title: Photosynthetic Response of Soybean to Microclimate in 26-Year-Old Tree-Based Intercropping Systems in Southern Ontario, Canada.
abstract: In order to study the effect of light competition and microclimatic modifications on the net assimilation (NA), growth and yield of soybean (Glycine max L.) as an understory crop, three 26-year-old soybean-tree (Acer saccharinum Marsh., Populus deltoides X nigra, Juglans nigra L.) intercropping systems were examined. Tree competition reduced photosynthetically active radiation (PAR) incident on soybeans and reduced net assimilation, growth and yield of soybean. Soil moisture of 20 cm depth close (< 3 m) to the tree rows was also reduced. Correlation analysis showed that NA and soil water content were highly correlated with growth and yield of soybean. When compared with the monoculture soybean system, the relative humidity (RH) of the poplar-soybean, silver maple-soybean, and black walnut-soybean intercropped systems was increased by 7.1%, 8.0% and 5.9%, soil water content was reduced by 37.8%, 26.3% and 30.9%, ambient temperature was reduced by 1.3°C, 1.4°C and 1.0°C, PAR was reduced by 53.6%, 57.9% and 39.9%, and air CO2 concentration was reduced by 3.7μmol·mol(-1), 4.2μmol·mol(-1) and 2.8μmol·mol(-1), respectively. Compared to the monoculture, the average NA of soybean in poplar, maple and walnut treatments was also reduced by 53.1%, 67.5% and 46.5%, respectively. Multivariate stepwise regression analysis showed that PAR, ambient temperature and CO2 concentration were the dominant factors influencing net photosynthetic rate.
authors.affiliation: Department of Biological and Medical Engineering, Shangluo University, Shangluo, Shaanxi, China; School of Environmental Sciences, University of Guelph, Guelph, Ontario, Canada.
authors.forename: Xiaobang
authors.initials: X
authors.lastname: Peng
authors.affiliation: School of Environmental Sciences, University of Guelph, Guelph, Ontario, Canada.
authors.forename: Naresh V
authors.initials: NV
authors.lastname: Thevathasan
authors.affiliation: School of Environmental Sciences, University of Guelph, Guelph, Ontario, Canada.
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Gordon
authors.affiliation: School of Environmental Sciences, University of Guelph, Guelph, Ontario, Canada.
authors.forename: Idris
authors.initials: I
authors.lastname: Mohammed
authors.affiliation: College of Forestry, Northwest A&F University, Yangling, Shaanxi, China.
authors.forename: Pengxiang
authors.initials: P
authors.lastname: Gao
mesh_terms: D031002:Acer / Q000254:growth & development; D000383:Agriculture / Q000379:methods*; D002940:Circadian Rhythm / Q000502:physiology; D018556:Crops, Agricultural / Q000254:growth & development*; D031324:Juglans / Q000254:growth & development; D008834:Microclimate; D009864:Ontario; D010788:Photosynthesis; D012044:Regression Analysis; D013025:Glycine max / Q000502:physiology*; D014197:Trees / Q000254:growth & development*