Friday, January 27, 2012
My Recent Project
Thursday, January 19, 2012
Some of "my" plants
Wednesday, January 11, 2012
Lianas?
About a year ago I took a trip to Costa Rica as part of a three-week plant systematics field trip with the University of Vermont. Lianas were present in nearly every forest type we explored. The word “liana” seemed exotic and their commonness was perhaps the most noticeable differences between northern temperate and tropical forests. Even the subtropical forests of southern Florida I became familiar with didn’t share such a pronounced abundance of these elegant climbing plants. I asked myself this question: Do northern temperate forest have lianas? The short answer is yes, but what follows here is the strange rabbit hole my mind traveled down in attempt to learn more. ( The picture on the left is a liana behind my uncle's house, the right is Bauhinia spp. in Costa Rica)
Google searches to a peer reviewed ecology papers will define lianas as a climbing woody vine. We definitely have these up north. As a kid I can remember swinging on big vines behind my uncle’s house, a place I visited recently. Although not as abundant, lianas exist in northern temperate forests. We know them as vines, which doesn’t sound as sexy.
In fact, there are about 215 liana species in the contiguous United States according to the USDA-NRCS (Londre and Schnitzer, 2006). The lianas behind my uncle’s house were likely of the genus Vitus, grapes, but other species I’ve regularly seen are Parthenocissus quinquefolia, Celastrus orbiculatus and Toxicodendron radicans (Virginia creeper, Oriental bittersweet and poison ivy). Liana studies done in northern forests almost always mention these species.
Apparently, one main reason why lianas don’t exist is such abundance in temperate forests is due to freezing xylems. However, a 0.94°C increase of average temperatures over the last 45 years in Wisconsin hasn’t increased liana abundance there (Londre and Schnitzer, 2006). However, in South Carolina, where increases in average temperatures could decrease the number of day below freezing per year, Allen at al’s 2007 study showed no convincing results that indicated increasing liana growth rates over a 12-year span.
According to Londre and Schnitzer (2006), we can expect to see more lianas along forest edges rather than interiors, which is what one might expect if they were in a tropical environment. Laurance et al (2001) did not observe higher liana abundances in fragmented area, but did find increases in diversity. Additionally, tropical forests being harvested have increased liana abundance and some by 40% in just 17 years (Schnitzer, 2011).
Lianas’ large canopies, high reproductive outputs (at the cost of structural support(Schnitzer and Bongers, 2002)) plus Zhu and Cao’s 2010 observation that lianas in South Western China have higher photosynthetic rates compared to trees of the same region, exemplify how lianas compete with trees for resources. Furthermore, underground competition for nutrients are thought to play a significant role in liana distributions and colonizations (Laurance et al 2001, Leight-Young et al, 2010), but are difficult to observe. Not only can they out compete trees for resources, but liana can climb up trees to steal their precious light!
There are many mechanisms employed by lianas to reach a forest canopy including, stem twining, clasping tendrils, thorns and spines, down-ward pointing hairs and adhesive adventitious roots (Schnitzer and Bongers, 2002). Leight-Young et al (2010), observed that the larger a tree’s diameter, the more root climbers were observed. Of course, tree architecture also plays a role in what kind of liana might colonize it.
Because of their ability to colonize disturbed areas there is concern about lianas suppressing forest regeneration by shading out plants important to succession. While having lower above ground biomasses than trees (lianas: 5-10%, trees: 90%), lianas can also slow tree growth. These factors: deforestation, colonization by lianas and decrease tree growth and regeneration suppression all decrease the amount of carbon being sequestered. Soil homogenization may also occur because of high foliar nitrogen and phosphorous as well as short leaf life-spans (Zhu and Cao 2010). Soil homogenization has the possibility of limiting growth of plants adapted to specialized soils (Schnitzer et al, 2011).
So, it would seem, from the information I’ve included, that lianas are bad. They take over light gaps, prevent other perhaps valuable trees from growing and regenerating the forest, decrease regeneration rates and facilitate soil homogenization. Lianas do provide structural diversity for forests, from which plant and animal life does benefit. They do contribute to biodiversity and may play an integral role in maintaining it because their ability to pull down trees and provide light gaps (Schnitzer et al, 2011).
Although this is my first foray into the world of existing liana research, it seems as though research does paint lianas in a negative light, despite acknowledgement of their cool ecology. Tropical inhabitants rely on their forest for income and sustenance. If lianas are portrayed as detriments to forests, it is possible their conservation may be neglected (despite their apparent increase in abundance, deforestation ultimately means less liana habitat). More research is likely needed into liana forest dynamics and their ecological role.
In my opinion, people are reluctant to change unless it has an economic benefit. By surveying ethnobotanical uses of lianas, results may garner support in effort for their conservation. For example, a survey conducted within a 1-ha plot of Amazonian Ecuador found 46 out of 98 liana species to have a use. The uses range from lamp fuel to music and construction material to edible material, and of course, ritualistic and medicinal uses. There is so much more to learn! I’ll end it here, but leave you with these questions in my head:
Is there a trend between lineage and liana climbing mechanism?
How are the different climbing mechanisms correlated to forest age, tree diameter and tree architecture?
Do lianas have host preferences and how do they range within a species?
Is there an ethnobotanical solution to liana conservation?
Works Cited:
Laurance, W.F., Perez-Salicrup, D., Delamonica, P.,Fearnside, P.M., D’Angelo, S., Jerozolinski, A., Pohl, L. and Lovejoy, T.E. 2001. Rain forest fragmentation and the structure of Amazonian liana communities. Ecology 82 (1): 105-116.
Leight-Young, S.A., Pavlovis, N.B., Frohnapple, K.J. and Grundel, R. 2010. Liana habitat and host preference in northern temperate forests. For. Ecol. And Management 260: 1467-1477.
Londre, R.S., and Schnitzer, S.A. 2006. The distribution of liana and their change in abundance in temperate forests over the past 45 years. Ecology 87(12):2973-2978.
Paz Y Mino C., G., Balslev, H. and Valencia, R. Useful liana of the Siona-Secoya Indians from Azmazonian Ecuador. Economic Botany 49 (3): 269-275.
Schnitzer, S.A. and Bongers, F. 2002. The ecology of lianas and their role in forests. Trends in Ecology and Evolutions 17 (5): 223-230.
Schnitzer, S.A., Bongers, F., and Wright, S.J. 2011. Community and ecosystem ramifications of increasing lianas in neotropical forest. Plant Signaling & Behavior 6:598-600.
Zhu, S. and Cao, K.F. 2010. Contrasting cost-benefit strategy between lianas and trees in a tropical seasonal rain forest in southwestern China. Oecologia 163: 591-599.
Sunday, January 1, 2012
Organic, Tree-hugging Vegetarians Save World!
Overview and thoughts on “Solutions for a cultivated plant” by, Foley et al 2011
As the human population continues to grow exponentially, Foley et al. (2011) demonstrate current agricultural methods are failing. Through analyses of geospatial data models, the authors explain these failures and define the state of current global agriculture. They suggest four key strategies to increase global food availability by 100 to 180%.
The first strategy aims to stop expansion of agricultural lands, which currently occupy 38% of Earth’s land mass not permanently covered by ice. Of that land, 3.38 billion is pastureland and 1.53 billion acres is cropland. Agricultural land has increased by 3% between 1985 and 2005 mostly at the cost of tropical forests, resulting in a decrease of biodiversity and increasing greenhouse gasses, while contributing little to global food demands. The authors argue that agricultural expansion would disrupt essential environmental processes facilitated by sensitive ecosystems.
Despite the 3% increase in agricultural land from 1985 to 2005, the 20% increase in crop production during that period resulted from higher crop yields. These yields are thought to have resulted from fewer areas in fallow, fewer crop failures and mutli-cropping practices. Estimated crop production could increase by 28% or 58% if crop yields were 75% and 95%, respectively. However, with more production per acre, crops may require more nutrients.
The third suggestion the authors extend is resource efficiency. Fertilizers cost money to produce, purchase and apply; Overuse wastes resources, has potential to pollute water and harm marine life. However, appropriate use and accessibility could increase productivity. Irrigation management coupled with use of plants best suited for environmental conditions can reduce water usage would also increase crop production.
Finally, the authors present a provoking, but simple way increase crop production: Feed humans crops that are currently grown for livestock or other purposes. Such a shift could increase crop production by 49%. However, areas unsuitable for crops could benefit in terms of calories from pastoral livestock. As it stands, 35% of cropland is devoted to fodder. In other terms, about 75% of agricultural land is directly used for animals. Creating ways to reduce post-harvest crop losses, over 40% in developing countries, would also increase available food quantities. It is interesting to know consumers and retailers of industrialized countries can waste over 40% of post-harvest crop.
The paper mentions 1 in 7 are malnourished, but doesn’t define the food deficit in terms of kilocalories, nor does it suggest how much crop production should have increase between 1985 and 2005 to feed the population. Because the food deficit isn’t known the conclusion of, “[increasing] global food production by 100-180% [and] meeting projected demands (Foley et al. 2011),” becomes slightly ambiguous. Only two ways to increase crop production were assigned percentages; a maximum of 49% from livestock conversion and 58% from higher crop yields, which doesn’t add up to 180%. Consequently, the readers must assume the remaining 73% increase is from a combination of other strategies mentioned in the paper but without values.
Throughout the paper the authors emphasize sustainable agricultural practices. Simple practices to increase production like mulching to reduce water loss, adopting some organic practices and providing better access to better crops were touted. None of the ideas presented to sustainably increase food production are necessarily new, but the authors consolidate them and support them with compelling global analyses. They acknowledge all four strategies must be used in concert to achieve their claimed increase in crop production. It is likely more collaborative efforts and ideas will be necessitated from shortfalls in global crop production. With sustainability creeping into the academic world, it will be interesting to see if integrative sciences test permaculture’s merits. From the evidence presented by Foley et al 2011, organic, tree-hugging vegetarians may be ahead of the global food crisis curve.
Foley, J.A., Ramankutty, N., Brauman, K.A., Cassidy, E.S., Gerber, J.S., Johnston, M. Mueller, N.D., O’Connell, C., Ray, D.K., West, P.C., Balzer, C., Bennett, E.M., Carpenter, S.R., Hill, J., Monfreda, C., Polasky, S., Sheehan, J., Siebert, S., Tilman, D. & Zaks, D.P.M. (2011). Solutions for a cultivated planet. Nature 478: 337-342.