Nucleário, cardboard, or manual crowning: which maintenance technique is most cost-effective in tree seedling survival establishment?

In ecological restoration, one of the main challenges is to develop new methods, techniques, and incentives that both favour and reduce maintenance costs in restoration projects. Besides, post-planting maintenance is often neglected hampering seedling survival over time owing to alien grasses, which compete strongly with native plants for resources. To solve these issues, recently, an innovative technology called Nucleário has been developed in Brazil. Aiming to hinder alien competition filters, the Nucleário also attempts to condition a better microenvironment, reducing drought stress through the water storage tank, decreasing temperatures, which facilitates the survival and growth of seedlings in areas under restoration. Another method used to decrease alien grasses, which is inexpensive, is seedling crowning using cardboard lowing maintenance needs in restored areas. Cardboard has similar functions to Nucleário, such as protecting soil against loss of water and nutrients and reducing competition with invasive exotic grasses. Therefore, comparing them also with traditional manual weeding (i.e., clean-weeded crown by hoe), we aimed to verify which technique is most cost-efficient for seedling crown maintenance of Dipteryx alata Vog., which is an indigenous tree species with high economic value owing to its nuts. We tested three techniques in areas under restoration in the Cerrado, in the Environmental Protection Area "Córrego Guariroba" located in Campo Grande, Mato Grosso do Sul, Brazil. We monitored seedlings submitted to the three methods in the wet and the dry periods for biotic (competition with exotic grasses, herbivory, and growth) and abiotic (moisture and soil temperature) indicators. We observed that the Nucleário was the treatment that maintained the highest soil moisture, resulting in a larger canopy area. However, these effects do not reflect increases in the survival rate, diameter, and height of the seedlings. None of the treatments was effective in reducing herbivory. Nucleário was the most effective treatment in reducing the competition of seedlings with invasive grasses. Cardboard presented an implementation value 21.5 times lower than Nucleário and 1.2 times than manual crowning. Given the high purchase price, the Nucleário's cost-benefit ratio was very high compared to the crowning of cardboard and the manual weeding, which discourages us from recommending it for this species with high survival rates. Its project can be revised to decrease herbivory rates, as well as its efficiency tested in the short and long term in different ecosystems and species, particularly species susceptible to water stress.

Which spatial arrangement of green manure is able to reduce herbivory and invasion of exotic grasses in native species?

The practice of using green manure for ecological restoration has grown so significantly that there is a shortage of seeds for purchase on the market. Nonetheless, there is very little literature available demonstrating the effects and benefits commonly cited for green manure for addressing important environmental filters, such as herbivory and invasive grasses. Our objective is to determine which spatial sowing arrangement including green manure promotes the lowest rates of herbivory on native species and decreases cover by invasive grasses in ecological restoration. We experimentally tested three sowing configurations of green manure intercropping with native species: T1 the lowest herbivoy rate for both native and green manure, mixture of native and green manure species in the same row, T2, alternating rows of green manure and native species, and T3, rows of native species intercropped with a 2 m wide strip of green manure. We found that (1) green manure species experience greater damage from herbivory than do native species, with average values ranging from 1.8 times higher values in green manure than natives in T1, 2.9 times in T2, and 2.7 times in T3 (when sown in rows and in broader strips, green manure and native species attract more herbivorous insects than if they were sown together [muvuca]); and (2) when green manure and native species are planted mixed in the same row they produce greater soil cover, and thus limit invasion by undesired species. The use of green manure has been identified as an alternative method for overcoming the environmental filters of herbivory and invasive grasses in restoration areas. Considering the demand for information that supports the use of green manure for purposes of ecological restoration, the novel results of the present study fill a void and should prove to be of great interest to researchers and practitioners. In addition, the presented results provide information on efficient and low-cost restoration techniques that are necessary for the activity to gain scale, enabling countries to meet the large restoration targets.