滴灌下天山北坡棉田杂草生态位及其排序分析

Niche and Ordination of Weed Communities in Cotton Fields Under the Condition of Drip Irrigation in Northern Slope of Tianshan Mountain

运用七级目测法调查了天山北坡5个地区25个滴灌棉田样点的杂草优势等级,并转换成重要值数据,在此基础上计测了天山北坡滴灌棉田20种主要杂草的生态位宽度和生态位重叠值;以杂草的优势度和生态位重叠值为依据,用DCA排序和图论聚类分析中的最小生成树法,作出反映杂草生态学相似关系的排序图和最小生成树。结果表明:田旋花(Convolvulus arvensis)、藜(Chenopodium album)、反枝苋(Amaranthus retroflexus)、龙葵(Solanum nig-rum)、芦苇(Phragmites australis)、狗尾草(Setria viridis)、苘麻(Abutilon theophrasti)、野西瓜苗(Hibiscus trionum)、稗草(Echinochloa crusgalli)等9种杂草的实际生态位较宽,它们是天山北坡滴灌棉田的优势种群(恶性杂草);莴苣(Lactuca tatarica)和播娘蒿(Descurainia sophia),稗草、野西瓜苗、反枝苋、苘麻,田旋花、藜、龙葵、狗尾草、芦苇等杂草间的生态位重叠值较大,对资源的竞争较为激烈。最小生成树法依据生态位重叠值的大小关系来反映杂草的生态需求相似程度,其将20主要种杂草划分为3组。对25个样地20种主要杂草综合生态需求的DCA排序表明:恶性杂草基本都聚集于排序图中央,与一般杂草区分明显,并与最小生成树对应较好;对5个地区各样方间生态相似关系的DCA排序表明:143团与奎屯两地区各样方在排序图中相互交织,说明棉田间杂草种类及其优势度较为相似,而其他地区间差异较明显。最小生成树中对不相邻的杂草没有明确的表明它们之间的生态关系,而DCA排序虽能从整体上反映所有杂草间的生态相似关系,但仍会丧失少量生态学信息。因此将两种方法结合,优势互补,优越性明显。

In cotton fields under the condition of drip irrigation in northern slope of Tianshan Mountain,25 random sampling fields in 5 regions under different ecological conditions were surveyed in detail with ＂seven scales by visualization＂ of weed dominance to cotton to obtain the weed important value. The 20 main weeds niche breadth and niche overlap were caculated on the basis of the data above. The minimal spanning tree and a two-dimensional scatter poh of DCA ordination revealing weed ecological similiarity were drawed based on niche overlap value. The results show that Convolvulus arvensis ,Chenopodium album ,Amaranthus retroflexus ,Solarium nigrum,Phragmites australis ,Setria viridis ,Abutilon theophrasti,Hibiscus trionum,Echinochloa crusgalli had bigger niche breadth as compared with those of other species ,being the important weed in cotton fields under the condition of drip irrigation in northern slope of Tianshan Mountain, the niche overlaps between Lactuca tatarica,Descurainia sophia, Echinochloa crusgalli ,Hibiscus trionum ,Amaranthus retroflexus ,Abutilon theophrasti, Convolvulus arvensis ,Chenopodium album, Solanum nigrum,Setria viridis ,Phragmites australis were higher. The minimal spanning tree method based on niche overlap value to reflect similar degree of the ecological needs of the weeds,20 main weeds will be divided into 3 groups. DCA ordination of 20 main weeds comprehensive ecological needs of 25 sampling sites：the vicious weeds all gathered at the central sorting chart, the distinction is obvious with the general weed and the corresponding of DCA ordination chart with minimal spanning tree is better; DCA ordination chart of sampling quadrats of 5 regions：all sampling quadrats of 143 corps and Kuytun intertwine mutually in the ordination chart,it shows：the species and its dominance of weeds in cotton fields is more Similar, but other interzone difference is obvious. The minimal spanning tree by its focus on the results of which show that weeds are the most similar to the ecological requirements, but not be used for the no adjacent species, and no clear that the ecological relationship between them, the DCA sorting can reflect the ecology similar relations between all weeds wholely,though this method will lose a small amount of ecological information through the data conversion. Therefore the two methods will be combined, complementary advantages,the superiority is obvious.