 of carbon was imputedinto the soil in the form of humic acids.(4) The total CO₂ fixation in Moso bamboo plantation ecosystem was 37.18tCO₂·hm^-2·a(-1),while the total CO₂ released from the system through soil and litter respiration was 29.786tCO₂·hm^-2·a^-1 and 4.115t CO₂·hm^-2·a^-1, respectively. Therefore, the carbon budget for Mosobamboo plantation ecosystem was 3.239tCO₂·hm^-2·a^-1 or 0.883tC·hm^-2·a^-1. It is concluded that the Moso bamboo plantation ecosystem is one of the most important sinks for the increasingCO₂ in the air, and that managing Moso bamboo plantation could be an alternative strategy foralleviating global climate stress.