Structure and Dynamic Characteristics of Shrub Patch in the Water-wind Erosion Crisscross Region
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【Author in Chinese】 郝红敏；
【Author's Information】 西北农林科技大学， 生理生态学， 2017， 硕士
【Abstract in Chinese】 随着全球变暖和人类活动对自然环境破坏加剧,土壤沙漠化日益严重。黄土高原地区,尤其是水蚀风蚀交错带正面临着水土流失、生态环境恶化等生态问题,严重危及到当地人民的生存和发展。灌丛斑块对维护黄土高原水蚀风蚀交错带的生态系统稳定性和恢复发挥着重要作用。本研究选取黄土高原水蚀风蚀交错带沙坡地沙蒿半灌木为建群种的灌丛斑块作为研究对象,通过分析不同演替阶段斑块空间分布格局特征、斑块数量动态规律和群落结构,旨在为揭示水蚀风蚀交错带植被恢复机理提供理论依据。本研究取得的主要结论如下:(1)灌丛斑块的空间分布格局表现为:灌丛斑块演替初期,小灌丛斑块(灌丛体积立方根d<60 cm)表现为聚集分布,到演替后期聚集程度减弱,大灌丛斑块(d>95cm)主要表现为均匀分布,演替末期逐渐发展为空间随机分布。分析灌丛斑块的空间关联特征,结果表明:除中灌丛斑块(60 cm<d≤95 cm)与大灌丛斑块呈空间负相关外,其余各斑块间均呈空间正相关。(2)灌丛斑块数量结构呈金字塔型,小灌丛斑块和中灌丛斑块占总斑块数量的77%,数量结构呈现微弱的增长型。灌丛斑块存活曲线为Deevey-II型。生存函数分析表明:灌丛斑块生存率函数单调下降,累积死亡率函数单调上升,死亡密度函数则较为平缓,危险率函数随灌丛斑块大小级的增加呈上升的趋势。(3)灌丛斑块内植物多样性、地上/地下生物量及土壤含水量均显著高于裸地斑块(P<0.05),且随灌丛斑块的增大呈增加的趋势。黄土高原水蚀风蚀交错带灌丛斑块显著改善了微生境,进而促进灌丛斑块的演替过程。作为植物群落次生演替的先锋植物,沙蒿灌丛斑块对水蚀风蚀交错带生态系统的维持和恢复发挥重要作用。小范围(0-10 m)尺度下,演替阶段和斑块间相互作用决定了灌丛斑块的空间分布格局;灌丛斑块的结构动态揭示了沙蒿灌丛斑块在研究区内生长更新良好,能够适应当地气候环境,种群处于稳定增长状态。而且,灌丛斑块对微生境的改善作用,即提高植物多样性、地上地下生物量和土壤含水量,随灌丛斑块演替呈增大趋势,有助于其它植物的定居,促进水蚀风蚀交错带退化生态系统的恢复。
【Abstract】 Soil desertification has become a serious environmental problem with increasing global warming and human activity.Especially wind-water erosion crisscross region on the Loess Plateau is facing the deterioration of environment,such as soil erosion and other ecological problems,which was a threat to the survival and development of local residents.Shrub patch plays an important role in ecosystem stability and vegetation recovery in water-wind erosion crisscross zone.Artemisia ordosica shrub patch was the dominant landscape in water-wind erosion region in Loess plateau.We studied the spatial pattern,number structure,and the micro-habitat(species diversity,biomass,and soil water content,etc.)of shrub patch in different stage,trying to reveal vegetation restoration mechanism in the water-wind erosion crisscross zone.The main results of this paper are as follows:(1)The spatial distribution characteristics of shrub patches in the study area showed that,at the early successional stage,the small shrub patches(cube root volume d < 60 cm)were spatial aggregation,then the strength of aggregation decreased at the later successional stage,while large shrub patches(d ≥ 95 cm)were regularly distributed and the dead shrub patches(d ≥ 95 cm)were randomly distributed in last phase.The spatial association of the shrub patches showed positive spatial relationship between different sizes shrub patches,except that the middle shrub patches(60 cm< d ≤ 95 cm)were negatively related to large shrub patches(d > 95 cm).(2)The number structure of the shrub patches was a pyramid,and the small and medium shrub patches accounted for 77% of the total,and the growth of patches structure was low.Survival curve was Deevey-type II.Survival function analysis showed that shrub patches survival rate function monotonically decreased.Cumulative mortality function monotonically increased.Mortality density function has little difference in all the shrub patches.Risk rate function showed increasing trend with increasing size of shrub patch.(3)The Shannon-wiener index,richness index,biomass and soil water content were higher in shrub patch than those in the bare land patch.With the increasing size of shrub patches,the indices increased.Shrub patch ameliorated micro-habitat obviously in wind-water erosion crisscross region in Loess Plateau,and then benefit the process of shrub patch succession.As the pioneer species of plant community in secondary succession,Artemisia ordosica shrub patch plays an important role in the stability of the ecosystem in the cross areas of wind-water erosion in Loess Plateau in China.Succession stage and interaction of shrub patches determined the spatial pattern of shrub patch in small spatial scale(0-10 m).The shrub patch could grow,renew,and adapt in the cross areas of wind-water erosion climate environment,and the population was in stable increasing situation.Therefore,shrub patch can improve plant diversity,above-and below-ground biomass,and soil water content and these indices increased in shrub patch succession.The amelioration of shrub patch to micro-habitat would contribute to the settlement of other plants and accelerate the ecosystem recover in the cross areas of wind-water erosion.