Effects of Canopy Closure on Photosynthetic Characteristics of Ilex latifolia Thunb.in Phyllostachys pubescens Forests

Plantation under the forest is a good way of agroforestry,but the canopy closure has a great influence on understory herbs’growth.In the study,different canopy closures of Phyllostachys pubescens forests were set up to explore its influence on the growth of Ilex latifolia Thunb.The photosynthetic characteristics of Ilex latifolia leaves under different canopy closures were determined by Li-6400 portable photosynthetic system.The results showed that the net photosynthetic rate curve of Ilex latifolia leaves of T1(canopy closure of 0.56)was bimodal with an obvious"midday depression"phenomenon,while the net photosynthetic rate curves of T2(canopy closure of 0.72)and T3(canopy closure of 0.86)were unimodal.The results of light response curve showed that the photosynthetically active radiation and transpiration rate reduced with the increasing of canopy closures.The photosynthetically active radiation,transpiration rate,stomatal conductance,and net photosynthetic rate of Ilex latifolia leaves of T2 were higher than those of T3.Although the net photosynthetic rate of T2 was lower than that of T1,it had no obvious photo-inhibition which affected plant growth.Overall,the canopy closure of 0.72 was more suitable for the growth of Ilex latifolia.The herb plantation in the bamboo forest should be considered with the canopy closure for a better growth.

Developing a dynamic growth model for teak plantations in India

Background： Tectono grandis （teak） is one of the most important tropical timber species occurring naturally in India. Appropriate growth models, based on advanced modeling techniques, are not available but are necessary for the successful management of teak stands in the country. Long-term forest planning requires mathematical models and the principles of Dynamical System Theory provide a solid foundation for these. Methods： The state-space approach makes it possible to accommodate disturbances and avarying environment. In this paper, an attempt has been made to develop a dynamic growth model based on the limited data, consisting of three annual measurements, collected from 22 teak sample plots in Karnataka, Southern India. Results： A biologically consistent whole-stand growth model has been presented which uses the state-space approach for modelling rates of change of three state-variables viz., dominant height, stems per hectare and stand basal area. Moreover, the model includes a stand volume equation as an output function to estimate this variable at any point in time. Transition functions were fitted separately and simultaneously. Moreover, a continuous autoregressive error structure is also included in the modelling process. For fitting volume equation, generalized method of moments was used to get efficient parameter estimates under heteroscedastic conditions. Conclusions： A simple model containing few free parameters performed well and is particularly well suited to situations where available data is scarce.

Root Plate Growth in Sunflower and Its Relevance to Sclerotinia Basal Stalk Rot

Sclerotinia basal stalk rot (BSR) of sunflower (Helianthus annuus L.) is a fungal disease of the roots that causes symptoms of wilt and a basal stem lesion. Evaluating root plate growth could improve our understanding of BSR. Separate studies were conducted to determine the effect of sunflower growth stage or genotype on root plate diameter in North American environments. Root plate diameter of cultivated hybrids at reproductive growth stages was 3 to 4 times larger than vegetative stages. Cultivated hybrids had larger root plate diameter than interspecific lines. These results have implications for artificial inoculation methods that evaluate genotypes for BSR resistance in the field or greenhouse. Disease escapes can occur if field-grown plants are inoculated too far from the root plate and/or too early at vegetative growth stages. Side-dressing mycelium-infested cereal grain closer (i.e., 10 cm) to plants at reproductive growth stages (i.e., R1 - R4) can increase disease pressure and reduce disease escapes. These guidelines for the field can be used to validate results from artificial inoculations in the greenhouse.