模拟氮沉降对鄂西南亚高山湿地泥炭藓(Sphagnum)凋落物分解的影响

Effects of simulated nitrogen deposition on decomposition of Sphagnum in a subalpine wetland,south-western Hubei Province

当前氮沉降对湿地泥炭藓凋落物分解的影响还存在很大争议,并且亚热带湿地泥炭藓分解对氮沉降的响应研究鲜见报道.采用分解袋法,在鄂西南地区开展模拟氮沉降对泥炭藓凋落物分解影响的实验.模拟氮浓度设置4个水平,分别为N0(0 g m^(-2)a^(-1))、N3(3 g m^(-2)a^(-1))、N6(6 g m^(-2)a^(-1))、N12(12 g m^(-2)a^(-1)),其中N0为对照(CK).野外分解3、6、9和12个月后,室内测定泥炭藓凋落物干重、灰分、总碳(C)、总氮(N)、C/N以及总酚含量,计算凋落物的质量残留率、总碳(C)残留率及总酚残留率.结果显示:(1)氮沉降对凋落物分解的影响取决于分解时间,且泥炭藓凋落物的分解主要发生在前6个月.分解12个月后,N3浓度的质量残留率较CK下降了11.91%,而N6、N12较CK分别增加了12.98%、10.43%.(2)氮沉降对凋落物灰分含量有一定影响,但是随分解时间的延长影响程度不同.凋落物的相对灰分含量和绝对灰分含量均随分解时间的增加呈显著增加趋势.(3)氮沉降对泥炭藓凋落物总碳(C)含量有显著的影响(P<0.05),分解时间对泥炭藓凋落物总碳(C)、总氮(N)及总酚含量存在显著影响(P<0.05),且氮沉降对泥炭藓凋落物总碳(C)含量的影响程度取决于分解时间.分解12个月后,凋落物中总碳(C)含量和C/N均较初始值有所下降,总氮(N)含量和总酚含量则有所增加.(4)凋落物质量残留率、总碳(C)残留率与总酚残留率呈现出较强的线性正相关.可见,氮沉降对泥炭藓分解在短期内有一定影响,但并不是简单地促进或抑制作用.

The effects of nitrogen deposition on the decomposition of Sphagnum litters are controversial,and there are few reports on the effects of nitrogen deposition on the decomposition of Sphagnum litters in subtropical wetlands.A field decomposition experiment of Sphagnum after deposition of artificial nitrogen was conducted in south-western Hubei Province.Four levels of simulated nitrogen concentration were set as N0(0 g m^(-2)a^(-1)),N3(3 g m^(-2)a^(-1)),N6(6 g m^(-2)a^(-1)),and N12(12 g m^(-2)a^(-1)),considering N0 as the control(CK).The litter decomposition bags were collected after 3,6,9,and 12 months,and the remaining mass,ash content,C,N,C/N,and total polyphenol content in the litter were determined.Mass remaining rate,carbon remaining rate,and total polyphenol remaining rate were calculated.The results showed that(1)the effects of nitrogen deposition on the decomposition of sphagnum litter depend on decomposition time,and the deposition of Sphagnum litter mainly occurs in the first 6 months.After 12 months,the mass remaining rate of the N3 treatment decreased by 11.91%compared with CK,whereas that of N6 and N12 increased by 12.98%and 10.43%,respectively.(2)N deposition had a certain effect on the ash content of litter,but the degree of influence varied with the duration of decomposition time.The ash content increased significantly with the increase in decomposition time.(3)N deposition had significant effects on the total C content,and the effects depended on decomposition time.The decomposition time had significant effects on the levels of total C,N,and polyphenol.After 12 months,the total C content and C/N in the litter decreased,whereas the total N content increased.(4)The mass remaining rate,total C remaining rate,and the total phenol remaining rate showed a strong linear positive correlation.N deposition had a certain effect on the decomposition of Sphagnum litter,but it was not a simple effect of promotion or inhibition.