@article {50004, title = {Nitrogen limitation in arid-subhumid ecosystems: A meta-analysis of fertilization studies}, journal = {Journal of Arid Environments}, volume = {75}, year = {2011}, pages = {675-680}, abstract = {

Evidence supporting water limitation in arid-semiarid ecosystems includes strong correlations between aboveground net primary production (ANPP) and annual precipitation as well as results from experimental water additions. Similarly, there is evidence of N limitation on ANPP in low precipitation ecosystems, but is this a widespread phenomenon? Are all arid-semiarid ecosystems equally limited by nitrogen? Is the response of N fertilization modulated by water availability?

We conducted a meta-analysis of ANPP responses to N fertilization across arid to subhumid ecosystems to quantify N limitation, using the effect-size index R which is the ratio of ANPP in fertilized to control plots. Nitrogen addition increased ANPP across all studies by an average of 50\%, and nitrogen effects increased significantly (P\ =\ 0.03) along the 50{\textendash}650\ mm\ yr-1 precipitation gradient. The response ratio decreased with mean annual temperature in arid and semiarid ecosystems but was insensitive in subhumid systems. Sown pastures showed significant (P\ =\ 0.007) higher responses than natural ecosystems. Neither plant-life form nor chemical form of the applied fertilizer showed significant effects on the primary production response to N addition. Our results showed that nitrogen limitation is a widespread phenomenon in low-precipitation ecosystems and that its importance increases with annual precipitation from arid to subhumid regions. Both water and N availability limit primary production, probably at different times during the year; with frequency of N limitation increasing and frequency of water limitation decreasing as annual precipitation increases. Expected increase N deposition, which could be significant even in arid ecosystems, would increase aboveground net primary production in water-limited ecosystems that account for 40\% of the terrestrial surface.

}, keywords = {arid ecosystems, article, journal, meta-analysis, nitrogen fertilization, primary production, resource limitation}, doi = {10.1016/j.jaridenv.2011.03.003}, url = {files/bibliography/JRN00579.pdf}, author = {Laura Yahdjian and Laureano A. Gherardi and O. E. Sala} }