Home | Visiting Scholars Research | 2006 Annual Report

Research by a Visiting Scholar at CGREC
Range Plant Responses to Competition, Clipping, and Drought

Danjun Wang, with Janet Patton



Table of Contents

Background and Research Interests

Research and Other Experience at CGREC

Methods

Results

Summary



Background and Research Interests


Danjun Wang graduated from The Beijing Forestry University in 2003, majoring in Forestry, and is now continuing her schooling at the Institute of Botany, Chinese Academy of Science, for her master’s degree. Her research is focused on rangeland ecology, studying the effects of competition on community structure and the importance of grazing on the succession of plant species in the community. She is from Zhejiang Province, which is located in the southern part of the Yangtze River Delta on the southeast coast of China (see Map). Zhejiang is renowned for its picturesque landscapes, boasting well known features such as Yandang Mountain and the West Lake in Hangzhou. Zhejiang has subtropical temperatures and monsoon rains. With an average annual temperature of 60 to 64º F, it has 230-270 frost-free days and an average annual rainfall of 39 to 75 inches. It has long been known as “a land of fish and rice, home to silk, a paradise for tourists and a place of rich cultural heritage.” The permanent population of the province reached 49 million in 2006.

 

Research and Other Experience at CGREC


After one year of graduate level classroom study in China, Danjun came to Central Grasslands Research Extension Center (CGREC) in 2005 to conduct research for her master’s degree thesis. Last year (2005), she studied the grazing influence on five targeted plant species on the morphological and physiological level. This year her work has focused on a competition experiment with two of these species in a greenhouse.


During her two six-month stays at the CGREC, Danjun also assisted plant scientists at the Center. This work included collecting data, sampling forage production and utilization, identifying plant species, sampling density and basal cover of each plant species, sampling soil water using a neutron moisture meter, separating plant roots into fine root, rhizome, and coarse root, assisting in measuring root respiration under five temperatures, measuring photosynthesis using the Li-Cor 6400 portable photosynthesis system, and using a pressure chamber to detect plant moisture stress.

 

Danjun Wang monitoring her research at CGREC, summer 2006

Methods


Danjun’s research project began in June, using western wheatgrass (Agropyron smithii) and smooth brome (Bromus inermis) grown in the greenhouse under various treatments. The effects of water availability and clipping on both vegetative growth and competitive performance were evaluated.


The experimental design employed a randomized block design with four replications to test the effects of two factors: clipping heights and water levels on smooth brome and western wheatgrass. Both factors were applied at two treatment levels in a fully factorial combination. Clipping treatments were applied during July: a moderate treatment (cutting 50% of height from ground level to simulate grazing) and a control treatment (no cutting). The moderate treatment was regularly maintained by clipping the vegetation every two weeks. The clippings were weighed and added to the final harvest for total production for the treatment. The water levels were applied as drought (75% of rainfall based on the average daily precipitation rate) and control (100% of average rainfall), both at 3-day intervals. To study the effects of competition, seedlings of the two species were planted in several combinations. These included zero, one, two, three, or four plants of each species per pot up to a maximum of eight plants in each pot. In summary, the experiment was established using a factorial design: 2 water levels X 2 clipping levels X 5 densities of smooth brome X 5 densities of western wheatgrass. Shoots and roots were separated, dried, and weighed. Total biomass (above-ground and below-ground biomass) for each species was calculated.

 

Results

 

The summer was very hot, and temperatures in the greenhouse reached 132º F. To decrease the greenhouse temperature, shade cloths were put on the roof, the floor and roof were watered, and fans were added. These steps lowered the greenhouse temperature to 105 º F. Fortunately, enough of the seedlings survived to continue the experiment. After about four months, the preliminary results are as follows. Above-ground and below-ground biomass of western wheatgrass and smooth brome are significantly affected by the clipping and watering treatments, except for the watering treatment for above-ground biomass of smooth brome. Under the drought and clipping treatments, below-ground biomass of western wheatgrass is significantly higher with four plants than with one. In the meantime, under the drought and clipping regimes, the below-ground biomass of a single western wheatgrass plant is significantly lower than the below-ground biomass of the three other plant combinations. Under the no-clipping treatment, water availability did not change the western wheatgrass below-ground biomass significantly. Other parameters, such as conductance, photosynthetic rate, and plant moisture pressure and transpiration rate were all significantly changed because of water availability. Also, density had a significant effect on biomass production. For both species, the production of above-ground biomass and below-ground biomass reached the maximum under the three or four plant monoculture.

 

Summary

 

 

When the results of this research are completely analyzed, they will help us understand how individual species and a combination of species react to varying amounts of available soil water and grazing. To achieve the maximum biomass production, a specific level of soil water and grazing intensity along with an appropriate management scenario will be required. For example, we can know which species combination will provide maximum production in a particular rainfall zone, whether in North Dakota or China. This information will help producers manage the land for sustainability and maximum profit. A final report will be available on CGREC’s website, www.ag.ndsu.nodak.edu/streeter/.


NDSU Central Grasslands Research Extension Center
HomeVisiting Scholars Research | 2006 Annual Report