| Overgrazing is the primary reason for grassland degradation and fencing is an important aid for restoration of degraded grasslands. Studying plant regrowth and reserves in response to fencing is a useful approach to understand the ecophysiological mechanisms of grassland degradation and restoration.This research was conducted in a Reaumuria soogorica - Cleistogenes songorica desert grassland in the Alax region of Inner Mongolia, China. Two plots, one fenced and one grazed were set up in both a lightly degraded and a heavily degraded area. Samples were collected from outside and inside the fence from May, July, and September in 2004 and 2005. Plant phenotypic changes were measured and nonstructural carbohydrate (including starch and soluble sugar) and total nitrogen in different parts of the plants were analyzed to assess plant physiological mechanisms for regrowth. The results showed that:1. Fencing resulted in increased plant height, biomass (leaf, total above ground, and root), together with canopy and individual tiller weight especially in the fenced, lightly degraded plots. As an example, the plant heights in September of both years were 2. 5 and 4 times greater compared with the grazed plots. Consistent with this, the above ground biomass in the fenced, lightly degraded plot was eight times (p<0. 05) more than that in grazed plot. However, in the heavily degraded plots, three years of fencing did not result in a significant effect on most indicators including biomass (leaf, above ground, root) and canopy. This indicates that fencing should be applied as soon as possible in degraded grasslands;otherwise, restoration will take a much longer time or is impossible.2. Nonstructural carbohydrates were mainly composed of starch which amounted to 12. 6% in terms of concentration in September;it was nearly twice that of water soluble carbohydrates. Reserves varied with season showed an initial decrease until July followed by a larger increase by September.3. In general, reserves within roots and stubble were greater in fenced plots than in grazed plots, and the differences were significant (p<0. 05) in lightly degraded plots. However, no consistency was found for the effect of fencing on nonstructural carbohydrates in leaves. The comparison between the two degraded plots showed that the concentration of nonstructural carbohydrates was lower in heavily degraded plots than that in lightly degraded ones. For example, starch concentration within stubble of lightlydegraded, fenced and grazed plots in Sep. 2005 were 12.6% respectively but were 8. 3% in heavy degraded plots.4. Leaves had the highest total nitrogen (TN) level followed by stubble and roots which only contained half to one fourth the total nitrogen of that in leaves. An increasing trend of leaf nitrogen content was observed from May to July followed by a decrease from July to September The corresponding changes in stubble and roots were much less.5. Fencing significantly affected the total nitrogen content of plants but the effect varied with grassland basic conditions. In the lightly degraded plots, the total nitrogen concentration of plants in the fenced plot was lower than that in the grazed plot, and the difference of leaves was significant in 2005. However, in heavily degraded plots the opposite trend was found, especially with the TN of roots in 2004. A comparison between the two degraded plots showed that the TN concentration of plants was higher in the heavily degraded plot than that in the lightly degraded one.6. In a whole, lightly degraded, fenced areas should be grazed but not before August. Heavily degraded areas need to continue to be fenced if recovery is to take place.
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