三工河流域两种琵琶柴群落细根生物量、分解与周转

细根对植物群落功能的发挥和土壤碳库及全球碳循环具有重要意义。利用连续土钻取样法和分解袋法,于2010年5—10月整个生长季节内,对三工河流域两处长势不同的琵琶柴群落的细根(φ2mm)生物量、分解与周转规律及其与土壤环境的关系进行研究。结果表明,群落1和群落2土壤容重、土壤含水量、pH和电导率等土壤因子差异显著。两群落的细根生物量表现出相同的季节和垂直变化趋势,即在5—8月逐渐增加,8月达到最大值,9—10月份逐渐下降。平均月细根生物量分别为51.55g/m2和133.93 g/m2。群落1的活细根和死细根分别占总细根生物量的69.68%和30.32%,群落2活细根和死细根分别占总细根生物量的72.61%和27.39%。在垂直变化上,随土壤深度增加细根生物量先增加后逐渐降低,其中10—20cm土壤层次细根生物量比例最大,群落1和群落2分别占46.48%和29.15%。群落1和群落2的细根年分解率分别为34.82%、42.91%。达到半分解和95%分解时,群落1需要630 d和2933 d,群落2需要467 d和2238 d。群落1和群落2的细根净生产力分别为50.67 g/m2和178.15 g/m2,细根年周转率分别为1.41次、1.69次。逐步回归分析结果显示细根动态受土壤水分、pH值、电导度等土壤因子的显著影响,琵琶柴细根具有相对较低的分解速率和较高的周转速率。

Fine root biomass, decomposition and turnover of Reaumuria soongorica communities in the Sangong River basin

Fine roots comprise plant roots with a diameter less than 2 mm and are important for plant growth and development, the soil carbon pool, and the global carbon cycle. In this research, sequential soil coring and ingrowth bag methods were used to investigate the fine root dynamics and turnover (formation, senescence, death and decomposition) of two Reaumuria soongarica communities with different physiognomy characteristics from May to October 2010 (representing the whole growing season) in the Sangong River basin. The fine root distribution, selected soil properties (such as moisture content, pH, and electrical conductivity), community structure, fine root decomposition rate, and fine root turnover of two R. soongarica communities were measured. Stepwise regression analysis was used to reveal the relationship between fine root dynamics and soil characteristics. The soil bulk density, soil water content, pH and electrical conductivity were significantly different between the two communities. The fine root biomass of the two communities showed the same trends in seasonal change and vertical distribution; for example, the fine root biomass increased gradually from May to August, and reached the maximum in August, then declined gradually from September to October. The monthly average fine root biomass of Community 1 and Community 2 was 51.55 g/m² and 133.93 g/m², respectively. The live fine-root biomass and dead fine-root biomass were 69.68% and 30.32% of total fine-root biomass in Community 1, and 72.61% and 27.39% of total fine-root biomass in the Community 2, respectively. The fine root biomass of the two communities increased initially then decreased gradually as soil depth increased. The fine root biomass was highest in the 10-20 cm soil layer, comprising 46.48% and 29.15% of the total fine root biomass in Community 1 and Community 2, respectively. The fine root decomposition rate showed a sharp decline to a minimum but thereafter increased steadily in both two communities; the annual fine root decomposition rate was 34.82% and 42.91% in Community 1 and Community 2, respectively. To reach 50% decomposition and 95% decomposition, periods of 630 days and 2933 days, respectively, for Community 1 and 467 days and 2238 days, respectively, for Community 2 were needed. Fine root net productivity of Community 1 and Community 2 was 50.67 g/m² and 178.15 g/m², respectively, and the fine root annual turnover rate in the two communities was 1.41 times/a and 1.69 times/a, respectively. The stepwise regression analysis showed that fine root dynamics were significantly influenced by soil factors such as soil moisture content, pH and electrical conductivity. Fine root growth was restricted by low soil moisture content, high soil pH, and high soil electrical conductivity, and therefore the two R. soongarica communities showed low fine root biomass and a low fine root turnover rate compared with most forest and grassland ecosystems. Nevertheless, carbon and nutrient release into the soil by fine root turnover is still an important component of the carbon and nutrient budget and is of importance for monitoring climatic change in an arid region.