Simulated recruitment of riparian trees and shrubs under natural and regulated flow regimes on the Wisconsin River,USA

Models that link ecological responses to hydrologic changes are important for assessing the effects of flow regulation on aquatic and riparian ecosystems. Based on the Recruitment Box Model, a graphical model used to prescribe environmental flows for cottonwood (Populus spp.) recruitment, we designed a simulation model to represent the influence of river flow dynamics on seedling recruitment of riparian pioneer woody plants. The model simulates the influence of temporal patterns of river stage on dispersal, germination, initial recruitment and over‐winter survival of first‐year seedlings of riparian pioneer shrubs and trees. We used the model to simulate seedling recruitment patterns for five species (Acer saccharinum, Betula nigra, Populus deltoides, Salix nigra and Salix exigua) on the Wisconsin River (Wisconsin, USA) under three flow scenarios: historic (1935–2002), simulated natural (1915–1975) and simulated regulated flows (1915–1975). Simulation results agreed well with field‐observed relative differences among years (1997–2000) in seedling densities for the five focal species. Simulated successful recruitment years were highly synchronous among species, but species differed in their sensitivity to flows at different times during the growing season, consistent with among‐species differences in seed dispersal timing. Comparison of simulated natural and regulated flows for 1915–1975 showed that flow regulation decreased monthly flow variability, increased late summer to winter baseflow and reduced the magnitude of spring peaks. Simulated recruitment and over‐winter survival of tree seedlings of all species was enhanced under the regulated flow scenario, likely due to increased summer baseflow and reductions in peak flood magnitude. Our analyses show the utility of extending the Recruitment Box Model to include multiple species of riparian shrubs and trees, and the effects of post‐colonization flows on their recruitment success. However, some key functional relationships between flow patterns and woody seedling demography (e.g. shear stress thresholds for seedling mortality) have not been adequately quantified and merit further study. Copyright © 2006 John Wiley & Sons, Ltd.     

IEA joint trials: New lessons from old plantations

Two international trials of potential biomass species families and clones planted in 1985 have been analyzed to determine changing patterns in growth, diseases, and insects. In the Swedish trial, with close spacing and short rotations, Salix viminalis clones gave the best average yield of 17.4 Mg/Ha/yr on the first coppice rotation. In the Minnesota, USA trial, with wider spacings and a longer rotation Populus alba hybrid clones gave the best average yields of 5.5 Mg/Ha/yr. The most important disease and insect problems encountered were Septoria musiva stem cankers on some Populus clones; frost die back in some Salix clones; and the leaf blotch miner, Fenusa dohrnii, on most Alnus families. Recommendations for future international cooperation in field trials are presented.     

化学预浸渍次数对沙柳P-RC APMP木素结构的影响

以沙柳为原料生产盘磨化学预处理碱性过氧化氢机械浆( P-RC APMP),在NaOH总用量8％、H2O2总用量10％时,研究沙柳原料木素(SPL)、单次化学预浸渍的沙柳P-RC APMP中木素(1-PL)和2次化学预浸渍的沙柳P-RC APMP中木素(2-PL)的变化.与SPL总量相比,1-PL和2-PL的总量分别减少8.3％和14.3％;与SPL相比,1-PL和2-PL中的脂肪族羟基含量基本没有变化,但总酚羟基(Tp-OH)含量分别降低了44.2％和47.1％;与SPL相比,1-PL和2-PL的数均分子质量和质均分子质量均逐渐减小,但两者的多分散性逐渐增加.     

不同工艺流程对沙柳P-RC APMP浆料性能的影响

采用沙柳为原料生产高得率碱性H2O2化学机械浆,发现在NaOH总用量为8%,H2O2总用量为10%时,和沙柳单段P-RC APMP浆料相比,沙柳双段P-RC APMP浆料的白度增加8.34%,裂断长增加21.82%,耐破指数增加24.83%;浆料内的细小纤维较沙柳单段P-RC APMP中的细小纤维多,纤维表面的碎片较多,纤维分丝帚化的程度较大;纤维的结晶度降低了3.45%。     

Hydrologic thresholds for riparian forest conservation in a regulated large Mediterranean river

Most riparian trees are phreatophytic, water table‐dependent plants which broadly differ in their tolerance to drought and permanent flooding. In semi‐arid settings, as water is limiting, inundations may be regarded as inputs rather than stresses for the survival of phreatophytes. In this study, the mortality rates and abundances of Populus alba, P. nigra, Salix alba and local Tamarix spp. were examined in 43 plots with different hydrologic conditions distributed across the floodplain of a large semi‐arid and Mediterranean river, the Ebro River (Spain). The objectives were to determine hydrologic thresholds for the maintenance of declining populations of those species, while providing novel information on their phreatophytic nature, and to examine shifts in the species composition along hydrologic gradients. All species exhibited significant relationships between mortality rates and hydrologic variables (deepest water table—WT, flood duration—FD and flood frequency—FF). S. alba was found to be the species with lowest tolerance to drier conditions (hydrologic thresholds for maintaining a mortality rate <50%: WT > ?1.22 m; FD: out of observation range; FF > 5.4 events y^?1), followed by P. nigra (WT > ?2.18 m; FD > 11.1%; FF > 3.8 events y^?1), Tamarix spp. (WT > ?2.96 m; FD > 3.7%; FF > 2.5 events y^?1) and P. alba (WT > ?3.45 m; FD > 1.7%; FF > 2.0 events y^?1). Only a significant reduction in S. alba relative abundance was observed as conditions got drier. The results provided quantitative information useful to guide management plans for the protection of Mediterranean phreatophytic tree species from further degradation and suggested that eventual natural or regulation‐induced droughts and groundwater declines would accelerate the loss of all phreatophytic species, especially S. alba. Copyright © 2010 John Wiley & Sons, Ltd.     

Tree colonization trends on a sediment bar after a major flood

Tree mortality and regeneration in riparian areas are greatly influenced by flooding. The elevational distribution of Salix spp. and Robinia pseudoacacia were investigated by observing densities and standing conditions before and after a major flood on a sediment bar in the middle reaches of the Arakawa River in Kumagaya, Japan. The subsequent tree recruitment was also examined. R. pseudoacacia was easily washed away with the eroded sediment, whereas Salix spp. was found to be more tolerant. Both species were able to survive even after collapsing, provided that their roots were fully or partially embedded in the sediment. Re‐shooting of collapsed trees, rather than emergence from saplings (either by seeds or vegetative fragments), was observed to be the major method of recruitment after the flood. Therefore, tree density before the flood was unchanged, unless the trees were subject to washing away. Salix spp. recruitment was mainly observed in low‐lying areas and R. pseudoacacia in elevated areas. Recruitment from saplings was species‐specific. Salix spp. at high elevations originated mainly from shoot fragments as they need high levels of moisture for seed germination and at higher elevations, sediment moisture content is very low. R. pseudoacacia, on other hand, originated mainly from roots and seeds. At a given elevation, past recruitment patterns indicated that the annual recruitment of trees increased with tree density up to a particular threshold of recruitment density. Further increases in tree density beyond that optimum value resulted in a decline in recruitment. Furthermore, threshold density was observed to increase along with elevation for R. pseudoacacia while declining with Salix spp. Copyright © 2010 John Wiley & Sons, Ltd.     

Sampling procedure in a willow plantation for estimation of moisture content

Heating value and fuel quality of wood is closely connected to moisture content. In this work the variation of moisture content (MC) of short rotation coppice (SRC) willow shoots is described for five clones during one harvesting season. Subsequently an appropriate sampling procedure minimising labour costs and sampling uncertainty is proposed, where the MC of a single stem section with the length of 10–50 cm corresponds to the mean shoot moisture content (MSMC) with a bias of maximum 11 g kg⁻¹. This bias can be reduced by selecting the stem section according to the particular clone. The average difference in MSMC between the largest and smallest shoot in a stump was 31 g kg⁻¹. This variation is only marginally smaller than the variation found in MC between stumps. The MC of individual stem sections may vary as much as 190 g kg⁻¹ in one shoot. Variation in whole shoot moisture content was primarily influenced by the shoot diameter, but in addition significant effects of clone and shoot age were found.     

超微粉碎技术在沙柳原料预处理中的应用

以沙柳为原料,研究了超微粉碎预处理技术对沙柳原料酶水解效果的影响,基于Box-Behnken实验设计,对经过超微粉碎预处理的沙柳原料,采用响应面分析法优化了超微粉碎沙柳原料稀碱预处理的工艺条件,考察了原料粒径,稀碱处理过程中碱浓度、处理时间、处理温度对原料水解的影响,并建立了工艺数学模型.通过实验得到最佳超微粉碎沙柳原料酶解的预处理条件:原料粒度(15μm)、0.79％NaOH、94.6℃、43.4min,原料的酶解率可以达到最大值.结果表明,超微粉碎预处理的沙柳原料经过稀碱预处理后可明显提高纤维素的酶水解效率,该模型为超微粉碎沙柳原料酶解工艺的进一步研究提供了依据.     

超微粉碎预处理沙柳原料酶解条件优化

研究了超微粉碎预处理技术在沙柳原料酶水解中的应用。沙柳原料经过超微粉碎处理后,通过正交实验设计优化原料的稀酸高温预处理条件,得到最佳的预处理参数为：原料粒度（15μm）、固液比1：12、温度160℃、H2SO4 0．5％、时间20min;经过预处理的沙柳原料通过混料实验设计法对纤维素酶的复配条件进行优化,得到最佳的纤维素酶系比例为：滤纸酶活（FPU）：CMC酶活（IU）：β-葡萄糖苷酶（IU）：木聚糖酶（IU）=1．52：5．35：29．55：1,该酶系比例的纤维素酶比使用单一商品纤维素酶水解效率提高了28％以上。     

预浸渍对沙柳两段P-RC APMP浆料性能的影响

研究了预浸渍化学药品NaOH和H2O2的用量对沙柳两段P-RCAPMP浆料性能的影响。结果表明:NaOH和H2O2用量分别是影响沙柳两段P-RCAPMP强度性能和白度的主要因素,NaOH最佳总用量为8%,H2O2的最佳总用量为10%;当第一段浸渍时NaOH和H2O2用量比大于1,二段化学浸渍NaOH和H2O2用量比一般小于1时,浆料的强度和白度都能得到最佳效果。