[Impact of land use types on soil macropores in the loess region].

Soil hydraulic conductivity and macropores are important parameters for determining the proportion of precipitation infiltration, simulating soil water and solution transport and establishing the hydrologic model. To investigate the effect of land use types on macropores in soils, soil hydraulic properties, macroporosity and macropore connectivity under different land use types (locust forestland, grassland, farmland and apple forestland) in the loess region were measured by Hood infiltrometer and water retention curve. The results showed that the average hydraulic conductivities under locust forestland, grassland, farmland and apple forestland were 58.60 x 10(-6), 54.90 x 10(-6), 35.30 x10(-6), 23.40 x 10(-6) m x s(-1), respectively. The differences among land use types were statistically significant (P < 0.05). The effective macropores per unit area, macroporosity and macropore connectivity were highest in locust forestland and grassland, followed by farmland and apple forestland. As a consequence of vegetation restoration, macropores which developed by plant roots and animal activity had significantly improved the soil infiltration capability. Restoring woods and grasses should persist in the loess region.

Sediment sources of Yan'gou watershed in the Loess Hilly region China under a certain rainstorm event.

At present the large scale vegetation restoration and intensive oil exploiting had brought huge influence on local environment in Yan'an region. the sediment yield data form series experiment plots and hydrological monitoring station in the Yan'an watershed after one rainfall event on July 2, 2005, which included sediment from different land uses (crop-land plot, vegetation plots, hard road surface) and 3 types roads(mountain-road brunches, mountain-road, and mountain-transport way) has been analyzed. Results showed that the erosion intensity of the 3 type roads was respectively 500 t/km(2), 3163 t/km(2), and 13500 t/km(2). The sediment from cropland and grass, shrub land was within 6-184 t/km(2). It stated that sediment from road area which only covered 1% of total area accounted for 42.3% of the total sediment yield, far beyond that from other uses of land. Sediment from grass-land and shrub-land, which covered 70.5% of watershed area, shared 26.7% of the total sediment. The further analysis showed that the 41.2% of total sediment could be detained by re-vegetation. On the contrary, that road constructing brought heavy sediment which offset the benefit of vegetation restore by 58.4%. the suggestion were to adjust our strategy from slope management to the road erosion mitigation Many studies have confirmed it is an important measure to return the steep slope farming land to green, and to restore vegetation in line with local conditions to prevent soil erosion in the Loess Plateau [1, 2]. To implement the measure in western region, the researches on "Grain for Green", returning farmland to forest and grassland, has become popular [3, 4]. Many scholars studied the effects of farming land and trees and grass land on soil water storage [2, 5]. Tang Keli stated that the slope land for farming was the main source of the sediment in Yellow river, and the maximum gradient slope for farming land use was 25° [6]. Many authorities not only pointed out that a far-reaching influence of land-use changes on the distribution of sediment source area but also put forward some new ideas about returning farming to green in Loess Plateau [7, 8]. However, we were still not sure the contribution of returning farmland to forest and grassland on reducing sediment yield of the valley and known it was difficult to identify its contribution to the total sediment yield. Analysis on the contribution of the stream channel and slope sediment yield had some results already [9, 10]. It was still too early to make clear the relationship between the sediment sources changes of the valley and the management. At present, Ecological restoration in the Loess Plateau caused the sediment form the slope land declining [3]. Due to human economic activities, the mountain road developed rapidly, it is inevitable that road erosion has been intensified [11]. A. Rijsdijk and LA Bruijnzeel (1991), [12] based the valley Konto observation, pointed out that although the rural road in the area accounts for only 3% of the area, but the impact on the sediment of this area was tremendous. Nyssen J, Moneryersons J. et al (2002) [13] also think that road without protection is one of the main sources of sediment. Many kinds of protective measures have great importance to the road erosion control. So attentions were paid to the study on the protection all kind of roads. Then what will happen to the soil erosion of the watershed, driven by the vegetation restoration and new road construction? What will happen to the proportion of sediment quality from slope land, road area and gully? A correct understanding of the sediment sources pattern of the typical watershed is of great significance on assessment the roles of vegetation to slope management and the roles of prevention the linear path erosion.

[Dynamic changes of Robinia pseudoacacia sap flow in hilly-gully region of Loess Plateau].

From April 14 to October 10, 2009, the dynamic changes of Robinia pseudoacacia sap flow in the hilly-gully region of Loess Plateau were measured with thermal dissipation probe. Meantime, the photosynthetic active radiation (PAR), air temperature, relative air humidity, water vapor pressure deficit (VPD), wind speed, and rainfall were monitored. The diurnal variation of the sap flow velocity (SFV) displayed a single-peak curve, but the pattern varied among different months. In April, the sap flow started to increase at about 12:00, and reached the peak at about 18:00. From May to August, the sap flow started to increase at 5:30-7:30, and reached the peak at about 15:00. In September and October, the sap flow started to increase at about 8:00, and reached the peak at 11:30-13:00. The monthly average SFV was the highest in August and the lowest in April, with the value being 0.002610 cm x s(-1) and 0.000549 cm x s(-1), respectively. During the monitoring period, the sap flow velocity was significantly correlated with PAR, air temperature, VPD, wind speed, and air relative humidity, and the correlation coefficients declined in the order of air temperature > VPD > PAR > relative humidity > wind speed. The sap flow velocity could be estimated by the linear equation with variables PAR and VPD, and the regression coefficients were highly significant.

Germplasm-regression-combined (GRC) marker-trait association identification in plant breeding: a challenge for plant biotechnological breeding under soil water deficit conditions.

In the past 20 years, the major effort in plant breeding has changed from quantitative to molecular genetics with emphasis on quantitative trait loci (QTL) identification and marker assisted selection (MAS). However, results have been modest. This has been due to several factors including absence of tight linkage QTL, non-availability of mapping populations, and substantial time needed to develop such populations. To overcome these limitations, and as an alternative to planned populations, molecular marker-trait associations have been identified by the combination between germplasm and the regression technique. In the present preview, the authors (1) survey the successful applications of germplasm-regression-combined (GRC) molecular marker-trait association identification in plants; (2) describe how to do the GRC analysis and its differences from mapping QTL based on a linkage map reconstructed from the planned populations; (3) consider the factors that affect the GRC association identification, including selections of optimal germplasm and molecular markers and testing of identification efficiency of markers associated with traits; and (4) finally discuss the future prospects of GRC marker-trait association analysis used in plant MAS/QTL breeding programs, especially in long-juvenile woody plants when no other genetic information such as linkage maps and QTL are available.

[Dynamic changes of soil moisture in loess hilly and gully region under effects of different yearly precipitation patterns].

Based on field determinations, the dynamic changes of soil moisture in dry farmland, Robinia pseudoacacia forestland, Hippophae shrubland and Bothriochloa ischaemum grassland in loess hilly and gully region under effects of different yearly precipitation patterns were analyzed. The results showed that yearly precipitation pattern had definite effects on the seasonal variation and profile distribution of soil moisture. In normal year, soil moisture in dry farmland had a gentle seasonal variation; in dry year, it decreased slowly before rainy season but increased markedly after rainy season; while in rainy year, it had an overall increase and the increment was remarkable after rainy season. The soil moisture in R. psendoacacia forestland, Hippophae shrubland, and B. ischaemun grassland decreased as a whole in normal year. In dry year, soil moisture in Hippophae shrubland decreased first and increased then, while that in R. psendoacacia forestland and B. ischaemun grassland varied in "W" type, with the minimum in June and August. In rainy year, the seasonal variation of soil moisture in R. psendoacacia forestland and Hippophae shrubland presented "V" type, and that in B. ischaemu grassland fluctuated markedly, with the minimum in August. In dry farmland, the active and sub-active layers of soil moisture were deeper in dry year than in normal year, and the sub-active layer disappeared in rainy year. In R. psendoacacia forestland and B. ischaemu grassland, the active layer of soil moisture was deeper in dry and rainy years than in normal year; while in Hippophae shrubland, this active layer was shallower in dry and rainy years than in normal year.