Man-made desert algal crusts as affected by environmental factors in Inner Mongolia, China

Man-made desert algal crusts were constructed on a large scale (3000m(2)) in Inner Mongolia, China. Microcoleus vaginatus was mass cultivated and inoculated directly onto unconsolidated sand dune and irrigated by automatic sprinkling micro-irrigation facilities. The crusts were formed in a short time and could resist the erosion of winds and rainfalls 22 days after inoculation. The maximum biomass in the man-made algal crusts could also reach 35 mu g Chl a/cm(2) of soil. Effects of environmental factors such as temperature, irrigation, rainfall and soil nutrients on algal biomass of man-made algal crusts were also studied. It was found that rainfalls and lower light intensity had significantly positive effects on the biomass of man-made algal crusts. The preliminary results suggested that man-made algal crusts could be formed rapidly, and thus it might be a new feasible alternative method for fixing unconsolidated sand. (c) 2006 Elsevier Ltd. All rights reserved.

花椒叶和土壤浸提液对土壤微生物、土壤酶及土壤化学性质的影响

花椒（Zanthoxylum bungeanum Maxim.）是川西地区重要的经济植物，化感作用是花椒连作障碍的原因之一，而花椒凋落物和根系分泌物对土壤质量的影响是花椒化感作用的一个重要方面。系统研究花椒如何影响土壤有助于深入理解和解决花椒连作障碍。本文主要以大红袍（10a生）花椒叶和种植过花椒的土壤的浸提液浇灌花椒幼苗进行试验，分析叶浸提液与土壤浸提液对非花椒生长土壤中土壤微生物、土壤酶及土壤化学性质的影响。主要结果如下： 1.花椒叶浸提液和土壤浸提液减少了土壤中微生物的种类、组成和数量。本试验中未施加浸提液的土样中根际微生物明显高于非根际区，在经过花椒叶浸提液处理后，根际细菌、真菌和放线菌数量以及微生物总数都有所减少，这样将会导致土壤中的有效养分的供给减少，进而可能影响植物的生长。 2．施加花椒叶浸提液和土壤浸提液，以及花椒幼苗的栽种，对不同土样中的土壤酶各有促进和抑制作用。在浸提液处理下，水解酶之间及氧化还原酶之间各存在相互促进作用。 3.施加花椒叶浸提液和土壤浸提液均抑制了根际土中全氮和有机质含量，叶浸提液还抑制了无苗土中全磷含量，土壤浸提液还抑制了无苗土中全氮含量与根际土全磷、有机质含量。但两种浸提液均促进了根际土中有效磷和水解性氮含量、根外土中全磷含量，叶浸提液促进了根际土中全磷含量，土壤浸提液促进了根外土中有效磷含量。全氮和有机质含量的下降可能对植物生长发育不利。 4．土壤化学性质与土壤酶活性在不同土样中有不同的相关性。全氮含量在施加叶浸提液的土样中与蛋白酶活性呈正相关。水解性氮含量在施加叶浸提液的土样中与蛋白酶活性、蔗糖酶活性呈正相关。全磷含量在施加叶浸提液的土样中与多酚氧化酶活性呈正相关；在施加土壤浸提液的土样中与蛋白酶活性、蔗糖酶活性呈正相关，与多酚氧化酶活性呈负相关。有效磷含量在施加叶浸提液的土样中与多酚氧化酶活性呈正相关，与蛋白酶活性呈负相关；在施加土壤浸提液的土样中与蛋白酶活性、过氧化氢酶活性呈正相关。有机质含量在施加叶浸提液的土样中与蛋白酶活性、蔗糖酶活性呈正相关。 Zanthoxylum bungeanum is one of the most important cash crops in Eastern Tibetan Plateau. Allelopathic effects could be one of reasons for Z. bungeanum’s continuous cropping impediment. The effects of secretion of leaf and root of Z. bungeanum on soil quality is a important way of Z. bungeanum’s allelopathic effects. However, allelopathic effect of Z.bungeanum on soil microbes, enzyme activities and chemical property were seldom studied. In this study, leaf and soil extracts of Da Hongpao(DHP), the most common varieties of Z.bungeanum in this area, were used to assess allelopathic effect of Z. bungeanum on soil biology and biochemistry by pot experiments . The main results showed that: 1. The irrigation of two kinds of extracts reduced the species, component and quantity of soil microbes. In rhizosphere soil which irrigated by distilled water, the quantity of soil microbes is significantly different from exoroot soil. In rhizosphere soil which irrigated by leaf extracts, the quantity of bacterial, fungi, actionmycete and gross of microbes were decreased, it may resulted in reduce of Available nutrient in soil, and influenced the growth of plants. 2．The irrigation of two kind of extracts reduced or enhanced the enzyme activities in different soils. Interaction between hydrolytic ferments and redoxases were promoted each other. 3. The irrigation of two kinds of extracts reduced the total N and organic matter in rhizosphere soil. Leaf extracts also reduced the total P in soil without seedling. Soil extracts reduced total N in soil without seedling and total P, organic matter in rhizosphere soil. But both extracts also enhanced available P and hydrolysable N in rhizosphere soil, total P in exoroot soil. Leaf extracts enhanced total P in rhizosphere soil. Soil extracts enhanced available P in exoroot soil. The reduction of total N and organic matter may influence growth of plants. 4．Positive correlations between total N and prolease, hydrolysable N and prolease, hydrolysable N and saccharase, total P and polyphenol oxidase, available P and polyphenoloxidase, organic matter and prolease, organic matter and saccharase, were studied in soil irrigated by leaf extracts. In soil irrigated by soil extracts, there are positive correlations between total P and prolease, total P and saccharase, available P and prolease, available P and catalase, while negative correlation between total P and polyphenoloxidase, available P and prolease, available P and catalase was found.

Habitat use by wintering Ruddy Shelduck at Lashihai Lake, Lijiang, China

Habitat use by wintering Ruddy Shelduck (Tadorna ferruginea) in Lijiang Lashihai Lake of southwest China was studied from 1 November 1999 to 29 April 2000. We divided habitats into five types-deep water, shallow water, mudflat, grassland and farmland. Shallow water and grassland, with rich food and easily accessible water, were preferred by wintering Ruddy Shelducks, Farmland was preferred in mid-winter but avoided in early winter and late winter. Even in mid-winter, the feeding Ruddy Shelduck on farmland were not equally distributed in fields and preferred wet fields (just irrigated) and avoided dry fields. In dry fields, the distances to water sources had great impact on the feeding distribution. Mudflats were only selected in later winter, coinciding with the growth of water-weeds. Deep-water areas were always avoided. Prohibition of human disturbance and retaining shallow water areas and grassland are important measures to mitigate conflict between Ruddy Sheldruck and local people.