风沙化土地逆转过程中生态环境变化的研究

通过对山东省禹城市沙河洼风沙化土地逆转过程中中小气候、风沙流结构、土壤养分、土壤微生物、土壤物理性状及植被群落等观测，研究了该地区生态环境的变化特征，指出采取综合治理措施是改善脆弱生态环境的有效途径。     

Bulk soil C to N ratio as a simple measure of net N mineralization from stabilized soil organic matter in sandy arable soils

Investigations of 23 northwestern German sandy Ap horizons (mean clay content 35 g kg⁻¹), that had higher organic matter (OM) levels than expected for sands, showed that the bulk soil C to N ratio reliably indicated the release of N from stabilized OM. Soils were incubated at 35 °C for 200 days under aerobic conditions. Cumulative N release curves were split into N released from fresh materials (N_fast) and N released from the larger pool of stabilized, older OM (N_slow rates, 0.06-0.77 μg N g⁻¹ soil d⁻¹, or 0.7-49 μg N g⁻¹ OM). Correlating the N_slow rates with total N contents of soils yielded no satisfactory relationships while their relationship with C to N ratios was very close (negative exponential, R²=0.88). Low rates of N release (N_slow) per unit of OM occurred if C to N exceeded 15. This was associated with historical factors like podzolization, calluna heathland, plaggen fertilization or a combination of these.     

不同施肥水平高分子聚合物对蓖麻产量及土壤水分利用效率的影响

以蓖麻为试材,研究了不同施肥条件下高分子聚合物对沙地的改良和利用效果。结果表明,播前在沙地施入高分子聚合物后再施用肥料,可以有效的提高土壤的保水能力,改善作物的生长习性和提高产量,减少耗水量和提高作物水分利用效率。对蓖麻产量和水分利用效率影响最大的为氮肥,其次为磷肥,钾肥最小。氮、磷、钾肥配合施用效果最好。     

应用HYDRUS-1D模拟砂质夹层土壤入渗特性

依据非饱和土壤水分运动理论,采用HYDRUS-1D软件,对砂质夹层土壤入渗特性进行数值模拟,分析各因素对砂质夹层土壤入渗规律的影响。结果表明:砂质夹层结构对土壤入渗特性有较大影响,具有暂时的阻水和减渗作用;湿润锋穿过砂层上界面后,入渗过程变为稳渗阶段,稳渗率主要受砂层质地、砂层埋深和压力水头影响,与土壤初始含水率和砂层厚度无关;砂质夹层土壤剖面水分分布不连续,上层土壤基本饱和,砂层土壤未饱和,土壤剖面含水率主要受砂层质地、砂层埋深和砂层厚度的影响。研究结果可为农业水资源利用及工程防渗技术提供理论依据。     

风沙土中荒漠植物出苗和生长的比较研究

选择了5种荒漠植物红砂（Reaumuria soongorica）、泡泡刺（Nitraria sphaerocarpo）、花棒（Hedysarum scoparium）、白刺（Nitraria tangutorum）和沙拐枣（Calligonum mongolicum），设计了沙埋和幼苗生长两个控制实验，来研究它们的萌发出苗和生长定植能力。结果表明：5种植物的高出苗率、快出苗现象集中在0～3cm的沙埋深度；红砂、泡泡刺、花棒、白刺、沙拐枣的最佳沙埋深度分别为1cm、2cm、2．5cm、2cm和5cm。出苗率与沙埋深度方程的斜率显著相关于种子重量。种子重量与幼苗的绝对生长率、相对生长率正相关。相对生长率与单位叶速率和叶面积干重比显著正相关，但和叶面积比率和叶干重比率显著负相关。种子重量与根绝对伸长速率无关，但与根长比率和根长叶面积比率显著负相关。种子重量和单位叶速率是出苗和生长的较好的指示者，但仅仅种子重量和幼苗相对生长率并不能预示植物成活能力。     

干旱胁迫对沙枣幼苗根茎叶生长及光合色素的影响

干旱半干旱地区水分是植被恢复和演替的限制性生态因子,沙土生物结皮能降低水分入渗,造成土壤水分浅层化和加剧土壤水分时空分异,因此有必要采取措施进行适度干扰,以促进生态恢复和重建。土壤蒸发是天然降水无效损失的一个重要途径,研究生物结皮对土壤蒸发的影响十分必要。以陕北水蚀风蚀交错区沙土生物结皮为研究对象,分析了移除生物结皮和沙埋2种干扰下生物结皮类土壤水分蒸发特性。结果表明,移除生物结皮并不能起到显著地抑制土壤蒸发的作用(p>0.05),而沙埋对土壤蒸发具有显著地抑制作用(p<0.01),且随沙埋厚度的增加,蒸发抑制率提高。20mm沙埋的抑制蒸发作用最大,蒸发抑制率达到了58.15%。5mm和10mm沙埋的蒸发抑制率则分别为25.20%和28.29%,二者之间的差异未达到显著水平(p>0.05)。可见,沙埋对于改善土壤水分状况具有极积意义,但应控制沙埋的厚度。     

Role of root-hairs and hyphae in adhesion of sand particles

The aggregation process in sandy soils depends on biological activity. We reported here results obtained from one sample time of: (a) adhesion of sand particles by root hairs and fungal hyphae, examined on root sections of four plant species (amaranth, Amaranthus hypochondriacus L.; Bermuda grass, Cynodon dactylon L.; maize, Zea mays L. and sunflower, Helianthus annuus L.) grown at field for 3 months; (b) root-adhering soil (RAS), root biomass (RB), and dry and water stable-aggregate fractions obtained from root:soil monoliths; and (c) arbuscular mycorrhizal colonization. Microscope observations on fine roots (<1 mm) showed that root hairs and hyphae contributed simultaneously, but not in the same proportion, to enmeshment of sand particles (20-150 μm). Hyphae contribution was considerably fewer than that of root-hairs. Maize and Bermuda grass had a higher root-hair density but a lower amount of external hyphae than those of amaranth and sunflower. Root-hairs of Bermuda grass and maize held approximately three times more sand particles than those of amaranth and sunflower (20 and 7 mm⁻¹ of root section, respectively). These results were consistent with the higher RAS:RB ratio of Bermuda grass and maize (302 and 257, respectively), than that of amaranth and sunflower (89 and 159). Intensity of mycorrhizal colonization in the whole root system was higher in maize, Bermuda grass and sunflower (range of 22.7-25%) as compared to that of amaranth (6.8%). A. hypochondriacus, considered as a non-mycorrhizal plant species, showed typical structures (vesicles, hyphae and arbuscules) in the root system. Results emphasized the preponderant role of root hairs (of grasses and dicotyledon species) in the process of soil adhesion by roots under sandy conditions (pumice and feldspath particles) and semi-arid climate.     

化学疏花疏果对砂梨座果率的影响

初步试验结果表明：盛花期喷布３００×１０－６乙烯利，或１波美度石硫合剂，幼果期喷布２０００×１０－６敌百虫，或２０×１０－６禁乙酸铵＋１００×１０－６乙烯利，分别对晚三吉和身不知等砂梨品种的疏花疏果作用，达显著或极显著水平。     

氮、钾、钙对柑桔幼苗生长与光合生理的影响

采用三因素五水平回归最优设计、砂培方法,研究了营养液中不同浓度 N、K、Ca 对椪柑实生苗生长与叶片叶绿素含量、光合强度及矿质养分吸收的影响,建立了相应的数学模型并对其进行了解析。结果表明;N 是影响柑桔叶片光合性状的重要因素,Ca、K 影响相对小些;叶片光合强度最大时的营养液组成是:N=230×10~(-6),K=130×10(-6),Ca=291×10~(-6);一定范围内,叶绿素含量、光合强度与叶片含 N、含 K 量成正相关;N 和 K 互相促进吸收,增施 K 时只有配合适量 N 才能更大程度地提高叶片的光合能力;叶片含 Ca 量随培养液与叶片中 N、K 含量升高而呈下降趋势。     

吉林省西部风沙地樟子松林技术的初步探讨

本文探讨了在干旱的吉林省西部风沙地樟子松造林技术。通过穴下栽植樟子松的试验，得出：樟子松当年造林成活率达到９０．７％，第三年造林保存率达到８５．２％，分别比常规造林（对照）提高７３．７％、７７．ｇ％。