Bringing new life to degraded forests in Madagascar
Researchers in the School of Plant and Environmental Sciences worked with international partners to protect and restore forests in Madagascar by testing shade structures, species, and soil amendments.
Madagascar contains 5 percent of the world’s known plants and animals, and 80 percent of those are only found on the island nation that is located off the coast of East Africa. But deforestation is threatening the nation’s biodiversity due to the fact that more than 40 percent of its forests have been cleared over the past 70 years. To address the problem, the government has committed to restoring 4 million hectares — more than 9.8 million acres — by 2030.
In order to help with these efforts, a team of Virginia Tech researchers in the College of Agriculture and Life Sciences explored techniques to improve plantings during eastern Madagascar’s dry season.
The project was led by undergraduate student Chris Logan and Leighton Reid, assistant professor in the School of Plant and Environmental Sciences, in partnership with nonprofit Green Again Madagascar.
“This project is a great example of collaboration between ecologists and practitioners to solve a bottleneck problem in tropical forest restoration,” Reid said.
The team of researchers worked at Parc Ivoloima, a forestry station and zoological park near Toamasina, where the dry season runs from August to December and a cyclone season from January to March.
They found that selecting the proper tree species and reducing transplant shock by using rustic shade structures from materials that are readily available is important to ensure long-term success. While more permanent wooden structures could be used, they are not readily available and are cost prohibitive for Malagasy farmers, as many typically earn less than $2 a day.
From October 2014 to January 2015, 369 seedlings that represent 17 native tree species were planted. Most of the seedlings were 4 to 8 inches tall.
They used a circular planting design with a central tree seedling surrounded by a ring of eight seedlings, separated by about 6 feet.
Controls, which did not receive soil amendments, watering, or shade, were planted in the center. The eight surrounding seedlings received shading with four fronds of a ruderal fern.
(From left) Chris Logan, Eva Colberg and Marcellin Velo inspect four-year old Parkia madagascariensis trees that survived a wildfire near Amoratandrazana. Photo by Leighton Reid.
The fronds were placed in a cone shape to allow temporary shade without inhibiting growth. The practice is regularly used by Malagasy farmers. The researchers noted a 75 percent reduction in transplant shock, suggesting that intense solar radiation is a primary limitation on initial establishment of dry season plantings.
"It's good to test these techniques. In the countryside, farmers don't test very many things and just do the things they know or what people have done before,” said Marcellin Velo, chief operating officer of Green Again Madagascar.
The team also focused on soil amendments and watering strategies.
Half of the shaded seedlings were soaked in buckets of creek water prior to planting. The other half were planted with only the moisture from their last watering at the nursery.
For soil amendments, half of the shaded seedlings were planted in a hole 33 percent filled with nutrient-rich compost. To help with moisture retention, the other four were filled with one of three locally available absorbent materials: moss, coconut husk or chopped petioles of traveler’s palm.
Seedling survival and height were measured after one to eight weeks, one year, and six years after planting.
More than 98 percent of all seedlings survived initial transplant, falling to 83 percent after one year and 41 percent after six years.
The team did not find evidence that soil amendments or watering decreased tree mortality in the first few months, but absorbent materials were associated with a slight decrease in the survival rate after one year.
Researchers observed species provided the greatest variation in seedling survival. After one year, Uapaca sp. had a survival rate of 100 percent compared to Delonix regia with a survival rate of 44 percent.
Survival rates were more erratic after several years as some successful short-lived varieties died. One example is Trema orientialis, which had a zero percent survival rate after six years following a 95 percent rate after one year.
The team recommends using short-lived, high growth species during the dry season. Those producing favorable results in this study include Uapaca sp., Trema orientalis, Psiadia sp., Macaranga sp., and Pittosporum ochrosiifolium.
“The findings from this experiment exemplify how forest restoration, using approaches from local farmers, is a practical and useful way to orient restoration plantings in Madagascar,” Logan said. “It’s very possible that other restoration applications can be found using their knowledge.”