| The Phyllostachys pubescens forest is an important forest resource in southern China, which plays a huge role in carbon sink. At the same time, it is also a great source of carbon. P. pubescens forest similar to other forest ecosystems, releases a large amount of CO2 to the atmosphere through litter decomposition and soil respiration each year. Therefore, an investigation of litter production and soil respiration of P. pubescens will has great significance on controlling atmospheric CO2 concentration, climate dynamics and global carbon cycle of the earth system. This study was conducted at Caicun, Jingxian County where is one of the main area of bamboo production in Anhui Province. We investigated the stand structure and soil characteristics and observed the dynamics of litterfall and soil respiration to reveal the growth, nutrient and carbon cycling characteristics. The main results obtained in this study are as follows.The mean diameter at breast height (DBH), mean height, stand density, basal area, mean AGS and mean uniformity of the P. pubescens forest were 9.73 cm,13.43 m,3076 stems·hm2,22.84 m2·hm-2,0.29 and 6.03, respectively.Among all the sampling stands, the concentrations of soil organic carbon (SOC), total nitrogen (N), available phosphorus (AP), and dissolved organic carbon (DOC) in the P. pubescens stands decreased with increasing depth of soil. The concentration of soil total calcium (Ca) ranged from 37.46 to 53.10 mg·kg-1, total magnesium (Mg) from 48.24 to 54.26 mg·kg-1, NH4+-N from 8.42 to 10.59 mg·kg-1 and NO3--N from 0.16 to 0.53 mg·kg-1. The lowest concentration of total phosphorus and potassium were found in 10-30 cm and 0-10 cm soil layer, respectively. The value of CV (%) was distinctly higher for DOC (31.96%) than other variables in P. pubescens stands, but total P (9.52%) was the lowest.The results from the regression analysis indicated that the stand density and uniformity were significantly correlated with the NO3--N in 0-50 cm soil in P. pubescens stands (p<0.05). The mean height of P. pubescens stands was significantly correlated with total Mg (p<0.05). However, the other soil variables were not significantly correlated with stand growth index (p>0.05).The mean annual litterfall biomass of the P. pubescens stands in Jingxian was 4.50 t·hm-2·a-1 with a single-peak, of which the maximum monthly litterfall occurred in April (1.33 t·hm-2) while the least in January (0.02 t·hm-2). The monthly litterfall amount was ordered as Apr.> May.> Jun.>Mar.> Jul.> Aug.> Nov.> Oct.> Dec.> Feb.> Jan.. The monthly litterfall was significantly higher in April than in other months (p<0.05).The nutrient concentration of litterfall was in order of N (15.57 g·kg-1)> Ca (5.51 g·kg-1)> Mg (2.74 g·kg-1)> K (2.60 g·kg-1)> P (0.35 g·kg-1). The value of CV (%) was distinctly higher for total P than for other variables in litterfall, with the lowest for total N. The nutrient concentrations of sheath were in order of N (17.01 g·kg-1)> K (4.24 g·kg-1)> Mg (1.94 g·kg-1)> Ca (0.75 g·kg-1)> P (0.21 g·kg-1). In comparison with the concentrations in the two components, litterfall had higher nutrient concentrations than sheaths did except for total N and K.The annual total nutrient input from litterfall to the forest floor was 120.53 kg·hm-2·a-1, of which, N input was the greatest (67.41 kg-hm-2·a-1) and contributed 55.93% of the total. P input was the least (1.55 kg-hm-2·a-1) and contributed only 1.29% of the total. The other nutrient inputs from litterfall were Ca 25.68 kg·hm-2·a-1, Mg 13.61 kg·hm-2·a-1 and K 12.28 kg·hm-2·a-1. The dynamics of annual carbon input from litterfall was the same as the litterfall biomass with a single-peak, of which the highest (0.59 t-hm-2) occurred in April and the least (0.01 t·hm-2) in January.The diurnal change of soil respiration in P. pubescens stands showed a single-peak appeared from 12:00 to 16:00. There was an obvious seasonal dynamics. The average monthly rates of soil respiration varied from 5.90 μmol·m-2·s-1 to 0.66 μmol·m-2·s-1, with a significant difference among months (p<0.05). The highest rate of soil respiration and the least rate appear in July and January, respectively. The results from the regression analysis indicated that soil respiration was significantly correlated with soil temperature and relative humidity (p<0.01). The Q10 values of the soil respiration of Phyllostachys pubescens stands was 1.95 with significant changes amongst months. The maximum Q10 value (18.12) was in January which had the lowest temperature, while the minimum Q10 value (1.47) was in July which had the highest temperature... |
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