白洋淀水陆交错带对陆源营养物质的截留作用初步研究

在白洋淀进行的野外实验结果表明水陆交错带中的芦苇群落和群落间的小沟都能有效地截留来自府河的陆源营养物质,其中,在植被２９０ｍ长的小沟对地表径流总Ｎ和总Ｐ的截留分别为４２和６５％;４ｍ芦苇根区土壤对地表下径流总Ｎ和总Ｐ的截留率分别为６４和９２％。被截留比率最大的是无机态的正磷酸根态磷和铵态氮。     

漓江水陆交错带不同植被类型的土壤酶活性

水陆交错带是内陆水生生态系统与陆地生态系统之间的功能界面区,其包含了高地到低地直到水体的区域,是土壤有机质源、汇和转换器。土壤中有机物的分解以及营养物质的转化不仅影响到植物的生长,也对水体质量产生间接影响。土壤酶几乎参与土壤中有机物质的分解与合成的全过程,直接或间接影响着土壤一系列的生物化学反应,对生态系统的物质循环产生重要影响。不少学者围绕农田土壤、林地土壤以及湿地土壤探讨了不同植被下酶活性的变异。水陆交错带植被种类丰富,周期性的淹水条件加剧了土壤性质变异的复杂性。但目前水陆交错带不同植被类型土壤酶活性差异的研究不多。以漓江水陆交错带土壤为研究对象,对苔藓、草本和灌丛3种植被类型下的土壤溶解性化学成分、4种土壤水解酶即糖苷酶、几丁质酶、亮氨酸氨基肽酶和磷酸酶以及2种氧化还原酶即酚氧化酶和过氧化物酶的活性,以及土壤性质与酶活性之间的关系进行了研究。结果表明,苔藓植被下土壤的糖苷酶和酚氧化酶活性显著高于草本和灌丛,草本植被下土壤的过氧化物酶活性显著高于苔藓和灌丛,灌丛植被下土壤几丁质酶活性显著高于苔藓和草本,但不同植被类型的土壤亮氨酸氨基肽酶活性无显著差异。相关分析表明,土壤水分含量与糖苷酶和酚氧化酶活性呈显著正相关,而与几丁质酶和碱性磷酸酶活性呈显著负相关。土壤有机碳和易氧化碳均与糖苷酶和酚氧化酶活性呈极显著负相关,与几丁质酶活性呈显著正相关。土壤溶解性有机碳与亮氨酸氨基肽酶和酚氧化酶呈显著正相关。综合认为,水陆交错带不同种类土壤酶在不同植被类型间的差异有别,土壤水分含量和土壤有机碳显著影响土壤酶活性的变化。不同植被类型土壤酶活性的差异不仅与植被类型有关,与水陆交错带微地形以及土壤性质的空间异质性也有密切关系,需运用长期控制试验手段开展研究。     

漓江水陆交错带土壤理化性质及其分布特征

水陆交错带是水生生态系统与陆地生态系统之间的过渡带,是一种典型的生态交错区,承载着能量流动、物质循环和信息交换的重要作用。土壤作为水陆交错带系统的重要组成部分,是水陆交错带功能实现的基础之一。鉴于此,以桂林漓江水陆交错带纵向梯度(上游、中游、下游)不同植被覆盖条件下的土壤为研究对象,采用野外取样调查、实验分析与统计检验相结合,系统的分析了土壤理化性质及其分布特征,旨在为该区域退化生态系统恢复与重建提供依据。结果表明:11个土壤理化性质,其中5个指标(土壤含水量、全氮、全磷、速效氮和速效钾)在上游、中游和下游均差异性显著。不同梯度下的土壤理化性质的相关性及相关性大小也不尽相同,但在总体上存在一些较相似的变化规律,如上游、中游和下游的土壤容重和孔隙度均呈现显著负相关,土壤全磷和有机质与多数土壤化学性质呈显著正相关;土壤含水量在下游与多数土壤化学性质均显著相关,但在上游仅与土壤全磷显著负相关。PCA主成分分析表明,土壤容重、土壤孔隙度和土壤全磷含量的贡献均大于其他环境因子的平均贡献率,体现了它们是影响漓江水陆交错带土壤理化性质的重要环境因子。     

漓江水陆交错带不同淹没区植物多样性与土壤特征

针对旅游区水陆交错带出现植被退化、砾石裸露导致景观观赏度降低的问题,以广西桂林市大圩古镇水陆交错带为研究区域,按照水陆交错带淹没程度将其划分不同淹没区,并在详细调查基础上研究了各淹没区植被指标与土壤理化特征分布特征。结果表明:研究区内水陆交错带物种组成以一年生草本植物为主,物种多样性在各个不同淹没区基本呈现为先增后减的趋势,具体为轻度淹没区中度淹没区重度淹没区微度淹没区;随着水文作用的减弱,土壤砂粒含量呈现逐渐减小的趋势,粉粒和黏粒含量呈现逐渐增加趋势,土壤容重、土壤有机质含量和土壤全磷含量呈现先减后增的趋势;全氮含量呈现先增后减趋势,全钾含量在各淹没区差异不明显;研究表明大圩古镇水陆交错带土壤理化性质与植被多样性强烈地受以水位为主导的水文过程的影响与控制。扁蓄可以作为一种指示水淹时间的物种;此外,大圩古镇水陆交错带除受水文作用影响较大外,高强度旅游干扰也是重要的因素之一,植被恢复工作应兼顾生态和旅游,提升大圩古镇景观游憩度。     

漓江水陆交错带典型立地根系分布与土壤性质的关系

研究根系与土壤关系是发掘河岸带生态退化等问题内在原因的重要途径。在漓江流域水陆交错带选取缓坡、陡坡、江心洲、人工岸坡4种典型立地类型,对不同土层深度的根长密度、根系生物量、比根长,以及根系特征与土壤有机质、全氮、有效磷的关系进行了研究,旨在为漓江流域生态修复过程中植被恢复、植被配置、快速绿化材料选取提供科学依据。结果表明:(1)同一立地类型0—10 cm土层和10—20 cm土层比根长差异性不显著。0—10 cm到10—20 cm土层,各立地类型根长密度和根系生物量密度均减小,但不同立地类型根长密度和根系生物量密度的差异程度逐渐缩小,表明地形、地表植物类型及生长状况对根长密度分布的影响也随土层深度的增加而逐渐减小。细根根长和生物量随着土壤深度的增加而减小。(2)土壤有机质含量差异性显著,分布规律为人工岸坡陡坡江心洲缓坡;土壤全氮含量从大到小依次是人工岸坡、陡坡、缓坡、江心洲,其值分别为:3.12、2.33、1.56、1.32 g/kg;土壤全氮与土壤有机质呈显著正相关。江心洲和缓坡有效磷含量远远大于人工岸坡和陡坡,原因是漓江水长期受人为洗漱影响,导致受江水干扰大的立地类型有效磷含量高。(3)根长密度、比根长、根系生物量与有机质、全氮含量呈正相关,与有效磷含量呈负相关,说明土壤根系越丰富,越有利于增加土壤有机质和全氮含量,但遏制了土壤有效磷。细根长度、生物量与根长密度在0.01水平(双侧)上显著正相关,与根系生物量密度呈负相关。     

漓江水陆交错带典型灌木群落根系分布与土壤养分的关系

在漓江流域水陆交错带选取一叶萩、细叶水团花、枫杨3种典型灌木群落,对不同土层深度的根长密度,以及根长密度与土壤有机质、全氮、有效磷的相关关系进行了研究,旨在为漓江流域生态修复过程中灌木植被恢复、主要灌木植被配置、快速绿化材料选取等提供科学依据。结果表明:(1)漓江水陆交错带典型灌木群落各土层根长密度差异性显著,分布规律均为:枫杨细叶水团花一叶萩。0—10 cm到40—60 cm土层,各灌木群落根长密度均减小,但不同灌木群落根长密度的差异程度逐渐缩小,表明地形、地表植物类型及生长状况对根长密度分布的影响也随土层深度的增加而逐渐减小。(2)枫杨(25.10g/kg)灌木群落底层腐殖质层厚,有机质含量最高,分别是细叶水团花、一叶萩的1.24、1.87倍。各灌木群落全氮含量从大到小依次是枫杨、细叶水团花、一叶萩,其值分别为:3.23、2.41、1.46 g/kg。土壤有效磷分布规律为一叶萩(11.56 mg/kg)细叶水团花(5.37 mg/kg)枫杨(3.99 mg/kg);一叶萩灌木群落有效磷含量远远大于枫杨和细叶水团花,原因是漓江水长期受人为洗漱影响,导致受江水干扰大的一叶萩灌木群落有效磷含量高。(3)根长密度与有机质、全氮含量呈正相关,与有效磷含量呈负相关,说明适量增加土壤有机质、全氮含量,减少土壤有效磷,有利于土壤根系的生长。根长密度与0L≤1 mm径级的根系所占比例呈极显著正相关,与1L≤2 mm径级的根系所占比例呈显著正相关,表明根系细根越多,根长密度越大。     

基于人地关系视角的鄱阳湖水陆交错带范围划分

水陆交错带是典型的过渡性地理空间,是地理学研究的关键样带,承载着特殊且复杂的人地关系。根据鄱阳湖过水性、吞吐型、季节性特点,考虑行政区划完整性与尺度效应,基于高分辨率遥感影像和长时间序列水位变化数据,利用非监督分类、目视解译、调查验证等方法,从自然和行政区划两个维度划分了鄱阳湖水陆交错带的地域范围,阐述了其自然、经济和社会等基本特征,分析了其理论基础、现实意义及科学内涵。研究表明：(1)鄱阳湖水陆交错带最大自然范围约为2508.08 km~2,行政范围涉及11个县(市、区)78个乡镇单元,包含行政村974个;(2)其景观要素变化多样,经济发展主要以生态农业、生态旅游业为主,人口分布呈现带状特征,与交错带范围高度吻合;(3)自然基础、尺度效应和内涵特征是其范围划分的理论基础,探究其人与环境相互作用的过程、机理与规律是重要现实意义;(4)未来可以从景观格局变化、人地关系分解、社会生活变迁等方面开展进一步研究,以揭示该区域特殊人地关系变化。     

漓江水陆交错带植物叶性状对水淹胁迫的响应及经济谱分析

以漓江水陆交错带为研究区,分两个条带分别量测了适生植物的5个叶性状指标:最大净光合速率(A_(max))、比叶重(LMA)、单位质量叶片全氮含量(N_(mass))、单位质量叶片全磷含量(P_(mass))、单位质量叶片全钾含量(K_(mass))。研究重度淹没带与微度淹没带不同功能型植物叶性状间的差异,分析并讨论重度淹没带叶性状间的关系与全球尺度是否存在差异,探究重度淹没带植物对水淹生境的生理响应机制。结果如下:(1)重度淹没带植物叶片的A_(mass)、N_(mass)、P_(mass)显著高于微度淹没带。(2)乔木、灌木叶片的LMA均显著高于草本植物,而A_(mass)、PPUE均显著低于草本植物。(3)重度淹没带草本叶性状指标的N_(mass)、P_(mass)、PNUE均显著高于微度微度淹没带,而乔木、灌木的叶性状在两个条带的差异则不显著。(4)重度淹没带植物叶性状关系与全球尺度基本一致,其植物叶片具有低LMA,高A_(mass)、Nmas s、P_(mass)。分析可知,重度淹没带植物在出露期提高叶片光合效率及相关营养水平可能是其适应水淹胁迫特殊生境的关键策略之一;不同功能型植物对同一环境的适应能力存在一定的差异,草本对于水淹环境的响应更为积极,适应能力更好;重度淹没带也存在叶经济谱,其植物在经济谱中属于"快速投资-收益"型物种。     

氮沉降对森林土壤磷循环的影响

磷是生物体必需的大量元素之一,也是许多生态系统的主要限制因子。近年来,大气氮沉降日益加剧,已对森林生态系统磷循环产生了不可忽视的影响。关于氮沉降对生态系统磷循环的影响已开展了一系列的研究,然而尚缺少对其整体的认识。因此,通过收集国内外已发表的相关文章,从以下五个方面综述氮沉降对森林生态系统土壤磷循环的影响及其机理:1)阐述了森林生态系统土壤磷循环的概念;2)介绍了氮沉降对森林土壤磷循环影响的研究方法,包括长期定位模拟氮沉降法、自然氮沉降梯度法和同位素示踪法等;3)概述了氮沉降对森林生态系统土壤磷循环的影响。目前的研究结论趋向于认为长期氮沉降使森林土壤磷循环速率加快。长期氮输入易于使土壤中可溶性磷向非活性磷酸盐库迁移而难以被利用。因此,为了满足需求,土壤磷酸酶活性将增加以加速有机磷的矿化,从而加速磷素在土壤-植物-微生物之间的周转。4)探讨了氮沉降影响森林土壤磷循环的机制。氮沉降可通过改变土壤有机质的性质、微生物群落组成、磷酸酶活性以及阳离子的流动性等途径影响森林土壤磷循环;5)指出了当前研究存在的问题及未来的研究方向。     

北方农牧交错带温性盐碱化草地土壤呼吸对不同形态氮添加和刈割的响应

农牧交错带草地生态系统兼受农业和牧业的影响, 属于脆弱生态系统, 尤其是养分贫瘠的盐碱化草地, 其生态系统结构和功能对外界干扰的响应更加强烈。位于晋西北地区的农牧交错带盐碱化草地, 地理位置独特, 区别于天然牧区草地生态系统。由于毗邻农田, 农业氮肥的过量使用促进了活性氮气体排放, 同时使得农牧交错带草地土壤碳氮循环发生改变。刈割是北方农牧交错草地生态系统的主要管理方式, 为了深入探究氮添加和刈割管理方式对农牧交错带草地碳循环的影响, 进一步厘清该区域草地生态系统的碳动态问题, 该研究设置了一个不同形态氮添加和刈割的裂区实验, 测定土壤呼吸对不同形态氮肥添加和刈割的响应, 为进一步科学管理该区域草地提供可靠的依据。实验样地位于山西省右玉县境内的“山西农业大学农牧交错带草地生态系统野外观测研究站”, 于2017年设置不同形态氮添加和刈割处理, 实验处理包括对照(不刈割和刈割)、尿素添加、缓释尿素添加、刈割+尿素添加、刈割+缓释尿素添加, 每种处理6个重复, 共36个小区。在不同处理条件下测定土壤呼吸速率、土壤温度、土壤水分、土壤微生物生物量、土壤无机氮含量、植物地上和地下生物量, 并计算土壤累积碳排放量及CO₂通量。研究结果表明: (1)短期(2017-2018年)尿素和缓释尿素的添加显著提高了该地区土壤呼吸速率和土壤累积碳排放量。与添加缓释尿素相比, 添加尿素处理下的土壤呼吸速率和累积碳排放量更高; (2)刈割显著降低土壤呼吸速率和累积碳排放量; (3)短期氮添加和刈割的交互作用对土壤呼吸速率没有显著影响。因此, 短期氮添加促进了北方农牧交错带盐碱化草地土壤碳释放, 刈割抑制土壤呼吸, 降低了累积碳排放量, 这可能是由于刈割移除地上植物, 减少了凋落物的输入, 底物减少导致土壤微生物活性降低。但是随着处理时间的延长, 氮添加和刈割对该农牧交错带盐碱化草地土壤碳动态的影响还有待进一步探究和发现。     

Basin-Wide Considerations for Water Quality Management: Importance of Phosphorus Retention by Reservoirs

The relationship between phosphorus retention (R_P) and water residence time (R_T) was assessed for selected U.S. Army Corps of Engineers reservoirs and found to be influenced by areal phosphorus loading rate (P_L). For reservoirs with high P_L (>15 gm/m²/yr), R_P increased markedly with modest increases in R_T. Reservoirs with lower values of P_L exhibited less dramatic responses in R_P to changes in R_T. The water quality management implications of this are great since reservoirs for which marked changes in R_P can occur with modest changes in R_T are potential management loci within a drainage basin.     

Soil Phosphorus Fractions and Symbiotic Nitrogen Fixation across a Substrate-Age Gradient in Hawaii

We evaluated soil phosphorus (P) fractions, other soil characteristics, and rates of symbiotic N₂ fixation across a substrate-age gradient in Hawaii that was dominated by the leguminous tree Acacia koa (koa). Patterns of soil P observed on this gradient were compared to those on a slightly wetter gradient dominated by the nonfixer Metrosideros polymorpha (ohia). Along both gradients, concentrations of primary-mineral P fell sharply between the young and intermediate-aged sites, while labile inorganic P declined most steeply between the intermediate-aged and old sites. The most marked difference between the two gradients was that total soil carbon (C), nitrogen (N), and P, as well as nonoccluded organic P, were more variable across the ohia gradient, increasing to the intermediate-aged sites, then declining sharply at the old site. On the koa gradient, specific nitrogenase activity, measured by the acetylene-reduction (AR) assay, decreased three- to eightfold between the young site and the intermediate-aged and old sites, respectively. Nodule biomass showed no clear pattern. N₂ fixation rates, estimated by combining AR activity and nodule biomass measurements, were up to 8 kg N · ha⁻¹ · y⁻¹ at the young site and no more than 2 kg N · ha⁻¹ · y⁻¹ at the older sites, suggesting that koa may be a modest source of N in these Hawaiian forests. Received 26 September 2000; accepted 15 February 2002     

Nitrogen Addition Shapes Soil Phosphorus Availability in Two Reforested Tropical Forests in Southern China

Scant information is available on how soil phosphorus (P) availability responds to atmospheric nitrogen (N) deposition, especially in the tropical zones. This study examined the effect of N addition on soil P availability, and compared this effect between forest sites of contrasting land‐use history. Effects of N addition on soil properties, litterfall production, P release from decomposing litter, and soil P availability were studied in a disturbed (reforested pine forest with previous understory vegetation and litter harvesting) and a rehabilitated (reforested mixed pine/broadleaf forest with no understory vegetation and litter harvesting) tropical forest in southern China. Experimental N‐treatments (above ambient) were the following: Control (no N addition), N50 (50 kg N ha^?1 yr^?1), and N100 (100 kg N ha^?1 yr^?1). Results indicated that N addition significantly decreased soil P availability in the disturbed forest. In the rehabilitated forest, however, soil P availability was significantly increased by N addition. Decreases in soil P availability may be correlated with decreases in rates of P release from decomposing litter in the N‐treated plots, whereas the increase in soil P availability was correlated with an increase in litterfall production. Our results suggest that response of soil P availability to N deposition in the reforested tropical forests in southern China may vary greatly with temporal changes in tree species composition and soil nutrient status, caused by different land‐use practices.     

丘岗稻田地下水位动态及对土壤氮磷有效性的影响

对红壤丘岗区渍潜田地下水位动态变化规律及对土壤氮磷有效性的影响进行了研究。结果表明,渍潜田地下水位的月变化具有十分明显的规律性,一般以秋冬季节（1－3月份和9－12月份）地下水位最低,而以春夏季节（4－8月份）地下水位最高,故以早稻受渍害最为严重,其原因主要是受降雨和灌溉的共同影响。根据渍潜田地下水位的变化特点不同,可将其分为地下水位和相对稳定型和非稳定型两种类型,并提出了相应的水分管理模式,地下水位的变化能明显影响土壤养分的有效性,随着地下水位的升高,土壤有效氮和磷含量下降。渍潜田土Fe-P和O－P含量也有随地下水位的升高而呈下降的趋势,其含量亦显著低于非渍潜田土壤,因而导致了土壤磷素有效性的下降。     

不同杉木林分类型土壤团聚体生态化学计量特征

在野外调查的基础上,选择成土母质相同、坡向坡度相似、海拔基本一致的杉木-米老排、杉木-火力楠和杉木纯林3种杉木人工林采集土壤样品,通过干筛法分离＞2 mm、2～0.25 mm和＜0.25 mm 3个团聚体组分,研究其土壤团聚体有机碳、全氮、全磷的含量及其生态化学计量特征,以阐明不同杉木林分类型土壤团聚体碳氮磷生态化学计...     

Soil Water Retention on Gold Mine Surfaces in the Mojave Desert

An experimental analysis of soil water retention was conducted on three substrates (an abandoned road, an overburden pile, and a heap leach) created by gold mining activities in the Mojave Desert in southeastern California. We mixed each substrate with straw, and the overburden pile and heap leach with growth medium, then applied surface rock mulch to half the plots in an attempt to increase soil water‐holding capacity for revegetation efforts. For each of the six treatments (controls included) we monitored soil water with time domain reflectometry following both a simulation of a rainfall event and a natural rainfall that occurred immediately following the simulation. Both the simulation and the rainfall increased soil water between 3 and 8%, depending on the substrate. Water retention patterns in the two‐week periods following each water addition were similar between the simulation and rainfall, and among all substrate types as values returned to background (pre‐water) conditions. The abandoned road substrate had higher background water content (16.5%) than the overburden pile (6%) and heap leach (5%). The road also had three times higher organic matter and five times higher soil nitrogen than the other two sites. Soil water retention was improved on the overburden pile by the addition of just surface rock mulch or of straw‐plus‐rock mulch. On the heap leach, increases were found with rock mulch only or with growth medium‐plus‐rock mulch. Rock mulches did not improve soil water retention and straw additions decreased soil water on the abandoned road. Judicious use of soil amendments can improve soil water conditions and improve revegetation efforts on disturbed lands in desert environments.     

Bio-Acidification and Leaching of Metals,Nitrogen, and Phosphorus from Soil and Sludge Mixtures

Soil and wastewater treatment sludge are commonly brought together in mixtures for a variety of beneficial purposes. The mixtures contain bioacidifying (i.e., sulfur-oxidizing) microorganisms that can easily be activated through providing the appropriate substrate and environmental conditions. In this study, contaminated soil and sludge mixtures were subjected to controlled bio-acidification and the impacts of the process on the partitioning of heavy metals, nitrogen, and phosphorus were examined. Three successive bio-acidification cycles resulted in significant leaching of metals from sludge. The leaching results, expressed as fraction of total mass of metals in the sludge, averaged 67% for Cr, 96% for Ni, 24% for Zn; 16% for Cu; 23% for Cd; and 96% for Pb. Bio-acidification of the sludge also converted 28 to 45% of the organic nitrogen into ammonia and increased the soluble orthophosphates fraction of total phosphorus by approximately 18 to 20%. Bio-acidification also resulted in significant metals leaching from the contaminated soils in the soil/sludge mixtures. Soil/sludge mixtures were prepared using six soil particle sizes (less than 0.075?mm to 2.38?mm) contaminated with 22,500?mg/kg Zn, 14,000?mg/kg Pb, 1500?mg/kg Cr, 9500?mg/kg Cu, 1000?mg/kg Ni, and 1000?mg/kg Cd. The addition of metals to the soil inhibited the sulfur-oxidizing microorganisms, preventing bio-acidification in the mixtures containing 4 to 50?g soil in 130?ml sludge, and considerably slowing bio-acidification in the mixtures containing 1 to 3?g soil. Using a mixture that contained 2-g soil samples, three successive bio-acidification cycles resulted in significant cumulative metals leaching results. The leaching results, expressed as percentage of the mass of metals added to the soil, were in the range of 56 to 98% for Cr, 77 to 95% for Zn, 33 to 66% for Ni, 64 to 82% for Cu, and 10 to 33% for Pb, with the higher results in each range belonging to the larger size soil particles. On the other hand, only Cr was leached in neutralized soil samples. The results confirmed the potential for inhibition of the sulfur-oxidizing microorganisms and bio-acidification in contaminated soil/sludge mixtures, and the significant impacts of bio-acidification on the mobility of metals, nitrogen, and phosphorus. In addition, the results confirmed the potential for using controlled bioacidification for removing heavy metals from contaminated soil using the indigenous sulfur oxidizing microorganisms in sludge.     

Experiments on Nitrogen and Phosphorus Release by Chironomus ex gr. plumosus from the Sediments of Lake Balaton,Hungary

Sediment-water systems of Lake Balaton mud and tap water were constructed in plexiglass tubes and boxes for evaluation of changes in the nitrogen and phosphorus contents of overlying water as influenced by chironomid density and light conditions. Nitrogen flux from sediment was greatly influenced by denitrification process. The amount of TN released by chironomids amounted to about half of the yearly nitrogen fixation rate in Lake Balaton. Omnivorous chironomids increased the phosphorus content of the overlying water. The rate of release was density dependent. TP release rates ranged between 1–17 mg m⁻² day ⁻¹ over a range of densities 500–20,000 larvae m⁻². It became evident that aerobic sediment cores can be an important nutrient source in lakes where chironomids inhabit them at densities above 1,000 larvae m⁻².     

The Influence of Land Use on Lake Nutrients Varies with Watershed Transport Capacity

Nutrient loading to lakes depends on both the availability of nutrients in a watershed and their potential for movement to a lake. Many studies have demonstrated that variation in watershed land use can translate to differences in lake water quality by affecting nutrient availability. There have been few attempts, however, to understand how loading to surface waters is affected by land use when there are differences in watershed transport capacity. We compared the relationship between land use/cover and lake nutrients in lakes draining watersheds that exhibited high and low transport capacity using a 5 year (2001–2005) dataset describing the chemistry of 101 lakes and reservoirs in a region of intensive agriculture. We measured watershed transport capacity by compositing the hydrologic, geologic, and topographic variables correlated with interannual variability in lake total nitrogen (TN) or phosphorus (TP) because the hydrologic permeability of watersheds amplifies downstream responses to rainfall events. Factors describing watershed transport capacity differed for TN and TP, consistent with differences in nutrient mobility and biogeochemistry. Partial least squares regression revealed that watershed transport capacity influenced the nature of the association between land use/cover and lake chemistry. In watersheds with low transport capacity, in-lake processes and near-shore land use/cover tended to be more influential, whereas, in watersheds with high transport capacity, land use/cover across the entire watershed was important for explaining lake chemistry. Thus, although land use is a key driver of nutrient loading to lakes, the extent to which it influences water quality can vary with watershed transport capacity. JMF conceived the study and analyzed the data. JAD collected the data. JMF and JAD wrote the paper.