Land Cover Changes and Drivers in the Water Source Area of the Middle Route of the South-to-North Water Diversion Project in China from 2000 to 2015

The Middle Route of the South-to-North Water Diversion Project(MR-SNWDP)in China,with construction beginning in 2003,diverts water from Danjiangkou Reservoir to North China for residential,agriculture and industrial use.The water source area of the MR-SNWDP is the region that is most sensitive to and most affected by the construction of this water diversion project.In this study,we used Landsat Thematic Mapper(TM)and HJ-1 A/B images from 2000 to 2015 by an object-based approach with a hierarchical classification method for mapping land cover in the water source area.The changes in land cover were illuminated by transfer matrixes,single dynamic degree,slope zones and fractional vegetation cover(FVC).The results indicated that the area of cropland decreased by 31%and was replaced mainly by shrub over the past 15 years,whereas forest and settlements showed continuous increases of 29.2% and 77.7%,respectively.The changes in cropland were obvious in all slope zones and decreased most remarkably(–43.8%)in the slope zone above 25°.Compared to the FVC of forest and shrub,significant improvement was exhibited in the FVC of grassland,with a growth rate of 16.6%.We concluded that local policies,including economic development,water conservation and immigration resulting from the construction of the MR-SNWDP,were the main drivers of land cover changes;notably,they stimulated the substantial and rapid expansion of settlements,doubled the wetlands and drove the transformation from cropland to settlements in immigration areas.

Impacts of land cover change on plant and bird species diversity in Hainan Island,China

Hainan Island, located at the southern end of China, has less than 0.4% of land area but contains 13% of plant and animal species in China. During the last four decades many primary forests have been converted to shrub land, grassland, and tree planation (e.g., eucalyptus forest). As a result, area of primary tropical forest has been reduced from 25.8% in the 1950s to 4% in the 1990s. To assess impacts of land conversion on plant and bird species diversity, a series of samples in primary forest and four types of converted lands were took. The land conversion had tremendously reduced both plant and bird species diversity. Specifically, plant species richness per site was 83.7 in primary forest, 28.3 in shrub land, 12.5 in grassland, 14.4 in eucalyptus forest, and 21.4 in Acacia forest. Bird species richness showed a similar trend: 22.0 in primary forest, 14.5 in shrub land, 2.5 in grassland, 4.9 in eucalyptus forest, and 9.0 in Acacia forest. The Shannon species diversity indices for plants in the five types of land cover were 3.69, 1.99, 0.97, 1.47 and 2.07, respectively. Similarly, the Shannon indices for bird species diversity were the highest in primary forest, and lowest in grassland, and intermediate in shrub land and eucalyptus forest.

Effects of Winter Cover Crop and Straw Returning on the Functional Diversity of Rhizosphere Microflora in Double-crop Rice Paddies

The functional diversity of rhizosphere microflora which is also known as the “microbial community” is a sensitive indicator of soil quality subject to the type of winter cover crop and straw returning.In order to evaluate the effects of different winter cover crops and returning patterns on the functional diversity of rhizosphere microflora in double-crop rice paddies,we designed five winter cover crops and straw returning combinations to analyze their effects on the functional diversity of rhizosphere microflora in rice paddies: ryegrass (Lolium multiflorumL.)–double-crop rice (Ry),milk vetch (Astragalus sinicus L.)–double-crop rice (Mv),Rape (Brassica napus L.)–Double-crop rice (Ra), Potato (Solanum tuberosum L.)–double-crop rice (Po),and winter fallow–doublecrop rice (CK,the control).In this paper,the average well color development (AWCD) in Biolog-GN plates indicated the capacity for carbon utilization by the rhizosphere microbial community.We analyzed the rhizosphere microbial community functional diversity of the paddy soils with the above five treatments by using the Biolog-GN system.The results showed that applications of winter cover crop and straw returning caused high increases in AWCD compared with CK,and the AWCD values for samples with Po treatment was greater than those with Ry and CK treatments at the early and late rice maturity stages. It was concluded that applications of winter cover crop and straw returning can cause changes in the carbon utilization efficiency of rhizosphere microflora.There were differences in the genetic diversity of the rhizosphere microflora among different treatments at the maturity stage of early and late rice.The richness,Shannon,and McIntosh Index under different winter cover crop and straw returning treatments were significantly different.The highest indexes were observed in the Po treatment and the lowest in the CK at the maturity stage of early and late rice.The richness, Shannon,and McIntosh Index under different treatments ranked in descending order is as follows: Po>Ra>Mv>Ry>CK.Principal Component Analysis (PCA) of substrate reactions were conducted in this research.The results indicated that the pattern of carbon source utilization varied with winter cover crop treatments,and that carbohydrates and amino acids were the main carbon sources of rhizosphere microorganisms.To conclude,the application of winter cover crop and straw returning to paddy fields could significantly increase the carbon source utilization, species richness,and species evenness of rhizosphere microflora in double-crop rice paddies.

Floristic Diversity, Distribution and Analysis of Forest Cover Change in the Kedjom Keku Forest, NW Cameroon

Conservation of tropical rainforest is an important aspect of climate change mitigation, and baseline information through inventories of forests is paramount so as to enable the putting in place of proper management strategies. This study was aimed at evaluating the plant species diversity, and distribution and to investigate the forest cover change of the Kedjom Keku forest. Five plots were located at irregular intervals (100 m × 50 m) along a line transect and spread throughout the study area using 10 m × 10 m. Land cover/Land use changes were evaluated using remote sensing and GIS, while semi structured questionnaires were used to assess the anthropogenic activities. A total of 107 species of plants including 74 trees, 28 shrubs and 5 lianas, belonging to 83 genera and 58 families were identified. Rubiaceae (10 species) and Asteraceae (5 species) were the most represented tree and shrub families respectively. Species with the highest important value index were Schefflera mannii (31.9) and Piper capense (16.9) for trees and shrubs respectively. This forest is diverse, with Shannon-Wiener diversity index values of 3.55 for trees and 3.07 for shrubs. Seven land cover classes were distinguished within the years 1986, 2003 and 2018. There was a drastic increase in built up/settlement from 0.63% in 2003, to 20.46% in 2018. Dense vegetation increased within 2003 to 2018 after a drastic drop from 151.86 ha−1 to 119.88 ha−1 between 1986 and 2003. Infrastructure, over-grazing and expansion of farmland were reported as the direct factors influencing degradation, while land right, land tenure and equitability were the most cited indirect factors. The prominent factor that encouraged degradation was the fertile nature of the soils. We propose that sensitization campaigns be carried out to educate inhabitants on the rich biodiversity of Kedjom Keku forest and explain to them the importance of sustainable management of the resources therein.

Diversity-accuracy assessment of multiple classifier systems for the land cover classification of the Khumbu region in the Himalayas

Land cover classification of mountainous environments continues to be a challenging remote sensing problem,owing to landscape complexities exhibited by the region.This study explored a multiple classifier system(MCS)approach to the classification of mountain land cover for the Khumbu region in the Himalayas using Sentinel-2 images and a cloud-based model framework.The relationship between classification accuracy and MCS diversity was investigated,and the effects of different diversification and combination methods on MCS classification performance were comparatively assessed for this environment.We present ten MCS models that implement a homogeneous ensemble approach,using the high performing Random Forest(RF)algorithm as the selected classifier.The base classifiers of each MCS model were developed using different combinations of three diversity techniques:(1)distinct training sets,(2)Mean Decrease Accuracy feature selection,and(3)‘One-vs-All’problem reduction.The base classifier predictions of each RFMCS model were combined using:(1)majority vote,(2)weighted argmax,and(3)a meta RF classifier.All MCS models reported higher classification accuracies than the benchmark classifier(overall accuracy with 95% confidence interval:87.33%±0.97%),with the highest performing model reporting an overall accuracy(±95% confidence interval)of 90.95%±0.84%.Our key findings include:(1)MCS is effective in mountainous environments prone to noise from landscape complexities,(2)problem reduction is indicated as a stronger method over feature selection in improving the diversity of the MCS,(3)although the MCS diversity and accuracy have a positive correlation,our results suggest this is a weak relationship for mountainous classifications,and(4)the selected diversity methods improve the discriminability of MCS against vegetation and forest classes in mountainous land cover classifications and exhibit a cumulative effect on MCS diversity for this context.

590份燕麦种质资源营养器官表型性状遗传多样性分析

为明确燕麦(Avena sativa)种质资源营养器官表型性状的遗传多样性和各性状之间的相关关系,进而为燕麦育种和种质资源创新利用提供理论依据,本研究以国内外收集的590份燕麦种质资源为研究对象,在青海省西宁市湟中区对其从地上器官质量性状、茎部性状、叶部性状和分蘖性状的遗传多样性进行评价分析,并利用相关性分析和聚类分析方法,评价其营养器官表型性状的遗传变异水平。结果表明:590份燕麦种质资源质量性状遗传多样性指数以茎节绒毛最高(1.026),苗期株型最低(0.162);数量性状的遗传多样性指数以第三茎节茎粗最高(2.09),旗叶叶面积最低(1.87);变异系数以无效分蘖数(54.92%)最大,茎节数最小(12.20%);茎部性状和倒二叶长、倒二叶叶面积是影响燕麦种子和饲草产量的重要因子。590份燕麦资源可分为4大类群,其中类群Ⅲ可作为饲草型育种目标的亲本材料,类群IV可作为抗倒伏育种材料。

植物覆盖对香蕉园土壤真菌多样性及群落结构的影响

高度集约化的农业措施致使蕉园土壤退化日趋严重,制约了中国香蕉产业的健康可持续发展。植物覆盖能够改善土壤理化性质,优化土壤微生物群落结构,是一种重要的改善农业生态系统土壤退化的耕作措施。本研究通过宽窄行种植方式,以传统的裸露土壤种植方式为对照,在宽行中人工种植大翼豆[Macroptilium atropurpureum(DC.)Urb.]和自然生杂草为植物覆盖处理,通过连续定位试验,采集土壤样品并进行高通量测序,分析蕉园在植物覆盖下的土壤真菌多样性及群落结构的差异特征,以期探索蕉园土壤可持续利用种植模式。结果表明:蕉园植物覆盖处理下真菌群落组成差异显著,并随着覆盖年限增加呈现加强的趋势。根据FUNguild功能预测,与对照相比,大翼豆覆盖处理2019年和2020年Saprotroph_Symbiotroph真菌种群显著地(P≤0.05)增加,2020年Pathogen_Saprotroph真菌种落显著(P≤0.05)降低。共线性网络分析结果表明大翼豆覆盖处理与对照相比,群落复杂性无差异,但群落稳定性更高。同时核心物种无镰刀菌属ASVs,这可能反映了大翼豆覆盖可以减少镰刀属ASVs在群落中主导力,降低土传病害香蕉枯萎病的潜在发生风险。大翼豆处理有效提高了共生有益真菌群,减少了潜在的致病真菌群,有利于保持香蕉种植中的土壤健康。宽窄行与行间覆盖植物相结合的种植技术可有效改善土壤微生物多样性,有利于香蕉产业的可持续发展。

不同带间距固沙林带间植被与土壤特性变化

在科尔沁沙地敖汉旗沙区,通过评估不同带间距低覆盖度固沙林对土壤及植被的影响,旨在提出更适宜当地条件的带间植被恢复与土壤发育的配置结构模式,为科尔沁沙地人工造林提供科学依据。对3种不同带间距的赤峰杨固沙林带间植被群落多样性、土壤理化性质及其相关性进行了研究。结果表明:不同带间距赤峰杨固沙林带间植被与土壤恢复有明显影响,植被恢复与土壤恢复是相辅相成的。(1)在调查的3种不同带间距的行带式固沙林中,随着带间距的增加,带间植被的物种多样性呈增加趋势,各物种多样性指数的变化趋势比较为:带间距25 m>16 m>10 m>等株距对照样地;(2)土壤含水量、孔隙度及土壤养分(有机碳、碱解氮、速效磷、速效钾)含量比较为:带间距25m>16m>10m>等株距对照样地;土壤容重比较为:带间距25 m<16 m<10 m<等株距对照样地;(3)在不同带间距赤峰杨固沙林中,土壤发育和植被恢复是相互促进的,物种多样性指数与土壤的各项理化性质存在不同程度的显著(P<0.05)或极显著(P<0.01)相关,但与速效钾的相关性不显著。低覆盖度赤峰杨固沙林带间距的大小对带间土壤理化性质、植被恢复有明显的影响,增大带间距,能有效促进土壤发育、促进带间植被生长,25m的带间距,更有利于土壤的发育和带间草本植被生长。

河床冲洪积覆盖层箱涵与引水隧洞明暗结合部开挖与支护方法

引水工程在遇两侧山体中间夹河道的情况下,通常采用河床区箱涵与山体内隧洞连接的形式通过。河道的河床区往往存在较深且透水性强的冲洪积覆盖层,当箱涵与引水隧洞明暗结合部布置在覆盖层中时,为保证施工安全及质量,必须采取有效的开挖与支护方法,其中箱涵基坑降排水、箱涵分层开挖与支护、结合部预加固、隧洞超前支护与洞身开挖等重要程序必须制定完善的施工方法,并严格执行。通过隧洞围岩变形监测,该工程开挖与支护方法合理有效。

Spatial pattern of landscape changes and consequence changes in species diversity between 1956-1999 of Pinus halepensis Miller plantations in Montes de Malaga State Park (Andalusia, Spain)

Changes in forest diversity and the transforma- tion of coniferous plantations into more natural woodlands are of special interest in the Medi- terranean. The aim of this study was to investi- gate changes in land use patterns and vegeta- tion cover from 1956 to 1999 in Pinus halepensis Miller plantations in Montes de Málaga State Park in southern Spain. At the landscape level, a FRAGSTAT analysis was performed using aerial photographs. At the community level, a total of 47 sample plots were analyzed. Field measure- ments indicated the presence of a total of 70 species in the different vegetation types sam- pled. Shannon-Wiener (H), and Simpson’s (D) diversity indices showed the greatest species richness in Aleppo pine plantations (H = 1.54 ± 0.2;D = 3.88 ± 0.6), while Holm oak stands in the forested areas (H = 1.37 ± 0.1;D = 3.35 ± 0.6) and agricultural land (H = 1.33 ± 0.01;D = 2.80 ± 0.03) had lower values. FRAGSTATS analyses at land- scape and community levels indicated increases in patch richness, patch number, and percent of landscape mainly for pine plantations, Holm oak forests and shrub habitats. Replacement of agri- culture by conifer plantations led to the homo- genization of landscape structure. This change has modified the landscape by facilitating the recovery of indigenous tree species including Holm oak, which will likely lead to the future establishment of native forests in this area. Our findings suggest that pine plantations could fa- vour woody species diversity by increasing abundance and species richness in contrast to the situation in non-forested agricultural land.

Immediate and legacy effects of snow exclusion on soil fungal diversity and community composition

Background:Soil fungi play crucial roles in ecosystem functions.However,how snow cover change associated with winter warming affects soil fungal communities remains unclear in the Tibetan forest.Methods:We conducted a snow manipulation experiment to explore immediate and legacy effects of snow exclusion on soil fungal community diversity and composition in a spruce forest on the eastern Tibetan Plateau.Soil fungal communities were performed by the high throughput sequencing of gene-fragments.Results:Ascomycota and Basidiomycota were the two dominant fungal phyla and Archaeorhizomyces,Aspergillus and Amanita were the three most common genera across seasons and snow manipulations.Snow exclusion did not affect the diversity and structure of soil fungal community in both snow-covered and snow-free seasons.However,the relative abundance of some fungal communities was different among seasons.Soil fungal groups were correlated with environmental factors(i.e.,temperature and moisture)and soil biochemical variables(i.e.,ammonium and enzyme).Conclusions:These results suggest that the season-driven variations had stronger impacts on soil fungal community than short-term snow cover change.Such findings may have important implications for soil microbial processes in Tibetan forests experiencing significant decreases in snowfall.

Stand development patterns of forest cover types in the natural forests of northern Baekdudaegan in South Korea

The purpose of this study was to classify current forest cover types,and to investigate stand development patterns for natural forests in six areas in northern Baekdudaegan,South Korea.Twenty-eight independent forest communities were aggregated into eight forest cover types by species composition in the overstory of each forest community.The forest cover types were of mixed mesophytic,‘‘others’ ’ deciduous,Quercus mongolica dominant,Q.mongolica pure,Pinus densiflora–Q.mongolica,P.densiflora,Betula ermanii,and Q.mongolica–P.koraiensis.The ecological information was organized by importance value and species diversity for each forest type.Based on the correlation between species diversity index and the abundance of Q.mongolica plus P.densiflora for corresponding forest cover types,we compared the developmental process and approximate successional pathway between each cover type.The P.densiflora forest cover type changes into the P.densiflora–Q.mongolica cover type,followed by the Q.mongolica dominant cover type through continuous invasion of the oak trees.Furthermore,the Q.mongolica pure cover type would spread toward the Q.mongolica dominant cover type with a mixture of various deciduous tree species.The Q.mongolica dominant cover type progresses through the other deciduous cover types to the mixed mesophytic cover type with diversified composition and structure.On the mid to lower slopes,with loamy soils and good moisture conditions,various deciduous forest types should progress,by ecological succession,toward the mixed mesophytic cover type without any further disturbance.

Soils Typology and Floristic Diversity of the Forest of the“Cite Scientifique”of Brazzaville,Congo

A study of the typology of soils and floristic diversity was carried out in the forest of the “Cité Scientifique” of Brazzaville. The study aimed to assess the influence of soil cover on the distribution of taxa. The study covers 18 plots of 625 m2 each, distributed in different soil profiles. The floristic inventory concerns the measurement of diameter of trees with dbh ≥ 10 cm and the counting of herbaceous and shrubs of dbh < 10 cm. The floristic composition reveals a total of 129 plant species distributed in 48 families dominated by Fabaceae and a preponderance of pioneer taxa. The Jaccard coefficients of similarity reveal a low degree of homology of woody plots, whereas for the flora as a whole, the floristic composition is heterogeneous. The Shannon biological diversity index of ligneous varies from 0.6 to 2, against a maximum diversity of 0.69 to 3. The Pielou index of ligneous (0.5 to 0.9) does not reveal any dominance. Soil cover consists of ferrallitic and podzol soils. Their texture is sandy, weakly structured, fragmentary polyhedral throughout the profile, but lumpy and/or nuciform at the surface and sub angular in depth. The porosity decreases proportionally with the depth and thickness of the horizons. The floristic analysis presents an ecosystem with a low degree of diversification for a high floristic richness. The preponderance of anthropization markers is a proof of its very advanced state of disturbance. The study shows that soil cover does not influence the distribution of timber. Indeed, the establishment and development of pioneer species are less prone to soil properties.

Floristic diversity and carbon stocks in the periphery of Deng–Deng National Park,Eastern Cameroon

Carbon is continuously being removed from the atmosphere by photosynthesis and stored in carbon pools(live,dead,and soil carbon)of forest ecosystems.However,carbon stock in dead wood and of trees with diameters at breast height(dbh)between 5 and 10 cm is often not considered in many studies carried out in the Congo Basin Forest.The relationship between tree diversity,life-forms and carbon stocks has received little attention.This study was carried out on the outskirts of Deng Deng National Park(DDNP)to determine tree diversity(dominant families,species richness and Shannon index),assess carbon stocks in the five carbon compartments(living tree,understory,fine roots,dead wood and litter)as well as to analyze the relationship between(1)carbon stocks and tree diversity;and,(2)between carbon stock and life-forms.The Shannon index of trees≥10 cm dbh ranged from 2.6 in riparian forest to 4.3 in secondary forest;and for the tree between 5 and 10 cm,it ranged to 1.56 in riparian forest to 3.68 in the secondary forest.The study site housed 16 species,7 genera and 3 families which are only found in trees of dbh between 5 and 10 cm.The average total carbon stock of the five compartments varied from 200.1 t ha-1 in forest residues to 439.1 t ha-1 in secondary forest.Dead wood carbon stock varied from 1.2 t ha-1 in riparian forests to 12.51t ha-1 in agroforests.The above ground carbon stocks for trees with diameter between 5 and 10 cm varied from 0.7 t ha-1 in young fallow fields to 5.02 t ha-1 in old secondary forests.This study reveals a low but positive correlation between species richness and total carbon stocks,as well as a significant positive relationship between life-forms and total carbon stocks.The findings highlight the need for more data concerning carbon content of dead wood,carbon of trees≥5 cm<10 cm dbh and the relationship between carbon stocks and tree diversity from other areas of the Congo Basin for a good understanding of the contribution of tropical forests to climate change mitigation.

The Fate of Taita Hills Forest Fragments: Evaluation of Forest Cover Change between 1973 and 2016 Using Landsat Imagery

Landsat images were used to evaluate changes in forest cover of five forest fragments (Chawia, Fururu, Mbololo, Ngangao and Vuria) between 1973 and 2016. The forest fragments are part of the Eastern Arc Mountains, a global biodiversity hotspot that boasts outstanding diversity of flora and fauna and a high level of endemism. Landsat imageries of 1973, 1987, 2001, 2012 and 2016 were analyzed using ArcGIS version 10.0 to provide information on forest cover change of the fragments between 1973 and 2016. Results showed that the annual rate of deforestation was 0.5% and was similar to global estimates. The forest fragments lost 23.2% of forest cover between 1973 and 2016. The forest area lost was higher in Vuria (43.0%) and Chawia (32.7%) which are non-gazetted forests managed by the County government of Taita Taveta but lower in Fururu (3.2%), Mbololo (13.7%) and Ngangao (16.8%) which are gazetted forests managed by Kenya Forest Service. Fururu and Mbololo forest fragments gazetted in early 1990s suffered less loss in forest cover compared to Ngangao, which was gazetted 12 years later. Gazettement of forests could preclude further forest degradation and loss by improving their management for effective provision of ecosystem services and conservation of biodiversity.

南水北调中线工程2014—2022年冬季水温与冰盖观测分析

南水北调中线工程自2014年12月全线通水以来已运行8个冬季,为防止冰塞冬季输水流量控制为设计流量的30%~50%,严重制约了工程输水效益的发挥。因此,渠道水温和冰盖特性一直是冬季输水关注的重点问题之一。实测数据表明:①冬季输水流量总体逐年增大,最末段保持相对稳定,岗头闸流量约为50 m^(3)s,北拒马河闸约为25 m^(3)s;②冬季气温总体以暖冬居多。保定站最低气温-22.0℃,3日滑动气温极值-10.7℃,短期强寒潮可能是今后冰盖生成的关键驱动因子;③冬季水温沿程逐渐降低,渠首陶岔闸最低水温6.7℃,渠末北拒马河闸多数年份降至0℃附近。北拒马河闸水温最大降幅10日内由3.5℃降至0℃,期间渠段水温降幅亦达到极大值1.69℃100 km。④2016年冬季冰盖最长达280 km(最南端延伸至午河闸),次之为2015年冬季的73 km和2021年冬季的38 km,有两个冬季未生成冰盖。岗头闸-北拒马河闸近90 km是冰盖多发渠段,应引起关注。基于冰盖生成前实测数据,以初始水温和区间气温为输水条件,拟合给出了2 d、3 d和7 d等不同预报时效的简化水温模型和冰盖生成临界阈值。初步分析认为:冬季气温和输水流量是冰盖生成的两大关键驱动因子,流量越小气温越低越易生成冰盖,1月出现的短期强寒潮更易于导致冰盖生成。2016年冬季严重冰情是二者叠加的结果,2015年冬季冰盖主要是输水流量小诱发,而2021年冬季冰盖主要是短期强寒潮所致。

沾益区林木树冠覆盖与植物多样性

选用清晰的全色历史数据影像为基础,通过Ecognition9.0软件解译,计算其树冠覆盖率及不同土地类型比例,根据分层随机抽样和实地调查方法,选取111个样方。结果表明:沾益区(建成区)林木树冠覆盖面积4.33 km 2,林木树冠覆盖率28.68%,其中公园绿地林木树冠覆盖率占比较大,其植物多样性、植物丰富度等均高于其他绿地。应用频度最多的乔木树种为香樟(Cinnamomum camphora)等;灌木树种为海桐(Pittosporum tobira)等,树种应用以乡土树种为主。不同绿地类型之间树冠覆盖率存在差异,树冠覆盖率与Simpson指数、Shannon-Wiener指数、Pielou指数、平均株高之间存在不显著正相关关系,与Margalef丰富度指数、平均胸径存在不显著负相关关系。沾益区已形成相对稳定的现实林木树冠斑块,潜在林木树冠覆盖有较大增长空间。

青藏高原东北边缘地区高寒草甸群落特征对封育的响应

封育是退牧还草恢复退化草地的主要措施,而封育的时效限制着该措施的实施年限。本研究连续6年监测了青藏高原东北边缘天祝县高寒草甸群落特征对封育的响应。结果表明,高寒草甸群落盖度、高度、物种多样性及生物量均随着封育年限增加表现为先显著降低,后显著升高,再显著降低(P<0.05),第4年时群落高度和盖度最高,物种多样性和生物量最大,说明高寒草甸适宜封育时间是4年。

辽河流域环境要素对水生态的影响

为了分析流域内气候、地形地貌和人类活动对水生态的影响,分别于2009年8月和2010年6月对辽河流域76个采样点的鱼类和底栖动物进行了调查采样。运用统计学的相关分析和典型相关分析,从流域尺度分别建立了气候、地形地貌、土地利用类型与鱼类和底栖动物生物多样性的关联。结果表明,鱼类多样性与年均日照时数、草地用地比例、耕地用地比例、城市用地呈显著负相关,与多年平均降水量、相对湿度和水域的用地比例呈显著正相关;底栖多样性与年均日照时数、林地、草地、耕地用地比例呈显著负相关,与坡度、NDVI、多年平均降水量、相对湿度和水域的用地比例呈显著正相关。典型相关分析表明对水生生生物影响最大的环境要素是多年平均温度、坡度和水域用地。

冬季覆盖作物秸秆还田对双季稻田根际土壤微生物群落功能多样性的影响

微生物群落功能多样性是土壤质量变化重要的指标,不同作物类型的秸秆还田措施对土壤微生物群落功能多样性具有明显的影响。以位于双季稻主产区不同冬季覆盖作物-双季稻种植模式大田定位试验田为研究对象,以冬闲-双季稻种植模式为对照(CK),应用Biolog-GN技术开展黑麦草-双季稻(Ry)、紫云英-双季稻(Mv)、油菜-双季稻(Ra)和马铃薯-双季稻(Po)种植模式条件下不同冬季覆盖作物秸秆还田后对双季稻田根际土壤微生物功能多样性影响的研究。研究结果表明,早稻和晚稻成熟期,与CK处理相比,冬季覆盖作物秸秆还田处理增加了稻田土壤碳源平均颜色变化率(AWCD),以Po处理AWCD均为最高,均显著高于Ry和CK处理。不同冬季覆盖作物秸秆还田处理土壤微生物代谢多样性指数表现出明显的差异,早稻成熟期,Po处理的Richness、Shannon和McIntosh指数均为最高,其次为Ry、Mv和Ra处理,CK处理最低;晚稻成熟期,各处理的Richness、Shannon和McIntosh指数大小顺序均表现为Po>Ra>Mv>Ry>CK。土壤微生物碳源利用的主成分分析结果表明,各冬季覆盖作物秸秆还田处理根际土壤微生物利用的主要碳源为氨基酸类和糖类物质,不同处理间碳源利用类型有差异。冬季覆盖作物秸秆还田措施有利于提高双季稻田根际土壤微生物对碳源的利用能力、物种丰富度和均匀度。