山地草原生物量的垂直变化及其与气候变暖和施肥的关系

BIOMASS RESPONSES TO A SIMULATED GLOBAL WARMING BY CHANGING OF ELEVATION AND FERTILIZER ADDITION IN UPLAND GRASSLAND

试验将３种土壤（酸性棕壤、灰壤土、粘泥炭土）／植被的土柱从位于英格兰北部的ＧｒｅａｔＤｕｎＦｅｌ（ＧＤＦ）移入同一山体低海拔的ＮｅｗｔｏｎＲｉｇｇ（ＮＲ），利用海拔高差造成的温差（４．２℃）模拟全球变暖对生物量的影响；和利用施肥（２０ｋｇＮｈｍ－２ａ－１、１０ｋｇＰｈｍ－２ａ－１）试验模拟全球变暖下，温度升高诱发土壤有机质分解速度加快，营养元素浓度升高对生物量的影响。结果表明：海拔变动造成的温度差异使生物量差异极显著（Ｐ≤０．０１）。温度升高使粘泥炭土、酸性棕壤、灰壤土地上总生物量比对照分别提高５１％、７８％及６６％；同时，物种组成大大改变，剪股颖在群落总生物量中所占的比例急剧升高。但不同施肥处理未使样品间生物量出现显著差异，从而得出结论：全球变暖引起的土壤有机质分解速度加快不会直接对生物量造成重要影响；而温度是影响生物量及物种组成变化的主要因素。

Experiments were carried out to test the impacts of improved climate on biomass in three upland grassland systems .This was achieved by transplanting lysimeters of different soil/vegctation types between two sites down an altitudinal gradient at Great Dun Fell(GDF) in the northern Pennines,U.K.Three soil types were moved(acid brown earth,peaty gley and micropodzol) with associated vegetation,and the temperature difference between the sites was an annual average of 42℃Parallel fertilizer experiments were performed using the three soil/vegetation types at the same two sites, to examine the vegetation responses to additions of N (20kg·hm-2·a-1) and P (10kg·hm-2·a-1) in order to assess whether climaticallylinked improvements in growth were related to soil nutritional changes. The experiment showed that the change in altitude resulted in a marked and significant(p<001) increase in total aboveground productivity,with productivity at the warmer site being increased by 51%,66% and 78% for the peaty gley,micropodzol and acid brown earth,respectively.Change in species composition were observed with, in particular ,the grass Agrostis capillaris showing the greatest positive response to climatic improvement.The fertilizer additions did not show any significant effect on above ground productivity on any soil type,at either of the two transplant sites, Therefore, we conclude that temperature acting on the plants directly, and not through soil nutrient supply,is the major limiting factor to primary productivity at this upland site.