流动沙丘先锋植物沙米的生态防护作用

使用野外风速廓线仪与阶梯式集沙仪,对流动沙丘先锋植物沙米及其群落的生态防护作用进行了野外实地观测研究。研究结果表明,沙米植株成塔状,基部分枝,株高变异性、可塑性大,与其他形态指标呈显著正相关,通过测定株高可掌握其基本形态特征。立枯沙米单株可降低风速90%以上,并能阻挡风沙流形成沙舌,沙舌积沙量、高度、长度与沙米体积、高度和冠幅呈显著相关。沙米群落粗糙度达到6.325 cm,是裸露流沙区的2635倍。在裸露流沙区200 cm高度风速为6.2 m/s时,裸露流沙区输沙量达到86.34 g/cm.h,而沙米群落中无风沙流发生;风速为9.5 m/s时,裸露流沙区输沙量也达到沙米群落的574倍。研究认为,在短期(2~3年)和局部空间范围(流动沙丘坡脚与两翼以及裸沙斑块),立枯沙米及其群落具有较明显的防风固沙作用;发达的生殖生长、侧枝系统和侧根系统,枯死后可保留2~3个生长季,是沙米发挥防风固沙作用的关键所在。     

Conventional tillage improves the storage of soil organic carbon in heavy fractions in the Loess Plateau,China

Soil labile organic carbon(C) plays an important role in improving soil quality. The relatively stable fractions of soil organic C(SOC) represent the bulk of SOC, and are also the primary determinant of the long-term C balance of terrestrial ecosystems. Different land use types can influence the distribution patterns of different SOC fractions. However, the underlying mechanisms are not well understood. In the present study, different fractions of SOC were determined in two land use types: a grazed grassland(established on previously cultivated cropland 25 years ago, GG) and a long-term cultivated millet cropland(MC). The results showed that C concentration and C storage of light fractions(LF) and heavy fractions(HF) presented different patterns along the soil profiles in the two sites. More plant residues in GG resulted in 91.9% higher LF storage at the 0–10 cm soil depth, further contributed to 21.9% higher SOC storage at this soil depth; SOC storage at 20–60 cm soil depth in MC was 98.8% higher than that in GG, which could be mainly attributed to the HF storage 104.5% higher than in GG. This might be caused by the long-term application of organic manure, as well as the protection from plough pan and silt- and clay-sized particles. The study indicated that different soil management practices in this region can greatly influence the variations of different SOC fractions, while the conventional tillage can greatly improve the storage of SOC by increasing heavy fractions.     

固沙植物沙米光合特性研究

采用Li—6200光合分析仪对沙地一年生植物种沙米的Pn进行了日变化和季节变化测试,结果表明：沙米光合速率日变化呈双峰曲线,其Pn第一峰值和第二峰值分别为13.38μmol/(m2·s)和9.428μmol/(m2·s)。沙米Pn在季节变化中平均高峰值在7月份为7.3428μmol/(m2·s)。沙米的光补偿点较低为127.3μmol/(m2·s)。在生长季节中沙米的水分利用效率（WUE）平均值为0.5707,最大平均值出现在6月份为0.7145。经对沙米Pn及其多项影响因子的相关分析,得出：沙米Pn与其因子QNTM、EAIR、TRAN呈极显著正相关关系相关;与CINT呈显著负相关关系。并得出沙米Pn及影响因子之间的回归方程。     

沙蓬种子的生活力测定和休眠破除方法

研究了四唑液质量分数和染色前预处理对沙蓬(Agriophyllum squarrosum)种子生活力测定的影响,以及不同预处理方法破除沙蓬种子休眠的效果。结果表明,染色前刺破种皮法可缩短沙蓬种子四唑染色时间,以1.0%四唑溶液染色14~18 h效果最佳。种皮刺破法亦可有效地破除沙蓬种子的休眠,种子吸胀7 d后刺破种皮,各种样第2天种子即迅速萌发,第7天发芽率平均达92%,较未刺破种皮平均发芽率提高47%。     

不同处理方式对流动沙丘先锋植物沙米种子萌发的影响

为解决种子自然萌发率低的问题,以不同生态区域沙米种子为实验材料,研究GA3处理、双氧水处理、乙烯利处理、紫外线照射处理、冷冻处理对沙米种子萌发的影响。研究结果表明:5种处理方式对沙米种子萌发均具有不同程度的促进作用。其中,GA3(2000 mg/L)和乙烯利(400~600μmol/L)的处理条件下4个生态区域沙米种子发芽率均高达100%;随紫外线照射时间的延长,种子萌发率先升高后降低,在紫外线照射24 h下发芽率最高;-20℃冷冻处理下沙米种子发芽率最高,奈曼旗(96.7%)沙坡头(95.6%)民勤(21.11%)敦煌(17.78%)。     

Effect of Agronomic Factors on Annual Leguminous Forage Crop in Mediterranean Environments

Dry matter and seed production of five annual leguminous species hairy vetch ( Vicia villosa Roth cv. Orsara) , crimson clover ( Trifolium incarnatum L. ecotype Campano) , squarrosum clover ( T. squarrosum L. ecotype Calabro) , persian clover ( T. resupinatum cv. Accadia) and fenugreek ( Trigonella foenum-graecum L. ecotype Maltese) was estimated in 1989–90 under two density and irrigation rates and with two cutting treatments. The experiments were done at the Forage Crops Institute of Foggia, which has a typical Mediterranean environment. The forage cut severely affected the regrowth of the plants in all species. The year and irrigation factors affect dry matter, seed production and seed yield components more than the plant density rates. The averages over the years, for dry matter and seed yield were 21.0 % and 20.5 % higher in the irrigated than the not irrigated ones. The lower plant density rate, for seed yield trait, gave better result in hairy vetch in irrigated and non-irrigated treatment. Whereas in the other species, the lower rate of planting gave greater yield under non-irrigated and the higher rate under irrigated growing condition. The seed yield components most influenced by irrigation were: thousand seed weight and seeds/pod in hairy vetch and heads/tiller and seeds/head in clovers species. Fenugreek was the earliest forage crop (cut at the beginning of March), followed by crimson and persian clovers (cut at the middle of April) and squarrosum clover and hairy vetch (cut in the middle-late of May). All the cultivars and ecotypes considered not regrowth after cut and could represent an important fresh forage resource for the period March–May for the Mediterranean regions.     

流动沙丘先锋植物沙米种子萌发影响因素

种子萌发是沙米种子的唯一繁殖方式,以流动沙丘先锋植物沙米种子为试验材料,研究了光照、GA3、Na Cl、PEG对沙米种子萌发的影响。研究表明,沙米种子在黑暗条件下的萌发高于光照条件下的萌发;GA3处理对沙米种子的萌发具有促进作用,其中以0.1%、0.15%浓度GA3处理的萌发率高达99.6%,而且不同浓度处理间达到极显著差异;随着盐胁迫加剧,沙米种子萌发率降低,以50%的Na Cl溶液处理下的种子萌发最高;随着PEG渗透势的下降,沙米种子的萌发得到不同程度的抑制,PEG渗透势越低,抑制作用越明显,在渗透势阈值为-0.0676 MPa时,种子萌发较高。研究表明,沙米种子萌发受到自身因素和外部的生态环境等因素的影响,沙米种子喜于黑暗条件下萌发,属于一种厌光型种子,GA3对沙米种子的萌发具有显著促进作用,盐胁迫和干旱胁迫对沙米种子的萌发具有不同程度的抑制作用。该研究结论为揭示沙米的生态适应机制以及沙米人工栽培提供了理论依据和技术支撑。     

三种一年生藜科沙生植物出苗对沙埋深度和水分条件的响应

通过盆栽控制试验,研究了沙米、大果虫实和长穗虫实3种一年生沙生植物在4个模拟降水水平(A、B、C和D)和6种埋深水平(0,10,20,30,40和50 mm)的出苗情况。结果表明,3种植物种子均没有休眠现象。沙米和长穗虫实均在10 mm埋深处的出苗率最大,而大果虫实在30 mm埋深处的出苗率最大,沙米、大果虫实和长穗虫实,各降水处理的平均出苗率分别为50.63％,77.29％和75.21％。在沙土表面的种子,沙米萌发受强烈抑制,而其余2种植物在降水较多的A、B和D处理下萌发较多但成苗较少。这3种植物耐埋深的大小依次为:大果虫实>沙米>长穗虫实。降水量越大,其出苗率越高,沙米和大果虫实单次强降水下其种子出苗率大于等量的多次少量降水的积累,但是长穗虫实相反。这表明在干旱半干旱沙地,降水是调节季节性种子出苗最重要的决定因素,种子在沙土中的垂直分布决定了降水后种子萌发的比例并有助于维持土壤种子库。     

沙米生长特性调查

通过对沙米生长特性、种群动态及其对水分的影响等方面系统的调查,探讨流动沙丘上若留有片状枯萎的沙米,（翌年）沙米植株之间就不再生长新生沙米的可能原因。同时,利用先锋植物的这种生态适应机制,探讨了沙漠地区短命植物适应干旱环境的生长特性。