沿海濕(shi)地(di)(di)是地(di)(di)球上生(sheng)產力最高(gao)、碳(tan)含量最豐富的生(sheng)態系(xi)(xi)統(tong)之一。海岸(an)濕(shi)地(di)(di)的長期碳(tan)儲量主要(yao)以土(tu)(tu)(tu)(tu)壤(rang)(rang)有(you)(you)機質(zhi)(zhi)（SOM）的形式(shi)存在于地(di)(di)下。除(chu)了作為(wei)碳(tan)匯外(wai)，土(tu)(tu)(tu)(tu)壤(rang)(rang)有(you)(you)機質(zhi)(zhi)還影(ying)響(xiang)濕(shi)地(di)(di)生(sheng)態系(xi)(xi)統(tong)的結構、功能(neng)和(he)穩定性(xing)。為(wei)了預測(ce)和(he)減(jian)輕(qing)氣候(hou)(hou)變(bian)化的影(ying)響(xiang)，有(you)(you)必要(yao)進一步了解環(huan)境因子如何控制(zhi)濕(shi)地(di)(di)土(tu)(tu)(tu)(tu)壤(rang)(rang)有(you)(you)機質(zhi)(zhi)的。因此，作者選擇了墨(mo)西哥(ge)灣北岸(an)的跨不(bu)同(tong)氣溫帶和(he)降雨梯度的10個河口(kou)濕(shi)地(di)(di)進行調查，收(shou)集(ji)了10個河口(kou)濕(shi)地(di)(di)不(bu)同(tong)海拔和(he)植(zhi)被梯度帶中的植(zhi)物(wu)樣(yang)品和(he)土(tu)(tu)(tu)(tu)壤(rang)(rang)樣(yang)品，綜合分析了四個環(huan)境因素（包(bao)括：氣候(hou)(hou)、植(zhi)物(wu)群落、土(tu)(tu)(tu)(tu)壤(rang)(rang)母質(zhi)(zhi)和(he)地(di)(di)形）對濱海濕(shi)地(di)(di)土(tu)(tu)(tu)(tu)壤(rang)(rang)有(you)(you)機碳(tan)的影(ying)響(xiang)。

土(tu)壤(rang)蘊藏著陸地(di)(di)生(sheng)(sheng)態系(xi)(xi)統(tong)中(zhong)(zhong)最(zui)大(da)的(de)(de)(de)(de)碳庫(ku)，土(tu)壤(rang)中(zhong)(zhong)的(de)(de)(de)(de)碳儲(chu)量高于(yu)(yu)比全(quan)球植物(wu)(wu)和(he)(he)大(da)氣中(zhong)(zhong)碳庫(ku)之和(he)(he)。作為(wei)典型的(de)(de)(de)(de)濱海(hai)濕地(di)(di)生(sheng)(sheng)態系(xi)(xi)統(tong)，紅樹(shu)林和(he)(he)鹽沼生(sheng)(sheng)存(cun)(cun)著具有高生(sheng)(sheng)產(chan)力的(de)(de)(de)(de)維管植物(wu)(wu)群落(luo)，這些植物(wu)(wu)產(chan)生(sheng)(sheng)的(de)(de)(de)(de)大(da)量有機物(wu)(wu)由于(yu)(yu)存(cun)(cun)在限制分解的(de)(de)(de)(de)非(fei)生(sheng)(sheng)物(wu)(wu)條件而以土(tu)壤(rang)有機質(zhi)的(de)(de)(de)(de)形式積聚在地(di)(di)下。另外，由于(yu)(yu)海(hai)平面上(shang)升導致的(de)(de)(de)(de)濱海(hai)濕地(di)(di)沉(chen)積物(wu)(wu)和(he)(he)有機質(zhi)加速積累(lei)，為(wei)土(tu)壤(rang)有機質(zhi)的(de)(de)(de)(de)累(lei)積和(he)(he)埋(mai)藏提(ti)供了連續(xu)不斷的(de)(de)(de)(de)容納空間(jian)。因此，濱海(hai)濕地(di)(di)生(sheng)(sheng)態系(xi)(xi)統(tong)地(di)(di)下碳儲(chu)存(cun)(cun)和(he)(he)埋(mai)藏率是(shi)地(di)(di)球上(shang)眾(zhong)多(duo)生(sheng)(sheng)態系(xi)(xi)統(tong)中(zhong)(zhong)最(zui)高的(de)(de)(de)(de)。

了解氣候(hou)變化(hua)對土壤有(you)機(ji)質的(de)影響在(zai)(zai)某些生(sheng)(sheng)(sheng)態(tai)(tai)系(xi)統(tong)(tong)(tong)中尤為重(zhong)要(yao)，例如(ru)在(zai)(zai)濱海濕(shi)(shi)地等生(sheng)(sheng)(sheng)態(tai)(tai)系(xi)統(tong)(tong)(tong)中，相對較小的(de)氣候(hou)變化(hua)就(jiu)可能(neng)(neng)導致生(sheng)(sheng)(sheng)態(tai)(tai)系(xi)統(tong)(tong)(tong)喪失或在(zai)(zai)大景觀尺度(du)上(shang)引發生(sheng)(sheng)(sheng)態(tai)(tai)系(xi)統(tong)(tong)(tong)結(jie)構和功能(neng)(neng)的(de)變化(hua)。在(zai)(zai)濱海濕(shi)(shi)地中，基(ji)礎植(zhi)(zhi)(zhi)物(wu)種(zhong)類扮(ban)演(yan)著(zhu)重(zhong)要(yao)的(de)功能(neng)(neng)性角(jiao)色(se)，如(ru)紅樹(shu)植(zhi)(zhi)(zhi)物(wu)、鹽沼植(zhi)(zhi)(zhi)物(wu)創造了生(sheng)(sheng)(sheng)境，調節(jie)生(sheng)(sheng)(sheng)態(tai)(tai)系(xi)統(tong)(tong)(tong)功能(neng)(neng)，支持著(zhu)整個生(sheng)(sheng)(sheng)態(tai)(tai)系(xi)統(tong)(tong)(tong)群落；這些物(wu)種(zhong)同樣也提供了整個生(sheng)(sheng)(sheng)態(tai)(tai)系(xi)統(tong)(tong)(tong)的(de)產品和服(fu)務。在(zai)(zai)面(mian)臨(lin)海平面(mian)上(shang)升(sheng)的(de)情況時(shi)，基(ji)礎植(zhi)(zhi)(zhi)物(wu)物(wu)種(zhong)通過淹沒、植(zhi)(zhi)(zhi)物(wu)生(sheng)(sheng)(sheng)長(chang)、土壤有(you)機(ji)質積(ji)累(lei)和沉(chen)積(ji)之(zhi)間的(de)生(sheng)(sheng)(sheng)物(wu)地形學反饋，維持著(zhu)濱海濕(shi)(shi)地的(de)穩定。然而濱海濕(shi)(shi)地基(ji)礎植(zhi)(zhi)(zhi)物(wu)在(zai)(zai)面(mian)臨(lin)氣候(hou)變化(hua)引起的(de)生(sheng)(sheng)(sheng)態(tai)(tai)系(xi)統(tong)(tong)(tong)變遷時(shi)也具有(you)脆(cui)弱性。

近年(nian)(nian)來，雖(sui)然(ran)(ran)作者(zhe)對(dui)(dui)氣(qi)候控制濱(bin)海(hai)濕(shi)(shi)(shi)地(di)植(zhi)(zhi)物(wu)群落和(he)(he)地(di)上生態(tai)系(xi)統(tong)(tong)屬(shu)性(xing)(xing)的(de)(de)認識(shi)迅速提(ti)(ti)高，但氣(qi)候因子對(dui)(dui)土(tu)(tu)壤(rang)和(he)(he)地(di)下生態(tai)系(xi)統(tong)(tong)屬(shu)性(xing)(xing)的(de)(de)影(ying)(ying)響(xiang)還有(you)(you)待(dai)進一(yi)步研究。在圖(tu)1中，作者(zhe)闡(chan)明了(le)氣(qi)候對(dui)(dui)墨(mo)西哥灣北部沿(yan)(yan)海(hai)濕(shi)(shi)(shi)地(di)植(zhi)(zhi)物(wu)群落的(de)(de)影(ying)(ying)響(xiang)，然(ran)(ran)而(er)對(dui)(dui)土(tu)(tu)壤(rang)性(xing)(xing)質的(de)(de)相應影(ying)(ying)響(xiang)尚(shang)未完全了(le)解(jie)（作者(zhe)在圖(tu)中用 ？表(biao)示(shi)）。在圖(tu)2中，作者(zhe)提(ti)(ti)出了(le)陸地(di)和(he)(he)海(hai)岸濕(shi)(shi)(shi)地(di)文(wen)獻(xian)中關(guan)于(yu)氣(qi)候對(dui)(dui)碳(tan)(tan)(tan)(tan)相關(guan)土(tu)(tu)壤(rang)性(xing)(xing)質影(ying)(ying)響(xiang)的(de)(de)假設。在陸地(di)生態(tai)系(xi)統(tong)(tong)中，年(nian)(nian)平均降(jiang)水量與土(tu)(tu)壤(rang)有(you)(you)機碳(tan)(tan)(tan)(tan)呈正(zheng)相關(guan)，年(nian)(nian)平均氣(qi)溫與土(tu)(tu)壤(rang)有(you)(you)機碳(tan)(tan)(tan)(tan)呈負相關(guan)。然(ran)(ran)而(er)，在濱(bin)海(hai)濕(shi)(shi)(shi)地(di)，關(guan)于(yu)氣(qi)候驅(qu)(qu)動因素對(dui)(dui)碳(tan)(tan)(tan)(tan)相關(guan)土(tu)(tu)壤(rang)特性(xing)(xing)的(de)(de)影(ying)(ying)響(xiang)，有(you)(you)幾種不同(tong)的(de)(de)假設（參(can)見圖(tu)2中的(de)(de)標題和(he)(he)虛(xu)線(xian)）。基于(yu)文(wen)獻(xian)資料的(de)(de)分(fen)析表(biao)明，溫度(du)與濱(bin)海(hai)濕(shi)(shi)(shi)地(di)土(tu)(tu)壤(rang)碳(tan)(tan)(tan)(tan)密度(du)或土(tu)(tu)壤(rang)碳(tan)(tan)(tan)(tan)積(ji)累之間可(ke)能(neng)沒有(you)(you)關(guan)系(xi)（圖(tu)2，右圖(tu)中的(de)(de)直線(xian)、虛(xu)線(xian)），降(jiang)水量與濱(bin)海(hai)濕(shi)(shi)(shi)地(di)地(di)下碳(tan)(tan)(tan)(tan)儲量之間可(ke)能(neng)存(cun)在正(zheng)相關(guan)。然(ran)(ran)而(er)，跨區域氣(qi)候梯度(du)下系(xi)統(tong)(tong)性(xing)(xing)和(he)(he)戰略性(xing)(xing)的(de)(de)實(shi)測數據的(de)(de)缺(que)乏，阻礙了(le)作者(zhe)對(dui)(dui)這(zhe)些(xie)假設的(de)(de)驗證(zheng)和(he)(he)進一(yi)步了(le)解(jie)氣(qi)候驅(qu)(qu)動因素對(dui)(dui)沿(yan)(yan)海(hai)濕(shi)(shi)(shi)地(di)土(tu)(tu)壤(rang)碳(tan)(tan)(tan)(tan)儲存(cun)和(he)(he)循環(huan)的(de)(de)影(ying)(ying)響(xiang)。

基于文獻的(de)分(fen)析，作者提出如下假設：1. 在研究區溫(wen)度(du)對濱海(hai)濕地土壤有機碳(tan)的(de)影(ying)響很小或無(wu)顯著(zhu)影(ying)響；2. 降(jiang)雨量(liang)、鹽度(du)和植(zhi)物生(sheng)產力對土壤有機碳(tan)具有顯著(zhu)的(de)直接(jie)或間接(jie)影(ying)響；3. 由于地貌影(ying)響著(zhu)淹沒(mei)、沉(chen)積物供(gong)應和鹽度(du)分(fen)布(bu)，而他(ta)們同樣(yang)都影(ying)響植(zhi)物生(sheng)產力，所以(yi)作者假設高程能夠顯著(zhu)影(ying)響土壤有機碳(tan)含量(liang)。?

作者首先建立了一個濱海濕地通用模型，該模型是基于1941年Jenny創建模型的改進，并在前人模型的基礎上加入了如鹽分等影響濱海濕地的重要參數（圖3）。同時，作者對圖4中墨西哥灣北部的10個河口濕地中植被、土壤相關參數進行了取樣調查和測量。