-
灌丛化(Shrub encroachment)指以木本植被的盖度、密度和生物量增加为主要特征的全球化现象[1]。最早的“灌丛化”现象可追溯到19世纪后期,距今已有150~200年的历史。草地灌丛化的发生范围多集中在干旱与半干旱的草原生态系统,在纬度较高的苔原等区域中也有出现,以草地生态系统为主,具有发生范围广、发展迅速等特点[2],并且灌丛化的趋势仍在加快。例如,在澳大利亚,Mesquiet植物每年大约以0.4%~1.2%的速度扩张[3]。在北美,灌丛化的总面积约为3.3×108 hm2,每年以0.2%~0.5%的速度增长[4]。在我国,草地灌丛化的现象同样分布广泛,如内蒙古草原[5]、贵州高原[6]、川西高寒草地[7]等地。但目前我国对草地灌丛化的研究还较为薄弱,没有形成系统的理论支撑。因此,本文就国内外已有的有关灌丛化成因及影响的研究动态进行综述,对草地灌丛成因及其对草地生态系统的影响进行了阐明,并提出了相关对策,旨在为我国草地灌丛化研究提供理论参考及展望,同时对我国的草原生产区的恢复、治理与管理提供科学依据。
Review on Causes and Consequences of Shrub Encroachment into Grassland
More Information-
摘要: 草地灌丛化作为全球普遍发生的现象,已成为全球性的问题,同时也是全球变化生态学,草地生态学,物候学,旅游学,畜牧学研究的热点问题。其定义为草地生态系统中木本植物的生物量、密度和盖度的增加导致草本植物生物量、密度和盖度减少的现象。草地灌丛化是气候变化、过度放牧和火烧等互相作用的结果。草地灌丛化导致草原土地格局和生物格局发生改变,表现出“沃岛”效应、草原生物多样性以及草地生产力的变化。未来草地灌丛化研究应该聚焦于草地灌丛化的机理、对草地-灌木生态系统的地上、地下部分的影响以及相应的管理措施,研究结果对我国的草原生产区生态管理和恢复具有非常重要的意义。Abstract: Shrub encroachment is an universal phenomenon, which has become a global problem, and a hot issue in the study of global change ecology, grassland ecology, phenology, tourism and animal husbandry. It is defined as the increase of woody biomass, density and coverage, but the decrease of herbaceous biomass, density and coverage in grassland ecosystems. Shrub encroachment is the result of the interaction of overgrazing, fire and climate change. The shrub encroachment causes the change of grassland land patterns and biological patterns, which results in the fertile island effect, the change of grassland biodiversity and grassland productivity. In the future research, more work should be emphasized on the mechanisms of shrub encroachment, influences on the aboveground and belowground parts of grassland-shrub ecosystems and management approach of shrub encroachment, which is of great significance to the grassland production areas in China.
-
Key words:
- Shrub encroachment;
- Shrub encroachment mechanism;
- Overgrazing;
- Fire;
- Climate change
-
[1] Van Auken O W. Causes and consequences of woody plant encroachment into western North American grasslands[J]. Journal of Environmental Management, 2009, 90(10): 2931−2942. doi: 10.1016/j.jenvman.2009.04.023 [2] Naito A T, Cairns D M. Patterns and processes of global shrub expansion[J]. Progress in Physical Geography, 2011, 35(4): 423−442. doi: 10.1177/0309133311403538 [3] Robinson T P, Van Klinken R D, Metternicht G. Spatial and temporal rates and patterns of mesquite (Prosopis species) invasion in Western Australia[J]. Journal of Arid Environments, 2008, 72(3): 175−188. doi: 10.1016/j.jaridenv.2007.05.011 [4] Knapp A K, Briggs J M, Collins S L, et al. Shrub encroachment in North American grassland: shift in growth from dominance rapidly alters control of ecosystem carbon inputs[J]. Global Change Biology, 2008, 14(3): 615−623. doi: 10.1111/j.1365-2486.2007.01512.x [5] 熊小刚,韩兴国. 运用状态与过渡模式讨论锡林河流域典型草原的灌丛化[J]. 草业学报,2006,15(2):9−13. doi: 10.3321/j.issn:1004-5759.2006.02.002 [6] Ding L, Wang P, Zhang W, Zhang Y, Li S, Wei X, Chen X, Zhang Y, Yang F. Shrub Encroachment Shapes Soil Nutrient Concentration, Stoichiometry and Carbon Storage in an Abandoned Subalpine Grassland[J]. Sustainability, 2019, 11(6): 1−17. [7] 马文明,刘军,周青平,陈红,刘超文. 高寒草地灌丛化对土壤团聚体稳定性及有机碳分布特征的影响[J]. 土壤通报,2019,50(5):1108−1115. doi: 10.19336/j.cnki.trtb.2019.05.14 [8] 王庆辉,窦学诚,龚大鑫. 高寒牧区草地沙化问题研究—以玛曲草原为例[J]. 干旱区地理,2012,35(2):302−308. [9] Kuechly H U, Mueller J S, Reinfelder V L, et al. Rodent‐mediated dispersal of Acacia seeds in Kalahari savannah rangelands-implications for bush encroachment[J]. African Journal of Ecology, 2011, 49(1): 119. doi: 10.1111/j.1365-2028.2010.01230.x [10] Holland E A, Detling J K. Plant response to herbivory and below ground nitrogen cycling[J]. Ecology, 1990, 71(3): 1040−1049. doi: 10.2307/1937372 [11] 杨维康,蒋慧萍,乔建芳. 放牧对准噶尔荒漠植物群落及土壤特性的影响[J]. 干旱区地理,2008,31(5):659−664. [12] Smith R, Tighe M, Reid N, et al. Effects of grazing, trenching and surface soil disturbance on ground cover in woody encroachment on the Cobar Pedingplain, south-eastern Australia[J]. Journal of Arid Environments, 2013, 96: 80−86. doi: 10.1016/j.jaridenv.2013.04.006 [13] Skapre C. Shrub Layer Dynamics Under Different Herbivore Densities in an Arid Savanna, Botswana[J]. Journal of Applied Ecology, 1990, 27(3): 873−885. doi: 10.2307/2404383 [14] BROWN J, ARCHER S. Woody plant invasion of grasslands: establishment of honey mesquite (Prosopis glandulosa var. glandulosa) on sites differing in herbaceous biomass and grazing history[J]. Oecologia, 1989, 80(1): 19−26. doi: 10.1007/BF00789926 [15] Booysen P V D, Tainton N M. Ecological effects of fire in South African ecosystems[M]. Springer Science & Business Media, 2012. [16] Smit I P J, Asner G P, Govender N, et al. An examination of the potential efficacy of high‐intensity fires for reversing woody encroachment in savannas[J]. Journal of Applied Ecology, 2016, 53(5): 1623−1633. doi: 10.1111/1365-2664.12738 [17] Sankaran M, Hanann P, Scholes R J, et al. Determinants of woody cover in African savannas[J]. Nature, 2005, 438(7069): 846−849. doi: 10.1038/nature04070 [18] D’Odorico P, Okin G S, Bestelmeyer B T. A synthetic review of feedbacks and drivers of shrub encroachment in arid grasslands[J]. Ecohydrology, 2012, 5(5): 520−530. doi: 10.1002/eco.259 [19] Peters D P C, Yao J, Gosz J R. Woody plant invasion at a semi-arid/arid transition zone: importance of ecosystem type to colonization and patch expansion[J]. Journal of Vegetation Science, 2006, 17(3): 389−396. doi: 10.1111/j.1654-1103.2006.tb02459.x [20] Craine J M, Towne E G, Nippert J B. Climate controls on grass culm production over a quarter century in a tallgrass prairie[J]. Ecology, 2010, 91(7): 2132−2140. doi: 10.1890/09-1242.1 [21] Huang H, Anderegg L D L, Dawson T E, et al. Critical transition to woody plant dominance through microclimate feedbacks in North American coastal ecosystems[J]. Ecology, 2020, 101(9): e03107. [22] martinez J V, Pockman W T. The vulnerability to freezing-induced xylem cavitation of Larrea tridentata (Zygophyllaceae) in the Chihuahuan desert[J]. American Journal of Botany, 2002, 89(12): 1916−1924. doi: 10.3732/ajb.89.12.1916 [23] Sekhwela M, Yates D J. A phenological study of dominant acacia tree species in areas with different rainfall regimes in the Kalahari of Botswana[J]. Journal of Arid Environments, 2007, 70(1): 1−17. doi: 10.1016/j.jaridenv.2006.12.006 [24] Sanz-Elorza M, Dana E d, González A, Sobrino E. Changes in the high mountain vegetation of the Central Iberian Peninsula as a probable sign of global warming[J]. Annals of Botany, 2003, 92(2): 273−280. doi: 10.1093/aob/mcg130 [25] Buitenwerf R, Bond W J, Stevens N, et al. Increased tree densities in South African savannas: >50years of data suggests CO<sub>2</sub> as a driver[J]. Global Change Biology, 2012, 18(2): 675−684. doi: 10.1111/j.1365-2486.2011.02561.x [26] Morgan J A, Milchunas D G, Lecaain D R, et al. Carbon dioxide enrichment alters plant community structure and accelerates shrub growth in the shortgrass steppe[J]. Proc Natl Acad Sci U S A, 2007, 104(37): 14724−14729. doi: 10.1073/pnas.0703427104 [27] Drake B G, Gonzalezmeler MA, Long S P. More efficient plants: A consequence of rising atmospheric CO<sub>2</sub>?[J]. Annual Review of Plant Physiology and Plant Molecular Biology, 1997, 48: 609−639. doi: 10.1146/annurev.arplant.48.1.609 [28] Mooney H A, Cleland E E. The evolutionary impact of invasive species[J]. Proceedings of the National Academy of Sciences of the United States of America, 2001, 98(10): 5446−5451. doi: 10.1073/pnas.091093398 [29] Darrouzet A N, D'antonio C M, Dawson T E. Depth of water acquisition by invading shrubs and resident herbs in a Sierra Nevada meadow[J]. Plant and Soil, 2006, 285(1): 31−43. [30] Duniway M C, Snyder K A, Herrick JE. Spatial and temporal patterns of water availability in a grass-shrub ecotone and implications for grassland recovery in arid environments[J]. Ecohydrology, 2010, 3(1): 55−67. [31] Masocha M, Dube T, Skidmore A, Holmgren M, Prins H. Assessing effect of rainfall on rate of alien shrub expansion in a southern African savanna[J]. African Journal of Range and Forage Science, 2017, 34(1): 1−6. doi: 10.2989/10220119.2017.1301551 [32] 刘峻杉,徐霞,张勇,田玉强,高琼. 长期降雨波动对半干旱灌木群落生物量和土壤水分动态的效应[J]. 中国科学:生命科学,2010,40(2):166−174. [33] Smith S D, Huxman T E, Zitzer S F, et al. Elevated CO<sub>2</sub> increased productivity and invasive species success in an arid ecosystem[J]. Nature, 2000, 408(6808): 79−82. doi: 10.1038/35040544 [34] 熊小刚,韩兴国. 生态学中的新领域——沃岛效应与草原灌丛化[J]. 植物杂志,2003(2):45−46. [35] Bhark E W, Small E E. Association between plant canopies and the spatial patterns of infiltration in shrubland and grassland of the Chihuahuan Desert, New Mexico[J]. Ecosystems, 2003, 6(2): 185−196. doi: 10.1007/s10021-002-0210-9 [36] Schlesinger W H, Raikes J A, Hartley A E, et al. On the spatial pattern of soil nutrients in desert ecosystems[J]. Ecology, 1996, 77(2): 364−374. [37] Davidj E, Walterg W, Benjamind D. Animal disturbances promote shrub maintenance in a desertified grassland. Journal of Ecology, 2009, 97(6) : 1302-1310. [38] Hibbard K A, Archer S, Schimel D S, Valentine D W. Biogeochemical changes accompanying woody plant encroachment in a subtropical savanna. Ecology, 2001, 82(7): 1999- 2011. [39] Zarovalli M P, Yiakoulaki M D, Papanastasis V P. Effects of shrub encroachment on herbage production and nutritive value in semi-arid Mediterranean grasslands[J]. Grass and Forage Science, 2007, 62(3): 355−363. doi: 10.1111/j.1365-2494.2007.00590.x [40] Ratajcazak Z, Nippert J B, Collins S L. Woody encroachment decreases diversity across North American grasslands and savannas[J]. Ecology, 2012, 93(4): 697−703. doi: 10.1890/11-1199.1 [41] Zavaleta E S, Kettley L S. Ecosystem change along a woody invasion chronosequence in California grassland[J]. Journal of Arid Environments, 2006, 66(2): 290−306. doi: 10.1016/j.jaridenv.2005.11.008 [42] Howard K S C, Eldridge D J, Soliveres S. Positive effects of shrubs on plant species diversity do not change along a gradient in grazing pressure in an arid shrubland[J]. Basic and Applied Ecology, 2012, 13(2): 159−168. doi: 10.1016/j.baae.2012.02.008 [43] Brantley S T, Young D R. Contribution of sunflecks is minimal in expanding shrub thickets compared to temperate forest[J]. Ecology, 2009, 90(4): 1021−1029. doi: 10.1890/08-0725.1 [44] Brantley S T, Young D R. Leaf-area index and light attenuation in rapidly expanding shrub thickets[J]. Ecology, 2007, 88(2): 524−530. doi: 10.1890/06-0913 [45] 关林婧,梅续芳,张媛嫒,等. 狭叶锦鸡儿灌丛沙堆土壤水分和肥力的时空分布[J]. 干旱区研究,2016,33(2):253−259. doi: 10.13866/j.azr.2016.02.05 [46] Veach A M, Dodds W K, Adam S, et al. Fire and Grazing Influences on Rates of Riparian Woody Plant Expansion along Grassland Streams[J]. Plos One, 2014, 9(9): e0129409. [47] Collins S L, Nippert J B, Blair J M, et al. Fire frequency, state change and hysteresis in tallgrass prairie[J]. Ecology Letters, 2021, 24(4): 636−647. doi: 10.1111/ele.13676 [48] 林燕,白永飞. 内蒙古典型草原小叶锦鸡儿灌丛地上净初级生产力和种群结构对火烧的响应[J]. 草业学报,2010,19(5):170−178. doi: 10.11686/cyxb20100523 [49] Müller B, Frank K, Wissel C. Relevance of rest periods in non-equilibrium rangeland systems-A modelling analysis[J]. Agricultural systems, 2007, 92(1): 295−317. [50] Quaas M F, Baumgärtner S. Optimal grazing management rules in semi-arid rangelands with uncertain rainfall[J]. Natural Resource Modeling, 2012, 25(2): 364−387. doi: 10.1111/j.1939-7445.2011.00110.x [51] Zhang Y, Gao Q, Xu L, Yu M, Tian Y Q. Shrubs proliferated within a six-year exclosure in a temperate grassland-spatiotemporal relationships between vegetation and soil variables[J]. Sciences in Cold and Arid Regions, 2014, 6(2): 139−149.