灌丛资源及其管理利用研究进展

灌丛是中国山地和干旱地区的常见植被类型,分布范围广泛、生态功能多样、经济价值可观。然而,自然资源、生态环境、国民经济等相关部门多将灌丛拆分归属于森林或草原,其重要性未能充分体现。学术界有关灌丛资源的概念、内涵未有明确统一共识,基于资源属性特点的灌丛资源分区分类体系尚未建立。草原灌丛化的发生范围、速度及其生态影响不够明确,严重影响灌丛资源的高效保护、科学管理与可持续利用。这已然成为亟需凝聚共识和深入探究的理论技术难点与实践问题。建议在科学界定灌丛资源的概念内涵、建立健全灌丛资源分类体系基础上,深入发展和应用灌丛植被多基遥感和人工智能识别技术,科学掌握不同区域灌丛变化特别是草原灌丛化的过程及原因,全面系统地评估灌丛化的生态经济影响,优化分区分类灌丛管理利用策略,促进灌丛资源可持续管理和利用。

藏东南施工便道植被恢复对坡面水土流失的影响

[目的]明晰施工便道上、下边坡在植被恢复条件下的坡面产流产沙过程,揭示施工便道建设扰动后植被恢复对藏东南生态脆弱的亚高山森林灌丛区坡面尺度水土流失的影响,为施工便道工程扰动后水土流失防治和植被恢复提供理论依据。[方法]选取施工便道上、下边坡扰动后不同植被恢复条件下的典型坡面,进行室内模拟降雨试验,研究工程扰动后上、下边坡4种植被覆盖度(0%,30%,60%,90%),3种坡度(15°,30°,45°),2种雨强(30,60 mm/h)条件下的坡面产流产沙过程,明确施工便道植被恢复对水土流失的影响。[结果](1)施工便道工程扰动后,在上、下边坡裸土坡面进行植被恢复能有效延缓初始产流时间,随着植被覆盖度增加,延缓初始产流时间的效果增强,且植被的延缓产流效应在上边坡更为明显。(2)在0%~60%植被覆盖度范围内,上、下边坡稳定产流速率随植被覆盖度的增加而显著降低,60%与90%植被覆盖度的稳定产流速率接近。相比裸土坡面,60%,90%植被覆盖度的减流效益分别为59%~75%,58%~77%,表明减流作用的植被临界覆盖度为60%。(3)植被覆盖度为30%,60%时,减沙效益分别达到29%~82%,86%~96%。植被覆盖度在60%以下,当覆盖度增加,减沙作用显著增强,超过此临界覆盖度,即使增加覆盖度,其减沙效益也变化不大。(4)在相同植被覆盖度、坡度和雨强条件下,挖方形成的上边坡总产流量总是高于填方形成的下边坡,而下边坡总产沙量始终高于上边坡,反映出施工便道扰动后,挖方、填方边坡在坡面土壤侵蚀方面的显著差异。[结论]在藏东南施工便道扰动区的水土流失防治中,60%植被恢复率兼具较好的防治效益和经济可行性,且在水土保持措施布设时,挖方边坡更需要“控水”而填方边坡应偏重“阻沙”,只有充分考虑其差异才能在施工便道扰动区达到更好的水土保持效果。

Climate and topography regulate the spatial pattern of soil salinization and its effects on shrub community structure in Northwest China

Soil salinization may affect biodiversity and species composition,leading to changes in the plant community structure.However,few studies have explored the spatial pattern of soil salinization and its effects on shrub community structure at the ecosystem scale.Therefore,we conducted a transect sampling of desert shrublands in Northwest China during the growing season(June–September)in 2021.Soil salinization(both the degree and type),shrub community structure(e.g.,shrub density and height),and biodiversity parameters(e.g.,Simpson diversity,Margalf abundance,Shannon-Wiener diversity,and Pielou evenness indices)were used to assess the effects of soil salinization on shrub community structure.The results showed that the primary degree of soil salinization in the study area was light salinization,with the area proportion of 69.8%.Whereas the main type of soil salinization was characterized as sulfate saline soil,also accounting for 69.8%of the total area.Notably,there was a significant reduction in the degree of soil salinization and a shift in the type of soil salinization from chloride saline soil to sulfate saline soil,with an increase in longitude.Regional mean annual precipitation(MAP),mean annual evapotranspiration(MAE),elevation,and slope significantly contributed to soil salinization and its geochemical differentiation.As soil salinization intensified,shrub community structure displayed increased diversity and evenness,as indicated by the increases in the Simpson diversity,Shannon-Wiener diversity,and Pielou evenness indices.Moreover,the succulent stems and leaves of Chenopodiaceae and Tamaricaceae exhibited clear advantages under these conditions.Furthermore,regional climate and topography,such as MAP,MAE,and elevation,had greater effects on the distribution of shrub plants than soil salinization.These results provide a reference for the origin and pattern of soil salinization in drylands and their effects on the community structure of halophyte shrub species.

荒漠豆科灌丛根际土壤氨氧化和反硝化微生物功能基因丰度及群落多样性特征

为探索宁夏荒漠草原豆科灌丛根际土壤中参与氨氧化和反硝化的微生物功能基因丰度和群落组成对植物类型和生长时期的响应特征,本研究以宁夏白芨滩国家级自然保护区内典型的豆科灌丛群落柠条、沙冬青、猫头刺和毛刺不同生长时期(营养期、盛花期和果实期)的根际土壤为材料,通过功能基因实时荧光定量PCR和高通量测序方法,分析4种灌丛根际土壤中氨氧化和反硝化微生物功能基因丰度、群落结构组成特征及其与土壤因子的相关性。结果表明,功能基因丰度及群落结构因灌丛类型和生长时期不同而存在差异。柠条灌丛根际土壤中各功能基因丰度显著高于其他3种灌丛,且在盛花期达到最高。柠条各生长期根际土壤中氨氧化细菌(ammonia-oxidizing bacteria,AOB)群落多样性高于其他灌丛类型,而毛刺根际氨氧化古菌(ammonia-oxidizing archaea,AOA)和nirK型反硝化菌群落多样性最低。各灌丛根际AOA以未分类类群为绝对优势,占79.34%~98.37%,奇古菌门和泉古菌门分别仅占0.28%~20.37%和0.28%~2.35%;AOB在柠条根际以变形菌门为优势,其他3种植物根际则以未分类类群为优势;nirK和nirS型反硝化菌均以变形菌门为优势门,但nirK型反硝化菌的组成受植物类型和生长时期的影响更显著。功能基因的丰度与土壤全氮、速效钾和pH显著正相关。全钾、速效钾、有机质显著影响氨氧化微生物的群落组成,pH是反硝化微生物群落结构的主要影响因子。

Diurnal and seasonal dynamics of soil respiration in desert shrubland of Artemisia Ordosica on Ordos Plateau of Inner Mongolia, China

The diurnal and seasonal dynamics of soil respiration in the A. ordosica shrubland on Ordos Plateau were investigated in the growing season （May-October） of 2006 and their environmental driving factors were also analyzed, Results indicated that diurnal dynamics of soil respiration rate and its temperature dependence showed some discrepancy in two different growth stages （the vegetative growth stage and the reproductive growth stage）. During the vegetative growth stage, the diurnal variation of soil respiration was slight and not correlated with the daily temperature change, but during the reproductive growth stage, the daily respiration variation was relatively large and significantly correlated with the diurnal variation of air and soil temperature. In the growing season, the peak value of soil respiration occurred at July and August because of the better soil water-heat conditions and their optimal deployment in this period. In the shrubland ecosystem, precipitation was the switch of soil respiration pulses and can greatly increase soil respiration rates after soil rewetting. Moreover, the soil respiration rates in the growing season and the air temperature and soil surface water content were closely correlated （p〈0.05） each other. The stepwise regression model indicated that the variation of soil surface moisture accounted for 41.9% of the variation in soil respiration （p〈0.05）.

Impact of Gully on Soil Moisture of Shrubland in Wind-Water Erosion Crisscross Region of the Loess Plateau

The most serious erosion on the Loess Plateau of China exists in the wind-water erosion crisscross region where the annual precipitation is about 400 mm,the ecological environment is very fragile,and water is the key limiting factor for improving the environment. In this study,changes of soil moisture content for Caragana korshinskii Kom. shrubland in the gully bank of the Loess Plateau were studied using the methods of soil sampling and neutron probe. A typical gully(75 m long,28 m wide,and 10 m deep) was selected,and six neutron probe access tubes(6 m long) were installed at points 50,100,200,300,400,and 500 cm from the gully border for obtaining soil moisture data from July to October 2004 at approximately 10 d intervals. Soil samplings were simultaneously carried out for moisture determination at the six points. Results showed that the soil moisture of the shrubland in the gully bank significantly varied between 300 and 400 cm in the horizontal direction and up to 600 cm in vertical direction of the gully. Seasonal changes in soil moisture revealed a curve with a single peak that occurred at the end of August or early September. A linear regression equation was fit for soil water storage and the distance from the gully border,with coefficients depending on rainfall characteristics,sampling point,and time of measurement.

Plant water use strategies in the Shapotou artificial sand-fixed vegetation of the southeastern margin of the Tengger Desert, northwestern China

Stable oxygen and hydrogen isotopic compositions(δ^(18)O and δD) of plant xylem water and its potential water sources can provide new information for studying water sources, competitive interactions and water use patterns of plants. The contributions of different water sources to three plants, Hedysarum scoparium(HS), Caragana Korshinskii(CK) and Artemisia ordosica(AO), were investigated in the artificial sand-fixed vegetation of Shapotou, the southeastern margin of the Tengger Desert of northwestern China, based on meteorological data and δ^(18)O and δD values of precipitation, groundwater, soil water and xylem water of HS, CK and AO. Our results indicated that soil water infiltration through precipitation was the main water source of the artificial sand-fixed vegetation. Obvious differences in soil water content and in δ^(18)O of soil water and xylem water were found among different seasons. No relationship was found between the δ^(18)O in plant xylem water and in soil water in January. The same water use patterns were found in CK, HS and AO in May, suggesting they have the same water sources. The different water sources of CK, HS and AO in August indicate that water competition occurred. In addition, the main water sources of CK, HS and AO in August mainly come from shallow soil water, while they use relatively deep soil water in May. This phenomenon is related to the differences of soil water content throughout soil profile, precipitation, transpiration and water competition under different growth periods. The water use patterns of CK, HS and AO respond to soil water content throughout the soil profile and their competition balance for water uptake during different growth season. The results indicate that these sandfixed plants have developed into a relatively stable stage and they are able to regulate their water use behavior as a response to the environmental conditions, which reinforces the effectiveness of plantation of native shrubs without irrigation in degraded areas.

Effects of sand-fixing and windbreak forests on wind flow:a synthesis of results from field experiments and numerical simulations

Sand-fixing and windbreak forests are widely used to protect or/and improve the ecological environments in arid and semi-arid regions. A full understanding of wind flow characteristics is essential to arranging the patterns of these protective forests for enhancing the effectiveness. In this study, the wind velocity over the underlying surface with sand-fixing forests and windbreak forests at the heights of 1–49 m was monitored from two 50-m high observation towers in an oasis of Minqin, Gansu Province of China. The wind velocities were simulated at different locations over these protective forests between those two towers by a two-dimensional Computational Fluid Dynamics（CFD） model. The results showed that at the heights of 1–49 m, the wind velocity profiles followed a classical logarithm law at the edge of the oasis and a multilayer structure inside the oasis. With increasing number of sand-fixing forest and windbreak forest arrays, the wind velocity at the heights of 1–49 m generally decreased along the downstream direction of the prevailing wind. Specifically, below the height of windbreak forests, the wind velocity decelerates as the airflow approaches to the windbreak forests and then accelerates as the airflow passes over the windbreak forests. In contrast, above the height of windbreak forests, the wind velocity accelerates as the airflow approaches to the windbreak forests and then generally decelerates as the airflow passes over the windbreak forests. Both the array number and array spacing of sand-fixing and windbreak forests could influence the wind velocity. The wind protection effects of sand-fixing forests were closely related to the array spacing of windbreak forests and increased with the addition of sand-fixing forests when the array of the forests was adequately spaced. However, if the array spacing of windbreak forests was smaller than seven times of the heights of windbreak forests, the effects were reduced or completely masked by the effects of windbreak forests. The results could offer theoretical guidelines on how to systematically arrange the patterns of sand-fixing and windbreak forests for preventing wind erosion in the most convenient and the cheapest ways.

Wind-proof and sand-fixing effects of Artemisia ordosica with different coverages in the Mu Us Sandy Land,northern China

Wind erosion is a key global environmental problem and has many adverse effects.The Mu Us Sandy Land of northern China is characterized by an arid climate,where vegetation patches and bare sand patches are usually distributed mosaically,and aeolian activities occur frequently.Vegetation plays a significant role in controlling wind erosion.Artemisia ordosica is the most dominant native plant species in the Mu Us Sandy Land.It is urgent to study the wind-proof and sand-fixing effects of Artemisia ordosica in the Mu Us Sandy Land.This study analyzed the wind-proof and sand-fixing effects of Artemisia ordosica based on the field data of wind regimes,aeolian sediment transport,and surface change of Artemisia ordosica plots with four coverages(denoted as site A,site B,site C,and site D)in the Mu Us Sandy Land during the period from 1 June 2018 to 29 June 2019.The coverages of Artemisia ordosica at site A,site B,site C,and site D were 2%,16%,29%,and 69%,respectively.The annual average wind speeds at 2.0 m height above the ground for site A,site B,site C,and site D were 3.47,2.77,2.21,and 1.97 m/s,respectively.The annual drift potentials were 193.80,69.72,15.05,and 6.73 VU at site A,site B,site C,and site D,respectively.The total horizontal aeolian sediment fluxes during the period from 2-3 June 2018 to 6 June 2019 at site A,site B,site C,and site D were 4633.61,896.80,10.54,and 6.14 kg/m,respectively.Site A had the largest surface changes,and the surface changes at site B were significantly weaker than those at site A,whereas the surface changes at site C and site D were minimal.The results indicated that Artemisia ordosica significantly reduced the wind speed,drift potential,aeolian sediment transport,and surface changes.The higher the coverage of Artemisia ordosica is,the more obvious the effects of wind-proof and sand-fixing.Wind erosion would be effectively controlled in the Mu Us Sandy Land if the coverage of Artemisia ordosica is greater than 29%.These results provide a scientific basis for evaluating the ecosystem service function of Artemisia ordosica and the vegetation protection and construction projects in the Mu Us Sandy Land.

Preparation and Water Retention Properties of Clay-based Sand-fixing and Grass-planting Materials

Targeting the problem of available water conservation in sand fixation, the sand-fixing and grass-planting materials were prepared with clay modified by emulsifying vegetable waxes and octylphenol polyoxyethylene ether （OP4）. The water retention property was studied in simulating desertification environmental climate and the materials were characterized by means of UV-Vis, SEM, FTIR, XRD and TGA measurements. The experimental result showed that the materials had excellent water retention properties, due to that vegetable waxes adhered evenly to clay particle surfaces, made the clay pores changing from hydrophilic to hydrophobic and so inhibited the water evaporation. Grass-planting experiment showed that, with reasonable mass ratio of clay, vegetable waxes and surfactant, the materials not only inhibited water evaporation but also maintained sound air permeability so shat the germination rate and survival rate of grass were significantly improved.

Sand-fixing characteristics of Carex brunnescens and its application with straw checkerboard technique in restoration of degraded alpine meadows

Carex brunnescens（Pers.）, a typical clonal species, is considered to be the only herb found to date that can develop on sand dunes in Maqu alpine region of northwestern China. However, the characteristics that C. brunnescens resists to harsh alpine environment have not been documented. In this study, we conducted a field investigation to determine the morphological, reproductive, and sand-fixing characteristics of C. brunnescens. Concomitantly, we transplanted the belowground rhizomes of C. brunnescens to sand dunes and compared the abilities to restore degraded alpine meadows among sand dunes that had no further treatment（SD＋N）, sand dunes that had straw checkerboard technique but no transplanted rhizomes of C. brunnescens（SD＋SCT）, and sand dunes that had both SCT and transplanted rhizomes of C. brunnescens（SD＋SCT＋P）. We found that belowground vertical rhizomes and horizontal rhizomes（including branching rhizomes and main rhizomes） of C. brunnescens were highly developed and that population reproduction was dominated by horizontal rhizomes. C. brunnescens exhibited a significant sand-fixation effect under following conditions： population density was 145–156 ramets/m^2, vegetation cover was 31.2%–39.3%, total length of belowground rhizomes was 11,223 cm/m^2, total length of belowground first-order roots was 9161–10,524 cm/m^2, fresh weight of aboveground part was 198.5–212.6 g/m^2, and fresh weight of belowground part was 578.8–612.4 g/m^2. It should be particularly noted that SD＋SCT＋P treatment（sand dunes that had both straw checkerboard technique and transplanted rhizomes of C. brunnescens） was the best and SD＋N（sand dunes that had no further treatment） was the worst in terms of following biotic indicators： total number of reproductive ramets, total number of belowground rhizomes, and fresh weight of aboveground and belowground parts of C. brunnescens, contents of soil organic carbon, available nitrogen, microbial biomass carbon, and microbial biomass nitrogen. It implies that applying SCT in sand dunes and transplanting belowground rhizomes to sand dunes with SCT could improve both soil fertility and growth of C. brunnescens. These results suggest that the SCT-promoted high reproductive abilities of belowground rhizomes of C. brunnescens can successfully facilitate the establishment of ramets and can thus be an effective strategy to restore degraded vegetation in Maqu alpine region of northwestern China.

广西岩溶区灌木林地凋落物——土壤碳、氮、磷化学计量特征

文章对广西7个典型岩溶石山区(隆林各族自治县、凌云县、东兰县、河池市金城江区、罗城仫佬族自治县、融水苗族自治县和桂林市雁山区)、63个灌木林地样方土壤及环境因子进行取样和调查,研究典型岩溶区土壤和凋落物有机碳(C)、全氮(N)和全磷(P)的化学计量特征及其影响因素。结果表明:(1)研究区灌木林地0~40 cm土壤C、N、P平均值分别为31.90 g·kg^(-1)、3.95 g·kg^(-1)和2.65 g·kg^(-1),变异系数分别为40.13%、41.46%、65.24%;C/N、C/P、N/P平均值分别为8.10、14.82、7.80,变异系数分别为14.88%、48.78%和41.33%;0~20 cm土壤C/N、C/P、N/P值略高于20~40 cm土壤;0~20 cm和20~40 cm土壤C/N、C/P和N/P组间均存在显著差异;(2)土壤养分元素含量之间均存在极显著相关性,土壤养分元素生态化学计量特征与凋落物N、P含量显著正相关,与凋落物C/N显著负相关;土壤P含量与海拔显著正相关,土壤C/N与年平均气温呈负相关关系;年平均降水量与土壤C、P呈中等负相关关系;年平均气温与土壤C、C/N、C/P呈负相关关系,与土壤N呈正相关关系。广西岩溶区土壤和凋落物均具有低碳高磷的特征,凋落物氮、磷是影响岩溶灌丛土壤养分化学计量特征的重要因子,年均温升高会促进土壤N增加,降低土壤C/N,年均降水量增加会降低土壤C、P含量。

2011-2020年海北高寒灌丛碳水热通量观测数据集

高寒灌丛是青藏高原的重要植被类型之一,多分布在山地阴坡、半阴坡或高海拔山前滩地,具有十分重要的碳素固持和水源涵养及气候调节功能。青海海北高寒草地生态系统国家野外科学观测研究站(简称海北站)自2002年应用涡度相关技术进行高寒金露梅(Potentilla fruticosa)灌丛生态系统碳水热交换,已有近20年的数据积累。在前期公开2003–2010年相关数据的基础上,进一步发布2011–2020年海北高寒灌丛碳水热通量观测数据集。本数据集包含空气温度、空气相对湿度、水汽压、风速、风向、大气压强、总辐射、净辐射、光合有效辐射、降水、土壤温度、土壤水分的常规气象数据子集和净生态系统CO_(2)交换、生态系统CO_(2)呼吸、总生态系统CO_(2)交换、潜热通量、显热通量的碳水热通量数据子集,均由半小时、日、月和年等4种时间尺度组成。本系列数据集不仅可以用于科学评估高寒灌丛生态系统碳水热等生态功能的环境驱动和演变趋势,还能对遥感-生态过程模型的参数验证及优化提供地面观测支撑。

增温对窄叶鲜卑花高寒灌丛生物量碳和氮分配的影响

文章以青藏高原东部窄叶鲜卑花灌丛为研究对象,采用开顶式生长室(OTCs)模拟增温实验(+1.2℃),分析增温对灌木层和草本层各器官碳、氮分配的影响及其影响因素,以揭示青藏高原东部高寒灌丛灌木层和草本层碳、氮分配对增温的响应策略。结果显示:(1)增温使窄叶鲜卑花灌木层叶、粗根、细根碳库显著增加18.8%、7.7%和139.4%,使灌木层细根氮库显著增加153.9%;增温使草本层地上和地下部分碳库显著增加60.4%和130.5%,使草本层地上和地下部分氮库显著增加46.1%和124.0%。(2)增温使灌木层茎和粗根碳分配比例显著降低18.9%和16.2%,使灌木层叶、茎和粗根氮分配比例显著降低25.2%、23.3%和14.4%,使灌木层细根碳、氮分配比例显著增加86.5%和96.2%;增温使草本层地上部分碳、氮分配比例显著降低19.5%和18.9%,使草本层地下部分碳、氮分配比例显著增加15.6%和24.8%。(3)Pearson相关分析和多元线性回归分析结果表明,空气温度和土壤微生物生物量是影响灌木层地上碳、氮分配的主要因子,能解释其变异的72.0%以上;土壤温度、土壤有机碳含量和土壤脲酶活性是影响灌木层地下碳、氮分配的主要因子,能解释其变异的92.0%以上;土壤有机碳含量、土壤转化酶和脲酶活性是影响草本层地上和地下碳、氮分配的主要因子,能解释其变异的92.8%以上。(4)土壤氮素有效性对灌木层和草本层生物量碳、氮分配的影响不显著。研究表明,气候变暖情景下,青藏高原东部窄叶鲜卑花高寒灌丛的灌木层和草本层植物通过提高地下部分碳、氮分配,进而更好地适应外界环境温度的提高。

东祁连山灌丛凋落叶水浸提液对垂穗披碱草种子萌发和幼苗生长的影响

为了解灌丛凋落叶在灌草群落结构维持中可能存在的潜在化感作用,以东祁连山3种优势灌木和灌下优势草种垂穗披碱草(Elymus nutans)为供试材料,分析了不同浓度(0.01 g/L、0.025 g/L、0.05 g/L、0.075 g/L、0.1 g/L)的金露梅(Potentilla fruticosa)、川滇柳(Salix rehderiana)、头花杜鹃(Rhododendron capitatum)及灌间草本的凋落叶水浸提液,对垂穗披碱草种子萌发、幼苗形态和生理指标的影响。结果表明:(1)垂穗披碱草种子发芽率与发芽势在金露梅与川滇柳凋落叶浸提液处理下呈“低促高抑”的浓度效应,在灌间草本凋落叶浸提液处理时表现为先升后降,而头花杜鹃凋落叶浸提液处理时均下降,并在浓度超过0.075 g/L时种子不发芽。(2)灌丛凋落叶浸提液对垂穗披碱草幼苗根长与干重均表现出抑制作用,且随浓度增大而增强;金露梅、川滇柳与灌间草本凋落叶浸提液对垂穗披碱草幼苗苗高表现出“低促高抑”的浓度效应;而头花杜鹃凋落叶浸提液处理对垂穗披碱草幼苗鲜重与苗高均呈抑制作用。(3)垂穗披碱草幼苗CAT、SOD活性随着浸提液浓度升高均表现出先升后降的变化趋势;可溶性糖与可溶性蛋白在灌丛凋落叶浸提液浓度低于0.075 g/L时含量较高;MOD含量在金露梅凋落叶浸提液处理下随浓度升高而持续升高,而在川滇柳与灌间草本凋落叶浸提液处理下呈先升高后降低的趋势。综合来看,灌丛凋落叶浸提液对垂穗披碱草的化感作用由大到小依次为:头花杜鹃、川滇柳、灌间草本、金露梅,其中头花杜鹃对灌下草本植物影响较大,凋落叶化感作用是影响该地区灌草系统群落分布及灌草结构的重要因素。

Changes in snow parameterization over typical vegetation in the Northern Hemisphere

季节性降雪对气候变化很敏感,常被当作气候变化的信号.由于其局地特征差异显著,不同下垫面类型的积雪过程也不尽相同.北半球中高纬度的典型下垫面(开阔灌丛,常绿针叶林和混交林)在积雪覆盖率和雪深之间有着独特的关系曲线,这种关系不仅代表了积雪过程和融雪过程的特征变化,更能用于模式进行积雪预测.研究发现,北半球中高纬度的增温改变了积雪参数化关系,进一步影响了局地能量和水循环,造成开阔灌丛的北缩和常绿针叶林及混交林的扩张.然而,目前模式中的积雪参数化并不能很好地再现全球变暖影响下融雪阶段出现的加速融化过程,并且进一步影响对春季融雪的生态影响的理解.

中国主要灌丛植被碳储量

在广泛收集资料的基础上,利用植被平均碳密度方法,估算了我国6种主要灌丛植被的碳储量,并分析了其区域分布特征。主要结果如下:1)6种灌丛植被总面积为15462.64×104hm2,总碳储量为1.68±0.12PgC(1Pg=1015g),灌丛植被平均碳密度为10.88±0.77MgC·hm-2(1Mg=106g),不同植被类型差异较大,在5.92～17MgC·hm-2之间波动。2)从区域分布来看,西南3省(云南、贵州、四川)既是我国灌丛主要的分布地区之一,分布面积占6种灌丛总面积的23.5%,又是我国灌丛碳储量的主要储库,碳储量占整个6种灌丛碳储量的1/3(32.6%),适宜的水热条件决定了该地区的植被平均碳密度要高于全国平均水平。3)与我国森林和草地的植被碳储量相比,这些灌丛碳储量相当于我国森林和草地碳储量的27%～40%和36%～55%。

不同放牧强度对三峡地区灌丛草地植物产量的影响

研究了不同放牧强度下长江三峡地区灌丛草地植物产量的动态变化。结果表明 ,灌丛草地上的优势草本植物种是芒 ,重牧区灌丛草地中芒的地上生物量均显著 (P<0 .0 5 )小于对照和轻牧区。对照、轻牧和重牧 3种处理下 ,芒的平均地上生物量 (干物质 )分别为 (74 9.1± 80 8.7) kg/ hm2 、(6 98.6± 6 78.8) kg/ hm2 和 (2 2 2 .5± 10 0 .5 ) kg/ hm2 。在对照、轻牧和重牧处理下 ,灌丛草地禾草、灌木和杂类草的产量组成依次分别为 :3.7∶ 1.5∶ 1、5 .3∶ 1.6∶ 1、1.5∶ 1.2∶ 1,灌丛草地上禾草的产量动态变化趋势与总产草量的变化基本一致。9月份灌丛草地的产草量最高 ,对照、轻牧和重牧 3个处理的总产草量分别为 30 4 2 .8kg/ hm2 、2 5 18.4 kg/ hm2 和 1180 .3kg/ hm2 。

荒漠草原人工柠条林草本层植被的结构与动态

为系统认识柠条林草本层植被的物种组成特征及其动态变化规律,把握灌草结构及人工林系统的演变趋势,采用空间换时间的方法,以天然草地为对照,搭建一个由不同林龄样地构成的研究序列,并开展灌丛内外植被季节性动态的跟踪监测与分析。结果表明:1)对照草地和柠条林地草本层物种共计25种,分属于8个科23个属。16a柠条林物种数最多(16种),随着林龄的增大,物种数逐渐减少,中亚白草和隐子草等多年生禾草开始出现,但是优势种以一年生短命植物为主。物种多样性指数则随林龄增长呈先增长后下降的趋势。2)草本层植被盖度、生物量与物种数的季节动态主要受降水、气温变化的影响,但是灌丛的存在显著延滞了草本层植被经历春季干旱后的生长恢复速度,并以25a柠条林的生长节律变化最为突出。3)林龄显著改变了灌丛内外草本层植被盖度以及灌丛内草本层植被生物量的季节动态,林龄与季节因子间存在显著的交互作用。综上所述,荒漠草原人工柠条林草本层植被的结构与动态是林龄、季节以及空间异质性等因子交互作用下的产物,伴随人工柠条林的衰败,群落存在逐步向地带性植被演替的趋势,但是在以一年生短命植物为主要优势物种情况下,系统稳定性的维持和演替方向还存在诸多的不确定性。

海南俄贤岭石灰岩山地海南大戟灌丛群落研究

根据样方调查,对海南俄贤岭自然保护区海南大戟灌丛群落的种类组成、外貌、结构特征和物种多样性进行分析。结果表明,在700m2样地中,有维管植物77种,隶属于47科70属。群落中乔木的个体数量很少,主要由灌木和草本组成,灌木层主要优势种为海南大戟等。群落外貌常绿,生活型以小高位芽为主,占22.08%;按照Raunkiaer的频度等级定律,属于B级的种类最多,频度值为43.42。整个群落的物种丰富度Magarlef指数为8.56,Shannon-Wiener指数为1.38,Simposon为0.90,均匀度指数为0.32。群落各层次的丰富度格局表现为灌木层>草本层>乔木层>藤本植物,多样性格局为灌木层>乔木层>草本层<(>)藤本植物,均匀度格局为乔木层>藤本植物>灌木层>草本层。