Our new article “Vegetation restoration in Northern China: A contrasted picture“ was just published in Land Degradation and Development. Lead author Feng Wang was a visiting professor in the Caylor Lab at Princeton for a year back in 2014 and we have been collaborating since then. See the abstract below for a quick overview of the study and results or head over to Land Degradation and Development’s website to read the full paper.
China started a long-term effort to mitigate desertification and ensure the sustainability of its environment by implementing multiple large-scale national ecological restoration projects since 1978, but their success has been highly debated for a long time. Here, we estimated the change of vegetation fraction cover (VFC) in the Three‐North Shelterbelt Programme (TNSP) region over the past three decades on the basis of the Normalized Difference Vegetation Index dataset from the Global Inventory Monitoring and Modeling System. We evaluate the national strategy of vegetation restoration in North China by comparing rainfall patterns, vegetation change, and national ecological restoration programs on the basis of the Global Meteorological Forcing Dataset and the China Forestry Statistical Yearbooks. We find that the western, central, and eastern parts of the TNSP region exhibited a distinct increase in vegetation coverage. The western region had the highest increase in annual precipitation, but this did not result in the highest VFC increase. We infer that ecological restoration activities are the factor leading to the observed increase in VFC in the eastern and central region compared with the western region. The low survival rate of planted trees in the forest of the TNSP region indicates that it is necessary to improve the mode of vegetation restoration to obtain optimal returns and avoid excessive investment. The success of new strategies, for example, natural restoration and quasi-natural afforestation are promising as an alternative method. China’s experiences in reforestation will be very beneficial for other countries to promote land degradation mitigation and vegetation improvement in the arid and semiarid areas.
Over the past few months, I have been busy with conferences and talks, starting with a talk at the AGU Fall Meeting in Washington DC on my work using CYGNSS to look at rainfall interception. In January, I visited Caltech for the CYGNSS Science Team meeting. I went on to give a talk for the Environmental Engineering and Water Resources Seminar Series in the CEE department here at the University of Michigan. Finally, I gave a guest lecture for the Environmental Science Seminar at Iowa State University, hosted by Pr. Brian Hornbuckle.
Recently, the Green Life Sciences Symposium I presented at in September 2018 uploaded all the presentations to Youtube. You can see my talk below, or follow this link to see the rest of the presentations.
I have been representing the AGU Ecohydrology Technical Committee to organize a large event at the upcoming AGU Fall Meeting. Geared towards early-career and students, the event will include awesome panelists (the Ecohydrology panelist will be the amazing Holly Barnard), free food, and 200 people looking to chat and connect. Join us!
Last week, I attended the Green Life Sciences Symposium organized by the Green Life Sciences Initiative at the University of Michigan. The two-day symposium brought together plant scientists from all over the US and a few international places. I gave a talk on my recent paper looking at the effects of dew deposition on leaf transpiration using stable isotopes. For me, it was especially great to connect with plant scientists at the University of Michigan that I had not had a chance to interact with yet. The organizers also worked really hard to ensure that women and POC were represented, and we got to see multiple talks by inspiring women in the field, including Johanna Schmitt, Beronda Montgomery, and Deborah Goldberg.
Inspired by the AGU Centennial Celebration and how ecohydrology has grown in the last 100 years, the AGU Ecohydrology Technical Committee I am part of has been adding a “leaf” to the ecohydrology tree week-by-week by introducing a new ecohydrologist every week and how their experiences helped shape the perspective they contribute.
I was featured this week and answered a few questions on my vision of the field. Head over to the AGU Ecohydrology website to check it out!
Foliar uptake of water from the surface of leaves is common when rainfall is scarce and non-meteoric water such as dew or fog is more abundant. However, many species in more mesic environments have hydrophobic leaves that do not allow the plant to uptake water. Unlike foliar uptake, all species can benefit from dew- or fog-induced transpiration suppression, but despite its ubiquity, transpiration suppression has so far never been quantified. Here, we investigate the effect of dew-induced transpiration suppression on the water balance and the isotope composition of leaves via a series of experiments. Characteristically, hydrophobic leaves of a tropical plant, Colocasia esculenta, are misted with isotopically enriched water to reproduce dew deposition. This species does not uptake water from the surface of its leaves. We measure leaf water isotopes and water potential and find that misted leaves exhibit a higher water potential and a more depleted water isotope composition than dry leaves, suggesting a ∼30% decrease in transpiration rate compared to control leaves. We propose three possible mechanisms governing the interaction of water droplets with leaf energy balance: increase in albedo from the presence of dew droplets, decrease in leaf temperature from the evaporation of dew, and local decrease in vapor pressure deficit. Comparing previous studies on foliar uptake to our results, we conclude that transpiration suppression has an effect of similar amplitude, yet opposite sign to foliar uptake on leaf water isotopes.
Dew deposition occurs in ecosystems worldwide, even in the driest deserts and in times of drought. Although some species absorb dew water directly via foliar uptake, a ubiquitous effect of dew on plant water balance is the interference of dew droplets with the leaf energy balance, which increases leaf albedo and emissivity and decreases leaf temperature through dew evaporation. Dew deposition frequency and amount are expected to be affected by changing environmental conditions, with unknown consequences for plant water stress and ecosystem carbon, water and energy fluxes. Here we present a simple leaf energy balance that characterizes the effect of deposition and the evaporation of dew on leaf energy balance, transpiration, and carbon uptake. The model is driven by five common meteorological variables and shows very good agreement with leaf wetness sensor data from the Blue Oak Ranch Reserve in California. We explore the tradeoffs between energy, water, and carbon balances for leaves of different sizes across a range of relative humidity, wind speed, and air temperature conditions. Our results show significant water savings from transpiration suppression up to 25% for leaf characteristic lengths of 50 cm. CO2 assimilation is decreased by up to 12% by the presence of dew, except for bigger leaves in windspeed conditions below 1 m s−1 when an increase in assimilation is expected.
The MUSE conference is a large-scale version of these workshops, bringing people from across the University of Michigan to present their research during a two-day event. I chaired the session on Land Use and Land Cover Change on Thursday morning and presented my own results from using solar-induced fluorescence to map reforestation in China.
It was a fun occasion to meet students, postdocs, and faculty from a range of departments, from English to Psychology, and Mechanical Engineering to the School of Public Health, and I hope that some of the contacts made at the conference will eventually turn into long-term collaborations.
This year, the AGU Fall Meeting moved from its traditional location in San Francisco to New Orleans. As usual, the meeting was a wonderful occasion to catch up with former classmates and colleagues, and hear about all the new science!
Finally, I had the opportunity to attend the Ecohydrology Technical Committee and to help out with the Hydrology Business Meeting. Both events were great opportunities to meet new people in my field, and I’m hoping to get more and more involved with the hydrology community at AGU in the future.
A new paper entitled ‘Advancing ecohydrology in the changing tropics: Perspectives from early career scientists‘ just appeared in Ecohydrology today. The article is a student-lead paper focusing on current and future threats faced by tropical ecosystems, and what the potential research gaps that would help the scientific community better understand and mitigate some of these threats.
The article stemmed out of the AGU Chapman conference on tropical ecohydrology that I attended in June 2016. All the co-authors of the article are graduate students and early-career scientists from institutions around the world, and it was both a lot a fun and a great learning experience to write this together! You can see the article on the Ecohydrology website HERE.
Tropical ecosystems offer a unique setting for understanding ecohydrological processes, but to date, such investigations have been limited. The purpose of this paper is to highlight the importance of studying these processes—specifically, how they are being affected by the transformative changes taking place in the tropics—and to offer an agenda for future research. At present, the ongoing loss of native ecosystems is largely due to agricultural expansion, but parallel processes of afforestation are also taking place, leading to shifts in ecohydrological fluxes. Similarly, shifts in water availability due to climate change will affect both water and carbon fluxes in tropical ecosystems. A number of methods exist that can help us better understand how changes in land use and climate affect ecohydrological processes; these include stable isotopes, remote sensing, and process-based models. Still, our knowledge of the underlying physical mechanisms, especially those that determine the effects of scale on ecosystem processes, remains incomplete. We assert that development of a knowledge base concerning the effects of transformative change on ecological, hydrological, and biogeochemical processes at different spatio-temporal scales is an urgent need for tropical regions and should serve as a compass for emerging ecohydrologists. To reach this goal, we advocate a research agenda that expands the number and diversity of ecosystems targeted for ecohydrological investigations and connects researchers across the tropics. We believe that the use of big data and open source software—already an important integrative tool/skill for the young ecohydrologist — will be key in expanding research capabilities.