Ground level photosynthetically active radiation dynamics in stands of Acacia mearnsii De Wild

Abstract

The objective is to study the dynamics of photosynthetic radiation reaching the soil surface in stands of Acacia mearnsii De Wild and its influence on height growth in stands. This fact gives rise to the formulation of the following hypothesis for this study: "The reduction of the incidence of light inside the stand of black wattle will cause the inflection point in its height growth when this reaches 4 to 5 m in height, i.e. when the stand is between 2 and 3 years of age". The study was conducted in stands in the state of Rio Grande do Sul, Brazil, where diameters at breast height, total height and photosynthetically active radiation available at ground level were measured. The frequency tended to be more intense when the age of the stands increases. It was evident that a reduction of light incidence inside the forest occurred, caused by canopy closure. Consequently, closed canopy propitiated the competition of plants. This has affected the conditions for growth in diameter and height of this species, reason why it becomes possible to conceive the occurrence of an inflection point in the growth of these two variables, confirming the formulated hypothesis.

Dynamics of solar radiation and soybean yield in agroforestry systems

“…Similar results those obtained in this study were reported by Almeida et al (2015). Péllico Netto et al (2015), evaluating the dynamics of solar radiation in the understory of Acacia mearnsii, in an experiment conducted in Southern Brazil, have concluded that in the center of the plot, i.e., between rows of trees, more than 70% of the radiation reaches the ground level; however, in the projection and closure of the canopy, the values were significantly reduced to only 20%; confirming the influence of the canopy trees in the interception of incident radiation and thus reducing the availability of radiation for understory crops. Our findings agree with a study carried out by Pezzopane et al (2015) and Bosi et al (2014) who reported the high relation between levels of incident solar radiation, and its effect on microclimate, growth characteristics of plants, and soil moisture.…”

“…This is especially relevant in areas which include trees, given their continued growth in height, crown projection, and leaf area index, which can modify the distribution of existing resources (Muller et al 2014), and in particular solar radiation (Elli et al 2016). The fraction of solar radiation transmitted through the canopy, available to plants within the understory, can present a direct or diffuse form, which determines the internal microclimate of the system (Pezzopane et al 2015, Péllico Netto et al 2015.…”

Plant growth, radiation use efficiency and yield of sugarcane cultivated in agroforestry systems: An alternative for threatened ecosystems

“…It can be inferred that independent of the cropping system, the k values depend primarily on the LAI, which determines the amount of solar radiation available in the understory of sugarcane. According to Behling et al (2015), this condition is understandable since light attenuation of the plant canopy is determined by leaf density (which can be expressed by LAI) and also by the geometric characteristics of the leaves and the tree canopy, as well as the optical properties of the leaves. Thornley (1976) reported that the value of k may vary with leaf traits, sun angle, spacing, and latitude.…”

Conversion Efficiency of Photosynthetically Active Radiation Into Acacia mearnsii Biomass

“…Solar radiation, when intercepted by a crop, plays a fundamental role in the environment, and the available energy balance is associated with biomass production (Monteith & Moss, 1977). The amount of radiation available for plants is a function of several factors, including physiological and morphological characteristics, such as growth pattern, leaf angle and leaf position (Netto et al, 2015).…”