季节性积雪下的高山草地凋落物分解
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摘要
青藏高原高山草地的凋落物分解是其生物地化循环过程的重要一环.采用样方调查法估测两种典型地形条件下高山草地单位面积的年凋落物产量,分析定面积凋落物分解袋中的初始装袋量与凋落物分解率的关系,估算最佳初始凋落物装袋量.通过积雪期设置双面凋落物分解袋于浅雪、深雪、无雪及人工雪被处理下,比较不同的雪被处理下凋落物的分解率,同时测定对应的土壤温度及土壤微生物生物量碳氮含量,进而分析土壤微生物生物量碳氮与凋落物分解率之间的相关关系.研究发现:(1)两种典型样地内植物凋落物在自然状态下的年产生量均约为90 g/m~2;(2)非生长季中凋落物分解率与凋落物初始重量呈负线性相关,凋落物初始装袋量3 g是研究分解率的相对较佳重量;(3)随着积雪厚度的增加,非生长季土壤温度和凋落物分解率提高,同时也促进了土壤微生物生物量的积累,凋落物分解率和土壤微生物生物量碳、氮在深雪与无雪处理下分别达到最大值(分别为10.15%,156.37 mg/kg,75.89 mg/kg)和最小值(分别为3.07%,65.38mg/kg,20.17mg/kg).土壤微生物生物量碳、氮均与凋落物分解率呈显著相关性(P <0.05).综上所述,即便在冬季气温低于冰点的情况下,雪被的隔绝作用使得土壤微生物活动依然活跃进行;雪被变化既改变了土壤环境因子及凋落物分解率,也深刻影响着高山草地生态系统的结构与功能.
Litter decomposition is an important part of the biogeochemical cycles in alpine meadows of eastern Tibetan Plateau under long-lasting snow cover. This study aimed to calculate annual plant litter production and determine appropriate litter mass in a fixed-area litterbag. Subsequently, the decomposition rate of plant litter was compared under different snow depths.Lastly, the relationship of litter decomposition rate with soil microbial biomass was analyzed. The annual litter production per unit area was calculated by using the quadrat method at two typical topographic sites. A double-faced litter bag was applied to get suitable litter mass for packing and to evaluate litter decomposition rates under four different snow cover treatments, i.e.deep snow cover(Deep), shallow snow cover(Shallow), without snow cover(None), and artificial snow cover(Artificial). Soil temperature and soil microbial biomass were also measured and logged over the entire experimental period. The results indicated that 1) the in situ plant litter production was approximately 90 g/m~2; 2) the litter decomposition rate showed a negative linear regression with the litter mass in the litterbag with fixed-area, and 3 g of litter mass was the appropriate amount to measure decomposition rates in this study; 3) soil temperature and litter decomposition rate increased with increasing depth of snow cover, which also promoted the accumulation of soil microbial biomass. The litter decomposition rate and soil microbial biomass were the highest(decomposition rate: 10.15%; MBC: 156.37 mg/kg; MBN: 75.89 mg/kg) under maximum snow depth and the lowest(decomposition rate: 3.07%; MBC: 65.38 mg/kg; MBN: 20.17 mg/kg) in the treatment without snow cover, respectively.The above results demonstrated that many ecological processes in winter could persist because of the insulation effect of the snow cover formed at near-freezing temperatures. Therefore, the variation of snowpack accumulation not only alters the litter decomposition rate, but can also affect the structure and function of an alpine meadow ecosystem in the eastern Tibetan Plateau.
Litter decomposition is an important part of the biogeochemical cycles in alpine meadows of eastern Tibetan Plateau under long-lasting snow cover. This study aimed to calculate annual plant litter production and determine appropriate litter mass in a fixed-area litterbag. Subsequently, the decomposition rate of plant litter was compared under different snow depths.Lastly, the relationship of litter decomposition rate with soil microbial biomass was analyzed. The annual litter production per unit area was calculated by using the quadrat method at two typical topographic sites. A double-faced litter bag was applied to get suitable litter mass for packing and to evaluate litter decomposition rates under four different snow cover treatments, i.e.deep snow cover(Deep), shallow snow cover(Shallow), without snow cover(None), and artificial snow cover(Artificial). Soil temperature and soil microbial biomass were also measured and logged over the entire experimental period. The results indicated that 1) the in situ plant litter production was approximately 90 g/m~2; 2) the litter decomposition rate showed a negative linear regression with the litter mass in the litterbag with fixed-area, and 3 g of litter mass was the appropriate amount to measure decomposition rates in this study; 3) soil temperature and litter decomposition rate increased with increasing depth of snow cover, which also promoted the accumulation of soil microbial biomass. The litter decomposition rate and soil microbial biomass were the highest(decomposition rate: 10.15%; MBC: 156.37 mg/kg; MBN: 75.89 mg/kg) under maximum snow depth and the lowest(decomposition rate: 3.07%; MBC: 65.38 mg/kg; MBN: 20.17 mg/kg) in the treatment without snow cover, respectively.The above results demonstrated that many ecological processes in winter could persist because of the insulation effect of the snow cover formed at near-freezing temperatures. Therefore, the variation of snowpack accumulation not only alters the litter decomposition rate, but can also affect the structure and function of an alpine meadow ecosystem in the eastern Tibetan Plateau.
引文
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2李俊,吴福忠,杨万勤,谭波,彭艳,王滨,常晨晖.高山草甸冬季凋落物分解过程中土壤动物对微生物群落结构的影响[J].应用与环境生物学报,2016,22(1):27-34[Li J,Wu FZ,Yang WQ,Tan B,Peng Y,Wang B,Chang CH.Effects of soil fauna on microbial community structure in foliar litter during winter decomposition in an alpine meadow[J].Chin J Appl Environ Biol,2016,22(1):27-34]
3郭剑芬,杨玉盛,陈光水,林鹏,谢锦升.森林凋落物分解研究进展[J].林业科学,2006,42(4):93-100[Guo JF,Yang YS,Chen GS,Lin P,Xie JS.A review on litter decomposition in forest ecosystem[J].Sci Silv Sin,2006,42(4):93-100]
4 Curl H,Hardy JT,Ellermeier R.Spectral absorption of solar-radiation in alpine snowfields[J].Ecology,1972,53(6):1189-1194
5 Edwards AC,Scalenghe R,Freppaz M.Changes in the seasonal snow cover of alpine regions and its effect on soil processes:a review[J].Quaternary Intern,2007,162:172-181
6吴彦.季节性雪被覆盖对植物群落的影响[J].山地学报,2005,23(5):40-46[Wu Y.Effects of seasonal snow cover on plant community[J].JMount Sci,2005,23(5):40-46]
7武启骞,吴福忠,杨万勤,徐振锋,何伟,何敏,赵野逸,朱剑霄.季节性雪被对高山森林凋落物分解的影响[J].植物生态学报,2013,37(4):296-305[Wu QQ,Wu FZ,Yang WQ,Xu ZF,He W,He M,Zhao YY,Zhu JX.Effect of seasonal snow cover on litter decomposition in alpine forest[J].Chin J Plant Ecol,2013,37(4):296-305]
8 Baptist F,Yoccoz NG,Choler P.Direct and indirect control by snow cover over decomposition in alpine tundra along a snowmelt gradient[J].Plant Soil,2010,328(1-2):397-410
9 Walker DA,Halfpenny JC,Walker MD,Wessman CA.Long-term studies of snow-vegetation interactions[J].Bioscience,1993,43(5):287-301
10 Williams MW,Brooks PD,Seastedt T.Nitrogen and carbon soil dynamics in response to climate change in a high-elevation ecosystem in the rocky mountains,USA[J].Arctic Alpine Res,1998,30(1):26-30
11 Beare MH,Parmelee RW,Hendrix PF,Cheng WX,Coleman DC,Crossley DA.Microbial and faunal interactions and effects on litter nitrogen and decomposition in agroecosystems[J].Ecol Monographs,1992,62(4):569-591
12 Olson JS.Energy storage and the balance of producers and decomposers in ecological systems[J].Ecology,1963,44:322-331
13 Taylor BR,Jones HG.Litter decomposition under snow cover in a balsam fir forest[J].Can J Bot-Rev Can Bot,1990,68(1):112-120
14 Groffman PM,Driscoll CT,Fahey TJ,Hardy JP,Fitzhugh RD,Tierney GL.Colder soils in a warmer world:a snow manipulation study in a northern hardwood forest ecosystem[J].Biogeochemistry,2001,56(2):135-150
15高景,王金牛,徐波,谢雨,贺俊东,吴彦.不同雪被厚度下典型高山草地早春植物叶片性状、株高及生物量分配的研究[J].植物生态学报,2016,40(8):775-787[Gao J,Wang JN,Xu B,Xie Y,He JD,Wu Y.Plant leaf traits,height and biomass partitioning in typical ephemerals under different levels of snow cover thickness in an alpine meadow[J].Chin J Plant Ecol,2016,40(8):775-787]
16 Groisman PY,Karl TR,Knight RW,Stenchikov GL.Changes of snow cover,temperature,and radiative heat-balance over the northernhemisphere[J].J Climate,1994,7(11):1633-1656
17杨玉莲,吴福忠,何振华,徐振锋,刘洋,杨万勤,谭波.雪被去除对川西高山冷杉林冬季土壤微生物生物量碳氮和可培养微生物数量的影响[J].应用生态学报,2012,23(7):1809-1816[Yang YL,Wu FZ,He ZH,Xu ZF,Liu Y,Yang WQ,Tan B.Effects of snow pack removal on soil microbial biomass carbon and nitrogen and the number of soil culturable microorganisms during wintertime in alpine Abies faxoniana forest of western Sichuan,Southwest China[J].Chin J Appl Ecol,2012,23(7):1809-1816]
18 Schmidt SK,Lipson DA.Microbial growth under the snow:implications for nutrient and allelochemical availability in temperate soils.Plant Soil,2004,259:1-7
19卫云燕,尹华军,刘庆,黎云祥.气候变暖背景下森林土壤碳循环研究进展[J].应用与环境生物学报,2009,15(6):888-894[Wei YY,Yin HJ,Liu Q,Li YX.Advance in research of forest carbon cycling under climate warming[J].Chin J Appl Environ Biol,2009,15(6):888-894]
20 Tomonori S.Inf luences of subtropical jet and Tibetan Plateau on precipitation pattern in Asia,insights from regional climate modeling.Quaternary Intern,2009,194:148-158
21 Dunne JA,Harte J,Taylor KJ.Subalpine meadow flowering phenology responses to climate change:integrating experimental and gradient methods[J].Ecol Monogr,2003,73(1):69-86
22谭波,吴福忠,杨万勤,杨玉莲,王奥,康丽娜.雪被去除对川西高山森林冬季土壤温度及碳、氮、磷动态的影响[J].应用生态学报,2011,22(10):2553-2559[Tan B,Wu FZ,Yang WQ,Yang YL,Wang A,Kang LN.Effects of snow pack removal on the dynamics of winter-time soil temperature,carbon,nitrogen,and phosphorus in alpine forests of west Sichuan[J].Chin J Appl Ecol,2011,22(10):2553-2559]
23彭艳,杨万勤,薛樵,李俊,王滨,谭波,吴福忠.季节性冻融期间土壤动物对高山草甸两种凋落叶木质素降解的影响[J].应用与环境生物学报,2016,22(2):300-306[Peng Y,Yang WQ,Xue Q,Li J,Wang B,Tan B,Wu FZ.Impact of soil fauna on lignin degradation of two foliar litters in an alpine meadow during freezing-thawing period[J].Chin JAppl Environ Biol,2016,22(2):300-306]
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