Two surveys were conducted to investigate weed vegetation in a 153-hm^2 sampling area of summer crop fields from Anhui Province, China, through visual scoring of the level of weed infestation compared with summer crop...Two surveys were conducted to investigate weed vegetation in a 153-hm^2 sampling area of summer crop fields from Anhui Province, China, through visual scoring of the level of weed infestation compared with summer crops on a seven-class scale. In total, 155 sampling sites were selected in the field based on crops, tillage, rotation systems, geographical regions, and soil types across the province. Data on weed communities and environmental factors were collected and analyzed through principal component analysis （PCA） and canonical correspondence analysis （CCA）, and the output was interpreted ecologically. Results showed that the main factors influencing the structure and distribution of weed communities in summer crop fields were the soil submersion period, latitude, and soil type and pH. The CCA indicated a significant relationship between weed dominance and soil submersion duration, latitude, and soil pH. From the result of the PCA and CCA ordination, the 155 sampling sites could be divided into three groups based on geographic and floristic composition, as well as weed abundance. The southern dry land group, which was characterized by a double-cropping system in the hilly regions of southern and central Anhui Province with a continuous summer crop and an autumn dry land crop, was dominated by Galium aparine Linn. var. tenerum （Gren. et Godr） Robb., Avenafatua L., and Veronica persica Poir. The northern dry land group, which had the same cropping system as the southern dry land group, was dominated by G. aparine var. tenerum, Galium tricorne Stokes, Descurainia sophia （L.） Schur., and Lithospermum arvense L. in the North Anhui Province, China. These two dry land groups could be combined into one large dry land group, in which the Galium weed vegetation type dominated. The third group was the paddy soil group, which was characterized by a continu- ous summer crop and double- or triple-cropping systems of rice, and prevailed in the south and central areas of Anhui Province; Alopecurus aequalis Sobol. was the dominant weed in this group. Other main weeds in this group included Malachium aquaticum （L.） Fries, Stellaria alsine Grimm, Alopecurusjaponicus Steud., and Lapsana apogonoides Maxim. Thus, the weed community distributions in this group were described as the Alopecurus weed vegetation type. The paddy soil group could be divided into two subgroups, one southern and one central paddy soil subgroup. A strategy for integrated weed management is suggested according to the weed distribution pattern. The present study serves as a good example of how a quantitative research method was used to associate a visual estimate of weed infestation with multivariate analyses, such as PCA and CCA, and how this method can be applied to the study of weed vegetation on arable land.展开更多
Commelina species are plant resources full of promise as future food and feed that thrive in diverse ecosystems. They are medicinal plants, leafy vegetables, forage for ruminants, feed for cricket insects, crop protec...Commelina species are plant resources full of promise as future food and feed that thrive in diverse ecosystems. They are medicinal plants, leafy vegetables, forage for ruminants, feed for cricket insects, crop protection, and fuel. However, information regarding factors driving Commelina in agro-ecological zones in Western Kenya is lacking. Therefore, we investigated the diversity of Commelina species, the composition of associated weed species as well as environmental and management factors affecting their diversity and distribution based on 22 variables from 12 production sites. In the survey, 115 species belonging to 30 families were recorded of which 11 Commelina species were identified. Among Commelina species, Commelina diffusa and Commelina benghalensis var. benghalensis (non-hybrid variant) had higher relative density. Multiple linear regressions revealed that the environment (exchangeable sodium percentage, magnesium, soil pH, and total nitrogen) and management (agriculture system type) variables exert a stronger effect on the diversity of Commelina species. Detrended Correspondence Analysis detected different ecological conditions for Commelina species and the composition of associated weed species. The forward selection based on Canonical Correspondence Analysis indicated that the distribution of Commelina species responded significantly to soil pH, available phosphorous, total nitrogen, fertility, and crop spacing. Partitioning variation showed the great importance to the environment than management (10.57% versus 5.97%). The low shared variance (environment × management) was -0.4%, indicating that the two factors have a more individualistic than interactive nature. However, the 83.86% that remained unexplained was attributed to stochastic variation or unmeasured variables. This study suggests that the identified five important variables affecting the distribution of Commelina species will certainly contribute to the prioritization of ecological aspects leading to the growth condition of Commelina species.展开更多
文摘Two surveys were conducted to investigate weed vegetation in a 153-hm^2 sampling area of summer crop fields from Anhui Province, China, through visual scoring of the level of weed infestation compared with summer crops on a seven-class scale. In total, 155 sampling sites were selected in the field based on crops, tillage, rotation systems, geographical regions, and soil types across the province. Data on weed communities and environmental factors were collected and analyzed through principal component analysis （PCA） and canonical correspondence analysis （CCA）, and the output was interpreted ecologically. Results showed that the main factors influencing the structure and distribution of weed communities in summer crop fields were the soil submersion period, latitude, and soil type and pH. The CCA indicated a significant relationship between weed dominance and soil submersion duration, latitude, and soil pH. From the result of the PCA and CCA ordination, the 155 sampling sites could be divided into three groups based on geographic and floristic composition, as well as weed abundance. The southern dry land group, which was characterized by a double-cropping system in the hilly regions of southern and central Anhui Province with a continuous summer crop and an autumn dry land crop, was dominated by Galium aparine Linn. var. tenerum （Gren. et Godr） Robb., Avenafatua L., and Veronica persica Poir. The northern dry land group, which had the same cropping system as the southern dry land group, was dominated by G. aparine var. tenerum, Galium tricorne Stokes, Descurainia sophia （L.） Schur., and Lithospermum arvense L. in the North Anhui Province, China. These two dry land groups could be combined into one large dry land group, in which the Galium weed vegetation type dominated. The third group was the paddy soil group, which was characterized by a continu- ous summer crop and double- or triple-cropping systems of rice, and prevailed in the south and central areas of Anhui Province; Alopecurus aequalis Sobol. was the dominant weed in this group. Other main weeds in this group included Malachium aquaticum （L.） Fries, Stellaria alsine Grimm, Alopecurusjaponicus Steud., and Lapsana apogonoides Maxim. Thus, the weed community distributions in this group were described as the Alopecurus weed vegetation type. The paddy soil group could be divided into two subgroups, one southern and one central paddy soil subgroup. A strategy for integrated weed management is suggested according to the weed distribution pattern. The present study serves as a good example of how a quantitative research method was used to associate a visual estimate of weed infestation with multivariate analyses, such as PCA and CCA, and how this method can be applied to the study of weed vegetation on arable land.
文摘Commelina species are plant resources full of promise as future food and feed that thrive in diverse ecosystems. They are medicinal plants, leafy vegetables, forage for ruminants, feed for cricket insects, crop protection, and fuel. However, information regarding factors driving Commelina in agro-ecological zones in Western Kenya is lacking. Therefore, we investigated the diversity of Commelina species, the composition of associated weed species as well as environmental and management factors affecting their diversity and distribution based on 22 variables from 12 production sites. In the survey, 115 species belonging to 30 families were recorded of which 11 Commelina species were identified. Among Commelina species, Commelina diffusa and Commelina benghalensis var. benghalensis (non-hybrid variant) had higher relative density. Multiple linear regressions revealed that the environment (exchangeable sodium percentage, magnesium, soil pH, and total nitrogen) and management (agriculture system type) variables exert a stronger effect on the diversity of Commelina species. Detrended Correspondence Analysis detected different ecological conditions for Commelina species and the composition of associated weed species. The forward selection based on Canonical Correspondence Analysis indicated that the distribution of Commelina species responded significantly to soil pH, available phosphorous, total nitrogen, fertility, and crop spacing. Partitioning variation showed the great importance to the environment than management (10.57% versus 5.97%). The low shared variance (environment × management) was -0.4%, indicating that the two factors have a more individualistic than interactive nature. However, the 83.86% that remained unexplained was attributed to stochastic variation or unmeasured variables. This study suggests that the identified five important variables affecting the distribution of Commelina species will certainly contribute to the prioritization of ecological aspects leading to the growth condition of Commelina species.
