A Col­lec­tion of News by Moos


Cli­mate change will affect moun­tain ecosys­tems globally

pub­lished 29 Jan­u­ary 2017 | mod­i­fied 29 Jan­u­ary 2017

Treeline vegetationThe cli­mate warm­ing that is expected to occur over the next 80 years may greatly dis­rupt moun­tain ecosys­tems. This con­clu­sion is pre­sented by an inter­na­tional research team in a new study in the jour­nal Nature. In seven moun­tain­ous areas around the world they com­pared veg­e­ta­tion, nutri­ent avail­abil­ity and soil con­di­tions at dif­fer­ent alti­tudes – cor­re­spond­ing to dif­fer­ent tem­per­a­ture zones — and could thereby pre­dict how a warmer cli­mate would affect moun­tain ecosys­tems. Their results are pub­lished on 25 Jan­u­ary in Nature.

Moun­tain ecosys­tems world­wide are highly vul­ner­a­ble to human-​induced cli­mate warm­ing. This is char­ac­ter­ized both by the move­ment of tree lines, and by changes in veg­e­ta­tion that are inde­pen­dent of tree line shifts. Many exper­i­ments have been per­formed to try to under­stand how cli­mate warm­ing affects moun­tain ecosys­tems, but these are ham­pered because climate-​driven effects occur over a much longer time frame than the dura­tion of any exist­ing exper­i­ment, and because most exper­i­ments are not well suited to study responses of large, long lived plants such as trees. As such our knowl­edge of how cli­mate warm­ing may affect moun­tain ecosys­tems glob­ally remains limited.

The exper­i­ments
The recent arti­cle, coor­di­nated by post­doc­toral researcher Jor­dan Mayor and pro­fes­sor David War­dle (both with the Depart­ment of For­est Ecol­ogy and Man­age­ment at Sveriges lant­bruk­suni­ver­sitet (SLU)), and coau­thored by researchers in nine other insti­tu­tions, sheds new light on how cli­mate warm­ing may affect moun­tain ecosys­tems glob­ally. Rather than uti­lize short term exper­i­ments, the researchers uti­lized gra­di­ents of ele­va­tion in moun­tains both above and below the alpine tree line. Ele­va­tion serves as a sur­ro­gate for cli­mate warm­ing, because as a con­se­quence of warm­ing, any par­tic­u­lar ele­va­tion is expected to expe­ri­ence the same tem­per­a­ture as that of an ele­va­tion that is 300 meters lower in 80 years time. This approach allows pre­dic­tion of effects of warm­ing in real moun­tain ecosys­tems with­out the prob­lems that plague exper­i­ments. Fur­ther, to test for the gen­er­al­ity of their find­ings, they used ele­va­tional gra­di­ents in seven dis­tinct tem­per­ate regions of the world: cen­tral Europe, Hokkaido, east­ern Aus­tralia, New Zealand, Col­orado, British Colum­bia and Patagonia.

The results
They found recur­rent responses of ecosys­tem prop­er­ties to ele­va­tion across the seven regions. As such, they found that decreas­ing ele­va­tion con­sis­tently increased the avail­abil­ity of nitro­gen from the soil for plant growth, mean­ing that warm­ing will be expected to con­sis­tently improve plant nitro­gen nutri­tion. How­ever, plant phos­pho­rus avail­abil­ity was not con­trolled by ele­va­tion in the same way; as a result the bal­ance of nitro­gen to phos­pho­rus avail­abil­ity (char­ac­ter­ized by the ratios of nitro­gen to phos­pho­rus in plant leaves) was very sim­i­lar across the seven regions at high ele­va­tions, but diverged greatly across the regions at low ele­va­tion. This means that this bal­ance is con­strained by low tem­per­a­tures at high ele­va­tions, but at low ele­va­tions and as tem­per­a­tures become warmer, regional fac­tors and dif­fer­ences between regions become more important.

The researchers fur­ther explored the mech­a­nisms that under­pinned the con­sis­tent responses to ele­va­tion across the seven regions. They found that increas­ing tem­per­a­ture and its con­se­quences for plant nutri­tion were also linked to changes with decreas­ing ele­va­tion in the amount of organic mat­ter in the soil, the qual­ity of this organic mat­ter, and the micro­bial com­mu­nity. These find­ings reveal some remark­ably com­pa­ra­ble responses to increas­ing tem­per­a­ture across glob­ally con­trast­ing regions. Fur­ther, they found that these changes are at least partly inde­pen­dent of any effect of the alpine tree line, mean­ing that effects of warm­ing on ecosys­tem prop­er­ties will occur irre­spec­tive of what­ever shifts occur in the migra­tion of trees up-​slope due to higher temperatures.

Much remains unknown about how human-​driven cli­mate change will affect the Earth’s ecosys­tems in the long term and over large spa­tial scales. Through a sim­ple use of a nat­ural exper­i­ment (i.e., ele­va­tional gra­di­ents dis­trib­uted around the world) the researchers were able to pro­vide evi­dence that tem­per­a­ture changes of the mag­ni­tude expected to occur over the next 80 years have the poten­tial to greatly dis­rupt the func­tional prop­er­ties of the Earth’s moun­tain ecosys­tems and result in increased dis­e­qui­lib­rium in both the above– and below-​ground ecosys­tem components.

(Source: Sveriges lant­bruk­suni­ver­sitet press release, 26.01.2017)

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Tiger range countries map

Tiger map” (CC BY 2.5) by Sander­son et al., 2006.


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