Conservation Of Weed Diversity And Its Ecological Effects In Red Soil Fields On Slopes

Controversies on the ecological benefits and the harm of keeping weed diversity to crop production in farmland keep hot in recent days. Impacts of weed management strategies on weed diversity and the ecological effects of weed diversity conservation were still poor known although influence of weed on agricultural production and its controlling practice were well documented. The species composition of weed community, its spatial distribution characteristics and the ecological features in rhizosphere of major weed species in red soil fields on slopes in southwestern Zhejiang were determined. Impacts of weed management strategies including weed control by chemical, weed control by mowing, non-weed-controlling, weed control by hoeing, and plant-free bare land on the change of weed community structure, weed species diversity and their ecological effects were detailed studied on the red soil fields on slopes in southwestern Zhejiang, China with completed randomized block field experiments. Additionally, ecological effects of weed species diversity were also measured by combining a randomized field experiment and stimulated pot experiment Main results obtained were shown as follows.1. The species composition of weed community and spatial distribution characteristics of weed species diversity in red soil fields on slopesThe weed community in red soil fields on slopes included 96 species of 27 families during experimental cycle. The species richness of various weed community samples varied from 2.0 to 13.7numbers/m2. The weed species with frequent existence belonged to the families of Poaceae, Luguminosae, Asteraceae, Polygonaceae, Violaceae, Cyperaceae, Oxalidaceae. Weed species diversity in sloping land showed a clear regularity of spatial distribution along with elevation. Weed species number in paddy field, which accounted for 12.6% of total number in the catchment, showed the least diversity while weed species diversity in the transition zone from paddy field to slope land (ecotone) showed the highest diversity. The weed species number in this area accounted for 62.2% of the total number of weed species in the catchment. The weed species diversity in sloping upland is higher thanthat in the paddy field and less than that in the transition ecotone. Horizontally, weed species diversity varied from the different land use patterns. Weed species diversity in the aged orchard showed the highest index followed by the forest The species diversity in newly developed orchard and upland showed the lowest index of species diversity. 2. The ecological features in rhizosphere of main weed speciesThere were significant difference of rhizospheric ecological features (microbial biomass carbon (MBC), phosphorus-solubilizing microbes (PSMs), arbuscular mycorrhizal fungi (AMF), dynamic phosphorus form in rhizosphere) among various weed species. MBC varied from 117.91mg/kg to 499.87 mg/kg among the weed species. The activities of PSMs varied from 580.11 u gP/21d to 6340.75 u gP/21d (ground phosphorite as sole phosphorus source) and from 62.15 ugP/21d to1301.84y gP/21d (lecithin as organic phosphorus source) among the weed species. The colonization rate of AMF varied from 33.8% to 100.00% among the weed species. The total and available phosphorus content varied from 113.44 mg/kg. to 455.81 mg/kg and 4.30 t mg/kg o 48.16 mg/kg separately. Phosphorus content of weed plant varied from 379.99 mg/kg. to 3653.34mg/kg. 3. Impacts of weed management strategies on weed diversityWeed management strategies significantly affected the weed community structure and community succession. Weed control by mowing resulted in an increase of species abundance of weed community and weed species diversity. Weed control by chemical induced a gradually and slowly decrease of weed species abundance and diversity. Non-weed-control treatment showed a change of increasing at first and then decreased weed species abundance and diversity. Weed control by hoeing resulted in an unclear change of weed diversity.The general trend of th...