Studying cave plants in SW China

Yangtse cave, Fengshan County, Guangxi, type locality for eight species of plant. The plant-bearing part of the cave is ca 170 m deep and 70 m wide (note the person for scale)

As part of my research on the nettle family, Urticaceae I became aware of plants growing in the entrance caverns of caves several years ago and for over a year now my collaborators at the Guangxi Institute of Botany, China lead by Professor Yigang Wei and I have been working on documenting the full diversity of this unusual flora. This lead us to think about whether these plants may have become adapted to life in caves, in particular the relatively constant climate and low light. Especially for species which grow amongst the lowest light levels at the back of caverns where they are growing in a fraction of the light they could be expected to receive in a forest. We therefore applied for a grant from the Guangxi Key Laboratory of Plant Conservation and Restoration Ecology in Karst Terrain, and the Foreign Experts Bureau to undertake some preliminary work to document the climate, light and photosynthesis of the plants in the caves.

Fu Longfei and Chen Xiaoqin taking photosynthesis measurements using an instrument called a handheld PAM which uses fluorescence to measure various aspects of photosynthesis.

We selected the Yangtse cave as we know the diversity of plants that grow there (ten species of nettle alone), we have three data-loggers recording temperature and humidity in it and it is close to a town where we can spend the night. It is also a spectacular and beautiful place to spend several days working. The aim of our work was to collect the data necessary to test the hypothesis that the plants growing within the entrance cavern of the Yangtse cave exhibit different photosynthetic performance than the same or congeneric species growing outside of the cave. To do this we randomly selected individuals of three species of nettle in the genus Elatostema, one species of Begonia and a species of fern at four different locations in the cave, the back, midway into the entrance cavern, at the entrance and outside of the cave. We also brought two species of Elatostema from the living collection at the Guangxi Institute of Botany to compare their photosynthesis performance with members of the same species that had grown up within the cave. This was to get some indication as to how plastic their response was.

Elatostema obscurinervium, one of 31 species known only from caves and recently collected from a cave in northern Vietnam.

Each plant was connected to a hand-held PAM chlorophyll fluorometer, an incredibly sensitive device that can measure several key outputs of photosynthetic reactions in the chloroplasts as they take place. By comparing our study plants to those growing outside of the cave and from the scientific literature we hope to see whether cave-dwelling plants differ from non-cave plants in some of those parameters, and whether those differences are dependent upon what kind of plant they are. These parameters include the efficiency of photosynthesis, that is how much of the light energy is harnessed by the photosynthetic reactions, how much is dissipated and how resilient the photosynthetic apparatus is to changing light intensity. If we find  a difference between cave and non-cave dwelling plants then taken together these measurements can provide some indication of which group of photosynthetic reactions are leading to these differences.

Reforestation in Haiti, the value of botanical knowledge

Sadhana Forest Haiti staff and volunteers planting Brosimum alicastrum seedlings in the compound of an Anse-a-Pitre smallholder

Haiti is infamous for extensive deforestation, less tha 4% of its original forest cover remains, which in addition to threatening many of its endemic trees with extinction has also increased the destructive impact of natural disasters of which there have been several in the last couple of decades. Deforestation is widely recognized as a significant threat to the well-being and security of Haitians and as a consequence many projects have been set up to plant trees, some more successful than others. Probably the biggest challenge to reforestation is to ensure that the communities involved are engaged and that they feel that the benefits of protecting and looking after a tree outweigh the sacrifice involved in not converting it to charcoal for cooking. Charcoal is the main fuel in rural areas and demand for it is high, a small bucket costing up to US$2 leading people to burn cacti to produce it. One NGO which seems to have been successful in engaging rural communities to grow and protect useful tree species has been Sadhana Forest Haiti

5 litre containers of charcoal can be found at most local shops. Charcoal is produced from local trees and represents the main source of fuel for cooking and so essential.

One of the difficulties for NGOs reforesting in any country is access to the scientific information necessary to make choices about what is grown: will a species grow in the chosen sites? How quickly will it grow? Will local people recognise it as a species of value to be protected? Will it support livelihoods? Where can seed be obtained from? How does it germinate? Is it native? What is its conservation value? This information can be tricky to get hold of, especially in countries with little botanical capacity or knowledge repositories. Often the result is that the species selected are those for which seed can be obtained and that are very well known to be of livelihood value, normally non-native species such as avocado, mango, eucalyptus of little conservation or biodiversity value but highly recognizable. Some native and especially endemic species for which knowledge of livelihood value is likely to be restricted to older members of a community or a small number of botanists and whose propagation and germination requirements are less well known will be harder for NGOs to incorporate.

Sadhana’s community liaison officer, Nixon Casseus, discussing fruiting of a 4 year-old Brosimum alicastrum with the owner of a small-holding who has been looking after the tree

RBG Kew has been working in neighboring Dominincan Republic for several years and has developed a strong relationship with the Dr. Rafael Moscoso National Botanical Garden, an institution with an active botanical community and seed bank. This represents an opportunity to share some of the knowledge and expertise on additional potential native plants with Sadhana Forest and the households that they work with. To this end I spent a few days visiting Sadhana Forest Haiti and some of the households. I was struck with the commitment and planning behind Sadhana Forest, who with few resources have provided several thousand seedlings to thousands of households in a region spanning Haiti’s south eastern border with the Dominican Republic. Hopefully, in collaboration with the Dr. Rafael Moscoso National Botanical Garden and Kew we will be able to introduce more native species of livelihood value to be planted in the future.

The Sadhana Forest compound at Anse-a-Pitre, Haiti.