基于CA-Markov模型的锡林河流域土地利用变化及预测分析

研究土地利用变化特征及预测未来土地利用变化的趋势，对经济平衡发展、提高生态环境质量、实现土地资源合理利用具有重要意义。以锡林河流域为研究区，对Landsat 2000、2005、2010年和2015年4期遥感数据进行目视解译，采用土地利用结构分析方法、重心迁移模型和CA-Markov模型，分析研究区16 a间土地利用演变特征，并对2030年土地利用情况进行预测。结果表明:1)2000-2015年，草地、林地和耕地呈波动变化，水域面积缓慢增加，建设用地不断扩张，未利用地面积在不断减少。建设用地、耕地和未利用地重心具有明显的方向性移动，耕地先向南后向北移动，建设用地主要向西北方向扩张，未利用土地重心持续向北移动。2)研究区综合土地利用动态度为5.70％，变化速率较快；锡林浩特市和各苏木土地利用变化速率差异较大，总体表现为中游＞下游＞上游；不同土地利用类型动态度为建设用地＞水域＞林地＞耕地＞未利用土地＞草地，即建设用地变化最快。3)研究区土地利用变化的主要方向为草地和未利用地的相互转换、耕地和草地的互相转换以及建设用地的不断扩张。4)2030年预测结果表明，耕地面积继续增加，速率有所下降，重心向西南方向移动；林地延续之前变化趋势，稳中有升；草地和未利用地面积继续减少，且未利用地重心持续向北移动；建设用地扩张明显，重心向锡林浩特市中心移动，速度减缓；水域有少量增加。CA-Markov模型与土地利用重心迁移模型相结合，实现了对未来耕地、建设用地和未利用土地的迁移方向的预测，可以为研究区提高草地退化防治效果、土地管理政策的制定和实施、城乡建设、土地利用规划等提供理论指导。     

生物炭对黑土区坡耕地土地生产力的可持续效应研究

为探究一次性施加生物炭后对黑土区坡耕地生产力的可持续效应,以东北黑土区3°坡耕地径流小区为研究对象,设置CK(不施用生物炭)和BC(2016年施用75 t/hm~2生物炭,2017、2018年不再施用生物炭)两个处理,于2016—2018年开展了试验研究。结果表明:一次性施入生物炭3年内,土壤容重显著降低(P0.05),第1年降低最明显,为3.87%,孔隙度和总有机碳、铵态N、有效P、速效K含量显著提高(P0.05),p H值则是施炭后前两年显著提高(P_(2016)=0.034、P_(2017)=0.038),分别提高了0.9、0.6,第3年与未施炭处理无显著差异(P_(2018)=0.067);施用生物炭显著提升了土壤的持水能力和保水保土性能,土壤饱和含水率、田间持水率、凋萎系数均显著提高(P0.05),最大增长率分别为5.58%、4.78%、7.29%,年径流深和土壤侵蚀量显著降低(P0.05),年径流深最大减少量为4.92 mm,土壤侵蚀量最大减小率为5.71%;大豆产量和水分利用效率显著提高(P0.05),最大增长率分别为29.01%、16.92%。但生物炭对土地生产力的持续效应逐年减弱,随着生物炭施用年限的延长,BC处理土壤容重线性递增,p H值和总有机碳含量呈幂函数递减,孔隙度和铵态N、有效P、速效K含量线性递减,饱和含水率、田间持水率、凋萎系数线性递减,年径流深和土壤侵蚀量线性递增,大豆产量和水分利用效率分别呈幂函数递减和线性递减。采用改进的TOPSIS(Technique for order preference by similarity to an ideal solution)模型和GM(1,1)模型测算并预测土地生产力指数,结果显示,BC处理的土地生产力指数均高于CK处理,但其值逐年下降,预计到2021年与CK处理十分接近,表明一次性施用75 t/hm~2生物炭对土地生产力的影响可持续5～6年。研究结果可为东北黑土区生物炭应用提供理论依据。     

基于宗地尺度的土地集约利用潜力评价及存量用地挖潜研究——以重庆市渝北区为例

为探究渝北区未来存量用地的挖潜方向,通过构建商服圈,并利用建筑、人口经济、交通和公共服务设施数据,从功能、强度和区位潜力3方面选取评价指标,结合层次分析法和熵权法确定其权重,计算渝北区城镇建设用地集约利用潜力,并依此识别可用于二次开发的宗地.结果表明:①渝北区划定商服圈总面积15 827.25 hm~2,因受地形、政策和城市双核心发展因素影响商服圈呈不规则形状;②用于潜力评价的宗地因城市开发过程中各类用地并存且未实现更新而未呈现同心圆模式;③渝北区可用于二次开发的城镇建设用地总面积为1 178.88 hm~2,主要布局于两路老城区南部、龙山—龙溪—龙塔街道西北部和创新经济走廊中部等区域.④渝北区公共管理与公共服务用地和商业服务业设施用地土地集约利用潜力较大,是未来改造盘活的主要用地类型.     

活化风蚀坑沙障固沙技术及植被恢复

风蚀坑活化形成的流动沙地直接危害草场,使土地逐渐丧失生产力。结合风蚀坑内风速变化特征,采取风蚀坑及边坡、风蚀坑积沙区沙障固沙技术,恢复风蚀坑植被。结果表明:风蚀坑及边坡设置黄柳沙障3 a,植被覆盖率达到27.0%,植物种为7种;PE纱网沙障植被覆盖率为31.0%,植物种为11种;PLA沙障植被覆盖率达到15.6%,植物种为4种;黄柳+PE复合沙障植被覆盖率达到75.3%,植物种为6种,而对照植被覆盖率为1.6%,植物种2种。在风蚀坑积沙区,设置沙障3 a后,PE纱网沙障植物种达到10种,黄柳+PE沙障为8种,PLA沙障为4种,黄柳沙障6种,而对照为1种;植被覆盖率分别达到50.3%、50.7%、22.7%、40.0%,而对照为4.0%。采取网格或带状PE沙障,带状黄柳+带状PE沙障对风蚀坑植被恢复具有良好效果。     

双免耕覆盖对旱地土壤微生物、酶活性和冬小麦干物质转运的影响

为了解双免耕覆盖下旱地土壤微生物数量、土壤酶活性及冬小麦干物质转运特征，研究了双免耕覆盖下麦田土壤中细菌、真菌、放线菌的数量、土壤蛋白酶和脲酶的活性、冬小麦花前和花后干物质向籽粒的转运量与传统耕作（对照）的差异。结果表明，与对照相比，双免耕覆盖下土壤中微生物的数量和酶活性在冬小麦不同生育时期和不同土层均显著（P<0.05）或极显著（P<0.01）高于对照；在0～60 cm土壤中，双免耕覆盖下微生物总量平均较对照高68.2%，差异达极显著水平；土壤中蛋白酶和脲酶活性平均较对照高 27.3%和32.7%。双免耕覆盖下冬小麦花后干物质积累量对籽粒产量的贡献率为44.2%，较对照增加了 61.7%；产量较对照提高18.4%，二者差异达极显著水平。     

Phosphorus fractions and dynamics as affected by land-use changes in the Central Mexican highlands

Land-use change from forest to agriculture in the volcanic ash-derived soils of Mexico has increased over recent decades. It is likely that land uses and management practices, particularly fertilizer use have affected phosphorus (P) distribution and availability. The objective of this study was to evaluate the effects of land-use types (native forest and maize mono-cropping), and the related P addition, on the forms and distribution of soil P and their isotopic exchangeability. An Andisol, sampled from a cropping site, along with the contiguous area under native forest was treated with ³²P-labelled potassium phosphate (KH₂³²PO₄). The soil samples were extracted after incubation times of 7, 21, 35 and 49 days. Phosphorus content and ³²P recovery in fractions sequentially extracted were assessed for each incubation time. Total soil P was dominated by inorganic fractions (79 to 86%) in both land-use types. Resin-Pi, bicarbonate extractable inorganic P (Bic-Pi) and sodium hydroxide extractable inorganic P (NaOH_0.1-Pi) were all raised with P addition. However, the proportion of organic P fraction was reduced under cropped soil. The recovery of ³²P in soils with P addition indicates that resin-Pi, Bic-Pi and NaOH_0.1-Pi comprised nearly all the exchangeable P. In native soils with no P addition, more than 19% of the ³²P was recovered in Bic-Po and NaOH_0.1-Po forms. This finding indicates that organic P cycling is crucial when soil Pi reserves are presented in an inadequate amount. Ecologically based management has to be designed for replenishment and succeeding maintenance of soil organic P compounds to increase sustainable agricultural production.     

汉中市南郑区林地保护利用现状及对策

对汉中市南郑区林地保护利用现状及存在问题进行了分析、评价,提出加强林地保护管理,集约利用和优化配置林地资源,满足林业可持续发展,提高林地保护利用的措施及对策。     

Impact of grassland contract policy on soil organic carbon losses from alpine grassland on the Qinghai–Tibetan Plateau

Carbon storage in the soils on the Qinghai–Tibetan Plateau plays a very important role in the global carbon budget. In the 1990s, a policy of contracting collective grasslands to smaller units was implemented, resulting in a change from the traditional collective grassland management to two new management patterns: a multi‐household management pattern (MMP: grassland shared by several households without enclosures) and a single‐household management pattern (SMP: grassland enclosed and used by only one household). In 2016, 50 MMP and 54 SMP winter pastures on the Qinghai–Tibetan Plateau were sampled to assess the differences in soil organic carbon (SOC) between the two management patterns. Results showed that average SOC was significantly greater under MMP than under SMP, with an estimated 0.41 Mg C/ha/yr lost due to SMP following the new grassland contract. Based on the government's grassland policy, four grassland utilization scenarios were developed for both summer and winter pastures. We found that if the grassland were managed under SMP, likely C losses ranged between 0.31 × 10⁷ and 6.15 × 10⁷ Mg C/yr across the Qinghai–Tibetan Plateau relative to MMP, which more closely resembles pre‐1990s grassland management. Previous estimates of C losses have only considered land use change (with cover change) and ignored the impacts driven by land management pattern changes (without cover change). The new data suggest that C losses from the Qinghai–Tibetan Plateau are greater than previously estimated, and therefore that the grassland contract policy should be reviewed and SMP households should be encouraged to reunite into the MMP. These findings have potential implications for land management strategies not only on the Qinghai–Tibetan Plateau but also other grazing regions globally where such practices may exist.     

Intercropping fenugreek (Trigonella foenum‐graecum L.) and barley (Hordeum vulgare L.) with and without biochar: Tests along a competition gradient

Integrating soil amendment biochar to legume‐based intercropping systems may amplify the intercropping benefits and lead to more sustainable production due to its positive effects on the soil physicochemical and biological environment. Fenugreek (Trigonella foenum‐graecum) is a legume used in an intercropping system in several countries in Southern Europe, the Middle East, and Asia. A barley cultivar and an Iranian fenugreek ecotype were studied in two replacement series experiments to find the best combination of the two species as well as the effect of adding biochar to the soil. Fenugreek and barley were grown in 4‐L pots in five density combinations (20:0, 15:5, 10:10, 5:15, 0:20) with and without application of biochar in sandy loam soil. The biomass, nitrogen (N) and carbon (C) amount of the two crops were measured fifty days after sowing, and the Relative Yield Total (RYT) was estimated. Our results showed that biochar application resulted in a higher total biomass, N and C amount in all combinations of fenugreek and barley. Total biomass was increased by biochar 19.2% when fenugreek was grown alone and 8.1 and 12.9% in series with 25 and 50% barley when biochar was added, respectively. Biochar increased dry matter, N and C accumulation in both crop species in the mixtures. An exception was the C amount of barley which was not influenced by biochar in intercropping. RYT values were largest for biomass, C and N amount in mixtures with 15 fenugreek plants per pot and 5 barley plants per pot corresponding to approximately 400 fenugreek plants per m mixed with 130 barley plants per m². Biochar application increased RYT of the total dry weight by 2.7 and 5.5% in mixtures of 25 and 50% barley plants, RYT of the total nitrogen by 0.8% in mixtures with 25% barley plants, and RYT of the total carbon by 2.7 and 6.6% in mixtures with 25 and 50% barley plants. The RYT values declined with increasing number of barley plants as a result of a less competitive ability of fenugreek when growing in high barley densities. The yield was highest with intercropping but monoculture of barley also resulted in high yields. The total highest yield was found when approximately 130 fenugreek plants per m² were mixed with 400 barley plants per m². Mixtures with 75% fenugreek and 25% barley obtained RYT values larger than 1 for biomass, carbon and nitrogen percentages.     

Monitoring desertification processes in Mongolian Plateau using MODIS tasseled cap transformation and TGSI time series

Most remote sensing studies assess the desertification using vegetation monitoring method. But it has the insufficient precision of vegetation monitoring for the limited vegetation cover of the desertification region. Therefore, it offers an alternative approach for the desertification research to assess sand dune and sandy land change using remote sensing in the desertification region. In this study, the indices derived from the well-known tasseled cap transformation(TCT), tasseled cap angle(TCA),disturbance index(DI), process indicator(PI), and topsoil grain size index(TGSI) were integrated to monitor and assess the desertification at the thirteen study sites including sand dunes and sandy lands distributed in the Mongolian Plateau(MP) from 2000 to 2015. A decision tree was used to classify the desertification on a regional scale. The average overall accuracy of 2000, 2005, 2010 and 2015 desertification classification was higher than 90%. Results from this study indicated that integration of the advantages of TCA, DI and TGSI could better assess the desertification. During the last 16 years, Badain Jaran Desert, Tengger Desert, and Ulan Buh Desert showed a relative stabilization. Otindag Sandy Land and the deserts of Khar Nuur, Ereen Nuur, Tsagan Nuur, Khongoryn Els, Hobq, and Mu Us showed a slow increasing of desertification, whereas Bayan Gobi, Horqin and Hulun Buir sandy lands showed a slow decreasing of desertification. Compared with the other 11 sites, the fine sand dunes occupied the majority of the Tengger Desert, and the coarse sandy land occupied the majority of the Horqin Sandy Land. Our findings on a three or four years' periodical fluctuated changes in the desertification may possibly reflect changing precipitation and soil moisture in the MP. Further work to link the TCA, DI,TGSI, and PI values with the desertification characteristics is recommended to set the thresholds and improve the assessment accuracy with field investigation.